Indian Journal of

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VOLUME 16

NUMBER 3

JUNE 2009

CODEN : IEMSEW

ISSN : 0971-4588

 

Special Issue

on

Luminescence and its Applications

 

 

CONTENTS

 

 

Preface

 

        Vikram Kumar & Harish Chander

143

 

 

Papers

 

 

 

New highly efficient green phosphor for LEDs

147

        Mihail Nazarov, Boris Tsukerblat & Do Young Noh

 

 

 

POSL studies on indigenously developed α-Al2O3:C

151

        M S Kulkarni, D R Mishra, K P Muthe, S K Gupta & D N Sharma

 

 

 

Delayed optically stimulated luminescence of Al2O3:Si,Ti phosphor

154

        P S Page, B C Bhatt, N S Rawat, D R Mishra & M S Kulkarni

 

 

 

Electroluminescence of CdS nanoparticles-polyvinyl carbazole composites

157

        Pooja Chouksey, B P Chandra & M Ramrakhiani

 

 

 

Swift heavy ion induced thermoluminescence studies in polycrystalline

161

aluminum oxide

 

        K R Nagabhushana, B N Lakshminarasappa , D Revannasiddaiah,

        D Haranath & Fouran Singh

 

 

 

Synthesis and thermoluminescence studies of Sr4Al14O25:Eu2+  phosphor

165

        Suchinder Sharma, Shreyas Pitale, M M Malik, R N Dubey ,

        M S Qureshi , S K Vasisth & P Pathak

 

 

 

Thermoluminescence dosimetric study of X-ray irradiated BAM:Eu

169

        K V R Murthy, A S Sai Prasad, B Subba Rao & Louis Rey

 

 

 

Energy response study of thermoluminescent dosimeters to synchrotron  radiation in the energy range 10-35 keV

172

        A K Bakshi, B S Dhabekar, S Chatterjee , V J Joshi & R K Kher

 

 

 

Preparation of Eu3+ doped Y2O3 and core-shell Y2O3:Eu-Y2O3 nanoparticles: Photoluminescence study

175

        Dorendrajit Singh & L Robindro Singh

 

 

 

Luminescence studies during combustion synthesis of a long afterglow

178

phosphor Sr4Al14O25:Eu2+,Dy3+

 

        N Suriyamurthy & B S Panigrahi

 

 

 

Eu3+ luminescence in Na3SO4F and NaMgSO4F halosulphate phosphor for

181

mercury-free lamps

 

        I M Nagpure, S J Dhoble, S V Godbole, M K Bhide & R B Pode

 

 

 

Role of SiO2 in Zn2SiO4:Mn2+ phosphor used in optoelectronic materials

185

        M C ParmarW D Zhuang, K V R Murthy, X W Huang, Y S Hu &

        V Natarajan

 

 

 

Synthesis and optical properties of CdTe nanocrystals with improved

188

optical properties

 

        Kiran Jain, Vibha Srivastava & Abhilasha Chouksey

 

 

 

Spectroscopic characteristics of Sm3+ doped alkaline earth potassium titanium

193

phosphate glasses

 

        D V R Moorthy, M Jayasimhadri, Kiwan Jang, J Suresh Kumar,

        A Mohan Babu & L Rama Moorthy

 

 

 

Effect of pre-thermal treatment on the OSL response of Al2O3:Si,Ti

197

        B C Bhatt, P S.Page, N S Rawat, D R Mishra & M S Kulkarni

 

 

 

 

 

 

 

 

 

Preface

 

 

