Synthesis and characterization of nonstoichiometric nickel manganite spinels NixMn3 − x□3δ4O4 + δ

Nickel manganites have been prepared by thermal decomposition of mixed oxalates Nix3Mn(3 − x3C2O4 · nH2O in air at 623 K (0 ≤ x ≤1). These oxides are finely divided materials because their BET specific surface areas are close to 100 m2/g and the average diameter of their crystallites is about 10 nm. Electron diffraction studies of these compounds show that they crystallize in a spinel-like cubic structure. Thermogravimetric analyses show that these oxides are nonstoichiometric cation deficient spinels NixMn3 − x□3δ4O4 + δ. δ depends on nickel content and reaches a maximum of 0.9 for x = 0.4.