TL/OSL properties of beta irradiated Al2O3:Tm3+ phosphor synthesized by microwave combustion method

Highlights: • TL emission spectra of γ – rayed Al₂O₃:Tm³⁺ shows Tm³⁺ characteristic transitions. • Doping of Tm³⁺ ions causes enhancement of TL/OSL. • TL/OSL kinetic parameters are analyzed by CGCD method. • TL mechanism of γ/β – rayed Al₂O₃:Tm³⁺ was proposed. • TL/OSL dosimetric properties of Al₂O₃:Tm³⁺ suggests that the material is appropriate for medical dosimetry. - 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.