Luminescence is a phenomenon that involves conversion of higher energy upon absorption by a material to visible radiations without incandescence. It finds important applications in light sources, display devices and detection systems.  The phosphors are being used in electronic displays such as electroluminesenct displays, vacuum fluorescent displays, plasma displays and field emission displays. Phosphors also form an integral component of low cost white LEDs in the area of solid-state lighting. A large number of research groups in India and abroad are working in the area of luminescence and its applications. An “International Conference on Luminescence and its Applications- ICLA-2008”, was organized by National Physical Laboratory, New Delhi, under the auspices of Luminescence Society of India (LSI) at during February 13-16, 2008. The Luminescence Society of India was founded in 1990. Regular annual meetings and Quadri-annual international meetings are being organized by LSI ever since its inception. The present International Conference on Luminescence and its Applications is the third in its series and covers many applications of luminescence ranging from diamonds and gemstones to geosciences and from biological applications to industrial phosphors and radiation dosimetry.  The delegates from various countries like US, Canada, Japan, UK, Korea, Belgium, Taiwan and Switzerland participated in the conference. Prof. Dr V S Ramamurthy, Chairman, Board of Governors, IIT Delhi, inaugurated the conference. He spoke about luminescent materials and their diverse applications. He was very particular about the technology of materials and devices development related to the field of luminescence.

This special issue of Indian Journal of Engineering & Materials Sciences (IJEMS) based on papers presented in ICLA-2008 will promote research in the field of luminescent materials. The papers have been selected based on through review process. The editors finalized 15 papers out of twenty recommended by technical committee on the basis of contents suitable for IJEMS. The paper presented in this volume cover a fairly large spectrum of current research activities of luminescence and its applications from basic concepts to advanced applications like nanophosphors and radiation dosimetry. The special issue will give boost to researchers in the field of luminescence materials and they shall contribute with quality research. Finally, we thank Dr R S Beniwal for his cooperation and very sincere hard work to bring out this special issue on ‘Luminescence and its Applications’.

 

 

Vikram Kumar & Harish Chander

Guest Editors

National Physical Laboratory

New Delhi 110 012, India

 

 

 

 

 

     AUTHOR INDEX

 



 

 

 

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 147-150

 

 

New highly efficient green phosphor for LEDs

Mihail Nazarov, Boris Tsukerblat & Do Young Noh

 

 

To develop a highly energy-efficient white light sources, one needs to design highly efficient yellow, green and red phosphors, which are able to absorb excitation energy of blue LEDs and generate emissions. In this paper, results on production of a new green multiphase thiogallate phosphor {SrGa2S4 + MgGa2O4}:Eu2+ with improved luminescence properties have been presented. The detailed XRD analysis, Raman spectroscopy and PL study have been carried out in order to enlarge the understanding of the radiative processes in {SrGa2S4 + MgGa2O4}:Eu2+, based on two different crystallographic phases {SrGa2S4} and {MgGa2O4}, prepared by solid state reaction at 900-1000°C during 4 h with a carbon reduction atmosphere. A model of 4f-5d optical transitions with due account for the electron-vibrational interaction is discussed. An approximate simple expression for the shape function of the broad vibronic bands with allowance for the terms corresponding to the emission (absorption) from both ground and first excited vibrational levels is given. Within this approximation we analyze the room temperature experimental data on the 4f-5d transitions in thiogallates doped with Eu2+ ions. The vibronic coupling parameters, Stokes shift and nephelauxetic effect for systems under study are estimated. The theoretical results are in a good agreement with the experimental data.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 151-153

 

 

POSL studies on indigenously developed α-Al2O3:C

M S Kulkarni, D R Mishra, K P Muthe, S K Gupta & D N Sharma

 

The pulsed optically stimulated luminescence (POSL) technique is known for its good signal to noise ratio, fast, and multiple readout features in radiation dosimetry in general and personnel monitoring in particular. Apart from this the POSL method also provides the estimation of the luminescence lifetime t which cannot be measured in CW-, LM OSL techniques. The POSL signal is recorded on the indigenously developed α-Al2O3:C using 532 nm diode pumped solid state laser and high intensity blue (470 nm) light emitting diode cluster for different pulse widths (5–20 μs) and different repetition rates. The results are also compared with commercially available single crystal α-Al2O3: C. The luminescence life time is estimated to be ≈ 35 ms is observed in both the samples. The POSL studies show the developed sample do not have long decay tail in time profile of POSL curve indicating suitability of the developed material for POSL routine dosimetry and qualitative difference of defect formation in developed sample as compared to those formed in the commercially available sample .

