Luminescence of CaWO4:Pr3+ and CaWO4:Tb3+ at ambient and high hydrostatic pressures

Photoluminescence spectra of CaWO4 doped with Pr3+ and Tb3 obtained at high hydrostatic pressures up to 315 kbar applied in a diamond anvil cell (DAC) are presented. The intensities of the luminescence from the 3P0 state of PO+ and from the D-5(3) state of Pr3+ decreased with increasing pressure. At pressures greater than 50 kbar, the D-1(2) <-> H-3(1) transitions in Pr+ and the D-5(4) <-> E-7(1) transitions in Tb3 dominated the spectra. At pressures greater than 100 kbar, only emissions from the lower excited states were observed. At pressures greater than 150 kbar, luminescence from the D-1(2) and D-5(4) states also decreased with increasing pressure, and at a pressure of 315 kbar for CaWO4:Pr3+ and 190 kbar for CaWO4:Pr3+, the emissions related to the PO+ and TIP+ were quenched. These effects were related to the influence of impurity trapped excitons (ITEs) on the efficiency of the f f emission in the PO+ and Tb3+ ions. Analysis of the emission spectra collected at different pressures allowed the energies of the ground states of the Pr3+ and Tb3+ ions with respect to the band edges of the CaWO4 host to be estimated.