materials Article
Effect of Polymer Matrix on the Structure and Electric Properties of Piezoelectric Lead Zirconatetitanate/Polymer Composites Rui Li 1,2, *, Jun Zhou 1 , Hujun Liu 3 and Jianzhong Pei 1 1 2 3
*
Highway School, Chang’an University, Xi’an 710064, China; [email protected] (J.Z.); [email protected] (J.P.) School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore CCCC Fourth Harbor Engineering Institute Co., LTD., Guangzhou 510000, China; [email protected] Correspondence: [email protected]
Received: 27 June 2017; Accepted: 8 August 2017; Published: 14 August 2017
Abstract: Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 103 Hz, the dielectric and piezoelectric properties of PZT/poly(vinylidene fluoride) were both better than that of PZT/polyvinyl chloride (PVC). When the volume fraction of PZT was 50%, PZT/PVDF prepared by the hot-press method had better comprehensive electric property. Keywords: PZT/polymer; PVDF; PVC; dielectric; piezoelectric
1. Introduction In recent years, the use of piezoelectric materials to collect energy received more and more attention, the environmental characteristics of piezoelectric materials are also gaining popularity [1–4]. As a member of the new functional material family, piezoelectric actuators have been widely used in engineering and daily life because of their good piezoelectric effect, but their inflexibility and brittleness lead to processing difficulties and poor impact resistance, and so their applications are limited [5–7]. In the past, researchers improved the properties of PZT by changing its preparation condition, polarization condition, and the particle size in most cases, but there have been few studies to examine how the polymer affects PZT/PVDF. Compared with the pure PZT piezoelectric materials, PZT/polymer composites have many virtues such as lower density, better flexibility, stronger plasticity, easier performance improvement and so on. Mendes [8] researched the influence of particle size and the amount of PZT fillers on the PVDF matrix of measurement the dielectric and dynamic mechanical of PZT/PVDF, the results showed that the dielectric properties of the composites are mainly affected by the amount of the ceramic particles. As a polymer monomer, poly(vinylidene fluoride) (PVDF) is renowned for having excellent piezoelectric properties, as well as good mechanical and chemical properties, especially a wide processing temperature range to meet the industrial control system field [9–15]. As an engineering polymer, polyvinyl chloride (PVC) is widely used throughout the building materials industry because it has unique advantages such as waterproof, fireproof, and antistatic properties, PVC can be especially easily shaped and costs less than PVDF [16–23]. In this paper, PVDF and PVC were used to prepare PZT/polymer piezoelectric composite with PZT respectively, the microstructure of PZT/polymer composite was observed by scanning electron Materials 2017, 10, 945; doi:10.3390/ma10080945
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micrographs (SEM), the physical phases of the composite were analyzed by X-ray diffractometer (XRD), the effect of two kinds of polymer matrix on the electric properties of PZT/polymer composite materials were investigated. The results measured have great importance to the design of application domain of PZT/polymer composite materials. 2. Experimental 2.1. Materials PZT was supplied by Hongsheng Acoustic, Electronic Equipment Co. Ltd. in Baoding, China. PVDF was supplied by San AI Fu FR902 in Shanghai, China. PVC was from Nanjing Daoning Chemical Co. Ltd. in Nanjing, China. 2.2. Preparation of PZT/Polymer Composites The PZT and PVDF powder were weighed by the volume. Then they were mixed and the mixture was placed into a grinding bowl, next absolute ethyl alcohol was added, the powder was mixed with a stirring rod for 10 min. After the mixture was dried in an oven at 100 ◦ C for 25 min, the mixed powder of PZT and PVDF was put in the hot pressing mold, which was heated to 190 ◦ C for 30 min, PZT/PVDF composites with a diameter of 13 mm and a thickness of 1 mm were obtained. The above steps were repeated to mix the PZT and PVC, the temperature of the hot pressing mold was 175 ◦ C for 30 min, PZT/PVC composites with a diameter of 13 mm and a thickness of 1 mm were obtained. The pan was then dried in an oven and an electrode was coated thereon. It was placed in thermostatic silicone oil and polarized at a polarization voltage of 3 kV/mm and at 80 ◦ C for 30 min. Finally, the samples were tested after resting 24 h. 2.3. Measurements All these measurements were obtained at ambient temperature and pressure. The microstructures of PZT/polymer composites were characterized by XRD, FT-IR, and SEM, the dielectric constant (εr ) and the dielectric loss (tan δ) of PZT/Polymers composites were measured by a precision LCR digital bridge under 1 kHz, and the piezoelectric constant (d33 ) of PZT/Polymer composites were measured by ZJ-3AN-type quasi-static d33 measuring. 3. Results and Discussion 3.1. Structure and Morphology 3.1.1. XRD Figure 1 shows the XRD pattern of PZT/PVDF and PZT/PVC composites. It can be seen that there are no new diffraction peaks of XRD and the diffraction peak of PZT has not changed significantly. It is only because of the different crystallization of the polymer that there are different manifestations in the XRD of composite. PVDF is a semicrystalline polymer whose diffraction peak is weak and is basically covered when the PZT content is 50%. Figure 1b shows that there is no the diffraction peak of PVC caused by the PVC crystallinity is low. with the increase of the PZT content, the (002) diffraction peak becomes gets stronger gradually, that is, with the increase of PZT content and decrease of polymer content, the formation is beneficial to the polarization of the ceramic phase.
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Figure 1. (a) XRD pattern of PZT/PVDF composites; (b) XRD pattern of PZT/PVC composites. Figure 1. (a) XRD pattern of PZT/PVDF composites; (b) XRD pattern of PZT/PVC composites.
