Microstructure and property evolution of Gd3NbO7-GdNbO4 composite thermal barrier coating

• Published in: Journal of the European Ceramic Society 2025-03, Vol.45 (3), p.117026, Article 117026
• Main Authors: Lu, Yang, Sun, Jian, Liu, Guanghua, Liu, Wei, Liu, Xiangyang, Pan, Wei, Wan, Chunlei
• Format: Article
• Language: English
• Subjects: Fracture toughness; Gd3NbO7-GdNbO4; Sintering; Thermal barrier coatings; Thermal property
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2024.117026

To fulfill the multi-functional requirements of advanced thermal barrier coatings, composite oxides are emerging as promising candidates due to their enhanced thermal and mechanical properties. Although numerous composite materials have been developed, a comprehensive investigation of their microstructure and property evolution is still lacking. In this study, we conducted a comprehensive investigation of the microstructure and property evolution of the Gd3NbO7-GdNbO4 composite thermal barrier coating as a case study. The as-sprayed Gd3NbO7-GdNbO4 coating was verified to possess a single fluorite phase with a composition of NbxGd(1-x)O(1.5+x), which is a metastable phase. After heat treatment, the monoclinic GdNbO4 phase precipitated without altering the coating microstructure. During high-temperature thermal exposure, rapid sintering occurred, accompanied by grain coarsening and pore healing, leading to an increase in hardness and toughness. The toughness of the Gd3NbO7-GdNbO4 coating was higher than that of rare earth zirconates due to the presence of multiple toughening mechanisms. Additionally, a low thermal conductivity of 1.33 W/(m·K) was achieved for the Gd3NbO7-GdNbO4 coating due to rapid sintering. Notably, there were no abrupt changes in the CTE curves during the heating process, which is crucial for thermal barrier coatings. The CTE reaches 11.0×10−6 K−1 at 1300 °C, which is close to YSZ, indicating that the Gd3NbO7-GdNbO4 coating is suitable for advanced thermal barrier coatings.