The preparation and electrical properties of sintered bodies consisting of monophase cubic spinel oxides, Mn(1 + 0.5X)FeNi(1- 0.5X)O4 (0 ≤ X ≤ 1.00), were investigated. Sintered bodies composed of monophase cubic spinel structure were prepared through heat treatment at 1000 oC for oxidization after sintering at 1400 oC in Ar. The required time for oxidization exceeded 48 h for specimens with X = 0 to 0.375 and more than 96 h for those with X = 0.50 to 1.00. Electrical conduction (σ) and Seebeck potential (Qe) were measured using rectangular bars cut from sintered pellets. The electrical characteristics were determined based on the change of cation distribution related to the disproportionation of Mn ions. We concluded that the electrical conduction of sintered bodies is controlled by a small polaron hopping mechanism.

Keywords: Mn-Fe-Ni monophase cubic spinel oxide, Electrical conductivity, Seebeck coefficient, Small polaron hopping, NTC thermistor.