Fracture toughness degradation of rare earth zirconate-yttria-stabilized zirconia (RE = Sm and Gd) composite after high-temperature treatment

Thermal barrier coatings are mandated to exhibit exceptional mechanical properties, particularly high toughness, for enhanced thermal cycling durability. However, many newly developed materials exhibit low fracture toughness, limiting their performance. To address this challenge, composite coatings have emerged as a strategic approach to enhance thermal shock resistance. This study delves into the toughening influence of yttria-stabilized zirconia (YSZ) on rare earth zirconate (RE₂Zr₂O₇, REZ) composites (RE = Sm or Gd). After sintering at 1300°C for 100 h, the absence of a monoclinic phase in REZ-YSZ is attributed to the diffusion of rare earth elements into YSZ. Notably, while REZ-YSZ composite coatings exhibit higher fracture toughness initially, they experience a decline in this property with prolonged sintering time. Our research highlights a significant finding in the development of YSZ-toughened TBC materials.