Effect of annealing at oxygen partial pressure on the conductivity of Ni0.5Mn2.5O4 oxides
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This paper presents a study of the electrical properties of nickel manganite Ni0.5Mn2.5O4−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 ln ρ–1/T plots, was higher for samples annealed at lower oxygen partial pressure. The Mn4+/Mn3+ ratio, obtained through differential thermal analysis, increased with an increase in the oxygen partial pressure during annealing. The relationship between resistivity and the Mn4+/Mn3+ ratio during annealing at oxygen partial pressure was investigated.
KeywordsOxygen Partial Pressure Manganite Octahedral Site Spinel Structure Lower Oxygen Partial Pressure
Financial support for this research, provided by the National Science Council, Taiwan, ROC, under Grant No. NSC 98-2221-E-036-012, is gratefully acknowledged.