Phase stability and thermal conductivity of RE2O3 (RE=La, Nd, Gd, Yb) and Yb2O3 co-doped Y2O3 stabilized ZrO2 ceramics

Y2O3 stabilized ZrO2 (YSZ) has been considered as the material of choice for thermal barrier coatings (TBCs), but it becomes unstable at high temperatures and its thermal conductivity needs to be further reduced. In this study, 1 mol% RE2O3 (RE=La, Nd, Gd, Yb) and 1 mol% Yb2O3 co-doped YSZ (1RE1Yb-YSZ) were fabricated to obtain improved phase stability and reduced thermal conductivity. For 1RE1Yb-YSZ ceramics, the phase stability of metastable tetragonal (t′) phase increased with decreasing RE3+ size, mainly attributable to the reduced driving force for t′ phase partitioning. The thermal conductivity of 1RE1Yb-YSZ was lower than that of YSZ, with the value decreasing with the increase of the RE3+ size mainly due to the increased elastic field in the lattice, but 1La1Yb-YSZ exhibited undesirably high thermal conductivity. By considering the comprehensive properties, 1Gd1Yb-YSZ ceramic could be a good potential material for TBC applications.