Thermoluminescence behaviour and kinetic analysis of a novel Tb³⁺-Doped LaCa₄O(BO₃)₃ phosphor: Impacts of heating rates and dose

Abstract

This study employs kinetic analysis methods to comprehensively understand the thermoluminescence (TL) behaviour of Tb³⁺-doped LaCa₄O(BO₃)₃ (LACOB), applying the Hoogenstraaten and Booth-Bohun-Parfianovitch methods, as well as the T_m-T_stop and Glow Curve Deconvolution (GCD) techniques. Optimal TL intensity was found at a Tb³⁺ concentration of 2 wt%, beyond which concentration quenching occurred. The complete TL glow curve before preheating displays two peaks at approximately 70 °C and 286 °C. After preheating, only the 286 °C peak remains, due to its greater stability and intensity, making it the primary TL peak relevant for dosimetric applications. As the heating rate increased, the TL glow peaks shifted to higher temperatures and exhibited reduced intensity due to thermal quenching. The TL intensity exhibited superlinear behaviour at lower doses (0.5–20 Gy), followed by nearly linear behaviour at intermediate doses (30–100 Gy), and sublinear behaviour at higher doses. Anomalous fading of the TL signal was observed in LACOB:2 wt%Tb, suggesting competition with radiationless transitions. Activation energy values derived from Hoogenstraaten and Booth-Bohun-Parfianovitch methods showed close alignment, supporting the reliability of the kinetic analysis. The T_m-T_stop and GCD analyses with preheating identified four distinct TL glow peaks, with activation energies between 1.72 and 1.82 eV. Analysis whole glow curve revealed nine TL glow peaks overall, ranging from 1.08 to 1.82 eV, reflecting a complex trap structure with continuous energy distributions. The GCD method yielded a Figure of Merit (FOM) of 2.67 % with preheating and 2.84 without preheating, indicating a strong fit between experimental and theoretical data in both cases. The material demonstrated excellent stability and reusability, making it a strong candidate for dosimetric applications.