EXAFS and XRD Study of the Structural Evolution during Isothermal Sintering of SnO2 Xerogels
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Data
1997-12-01
Autores
Brito, G. E S [UNESP]
Briois, V.
Pulcinelli, Sandra Helena [UNESP]
Santilli, Celso Valentim [UNESP]
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Resumo
The formation of an ordered (crystalline) phase during isothermal sintering of SnO2 monolithic xerogels, at 200, 250, 300, 400, 500, 600 and 700°C, has been analyzed by the combined use of EXAFS and XRD techniques. For the desiccated gel (110°C), EXAFS results show the formation of small microcrystallites with the incipient cassiterite structure. Between 110 and 250°C, the dehydratation reaction leads to an amorphization evidenced by a decrease of the long and short range crystallographic order. It is due to fissure formation in the xerogel network. For higher temperatures, a continuous coagulation of the crystallites occurs, leading to grain growth. Grain and pore growth obeys the same kinetic relation, so that the microstructure grows by simple enlargement while its morphology is static.
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EXAFS, Sintering, SnO2 xerogels, XRD, Amorphization, Coagulation, Crystal microstructure, Crystalline materials, Dehydration, Grain growth, Morphology, Reaction kinetics, Thermal effects, Tin compounds, X ray diffraction analysis, Extended X ray absorption fine structures (EXAFS), Isothermal sintering, Structural evolution, Xerogels, Gels
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Journal of Sol-Gel Science and Technology, v. 8, n. 1-3, p. 269-274, 1997.