Keywords: Optically stimulated luminescence, POSL, a-Al2O3:C

 

 

Indian Journal of  Engineering & Materials Sciences

Vol. 16, June 2009, pp. 154-156

 

 

 

 

Delayed optically stimulated luminescence of Al2O3:Si,Ti phosphor

P S Page, B C Bhatt, N S Rawat, D R Mishra & M S Kulkarni

 

In some Al2O3 samples, the OSL is seen to decay much more slowly that we would expect due to re-trapping of the released charge in shallow traps. The preliminary studies indicate that Al2O3:Si,Ti has some component of delayed optically stimulated luminescence (DOSL). Therefore, DOSL in this system has been investigated in detail and relative contribution of DOSL to the CW-OSL signal has been determined. Therefore, OSL readout has been performed at elevated temperatures (in the range 27-100ºC) in order to eliminate the contribution of DOSL in the CW-OSL signal. The dependence of DOSL signal on readout temperature can be explained in terms of Arrhenius equation of thermally released charges from shallow traps. The total contribution of the DOSL to the CW-OSL intensity is estimated to be about 1.4%. Although the contribution of DOSL to the CW-OSL integral signal is much less, it is advisable that OSL measurements be performed at 75ºC to avoid any contribution of DOSL signal to CW-OSL signal. The DOSL decay shows the second order exponential fit. The activation energy calculated for the trap responsible for DOSL is 0.5 ±0.04 eV.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 157-160

 

 

Electroluminescence of CdS nanoparticles-polyvinyl carbazole composites

Pooja Chouksey, B P Chandra & M Ramrakhiani

 

In the present study thin films of CdS nanoparticle-polyvinyl carbazole (PVK) composite have been prepared using chemical method. The absorption spectra and electroluminescence of the films doped with different concentrations of CdS nanoparticle have been measured. The absorption of pure PVK film starts at 290 nm wavelength in which a peak appears at 270 nm, indicating that the optical energy gap of PVK film is 4.26 eV. The absorption onset of CdS-PVK thin films is obtained at 300 nm, which gives the band gap of CdS nanoparticles as 4.13 eV. It is observed that the current varies linearly, whereas EL intensity varies non-linearly with increasing voltage. At a particular frequency, the emission starts at a particular threshold voltage and then it increases rapidly with increasing voltage. At a particular frequency and voltage, the EL intensity of the composite increases with concentration of CdS nanoparticles in PVK polymer and attains saturation at 5% CdS concentration. It is shown that the EL of CdS-PVK composites can be explained on the basis of electron acceleration-collision mechanism.

 

 

Indian Journal of Engineering & Materials Scirnces

Vol. 16, June 2009, pp. 161-164

 

 

Swift heavy ion induced thermoluminescence studies in
polycrystalline aluminum oxide

 

K R Nagabhushana, B N Lakshminarasappa, D Revannasiddaiah, D Haranath & Fouran Singh

 

 

When energetic swift heavy ions interact with matter, inelastic collision (leading to electronic energy loss-Se) and elastic collision (leading to nuclear energy loss -Sn) take place. In the present study, the effect of energetic ion species on thermoluminescence (TL) of polycrystalline aluminum oxide (PAO) is reported. PAO pellets of 6 mm diameter are irradiated with energetic Au9+, Ni7+ and Si7+ ions for the fluence of 1×1013 ions cm-2. A single well resolved prominent TL glow with peak at 538 K is observed in Si7+ irradiated samples. However, in Ni7+ and Au9+ irradiated samples a prominent TL glow with peak at 610 K along with a shoulder at 513 K is observed. On the other hand, when PAO samples are irradiated with g-rays two well separated TL glows with peaks at 483 K and 638 K are observed. A prominent PL emission with peak at 430 nm besides a weak emission with peak at 480 nm and a shoulder at 525 nm are observed in 120 MeV Au9+ion irradiated samples when excited with 320 nm. These PL peaks are attributed to F, F2+ and F22+-centers respectively. However, in Si7+ irradiated samples a single PL emission peak at 430 nm is observed and it is attributed to F-centers.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 165-168

 

 

Synthesis and thermoluminescence studies of Sr4Al14O25:Eu2+  phosphor

Suchinder Sharma, Shreyas Pitale, M M Malik, R N Dubey, M S Qureshi, S K Vasisth

& P Pathakb

 

