The effect of cerium doping and rate of crystallization on the microstructure of the Al2O3/YAG eutectic composite

TL;DR

This study investigates how cerium doping and crystallization rate influence the microstructure of Al2O3/YAG eutectic composites, revealing critical conditions for high homogeneity and structural stability during directional crystallization.

Contribution

It provides new insights into the effects of cerium doping and crystallization rate on eutectic microstructure, including deviations from classical models and conditions for optimal homogeneity.

Findings

Deviation from Jackson-Hunt model observed

Critical pooling rate identified for morphological stability

High cerium concentration leads to third phase formation

Abstract

Eutectics of Sapphire/Yttrium-Aluminum garnet and Ce-doped Sapphire/Yttrium-Aluminum garnet (Ce up to 1 at.%) with a Chinese script microstructure were obtained by the method of horizontal directional crystallization in a carbon-containing reducing atmosphere based on argon gas. The effects of the pooling rate and Ce-dopant concentration on the microstructure of the eutectic were studied by the modified chord method. The deviation of the dependence of the characteristic eutectic distance on the pooling rate from the Jackson-Hunt model has been established. A change in the pathway for restructuring the structure of the doped eutectic at a certain critical pooling rate was revealed, which may indicate that the development of morphological instability of the crystallization front is carried out as a two-stage process. The conditions for obtaining doped eutectic of high homogeneity have been established. It was shown that increasing cerium ion concentration causes an increase in the structure parameters and its value deviation. Intensive formation of the third phase occurred when the limit of cerium ion concentration was exceeded.