Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds

Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds

Thermoluminescence of undoped and doped CaB₄O₇ with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaB₄O₇ are prepared by melting method. The formation of CaB₄O₇ compound is checked by X-ray diffraction study and the compound is found to have ort...

Повний опис

Збережено в:
Бібліографічні деталі
Дата:2003
Автори: Manam, J., Sharma, S.K.
Формат: Стаття
Мова:English
Опубліковано: Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України 2003
Назва видання:Semiconductor Physics Quantum Electronics & Optoelectronics
Онлайн доступ:http://dspace.nbuv.gov.ua/handle/123456789/118092
Теги: Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
Назва журналу:Digital Library of Periodicals of National Academy of Sciences of Ukraine
Цитувати:Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds / J. Manam, S.K. Sharma // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2003. — Т. 6, № 4. — С. 465-470. — Бібліогр.: 10 назв. — англ.

Репозитарії

Digital Library of Periodicals of National Academy of Sciences of Ukraine
id irk-123456789-118092
record_format dspace
spelling irk-123456789-1180922017-05-29T03:05:07Z Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds Manam, J. Sharma, S.K. Thermoluminescence of undoped and doped CaB₄O₇ with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaB₄O₇ are prepared by melting method. The formation of CaB₄O₇ compound is checked by X-ray diffraction study and the compound is found to have orthorhombic structure at room temperature. The TSL studies of undoped CaB₄O₇ sample shows two glow peaks at 150°C and 265°C and one shoulder at around 190°C. The TSL studies of Cu doped CaB₄O₇ sample also shows two glow peaks at 160°C and 270°C and a shoulder at around 230°C whereas the TSL glow curves of Mn doped CaB₄O₇ has only one single strong glow peak at 135°C. A comparative TSL studies of these compounds shows that CaB₄O₇ compound doped with Mn is the most sensitive and the TSL intensity is enhanced by about 40 times when compared with the TSL intensity of undoped CaB₄O₇ compound. The trap parameters namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the 135°C glow peak of CaB₄O₇: Mn phosphor are determined using isothermal decay and glow curve shape (Chen's) methods. 2003 Article Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds / J. Manam, S.K. Sharma // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2003. — Т. 6, № 4. — С. 465-470. — Бібліогр.: 10 назв. — англ. 1560-8034 PACS: 78.60.Kn, 61.10.Nz http://dspace.nbuv.gov.ua/handle/123456789/118092 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description Thermoluminescence of undoped and doped CaB₄O₇ with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaB₄O₇ are prepared by melting method. The formation of CaB₄O₇ compound is checked by X-ray diffraction study and the compound is found to have orthorhombic structure at room temperature. The TSL studies of undoped CaB₄O₇ sample shows two glow peaks at 150°C and 265°C and one shoulder at around 190°C. The TSL studies of Cu doped CaB₄O₇ sample also shows two glow peaks at 160°C and 270°C and a shoulder at around 230°C whereas the TSL glow curves of Mn doped CaB₄O₇ has only one single strong glow peak at 135°C. A comparative TSL studies of these compounds shows that CaB₄O₇ compound doped with Mn is the most sensitive and the TSL intensity is enhanced by about 40 times when compared with the TSL intensity of undoped CaB₄O₇ compound. The trap parameters namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the 135°C glow peak of CaB₄O₇: Mn phosphor are determined using isothermal decay and glow curve shape (Chen's) methods.
format Article
author Manam, J.
Sharma, S.K.
spellingShingle Manam, J.
Sharma, S.K.
Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds
Semiconductor Physics Quantum Electronics & Optoelectronics
author_facet Manam, J.
Sharma, S.K.
author_sort Manam, J.
title Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds
title_short Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds
title_full Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds
title_fullStr Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds
title_full_unstemmed Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds
title_sort thermally stimulated luminescence studies of undoped and doped cab₄o₇ compounds
publisher Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
publishDate 2003
url http://dspace.nbuv.gov.ua/handle/123456789/118092
citation_txt Thermally stimulated luminescence studies of undoped and doped CaB₄O₇ compounds / J. Manam, S.K. Sharma // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2003. — Т. 6, № 4. — С. 465-470. — Бібліогр.: 10 назв. — англ.
