Environ Sci Pollut Res DOI 10.1007/s11356-015-4993-6
POLLUTION CONTROL TECHNOLOGIES AND ALTERNATE ENERGY OPTIONS
Synthesis and thermoluminescence properties of rare earth-doped NaMgBO3 phosphor Z. S. Khan 1 & N. B. Ingale 2 & S. K. Omanwar 3
Received: 23 February 2015 / Accepted: 30 June 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Rare earth (Dy3+ and Sm3+)-doped sodium magnesium borate (NaMgBO3) is synthesized by solution combustion synthesis method keeping their thermoluminescence properties in mind. The reaction produced very stable crystalline NaMgBO3:RE (RE=Dy3+, Sm3+) phosphors. The phosphors are exposed to 60Co gamma-ray radiations dose of varying rate from 5 to 25 Gy, and their TL characteristics with kinetic parameters are studied. NaMgBO3:Dy3+ phosphor shows two peaks for lower doping concentration of Dy3+ while it reduced to single peak for the higher concentrations of activator Dy3+. NaMgBO3:Dy3+ shows the major glow peak around 200 °C while NaMgBO 3 :Sm 3+ phosphors show two well-separated glow peaks at 200 and 332 °C respectively. The thermoluminescence intensity of these phosphors was compare with the commercially available TLD-100 (Harshaw) phosphor. The TL responses for gamma-ray radiations dose were found to be linear from 5 to 25 Gy for both phosphors while the fading in each case is calculated for the tenure of 45 days.
Responsible editor: Philippe Garrigues * Z. S. Khan [email protected] 1
Department of Physics, BS Patel College, Pimpalgaon kale 443403, India
2
Prof. Ram Meghe Institute of Technology and Research, Badnera, Amravati 444701, India
3
Department of Physics, SGB Amravati University, Amravati 444602, India
Keywords Thermoluminescence . NaMgBO3 . Solution combustion synthesis method . Rare earths . Kinetic parameters
Introduction Borate phosphors attract the attention of researchers due to their applications in various fields. Borates possess excellent properties as host structures of phosphors in which isolated planer [BO3]3− groups (Nagpure et al. 2011). In borate compounds, boron atom is coordinated by oxygen atoms to form a variety of atomic groups that affect the physical properties in general and optical properties in particular (Wu et al. 2004). The NaMgBO3 phosphor may show such applications due to the presence of isolated planar [BO3]3− group at an appropriate position. Borate compound LiCaBO3: Tb, Dy (Bajaj and Omanwar 2012) find significant applications as TLD phosphor used in personal dosimetry. A variety of BOatomic group are considered to be a dominant factor in their physical properties and a class of phosphors with high-quality performances, especially when doped with proper activators (Nagpure and Omanwar 2012). The main reason of emphasizing on borate is their variety of structure types, transparency to a wide range of wavelengths, high laser damage tolerance, and high optical quality (Bajaj and Omanwar 2013). Combustion synthesis is a good low-cost, one-step, and lowtemperature method for the synthesis of borates, phosphates, and silicates (Khan et al. 2015; Bhatkar et al. 2002; Thakare et al. 2007; Bhatkar et al. 2007; Sonekar et al. 2007; Sonekar et al. 2009). Some orthoborates,
Environ Sci Pollut Res Table 1
Balanced chemical reactions during the combustion method
S.N. Product 1. 2.
Corresponding reaction with balanced molar ratios of precursors
NaMgBO3:Dy3+ NaNO3 +Mg(NO3)2 +H3BO3 +5CO(NH2)2 +7.5 NH4NO3 +x Dy2O3⟶Na Mg1-xBO3 : x Dy3+ + Gaseous (H2O, NH4, NO2, etc.) [x=0.001, 0.002, 0.005, 0.01 and 0.02] NaMgBO3:Sm3+ NaNO3 +Mg(NO3)2 +H3BO3 +5CO(NH2)2 +7.5 NH4NO3 +x Sm2O3⟶NaMg1-xBO3 : x Sm3+ + Gaseous (H2O, NH4, NO2, etc.) [x=0.001, 0.002, 0.005, 0.01 and 0.02]
LiMgBO3:Dy3+ (Bajaj and Omanwar 2014), NaCaBO3 (Wu et al. 2005), LiCaBO 3 (Anishia et al. 2010), LiSrBO3 (Cheng et al. 2001), LiBaBO3 (Cheng et al. 2001), NaBaBO3 (Kononova et al. 2003), N a S r B O 3 : T b 3 + ( N a g p ur e a n d O m a n w a r 2 01 2 ) , LiSrBO 3 :Sm 3+ (Pitale et al. 2011), NaSrBO 3 :Sm 3+ (Kumar et al. 2013), NaCaBO 3 : Ce 3+ , Mn 2+ (Sun et al. 2013), NaCaBO3:Ce3+, Tb3+, Mn2+ (Zhang and Gong 2014), NaCaBO3:Sm3+ (Bedyal et al. 2014), etc., have been synthesized with different methods to explore their crystal structure and luminescent properties for probable applications in medical as well as industrial fields. Recently, Wu et al. (2007) effectively synthesized NaMgBO 3 by solid-state reaction and explained the structure of NaMgBO3 which is somewhat similar to that of NaSrBO3 orthoborates. In this paper, we describe synthesis and characteristics of NaMgBO 3:RE (RE = Dy3+ and Sm3+) using the solution combustion synthesis method. The prepared materials are considered for its TLD properties under gamma-ray exposure with the impacts of rare earth (RE) activators on it.
