Lanthanum zirconate thermal barrier coatings deposited by spray pyrolysis

The fabrication of thick nanostructured lanthanum zirconate thermal barrier coatings deposited by spray pyrolysis from aqueous nitrate based precursor solutions is presented. After deposition, the green coatings are decomposed to introduce vertical cracks which are beneficial to enhance the thermo-mechanical compliance of the coatings. The cracks were stable after crystallization of the coatings to the cubic pyrochlore structure by further heat-treatment. Nanocrystalline mono- and multi-layered coatings with contrasting crack patterns were produced based on the knowledge of the influence of the different parameters. Multilayered coatings with small crack spacing and crack opening exhibited a higher density, a lower thermal diffusivity, and a higher thermal conductivity of ~ 0.34 W/(m·K) at elevated temperatures compared to monolayered coatings of similar thickness with larger crack spacing and crack opening. The low thermal properties of the crystalline coatings were attributed to the nanostructure of the coatings.