series Semiconductor Physics Quantum Electronics & Optoelectronics
work_keys_str_mv AT manamj thermallystimulatedluminescencestudiesofundopedanddopedcab4o7compounds
AT sharmask thermallystimulatedluminescencestudiesofundopedanddopedcab4o7compounds
first_indexed 2025-07-08T13:21:10Z
last_indexed 2025-07-08T13:21:10Z
_version_ 1837085095557595136
fulltext 465© 2003, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine Semiconductor Physics, Quantum Electronics & Optoelectronics. 2003. V. 6, N 4. P. 465-470. PACS: 78.60.Kn, 61.10.Nz Thermally stimulated luminescence studies of undoped and doped CaB4O7 compounds J. Manam*, S.K. Sharma Department of Applied Physics, Indian School of Mines, Dhanbad-826004, India *Corresponding author: Phone: +91 326 2202671, Fax: +91 326 2210028, E-mail: jairam_manam@yahoo.co.in Abstract. Thermoluminescence of undoped and doped CaB4O7 with activators such as Cu and Mn has been investigated. The polycrystalline samples of undoped and doped CaB4O7 are prepared by melting method. The formation of CaB4O7 compound is checked by X-ray dif- fraction study and the compound is found to have orthorhombic structure at room tempera- ture. The TSL studies of undoped CaB4O7 sample shows two glow peaks at 150°C and 265°C and one shoulder at around 190°C. The TSL studies of Cu doped CaB4O7 sample also shows two glow peaks at 160°C and 270°C and a shoulder at around 230°C whereas the TSL glow curves of Mn doped CaB4O7 has only one single strong glow peak at 135°C. A comparative TSL studies of these compounds shows that CaB4O7 compound doped with Mn is the most sensitive and the TSL intensity is enhanced by about 40 times when compared with the TSL intensity of undoped CaB4O7 compound. The trap parameters namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the 135°C glow peak of CaB4O7: Mn phosphor are determined using isothermal decay and glow curve shape (Chen�s) methods. Keywords: Calcium borate, X-ray diffraction, thermally stimulated luminescence, trap pa- rameters. Paper received 08.09.03; accepted for publication 11.12.03. 1. Introduction Phosphors prepared from inorganic compounds by dop- ing with suitable activator and coactivator impurities are generally polycrystalline which are capable of convert- ing one or more forms of energy into radiation in or close to the visible region of the electromagnetic spectrum. These phosphors find many industrial applications in the manufacture of TV/CRO screens, fluorescent lamps, EL panels, visible light emitting diodes, X-ray imaging, IR sensors, radiation dosimetry, luminescence paints etc. In recent years, significant progress has been made in the development of new materials for radiation dosimetry. These include alkali and alkaline earth tetra borates [1,2]. The following work is undertaken to study the TL mecha- nism in undoped and doped calcium borate compounds. Thermoluminescence in irradiated sintered CaB4O7 con- taining activators such as Cu, Pb, Eu or Dy has been first investigated by Fukuda et al [3,4,5]. As the TL glow curves often depend on the activators so it seems interesting to investigate further the effects of other activator such as Mn on the TSL output of polycrystalline CaB4O7 com- pound. 2. Experimental details The polycrystalline samples of undoped and doped CaB4O7 were prepared by melting method [6]. The prepa- ration of calcium borate sample has been made by mix- ing calcium carbonate (99%,Loba Chemie, Bombay) and boric acid (99.5%, s.d. fine-chem Ltd., Boisar ) in stoi- chiometric ratio and the mixture is melted at 900ºC in a platinum crucible for 4.5 hours and then cooled at a rate of about 60 K/min. The crystalline material was ground and sieved to a grain size of 200µm. Doped CaB4O7 sam- ples are prepared in a similar manner by taking the start- ing material in stoichiometric ratio and adding 0.5 wt% of CuCl2 ( 98%, Loba Chemie, Bombay) or MnCl2 (99.5%, s.d. fine-chem Ltd.,Boisar ) in the mixture. The characterization of CaB4O7 is carried out by X- ray diffraction study. X-ray diffractogram of the com- pound is taken at room temperature in a wide range of Bragg angle 2θ (10º ≤ 2θ ≤ 80º) using