Stability limits in the monoclinic-tetragonal transformations of zirconia
A variety of experimental data obtained from single crystals and powders of zirconia has been examined to obtain the stability limits of the tetragonal and monoclinic phases. These limits are used to delineate the possible modes of transformation at different temperatures in the light of a nonclassical theory of nucleation. The theory predicts an asymmetric relation between three critical temperatures T*, T/sub o/, and T/sub c/. Transformation by nucleation and growth occurs only in the range T/sub o/-T/sub c/ during cooling and in the range T*-T/sub o/ during heating. Below T/sub c/, transformation proceeds homogeneously in a manner akin to spinodal decomposition. In the neighborhood of T/sub c/, the metastable tetragonal phase can have a long lifetime. It is assumed that the driving mechanism of transformation comes from the partial softening of a particular shear mode of lattice vibration. An indirect evidence in support of this assumption comes from the linear relationship between the transformation temperature of a zirconia/hafnia solid solution and the reciprocal effective cation mass. 31 refs., 6 figs.
- Research Organization:
- Commonwealth Scientific and Industrial Research Organization, Clayton (Australia). Div. of Materials Science and Technology; Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 5311658
- Report Number(s):
- CONF-870843-10; ON: DE88005924
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
CHALCOGENIDES
CRITICAL TEMPERATURE
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
ENERGY LEVELS
EXCITED STATES
HAFNIUM COMPOUNDS
HAFNIUM OXIDES
KINETICS
LATTICE VIBRATIONS
METASTABLE STATES
MONOCLINIC LATTICES
NUCLEATION
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
REFRACTORY METAL COMPOUNDS
TETRAGONAL LATTICES
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES