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. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.