Local structures around Fe and Cr atoms in glasses of the systems CaMgSi₂O₆–CaFeAlSiO₆ and CaMgSi₂O₆–CaCrAlSiO₆ determined by X-ray diffraction method

Abstract

Local structures around transition-metal atoms were investigated on glasses in the systems CaMgSi₂O₆–CaFeAlSiO₆ and CaMgSi₂O₆–CaCrAlSiO₆ with the X-ray diffraction technique. The correlation functions of the glasses in the former system indicated that a part of Fe atoms have coordinations lower than sixfold. Since the melting points of the substances rise rapidly with the increasing amount of CaCrAlSiO₆, the glasses with CaCrAlSiO₆ contents up to 5 wt% were examined in the latter system. Within this compositional range, the correlation functions showed that Cr atoms have sixfold coordinations. The difference in the preference to the sixfold coordination between Fe³⁺ and Cr³⁺ ions is supposed to be due to the difference in the crystal-field stabilization energy.