Synthesis and properties of cubic zirconia–alumina composite by mechanical alloying

Synthesis of 8mol%Y2O3–ZrO2 (8YSZ) powder with Al2O3 by mechanical alloying (MA) and the sintering behavior of this powder were investigated. The solubility of Al2O3 in 8YSZ was 1.15 wt.% after MA for 48 h. Large agglomerated particles formed during MA resulted in a slow densification rate of the compact. After eliminating the agglomerates by sedimentation, the relative density of 97% was obtained by sintering the compact at 1400°C for 2 h. Sintered microstructure of mechanically alloyed 3wt.%Al2O3–8YSZ (3A8YSZ) consisted of 8YSZ grains in the size range of 0.5–1.2 μm and 20–400 nm size Al2O3 particles dispersed uniformly in the 8YSZ. Fracture toughness and hardness of the composite was improved due to intragranular dispersion of Al2O3 particles. Electrical conductivity of the composite was 6.4×10−5 S cm−1 at 400°C and also exhibited significant increase over monolithic 8YSZ. Improvement in lattice conductivity was unique in this composite and attributed to the role of intragranular Al2O3 particles, which provided strong lattice distortion of 8YSZ matrix.