Investigating the optical and thermoluminescence properties of γ-irradiated Al2O3:Tb3+ phosphors for dosimetric applications

Abstract

This work demonstrates the solution combustion synthesis and characterization of Al₂O₃:Tb³⁺ phosphor, with a focus on its thermoluminescence (TL) properties for high dose γ – irradiated dosimetric applications. X-ray diffraction (XRD), confirms the formation of stable α-phase of Al₂O₃ with a rhombohedral structure The diffuse reflectance spectrum (DRS) shows the optical band gap of 4.21 eV and 4.25 for undoped and the Tb³⁺-doped samples respectively. The photoluminescence (PL) emission spectrum shows two set of characteristic emission from Tb³⁺ ions corresponding to the transitions ⁵D₃→⁷F_J (where J = 6–3) and ⁵D₄→⁷F_J (where J = 6–3). The 562 K peak in this study is unique because of its enhanced thermal stability and distinct emission behaviour, which are attributed to the doping with Tb³⁺. The optimized sensitivity was achieved at a dopant concentration of 0.05 mol% of Tb³⁺. This improvement in luminescent properties at elevated temperatures sets this study apart from existing research. Further, TL emission 3D spectra of γ – irradiated Al₂O₃:Tb³⁺ samples (0.05 and 1.00 mol%) shows characteristic transition emission of Tb³⁺, Cr³⁺ and Mn⁴⁺ and the relative intensities of the Tb³⁺ based two set of transitions emission ratios of the prominent TL glow peak were compared. TL kinetic parameters viz activation energy, order of kinetics and frequency factor were estimated by using the Computerized Glow Curve Deconvolution (CGCD) technique, with peak identification performed through the second derivative method. TL dosimetric properties such as dose response, reusability and minimum detectable dose were studied to assess their suitability for dosimetry applications. A TL mechanism based on the process of ionization of an electron, trapping and recombination is proposed.