Figure 1. (a) XRD pattern of PZT/PVDF composites; (b) XRD pattern of PZT/PVC composites. It is not hard to find that the figure of PZT/PVDF composite is similar to the PZT/PVC, but the It is not hard to find that the figure of PZT/PVDF composite is similar to the PZT/PVC, PZT/PVC is slightly wider, but the polarization rate of the PVDF base composite is higher than that but slightly but the of the PVDF base composite is higher than It isthe notPZT/PVC hard to is find that wider, the figure of polarization PZT/PVDFrate composite is similar to the PZT/PVC, but the of the PVC base composite material at high content. When the content of PVDF is high, the PZT that ofisthe PVC base composite material at high rate content. When the base content of PVDF is high, thethan PZT that PZT/PVC slightly wider, but the polarization of the PVDF composite is higher polarization rate of PZT/PVDF composites is higher than that of PZT/PVC composites [24]. polarization of PZT/PVDF composites higher than that of of the PVC baserate composite material at highis content. When thePZT/PVC content composites of PVDF is[24]. high, the PZT
polarization rate of PZT/PVDF composites is higher than that of PZT/PVC composites [24]. 3.1.2. FT-IR FT-IR 3.1.2. Figure 2a is FT-IR spectra of PVDF powder. It can be seen from the absorption band that the PVDF primarily as α-phase, but exhibited one δabsorption phase absorption band wave primarily existed existed as α-phase, but exhibited only oneonly δ phase band with the with wavethe number −1 number of cm . Itspectra means it is difficult tothe obtain with the piezoelectric effect through −1510 Figure 2a is of PVDF Itβ-PVDF canthe beβ-PVDF seenpiezoelectric from absorption band of 510 cm . ItFT-IR means that it isthat difficult topowder. obtain with effect through the that hot the the hot pressing method. For the piezoelectric composites prepared by hot pressing, PVDF is mainly PVDF primarily existed as α-phase, butcomposites exhibitedprepared only onebyδhot phase absorption with the wave pressing method. For the piezoelectric pressing, PVDF isband mainly α crystal α crystal and does not have the piezoelectric properties. That is, PVDF mainly plays a role of −1 and of does the piezoelectric properties. That is,the PVDF mainly plays a role of connection in number 510not cmhave . It means that it is difficult to obtain β-PVDF with piezoelectric effect through connection in PZT/PVDF composites, and its piezoelectric properties can be neglected. However, due PZT/PVDF andthe its piezoelectric piezoelectric properties canprepared be neglected. However, due to the strong the hot pressingcomposites, method. For composites by hot pressing, PVDF is mainly to the strong polarity of C–F in PVDF, the effect properties of dielectricofproperties of the PZT/PVDF composites polarity of C–F in PVDF, the effect of dielectric the PZT/PVDF composites cannot be of α crystal and does not have the piezoelectric properties. That is, PVDF mainly plays a role cannot be neglected. Figure2b shows that the maximum value of the PVC absorption peak at 1248.82 − neglected. Figure 2b shows that theand maximum value of the PVC absorption peak at 1248.82 cm 1 , due connection in PZT/PVDF composites, itsadjacent piezoelectric properties can be neglected. However, −1, which cm caused by the oscillation of the –C– of the CH 2 functional group in the PVC and caused by the oscillation of the adjacent –C– of the CH2 functional group in the PVC and its to thewhich strong polarity of C–F The in PVDF, theabsorption effect of dielectric properties of the−cm PZT/PVDF composites −1 was formed its connected –Cl– atoms. vibration peak of ethylene at 1429.08 connected –Cl– atoms. The vibration absorption peak of ethylene at 1429.08 cm 1 was formed duedue to cannot be neglected. Figure2b shows that the maximum value of the PVC absorption peak at 1248.82 to shear distortion. shear distortion. Figure 2a is FT-IR spectra of PVDF powder. It can be seen from the absorption band that the PVDF 3.1.2. FT-IR
cm−1, which caused by the oscillation of the adjacent –C– of the CH2 functional group in the PVC and its connected –Cl– atoms. The vibration absorption peak of ethylene at 1429.08 cm−1 was formed due to shear distortion.
Figure (a) FT-IR Figure 2. 2. (a) FT-IR spectra spectra of of PVDF PVDF powders; powders; (b) (b) FT-IR FT-IR spectra spectra of of PVC PVC powders. powders.
3.1.3. 3.1.3. SEM The of PZT/PVC PZT/PVCcomposite compositeprepared prepared PVC with volume fractions of 40%, and The SEM of byby PVC with volume fractions of 40%, 50%50% and 60% 60% respectively were shown in Figure 3. It can befrom seen from 3,of when the volume respectively were2. shown in Figure 3.ofItPVDF can bepowders; seen 3, when the volume fractionfraction of PZT Figure (a) FT-IR spectra (b)Figure FT-IRFigure spectra PVC powders. of PZT was large number PZT particles were ‘suspended’ in the PVDF and PVDF some was 40%, a 40%, large anumber of PZTof particles were ‘suspended’ in the PVDF matrix,matrix, and some powder displays the reunion phenomenon. As the volume PZT increased to 50%, although displays the reunion phenomenon. As the fraction volume of fraction of PZT increased to 50%, 3.1.3.PVDF SEM powder some PZTsome powder completely wrappedwrapped in the PVDF powder, most PZTmost particles were exposed although PZTwas powder was completely in the PVDF powder, PZT particles were The SEM of PZT/PVC composite by PVC with 40%,the 50% and 60% to each other, and the PVDF powderprepared was embedded in the gapvolume betweenfractions particles.of When volume
respectively were shown in Figure 3. It can be seen from Figure 3, when the volume fraction of PZT was 40%, a large number of PZT particles were ‘suspended’ in the PVDF matrix, and some PVDF powder displays the reunion phenomenon. As the volume fraction of PZT increased to 50%, although some PZT powder was completely wrapped in the PVDF powder, most PZT particles were exposed
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exposed to each other, and the PVDF powder was embedded in the gap between particles. When the fractionfraction of PZT PZT increases increases to 60%, 60%,to the PZTthe particles are almost almost completely in contact contact with each each other, volume of PZT increases 60%, PZT particles are almost completely in contact withother, each fraction of to the PZT particles are completely in with and the distribution of PZT particles is very uniform. other, and the distribution PZT particles very uniform. and the distribution of PZTofparticles is veryisuniform. Figure 44 isisthe theSEM SEMimages imagesof ofPZT/PVC PZT/PVC composite prepared by by PVC PVC with with the the volume volume fractions fractions Figure composite prepared the SEM images of PZT/PVC of 40%, 40%, 50% 50% and and 60%, 60%, respectively. respectively.It It can be seen from the Figure 4 that the PZT particles in composite of respectively. can be seen from the Figure 4 that the PZT particles in composite It can materials are are distributed distributed evenly evenly in in the the PVC PVC matrix. matrix. With With the the increase increase of of PZT PZT content, content, the the thickness thickness materials PZT content, thickness of the the PVC PVC layer layer is is reduced reduced and andthe thedistance distancebetween betweenPZT PZTparticles particlesdecreases. decreases. The The interface interface of the PVC layer is reduced and the distance between PZT particles decreases. interface combination between PZT and PVC is better, even the PZT content of PZT/PVC composite is high high combination between PZT and PVC is better, better, even even the the PZT PZTcontent contentof ofPZT/PVC PZT/PVC composite is (PZT:PVC = 60:40), PVC PVC is is still still tightly tightly wrapped wrapped around around the the PZT PZT particles. particles. This This is is due due to to the the PVC PVC (PZT:PVC == 60:40), the PZT particles. having satisfied satisfied bonding bonding performance. performance. The small number number of of having The composites composites have have dense dense matrix and aa small pores, which is mainly caused by the PZT particle extraction process. pores, pores, which which is is mainly mainly caused caused by by the the PZT PZT particle particle extraction extraction process. process.
Figure 3. 3. (a) (a) The The SEM SEM images imagesof ofthe thePZT/PVDF PZT/PVDF (40:60); (40:60); (b) (b) The The SEM SEM images images of of the the PZT/PVDF PZT/PVDF (50:50); (50:50); Figure (40:60); PZT/PVDF PZT/PVDF (c)The TheSEM SEM images of the PZT/PVDF (c) images of the PZT/PVDF (60:40). SEM images of the PZT/PVDF (60:40).
Figure 4. 4. (a) (a) The The SEM SEM images images of the PZT/PVC (40:60); (b) The SEM images ofof the PZT/PVC (50:50); (c) Figure 4. The SEM images of the PZT/PVC (50:50); (c) Figure (a) The SEM imagesof ofthe thePZT/PVC PZT/PVC(40:60); (40:60);(b) (b) The SEM images the PZT/PVC (50:50); The SEM images of the thethe PZT/PVC (60:40). The SEM images of PZT/PVC (60:40). (c) The SEM images of PZT/PVC (60:40).
