Anion-Substituted Garnets Ca3Mn2 – x(Ni, Co)xVyGe3 – yO12 (x = 0, 1; y = 0, 1, 2): Preparation and Characterization

摘要： Garnets with the structure similar to that of Ca3Mn2Ge3O12 have been prepared with simultaneous substitutions of Ge4+ by V5+ in tetrahedra and of Mn3+ by Ni2+ or Co2+ in octahedra. X-ray photoelectron spectroscopy (XPS) proved the absence of V4+ in tetrahedra of the lattice of the compounds prepared and determined the valences of elements in octahedral sites. The increasing d-cation size in octahedra is accompanied by an increase in unit cell volume regardless of the composition of tetrahedra (VyGe3 – y)O12. The electrical conductivity of Ca3Mn2 – x(Ni, Co)xVyGe3 – yO12 (x = 0, 1; y = 0, 1, 2) garnet ceramic samples and the calculated bandgap widths make it possible to classify them with medium-gap semiconductors.