Experimental and theoretical study on the complete phase separation of ceria-zirconia solid solution into two end members, ceria and zirconia. (1st October 2022)

• Record Type: Journal Article
• Authors: Oh, Seol Hee; Kim, Hyun-Kyu; Kim, Jason; Kim, Yeong-Cheol; Park, Sun-Young; Yang, Sungeun; Ji, Ho-Il; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho
• Is Part Of: JPhys energy. Volume 4:Number 4(2022)
• Publication Date: 2022-10-01
• Subjects: Ce0.75Zr0.25O2 -- ceria-zirconia solid solution -- phase stability -- complete dissociation -- enhanced cation diffusion; Power resources -- Research -- Periodicals; Power resources -- Periodicals; 333.79
• DOI: 10.1088/2515-7655/ac8a76
• Languages: English
• ISSNs: 2515-7655

Abstract

Abstract: Solid solution CeO2 –ZrO2 has long been used as a non-noble metal oxide promoter for three-way catalysts owing to its high oxygen storage capacity. However, the stability issue of the CeO2 –ZrO2 has been controversial for a long time. In particular, the phenomena observed by phase instability are so diverse and inconsistent that the related causal analysis is still a matter of debate. In this study, for the first time, it was demonstrated theoretically and experimentally that a Ce0.75 Zr0.25 O2 (CZO) solid solution must be completely separated into CeO2 and ZrO2 phases owing to its inherent thermodynamic instability. According to an extensive evaluation via defect chemical calculations and well-controlled model experiments with grain-boundary-free epitaxial thin film samples, CZO materials undergo phase separation until they are completely separated, and the separation rate is particularly high in a reducing atmosphere. The underlying inherent stability problem and enhanced phase separation kinetics of the CZO material are attributed to the enhanced cation diffusion in a reducing atmosphere, where more mobile cationic defects (interstitial cations) are generated and an easier pathway with a lower migration energy is available.