Infrared absorption spectra of the spinels Fe 2SiO 4 and Co 2SiO 4

Abstract

The i.r. absorption spectra of the spinel polymorphs of Fe 2SiO 4 and CO 2SiO 4 have been measured from 200 to 4000 cm −1. Three strong absorption bands are observed at 835, 503 and 340 cm −1 and 810, 503 and 357 cm −1, respectively, and correspond to 3 of the 4 i.r. active T 1 u modes. The observed frequencies lie close to those for Ni 2SiO 4 [5] and are consistent with the normal spinel structure. The cation size effect on the i.r. frequencies and the nature of the vibrational modes are discussed for II–IV spinels.