Phase stability and thermal conductivity of ytterbia and yttria co-doped zirconia

Rare earth oxides doping has been extensively investigated as one of the effective methods to lower thermal conductivity of 4.55 mol% Y2O3 stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs). In the present work, 5–6 mol% Yb2O3 and Y2O3 co-doped ZrO2 ceramics were synthesized by solid reaction sintering at 1600 °C. The phase stability of the samples after heat treatment at 1500 °C was investigated. Yb2O3 and Y2O3 co-doped zirconia, especially when Yb2O3/Y2O3≥1, contained less monoclinic phase than single Yb2O3 or Y2O3 phase doped zirconia, indicating that co-doped zirconia was more stable at high temperature than YSZ. The thermal conductivity of the 3 mol% Yb2O3+3 mol% Y2O3 co-doped ZrO2 was 1.8 W m−1 K−1 at 1000 °C, which was more than 20% lower than that of YSZ.