Fig. 1 XRD pattern for NaMgBO3 Host
Experimental The NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphors are prepared by well-established solution combustion synthesis method (Bhatkar et al. 2002; Thakare et al. 2007; Bhatkar et al. 2007; Sonekar et al. 2007; Sonekar et al. 2009; Bajaj and Omanwar 2014; Wu et al. 2005). During the reaction, the stoichiometric amounts of high purity starting components, NaNO3 (G.R.), Mg (NO3)2·4H2O (Analytical Reagent), H3BO3 (A.R.), CO (NH2)2 (G.R.), NH4NO3 (G.R.), Dy2O3, and Sm2O3 (activators) are calculated on the basis of molar ratio (using oxidizer/fuel ratio) and are thoroughly mixed in the agate mortar by adding little amount of double distilled water and an aqueous homogeneous solution was obtained. Ammonium nitrate is nothing but the oxidizer which is used for combustion along with the fuel (here urea) in the reaction. The solution was then transferred into a China basin. The China basin was then kept into preheated muffle furnace maintained at (550±10 °C). The solution boils, foams, and ignites to burn with the flame, and a voluminous, foamy powder was obtained. The entire combustion was
Environ Sci Pollut Res
Fig. 2 SEM image of a NaMgBO3:Dy3+ and b NaMgBO3:Sm3+
over within 5 min. Following the combustion, the resulting fine powder was annealed in open air at 750 °C for 90 min and allowed to cool down at room temperature. The prepared sample was confirmed by Rigaku Miniflex X-Ray Diffractometer with scan speed of 2.00°/min and with Cu Kα radiation (λ= 1.5406 Å). Scanning electron microscope (SEM) images were taken from Synthetic and Art Silk Mills Research Association (SASMIRA), Mumbai. Irradiations with 60Co gamma-rays source was utilized from RTM Nagpur University while Thermoluminescence (TL) glow curves were recorded with the help Fig. 3 TL glow curve NaMgBO3: RE (RE=Dy3+, Sm3+) compared with commercial phosphor TLD-100H
of TL 1009I reader designed and offered by Nucleonix system with constant heating rate of 5 °C/s (Table 1).
Results and discussion XRD analysis Figure 1 represents the X-ray diffraction (XRD) pattern for the NaMgBO3 synthesized by solution combustion
Environ Sci Pollut Res Fig. 4 Deconvoluted curves from experimental curve for NaMgBO3:Dy3+
synthesis method which is in good agreement with the International Centre for Diffraction Data (ICDD) file 00059-0808. The sharp peaks in the XRD patterns also confirm the highly crystalline nature of prepared sample. All the main peaks favor the confirmation of the desired phosphor.
