Influence of Gd2O3 substitution on thermal and mechanical properties of ZrO2-Ta2O5-Y2O3

The effects of the partial Y2O3 substituted by Gd2O3 on thermal and mechanical properties of ZrO2-Ta2O5-Y2O3 ceramics were studied. Results indicated the single stable tetragonal phase of zirconia co-doped with 16 mol% YO1.5 +16 mol% TaO2.5 (YTZ) and zirconia co-doped with (16-x) mol% YO1.5+ x mol% GdO1.5+16 mol% TaO2.5 (xGYTZ, x = 2, 4, 8) just existed at and above 1500 degrees C. The Gd2O3 substitution caused a decrease in phase stability when annealed at 1300 degrees C and 1400 degrees C. YTZ and 2GYTZ ceramics exhibited high fracture toughness, large thermal expansion coefficients (TECs), and low thermal conductivity. With the Gd2O3 substitution, the mechanical properties and thermal conductivity showed a decreasing trend, while TECs increased due to the decrease of crystal energy. The thermal durability of YTZ and 2GYTZ TBCs was evaluated. The cycling life of 2GYTZ TBCs was much shorter. The combination of sintering effect and thermal expansion mismatch stresses was significant factor for the failure.