Microstructure and growth characteristics of Al2O3/Er2O3/ZrO2 solidified ceramics with different compositions

Abstract

Directionally solidified Al2O3/Er2O3/ZrO2 ceramics were prepared with high frequency induction zone melting. Their phase components, microstructure and growth characters were investigated. The results indicated that the raw material powder with uniform oxides’ distribution could be obtained via the green body’s crushing and second ball-milling, which was benefited to get the fined and unified eutectic microstructure. The phase components of each sample were consistent with the prediction originated from the position of their composition in the phase diagram. The microstructures of eutectic and hyper/hypo-eutectic were basically a network with interpenetrated crystal phases, and a small amount of coarsened phase existed in the form of colony structure in the latter, the microstructure was refined with the increase of the ZrO2 concentration. The quasi-eutectic with colony structure could be prepared at the molar ratio of raw materials determined by the volume fraction. In addition, a large number of coarsened phases appeared in the microstructures of the samples with the eutectic molar ratios, so the corresponding samples were non-eutectic. These results demonstrated that the composition might be more important than the growth rate in the preparation of non-eutectic samples with eutectic microstructure, and the selection of the composition of solidified ceramics should not depend too much on the phase diagram. The eutectic growth could be divided into four processes according to the microstructures of precursor and solidified ceramics.