Unusual intrinsic thermoluminescence in LiMgPO4:Er

Olivine-type phosphate LiMgPO4 doped with rare-earth elements is currently considered as a new dosimetric material suitable for both OSL and TSL applications and able to compete with top commercial detectors. In this work, the samples of LiMgPO4:Er3+ were synthesized by the conventional solid state reaction method. We first studied X-ray luminescence and thermally and optically stimulated luminescence in LiMgPO4:Er3+ in detail. Our studies included the structure refinement, DFT calculations, which predicted the preferred positions of both erbium and charge-compensating vacancies, and UV-vis spectroscopy. We showed that the thermoluminescence spectrum of irradiated LiMgPO4:Er3+ does not contain components caused by the 4f–4f transitions in erbium, but coincides with the spectrum of the phosphate matrix with two broad bands at 360 nm and 650 nm. We discovered a high OSL and TSL output in LiMgPO4:Er3+, despite the nonradiative deexcitation of erbium ions.