Improvement on the phase stability, mechanical properties and thermal insulation of Y₂O₃-stabilized ZrO₂ by Gd ₂O₃ and Yb₂O₃ co-doping

Gd₂O₃ and Yb₂O₃ co-doped 3.5 mol% Y₂O₃-ZrO₂ and conventional 3.5 mol% Y ₂O₃-ZrO₂ (YSZ) powders were synthesized by solid state reaction. The objective of this study was to improve the phase stability, mechanical properties and thermal insulation of YSZ. After heat treatment at 1500 C for 10 h, 1 mol% Gd₂O₃-1 mol% Yb ₂O₃ co-doped YSZ (1Gd1Yb-YSZ) had higher resistance to destabilization of metastable tetragonal phase than YSZ. The hardness of 5 mol% Gd₂O₃-1 mol% Yb₂O₃ co-doped YSZ (5Gd1Yb-YSZ) was higher than that of YSZ. Compared with YSZ, 1Gd1Yb-YSZ and 5Gd1Yb-YSZ exhibited lower thermal conductivity and shorter phonon mean free path. At 1300 C, the thermal conductivity of 5Gd1Yb-YSZ was 1.23 W/m K, nearly 25% lower than that of YSZ (1.62 W/m K). Gd₂O₃ and Yb ₂O₃ co-doped YSZ can be explored as a candidate material for thermal barrier coating applications.