Optical properties of (ZrO$_{2}$)$_{1-x}$(Y$_{2}$O$_{3}$)$_{x}$ ($x$ = 0–0.037) crystals grown by directional crystallization of the melt

The luminescent and optical properties of materials based on zirconium(IV) oxide grown by crystallization of ZrO$_{2}$ melts with 0, 2.0, 2.5, 2.8, and 3.7 mol % of Y$_{2}$O$_{3}$ are studied. Using Raman spectroscopy, it is found that this material with the Y$_{2}$O$_{3}$ concentration below 2 mol % is mainly a monoclinic ZrO$_{2}$ phase. The photoluminescence spectra of these crystals contain a blue–green band peaking at an energy of 2.4 eV. This fact in combination with the specific features of the refractive index and absorption coefficient dispersions indicates the presence of high concentrations of oxygen vacancies and polyvacancies in the samples. At higher concentrations of Y$_{2}$O$_{3}$ in the mixture, the tetragonal ZrO$_2$ modification becomes dominant in the materials under study and the blue–green luminescence intensity decreases. The experimental optical spectra are analyzed in comparison with the ab initio calculated spectra for ideal ZrO$_{2}$ crystals in the cubic, tetragonal, and monoclinic phases.