NaMgBO 3:Sm 3+ phosphor. The combustion synthesis method does not guaranteed the nanostructure of the prepared sample. It shows the moist particles with an irregular shapes and the range of particle size 1– 5 μm. TL glow curve
Morphology Figure 2 represents the SEM image showing morphology of as synthesized (a) NaMgBO 3 :Dy 3+ and (b)
Fig. 5 Deconvoluted curves from experimental curve for NaMgBO3:Sm3+
The TL glow curve of NaMgBO3 with different concentration of Dy3+ and Sm3+ for a test dose of 15 Gy is shown in Fig. 3 obtained at heating rate 5 °C/s. For
Environ Sci Pollut Res Table 2 Phosphor
Kinetic parameters for NaMgBO3:Dy3+ and NaMgBO3:Sm3+ Peak
NaMgBO3:Dy3+ Main peak High temperature peak 3+ NaMgBO3:Sm Main peak High temperature peak
E(eV) S(s−1) 0.659 1.505 0.864 1.38
8.76×105 1.75×1012 3.53×108 6.68×1010
Tm(°C) 219 317 200 332
NaMgBO3:Dy3+, the glow curve consists of two peaks nearly at 219 and 317 °C while for NaMgBO3:Sm3+, the glow curve consists of two peaks about 200 and 332 °C. The main aspect for TLD material is that for dosimetry purpose, it is desirable for the detector to have glow curve peak around 200–250 °C, which is partially filled by this phosphor at least for the first peak. This temperature range ensures that the trap depth is large enough without appreciable trap emptying at normal temperatures (Bajaj and Omanwar 2012; Koparkar et al. 2013). Also, this temperature range is low enough such that the interference due to black body radiation signal is negligible. Hence, it increases the interest of further studies on NaMgBO3. Thermoluminescence glow curve of NaMgBO 3:RE (RE = Dy3+ and Sm3+) prepared with solution combustion method was compared with the TL glow curve obtained from standard LiF:MCP under same dose conditions. TL intensity of main peak of our NaMgBO 3 :Dy 3+ phosphor is about 95 % intense as compared to that of LiF:MCP, while the intensity of main peak of NaMgBO 3 :Sm 3+ phosphor is about 50 % intense as that of LiF:MCP. Glow curve structure is confirmed by deconvolution of peak by using peak fit software (Bajaj and Omanwar 2013); the obtained
Fig. 6 Dose linearity of glow peak intensity in NaMgBO3:RE (RE=Dy3+ and Sm3+)
Fig. 7 Effect of doping concentration on NaMgBO3:Dy3+
peaks are simple and symmetric for both the phosphors NaMgBO 3 :RE (RE = Dy 3+ and Sm 3+ ) as shown in Figs. 4 and 5. Kinetic studies The TL glow curves for NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphors were deconvoluted by using the Peak Fit software as shown in Figs. 4 and 5, respectively. We employed the Chen’s peak shape method (Chen Reuven 1976) to analyze the activation energy of both NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphors by the method mentioned by Mckeever (1993) using Eq. (1): E ¼ cγ kT m2 =γ −bγ ð2kT m Þ ð1Þ where γ stands for τ, δ, or ω. The values of τ, δ, and ω are, respectively, determined by low-temperature halfwidth (τ = Tm –T1), high-temperature half-width (δ =T2–
Environ Sci Pollut Res Fig. 8 Effect of doping concentration on NaMgBO3:Sm3+
Tm), and full width (ω=T2 –T1). For first-order kinetics, the values of the cγ and bγ depending on τ, δ, or ω (Mckeever 1993) and k is Boltzmann constant. To analyze the frequency factor s of the glow curve values, the activation energy obtained from Eq. (1) and heating rate (β) at which the glow curves are recorded were used in Eq. (2). βE= kT m2 ¼ se½−E=kT m
ð2Þ
The summaries of calculated results are represented in Table 2.
