Doping disorder and the reduction–doping process in LiSrPO4

A systematic theoretical study was performed on trivalent and divalent rare-earth (RE) dopant ions in the LiSrPO4 structure, using atomistic simulations based on lattice energy minimization. It was found that RE3+ and RE2+ ions are most energetically favorable for incorporation at the Sr site. For RE3+ ion incorporation, charge compensation by vacancies or anti-site defects are both probable. In order to investigate the reduction-doping process (Europium reduction), two schemes (open atmosphere and H2 reducing atmosphere) were considered. A H2 reduction atmosphere was found to be the most effective agent for Eu reduction. Results reveal that the most probable charge compensation mechanism and the host site preference for rare-earth doping ions play important roles in the investigation of the mechanism of the luminescence properties of LiSrPO4.