NdAlO3-Nd2Zr2O7 composite with eutectic composition for advanced nanostructured thermal insulation coatings

Though numerous novel materials have been discovered as potential materials for thermal barrier coatings, their either relative poor strain tolerance or high thermal conductivity limited their further application. In the present work, a NdAlO3-Nd2Zr2O7 composite coating is prepared by air plasma spraying process. Glass phase appears in the composite coating and crystallizes after thermal exposure at 1000 degrees C for 5 h. This crystallization process leads to the severe reduction of the thermal expansion rate. Additionally, thermal conductivity of as-sprayed NdAlO3-Nd2Zr2O7 coating is about 1.0 Wm(-1) K-1 but increases to 1.7 Wm(-1) K-1 after heat treatment. A quite stable nanostructured thermal barrier coating is obtained after heat treatment. Remarkably, the NdAlO3-Nd2Zr2O7 composite coating exhibits a superior microstructure stability that the average grain size remains less than 100 nm, 175 nm, and 250 nm after calcined at 1100 degrees C, 1200 degrees C, and 1300 degrees C for more than 100 h, respectively. The fracture toughness of NdAlO3-Nd2Zr2O7 composite coating is one of the highest among the novel thermal barrier coatings owing to the existence of super-fine grains. The present study brings some new insight in designing advanced stable nanostructured thermal insulation coatings.