Effects of rare-earth doping and reduction processes in LiCaPO4 compound: A computer simulation study

Abstract

We perform a computational study of rare earth (RE) doping of the LiCaPO4 structure using an atomistic simulation based on lattice energy minimisation. Particular attention is given to the effects of RE doping on the structure of LiCaPO4. It is found that RE3+ and RE2+ dopant ions have an energetic preference to be incorporated at the Ca2+ host site. Our simulations show that for the incorporation of the RE3+ ion, charge compensation by LiCa, antisite defects is more likely to occur. In addition, the bond valence sum (BVS) is obtained for the RE3+-O2- pair. To investigate Eu reduction doping mechanisms, three reduction mechanisms (open atmosphere, CO and a H2 reducing atmosphere) are considered. An H2 reducing atmosphere was found to be the most effective agent for Eu reduction. Our results reveal the possibility of the co-existence of both Eu3+ and Eu2+ ions in the host. In fact, a specific study of the lattice deformation by various types of defect mechanisms can improve the effective rate performance of LiCaPO4 for luminescent applications.