Thermal conductivity of plasma sprayed Sm2Zr2O7 coatings

Rare-earth zirconates with a pyrochlore structure have been developed for potential application in thermal barrier coating systems to further improve the performance and durability of gas turbines. The Sm2Zr2O7 (abbreviated as SZ) powder was synthesized by solid state reaction and then deposited by air plasma spraying. The phase stability, microstructure and thermal conductivity of SZ and 8 wt% Y2O3 stabilized zirconia (8YSZ) coatings were investigated. The X-ray diffraction results indicated that the crystal structure of the as-sprayed SZ coatings was defect-fluorite, and after heat treating at 1200 °C for 50 h, it started to transform to pyrochlore, and the content of pyrochlore increased with increase in temperature of the heat treatment. The thermal conductivities of SZ coatings were significantly lower than those of 8YSZ coatings before and after heat treatments, which increased considerably after heat treatments compared to the as-sprayed states for both coatings due to sintering effects.