SYNTHESIS AND CHARACTERIZATION OF TERNARY ZINC-ANTIMONY-TRANSITION METAL SPINELS

Four series of ternary Zn(x)Me(y)Sb(z)O(4) spinels, Me = Cr, Mn, Co, or Ni, y less than or equal to 0.778, have been prepared by solid state reaction from appropriate oxides. The spinels were characterized by the X-ray powder diffraction method. The efficiency of Me ions to form spinel structure measured by the temperature needed to obtain the pure spinel phase decreases in the order Cr approximate to Mn > Co > Ni. The reaction temperature also becomes lower with increasing content of Me ions. The spinel lattice constants decrease linearly with increasing Me content, while the slope of curves depends on the ionic radii of Me ions. These results allow the lattice constant of more complex spinels to be estimated. Crystal structures of (Zn-1.000)[Zn0.633Co0.700Sb0.667]O-4, a = 0.85822(1) nm, and (Zn-1.000)[Zn0.816Cr0.778Sb0.407]O-4, a = 0.84924(1) nm, spinels, where ( ) denotes tetrahedral and [ ] octahedral sites, are determined by Rietveld's method from X-ray powder diffraction data. The results show that Co(II), Cr(III), and Sb(V) are situated in the octahedral site. The tetrahedral site is occupied exclusively by Zn ions. The same cation distribution was postulated for all spinels. (C) 1994 Academic Press, Inc.