Phase evolution and microstructure analysis of Al₂O₃–ZrO₂(Y₂O₃) eutectic powders with ultra-fine nanostructure

It is difficult to prepare high-quality eutectic particles with regular morphologies and fine microstructure by current technologies. In this work, the Al₂O₃–ZrO₂(Y₂O₃) eutectic powders with ultra-fine nanostructure is fabricated by a novel combustion synthesis combined with spray cooling (CS-SC) method. The phase structure and microstructure of eutectic particles with different Y₂O₃ content are discussed in details. The doping of Y₂O₃ inhibits the transformation of cubic-tetragonal and tetragonal-monoclinic during the solidification process, which gives rise to a rich variety of ZrO₂ polymorphs. Moreover, the microstructure of eutectic particles papered by CS-SC is independent of Y₂O₃ content, which are predominantly manipulated by cooling rate. The evolution of eutectic structure with particle size is also detailly analyzed. The cooling rate declines with the of particle size, which leads to increase of growth rate and consequently resulting in coarse structure. But all for this, the mean phase spacings of all particles remain nanoscale. The CS-SC has much higher growth rate and degree of supercooling than other solidification techniques. This work provides a basis for preparing Al₂O₃–ZrO₂(Y₂O₃) eutectic ceramics concurrent with large dimension and ultra-fine structure via sintering method.