On the energy transfer in LiMgPO4 doped with rare-earth elements

The phosphates LiMgPO4:RE (RE – Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm) with an olivine-type orthorhombic structure were synthesized by the conventional solid state reaction route and their optical properties were examined by the experimental and theoretical methods. In this work, we showed that the radioluminescence and thermoluminescence spectra of irradiated LiMgPO4:RE (RE = Sm, Gd, Tb, Dy, Tm) consist of lines reflecting 4f–4f transitions in the rare-earth element. For LiMgPO4:RE (RE = Nd, Ho, Er), they coincide with the spectrum of the phosphate matrix with two broad bands at 360 nm and 650 nm but are much more intense. A model of energy transfer is proposed to explain this phenomenon. It is shown that the model is confirmed by the features of photoluminescence in doped LiMgPO4 and by the results of ab initio calculations.