Effect of Gd2O3 on the microstructure and thermal properties of nanostructured thermal barrier coatings fabricated by air plasma spraying

The nanostructured 4–8 mol% Gd2O3-4.5 mol% Y2O3-ZrO2（4–8 mol% Gd YSZ） coatings were developed by the atmospheric plasma spraying technique. The microstructure and thermal properties of plasmasprayed 4–8 mol% Gd YSZ coatings were investigated. The experimental results indicate that typical microstructure of the as-sprayed coatings were consisted of melted zones, nano-zones, splats, nano-pores,high-volume spheroidal pores and micro-cracks. The porosity of the 4, 6 and 8 mol% Gd YSZ coatings was about 9.3%, 11.7% and 13.3%, respectively. It was observed that the addition of gadolinia to the nano-YSZ could significantly reduce the thermal conductivity of nano-YSZ. The thermal conductivity of Gd YSZ decreased with increasing Gd2O3 addition. And the reduction in thermal conductivity is mainly attributed to the addition of Gd2O3, which results in the increase in oxygen vacancies, lattice distortion and porosity.