Dose response The TL material is said to be good when its response to absorbed dose is linear over the wide range. To study the linearity, five samples were irradiated simultaneously for each level of dose. Each data point corresponds to the mean of the five readings. The linearity was observed in the range from 5 to 25 Gy as shown in Fig. 6. The relationship between the TL response of first peak and the absorbed dose for NaMgBO3:Dy3+ and NaMgBO 3 :Sm 3+ phosphor is shown in Fig. 6 which is found to be linear. The role played by dysprosium (Dy3+) activator is to enhance the energy in Fig. 9 Fading Effect of NaMgBO3:Dy3+ phosphor
NaMgBO 3 host as compared to samarium (Sm3+) as shown in Fig. 6. Effect of dopant concentrations Concentration of Dy3+ and Sm3+ in host was selected as per formula NaMg1−x BO3:REx (RE = Dy3+ and Sm3+) and varied from 0.1 mol to 2 mol%. It was observed that RE concentration has significant impact on the peak height of main as well as higher temperature glow peak. With increasing the concentration of RE (Dy 3+ and Sm3+), TL intensity of main glow peak, i.e., 219 °C as well as 200 °C respectively in NaMgBO3:Dy3+ and NaMgBO3:Sm3+, increases. The optimum concentration of RE in NaMgBO3:Dy3+ was found to be 0.005 mol of Dy 3+ while for NaMgBO 3 :Sm 3+ , it was 0.1 mol of Sm3+. In other words, on further increase of concentration, peak height decreases suddenly which is considered as concentration quenching of RE in NaMgBO3:RE in each case. Figures 7 and 8 show the variation of TL intensity with RE concentration. Fading effect While operating in the desired environment, stability of the material should be unaffected for the undesired sig-
Environ Sci Pollut Res Fig. 10 Fading Effect of NaMgBO3:Sm3+ phosphor
nals. Hence, fading effect is essential to check for particular duration of time regarding specially for optical signals. The loss in TL before readout may occur due to heat or light or any other means with respect to time. A dosimeter which is continuously exposed to sunlight or fluorescent lamp may lose part of its TL signal by optical stimulation. For dosimetry applications, the phosphor should be free from such optical effects. Hence, five samples of same dose were irradiated simultaneously. Each data point corresponds to the mean of the five readings. The TL material NaMgBO3:RE (RE= Dy3+ and Sm3+) shows linear intensity of glow peak up to 45 days and there was constancy found in results. The overall fading found in intensity was 5 % over the period 45 days; also the nature of each TL peak remained the same which supports the storage of sample not affecting the defects in crystallites. The fading effect in NaMgBO3:RE (RE=Dy3+ and Sm3+) was represented in Figs. 9 and 10 respectively.
Conclusion We synthesized NaMgBO3:RE (RE = Dy3+ and Sm3+) phosphors by one-step, low-cost, and low-temperature solution combustion method. TL characteristics and some dosimetric properties of Dy3+ and Sm3+ activated NaMgBO 3 phosphor were investigated in detail. The trap parameters, i.e., activation energy and frequency factor of the TL glow curve of the sample, were calculated by peak shape method. The so-prepared phosphor NaMgBO3 host shows impact of rare earth activators on it intensity (energy). NaMgBO 3 :Dy 3 + leads with NaMgBO3:Sm3+ in terms of energy. The TL and dosimetric characteristics implied the potential of NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphor as γray TL materials in the personal protection dosimetry field and radiation dosimetry Acknowledgments ZSK is grateful to the UGC-New Delhi, for financial support, and to the Head, Department of Physics, SGB Amravati University, for providing necessary facilities
