Study on the sol-gel-synthesis of glasses with novel structure

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The sol-gel method using metal alkoxides as raw materials was appliedto the preparation of glasses with unique compositions and structure which can not be achieved by the conventional melting technique. Following results were obtained.(1) Germanate glasses : The Na_20-Ge0_2 and Pb0-Ge0_2 glasses were obtainable by the sol-gel method. The structure, especially coordination state of Ge in those glasses was examined by several tchniques such as X-ray radial distribution function analyzes, EXAFS,IR and Raman spectroscopy. It was found that the amount of 6-fold coordinated Ge ions in the sol-gel-derived glasses was almost twice as large as the corresponding melt-derived glasses.(2) Titanate glasses : The Na_20-Ti0_2, Ba0-Ti0_2, PbO-TiO_2, Nb_20_5-Ti0_2, and Bi_20_3-Ti0_2 glasses with very high content of Ti0_2 were also prepared by the sol-gel method. The coordination state of Ti in the former two glasses was 5- and 6-fold, respectively, and the Ti0_n polyhedra were highly distorted, making … More these glasses usable in the nonlinear optics. The latter three glasses, really, exhibited third-order optical nonlinear susceptibility as high as 10^<-12> esu.(3) Li and K-glicolato complex of 5-fold coordinated Si was thermally decomposed to obtain Li_20- or K_20-Si0_2 glasses with unique structure. While Li-Si complex gave glasses with the structure similar to corresponding melt-derived glasses, it was considered that K-Si complex produced glasses containing a small amount of 5-fold coordinated Si.(4) Alumina gels which transformed partly to alpha-alumina around 500ﾟC was prepared from aluminum alkoxide under carefully controlled hydrolysis condition. Also, carefully designed hydrolysis reaction of Zr-and Si-alkoxides was found to lead to the Zr0_2-Si0_2 gel which produced ZrSi0_4 around 800ﾟC,when a lithium compound was added as a mineralizer.All above results have confirmed that the sol-gel method can really make glasses and gels with unique or novel structure and compositions at relatively low elevated temperatures. Less