Microstructure development of plasma-sprayed yttria-stabilized zirconia and its effect on electrical conductivity

4.5 mol% yttria-stabilized zirconia (YSZ) deposit was prepared by atmospheric plasma spraying (APS) using an agglomerate-sintered YSZ powder. Two samples were continuously deposited at two spray distances of 80 mm and 90 mm without intermittence during spraying. The measurement showed that the ionic conductivity of the YSZ deposit at 1000 °C significantly decreased from 0.06 S/cm to 0.033 S/cm with increasing spray distance from 80 mm to 90 mm. The deposit microstructure exhibited distinct interfaces between consecutive pass layers in the deposit sprayed at long spray distance. The decrease of ionic conductivity can be ascribed to change of the bonding ratio between consecutive passes resulting from decrease of deposition temperature with the increase of spray distance.