EFFECTS OF NANO-ZrO₂ ADDITIVE ON THE PHASE TRANSFORMATION AND DENSIFICATION OF ZrO₂-MgAl₂O₄ CERAMICS PREPARED BY SINGLE-STAGE SRS PROCESS

Abstract

A series of ZrO₂-MgAl₂O₄ ceramics with additions of 0, 2.5wt%, 5.0wt% and 7.5wt% nano-ZrO₂ were successfully fabricated at 1580 °C for 4 h from powders of commercial Al₂O₃ and calcined MgO by single-stage solid state reaction sintering (SRS) method. Effects of nano-ZrO₂ additive on the phase compositions, microstructures and bulk density of the ceramics were investigated. Nano-ZrO₂ additive was found to remarkably promote the sintering densification and improve the microstructure of the ceramics. Uniform, dense and fine microstructures are obtained, and the mean grain size of MgAl₂O₄ particles is about 2 μm. The as-prepared ceramics mainly consist of MgAl₂O₄ and c-ZrO₂ (cubic-Ca0.15Zr0.85O1.85), due to the reaction between Al₂O₃ and MgO as well as the nano-ZrO₂ additive and CaO stabilizer. The formation process of the ceramics mainly includes the synthesis of MgAl₂O₄ and the conversion process of m-ZrO₂ to c-ZrO₂ under the stabilizing action of CaO.

Keywords

• MgAl₂O₄
• Nano-ZrO₂
• Reaction sintering
• Phase transformation
• Densification