3.2. Effects Effects of Polymer Polymer on on the the Dielectric Dielectric Properties Properties of of PZT/Polymers PZT/Polymers 3.2. 3.2. Effects of of Polymer on the Dielectric Properties of PZT/Polymers The frequency frequency dependence dependence of of dielectric dielectric constant constant (ε (εrr)) of of PZT/polymers PZT/polymers was was shown shown in in Figure Figure 5. 5. The The frequency dependence of dielectric constant (ε r ) of PZT/polymers was shown in Figure 5. The frequency stability of the PZT/PVDF composites is lower than that of the PZT/PVC composites. The frequency frequency stability stability of of the the PZT/PVDF PZT/PVDF composites lower than than that that of of the the PZT/PVC PZT/PVC composites. The composites is is lower composites. The dielectric dielectric constant constant of of the the PZT/PVDF PZT/PVDF composites composites and and the the PZT/PVC PZT/PVC composites composites has has the same same trend The The dielectric constant of the PZT/PVDF composites and the PZT/PVC compositesthe has the trend same as the change of the PZT volume content. The dielectric constant of PZT/polymer composites as theaschange of the PZTPZT volume content. PZT/polymer composites composites trend the change of the volume content.The Thedielectric dielectricconstant constant of of PZT/polymer increased by by increasing increasing the the addition addition of of PZT, PZT, but but the the extent extent of of the the increase increase was was different. different. increased increased by increasing the addition of PZT, but the extent of the increase was different. The dielectric dielectric properties properties of of PZT/PVDF PZT/PVDF composites composites were higher higher than the the dielectric properties properties of of The The dielectric properties of PZT/PVDF composites were were higher than than the dielectric dielectric properties of PZT/PVC composite with the same PZT contents. This indicates that the dielectric constant of the PZT/PVC composite constant of of the the PZT/PVC composite with with the the same same PZT PZT contents. contents. This This indicates indicates that that the the dielectric dielectric constant PZT/polymer composite composite materials materials is is closely closely related related to to the the polymer polymer matrix’s matrix’s own own permittivity, permittivity, and and PZT/polymer PZT/polymer composite materials is closely related to the polymer matrix’s own permittivity, and the the polymer polymer with with high high dielectric dielectric constant constant can can obtain obtain composite composite material material with with aa high high dielectric the polymer with high dielectric constant can obtain composite material with a high dielectric dielectric constant. constant. When the PZT content of PZT/PVC composite reached 40%, and when PZT/PVDF constant. When the PZT content of PZT/PVC composite reached 40%, and when PZT/PVDF When the PZT content of PZT/PVC composite reached 40%, and when PZT/PVDF composite reaches composite reaches reaches 50%, 50%, the the curve curve shows shows aa strong strong resonance resonance peak, peak, the the reason reason is is that that the the orientation orientation composite 50%, the curve shows a strong resonance peak, the reason is that the orientation polarization comes polarization comes from the dipole of the PZT particles, the larger PZT content, the greater the polarization comes from dipolethe of larger the PZT larger PZT content, thecontribution greater the from the dipole of the PZTthe particles, PZTparticles, content, the the greater the polarization polarization contribution and the more obvious the resonance peak. polarization the more obvious the resonance peak. and the morecontribution obvious the and resonance peak.
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Figure 5. (a) Variation of dielectric constant of PZT/PVDF composites with frequency; (b) Variation of dielectric constant of PZT/PVC composites with frequency. Figure 5. (a) Variation of dielectric constant of PZT/PVDF composites with frequency; (b) Variation of
Figure 5. (a) Variation of dielectric constant losses of PZT/PVDF with (b) Variation Thedielectric relationship between the dielectric (tan δ) composites of two kinds of frequency; PZT/polymer composites is constant of PZT/PVC composites with frequency. of dielectric constant of PZT/PVC composites with frequency. shown in Figure 6. It can be seen that, with the increase of frequency, the tan δ of both composite are relationship between the dielectric (tan δ) of two kindsitofisPZT/polymer compositesof the 4 Hz), slightly The decreasing in the condition of lowlosses frequency (104 Hz), the tan δ of PZT/PVC change range differed greatly 4 Hz), it is due to the relaxation of the are slightly decreasing in the condition of low frequency (10 the tan δ of PZT/PVC change range differed greatly 4 slightly decreasing in theloss condition of low frequency (10 tan of PZT/PVC change range At the same time, the dielectric loss of PVDF matrix composite is higher than that of PZT/PVC frequency the dielectric loss of the PZT/PVDF composites increases dramatically with the frequency increase but the values ofand all PVC tan δ are small. In contrast with the increase of composite. The dielectric loss curves of PVDF composite the At the same time, the dielectric loss of PVDF matrixmatrix composite is higherdisplay than that ofresonance PZT/PVC peak, frequency the dielectric loss of the PZT/PVDF composites dramatically in particular, the PZT content of PZT/PVC hasincreases a composite loss peak when the content is 40%, composite. The dielectric loss curves of PVDFcomposite and PVC matrix display the PZT resonance peak, At the same time, the dielectric loss of PVDF matrix composite is higher than that of PZT/PVC which is mainlythe due to content the relaxation polarization caused dipole PZT. in particular, PZT of PZT/PVC composite has a by lossthe peak whenofthe PZT content is 40%, composite. dielectric curves ofpolarization PVDF and caused PVC matrix display the resonance peak, which isThe mainly due to loss the relaxation by thecomposite dipole of PZT.
in particular, the PZT content of PZT/PVC composite has a loss peak when the PZT content is 40%, which is mainly due to the relaxation polarization caused by the dipole of PZT.
Figure 6. (a) Variation of dielectric loss of PZT/PVDF composites with frequency; (b) Variation of
Figure 6. (a) Variation of dielectric loss of PZT/PVDF composites with frequency; (b) Variation of dielectric loss of PZT/PVC composites with frequency. dielectric loss of PZT/PVC composites with frequency.
