On the concentration dependence of the up-conversion process of Pr

Abstract

This work concerns the concentration dependence of the optical properties of microscale samples according to the solid solution Li2Ca1–2xPrxNaxSiO4 with x = 0.001, 0.002, 0.005, 0.01, 0.02, 0.05, 0.07, and 0.1. Phase purity was inspected by using X-ray powder diffraction. In order to figure out concentration dependent similarities and differences of their properties with respect to down- and up-conversion, luminescence spectroscopy for vacuum UV (VUV), X-ray, and blue light excitation were performed. Furthermore, diffuse reflection spectroscopy as well as time dependent luminescence measurements were conducted. It turns out that the concentration quenching of the up-conversion lags the down-conversion. In addition, a rise time can be observed in the time dependent measurements of the up-conversion. From these observations, it is concluded that the up-conversion process takes place via an energy transfer process with a very high probability.