Solid electrolytes based on zirconium dioxide partially stabilized with oxides of yttrium, gadolinium, and samarium

The phase composition, structure, conductivity, crack resistance, and microhardness of crystals (ZrO2)1-x(R2O3)x, where R = Y, Gd, Sm, and (x = 0.03, 0.04, 0.05) were studied. Crystals were grown by directed crystallization of the melt in a cold crucible. Crystals were studied by X-ray diffraction, transmission electron microscopy, impedance spectroscopy, and indentation. The concentration dependences of the investigated characteristics of crystals are obtained. It has been shown that an increase in the concentration of the stabilizing oxide in all cases leads to a decrease in the amount of the transformed t-phase and reduces the value of the crack resistance of the crystals. In this case, a decrease in the size of the twins and an increase in the defectiveness of the structure are observed, which is accompanied by a slight decrease in the electrical conductivity of tetragonal solid solutions. The influence of the ionic radius of trivalent cations on the stabilization of tetragonal phases, conductivity, and the mechanical properties of crystals is discussed. An increase in the values of crack resistance and a decrease in the values of high-temperature electrical conductivity of tetragonal solid solutions in the series Y2O3 -> Gd2O3 -> Sm2O3 at comparable concentrations of stabilizing oxides were established. It has been shown that ZrO2 solid solutions stabilized with Sm2O3 can be used as functional supporting membranes in solid oxide fuel cells.