High-temperature elemental segregation induced structure degradation in high-entropy fluorite oxide

• DOI: 10.26599/jac.2024.9220854
• Publication Date: 2024-01-19T02:18:18Z
• Authors: Yixuan Hu; Mariappan Anandkumar; Yumeng Zhang; Joydip Joardar; Atul Suresh Deshp...; Xiaodong Wang; Kolan Madhav Reddy
• Keywords: Bixbyite; Fluorite; Superstructure

Fluorite-structured oxides constitute an important category of with a wide range high-temperature applications. Following the concept high entropy, high-entropy fluorite (HEFOs) have showcased intriguing application potential. However, unlocking this potential necessitates assessment their long-term stability under conditions. In study, we conducted prolonged heat treatment at 1000 °C on typical HEFO, specifically (CeHfZrGdLa)O_x. After 100 hours, intensity X-ray diffraction (XRD) revealed transition from single-phase to multi-phase configuration. Further investigation by analytical electron microscopes (AEMs) demonstrated that degradation resulted facilitated element diffusion and consequent escalating chemical fluctuation temperatures, leading spontaneous segregation separation Ce La elements, forming Ce-rich, La-poor, La-rich phases. Notably, phase spontaneously transformed structure (space group Fm-3m) bixbyite Ia-3) elevated resulting in appearance superstructure reflection XRD profiles patterns. Despite intricate decomposition, energy band gap showed minimal variation, suggesting property (CeHfZrGdLa)O_x across broad compositions. These findings offer valuable insights into future applications HEFOs.