3.3. Effects of Polymer on the Piezoelectric Properties of PZT/Polymers
(a) Variation of Piezoelectric dielectric lossProperties of PZT/PVDF composites with frequency; (b) Variation of 3.3. Figure Effects 6. of Polymer on the of PZT/Polymers
As can beofseen in Figure 7, with with the increase of the PVDF volume fraction, the piezoelectric dielectric loss PZT/PVC composites frequency. As can be seen Figure 7, with the increase of the PVDF volume fraction, piezoelectric strain constant (d33in ) and the piezoelectric voltage constant (g33 ) of PZT/PVDF boththe presented decline strain gradually, this is because PVDF mainly played constant a role of a (g connection phase in PZT/PVDF, and PZT constant (d ) and the piezoelectric voltage 33) of PZT/PVDF both presented decline 3.3. Effects of 33 Polymer on the Piezoelectric Properties of PZT/Polymers providedthis the high piezoelectric Therefore, to obtain the piezoelectric properties gradually, is because PVDFperformance. mainly played a role in oforder a connection phase in PZT/PVDF, and PZT As can behigh seenproperties in Figure of 7, the with the increase of the volume fraction, the piezoelectric and mechanical composite system, thePVDF volume fraction of PZT should not bestrain provided the piezoelectric performance. Therefore, in order to obtain thephase piezoelectric properties constant (d3350%. ) and the piezoelectric voltagesystem, constant 33) of PZT/PVDF both presented decline than andless mechanical properties of the composite the(gvolume fraction of PZT phase should not be Figure 7b shows thePVDF relation curve played betweenathe piezoelectric properties of PZT/PVC composite gradually, this is because mainly role of a connection phase in PZT/PVDF, and PZT less than 50%. prepared by PZT and different volume fraction of PZT. As can be seen in Figure 7b, with the increase provided the7b high piezoelectric performance. Therefore, in order to obtain the piezoelectric Figure shows the relation curve between the piezoelectric properties of PZT/PVCproperties composite of the volume fraction of PZT, the d and the g of the composites increase gradually, when 33 33 and mechanical properties of the composite system, the volume fraction of PZT phase but should not be
prepared by PZT and different volume fraction of PZT. As can be seen in Figure 7b, with the increase less than 50%. fraction of PZT, the d33 and the g33 of the composites increase gradually, but when the of the volume Figure 7b shows thePZT relation curvethan between propertiesdecreases of PZT/PVC composite volume fraction of the is more 50%, the the piezoelectric d33 of the composites with a certain prepared by PZT and different volume fraction of PZT. As can be seen in Figure 7b, with the increase amplitude, because when the PZT volume fraction is from 50% to 60%, the PVC particles of the of the volume fraction of PZT, the d33 and the g33 of the composites increase gradually, but when the
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the volume fraction of the PZTais coating more than 50%, thethe d33 ceramic of the composites decreases a certain composite material will form around layer. The resultswith show that the amplitude, because when the PZT volume fraction is from 50% to 60%, the PVC particles piezoelectric properties of the composites show a decreasing trend when the content of of the PZT in composite material will form a coating around the ceramic layer. The results show that the piezoelectric ceramics exceeds 50%. Although the cohesive force between the two phases is increased, the charge properties of the composites show a decreasing trend when the content of PZT in ceramics exceeds transfer ability of the composites is reduced. 50%. Although the cohesive force between the two phases is increased, the charge transfer ability of This is illustrated in the 0–3 composites, the electroactive particles are under-solicited because the composites is reduced. of the difference of dielectric constant betweenthe ceramics and polymers and because of the difference This is illustrated in the 0–3 composites, electroactive particles are under-solicited because of elastic When constant the volume fraction of the is more 60%, thedifference piezoelectric of the modulus difference [25]. of dielectric between ceramics andPZT polymers and than because of the properties of modulus the PZT/PVDF increase with thefraction increase PZT volume are still lower of elastic [25]. When the volume of of thethe PZT is more thanfraction, 60%, thebut piezoelectric of the PZT/PVDF increase with the increase of the PZT volume fraction, but are still lower thanproperties that of PZT/PVC composites. than that of PZT/PVC composites.
Figure 7. (a) Effect of PVDF volume fraction of the d33 of PZT/PVDF; (b) Effect of PVDF volume
Figure 7. (a) Effect of PVDF volume fraction of the d33 of PZT/PVDF; (b) Effect of PVDF volume fraction of the g33 of PZT/PVDF. fraction of the g33 of PZT/PVDF. 4. Conclusions
4. Conclusions (1)
(1)
(2)
(3)
(4)
Two kinds of PZT/polymer composites were prepared by the hot pressing process using two polymers ascomposites the matrix. were The results showby that polymer matrix has ausing great two Twothermoplastic kinds of PZT/polymer prepared thethehot pressing process influence on the piezoelectric and dielectric properties of the PZT/polymer composites. thermoplastic polymers as the matrix. The results show that the polymer matrix has a great (2) The process preparation and of PZT/PVDF from semi-crystalline polymer PVDF was influence on thefor piezoelectric dielectriccomposite properties of the PZT/polymer composites. investigated. The piezoelectric properties of PZT/PVDF are the best when the PZT content is The process for preparation of PZT/PVDF composite from semi-crystalline polymer PVDF was higher than 50%. The dielectric constant of PZT/PVDF composites is better than PZT/PVC, and investigated. The piezoelectric properties of PZT/PVDF are the best when the PZT content is the dielectric loss is slightly higher than that of the PZT/PVC when the frequency is 1 kHz. higher than 50%. The dielectric constant of PZT/PVDF composites is better than PZT/PVC, and (3) The PZT/PVC composites prepared by combining PZT with PVC can measure the resonance the dielectric loss is slightly higher than that of the PZT/PVC when the frequency is 1 kHz. peak of the PZT when the content of PZT was 40%. The g33 of PZT/PVC composites is better than The that PZT/PVC composites prepared with The PVCd can measure the resonance of PZT/PVDF composites whenby thecombining PZT contentPZT is 30–50%. 33 of PZT/PVC composite peakisofobviously the PZTbetter whenthan the content of PZT was 40%. TheTherefore, g33 of PZT/PVC composites is better that of PZT/PVDF composite. the PZT/PVC composites will than that achieve of PZT/PVDF composites when the PZT content is 30–50%. The d33 of PZT/PVC composite high electromechanical coupling coefficients. 3 is obviously better than that of PZT/PVDF composite. Therefore, the PZT/PVC composites (4) Under the condition of frequency is 10 Hz, the dielectric and piezoelectric properties of the will PZT/PVC were both better than PZT/PVDF. When the volume fraction of PZT was 50%, achieve high electromechanical coupling coefficients. 3 the PZT/PVC composites prepared by the hot-press method and couldpiezoelectric achieve excellent electrical Under the condition of frequency is 10 Hz, the dielectric properties of the performance. The εbetter d33 was 16.2When Pc/N,the the volume g33 was 28.26 mV·m/N, andwas the tan δ the r was 65.75, PZT/PVC were both thanthe PZT/PVDF. fraction of PZT 50%, was only 0.037. PZT/PVC composites prepared by the hot-press method could achieve excellent electrical
performance. TheThe εr was 65.75, d33 was by 16.2 the Natural g33 wasScience 28.26 mV·m/N, the tan Acknowledgments: research wasthe supported thePc/N, National Foundationand of China (Grant Nos. 51378073 and 51408048), the Key Program for International Science and Technology Cooperation was only 0.037. Projects of Shaanxi province (Grant Nos. 2014KW10-03 and 2016ZDJC-24), the China Postdoctoral Science Foundation (Grant Nos. 2015M582591 and 2016T90880).
δ
Acknowledgments: The research was supported by the National Natural Science Foundation of China (Grant Author Contributions: Rui Li and Jianzhong Pei conceived and designed the experiments; Hujun Liu performed Nos. the 51378073 and 51408048), the Rui KeyLiProgram Science and Technology Cooperation Projects experiments; Jun Zhou and analyzedfor theInternational data; Jun Zhou and Rui Li wrote the paper; Jianzhong Pei contributed analysis toolsNos. and revised paper. and 2016ZDJC-24), the China Postdoctoral Science Foundation of Shaanxi province (Grant 2014KW10-03 (Grant Nos. 2015M582591 and 2016T90880). Author Contributions: Rui Li and Jianzhong Pei conceived and designed the experiments; Hujun Liu performed the experiments; Jun Zhou and Rui Li analyzed the data; Jun Zhou and Rui Li wrote the paper; Jianzhong Pei contributed analysis tools and revised paper.
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Conflicts of Interest: The authors declare that there is no conflict of interests regarding the publication of this paper.
