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

Abstract Synthesis of 8mol%Y 2 O 3 –ZrO 2 (8YSZ) powder with Al 2 O 3 by mechanical alloying (MA) and the sintering behavior of this powder were investigated. The solubility of Al 2 O 3 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.%Al 2 O 3 –8YSZ (3A8YSZ) consisted of 8YSZ grains in the size range of 0.5–1.2 μm and 20–400 nm size Al 2 O 3 particles dispersed uniformly in the 8YSZ. Fracture toughness and hardness of the composite was improved due to intragranular dispersion of Al 2 O 3 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 Al 2 O 3 particles, which provided strong lattice distortion of 8YSZ matrix.