Trapping parameter, the activation energy (E), the order of kinetics (b) and the frequency factor (s), are determined for the solution combustion synthesized Sr4Al14O25: Eu2+ phosphor using 60Co irradiation source. The glow curve is a double peak structure with prominent peak at 487 K with shoulder at 423 K. Non-shifting Tm property is utilized for the trap parameter determination. Glow curve deconvolution (GCD) is carried out on recorded glow curves after gamma radiations. The trap depths calculated ranges between 0.5-1.36 eV. The linearity characteristic of the present phosphor and the fading experiments suggests the aptness of present phosphor towards dosimetric applications.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 169-171

 

 

Thermoluminescence dosimetric study of X-ray irradiated BAM:Eu

K V R Murthy, A S Sai Prasad, B Subba Rao & Louis Rey

 

Thermoluminescence of 0.5Gy X-ray irradiated BAM:Eu has been studied. The irradiated phosphor has been studied for its TL properties after one week of irradiation and after 100 weeks of storage. The TL of BAM recoded after one week of irradiation and after 100 weeks of storage. Before storage for 100 weeks the TL of 0.5Gy X-ray irradiated phosphor displays a broad TL with a hump around 180oC followed by a peak at 273°C. After storage for 100 weeks the TL pattern entirely changed, i.e., the mixed peak emerged as two well resolved and high intensity peaks at 215 and 300oC. Normally after storage to 100 weeks, the peak at 190oC reduces its intensity or disappears in most cases, instead of that the peak appears at 215°C is a well resolved and the intensity is almost to the intensity of 300oC peak. Since the TL phenomenon observed is interesting. The two well resolved, isolated, high intensity peaks observed after 100 weeks of storage approves this BAM:Eu can be used as TL dosimetric material. The photoluminescence (PL) of BAM:Eu excited with 254 nm given an emission peak at 450 nm.

Keywords: Thermoluminescence (TL), Photoluminescence (PL)

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 172-174

 

 

Energy response study of thermoluminescent dosimeters to synchrotron
radiation in the energy range 10-35 keV

A K Bakshi, B S Dhabekar, S Chatterjee, V J Joshi & R K Kher

 

LiF:Mg,Ti, LiF:Mg,Cu,P and CaSO4:Dy TLDs are worldwide used in the field of medical dosimetry, personnel monitoring and environmental monitoring. In view of the wide spread applications of synchrotron radiation for material research and diagnostic radiology in particular medical imaging, the present study of the energy response of some popular TLDs was undertaken. For the energy response study the most useful energy range 10-35 keV of synchrotron radiation was chosen and the present experimental work was carried out at SYRMEP beam line of Elettra Synchrotron Accelerator facility, Bassoviza, Trieste, Italy. The LiF based TLDs in the form of chips and disc, and CaSO4:Dy in the form of disc of thicknesses 0.8 mm and 0.4 mm made up of mixture of CaSO4:Dy phosphor and Teflon in the weight ratio 1:3 were used. The energy of the synchrotron radiation was calibrated using a Si (111) double crystal monochromator and several thin foils   starting from Zn with Kedge 9.659 keV to KI compound with Kedge 33.169 keV. The energy response of the TLDs were normalized with respect its response to 60Co and corresponding relative response was evaluated. It was found that for CaSO4:Dy discs the relative response is about 12 at 25 keV which is maximum and subsequently falls down on either side of energy for both 0.4 mm and 0.8 mm thick discs. The relative response at 10 keV was found to be about 4.5 and 6 for 0.8 mm and 0.4 mm thick discs of CaSO4:Dy respectively. Maximum relative response of LiF:Mg,Cu,P chip of thickness 0.4 mm was found to be about 1.26 at 25 keV and it also exhibited lower response on either side of energy. LiF:Mg,Ti chips and discs show maximum response at the 30 keV which were 1.33 and 1.39, respectively. At 10 keV which was the lowest energy used in the present study, the relative response was always found to be less than 1 for LiF based TLDs. The relative response of the TLDs evaluated in the present experiment was compared with the published value in the literature and also confirmed through theoretical calculation using ratio of mass absorption coefficient of these materials with respect to air.

           Keywords: Synchrotron radiation; energy response; TLDs;

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 175-177

 

 

Preparation of Eu3+ doped Y2O3 and core-shell Y2O3:Eu-Y2O3 nanoparticles: Photoluminescence study

Dorendrajit Singh & L Robindro Singh

 

Nanocrystalline of Y2O3 doped with Eu3+ at different concentrations and also core-shell of Y2O3 is prepared by wet chemical method using urea hydrolysis at low temperatures. XRD, TEM and FTIR are used to characterize the prepared nanoparticles. The sizes determined by XRD are well in agreement with TEM results. As-prepared samples show luminescence peak of Eu3+ transition 5D0 à 7F2 at 615 nm but annealed samples at 610 nm. Core-shell study of the nanoparticles show reduction in the luminescence intensity compared to the core particles.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 178-180       

 

 

Luminescence studies during combustion synthesis of a long afterglow phosphor Sr4Al14O25:Eu2+, Dy3+

N Suriyamurthy & B S Panigrahi

 

The long glow persistent phosphor Sr4Al14O25:Eu2+, Dy3+ has been synthesized through combustion route. SrAl4O7 and SrAl2O4 are identified as the intermediate products formed at different temperatures during the synthesis of Sr4Al14O25:Eu2+,Dy3+. The photoluminescence and afterglow emission of the intermediate products have been systematically studied. The photoluminescence and afterglow emission profiles of the intermediate products varied with the temperature of synthesis. For a sample with similar aluminate phases (at a particular synthesis temperature) the λAGL and λPL are different. However, for Sr4Al14O25:Eu2+,Dy3+ annealed at 1200-1300ºC, the AGL and PL emissions are similar.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 181-184

 

 

Eu3+ luminescence in Na3SO4F and NaMgSO4F halosulphate phosphor for mercury-free lamps

I M Nagpure, S J Dhoble, S V Godbole, M K Bhide & R B Pode

 

Polycrystalline Na3SO4F:Eu and NaMgSO4F:Eu phosphors prepared by a wet chemical method has been studied for its photoluminescence (PL) characteristics. PL emission spectra of Na3SO4F and NaMgSO4F, phosphors under 393 nm excitation (mercury-free excitation) shows very strong prominet peak at 591 nm due to 5Do à7F1 transition and 613 nm corresponding to 5Do à7F2 transition in the red region of the spectrum. The PL emission spectra of Eu3+ ion in the Na3SO4F:Eu and NaMgSO4F:Eu phosphors are applicable for mercury free lamp industries.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 185-187

 

 

Role of SiO2 in Zn2SiO4:Mn2+ phosphor used in optoelectronic materials

M C ParmarW D Zhuang, K V R Murthy, X W Huang, Y S Hu & V Natarajan

 

Zn2-xMnxSiO4 is a classical green phosphor, and it has been used in many applications, such as CCFL, CRT, PDP etc. In this paper, Zn2SiO4:Mn2+ green phosphor is fabricated with the solid-state reaction method. Photoluminescence and crystalline properties are examined as functions of the firing temperatures. Zn2-xMnxSiO4 is ground and fired at 1200oC for 4 h in air, but intensity of emission is weak. Therefore, the conditions of firing are changed and Zn2-xMnxSiO4 are ground and fired at 1000oC for 2 h in air and again ground and fired at 1200 oC for 4 h in air respectively. When varies SiO2 value from 0.9 to 1.8 however the ZnO is 1.92 as well as MnCO3 is 0.08 are constant, The SiO2 concentration (1.1) show good PL spectra. The PL peak observed at 524 nm in these phosphors suggests their potential as green emitting phosphors under 254 nm excitation.

