Six samples of mixed Y2O3/CaO doped ZrO2 electrolytes, having the same nominal chemical composition of (ZrO2)0.90–(Y2O3)0.04–(CaO)0.06, were sintered at 1600C for 2, 4, 6, 8, 10 or 15h in order to make the grain size differ from sample to sample. The grain-boundary conductivity of each sample was measured by using complex impedance methods at 673 to 1073K. The results were analyzed according to the Arrhenius equation. It was found that variations in grain size could produce large changes in the activation energy for grain-boundary conduction, Egb, and that there existed a particular grain size at which Egb reached a maximum. This phenomenon was then analyzed on the basis of 2 existing models: the constriction resistance model and the brick layer model.

Grain-Boundary Effect in Zirconia Stabilized with Yttria and Calcia by Electrical Measurements. Y.Li, M.Liu, J.Gong, Y.Chen, Z.Tang, Z.Zhang: Materials Science and Engineering B, 2003, 103[2], 108-14