a X-ray diffrac- tometer type PW 1710, Holland with Cu target and at a scanning rate of 3º/min. All samples were heated to 400ºC for 10 minutes and then quenched to room temperature before X-irradiating 466 SQO, 6(4), 2003 J. Manam, S.K. Sharma: Thermally stimulated luminescence studies of undoped ... them. The powder samples were irradiated by X-rays obtained from Cu target of Machlett tube operated at 20 kV and 15 mA. The TSL studies were made by using Personal Computer Based Thermoluminescence Analyzer System (type 1007) supplied by Nucleonix Systems Pri- vate Limited, Hyderabad, India. The glow curves were recorded by heating the samples at a uniform rate of 4ºC/s with the help of a temperature controller (type 575) made by Nucleonix Systems Private Limited, Hyderabad, In- dia and the luminescence emission was detected by a photo-multiplier tube (type 9924 B) imported from U.K. The photo-current from PM tube is amplified by a DC amplifier (type 552) made by Nucleonix Systems Private Limited, Hyderabad, India which is interfaced to a per- sonal computer. The T S L out put is finally recorded by a printer connected to the personal computer. 3. Results and discussion 3.1 Structural study In order to ascertain the structure of prepared CaB4O7 compound, X-ray diffraction pattern of powder sample CaB4O7 is recorded (Fig. 1). The sharp and single dif- fraction peaks of the XRD pattern suggested the forma- tion of new compound. From the 2θ values of the diffrac- tion lines, interplanar spacing (d) of the peaks was calcu- lated. The diffraction lines were indexed using a compu- ter program package �Powdmult� [7,8]. Out of those a suitable orthorhombic unit cell was selected for which Σ∆d ( = dobs � dcal) was found to be minimum. The lattice parameters of the unit cell were refined using least-squares method and were found to be: a = 27.9159Å, b = 3.4790Å, c = 6.4198Å. A good agreement between the observed and calculated d-values (Table 1) suggests the suitability of the crystal structure and unit cell parameters. 1200 1000 800 600 400 200 0 10 20 30 40 50 60 70 80 CaB In te n si ty , a rb . u n it s Bragg angle, 2q Fig. 1. XRD pattern of CaB4O7 sample at room temperature. 3.2 TSL study Under this study, glow curves of undoped, Cu and Mn doped CaB4O7 samples are recorded for the different time of X-irradiation. The TSL glow curves of CaB4O7 powder samples are recorded by X-irradiating at room temperature for 1, 2, 4 and 10 minutes (Fig. 2). The room temperature X-irra- diated CaB4O7 sample exhibit two glow peaks at tem- peratures 150 and 265ºC and one shoulder at around 190ºC and the intensity of 150ºC glow peak is the stronger. Moreover the intensities of the glow peaks are found to increase with increase of the X-ray dose. The TSL glow curves of Cu-doped CaB4O7 powder sample are recorded by X-irradiating at room temperature for 1, 3 and 5 minutes (Fig. 3). The T S L glow curves of X- irradiated CaB4O7 : Cu exhibit two glow peaks at 160 and 270ºC and one shoulder at around 230ºC and the intensity of 160ºC glow peak is the higher. In this case also the intensities of glow peaks are found to increase with the increase of X-ray dose. The TSL glow curves of Mn doped CaB4O7 powder sample are recorded by X- irradiating at room temperature for 10,20,30,45 and 60 seconds (Fig. 4). The TSL glow curves of X-irradiated CaB4O7 : Mn exhibit only one strong TL glow peak at the temperature of 135ºC. It is observed that in this case also, the glow peaks grow in intensities with the increase of X-ray dose. The TL glow curves of both undoped and Cu doped CaB4O7 compounds shows two glow peaks indicating that two different species of traps are being activated within the particular temperature range each with its own value Table 1. Comparison of observed and calculated d-values (Å) of some reflections of CaB4O7 sample at room temperature.  h k l dobs  dcal  I/I0*100  1 1 0 3.4531 3.4522 44  0 2 0 1.7399 1.7395 19  0 0 4 1.6053 1.6050 25  8 2 0 1.5559 1.5568  100  3 2 2 1.5100 1.5091 14 19 0 1 1.4308 1.4302 16  7 1 4 1.3680 1.3688 15 11 2 3 1.1919 1.1971  9  0 3 1 1.1411 1.1412 14  4 0 6 1.0575 1.0576 15 14 2 4 1.0153 1.0151 15 27 1 2 0.9469 0.9470  6 30 1 0 0.8989 0.8989  5 28 1 3 0.8747 0.8747 12 J. Manam, S.K. Sharma: Thermally stimulated luminescence studies of undoped ... 