Pressure-induced phase transition in LiLuF4:Pr3+ investigated by an optical technique

The luminescence and luminescence kinetics of LiLuF4 doped with 1.5 at.% of Pr3+ obtained at high hydrostatic pressure changing from ambient to 220 kbar applied in a diamond anvil cell are presented. It has been shown that pressure causes shift of the emission lines toward the red with rates of the order of single cm-1 kbar-1. The pressure-induced phase transition from tetragonal to fergusonite structure for pressure above 100 kbar was observed. The crystal field calculations performed showed that this phase transition reduces the point symmetry of the Pr3+ site from the S4 to the C2 point group. (paper)