Structural Study of Potassium Gallate Glasses by Mössbauer Spectroscopy and Differential Thermal Analysis

Abstract

Abstract Mössbauer spectra of a series of potassium gallate (Ga2O3-based) glasses, containing 10 mol% Fe2O3 as a Mössbauer probe, consist of two types of quadrupole doublet peaks due to tetrahedral Fe3+ ions bonded with nonbridging and bridging oxygen atoms and those bonded only with bridging oxygen atoms. This indicates that all the Fe3+ ions are present at the substitutional sites of the tetrahedral Ga3+ ions constituting the skeleton of network structure. An increase in the K2O content results in an increased fraction of the FeO4 (and GaO4) tetrahedra bonded with nonbridging oxygen atom(s). A Mössbauer spectrum of 70K2O·20Ga2O3·10Fe2O3 glass consists of only one quadrupole doublet peak due to the FeO4 tetrahedra having nonbridging oxygen atom(s). This suggests that each of the Fe3+ (and also Ga3+) ions is tetrahedrally bonded with at least one nonbridging oxygen atom. Structural information obtained from the Mössbauer measurements is confirmed by DTA measurements of the gallate glasses, Tg of which shows a drastic decrease from 647 to 555 °C when the K2O content is changed from 35 to 70 mol%.