Sol-Gel Synthesis and Spectroscopic Analysis of Chromium in Sol Gel Silica

Abstract

Dense chromia-silica glasses have been successfully synthesized by the sol-gel method. Optical absorption and electron spin resonance studies are used to get the insight information about the prepared matrices. As the heat treatment temperature increased, Cr³⁺ ® Cr⁶⁺ conversion was facilitated, thereby generating Cr⁵⁺ ions in the matrix. The amount of Cr⁵⁺ and Cr⁶⁺ centers can vary depending on the preparation conditions. Racaah parameter (B) of chromium in the octahydral symmetry has been evaluated by using the spectral data. The reduction of Racaah parameter from its free ion value (918 cm^-1) reflects the presence of covalent bonding in the matrix. An attempt has been made to explain the nature of chromium on the basis of rule of ratio of radius.