Synthesis and optical absorption spectra of Cr2+-containing orthosilicates

By reacting chromium metal with appropriate oxides in a neutral atmosphere at high temperature it is possible to prepare Mg₂SiO₄ with the olivine structure containing Cr⁺⁺ and also Cr₂SiO₄. X-ray powder diffraction data for chromous orthosilicate may be indexed on an orthorhombic cell with a=5.690, b=11.262, and c=9.584 Å. The compound is not isotructural with olivine. Optical absorption spectra of Cr²⁺ in both hosts have been obtained and also indicate large differences between the two structures.