Keywords: Phosphors, X-ray method, Photoluminescence, Zn2SiO4-Mn2+

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 188-192

 

 

Synthesis and optical properties of CdTe nanocrystals with
improved optical properties

 

Kiran Jain, Vibha Srivastava & Abhilasha Chouksey

 

CdTe nanocrystals are prepared by hydrothermal route using the reaction between Cd2+ and KHTe in the presence of thioglycolic acid as the stabilizing agent. Hydrothermal synthesis under optimum conditions resulted in a rapid growth. CdTe nanocrystals with high PL intensity and narrow PL spectra are obtained in less time. The growth mechanism of CdTe nanocrystals is investigated. The growth rate in the initial stage of synthesis is higher in hydrothermal synthesis resulting in an increased growth in diffusion controlled focused region.

Keywords: CdTe, Nanostructures, Hydrothermal, Luminescence

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 193-196

 

 

Spectroscopic characteristics of Sm3+ doped alkaline earth potassium titanium phosphate glasses

 

D V R Moorthy, M Jayasimhadri, Kiwan Jang, J Suresh Kumar, A Mohan Babu & L Rama Moorthy

 

The paper reports on the preparation and characterization of Sm3+ doped alkaline earth potassium titanium phosphate (RKTP) glasses with molar composition of 24(NaPO3)6 + 30KH2PO4 + 25TiO2 + 20RCl2 + 1Sm2O3 (R=Mg, Ca & Sr). Optical absorption spectra in the UV-VIS-NIR region reveal twelve absorption bands and are assigned to different transitions arising from the 6H5/2 ground state. The energy level structure of Sm3+ (4f5) has been analyzed using the free-ion Hamiltonian model. The root mean square deviations between the experimental and calculated energies of Sm3+ doped MgKTP, CaKTP and SrKTP glasses are 44, 35 and 56 cm-1 respectively and are comparable with the earlier reports. By measuring the areas under the absorption peaks, the experimental oscillator strengths are calculated and the phenomenological JO-intensity parameters (Ω2, Ω4 and Ω6) have been determined with the help of least-squares fitting approach. These parameters exhibit a similar trend as Ω264 in all the three glasses. The evaluated JO parameters are then used to calculate the excited 4G5/2 level radiative properties such as radiative transition probabilities (AR), branching ratios (βR) and lifetimes (τR). The emission spectra recorded by exciting with 476 nm shows four peaks at 563, 599, 649 and 714 nm and are assigned to 4G5/2 6H5/2, 6H7/2, 6H9/2, 6H11/2 respectively. The experimentally observed decay profiles of the 4F5/2 level of Sm3+ are found to be single exponential yielding the lifetimes (τmes) 2330, 1750 and 2320 μs in MgKTP, CaKTP and SrKTP glasses respectively, which are comparable with the calculated lifetimes (τR) obtained from the Judd-Ofelt theory.

 

 

Indian Journal of Engineering & Materials Sciences

Vol. 16, June 2009, pp. 197-199       

 

 

Effect of pre-thermal treatment on the OSL response of Al2O3:Si,Ti

B C Bhatt, P S Page, N S Rawat, D R Mishra & M S Kulkarni

 

We have recently reported optically stimulated luminescence (OSL) characteristics of the Al2O3:Si,Ti phosphor along with some thermoluminescence (TL) and photoluminescence (PL) studies. The TL glow curve of this phosphor shows peaks around 158, 191, 276 and 355ºC for a heating rate of 4 Ks-1. In order to investigate the contribution of individual TL traps to OSL signal, CW-OSL was studied as a function of pre-thermal treatment in the temperature range 27-450ºC. The integrated CW-OSL intensity of the phosphor remains constant up to 100ºC; beyond this temperature the integrated intensity goes on decreasing with increase in temperature. After a pre-thermal treatment at 225ºC the CW-OSL intensity falls by 73% of its initial value. Hence, it can be concluded that the TL traps up to 225ºC are responsible for the major contribution to the CW-OSL signal in this phosphor. The OSL indicates that all the TL traps, up to 400ºC, give measurable contribution to the OSL signal. The OSL signal becomes insignificant when the exposed phosphor is annealed beyond 400ºC. It decreases nearly to zero for the sample annealed at 400ºC as compared to the OSL intensity of the sample without any pre-thermal treatment. Optical bleaching results indicate that all the TL peaks decrease continuously as a function of bleaching time.