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Phase Evolution upon Aging of Air Plasma Sprayed t′‐Zirconia Coatings: II –Microstructure Evolution
Author(s) -
Krogstad Jessica A.,
Leckie Rafael M.,
Krämer Stephan,
Cairney Julie M.,
Lipkin Don M.,
Johnson Curtis A.,
Levi Carlos G.
Publication year - 2013
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/j.1551-2916.2012.05460.x
Subject(s) - microstructure , materials science , cubic zirconia , monoclinic crystal system , phase (matter) , tetragonal crystal system , context (archaeology) , transmission electron microscopy , isothermal process , yttria stabilized zirconia , coating , crystallography , chemical engineering , analytical chemistry (journal) , composite material , nanotechnology , crystal structure , chemistry , ceramic , thermodynamics , geology , chromatography , paleontology , physics , organic chemistry , engineering
The correlation between microstructural and phase evolution in aged, yttria‐partially‐stabilized zirconia, air plasma‐sprayed coatings is discussed. Freestanding coatings with the dense, vertically cracked structure were isothermally aged at 1482°C (2700°F) in air. Characterization of the resulting microstructures was conducted using transmission electron microscopy, then compared with a parallel analysis of the phase evolution via synchrotron X ‐ray diffraction ( XRD ) described in Part I. Additional context was provided by related studies on vapor‐deposited coatings. Several salient points can be extracted from these assessments. XRD was further validated as a practical method for studying phase stability after clarification of how the possible phases are defined, including the following: (i) the nature of the t′ phase observed in XRD after phase decomposition has begun and (ii) the relationship between the Y‐rich tetragonal ( t″ ) and Y‐rich cubic ( c ) phases reported to coexist via XRD . A strong relationship between the initial microstructure and the subsequent phase destabilization is also reported. As a result, phase evolution is proposed to proceed via two competing routes. The interplay between these mechanisms dictates the incubation time for monoclinic formation within a given coating.