The influence of ceria addition on the quality of grown yttria crystals, their crystalline and defect structures

Y2O3 and CeO2-doped Y2O3 crystals were prepared by the oriented crystallization in a cold container in order to compare the influence of ceria addition on the quality of yttria crystals grown by this method as well as on their crystalline and defect structures. Ceria addition results in an increased phase stability of the melt as well as the solid phase. The crystallization of CeO2-doped Y2O3 has a rod-shaped character in comparison with the mosaic structure of undoped yttria. The distribution of cerium cations in the crystal is inhomogeneous and a part of them can be also present in the trivalent state. The addition of ceria increases the electrical conductivity of yttria due to the interstitial oxygen ions, vacancies and polarons according to the given conditions. An anomaly observed on the Arrhenius dependencies of conductivity versus temperature at low temperatures (493-593 K) could be explained by the excess vacancies formed by dislocations created during the crystallization of mosaic blocks and rods from the high temperatures in the cold container. The behavior of electrical conductivity is in a good agreement with that of microhardness