Cr-doped Al2O3–YAG binary and Al2O3–YAG–ZrO2 ternary eutectic materials crystallized by the micro pulling down technique and their characterization

Abstract

Cr-doped Al₂O₃–YAG and Al₂O₃–YAG–ZrO₂ eutectic ceramics rods of 3 mm in diameter were solidified from the melt by a micro-pulling down (μ-PD) technique. The Cr dopant affects the microstructure, morphology, and lattice parameters of the as-grown eutectics. As a function of the dopant, the coloration, morphology, microstructure, and luminescence were investigated. Whatever the Cr-dopant concentration, mainly two phases (Al₂O₃–YAG) in the case of the binary system and three phases (Al₂O₃–YAG–ZrO₂) in the case of the ternary system were observed. The Chinese script microstructure and colony boundaries are observed in ternary eutectics. Al₂O₃ and YAG phases show faceted morphologies, but for the ZrO₂ phase, growth tends to a weakly faceted manner and forms rods or lamellae. The hydrostatic stress of binary eutectics is less than that of ternary eutectics with same Cr dopant concentration due to the distribution of ZrO₂ particles in the microstructure affected by residual stresses. The spectroscopic properties of the Cr-doped binary and ternary eutectic show that Cr³⁺ ions exist in both Al₂O₃ and YAG phases in octahedral sites.