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Effect of Polymer Matrix on the Structure and Electric Properties of Piezoelectric Lead Zirconatetitanate/Polymer Composites Rui Li 1,2, *, Jun Zhou 1 , Hujun Liu 3 and Jianzhong Pei 1 1 2 3
*
Highway School, Chang’an University, Xi’an 710064, China; [email protected] (J.Z.); [email protected] (J.P.) School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore CCCC Fourth Harbor Engineering Institute Co., LTD., Guangzhou 510000, China; [email protected] Correspondence: [email protected]
Received: 27 June 2017; Accepted: 8 August 2017; Published: 14 August 2017
Abstract: Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 103 Hz, the dielectric and piezoelectric properties of PZT/poly(vinylidene fluoride) were both better than that of PZT/polyvinyl chloride (PVC). When the volume fraction of PZT was 50%, PZT/PVDF prepared by the hot-press method had better comprehensive electric property. Keywords: PZT/polymer; PVDF; PVC; dielectric; piezoelectric
1. Introduction In recent years, the use of piezoelectric materials to collect energy received more and more attention, the environmental characteristics of piezoelectric materials are also gaining popularity [1–4]. As a member of the new functional material family, piezoelectric actuators have been widely used in engineering and daily life because of their good piezoelectric effect, but their inflexibility and brittleness lead to processing difficulties and poor impact resistance, and so their applications are limited [5–7]. In the past, researchers improved the properties of PZT by changing its preparation condition, polarization condition, and the particle size in most cases, but there have been few studies to examine how the polymer affects PZT/PVDF. Compared with the pure PZT piezoelectric materials, PZT/polymer composites have many virtues such as lower density, better flexibility, stronger plasticity, easier performance improvement and so on. Mendes [8] researched the influence of particle size and the amount of PZT fillers on the PVDF matrix of measurement the dielectric and dynamic mechanical of PZT/PVDF, the results showed that the dielectric properties of the composites are mainly affected by the amount of the ceramic particles. As a polymer monomer, poly(vinylidene fluoride) (PVDF) is renowned for having excellent piezoelectric properties, as well as good mechanical and chemical properties, especially a wide processing temperature range to meet the industrial control system field [9–15]. As an engineering polymer, polyvinyl chloride (PVC) is widely used throughout the building materials industry because it has unique advantages such as waterproof, fireproof, and antistatic properties, PVC can be especially easily shaped and costs less than PVDF [16–23]. In this paper, PVDF and PVC were used to prepare PZT/polymer piezoelectric composite with PZT respectively, the microstructure of PZT/polymer composite was observed by scanning electron Materials 2017, 10, 945; doi:10.3390/ma10080945
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micrographs (SEM), the physical phases of the composite were analyzed by X-ray diffractometer (XRD), the effect of two kinds of polymer matrix on the electric properties of PZT/polymer composite materials were investigated. The results measured have great importance to the design of application domain of PZT/polymer composite materials. 2. Experimental 2.1. Materials PZT was supplied by Hongsheng Acoustic, Electronic Equipment Co. Ltd. in Baoding, China. PVDF was supplied by San AI Fu FR902 in Shanghai, China. PVC was from Nanjing Daoning Chemical Co. Ltd. in Nanjing, China. 2.2. Preparation of PZT/Polymer Composites The PZT and PVDF powder were weighed by the volume. Then they were mixed and the mixture was placed into a grinding bowl, next absolute ethyl alcohol was added, the powder was mixed with a stirring rod for 10 min. After the mixture was dried in an oven at 100 ◦ C for 25 min, the mixed powder of PZT and PVDF was put in the hot pressing mold, which was heated to 190 ◦ C for 30 min, PZT/PVDF composites with a diameter of 13 mm and a thickness of 1 mm were obtained. The above steps were repeated to mix the PZT and PVC, the temperature of the hot pressing mold was 175 ◦ C for 30 min, PZT/PVC composites with a diameter of 13 mm and a thickness of 1 mm were obtained. The pan was then dried in an oven and an electrode was coated thereon. It was placed in thermostatic silicone oil and polarized at a polarization voltage of 3 kV/mm and at 80 ◦ C for 30 min. Finally, the samples were tested after resting 24 h. 2.3. Measurements All these measurements were obtained at ambient temperature and pressure. The microstructures of PZT/polymer composites were characterized by XRD, FT-IR, and SEM, the dielectric constant (εr ) and the dielectric loss (tan δ) of PZT/Polymers composites were measured by a precision LCR digital bridge under 1 kHz, and the piezoelectric constant (d33 ) of PZT/Polymer composites were measured by ZJ-3AN-type quasi-static d33 measuring. 3. Results and Discussion 3.1. Structure and Morphology 3.1.1. XRD Figure 1 shows the XRD pattern of PZT/PVDF and PZT/PVC composites. It can be seen that there are no new diffraction peaks of XRD and the diffraction peak of PZT has not changed significantly. It is only because of the different crystallization of the polymer that there are different manifestations in the XRD of composite. PVDF is a semicrystalline polymer whose diffraction peak is weak and is basically covered when the PZT content is 50%. Figure 1b shows that there is no the diffraction peak of PVC caused by the PVC crystallinity is low. with the increase of the PZT content, the (002) diffraction peak becomes gets stronger gradually, that is, with the increase of PZT content and decrease of polymer content, the formation is beneficial to the polarization of the ceramic phase.
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Figure 1. (a) XRD pattern of PZT/PVDF composites; (b) XRD pattern of PZT/PVC composites. Figure 1. (a) XRD pattern of PZT/PVDF composites; (b) XRD pattern of PZT/PVC composites.
