Perovskite‐Type Strontium Zirconate as a New Material for Thermal Barrier Coatings

Abstract

Perovskite‐type SrZrO 3 was investigated as an alternative to yttria‐stabilized zirconia (YSZ) material for thermal barrier coating (TBC) applications. Three phase transformations (orthorhombic↔pseudo‐tetragonal↔tetragonal↔cubic) were found only by heat capacity measurement, whereas the phase transformation from orthorhombic to pseudo‐tetragonal was found in thermal expansion measurements. The thermal expansion coefficients (TECs) of SrZrO 3 coatings were at least 4.5% larger than YSZ coatings up to 1200°C. Mechanical properties (Young's modulus, hardness, and fracture toughness) of dense SrZrO 3 showed lower Young's modulus, hardness, and comparable fracture toughness with respect to YSZ. The “steady‐state” sintering rate of a SrZrO 3 coating at 1200°C was 1.04 × 10 −9 s −1 , which was less than half that of YSZ coating at 1200°C. Plasma‐sprayed coatings were produced and characterized. Thermal cycling with a gas burner showed that at operating temperatures ∼1250°C the cycling lifetime of SrZrO 3 /YSZ double‐layer coating (DLC) was more than twice as long as SrZrO 3 coating and comparable to YSZ coating. However, at operating temperatures >1300°C, the cycling lifetime of SrZrO 3 /YSZ DLC was comparable to the optimized YSZ coating, indicating SrZrO 3 might be a promising material for TBC applications at higher temperatures compared with YSZ.