In Situ Diffraction Study of the High‐Temperature Decomposition of t′‐Zirconia. Issue 1 (26th September 2014)

• Record Type: Journal Article
• Authors: Krogstad, Jessica A.; Gao, Yan; Bai, Jianming; Wang, Jun; Lipkin, Don M.; Levi, Carlos G.; Sampath, S.
• Is Part Of: Journal of the American Ceramic Society. Volume 98:Issue 1(2015)
• Page Start: 247
• Page End: 254
• Publication Date: 2014-09-26
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.13249
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace13249-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The mechanisms of phase destabilization upon aging of the metastable <italic>t′</italic> 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<italic>t′‐</italic>8YSZ. 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 <italic>T</italic>₀(<italic>c/t</italic>) temperature for <italic>t′‐</italic>8YSZ is estimated to be 1640°C. Full decomposition of the <italic>t′</italic> phase into a coherent mixture of a Y‐lean tetragonal phase (<italic>t</italic>) and a Y‐rich cubic phase (<italic>c</italic>) that coarsen over time is observed at elevated temperatures; however, upon quenching, the <italic>t′</italic> phase reappears in the diffraction profile. This supports our evolving understanding that the <italic>t′</italic> phase observed by XRD in aged samples is a microstructural artifact due to the coherency strain between the <italic>t</italic> and <italic>c</italic> phases.</p> </abstract>