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Low‐Temperature Aging of t ′‐Zirconia: The Role of Microstructure on Phase Stability
Author(s) -
Jue Jan Fong,
Chen Jong,
Virkar Anil V.
Publication year - 1991
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.1151-2916.1991.tb07793.x
Subject(s) - materials science , crystallite , tetragonal crystal system , microstructure , yttria stabilized zirconia , cubic zirconia , monoclinic crystal system , grain size , ceramic , transmission electron microscopy , annealing (glass) , composite material , mineralogy , crystallography , crystal structure , metallurgy , nanotechnology , chemistry
Polycrystalline, tetragonal ( t ′) zirconia samples containing 3 and 4 mol% yttria were fabricated by annealing pressureless‐sintered samples in air at ∼ 2100°C for 15 min. The grain size of these fully tetragonal samples was on the order of 100 to 200 μm. Domain structure of the samples and of a 3‐mol%‐yttria‐doped tetragonal zirconia single crystal was examined by transmission optical microscopy under polarized light and by transmission electron microscopy. The orientations of the domain/colony boundaries were in accord with the predictions of group theory. As‐polished surfaces of polycrystalline t ′ materials showed no monoclinic phase even after 1000 h at 275°C in air. By contrast, conventionally yttria‐doped tetragonal zirconia polycrystalline (Y‐TZP) ceramics of grain size >0.5 μm showed substantial transformation. Surface grinding enhanced the resistance to degradation of Y‐TZP but decreased that of t ′ materials. Even then, the t ′ materials exhibited better resistance to degradation than the Y‐TZP ceramics. Excellent resistance of the t ′ materials to low‐temperature aging despite a very large grain size and the opposite effect of grinding on phase stability are all explained on the basis of ferroelastic domain structure of these materials.