Yttria partially stabilized zirconia crystals and co-doped with neodymium, erbium or ytterbium oxides

Materials based on partially stabilized zirconia are widely used as structural non-metallic high-strength and wear-resistant materials, thermal barrier and protective coatings, as well as bioinert materials for medicine. The tetragonal phase of solid solutions based on zirconia is stabilized by doping with yttrium, cerium oxides, or oxides of other rare earth elements.

One of the possible ways to optimize the mechanical characteristics of ZrO₂-Y₂O₃ solid solutions crystals is to partially replace Y₂O₃ with oxides of other rare-earth elements. This work presents the results of studying the phase composition, structure, and mechanical properties of ZrO₂-based crystals stabilized with yttrium oxide and co-doped with neodymium, erbium, or ytterbium oxides with a total concentration of 3.2 mol.%.

The crystals were grown by directional melt crystallization in a cold container. The phase composition of the crystals was determined by X-ray diffractometry and Raman spectroscopy. The crystal structure was investigated by transmission electron microscopy. The microhardness and crack resistance of crystals were measured by the indentation method.

The study of the phase composition and structure of the crystals showed that, while maintaining the total concentration of codoning oxides, a change in the degree of substitution of Y³⁺ cations for dopant cations affects the quantitative ratio of phases, the degree of their tetragonality, and the size of twins.

The study of the mechanical characteristics of crystals, such as fracture toughness and microhardness, showed that co-doping has an insignificant effect on the change in microhardness values. The value of the crack resistance of crystals increases with an increase in the radius of the rare earth element of the co-doped oxide. The study of the monoclinic phase distribution in the region of the indenter indentation is carried out. Comparison of the obtained data on the dependence of the tetragonal - monoclinic phase transformations intensity with the data on the fracture toughness of crystals shows a general tendency towards a decrease in the values of fracture toughness with a decrease in the intensity of the tetragonal - monoclinic phase transformations.

The work was supported by research grants № 18-13-00397 of the Russian Science Foundation.