INVESTIGATIONS ON ELECTRONICALLY CONDUCTING OXIDE SYSTEMS .23. STRUCTURE AND PROPERTIES OF STABLE SPINELLS IN THE SERIES MZNIMN2-ZO4 (M = LI, FE)

Preparation and properties of the spinel compounds LizNiMn2-zO4 (0 less-than-or-equal-to z less-than-or-equal-to 2/3) and FezNiMn2-zO4 (0 less-than-or-equal-to z less-than-or-equal-to 1) are reported. Compounds of the series ZnzNiMn2-zOr are involved. Different from the initial compound NiMn2O4 (z = 0), the spinels with z greater-than-or-equal-to 1/6 submitted to annealing at 400-500-degrees-C appear to be in the thermodynamically stable state. For M = Li and Zn the upper limit of thermal stability of the compounds becomes comes reduced which, however, is not valid for the series with M = Fe. The alterations are interpreted in view of structural chemistry. The electrical properties are discussed in the frame of the polaron hopping model in close relation with the cationic distribution.