High temperature thermo-physical properties of and preparation of a novel thermal barrier coating Gd₂Zr₂O₇-8YSE

Gd₂Zr₂O₇ was prepared by solid state synthesis and its phase stability and thermo-physical properties were investigated. The Gd₂Zr₂O₇-8YSZ(8%Y₂O₃-ZrO₂) double-ceramic-layer thermal barrier coatings was prepared by electron beam physical vapour deposition. The crystal structure and atomic number ratio of the top coating were analysed. Results reveal that Gd₂Zr₂O₇ powders show excellent phase stability up to 1500℃, 250℃ higher as compared to the conventional 8YSZ.The coefficients of thermal expansion of the Gd₂Zr₂O₇ bulk ranges from 8.8×10^-6-11.0×10^-6 K^-1 at the temperature from 100 to 1500℃, which are comparable to that of the 8YSZ bulk.The thermal conductivities of the Gd₂Zr₂O₇ bulk are in a level of 1.0 W(m·K)^-1 at 1000-1400℃ and about 50% lower than that of the conventional 8YSZ. The as-deposited Gd₂Zr₂O₇ coating with pyrochlore structure has a stoichiometrical composition and exhibits a typical columnar grain structure.