Role of Na-doping-induced oxygen vacancies in the variation of electrical properties of NiO ceramics

Na-doping concentration dependent electrical and structural properties of NiO ceramics were investigated. Various samples of NaxNi1−xO (x = 0.00, 0.01, 0.03, 0.05, 0.07, 0.09, 0.11) were prepared by using conventional solid state reaction. Most of the samples showed the decreased electrical resistivity with the increase of the Na-doping concentration while maintaining phase-pure face-centered cubic (fcc) structure, except in the case of the sample containing 11% of Na. For the sample containing 11% of Na, the electrical resistivity slightly increased due to the presence of secondary phase. The possible physical origin of this reduced electrical resistivity is related to the increased number of oxygen vacancies, with the increase of the Na-doping concentration for phase-pure NaxNi1−xO ceramics.