References Anishia SR, Jose MT, Annalakshmi O, Ponnusamy V, Ramasamy V (2010) Dosimetric properties of rare earth doped LiCaBO3 thermoluminescence phosphors. J Lumin 130:1834–1840 Bajaj NS, Omanwar SK (2013) Combustion synthesis and characterization of phosphor KSr4 (BO3)3:Dy3+. Opt Mater 35:1222–1225 Bajaj NS, Omanwar SK (2014) Advances in synthesis and characterization of LiMgBO3:Dy3+. Optik Int J Light Electron Opt 1–4 Bajaj NS, Omanwar SK (2012) J Rare Earths 30:1005–1008 Bedyal AK, Kumar V, Ntwaeaborwa OM, Swart HC (2014) A promising orange-red emitting nanocrystalline NaCaBO3: Sm 3+ phosphor for solid state lightning. Mater Res Express 1: 015006–015012 Bhatkar VB, Omanwar SK, Moharil SV (2007) Opt Mater 29:1066–1070 Bhatkar VB, Omanwar SK, Moharil SV (2002) Phys Stat Sol 191:272– 276 Cheng WD, Zhang H, Lin QS, Zheng FK, Chen JT (2001) Chem Mater 13:1841 Khan ZS, Ingale NB, Omanwar SK (2015) Synthesis of thermoluminescence α-Ca2P2O7:Eu3+ bio nanomaterial. Mater Lett. doi:10.1016/j. matlet.2015.05.038 Kononova NG, Kokh AE, Bekker TB, Furmanova NG, Maksimov BA, Molchanov VN, Fedorov PP (2003) Growth and structure of barium sodium orthoborate NaBaBO3, crystals. Crystallogr Rep 48:1114– 1116 Koparkar KA, Omanwar SK, Virk HS, (2013) Recent advances and opportunities in TLD materials: a review. 75–110 Kumar V, Bedyal AK, Pitale SS, Ntwaeaborwa OM, Swart HC (2013) Synthesis, spectral and surface investigation of NaSrBO3: Sm3+ phosphor for full color down conversion in LEDs. J Alloys Compd 554:214–220 Mckeever SWS (1993) In: Chai GG, Wu F, Wang ST (eds) Thermoluminescence of solids. Atomic Energy Press. (in Chinese) Nagpure PA, Bajaj NS, Sonekar RP, Omanwar SK (2011) Indian J Pure Appl Phys 49:799–802 Nagpure PA, Omanwar SK (2012) J Rare Earths 30:856–859 Pitale SS, Nagpure IM, Kumar V, Ntwaeaborwa OM, Terblans JJ, Swart HC (2011) Mater Res Bull 46:987–989 Reuven C (1976) Review Methods for kinetic analysis of thermally stimulated processes. J Mater Sci 11:1521–1541 Sonekar RP, Omanwar SK, Moharil SV, Dhopte SM, Muthal PL, Kondawar VK (2007) Opt Mater 30:622–625 Sonekar RP, Omanwar SK, Moharil SV, Muthal PL, Dhopte SM, Kondawar VK (2009) Luminescence in LaBaB9O16 prepared by combustion synthesis. J Lumin 129:624–628 Sun J, Lian Z, Shen G, Shen D (2013) RSC Adv 3:18395–18398 Thakare DS, Omanwar SK, Moharil SV, Dhopte SM, Muthal PL, Kondawar VK (2007) Opt Mater 29:1731–1735
Environ Sci Pollut Res Wu L, Chen XL, Li XZ, Dai L, Xu YP, Zhao M (2005) Synthesis and ab initio X-ray powder diffraction structure of the new alkali and alkali earth metal borate NaCa(BO3). Acta Crystallogr Sect C 61:i32–i34 Wu L, Chen XL, Li H, He H, Dai L, Li XZ, Xu YP (2004) Structure determination of a new compound LiCaBO3. J Solid State Chem 177:1111–1116
Wu L, Zhang Y, Kong YF, Sun TQ, Xu JJ, Chen XL (2007) structure determination of novel orthoborate NaMgBO3: a promising Birefringent Crystal. Inorg Chem 46:5207–5211 Zhang X, Gong M (2014) Single-phased white-light-emitting NaCaBO3: Ce3+, Tb3+, Mn2+ phosphors for LED applications. Dalton Trans 43: 2465–2472
POLLUTION CONTROL TECHNOLOGIES AND ALTERNATE ENERGY OPTIONS
Synthesis and thermoluminescence properties of rare earth-doped NaMgBO3 phosphor Z. S. Khan 1 & N. B. Ingale 2 & S. K. Omanwar 3
Received: 23 February 2015 / Accepted: 30 June 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Rare earth (Dy3+ and Sm3+)-doped sodium magnesium borate (NaMgBO3) is synthesized by solution combustion synthesis method keeping their thermoluminescence properties in mind. The reaction produced very stable crystalline NaMgBO3:RE (RE=Dy3+, Sm3+) phosphors. The phosphors are exposed to 60Co gamma-ray radiations dose of varying rate from 5 to 25 Gy, and their TL characteristics with kinetic parameters are studied. NaMgBO3:Dy3+ phosphor shows two peaks for lower doping concentration of Dy3+ while it reduced to single peak for the higher concentrations of activator Dy3+. NaMgBO3:Dy3+ shows the major glow peak around 200 °C while NaMgBO 3 :Sm 3+ phosphors show two well-separated glow peaks at 200 and 332 °C respectively. The thermoluminescence intensity of these phosphors was compare with the commercially available TLD-100 (Harshaw) phosphor. The TL responses for gamma-ray radiations dose were found to be linear from 5 to 25 Gy for both phosphors while the fading in each case is calculated for the tenure of 45 days.
