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Diffusionless Cubic‐to‐Tetragonal Phase Transition and Microstructural Evolution in Sintered Zirconia–Yttria Ceramics
Author(s) -
Zhou Yu,
Lei TingChuan,
Sakuma Taketo
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.tb04071.x
Subject(s) - tetragonal crystal system , materials science , diffusionless transformation , crystallography , ceramic , diffraction , phase transition , phase (matter) , lattice (music) , substructure , condensed matter physics , crystal structure , martensite , microstructure , optics , metallurgy , chemistry , physics , organic chemistry , structural engineering , engineering , acoustics
Microstructural changes associated with the diffusionless cubic‐to‐tetragonal phase transition ( c–t ′) in sintered ZrO 2 –Y 2 O 3 ceramics with 4 to 20 mol% Y 2 O 3 are investigated. Ceramics containing 4 to 7 mol% Y 2 O 3 that are quickly cooled from high temperatures experience cubic‐to‐tetragonal transformation by a diffusionless mechanism. The TEM diffraction pattern of the transformation product, t ′‐ZrO 2 , reveals (112) reflections that are suppressed in the c ‐ZrO 2 phase. The microstructural features of the t ′‐ZrO 2 phase include antiphase boundaries and a twinned substructure in the (112) dark‐field images. The (112) reflections result from the displacement of oxygen atoms in the lattice during phase transformation. With increasing Y 2 O 3 content, the antiphase domain size, the tetragonality of the lattice, and the intensity of the (112) reflections decrease. When the Y 2 O 3 content reaches 8 mol% or more, the (112) reflections appear, but the dark‐field image shows no antiphase boundary, and the tetragonality decreases to 1. In ceramics with 14 to 20 mol% Y 2 O 3 , no suppressed reflection appears because the c–t transformation is fully suppressed. A model of the lattice structure is calculated and the intensity of diffraction determined experimentally; on this basis, the mechanism of diffusionless c–t ’transformation is discussed.