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In Situ Diffraction Study of the High‐Temperature Decomposition of t′ ‐Zirconia
Author(s) -
Krogstad Jessica A.,
Gao Yan,
Bai Jianming,
Wang Jun,
Lipkin Don M.,
Levi Carlos G.
Publication year - 2015
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.13249
Subject(s) - materials science , yttria stabilized zirconia , thermal expansion , phase (matter) , tetragonal crystal system , diffraction , cubic zirconia , thermal decomposition , x ray crystallography , metastability , crystallography , analytical chemistry (journal) , chemistry , composite material , optics , ceramic , physics , organic chemistry , chromatography
The mechanisms of phase destabilization upon aging of the metastable t′ phase of yttria‐stabilized zirconia ( YSZ ) are poorly understood, despite its broad application in thermal barrier coatings. To provide insight, synchrotron X‐ray diffraction ( XRD ) with a quadrupole lamp furnace is used to examine the temperature response, including thermal expansion and phase evolution, of a 9 mol% (8 wt%) YO 1.5 t′‐ 8 YSZ . The thermal expansion of equilibrated YSZ powders ranging from 0 to 18.4 mol% YO 1.5 is also investigated to better understand the effect of composition on the thermal expansion anisotropy. The T 0 ( c/t ) temperature for t′‐ 8 YSZ is estimated to be 1640°C. Full decomposition of the t′ phase into a coherent mixture of a Y‐lean tetragonal phase ( t ) and a Y‐rich cubic phase ( c ) that coarsen over time is observed at elevated temperatures; however, upon quenching, the t′ phase reappears in the diffraction profile. This supports our evolving understanding that the t′ phase observed by XRD in aged samples is a microstructural artifact due to the coherency strain between the t and c phases.