Physical Chemistry of the Thermal Transformation of Mesoporous and Microporous Zirconia

In fine-grained zirconia, the order of stability of the three polymorphs is exactly the reverse of that observed in a coarse-grained sample. Starting from a disorder amorphous material, the crystallization into the cubic form occurs, in general, below 500 °C. It is followed, or accompanied, by the f...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2000-12, Vol.104 (50), p.11906-11911
Main Authors: Pacheco, G, Fripiat, J. J
Format: Article
Language:English
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Summary:In fine-grained zirconia, the order of stability of the three polymorphs is exactly the reverse of that observed in a coarse-grained sample. Starting from a disorder amorphous material, the crystallization into the cubic form occurs, in general, below 500 °C. It is followed, or accompanied, by the formation of tetragonal ZrO2 and, finally, by the crystallization into monoclinic zirconia above 700 °C. This sequence is observed in mesoporous and microporous zirconia. It has been suggested that this anomalous behavior is due to a high surface energy of the monoclinic phase or to strains present in the small particles. It is shown here that the surface effect explains satisfactorily and semiquantitatively the observations. This does not rule out other factors.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp001455d