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Phase Separation by Spinodal Decomposition in the Tetragonal System
Author(s) -
STUBICAN V. S.,
SCHULTZ A. H.
Publication year - 1970
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.1151-2916.1970.tb12072.x
Subject(s) - spinodal decomposition , spinodal , tetragonal crystal system , materials science , phase (matter) , wavelength , condensed matter physics , thermodynamics , chemistry , physics , optoelectronics , organic chemistry
Coherent spinodal curves for the [001] and [100] directions were calculated for the system TiO 2 ‐SnO 2 . Inside the [001] spinodal curve, the crystalline solutions decomposed by a modulated phase composed of TiO 2 ‐rich and SnO 2 ‐rich plates perpendicular to the [001] direction. No modulation of structure was observed at compositions and temperatures between the [001] coherent spinodal and the equilibrium curve. The kinetics of the decomposition showed that the wavelength of the modulation decreased in the early stages of the separation, reaching minimum observable values of approximately 110 Å at 925°C, 170 Å at 1000°C, and 240 Å at 1150°C. In the second stage when the coherency was lost, the wavelength increased. Theoretical calculations to find the elastic free energy/unit volume to cause fluctuation of composition in the spinodal process were worked out for the tetragonal system. The calculations were done for an arbitrary direction and involved elastic constants. The theoretical prediction and the experimental results for the system TiO 2 ‐SnO 2 agreed well.