A comparison of the thermal properties of ZrO2-Ln2O3 (Ln – Y, La, Nd, Sm, Gd) thermal barrier coatings

In this work we are to report the results of our recent development in the field of powder synthesis and coating production with zirconia-based compositions and their thermal properties investigation. Four solid solutions and four “stoichiometric” phases from the ZrO₂-Ln₂O₃ (Ln – Y, La, Nd, Sm, Gd) systems were chosen for comparison.

Thermal conductivity of all as-sprayed coatings was shown to be very low (0.35-0.90 W/m·K at 1000°C). During the heat treatment the processes of microstructure evolution, crystal structure ordering and phase transition occurred strongly affecting the thermal properties of coatings (especially in the first ~24 hours). This “initial growth” value is completely different for all thermal barrier coating compositions and microstructures. The present paper focuses on defining the key factors responsible for the difference of 50% to 250% in the coating thermal conductivity growth at the same heat treatment conditions.