467SQO, 6(4), 2003 of activation energy (E) and frequency factor (s). Com- parison of intensities of glow peaks (Fig. 5) shows that addition of Cu impurity to undoped CaB4O7 enhance the TL intensity by a very small amount. The Mn doped CaB4O7 compound shows only one single strong TL glow peak indicating that only one spe- cies of traps are being activated at a particular tempera- ture with its activation energy (E) and frequency factor (s). Moreover this glow peak is observed at some low tem- perature compared to undoped and Cu doped CaB4O7 compounds. Comparison of intensity of glow peak (Fig. 5) in Mn doped CaB4O7 compound shows that addition of Mn impurity to undoped CaB4O7 compound enhances the TL intensity by about 40 times. It has been suggested that glow peak observed at 135ºC in CaB4O7 : Mn is peculiar to Mn activator and is related to the relaxation of the excited Mn++ ions. Upon irradiation, Mn++ ions capture one or two electrons to become Mn+ or Mn0. Mn++ + electron → Mn+ Mn++ + 2 electron → Mn0 T L i n te n si ty a rb . u n it s 0 50 100 150 200 250 300 350 400 2048 1792 1536 1280 1024 768 512 256 0 a � 10 s b � 20 s a b c e � 60 s Temperature, C° Fig. 4. TSL glow curves of CaB4O7:Mn sample for different times of X-irradiation. T L i n te n si ty a rb . u n it s 0 50 100 150 200 250 300 350 400 2048 1792 1536 1280 1024 768 512 256 0 a � CaB O b � CaB O : Cu a b c Temperature, C° 4 4 4 7 7 7 Fig. 5. Comparative TSL glow curves of undoped Cu and Mn doped culcium borate samples. Fig. 2. TSL glow curves of CaB4O7 sample for different times of X-irradiation. T L i n te n si ty , a rb . u n it s 0 50 100 150 200 250 300 350 400 2048 1792 1536 1280 1024 768 512 256 0 a � 1 min a b c c � 5 min Temperature, C° Fig. 3. TSL Glow curves of CaB4O7: Cu sample for different times of X-irradiation. 1536 1280 1024 768 512 256 0 0 50 100 150 200 250 300 350 400 T L i n te n si ty , a rb . u n it s Temperature, C° a � 1 mina � 1 min a b c d b � 2 min c � 4 min d � 10 min 468 SQO, 6(4), 2003 J. Manam, S.K. Sharma: Thermally stimulated luminescence studies of undoped ... On thermal stimulation, Mn+ ions give rise to TSL emission according to the following mechanism: Mn+ + hole → (Mn++)* → Mn++ + hν. Whereas in case of Mn0 atoms, thermal stimulation gives rise to TSL emission according to the following mechanism: Mn0 + 2 hole → (Mn++)* → Mn++ + hν The increase in the intensities of the glow curves with increase of irradiation dose can be understood by the fact that more and more traps responsible for these glow peaks were getting filled with the increase of irradiation dose and subsequently these traps release the charge car- riers on thermal stimulation to finally recombine with their counterparts, thus giving rise to different glow peaks. 3.3 Trap parameters Trap parameters such as order of kinetics (b), activation energy (E) and frequency factor (s) are calculated for the 135°C glow peak of CaB4O7 : Mn phosphor using the isothermal luminescence decay method (ILDM). The theory and experimental details of the method is described elsewhere [9]. As a check the trap parameters are also calculated by the glow curve shape (Chen�s) method. 3.3.1. Isothermal luminescence decay method The isothermal luminescence decay method is based on recording the decay of luminescence intensity with re- spect to time at a constant temperature. Three tempera- tures are chosen on the rising side of the glow peak whose trapping parameters are to be determined. After irradiat- ing the sample by X-ray or γ-ray of suitable dose, it is heated to one of the chosen temperatures and decay of luminescence intensity is recorded at a constant tempera- ture. This procedure is repeated for other two tempera- tures. The experimental data is tested for finding the or- der of kinetics. First order kinetics TL intensity equation for the first order kinetics is [9]:      −=    −= kT E sn dt dn I exp . The solution of intensity equation for the isothermal case : ( )            −−    −= kT E ts kT E sntI expexpexp0 or, ( )[ ] ( )     −+          −−= kT E sn t kT E stI 0lnexpln (1) So for the first order case, plot of ln[I(t)] vs time should yield a straight line. The slope of this straight line is:    −= kT E sm exp or, ( )[ ] ( )s kT E Tm lnln +−= (2) The slope (m) of straight line plots of ln[I(t)] vs time at different temperatures are noted and again ln[m(T)] vs 1/T are plotted which is a straight line (equ.2). The slope m′ = �E/k of this straight line give thermal activation energy (E) where k is the Boltzman�s constant and inter- cept part ln(s) of equation (2) gives the value of frequency factor (s). General order kinetics TL intensity equation for the general order kinetics is:     −′=    −= kT E ns dt dn I b exp , where 1 0 − =′ bn s s is the pre-exponential factor. The solution of intensity equation for the isothermal case [10]: ( )tb kT E s I I b b 1exp1 1 0 −   −=−    − , (3) so for the general order case, plot of (I0/I)(b�1)/b �1 vs time should yield a straight line where b is the order of kinet- ics (1< b ≤ 2), I0 is the intensity at t = 0 and I is the intensity at any instant t. The experimental data is tested by choosing different test values of b, among which the value of b that gives the best fit as straight line gives the order of kinetics (b). The slope of this straight line equation (3) is: ( )    −−= kT E sbm exp1 . (4) The determination of slope (m) of straight line plots of (I0/I)(b�1)/b �1 vs time at different temperatures will give the value of frequency factor according to the relation : ( ) ( )( ) 12 1 12 2 1 2 1 TT T TT T mb m s − − − = , (5) where m1 and m2 are the slopes corresponding to the tem- peratures T1 and T2 respectively. From equation (4) : ( )[ ] ( )[ ]1lnln −+−= bs kT E Tm . (6) J. Manam, S.K. Sharma: Thermally stimulated luminescence studies of undoped ... 469SQO, 6(4), 2003 Now to find the thermal activation energy (E) a graph ln[m(T)] vs 1/T is plotted, which is a straight line (equa- tion 6). The slope m′ = �E/k of this straight line graph will give the value of thermal activation energy (E). In order to calculate the trapping parameters corre- sponding to 135°C glow peak, three temperatures namely 120, 125 and 130°C were chosen and decay of lumines- cence intensity with time at these temperatures were re- corded by X-irradiating the sample for 1 minute. The plots of lnI vs time were drawn at these temperatures which do not fit into the straight line nature which establish that the glow peak at 135°C does not obey first order kinetics. This indicates that TSL mechanism at this temperature is not associated with first order kinetics. Then plots of (I0/I)(b�1)/b � 1 vs time were drawn for different values of b (1< b ≤ 2). The best straight line fitting is obtained for b = 2 as shown in Fig. 6. This established that 135°C glow peak is associated with second order kinetics. The value of frequency factor (s) is found from the slope of these straight lines at 120 and 125°C by using the equa- tion (5) and is found to be 4.68×109 sec�1. To find the thermal activation energy (E), the slope (m) of these straight lines for the temperatures 120, 125 and 130°C were noted and were plotted as ln(m)vs 1/T as shown in Fig. 7 which is a straight line as expected. The activa- tion energy (E) is calculated from the slope ( m′ = �E/k) of this straight line and is found to be 0.82 eV. 3.3.2 Glow curve shape method The method based on the shape of glow curve proposed by Chen was used to verify the above calculated trapping parameters. To determine these parameters the follow- ing shape parameters are determined: the total half in- tensity width (ω = T2 � T1 ), the high temp. half width (δ = T2 � Tm), the low temp. half width (τ = Tm� T1), where Tm is the peak temperature and T1 and T2 are temp. on either side of Tm corresponding to half peak intensity. Order of kinetics : Order of kinetics (b) is determined by calculating the symmetry factor (µg) of the glow peak from the known values of shape parameters : 12 2 TT TT ù ä ì m g − − == . (7) The shape factor (µg) for the 135°C glow peak of CaB4O7 : Mn is found to be 0.52 which