Yb2O3 and Gd2O3 doped strontium zirconate for thermal barrier coatings

Yb2O3 (10 mol%) and Gd2O3 (20 mol%) doped SrZrO3 was investigated as a material for thermal barrier coating (TBC) applications. The thermal expansion coefficients (TECs) of sintered bulk Sr(Zr0.8Yb0.1)O-2.95 and Sr(Zr0.8Gd0.2)O-2.9 were recorded by a high-temperature dilatometer and revealed a positive influence on phase transformations of SrZrO3 by doping Yb2O3 or Gd2O3. The results for the thermal conductivities of Sr(Zr0.9Yb0.1)O-2.95 and Sr(Zr0.8Gd0.2)O-2.9 indicated that both dopants can reduce the thermal conductivity of SrZrO3. Mechanical properties (Young's modulus, hardness, and fracture toughness) of dense Sr(Zr0.9Yb0.1)O-2.95 and Sr(Zr(0.8)d(0.2))O-2.9 showed lower Young's modulus, hardness and comparable fracture toughness with respect to YSZ. The cycling lifetimes of Sr(Zr0.9Yb0.1)O-2.95/YSZ and Sr(Zr0.8Gd0.2)O-2.9/YSZ double layer coatings (DLC), which were prepared by plasma spraying, were comparable to that of YSZ at operating temperatures <1300 degrees C. However, the cycling lifetime of Sr(Zr0.9Yb0.1)O-2.95/YSZ DLC was similar to 25% longer, whereas Sr(Zr0.8Gd0.2)O-2.9/YSZ DLC had a shorter lifetime compared to the optimized YSZ coating at operating temperatures >1300 degrees C. (c) 2008 Elsevier Ltd. All rights reserved.