Deciphering the Role of Gamma Ray Induced Radicals in the Thermoluminescence Process of a Neutral to Cool Daylight Emitting Sr1–xB4O7–Dyx Phosphor through Electron Paramagnetic Resonance (EPR) Spectroscopy

A number of researchers have reported on the thermoluminescence (TSL) properties of many borates activated with rare earths and transition metal ions. However, there are not many reports that pinpoint the role and chemical nature of the gamma induced radicals. Further, there are even fewer reports highlighting the multifunctional characteristics of a single TSL phosphor. In this work, we showcase SrB4O7 doped with Dy3+ for the dual role of white light emitting as well as a TSL dosimetric material. We did the PL/TSL/EPR (electron paramagnetic resonance) correlation studies in order to identify the active luminescent centers, the trap parameters and the chemical nature of the radicals responsible for the phenomena. By doing a systematic study on a series of Dy3+ (1–10 mol %) doped samples, we optimized the composition. Colorimetric studies on the optimized sample revealed that it had intense near white light emission with 38.1% color purity when excited by UV-C light (247 nm). The same sample also showed a linear gamma dose response up to 1600 Gy (J/kg). A detailed EPR investigation confirmed the role of a borate based radical in the observed TSL process. We believe that the material can be a good candidate for real life application as a multifunctional material.