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Crystallization of ThSiO4 from structurally and/or compositionally diphasic gels

Published online by Cambridge University Press:  31 January 2011

Gabriel Vilmin ,
Sridhar Komarneni  and
Rustum Roy
Gabriel Vilmin
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park. Pennsylvania 16802
Sridhar Komarneni
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park. Pennsylvania 16802
Rustum Roy
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park. Pennsylvania 16802
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Abstract

The use of structurally and/or compositionally diphasic gels has been shown earlier to have profound effects in lowering the crystallization temperature and enhancing densification in several systems. In this study of solid-state epitaxy the ThSiO4 composition has been investigated. The use of compositional diphasicity allows one to lower the huttonite (β-ThSiO4) crystallization temperature by as much as 200°C. Using crystalline thorite (α-ThSiO4) as second phase nuclei partially stabilizes this phase (hypothetically metastable), while the introduction of huttonite nuclei completely inhibits the formation of the α form, which appears in detectable quantities in the unseeded precursors. This confirms the structural (epitaxial) control of the solid-state reaction. The use of structural or compositional nanoheterogeneity clearly helps to lower the crystallization temperature and to stabilize a particular polymorph in ccramics processed by the sol-gel route, and this principle can certainly be utilized more generally.

Type
Articles
Information
Journal of Materials Research , Volume 2 , Issue 4 , August 1987 , pp. 489 - 493
Copyright
Copyright © Materials Research Society 1987

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References

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