Figure 1. (a) XRD pattern of PZT/PVDF composites; (b) XRD pattern of PZT/PVC composites. It is not hard to find that the figure of PZT/PVDF composite is similar to the PZT/PVC, but the It is not hard to find that the figure of PZT/PVDF composite is similar to the PZT/PVC, PZT/PVC is slightly wider, but the polarization rate of the PVDF base composite is higher than that but slightly but the of the PVDF base composite is higher than It isthe notPZT/PVC hard to is find that wider, the figure of polarization PZT/PVDFrate composite is similar to the PZT/PVC, but the of the PVC base composite material at high content. When the content of PVDF is high, the PZT that ofisthe PVC base composite material at high rate content. When the base content of PVDF is high, thethan PZT that PZT/PVC slightly wider, but the polarization of the PVDF composite is higher polarization rate of PZT/PVDF composites is higher than that of PZT/PVC composites [24]. polarization of PZT/PVDF composites higher than that of of the PVC baserate composite material at highis content. When thePZT/PVC content composites of PVDF is[24]. high, the PZT
polarization rate of PZT/PVDF composites is higher than that of PZT/PVC composites [24]. 3.1.2. FT-IR FT-IR 3.1.2. Figure 2a is FT-IR spectra of PVDF powder. It can be seen from the absorption band that the PVDF primarily as α-phase, but exhibited one δabsorption phase absorption band wave primarily existed existed as α-phase, but exhibited only oneonly δ phase band with the with wavethe number −1 number of cm . Itspectra means it is difficult tothe obtain with the piezoelectric effect through −1510 Figure 2a is of PVDF Itβ-PVDF canthe beβ-PVDF seenpiezoelectric from absorption band of 510 cm . ItFT-IR means that it isthat difficult topowder. obtain with effect through the that hot the the hot pressing method. For the piezoelectric composites prepared by hot pressing, PVDF is mainly PVDF primarily existed as α-phase, butcomposites exhibitedprepared only onebyδhot phase absorption with the wave pressing method. For the piezoelectric pressing, PVDF isband mainly α crystal α crystal and does not have the piezoelectric properties. That is, PVDF mainly plays a role of −1 and of does the piezoelectric properties. That is,the PVDF mainly plays a role of connection in number 510not cmhave . It means that it is difficult to obtain β-PVDF with piezoelectric effect through connection in PZT/PVDF composites, and its piezoelectric properties can be neglected. However, due PZT/PVDF andthe its piezoelectric piezoelectric properties canprepared be neglected. However, due to the strong the hot pressingcomposites, method. For composites by hot pressing, PVDF is mainly to the strong polarity of C–F in PVDF, the effect properties of dielectricofproperties of the PZT/PVDF composites polarity of C–F in PVDF, the effect of dielectric the PZT/PVDF composites cannot be of α crystal and does not have the piezoelectric properties. That is, PVDF mainly plays a role cannot be neglected. Figure2b shows that the maximum value of the PVC absorption peak at 1248.82 − neglected. Figure 2b shows that theand maximum value of the PVC absorption peak at 1248.82 cm 1 , due connection in PZT/PVDF composites, itsadjacent piezoelectric properties can be neglected. However, −1, which cm caused by the oscillation of the –C– of the CH 2 functional group in the PVC and caused by the oscillation of the adjacent –C– of the CH2 functional group in the PVC and its to thewhich strong polarity of C–F The in PVDF, theabsorption effect of dielectric properties of the−cm PZT/PVDF composites −1 was formed its connected –Cl– atoms. vibration peak of ethylene at 1429.08 connected –Cl– atoms. The vibration absorption peak of ethylene at 1429.08 cm 1 was formed duedue to cannot be neglected. Figure2b shows that the maximum value of the PVC absorption peak at 1248.82 to shear distortion. shear distortion. Figure 2a is FT-IR spectra of PVDF powder. It can be seen from the absorption band that the PVDF 3.1.2. FT-IR
cm−1, which caused by the oscillation of the adjacent –C– of the CH2 functional group in the PVC and its connected –Cl– atoms. The vibration absorption peak of ethylene at 1429.08 cm−1 was formed due to shear distortion.
Figure (a) FT-IR Figure 2. 2. (a) FT-IR spectra spectra of of PVDF PVDF powders; powders; (b) (b) FT-IR FT-IR spectra spectra of of PVC PVC powders. powders.
3.1.3. 3.1.3. SEM The of PZT/PVC PZT/PVCcomposite compositeprepared prepared PVC with volume fractions of 40%, and The SEM of byby PVC with volume fractions of 40%, 50%50% and 60% 60% respectively were shown in Figure 3. It can befrom seen from 3,of when the volume respectively were2. shown in Figure 3.ofItPVDF can bepowders; seen 3, when the volume fractionfraction of PZT Figure (a) FT-IR spectra (b)Figure FT-IRFigure spectra PVC powders. of PZT was large number PZT particles were ‘suspended’ in the PVDF and PVDF some was 40%, a 40%, large anumber of PZTof particles were ‘suspended’ in the PVDF matrix,matrix, and some powder displays the reunion phenomenon. As the volume PZT increased to 50%, although displays the reunion phenomenon. As the fraction volume of fraction of PZT increased to 50%, 3.1.3.PVDF SEM powder some PZTsome powder completely wrappedwrapped in the PVDF powder, most PZTmost particles were exposed although PZTwas powder was completely in the PVDF powder, PZT particles were The SEM of PZT/PVC composite by PVC with 40%,the 50% and 60% to each other, and the PVDF powderprepared was embedded in the gapvolume betweenfractions particles.of When volume
respectively were shown in Figure 3. It can be seen from Figure 3, when the volume fraction of PZT was 40%, a large number of PZT particles were ‘suspended’ in the PVDF matrix, and some PVDF powder displays the reunion phenomenon. As the volume fraction of PZT increased to 50%, although some PZT powder was completely wrapped in the PVDF powder, most PZT particles were exposed
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exposed to each other, and the PVDF powder was embedded in the gap between particles. When the fractionfraction of PZT PZT increases increases to 60%, 60%,to the PZTthe particles are almost almost completely in contact contact with each each other, volume of PZT increases 60%, PZT particles are almost completely in contact withother, each fraction of to the PZT particles are completely in with and the distribution of PZT particles is very uniform. other, and the distribution PZT particles very uniform. and the distribution of PZTofparticles is veryisuniform. Figure 44 isisthe theSEM SEMimages imagesof ofPZT/PVC PZT/PVC composite prepared by by PVC PVC with with the the volume volume fractions fractions Figure composite prepared the SEM images of PZT/PVC of 40%, 40%, 50% 50% and and 60%, 60%, respectively. respectively.It It can be seen from the Figure 4 that the PZT particles in composite of respectively. can be seen from the Figure 4 that the PZT particles in composite It can materials are are distributed distributed evenly evenly in in the the PVC PVC matrix. matrix. With With the the increase increase of of PZT PZT content, content, the the thickness thickness materials PZT content, thickness of the the PVC PVC layer layer is is reduced reduced and andthe thedistance distancebetween betweenPZT PZTparticles particlesdecreases. decreases. The The interface interface of the PVC layer is reduced and the distance between PZT particles decreases. interface combination between PZT and PVC is better, even the PZT content of PZT/PVC composite is high high combination between PZT and PVC is better, better, even even the the PZT PZTcontent contentof ofPZT/PVC PZT/PVC composite is (PZT:PVC = 60:40), PVC PVC is is still still tightly tightly wrapped wrapped around around the the PZT PZT particles. particles. This This is is due due to to the the PVC PVC (PZT:PVC == 60:40), the PZT particles. having satisfied satisfied bonding bonding performance. performance. The small number number of of having The composites composites have have dense dense matrix and aa small pores, which is mainly caused by the PZT particle extraction process. pores, pores, which which is is mainly mainly caused caused by by the the PZT PZT particle particle extraction extraction process. process.
Figure 3. 3. (a) (a) The The SEM SEM images imagesof ofthe thePZT/PVDF PZT/PVDF (40:60); (40:60); (b) (b) The The SEM SEM images images of of the the PZT/PVDF PZT/PVDF (50:50); (50:50); Figure (40:60); PZT/PVDF PZT/PVDF (c)The TheSEM SEM images of the PZT/PVDF (c) images of the PZT/PVDF (60:40). SEM images of the PZT/PVDF (60:40).
Figure 4. 4. (a) (a) The The SEM SEM images images of the PZT/PVC (40:60); (b) The SEM images ofof the PZT/PVC (50:50); (c) Figure 4. The SEM images of the PZT/PVC (50:50); (c) Figure (a) The SEM imagesof ofthe thePZT/PVC PZT/PVC(40:60); (40:60);(b) (b) The SEM images the PZT/PVC (50:50); The SEM images of the thethe PZT/PVC (60:40). The SEM images of PZT/PVC (60:40). (c) The SEM images of PZT/PVC (60:40).
