Thermo-mechanical properties of ThO2-doped Y2O3 stabilized ZrO2 for thermal barrier coatings

A series of ThO2-doped Y2O3 stabilized ZrO2 monolith compounds were prepared and investigated. The bigger ionic radius of Th4+ substitutions dilutes the average oxygen coordination to the cations, which is the determinant factor of the phase stability. Therefore, ThO2 incorporation has a strong impact on the phase composition, and consequently on the thermo-mechanical properties of the specimens. The metastable t′ phase was stabilized in light-doped specimens with a decreasing tetragonality while the thermodynamic equilibrium t phase and the related martensitic t–m phase transformation were absent in ThO2-doped specimens. Additionally, lower thermal conductivity was also achieved due to the substitutional phonon scattering effect. Considering the phase stability and thermo-mechanical properties, ThO2-doped Y2O3 stabilized ZrO2 compounds may be promising candidates for thermal barrier coatings although further research may be needed to improve their mechanical properties.