INFRARED SPECTRA OF M³⁺₂Si₂O₇ COMPOUNDS WITH THORTVEITITE STRUCTURE

Abstract

Infrared spectra of In₂Si₂O₇ and Lu₂Si₂O₇ with thortveitite structure were measured in the frequency range 1300-400cm^-1. The frequencies of the anti-symmetrical Si-O-Si stretching in In₂Si₂O₇ and Lu₂Si₂O₇ are 1175cm^-1, and 1115cm^-1, respectively. The frequency in M³⁺₂Si₂O₇ compound with thortveitite structure is strongly influenced by the electronegativity and the electronic structure of the M³⁺ ion. These facts suggest that the Si-O (br) distance in thortveitite structure is strongly influenced by them.