Ionic conductivity of CaO–Y2O3–ZrO2 materials with constant oxygen vacancy concentration

Structural modification of the fully stabilised zirconia is a possible way to improve its electrical properties. Electrical properties, especially ionic conductivity, of cubic zirconia solid solutions are strictly related to the ionic radius and valency of cations incorporated into the zirconia structure. Nanopowders with a constant oxygen vacancy concentration of 8 and 10 mol% were prepared by a hydrothermal treatment of co-precipitated zirconia hydrogels in a NaOH environment. The desired oxygen vacancy concentrations were obtained by introducing calcia and yttria, at different ratios, to the zirconia solid solutions. Phase compositions and lattice parameters of the respective phases were determined using X-ray diffraction analysis. Electrical properties of the samples were described on the basis of complex impedance spectroscopy analysis. It has been stated that substitution of calcia for yttria or yttria for calcia in zirconia solid solutions leads to ionic conductivity enhancement. Samples with a cubic structure, close to the stabilisation threshold, had the highest conductivity.