Metastable phase selection and partitioning for Zr[sub (1[minus]x)]Al[sub x]O[sub (2[minus]x/2)] materials synthesized with liquid precursors
- Univ. of California, Santa Barbara, CA (United States). Materials Dept.
Aqueous solutions of zirconium acetate and aluminum nitrate were spray pyrolyzed at 250 C and upquenched to different temperatures to yield metastable solid solutions of composition Zr[sub (1[minus]x)]Al[sub x]O[sub (2[minus]x/2)]. An amorphous oxide forms first during pyrolysis which subsequently crystallizes as a single phase for x [le] 0.57 ([le] 40 mol% Al[sub 2]O[sub 3]). The crystallization temperature increased with Al[sub 2]O[sub 3] content. Electron diffraction, supported by Raman spectroscopy, indicates that the initial phase is tetragonal. At higher temperatures, the initial solid solution partitions to other metastable phases, viz., t-ZrO[sub 2] + [gamma]-Al[sub 2]O[sub 3], prior to achieving their equilibrium phase assemblage, m-ZrO[sub 2] + [alpha]-Al[sub 2]O[sub 3]. Partitioning yields a nanocomposite microstructure with grain sizes of 20--100 nm, compared to the 3 to 5 nm in the initial, single phase. Compositions containing 45 to 50 mol% Al[sub 2]O[sub 3] concurrently crystallize and partition. The structure selected during crystallization and the partitioning phenomena are discussed in terms of diffusional constraints during crystallization, which are conceptually similar to those operating during rapid solidification.
- OSTI ID:
- 6988714
- Journal Information:
- Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 77:8; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CRYSTALLIZATION
DATA
DISPERSIONS
EXPERIMENTAL DATA
INFORMATION
MICROSTRUCTURE
MIXTURES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
SOLID SOLUTIONS
SOLUTIONS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES