Dependence of cross-relaxation on temperature and concentration from the D-1(2) level of Pr3+ in YPO4

We report on the role of cross-relaxation in the decay of the D-1(2) level of trivalent Pr in YPO4 in crystals with Pr concentrations of 0.1%, 1%, 2%, and 5%. We have found that the D-1(2) level decay is purely radiative in the low-doped system. As the Pr concentration is increased, the D-1(2) luminescence is quenched due to a cross-relaxation energy transfer between two Pr ions. The temporal behavior of the D-1(2) luminescence following pulsed excitation has been monitored in each sample at temperatures between 30 K and 300 K. and all decay curves were fit to the Yokota-Tanimoto model. The decay times decrease as temperature increases, due to an increase in both the radiative rate and the energy transfer rate with temperature. There is little evidence of diffusion at any temperature, even in the more concentrated samples. We have also fit the decay curves using the LumiTrans computer simulation. A comparison of the fits to the decay curves of the two methods is presented.