Relationship between local structures and ionic conductivity in ${\mathrm{ZrO}}_2$-${\mathrm{Y}}_2$${\mathrm{O}}_3$ studied by site-selective spectroscopy

The luminescence properties of ${\mathrm{Eu}}^{3+}$ ions in yttria-stabilized zirconia crystals are studied on samples with various yttria concentrations by using site-selective spectroscopy. From the analysis of luminescence spectra excited by ultraviolet light, it is found that the average crystal-field strength which acts on the ${\mathrm{Eu}}^{3+}$ ions increases with increasing dopant concentration. A detailed analysis of the site-selective spectra reveals that three distinct, but very similar sites for ${\mathrm{Eu}}^{3+}$ ions exist and, furthermore, the existence ratio of each site continuously changes with increasing dopant concentration. We propose local-structure models around the ${\mathrm{Eu}}^{3+}$ ions and discuss the relationship between local structures and ionic conductivity in this system.