Structural and Electrical Properties of Oxidic Spinels Containing Zinc, Cobalt, Chromium and Manganese

Department of Inorganic Chemistry, Institute of Science, Bombay-400 032

Manuscript received 24 June 1980, accepted 28 January 1981

X-ray crystallographic study of the system ZnCo₁ –  _xCr_x  MnO₄ has been carried out with a view to investigating the co-operative influence of other ions like Co³⁺ and Cr³⁺ in the presence of  Mn³⁺ (J-T) ion in aiding or hindering the distortion of the spinel lattice. The lattice parameter of  the compounds showed that the cubic spinel phase changed to tetragonal when 30% of  B-sites were occupied by Cr³⁺  ions. The plot of  V^{\(^{1/3}\)} vs composition showed a break at the transition region. The electrical resistivity-temperature behaviour obeyed the relation  \(\rho\)\(=\)\(\rho\)\(o\) exp (ΔE/kT). The hot probe tests showed that all compounds were p-type semiconductors. The plots of  ΔE and mean  d_B-_B distance vs composition showed a break where there was a change in the crystal structure indicating close relationship between crystal symmetry and the mode of conduction.