Responsible editor: Philippe Garrigues * Z. S. Khan [email protected] 1
Department of Physics, BS Patel College, Pimpalgaon kale 443403, India
2
Prof. Ram Meghe Institute of Technology and Research, Badnera, Amravati 444701, India
3
Department of Physics, SGB Amravati University, Amravati 444602, India
Keywords Thermoluminescence . NaMgBO3 . Solution combustion synthesis method . Rare earths . Kinetic parameters
Introduction Borate phosphors attract the attention of researchers due to their applications in various fields. Borates possess excellent properties as host structures of phosphors in which isolated planer [BO3]3− groups (Nagpure et al. 2011). In borate compounds, boron atom is coordinated by oxygen atoms to form a variety of atomic groups that affect the physical properties in general and optical properties in particular (Wu et al. 2004). The NaMgBO3 phosphor may show such applications due to the presence of isolated planar [BO3]3− group at an appropriate position. Borate compound LiCaBO3: Tb, Dy (Bajaj and Omanwar 2012) find significant applications as TLD phosphor used in personal dosimetry. A variety of BOatomic group are considered to be a dominant factor in their physical properties and a class of phosphors with high-quality performances, especially when doped with proper activators (Nagpure and Omanwar 2012). The main reason of emphasizing on borate is their variety of structure types, transparency to a wide range of wavelengths, high laser damage tolerance, and high optical quality (Bajaj and Omanwar 2013). Combustion synthesis is a good low-cost, one-step, and lowtemperature method for the synthesis of borates, phosphates, and silicates (Khan et al. 2015; Bhatkar et al. 2002; Thakare et al. 2007; Bhatkar et al. 2007; Sonekar et al. 2007; Sonekar et al. 2009). Some orthoborates,
Environ Sci Pollut Res Table 1
Balanced chemical reactions during the combustion method
S.N. Product 1. 2.
Corresponding reaction with balanced molar ratios of precursors
NaMgBO3:Dy3+ NaNO3 +Mg(NO3)2 +H3BO3 +5CO(NH2)2 +7.5 NH4NO3 +x Dy2O3⟶Na Mg1-xBO3 : x Dy3+ + Gaseous (H2O, NH4, NO2, etc.) [x=0.001, 0.002, 0.005, 0.01 and 0.02] NaMgBO3:Sm3+ NaNO3 +Mg(NO3)2 +H3BO3 +5CO(NH2)2 +7.5 NH4NO3 +x Sm2O3⟶NaMg1-xBO3 : x Sm3+ + Gaseous (H2O, NH4, NO2, etc.) [x=0.001, 0.002, 0.005, 0.01 and 0.02]
LiMgBO3:Dy3+ (Bajaj and Omanwar 2014), NaCaBO3 (Wu et al. 2005), LiCaBO 3 (Anishia et al. 2010), LiSrBO3 (Cheng et al. 2001), LiBaBO3 (Cheng et al. 2001), NaBaBO3 (Kononova et al. 2003), N a S r B O 3 : T b 3 + ( N a g p ur e a n d O m a n w a r 2 01 2 ) , LiSrBO 3 :Sm 3+ (Pitale et al. 2011), NaSrBO 3 :Sm 3+ (Kumar et al. 2013), NaCaBO 3 : Ce 3+ , Mn 2+ (Sun et al. 2013), NaCaBO3:Ce3+, Tb3+, Mn2+ (Zhang and Gong 2014), NaCaBO3:Sm3+ (Bedyal et al. 2014), etc., have been synthesized with different methods to explore their crystal structure and luminescent properties for probable applications in medical as well as industrial fields. Recently, Wu et al. (2007) effectively synthesized NaMgBO 3 by solid-state reaction and explained the structure of NaMgBO3 which is somewhat similar to that of NaSrBO3 orthoborates. In this paper, we describe synthesis and characteristics of NaMgBO 3:RE (RE = Dy3+ and Sm3+) using the solution combustion synthesis method. The prepared materials are considered for its TLD properties under gamma-ray exposure with the impacts of rare earth (RE) activators on it.
Fig. 1 XRD pattern for NaMgBO3 Host
Experimental The NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphors are prepared by well-established solution combustion synthesis method (Bhatkar et al. 2002; Thakare et al. 2007; Bhatkar et al. 2007; Sonekar et al. 2007; Sonekar et al. 2009; Bajaj and Omanwar 2014; Wu et al. 2005). During the reaction, the stoichiometric amounts of high purity starting components, NaNO3 (G.R.), Mg (NO3)2·4H2O (Analytical Reagent), H3BO3 (A.R.), CO (NH2)2 (G.R.), NH4NO3 (G.R.), Dy2O3, and Sm2O3 (activators) are calculated on the basis of molar ratio (using oxidizer/fuel ratio) and are thoroughly mixed in the agate mortar by adding little amount of double distilled water and an aqueous homogeneous solution was obtained. Ammonium nitrate is nothing but the oxidizer which is used for combustion along with the fuel (here urea) in the reaction. The solution was then transferred into a China basin. The China basin was then kept into preheated muffle furnace maintained at (550±10 °C). The solution boils, foams, and ignites to burn with the flame, and a voluminous, foamy powder was obtained. The entire combustion was
Environ Sci Pollut Res
Fig. 2 SEM image of a NaMgBO3:Dy3+ and b NaMgBO3:Sm3+
over within 5 min. Following the combustion, the resulting fine powder was annealed in open air at 750 °C for 90 min and allowed to cool down at room temperature. The prepared sample was confirmed by Rigaku Miniflex X-Ray Diffractometer with scan speed of 2.00°/min and with Cu Kα radiation (λ= 1.5406 Å). Scanning electron microscope (SEM) images were taken from Synthetic and Art Silk Mills Research Association (SASMIRA), Mumbai. Irradiations with 60Co gamma-rays source was utilized from RTM Nagpur University while Thermoluminescence (TL) glow curves were recorded with the help Fig. 3 TL glow curve NaMgBO3: RE (RE=Dy3+, Sm3+) compared with commercial phosphor TLD-100H
of TL 1009I reader designed and offered by Nucleonix system with constant heating rate of 5 °C/s (Table 1).
