Effect of annealing at oxygen partial pressure on the conductivity of Ni_(0.5)Mn_(2.5)O_4 oxides

摘要

This paper presents a study of the electrical properties of nickel manganite Ni_(0.5)Mn_(2.5)O_(4-x) as a function of annealing at oxygen partial pressure. The crystalline phase of manganite ceramics during annealing at oxygen partial pressure was investigated using X-ray diffraction; the predominant phase was tetragonal spinel. The electrical properties were analyzed by measuring resistance-temperature characteristics. The activation energy for electron hopping, determined using the slope of the In ρ-1/T plots, was higher for samples annealed at lower oxygen partial pressure. The Mn~(4+)/Mn~(3+) ratio, obtained through differential thermal analysis, increased with an increase in the oxygen partial pressure during annealing. The relationship between resistivity and the Mn~(4+)/Mn~(3+) ratio during annealing at oxygen partial pressure was investigated.