Ionic conductivity of zirconia based ceramics from single crystals to nanostructured polycrystals

The ionic conductivity of yttria doped zirconia polycrystals was measured by impedance spectroscopy in the temperature range 240–800°C in air and compared to that of a single crystal. Polycrystals with 4% mol yttria and an average grain size of 300 nm have exhibited a grain boundary contribution to the ionic conductivity (value and activation energy) higher than the volume measured in the 9.5% mol yttria doped zirconia single crystal. The bulk conductivity of polycrystals with 9.5% mol yttria was found to be smaller than the single crystal one. The interpretation of the grain boundary contribution to ionic conductivity, measured by impedance spectroscopy, is revisited.