Results and discussion XRD analysis Figure 1 represents the X-ray diffraction (XRD) pattern for the NaMgBO3 synthesized by solution combustion
Environ Sci Pollut Res Fig. 4 Deconvoluted curves from experimental curve for NaMgBO3:Dy3+
synthesis method which is in good agreement with the International Centre for Diffraction Data (ICDD) file 00059-0808. The sharp peaks in the XRD patterns also confirm the highly crystalline nature of prepared sample. All the main peaks favor the confirmation of the desired phosphor.
NaMgBO 3:Sm 3+ phosphor. The combustion synthesis method does not guaranteed the nanostructure of the prepared sample. It shows the moist particles with an irregular shapes and the range of particle size 1– 5 μm. TL glow curve
Morphology Figure 2 represents the SEM image showing morphology of as synthesized (a) NaMgBO 3 :Dy 3+ and (b)
Fig. 5 Deconvoluted curves from experimental curve for NaMgBO3:Sm3+
The TL glow curve of NaMgBO3 with different concentration of Dy3+ and Sm3+ for a test dose of 15 Gy is shown in Fig. 3 obtained at heating rate 5 °C/s. For
Environ Sci Pollut Res Table 2 Phosphor
Kinetic parameters for NaMgBO3:Dy3+ and NaMgBO3:Sm3+ Peak
NaMgBO3:Dy3+ Main peak High temperature peak 3+ NaMgBO3:Sm Main peak High temperature peak
E(eV) S(s−1) 0.659 1.505 0.864 1.38
8.76×105 1.75×1012 3.53×108 6.68×1010
Tm(°C) 219 317 200 332
NaMgBO3:Dy3+, the glow curve consists of two peaks nearly at 219 and 317 °C while for NaMgBO3:Sm3+, the glow curve consists of two peaks about 200 and 332 °C. The main aspect for TLD material is that for dosimetry purpose, it is desirable for the detector to have glow curve peak around 200–250 °C, which is partially filled by this phosphor at least for the first peak. This temperature range ensures that the trap depth is large enough without appreciable trap emptying at normal temperatures (Bajaj and Omanwar 2012; Koparkar et al. 2013). Also, this temperature range is low enough such that the interference due to black body radiation signal is negligible. Hence, it increases the interest of further studies on NaMgBO3. Thermoluminescence glow curve of NaMgBO 3:RE (RE = Dy3+ and Sm3+) prepared with solution combustion method was compared with the TL glow curve obtained from standard LiF:MCP under same dose conditions. TL intensity of main peak of our NaMgBO 3 :Dy 3+ phosphor is about 95 % intense as compared to that of LiF:MCP, while the intensity of main peak of NaMgBO 3 :Sm 3+ phosphor is about 50 % intense as that of LiF:MCP. Glow curve structure is confirmed by deconvolution of peak by using peak fit software (Bajaj and Omanwar 2013); the obtained
Fig. 6 Dose linearity of glow peak intensity in NaMgBO3:RE (RE=Dy3+ and Sm3+)
Fig. 7 Effect of doping concentration on NaMgBO3:Dy3+
peaks are simple and symmetric for both the phosphors NaMgBO 3 :RE (RE = Dy 3+ and Sm 3+ ) as shown in Figs. 4 and 5. Kinetic studies The TL glow curves for NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphors were deconvoluted by using the Peak Fit software as shown in Figs. 4 and 5, respectively. We employed the Chen’s peak shape method (Chen Reuven 1976) to analyze the activation energy of both NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphors by the method mentioned by Mckeever (1993) using Eq. (1): E ¼ cγ kT m2 =γ −bγ ð2kT m Þ ð1Þ where γ stands for τ, δ, or ω. The values of τ, δ, and ω are, respectively, determined by low-temperature halfwidth (τ = Tm –T1), high-temperature half-width (δ =T2–
Environ Sci Pollut Res Fig. 8 Effect of doping concentration on NaMgBO3:Sm3+
Tm), and full width (ω=T2 –T1). For first-order kinetics, the values of the cγ and bγ depending on τ, δ, or ω (Mckeever 1993) and k is Boltzmann constant. To analyze the frequency factor s of the glow curve values, the activation energy obtained from Eq. (1) and heating rate (β) at which the glow curves are recorded were used in Eq. (2). βE= kT m2 ¼ se½−E=kT m
ð2Þ
The summaries of calculated results are represented in Table 2.
