HIGH-PRESSURE LUMINESCENCE AND PRESSURE-INDUCED PHASE-TRANSITION FOR LIYF4-EU

We have measured the emission spectra of LiYF4:Eu under high pressure up to 15 GPa at room temperature. On the basis of the spectra we have investigated the dependence of the Stark levels of the D-5(0,1) and F- 7(1-4) multiplets on pressure. The unsplit level of F-7(0) is taken as energy reference. We have also found that an obvious change in the sp ectra occurs and some spectral lines split into two in the pressure ra nge from 10.0 to 10.5 GPa. This phenomenon shows that a structure phas e transition occurs in the LiYF4:Eu and the crystal symmetry lowers in the pressure range.