|About this Abstract
||Materials Science & Technology 2019
||Phase Transformations in Ceramics: Science and Applications
||Phase Transformations in High-entropy, Lanthanide Oxides
||Kuo-Pin Tseng, Waltraud M. Kriven, Ming-Hung Tsai
|On-Site Speaker (Planned)
Oxides of the lanthanides can experience phase transformations as a function of temperature and oxidation state. Most of lanthanide cations are trivalent under ambient conditions. However, some cations tend to be tetravalent (e.g. Ce) or coexist in both trivalent and tetravalent states (e.g. Tb). In high-entropy ceramics, the high-temperature phase transformation can be driven by the preferred oxidation states of its constituent cations. In this study, in-situ heating synchrotron data of two high-entropy lanthanide systems were collected up to 1600C. It finds that the ratio of trivalent to tetravalent states plays an important role in the occurrence of phase transformation. When the ratio is lower than 20%, the random arrangement of multi-cations can inhibit the phase transformations, e.g. Gd0.4Tb0.4Dy0.4Ho0.4Er0.4O3. However, the high temperature phase transformation can initiate as the ratio exceeds 50%, causing phase separation. This finding introduces a chemical selection mechanism for designing structurally stable, refractory, high-entropy ceramics.
||Definite: At-meeting proceedings