Thermoluminescence properties and trap hierarchy of GdBa3B9O18 revealed by multi-method kinetic analysis

Abstract

This work reports the first thermoluminescence (TL) investigation of trigonal borate phosphor GdBa₃B₉O₁₈. The material was synthesized via a urea-assisted sol–gel combustion route and structurally confirmed as a single- phase trigonal borate with space group (P6₃/m). The TL response was evaluated under β-irradiation over a dose range of 1.4–500 Gy through dose–response, fading, reusability, and heating-rate experiments combined with a multi-method kinetic analysis. The integrated TL signal exhibits a near-linear power-law dose dependence (b ≈ 1.01) between 1.4 and 200 Gy, followed by only mild supralinearity up to 500 Gy. A minimum detectable dose of ~0.11 Gy was obtained, indicating potential applicability in medium- to high-dose dosimetry. Reusability tests reveal cycle-to-cycle variations within ±5% over ten irradiation–readout cycles while maintaining a stable glow-curve structure. Heating-rate measurements (0.5–4 ◦ C s⁻¹), combined with the Kitis–Tuyn temperature-lag correction, confirm that the observed glow-peak shifts arise predominantly from intrinsic TL kinetics rather than instrumental artifacts. Variable-heating-rate (VHR), IR–T m–T stop , and computerized glow-curve deconvolution (CGCD) analyses indicate a hierarchical trap structure with activation energies ranging from ~0.87–1.98 eV and general-order kinetics (b ≈ 1.2–1.5), consistent with an energetically distributed trap system. Fading measurements reveal an unusual anti-fading behaviour, where the TL intensity reaches a maximum after ~12 h prior to the onset of conventional decay. Extended measurements up to 20 days further confirm that this non-monotonic behavior evolves into a long-term decay regime. This behavior is consistent with time-dependent charge redistribution from shallow to deeper traps via retrapping processes. Overall, these results demonstrate that GdBa₃B₉O₁₈ is a structurally stable borate phosphor with robust TL characteristics and promising potential for dosimetric applications in the Gy dose regime.