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 degreesC 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. (C) 2001 Elsevier Science Ltd. All rights reserved.