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 (orthorhombic2pseudo-tetragonal2tetragonal2cubic) 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 12001C. 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 ''steadystate'' sintering rate of a SrZrO 3 coating at 12001C was 1.04 Â 10 À9 s À1 , which was less than half that of YSZ coating at 12001C. Plasma-sprayed coatings were produced and characterized. Thermal cycling with a gas burner showed that at operating temperatures B12501C 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 413001C, 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.

Partial Evaporation of Strontium Zirconate During Atmospheric Plasma Spraying

“…Perovskitetype SrZrO 3 has been investigated as candidate TBCs material. Details of SrZrO 3 are published in literature ( Ref 1,2), and Table 1 summarizes its thermophysical properties.…”

Microstructure design for blended feedstock and its thermal durability in lanthanum zirconate based thermal barrier coatings

“…There were many trials to overcome the limitation of current YSZ material, such as zirconates, perovskites, and hexaaluminates [6,[10][11][12]. Among them, zirconates which contain rare-earth elements have been investigated as a new material for advanced TBCs in higher operating temperatures above 1200 o C. Especially, lanthanum zirconate (La2Zr2O7: LZO) has significantly lower thermal conductivities than YSZ.…”

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

“…[54,[75][76][77][78][79][80] The lanthanide cerates have thermal conductivities in the upper range of those of YSZ and higher than those of the lanthanide zirconates, [75,76] but can be decreased with doping (e.g., (Sm 1Àx Dy x ) 2 Ce 2 O 7 ). [76] The thermal conductivity of La 2 Hf 2 O 7 , however, is lower than that of La 2 Zr 2 O 7 , which has been attributed to reduction in the phonon velocity due to the lower elastic modulus of La 2 Hf 2 O 7 .…”

“…[76] The thermal conductivity of La 2 Hf 2 O 7 , however, is lower than that of La 2 Zr 2 O 7 , which has been attributed to reduction in the phonon velocity due to the lower elastic modulus of La 2 Hf 2 O 7 . [81] The thermal conductivities of strontium zirconate [54,77,78] and strontium hafnate [79] are in a similar range (i.e., upper range of YSZ), but can be decreased by creating defects with yttrium and ytterbium doping.…”