Effect of Y0.5Er0.5Ho0.5Yb0.5O3 addition on the microstructure and thermal stability of continuous alumina fibers

Continuous alumina fibers with excellent thermal stability are essential in high-temperature applications. In this study, 0~1 wt% Y 0.5 Er 0.5 Ho 0.5 Yb 0.5 O 3 were added to the alumina fibers to enhance thermal stability. The impact of Y 0.5 Er 0.5 Ho 0.5 Yb 0.5 O 3 addition on alumina fibers’ transformation and microstructure evolution of during the sintering process was systematically studied. The influence of single- and two-step sintering processes on the fiber microstructures was elucidated. The results suggested that adding Y 0.5 Er 0.5 Ho 0.5 Yb 0.5 O 3 impeded fiber densification, inhibited alumina grain growth, and enhanced the thermal stability of fibers. Using a two-step sintering process facilitated the achievement of fully dense alumina fibers with fine grains. The alumina fibers added with 1.0 wt% Y 0.5 Er 0.5 Ho 0.5 Yb 0.5 O 3 exhibited a remarkable strength retention rate of up to 93% after exposure to 1200 °C for 10 h. The TEM analysis revealed that rare earth elements segregation at α-Al 2 O 3 grain boundaries due to their larger radius than the Al element contributed to stabilizing the microstructures of α-Al 2 O 3 fibers at high service temperature. Graphical Abstract