Influence of microwave heating on grain growth behavior and phase stability of nano Y2O3/La2O3 co-doped ZrO2 ceramics

Abstract

Y2O3-doped ZrO2 (YSZ) is a significant structural material and excellent functional material, it has been widely used in fields such as ceramics, thermal barrier coatings, and medical, etc. The disadvantage of YSZ is that it undergoes phase transition occurs during high-temperature cooling, leading to cracks in zirconia. It is worth mentioning that the failure phase transition of YSZ can be suppressed by the addition of rare earth oxide such as lanthanum oxide. In this paper, ZrO2 nano-powders with 0.2 mol% La2O3-2.8 mol% Y2O3 were prepared by a high-energy ball milling method. The comparison of microwave sintering and conventional sintering temperatures (800 °C–1300 °C) on the phase transition transformation of La2O3-doped Y2O3-stabilized zirconia powders was investigated by the control variable method. Meanwhile, the effects of microwave sintering technology on the microstructure and grain growth behavior of the sintered powders were further analyzed. The results show that microwave sintering is superior to conventional sintering technology. Microwave sintering promotes the rate of conversion of zirconia from monoclinic to tetragonal phase. Furthermore, the average grain size of the samples increased linearly with increasing temperature, and the grain growth further contributed to the presence of stable phases. Adding La3+ and Y3+ can reduce the grain growth activation energy and increase the contents of both the t-ZrO2 and c-ZrO2 in the sample. In this experiment, we find that the samples sintered best at 1200 °C with stable phase composition, well-defined morphology and uniform particle distribution. It is well known that the synthesis of high-quality zirconia materials is essential for good zirconia raw materials in practical production. This study provides an experimental and theoretical basis for the synthesis of zirconia powder with excellent performance.