Effect of Al₂O₃ addtion on phase structure of ZrO₂ in Al₂O₃-ZO₂ system

Abstract

The effect of Al₂O₃ addition on the phase structure of ZrO₂ in the Al₂O₃-ZrO₂ system was investigated. Al₂O₃-ZrO₂ composite powders with 15wt%, 50wt% or 85wt% Al₂O₃ were prepared by mixing α-alumina powder with Zr(OH)₄ gel that was synthesized by the precipitation method. The resulting mixtures were calcined for 2h at various temperatures from 400°C to 1300°C. At the addition of 85wt% Al₂O₃, metastable t-ZrO₂ with grain size of less than 11nm was obtained after calcinations at temperatures ranged from 500°C to 750°C, whereas at the addition of 15wt%, or 50wt% Al₂O₃, the volume fraction of monoclinic zirconia continuously increased with increasing calcination temperature. It is indicated that alumina with high content can effectively inhibit the nucleation and the grain growth of zirconia.