Analysis of dosimetric characteristics of CaSO4:Mn,Tb phosphors synthesized by four different routes

Abstract

The luminescence properties of crystalline materials are critical for monitoring physical phenomena, including ionizing radiation doses. In this study, CaSO4:Mn,Tb phosphors were synthesized using four distinct methods: solid-state diffusion, co-precipitation, sol-gel, and slow evaporation routes. The influence of synthesis conditions on the structural, morphological, elemental, and luminescent properties of the phosphors was systematically investigated. X-ray diffraction (XRD) patterns confirmed that all synthesis routes produced samples with a stable CaSO4 crystal phase, and doping with Tb3+ and Mn2+ did not alter the crystal structure. Scanning electron microscopy (SEM) images revealed that synthesis methods significantly influenced grain morphology. Energydispersive X-ray spectroscopy (EDS) spectra validated the successful incorporation of Tb3+ and Mn2+ ions into the crystal lattice. The slow evaporation route, followed by co-precipitation, yielded the highest intensity of thermoluminescence (TL) glow curves, which were characterized using Schott BG-39 and Hoya U-340 bandpass filters to control wavelengths. Different emission curve behaviors for TL were observed. In the optically stimulated luminescence (OSL) analyses, obtained with continuous intensity optical stimulation and a 40 s integration time, all samples exhibited an exponential decrease in OSL signal as the charge traps were emptied. The CaSO4:Mn,Tb phosphor produced via the sol-gel route, and that synthesized by slow evaporation, showed the highest OSL intensity, followed by those produced via co-precipitation and solid-state synthesis. However, the high coefficient of variation (CV) in TL/OSL responses of samples produced by sol-gel and co-precipitation methods limited the reproducibility of the luminescent measurements. The slow evaporation route emerged as the most consistent and efficient method, exhibiting low CV values (<10 %) in terms of signal variation and sensitivity, the highest linear correlation in the dose-response relationship over the irradiation range of 0.16 Gy–100 Gy, and greater TL signal stability for long-term applications.