Formation of silicate structures in Cu-containing silica xerogels

Using infrared absorption and Raman spectroscopy, the structure of SiO2 sol -gel samples containing copper were analyzed as a function of air heat trea tments. The weight composition of the samples was 70(SiO2)-30(CuO) and the thermal treatments were carried out in air at Various temperatures in the r ange of 100-600 degreesC. It was found that the Cu might be incorporated in to the SiO2, matrix at least in two ways: forming oxide particles and formi ng metasilicatelike structures. The copper metasilicate found had the chemi cal formula, Cu-6[Si6O18].6H(2)O, which is known as dioptase with a thermal stability at temperatures up to 600 degreesC.