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Atomic-scale insights into CMAS-induced grain boundary embrittlement in thermal barrier ceramics

Year: 2025
Type: article
Abstract: We report a study on grain boundary (GB) embrittlement in yttria stabilised zirconia (YSZ) ceramics induced by calcia-magnesia-alumino-silicate (CMAS). Model ceramics composed of tetragonal YSZ grains and intergranular CMAS were fabricated through sintering of YSZ-CMAS powder mixtures with incremental CMAS additions up to 1 wt%. Microstructural characterisations reveal that, although glassy CMAS films are present at triple junctions and between YSZ grains, most GBs are free of glassy films but enriched with CMAS-derived impurities. As the CMAS content increases the fracture toughness drops significantly, and the fracture mode shifts increasingly towards intergranular. Fractographic analysis at the atomic scale shows that fractures occur within the cores of glass-free GBs, whereas in GBs containing glassy CMAS films, fractures occur at the CMAS/YSZ interface, where a 2 nm layer of monoclinic YSZ is present. The CMAS-induced grain boundary embrittlement is explained from the perspective of fracture energy, with contributions from GB energy, ionic bonding, oxygen vacancies and ionic size mismatch taken into consideration.
DOI: 10.1016/j.jeurceramsoc.2025.117472
Language: English
Open Access status: hybrid
Estimated APC paid: $3,900
Funders: Henry Royce Institute, Royal Academy of Engineering, Rolls-Royce, University of Manchester, Engineering and Physical Sciences Research Council, Innovate UK
Awards: Digital Qualification Platform for Advanced Alloy Components, Sir Henry Royce Institute - Manchester and NNL Equipment, Sir Henry Royce Institute - Manchester Build, The Royce: Capitalising on the investment, G6971754719, Sir Henry Royce InsStitute - recurrent grant
OpenAlex ID: W4409644733
FWCI: 0.799
Cites: 61
Cited by: 2
Related to: 10