3.2. Effects Effects of Polymer Polymer on on the the Dielectric Dielectric Properties Properties of of PZT/Polymers PZT/Polymers 3.2. 3.2. Effects of of Polymer on the Dielectric Properties of PZT/Polymers The frequency frequency dependence dependence of of dielectric dielectric constant constant (ε (εrr)) of of PZT/polymers PZT/polymers was was shown shown in in Figure Figure 5. 5. The The frequency dependence of dielectric constant (ε r ) of PZT/polymers was shown in Figure 5. The frequency stability of the PZT/PVDF composites is lower than that of the PZT/PVC composites. The frequency frequency stability stability of of the the PZT/PVDF PZT/PVDF composites lower than than that that of of the the PZT/PVC PZT/PVC composites. The composites is is lower composites. The dielectric dielectric constant constant of of the the PZT/PVDF PZT/PVDF composites composites and and the the PZT/PVC PZT/PVC composites composites has has the same same trend The The dielectric constant of the PZT/PVDF composites and the PZT/PVC compositesthe has the trend same as the change of the PZT volume content. The dielectric constant of PZT/polymer composites as theaschange of the PZTPZT volume content. PZT/polymer composites composites trend the change of the volume content.The Thedielectric dielectricconstant constant of of PZT/polymer increased by by increasing increasing the the addition addition of of PZT, PZT, but but the the extent extent of of the the increase increase was was different. different. increased increased by increasing the addition of PZT, but the extent of the increase was different. The dielectric dielectric properties properties of of PZT/PVDF PZT/PVDF composites composites were higher higher than the the dielectric properties properties of of The The dielectric properties of PZT/PVDF composites were were higher than than the dielectric dielectric properties of PZT/PVC composite with the same PZT contents. This indicates that the dielectric constant of the PZT/PVC composite constant of of the the PZT/PVC composite with with the the same same PZT PZT contents. contents. This This indicates indicates that that the the dielectric dielectric constant PZT/polymer composite composite materials materials is is closely closely related related to to the the polymer polymer matrix’s matrix’s own own permittivity, permittivity, and and PZT/polymer PZT/polymer composite materials is closely related to the polymer matrix’s own permittivity, and the the polymer polymer with with high high dielectric dielectric constant constant can can obtain obtain composite composite material material with with aa high high dielectric the polymer with high dielectric constant can obtain composite material with a high dielectric dielectric constant. constant. When the PZT content of PZT/PVC composite reached 40%, and when PZT/PVDF constant. When the PZT content of PZT/PVC composite reached 40%, and when PZT/PVDF When the PZT content of PZT/PVC composite reached 40%, and when PZT/PVDF composite reaches composite reaches reaches 50%, 50%, the the curve curve shows shows aa strong strong resonance resonance peak, peak, the the reason reason is is that that the the orientation orientation composite 50%, the curve shows a strong resonance peak, the reason is that the orientation polarization comes polarization comes from the dipole of the PZT particles, the larger PZT content, the greater the polarization comes from dipolethe of larger the PZT larger PZT content, thecontribution greater the from the dipole of the PZTthe particles, PZTparticles, content, the the greater the polarization polarization contribution and the more obvious the resonance peak. polarization the more obvious the resonance peak. and the morecontribution obvious the and resonance peak.
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Figure 5. (a) Variation of dielectric constant of PZT/PVDF composites with frequency; (b) Variation of dielectric constant of PZT/PVC composites with frequency. Figure 5. (a) Variation of dielectric constant of PZT/PVDF composites with frequency; (b) Variation of
Figure 5. (a) Variation of dielectric constant losses of PZT/PVDF with (b) Variation Thedielectric relationship between the dielectric (tan δ) composites of two kinds of frequency; PZT/polymer composites is constant of PZT/PVC composites with frequency. of dielectric constant of PZT/PVC composites with frequency. shown in Figure 6. It can be seen that, with the increase of frequency, the tan δ of both composite are relationship between the dielectric (tan δ) of two kindsitofisPZT/polymer compositesof the 4 Hz), slightly The decreasing in the condition of lowlosses frequency (104 Hz), the tan δ of PZT/PVC change range differed greatly 4 Hz), it is due to the relaxation of the are slightly decreasing in the condition of low frequency (10 the tan δ of PZT/PVC change range differed greatly 4 slightly decreasing in theloss condition of low frequency (10 tan of PZT/PVC change range At the same time, the dielectric loss of PVDF matrix composite is higher than that of PZT/PVC frequency the dielectric loss of the PZT/PVDF composites increases dramatically with the frequency increase but the values ofand all PVC tan δ are small. In contrast with the increase of composite. The dielectric loss curves of PVDF composite the At the same time, the dielectric loss of PVDF matrixmatrix composite is higherdisplay than that ofresonance PZT/PVC peak, frequency the dielectric loss of the PZT/PVDF composites dramatically in particular, the PZT content of PZT/PVC hasincreases a composite loss peak when the content is 40%, composite. The dielectric loss curves of PVDFcomposite and PVC matrix display the PZT resonance peak, At the same time, the dielectric loss of PVDF matrix composite is higher than that of PZT/PVC which is mainlythe due to content the relaxation polarization caused dipole PZT. in particular, PZT of PZT/PVC composite has a by lossthe peak whenofthe PZT content is 40%, composite. dielectric curves ofpolarization PVDF and caused PVC matrix display the resonance peak, which isThe mainly due to loss the relaxation by thecomposite dipole of PZT.
in particular, the PZT content of PZT/PVC composite has a loss peak when the PZT content is 40%, which is mainly due to the relaxation polarization caused by the dipole of PZT.
Figure 6. (a) Variation of dielectric loss of PZT/PVDF composites with frequency; (b) Variation of
Figure 6. (a) Variation of dielectric loss of PZT/PVDF composites with frequency; (b) Variation of dielectric loss of PZT/PVC composites with frequency. dielectric loss of PZT/PVC composites with frequency.