Dose response The TL material is said to be good when its response to absorbed dose is linear over the wide range. To study the linearity, five samples were irradiated simultaneously for each level of dose. Each data point corresponds to the mean of the five readings. The linearity was observed in the range from 5 to 25 Gy as shown in Fig. 6. The relationship between the TL response of first peak and the absorbed dose for NaMgBO3:Dy3+ and NaMgBO 3 :Sm 3+ phosphor is shown in Fig. 6 which is found to be linear. The role played by dysprosium (Dy3+) activator is to enhance the energy in Fig. 9 Fading Effect of NaMgBO3:Dy3+ phosphor
NaMgBO 3 host as compared to samarium (Sm3+) as shown in Fig. 6. Effect of dopant concentrations Concentration of Dy3+ and Sm3+ in host was selected as per formula NaMg1−x BO3:REx (RE = Dy3+ and Sm3+) and varied from 0.1 mol to 2 mol%. It was observed that RE concentration has significant impact on the peak height of main as well as higher temperature glow peak. With increasing the concentration of RE (Dy 3+ and Sm3+), TL intensity of main glow peak, i.e., 219 °C as well as 200 °C respectively in NaMgBO3:Dy3+ and NaMgBO3:Sm3+, increases. The optimum concentration of RE in NaMgBO3:Dy3+ was found to be 0.005 mol of Dy 3+ while for NaMgBO 3 :Sm 3+ , it was 0.1 mol of Sm3+. In other words, on further increase of concentration, peak height decreases suddenly which is considered as concentration quenching of RE in NaMgBO3:RE in each case. Figures 7 and 8 show the variation of TL intensity with RE concentration. Fading effect While operating in the desired environment, stability of the material should be unaffected for the undesired sig-
Environ Sci Pollut Res Fig. 10 Fading Effect of NaMgBO3:Sm3+ phosphor
nals. Hence, fading effect is essential to check for particular duration of time regarding specially for optical signals. The loss in TL before readout may occur due to heat or light or any other means with respect to time. A dosimeter which is continuously exposed to sunlight or fluorescent lamp may lose part of its TL signal by optical stimulation. For dosimetry applications, the phosphor should be free from such optical effects. Hence, five samples of same dose were irradiated simultaneously. Each data point corresponds to the mean of the five readings. The TL material NaMgBO3:RE (RE= Dy3+ and Sm3+) shows linear intensity of glow peak up to 45 days and there was constancy found in results. The overall fading found in intensity was 5 % over the period 45 days; also the nature of each TL peak remained the same which supports the storage of sample not affecting the defects in crystallites. The fading effect in NaMgBO3:RE (RE=Dy3+ and Sm3+) was represented in Figs. 9 and 10 respectively.
Conclusion We synthesized NaMgBO3:RE (RE = Dy3+ and Sm3+) phosphors by one-step, low-cost, and low-temperature solution combustion method. TL characteristics and some dosimetric properties of Dy3+ and Sm3+ activated NaMgBO 3 phosphor were investigated in detail. The trap parameters, i.e., activation energy and frequency factor of the TL glow curve of the sample, were calculated by peak shape method. The so-prepared phosphor NaMgBO3 host shows impact of rare earth activators on it intensity (energy). NaMgBO 3 :Dy 3 + leads with NaMgBO3:Sm3+ in terms of energy. The TL and dosimetric characteristics implied the potential of NaMgBO3:Dy3+ and NaMgBO3:Sm3+ phosphor as γray TL materials in the personal protection dosimetry field and radiation dosimetry Acknowledgments ZSK is grateful to the UGC-New Delhi, for financial support, and to the Head, Department of Physics, SGB Amravati University, for providing necessary facilities
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