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- 저자 : Lochab, S.P. (검색결과 3 건)
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Thermoluminescence characteristics of CaS doped with rare earth ions Ce and Sm
Geeta Sharma,S.P. Lochab,Nafa Singh 한국물리학회 2011 Current Applied Physics Vol.11 No.3
CaS:Ce, Sm nanophosphors have been synthesized using solid state diffusion method with an aim to study the thermoluminescence characteristics of CaS:Ce,Sm system with varying concentrations of cerium and smarium in CaS host. The structural characterization of nanophosphors was done using XRD and TEM spectroscopy. We have investigated the effect of different concentrations of cerium and smarium in CaS host on the TL intensity. TL intensity is found to be maximum for CaS:Ce_0.4Sm_0.6. The effect of different heating rates on the TL glow curves recorded after a UV exposure of 560 mJ/cm^2 has been investigated. Peak of the TL glow curve shifts toward higher temperature as the heating rate increases and the TL intensity decreases. Effect of different doses of UV on the TL glow curve of CaS:Ce_0.4Sm_0.6 at a heating rate of 10 K/s has been studied and all the glow curves show a single peak around 440 K. With increasing dose the TL intensity increases linearly upto 560 mJ/cm^2 of the dose and afterward saturation region is obtained upto 13.5 J/cm^2. Beyond it a fall is recorded upto 80 J/cm^2 of the exposure. Analysis of the TL glow curve and calculation of the trapping parameters has been done with the help of Glow curve deconvolution software.
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Study of the Electronic Structure and Luminescence of Mn-doped SrS Phosphors
Ankush Vij,Sanjeev Gautam,채근화,R. Brajpuriya,S.P. Lochab 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.10
In this paper, the electronic structure and the luminescence properties of Mn (1 mole%)-doped SrS phosphors synthesized by using the solid state diffusion method are reported. The X-ray diffraction pattern reveals a single-phase rocksalt structure, and the average crystallite size calculated using a Williamson-Hall plot is 72 nm. The near-edge X-ray absorption fine structure (NEXAFS) collected at Mn L<sub>3,2</sub>-edges confirms the presence of divalent Mn in SrS. A bright green photoluminescence (PL) at 547 nm is observed at an excitation wavelength of 355 nm, which may be attributed to the <sup>4</sup><i>T</i><sub>1</sub>−<sup>6</sup><i>A</i><sub>1</sub> inner atomic transition of the 3<i>d</i> electrons in the Mn<sup>2+</sup> ion under the cubic crystal field of SrS. We have also studied the thermoluminescence (TL) of UV (254 nm)-irradiated Mn-doped SrS phosphors. The TL glow curve has a well-resolved single peak around 360 K, which shifts slightly to lower temperatures with increasing UV exposure time, confirming second-order kinetics. A kinetic analysis of the experimental TL glow curve has been carried out using Chen’s peak shape method to determine the trapping parameters.
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Gupta, K.K.,Kadam, R.M.,Dhoble, N.S.,Lochab, S.P.,Singh, V.,Dhoble, S.J. Elsevier Sequoia 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.688 No.2
In this study, we have synthesized Dy<SUP>3+</SUP> activated Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F (S-FAP) phosphors by sol-gel synthesis method. The synthesized phosphors were characterized by X-ray diffraction pattern (XRD), scanning electron microscopic (SEM), photoluminescence (PL) and thermoluminescence (TL) for structural, morphological and luminescent properties. Dy<SUP>3+</SUP> activated Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphor shows its characteristic PL emission at 481 nm and 574 nm due to <SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>15/2</SUB> and <SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>13/2</SUB> transitions, respectively. TL characteristics of Dy<SUP>3+</SUP> doped Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphors were taken after irradiation by <SUP>60</SUP>Co gamma exposure. Two separate TL peaks at 126 <SUP>o</SUP>C and 279 <SUP>o</SUP>C were observed in case of Dy<SUP>3+</SUP> doped phosphor. Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor was irradiated within a wide range of exposure of 50 Gy to 7 kGy doses. Linearity was found up to 2 kGy and thereafter TL response saturates. Fading study was also carried out over the duration of six weeks for Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F phosphor. Trapping parameters were calculated using Chen's peak shape method, initial rise method and various heating rate method. Glow curve is deconvoluted using computerized glow curve deconvolution program. TL sensitivity of Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor is found to be less by a factor of 2.08 than commercially used CaSO<SUB>4</SUB>:Dy phosphor. In order to identify the defect centers formed upon γ-ray irradiation in Sr<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB>F:Dy<SUP>3+</SUP> phosphor, EPR measurements were carried out on un-irradiated and irradiated phosphors.
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