3.3. Effects of Polymer on the Piezoelectric Properties of PZT/Polymers
(a) Variation of Piezoelectric dielectric lossProperties of PZT/PVDF composites with frequency; (b) Variation of 3.3. Figure Effects 6. of Polymer on the of PZT/Polymers
As can beofseen in Figure 7, with with the increase of the PVDF volume fraction, the piezoelectric dielectric loss PZT/PVC composites frequency. As can be seen Figure 7, with the increase of the PVDF volume fraction, piezoelectric strain constant (d33in ) and the piezoelectric voltage constant (g33 ) of PZT/PVDF boththe presented decline strain gradually, this is because PVDF mainly played constant a role of a (g connection phase in PZT/PVDF, and PZT constant (d ) and the piezoelectric voltage 33) of PZT/PVDF both presented decline 3.3. Effects of 33 Polymer on the Piezoelectric Properties of PZT/Polymers providedthis the high piezoelectric Therefore, to obtain the piezoelectric properties gradually, is because PVDFperformance. mainly played a role in oforder a connection phase in PZT/PVDF, and PZT As can behigh seenproperties in Figure of 7, the with the increase of the volume fraction, the piezoelectric and mechanical composite system, thePVDF volume fraction of PZT should not bestrain provided the piezoelectric performance. Therefore, in order to obtain thephase piezoelectric properties constant (d3350%. ) and the piezoelectric voltagesystem, constant 33) of PZT/PVDF both presented decline than andless mechanical properties of the composite the(gvolume fraction of PZT phase should not be Figure 7b shows thePVDF relation curve played betweenathe piezoelectric properties of PZT/PVC composite gradually, this is because mainly role of a connection phase in PZT/PVDF, and PZT less than 50%. prepared by PZT and different volume fraction of PZT. As can be seen in Figure 7b, with the increase provided the7b high piezoelectric performance. Therefore, in order to obtain the piezoelectric Figure shows the relation curve between the piezoelectric properties of PZT/PVCproperties composite of the volume fraction of PZT, the d and the g of the composites increase gradually, when 33 33 and mechanical properties of the composite system, the volume fraction of PZT phase but should not be
prepared by PZT and different volume fraction of PZT. As can be seen in Figure 7b, with the increase less than 50%. fraction of PZT, the d33 and the g33 of the composites increase gradually, but when the of the volume Figure 7b shows thePZT relation curvethan between propertiesdecreases of PZT/PVC composite volume fraction of the is more 50%, the the piezoelectric d33 of the composites with a certain prepared by PZT and different volume fraction of PZT. As can be seen in Figure 7b, with the increase amplitude, because when the PZT volume fraction is from 50% to 60%, the PVC particles of the of the volume fraction of PZT, the d33 and the g33 of the composites increase gradually, but when the
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the volume fraction of the PZTais coating more than 50%, thethe d33 ceramic of the composites decreases a certain composite material will form around layer. The resultswith show that the amplitude, because when the PZT volume fraction is from 50% to 60%, the PVC particles piezoelectric properties of the composites show a decreasing trend when the content of of the PZT in composite material will form a coating around the ceramic layer. The results show that the piezoelectric ceramics exceeds 50%. Although the cohesive force between the two phases is increased, the charge properties of the composites show a decreasing trend when the content of PZT in ceramics exceeds transfer ability of the composites is reduced. 50%. Although the cohesive force between the two phases is increased, the charge transfer ability of This is illustrated in the 0–3 composites, the electroactive particles are under-solicited because the composites is reduced. of the difference of dielectric constant betweenthe ceramics and polymers and because of the difference This is illustrated in the 0–3 composites, electroactive particles are under-solicited because of elastic When constant the volume fraction of the is more 60%, thedifference piezoelectric of the modulus difference [25]. of dielectric between ceramics andPZT polymers and than because of the properties of modulus the PZT/PVDF increase with thefraction increase PZT volume are still lower of elastic [25]. When the volume of of thethe PZT is more thanfraction, 60%, thebut piezoelectric of the PZT/PVDF increase with the increase of the PZT volume fraction, but are still lower thanproperties that of PZT/PVC composites. than that of PZT/PVC composites.
Figure 7. (a) Effect of PVDF volume fraction of the d33 of PZT/PVDF; (b) Effect of PVDF volume
Figure 7. (a) Effect of PVDF volume fraction of the d33 of PZT/PVDF; (b) Effect of PVDF volume fraction of the g33 of PZT/PVDF. fraction of the g33 of PZT/PVDF. 4. Conclusions
4. Conclusions (1)
(1)
(2)
(3)
(4)
Two kinds of PZT/polymer composites were prepared by the hot pressing process using two polymers ascomposites the matrix. were The results showby that polymer matrix has ausing great two Twothermoplastic kinds of PZT/polymer prepared thethehot pressing process influence on the piezoelectric and dielectric properties of the PZT/polymer composites. thermoplastic polymers as the matrix. The results show that the polymer matrix has a great (2) The process preparation and of PZT/PVDF from semi-crystalline polymer PVDF was influence on thefor piezoelectric dielectriccomposite properties of the PZT/polymer composites. investigated. The piezoelectric properties of PZT/PVDF are the best when the PZT content is The process for preparation of PZT/PVDF composite from semi-crystalline polymer PVDF was higher than 50%. The dielectric constant of PZT/PVDF composites is better than PZT/PVC, and investigated. The piezoelectric properties of PZT/PVDF are the best when the PZT content is the dielectric loss is slightly higher than that of the PZT/PVC when the frequency is 1 kHz. higher than 50%. The dielectric constant of PZT/PVDF composites is better than PZT/PVC, and (3) The PZT/PVC composites prepared by combining PZT with PVC can measure the resonance the dielectric loss is slightly higher than that of the PZT/PVC when the frequency is 1 kHz. peak of the PZT when the content of PZT was 40%. The g33 of PZT/PVC composites is better than The that PZT/PVC composites prepared with The PVCd can measure the resonance of PZT/PVDF composites whenby thecombining PZT contentPZT is 30–50%. 33 of PZT/PVC composite peakisofobviously the PZTbetter whenthan the content of PZT was 40%. TheTherefore, g33 of PZT/PVC composites is better that of PZT/PVDF composite. the PZT/PVC composites will than that achieve of PZT/PVDF composites when the PZT content is 30–50%. The d33 of PZT/PVC composite high electromechanical coupling coefficients. 3 is obviously better than that of PZT/PVDF composite. Therefore, the PZT/PVC composites (4) Under the condition of frequency is 10 Hz, the dielectric and piezoelectric properties of the will PZT/PVC were both better than PZT/PVDF. When the volume fraction of PZT was 50%, achieve high electromechanical coupling coefficients. 3 the PZT/PVC composites prepared by the hot-press method and couldpiezoelectric achieve excellent electrical Under the condition of frequency is 10 Hz, the dielectric properties of the performance. The εbetter d33 was 16.2When Pc/N,the the volume g33 was 28.26 mV·m/N, andwas the tan δ the r was 65.75, PZT/PVC were both thanthe PZT/PVDF. fraction of PZT 50%, was only 0.037. PZT/PVC composites prepared by the hot-press method could achieve excellent electrical
performance. TheThe εr was 65.75, d33 was by 16.2 the Natural g33 wasScience 28.26 mV·m/N, the tan Acknowledgments: research wasthe supported thePc/N, National Foundationand of China (Grant Nos. 51378073 and 51408048), the Key Program for International Science and Technology Cooperation was only 0.037. Projects of Shaanxi province (Grant Nos. 2014KW10-03 and 2016ZDJC-24), the China Postdoctoral Science Foundation (Grant Nos. 2015M582591 and 2016T90880).
δ
Acknowledgments: The research was supported by the National Natural Science Foundation of China (Grant Author Contributions: Rui Li and Jianzhong Pei conceived and designed the experiments; Hujun Liu performed Nos. the 51378073 and 51408048), the Rui KeyLiProgram Science and Technology Cooperation Projects experiments; Jun Zhou and analyzedfor theInternational data; Jun Zhou and Rui Li wrote the paper; Jianzhong Pei contributed analysis toolsNos. and revised paper. and 2016ZDJC-24), the China Postdoctoral Science Foundation of Shaanxi province (Grant 2014KW10-03 (Grant Nos. 2015M582591 and 2016T90880). Author Contributions: Rui Li and Jianzhong Pei conceived and designed the experiments; Hujun Liu performed the experiments; Jun Zhou and Rui Li analyzed the data; Jun Zhou and Rui Li wrote the paper; Jianzhong Pei contributed analysis tools and revised paper.
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Conflicts of Interest: The authors declare that there is no conflict of interests regarding the publication of this paper.
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