Dynamic formation of zircon during high temperature deformation of zirconia–silica composites with alumina additions

摘要

A three phase ceramic composite of 8 mol% Y2O3 stabilized ZrO2 (YSZ), SiO2, and Al2O3 was evaluated for potential high temperature superplasticity. The amorphous SiO2 content was 5 wt.%, and increasing additions of Al2O3 were made. The effect of varying the Y2O3 stabilizer concentration in ZrO2 was also studied. Samples sintered at 1200 °C contained only YSZ, Al2O3, and amorphous SiO2, but ZrSiO4 formed in the samples above 1300 °C. Mullite (3Al2O3 · 2SiO2) was not detected in any samples. Specimens of 1 wt.% Al2O3–YSZ/SiO2 had an anomalously high deformation rate of ～2 × 10?4 s?1 at 1200 °C when compared to YSZ/SiO2 without Al2O3 (～4 × 10-5 s?1). Higher amounts of Al2O3 additions decreased the strain rate. Extensive deformation of Al2O3 doped YSZ/SiO2 at 1200 °C induced the formation of ZrSiO4 due to enhanced reaction rates. This distributed, yet locally interconnected, zircon phase rapidly eroded the strain rate after ～60% deformation.