Evolution of microstructure and properties of Ba(Mg_1/3Ta_2/3)O₃ thermal barrier material exposed to CMAS corrosion

Calcium-magnesium-alumina-silicate (CMAS) resistance has become a key parameter to evaluate the properties of thermal barrier coating (TBC) materials. The CMAS corrosion behavior of BMT ceramic as a novel candidate material for TBC is poorly understood. In this paper, the solid-state sintering process was used to prepare the BMT bulks, and the evolution of microstructure, phase composition, thermophysical properties, and mechanical properties of the BMT bulks exposed to CMAS corrosion were studied. The results indicate that obvious elemental interdiffusion between the CMAS melt and BMT occurred at 1250 °C, which changed the original phase composition and formed multiple substances including Ba(Al, Ca)Si₂O₈, Ba₂MgSi₂O₇, BaTa₂O₆, Ba₂Si₄O₁₀, etc. The microstructure of BMT also underwent changes due to differences in the diffusion coefficients of different elements. As corrosion time prolongs, an obvious porous columnar reaction layer formed on the sample surface, causing the CMAS melt to sustainably corrode the deep BMT, resulting in intragranular corrosion. In terms of properties, the thermophysical and mechanical properties of the BMT bulks corroded by CMAS deteriorated. The thermal conductivity at 1100 °C increased from 1.43 W m⁻¹ · k⁻¹ to 1.67 W m⁻¹ · k⁻¹. The average coefficient of thermal expansion at 200–1400 °C decreased from 11.60 × 10⁻⁶ K⁻¹ to 10.95 × 10⁻⁶ K⁻¹. The hardness dropped by 21 % compared to the original BMT bulk. Therefore, it is necessary to improve the CMAS resistance of BMT ceramic in future studies.