Optical characterization of Pr3+-doped yttria-stabilized zirconia single crystals

Abstract

The optical absorption and fluorescence of Pr${}^{3+}$ ions in yttria-stabilized zirconia single crystals are investigated. Fluorescence emissions from the ${}^{1}{D}_{2}$ level are clearly dominant and low intensity emission lines from the ${}^{3}{P}_{0}$ and ${}^{1}{G}_{4}$ states are also observed. Analysis with the Judd-Ofelt theory of the absorption intensities has been made assuming that only $\ensuremath{\sim}40$% of the praseodymium ions contribute to the optical absorption bands. Quantum efficiency values of $\ensuremath{\eta}{(}^{3}{P}_{0})\ensuremath{\sim}0.2$ and $\ensuremath{\eta}{(}^{1}{D}_{2})\ensuremath{\sim}$ 1 are obtained at room temperature. ${}^{1}{D}_{2}$ fluorescence quenching has been observed in heavily-doped samples due to cross relaxation processes among neighboring Pr${}^{3+}$ ions. Analysis using the Inokuti-Hirayama model shows that electric dipole-dipole interactions are mainly responsible for the quenching effect. Pr${}^{3+}$ ions are present in seven and sixfold configurations with a statistical distribution. The energy position of the $4f5d$ configuration is very different for each center. The fluorescence dynamics is explained by a mechanism involving thermally assisted population of the ${}^{3}{P}_{1,2}{+}^{1}{I}_{6}$ upper levels and fast relaxation to the ${}^{1}{D}_{2}$ level via states of the excited $4f5d$ configuration.