Rietveld refinement of amorphous SiO2 prepared via sol–gel method

• Published in: Materials letters Vol. 60; no. 29-30; pp. 3526 - 3529
• Main Authors: Martínez, J.R., Palomares-Sánchez, S., Ortega-Zarzosa, G., Ruiz, Facundo, Chumakov, Yurii
• Format: Journal Article
• Language: English
• Published: 01.12.2006
• ISSN: 0167-577X
• DOI: 10.1016/j.matlet.2006.03.044

Using the Rietveld refinement, the structural evolution was analysed under thermal treatment of silica xerogel samples prepared by the sol-gel method with molar ratio (R) of water to TEOS of R = 5 and R = 11.66. The structure of compounds was refined using the Maud program and the unit cell parameters and atomic positions of the refined silica amorphous atoms were found for whole samples. The results showed that the amorphous structure is quartz-like or low-cristobalite-like, depending on the molar ratio values and the heat-treatment of the samples. For R = 5, different quartz structures were obtained whereas, for R = 11.66, close structures were obtained in which a transformation of quartz-like amorphous to low-cristobalite amorphous phase occurred at about 600 C. These results give scope to explain the partial crystallisation of the silica at relatively low temperatures obtained when metallic species are present. 25 refs.