INVESTIGATIONS ON ELECTRONICALLY CONDUCTING OXIDE SYSTEMS .21. STABLE SPINELS ZNZNIMN2-ZO4 AND COMPARISON WITH SPINELS MGZNIMN2-ZO4

Stable spinels are obtained in the result of substitution of Zn(II) for manganese in the series ZnzIINiIIMnzIVMn2-2zIIIO4 (0 less-than-or-equal-to z < 1). Different from spinels MgzIINiIIMnzIVMn2-2zIIIO4 (0 less-than-or-equal-to z less-than-or-equal-to 1) they don't be submitted to decomposition in air during slow cooling at medium temperatures. ZnNiMnO4 (z = 1) could not be prepared in a mono-phase state which is indicated by the composition of ZnNiMnO3.96 deduced from analysis by oxidimetric titration. The comparably small variation of the specific electrical conductivity and of the activation energy observed in the range 0 less-than-or-equal-to z less-than-or-equal-to 2/3 for ZnzNiMn2-zO4 is discussed in relation to larger alterations in the series MgzNiMn2-zO4. Structural interpretation is proposed based on the comparison of the molar volume of spinels M Mn2O4 (M:Mn, Fe, Co, Ni, Cu, Zn, Mg).