CONDUCTIVITY AND STRENGTH BEHAVIOR OF ALUMINA(WHISKER)-ZIRCONIA COMPOSITES

Yttria stabilized zirconia (8 mol%) composites were fabricated by tape casting with either alumina powder or alumina whiskers, and pressurel ess sintered. Sintering behaviour, ionic conductivity and mechanical s trength were analysed. For all compositions analysed, increasing alumi na content reduced the sintered density. For whisker-reinforced zircon ia, the rigid whiskers prevented matrix densification along their axis . The ionic conductivity was measured by the complex impedance method from 500-1000 degrees C and the activation energy for ionic conduction calculated over that range. The ionic conductivity of the alumina-zir conia composites decreased with increasing alumina content as expected by the rule of mixtures. However, the ionic conductivity of the whisk er-zirconia composites decreased more than expected possibly due to co ntamination from the whiskers. The strength of the whisker-zirconia co mposites was also found to be affected by the porosity. At 5 vol%, the average strength was measured at 39.9 kgf mm(-2), which decreased to 24 kgf mm(-2) at 20 vol%.