Zirconium oxide crystal phase: The role of the pH and time to attain the final pH for precipitation of the hydrous oxide
Precipitated hydrous zirconium oxide can be calcined to produce either a monoclinic or tetragonal product. It has been observed that the time taken to attain the final pH of the solution in contact with the precipitate plays a dominant role in determining the crystal structure of the zirconium oxide after calcination at 500 /sup 0/C. The dependence of crystal structure on the rate of precipitation is observed only in the pH range 7--11. Rapid precipitation in this pH range yields predominately monoclinic zirconia, whereas slow (8 h) precipitation produces the tetragonal phase. At pH of approximately 13.0, only the tetragonal phase is formed from both slowly and rapidly precipitated hydrous oxide. The present results, together with earlier results, show that both the pH of the supernatant liquid and the time taken to attain this pH play dominant roles in determining the crystal structure of zirconia that is formed after calcination of the hydrous oxide. The factors that determine the crystal phase are therefore imparted in a mechanism of precipitation that depends upon the pH, and it is inferred that it is the hydroxyl concentration that is the dominant factor.
- Research Organization:
- Kentucky Energy Cabinet Laboratory, University of Louisville, P.O. Box 13015, Lexington, Kentucky 40512 and the Department of Metallurgical Engineering and Materials Science, University of Kentucky, Lexington, Kentucky 40506
- OSTI ID:
- 7201781
- Journal Information:
- J. Mat. Res.; (United States), Journal Name: J. Mat. Res.; (United States) Vol. 3:4; ISSN JMREE
- Country of Publication:
- United States
- Language:
- English
Similar Records
Crystal structure of hafnia--zirconia mixtures obtained by calcination of hydrous oxide prepared by precipitation
Factors determining the crystal phases of zirconia powders: A new outlook
Related Subjects
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
CALCINATION
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL STRUCTURE
DECOMPOSITION
DIFFRACTION
HYDRATES
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PRECIPITATION
PYROLYSIS
SCATTERING
SEPARATION PROCESSES
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES