The influence on intrinsic light emission of calcium tungstate and molybdate powders by multivalence Pr codoping

For trivalent praseodymium (Pr3+) and quadrivalent praseodymium (Pr4+) codoped CaMO4 (M = W, Mo) powders, the luminescence propriety of matrix is obviously influenced by carrier concentration. The light emission intensity of CaWO4 matrix decreases exponentially with increasing of Pr concentration because oxygen-deficient (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mathrm{WO}_{3}\cdot V_{\mathrm{O}}^{\bullet \bullet}$\end{document}) obtains an electron supplied by Pr3+ (5d). However, the light emission intensity of CaMoO4 is enhanced by Pr codoping because the quasi-free electrons increase the probability of radiative combination. The difference of photoluminescence properties in the two materials are attributed to the bonding character of M and O in the CaMO4 structure.