The conductivity of Y2O3-doped polycrystals was measured by means of impedance spectroscopy at 240 to 800C in air, and was compared with that of a single crystal. Polycrystals which contained 4mol%Y2O3, and had an average grain size of 300nm, exhibited a grain-boundary contribution to ionic conductivity that was higher than the volume contribution measured in 9.5mol%Y2O3-doped single crystals. The bulk conductivity of polycrystals which contained 9.5mol%Y2O3 was found to be smaller than the single-crystal value.

Ionic Conductivity of Zirconia-Based Ceramics from Single Crystals to Nanostructured Polycrystals. A.Cheikh, A.Madani, A.Touati, H.Boussetta, C.Monty: Journal of the European Ceramics Society, 2001, 21[10-11], 1837-41