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 $\sim 40$% of the praseodymium ions contribute to the optical absorption bands. Quantum efficiency values of $\eta {(}^3{P}_0)\sim 0.2$ and $\eta {(}^1{D}_2)\sim$ 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.

• Received 7 March 1997

DOI:https://doi.org/10.1103/PhysRevB.56.5856