CONDUCTIVITY MEASUREMENTS OF VARIOUS YTTRIA-STABILIZED ZIRCONIA SAMPLES

Samples of yttria-stabilized zirconia manufactured by the following fa brication procedures, were obtained from commercial sources: (i) hot i sostatic pressing; (ii) tape casting; (iii) vacuum plasma spraying, an d (iv) calendering. The ionic conductivities of these samples were mea sured by (a) impedance spectroscopy; (b) the four-point probe method; (c) the current-interruption technique, and (d) the van der Pauw techn ique. The tape-cast and hot pressed samples showed good and very repro ducible conductivity values. The vacuum plasma sprayed samples showed an anisotropy in their conductivity, with the cross-plane value being several times lower than the in-plane value. A simple model based on t he porous microstructure of these samples can explain this observation . Sintering of the plasma sprayed samples minimized the anisotropy and significantly improved their conductivity values. The calendered samp les also showed a similar anisotropy in their conductivity data when t hey were inadequately sintered.