Calcium zirconate as a solid electrolyte for electrochemical devices applied in metallurgy

Stoichiometric calcium zirconate and CaZrO3 samples with an excess of calcia or zirconia were obtained from powders prepared by the citrate method. XRD measurements were used to determine the phase compositions of the sintered materials as well as their crystal structures. The compositional dependence of the calcium zirconate cell parameter indicates that an excess of calcia or zirconia form a solid solution. Stoichiometric CaZrO3 appeared to be a rather poor oxygen ion conductor, whereas calcium zirconate samples with an excess of calcia or zirconia exhibit pure oxygen conductivity. The introduction of a respective excess of cations led in both cases to a significant enhancement of conductivity. The fracture toughness, hardness, and flexural strength of the samples were also investigated. The mechanical and electrical properties of CaZrO3-based materials are comparable to those of zirconia solid electrolytes. The lower thermal expansion coefficient and better resistance to thermal shock make CaZrO3 a more suitable solid electrolyte for metallurgical applications.