ABSTRACT

Two series of solid solutions of olivine structure, (Mg, Co)₂SiO₄ and (Mg, Ni)₂SiO₄, were synthesized at 1, 400°C, and their unit cell parameters were measured at room temperature. It was found that deviations from Vegard's law increase according to the order (Mg, Fe)₂SiO₄, (Mg, Co)₂SiO₄ and (Mg, Ni)₂SiO₄. This order coincides with the order of octahedral crystal field stabilization energies of transition metal ions. It was suggested that the site preference of Mg and transition metal ions over M_I and M_II sites is most pronounced in the case of (Mg, Ni)₂SiO₄ solid solution series.