Electrical properties of stoichiometric and non-stoichiometric calcium zirconate

Stoichiometric calcium zirconate and calcium zirconate with calcia or zirconia excess sintered bodies were prepared. Electrical properties of these materials were investigated at 950 degreesC using the dc four-probe and ac impedance spectroscopy methods. XRD analysis was used to determine the changes of cell parameters. The Rietveld method was used to refine calcium zirconate structure. The emf measurements of galvanic cells were used to determine the ionic transference numbers in the selected samples. Stoichiometric calcium zirconate appeared to be a rather poor and mixed electron-oxygen ion conductor, whereas calcium zirconate samples with excess of calcia or zirconia exhibit purely oxygen ion conductivity. In both cases, introduction of a respective cation excess led to the significant enhancement in conductivity. The simple point defect model for calcium zirconate with calcia or zirconia excess was proposed. (C) 2002 Elsevier Science B.V. All rights reserved.