Ionic Conductivity and Mechanical Properties of Post-HIPed Cubic Zirconia/Alumina Composites

8 mol.% yttria-doped cubic zirconia (8Y-CSZ)/AI₂O₃ composites containing 0-30 vol.% Al₂O₃ particles were fabricated by sintering, followed by hot isostatic pressing (post-HIPing). All composites were densified to at least 99·5% of the theoretical density by post-HIPing. The bending strength of composites sintered at 1500°C in air was independent of A1₂O₃ content, but a significant improvement in the bending strength was achieved by the post-HIPing technique. The bending strength and the fracture toughness of the HIPed composites increased with increasing A1₂O₃ content. Ionic conductivity of the composites was evaluated and the total, lattice, and grain boundary conductivities slightly decreased with increasing A1₂O₃ content. The HIPed composites containing up to 20 vol.% A1₂0₃ appear to be suitable candidate materials as electrolyte for solid oxygen fuel cell.