High-entropy fluorite oxides: Atomic stabiliser effects on thermal-mechanical properties

• Published in: Journal of the European Ceramic Society Vol. 42; no. 14; pp. 6608 - 6613
• Main Authors: Liew, Siao Li, Ni, Xi Ping, Wei, Fengxia, Tan, Sze Yu, Luai, Meng Tzee, Lim, Poh Chong, Teo, Siew Lang, Rafiq, Nafisah Bte Mohd, Zhou, Jun, Wang, Shijie
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2022
• Subjects: Co-stabiliser; Coefficients of, thermal expansion; High-entropy fluorite oxides; Thermal Barrier Coating; Thermal conductivity; Thermal conductivity; Coefficients of, thermal expansion; Thermal Barrier Coating; High-entropy fluorite oxides; Co-stabiliser
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2022.07.026

High-entropy oxides Hf0.25Zr0.25Ce0.25Gd0.125X0.125O2-δ (X = Ca, Ti or Si) have been fabricated via solid-state reactions, in which the co-stabiliser X was intentionally chosen for its significant atomic mass and size difference from Gd. The single phase of these cubic fluorite oxides with dense microstructures has been confirmed by XRD, EDS and TEM characterizations. These phases are thermally stable without the appearance of secondary phase and phase separation within the temperature range studied (up to 1200 °C). Compared to yttria-stabilised zirconia (YSZ), which is used in the current commercial thermal barrier coatings, these fluorite oxides have higher coefficients of thermal expansion and lower thermal conductivities. They also exhibit comparable Young’s modulus and hardness with other reported high-entropy fluorite oxides. The fluorite oxides reported in this study are promising to improve the thermal expansion matching between ceramic topcoat and metal substrates for thermal barrier coating applications.