suggest that this peak obey second order kinetics. Activation energy : Activation energy (E) is calculated by using the Chen�s equations which gives the trap depth in terms of τ, δ, ω. A general formula for E was given by : m mã Tkb ã kTc E 2 2 γ−= , (8) where γ is τ, δ or ω. The constants cγ and bγ for the three equations (τ, δ and ω) and for second order kinetics are Cτ = 1.81, bτ = 2.0, Cδ = 1.71, bδ = 0, Cω = 3.54, bω = 1.0. The activation energy for the 135°C glow peak of CaB4O7 : Mn when calculated by equation (8) using low temp. half width, high temp. half width and full width of the peak at its half height are found to be 0.81 eV, 0.83 eV and 0.82 eV giving mean value of activation energy 0.82 eV. Frequency factor : Once order of kinetics and activation energy are de- termined, the frequency factor (s) can be calculated by the equation given by Chen & Winer : ( )     −      −+= m m m kT E E kT bs kT qE exp 2 11 2 (9) where q is the heating rate. The frequency factor for the 135°C glow peak of CaB4O7 : Mn when calculated by using equation (9) is found to be 2.96×109sec�1. Table 2 gives the values of trapping parameters of the 135°C glow peak of CaB4O7 : Mn phosphor calculated by isothermal decay and Chen�s methods. The results shows a very good agreement between the trapping parameters calculated by the two methods and indicates 0 0.5 1 1.5 2 2.5 3 3.5 0 10 20 30 40 50 60 70 T im e, s 0 T = 12 0 C T = 12 5 C T = 13 0 C [( / ) I I � 1 ] 1/ 2 Fig. 6. Isothermal luminescence decay curves of CaB4O7:Mn sample for 135°C glow peak. �4 �3 �2 �1 0 2.46 2.48 2.5 2.52 2.54 2.56 ln [m (T )] (1 /T ) 1 0× 3 K – 1 Fig. 7. Plot of ln[m(T)] vs 1/T for 135°C glow peak of CaB4O7 : Mn sample. 470 SQO, 6(4), 2003 J. Manam, S.K. Sharma: Thermally stimulated luminescence studies of undoped ... the reliability of two methods and accuracy of the meas- urement of parameters. 4. Conclusions (i) The compound CaB4O7 has orthorhombic struc- ture at room temperature. (ii) The addition of Mn impurity to undoped CaB4O7 enhances the TL intensity by about 40 times. (iii) The 135°C glow peak of CaB4O7 : Mn phosphor is due to the second order kinetics with the activation energy 0.82 eV and frequency factor 4.68×109 s�1 . Table 2. Trap parameters of 135°C glow peak of CaB4O7 : Mn phosphor. Trap parameters Method Isothermal Chen�s decay Order of kinetics  2 2 Activation energy (E) in eV 0.82 0.82 Frequency factor (s) in s�1   4.68×109 2.96×109 References 1. J. Manam, A.K. Singh and S.K. Sharma, Thermally stimula- ted luminescence studies of undoped, Cu and Mn doped lithium borate compounds // Ind. J. Phys., 76A (6) pp. 549- 552 (2002). 2. J. Manam and S.K. Sharma, Thermally stimulated lumines- cence studies of undoped, Cu and Mn doped magnesium borate compounds // Asian J. Phys. 12(4) (2003) (In Press). 3. Y. Fukuda, A. Tomita and N. Takeuchi, Thermoluminescence and thermally stimulated exoelectron emission in glass and sintered CaB4O7 : Cucl2 // Phys. Stat. Sol.(a) 85, pp. K141- K144 (1984). 4. Y. Fukuda, A. Tomita and N. Takeuchi, Thermoluminescence and thermally stimulated exoelectron emission of sintered CaB4O7 doped with Pb, Eu or Dy // Phys. Stat. Sol.(a) 99 pp. K135-K138 (1987). 5. Y. Fukuda, K. Mizuguchi and N. Takeuchi, Thermolumines- cence in sintered CaB4O7 : Dy and CaB4O7 : Eu // Radiat. Prot. Dosim. 17 pp. 397-401 (1986). 6. J. Azorin, C. Furetta and A. Scacco, Preparation and prop- erties of thermoluminescent materials // Phys. Stat. Sol. (a) 138 pp. 9-46 (1993). 7. R.N.P. Choudhary, R. Palai and S. Sharma, Structural, di- electric and electrical properties of lead cadmium tungstate ceramics // Mater. Sci. and Engg. B77, pp. 235-240 (2000). 8. T. Kar and R.N.P. Choudhary, Structural, dielectric and electrical conducting properties of KB�B��O6 (B� = Nb,Ta; B�� = W, Mo) ceramics // J. of Phys. & Chem. of Solids 62 pp. 1149-1161 (2001). 9. R. Chen and S.W.S. McKeever, Theory of Thermolumines- cence and Related Phenomena, World Scientific, Singapore (1997). 10. J. Manam, Variation of order of kinetics with dose of X- irradiation in LiF single crystals // Ind. J. Phys. 68A (1) pp. 105-112 (1994).

Схожі ресурси