Effect of Fe incorporation on cation distributions and hopping conductions in Ni-Mn-Co-O spinel oxides

Abstract

Effect of Fe incorporation on electrical properties of (NixCoyMn3-x-y)O-4 (NMC) spinel compound is investigated for the application to a negative temperature coefficient (NTC) thermistor. Cation distribution of the Fe doped NMC (FNMC) is calculated based on the size of ions located at tetragonal A sites and octahedral B sites in spinel structure, which can be closely related with temperature dependent electrical properties of the FNMC. With change of Fe contents, the ratio of Mn3+/Mn4+ in octahedral B site of FNMC is changed which can determine the temperature sensitivity factor (B-value). Hopping conduction mode relating with activation energy and hopping distance was also discussed depending on Fe contents, based on the small polaron hopping theory. (C) 2017 Elsevier B.V. All rights reserved.