Abstract
This work discusses synthesis of stable α-phase of Al2O3:Tm3+ by combustion method using temperature controlled microwave oven. The crystalline phase was analyzed by X-ray diffraction (XRD) technique and average crystallite size was found to be 147 nm. Observations using scanning electron microscope (SEM) image suggest formation of agglomerated particles and energy dispersive x-ray spectroscopy (EDS) confirmed the incorporation of Tm3+ in Al2O3. Thermoluminescence emission (TLE) spectrum of γ – irradiated Al2O3:Tm3+ shows characteristic emissions of Tm3+, Cr3+ and Mn4+. TL glow curves of γ – irradiated Al2O3:Tm3+ exhibit a prominent peak at 453 K along with a shoulder at 496 K. The glow curves of β – irradiated Al2O3:Tm3+ were studied in different emission regions using U340 + BG39 (UV band pass), CS759 + BG39 (Blue band pass) and BG39 (Visible band pass) optical glass filters. A prominent peak was observed at 471 K in for all mentioned emission regions and an additional shoulder was observed at 511 K with CS759 + BG39 and BG39 filters. TL glow curve of β – irradiated Al2O3:Tm3+ using only BG39 filter had more counts than CS759 + BG39 and U340 + BG39 filters. Further, the effect of Tm3+ impurity on TL response was studied. TL kinetic parameters were estimated by using computerized glow curve deconvolution (CGCD) technique. The activation energy and frequency factor of prominent peak (471 K) were found to be 1.31 eV and 3.50 × 1013 s−1 respectively. Optically stimulated luminescence (OSL) characteristics of β – irradiated Al2O3:Tm3+ were studied using U340 + BG39 and CS759 + BG39 filters. Highest OSL intensity was observed in UV. OSL curves were deconvoluted by general order decay equation. Life time and photoionization cross section of the traps responsible for OSL were found to be 5.30 s and 3.98 × 10−18 cm2 respectively. The process of ionization of electron from Tm3+, electron trap in host lattice and its recombination mechanism is proposed. Phosphorescence decay of beta irradiated sample was also studied. The lifetime of phosphorescence decay was found to be 140 s for the prominent peak and TL intensity decays 25% after the phosphorescence. TL/OSL dosimetric properties viz. linearity with dose, reusability and minimum detectable dose of the phosphor were characterized for medical dosimetry application.
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