Lanthanum-cerium oxide thermal barrier coatings prepared by atmospheric plasma spraying

Lanthanum-cerium oxide (La₂Ce₂O₇, LC) thermal barrier coatings (TBCs) were prepared by atmospheric plasma spraying (APS). The actual composition of the as-sprayed coating is La₂Ce_1.66O_4.32, due to the volatilization of CeO₂ phase during the spray process. A little decomposition of the LC coating takes place after annealing at 1400°C for 240 h. The thermal conductivity of bulk LC material is about 0.51 W/(m·K) at 1000°C, which is one fourth of that of typical bulk YSZ. The coefficient of thermal expansion (CTE) of the LC coating ranges from 10×10^-6 K^-1 to 13×10^-6 K^-1 at the temperature from 450°C to 1100°C, which is relatively higher than that of the YSZ coating. Dilatometric measurements show that there is slight shrinkage in the coating till 1250°C, however, a remarkable sintering process happens during holding period at 1250°C. A spallation of the LC TBC occurs after 60 cycles at 1100°C by typical delaminating cracking within the LC topcoat.