The electrical conductivity of CoO: Experimental results and a new conductivity model

Abstract

The electrical conductivity of the transition metal oxide Co1‐σO has been measured as a function of the oxygen activity and the temperature in the whole stability field of CoO using a very pure single crystal. The results are modelled in terms of a new conductivity model in which free electron holes as well as electron holes which are trapped by cation vacancies contribute to the conductivity. At low oxygen activities also electrons are considered. Within this model the following parameters are obtained: the two mass action constants, K1 and K11, for the incorporation of oxygen and the formation of singly ionized vacancies, the mobilities of free and trapped electron holes, b0 and b1, and the product of the electron mobility and the electronic mass action constant, Kebe. A microscopic interpretation of the model is made possible by translating the so‐called five‐frequency model for impurity diffusion to the conductivity problem. Then it is also possible to estimate the lifetime of the associate consisting of a doubly ionized vacancy and an electron hole, which is about twenty times larger than the residence time of an electron hole on a cation site.

Self-Organized TiO2/CoO Nanotubes as Potential Anode Materials for Lithium Ion Batteries

“…For example, oxide nanotubes obtained from Ti-V, Ti-Ni, Ti-Fe, Ti-Mo-Ni and Ti-6Al-4V alloys were implemented in rechargeable batteries, super capacitors, solar hydrogen production systems and are investigated under biomedical aspects [25][26][27][28][29] . The Ti-Co-O system is a very promising candidate to significantly contribute to the physicochemical properties such as the relatively high electric and ionic conductivity of CoO to those of TiO 2 beneficial the 1D structures of the formed nanotubes [30][31][32][33][34] . Consequently, the diffusion rate of Li ions through the electrode is expected to be increased.…”

“…Such mixed oxide nanotubes were demonstrated to have real potential for applications. For example, oxide nanotubes obtained from Ti–V, Ti–Ni, Ti–Fe, Ti–Mo–Ni and Ti–6Al–4V alloys were implemented in rechargeable batteries, super capacitors and solar hydrogen production systems, and have been studied under biomedical aspects. − The Ti–Co–O system is a very promising candidate to contribute significantly to the physicochemical properties such as the relatively high electric and ionic conductivity of CoO to those of TiO 2 beneficial the 1D structures of the formed nanotubes. − Consequently, the diffusion rate of Li ions through the electrode is expected to be increased. 1D architectures are known to overcome the pulverization or the structure collapse resulting from the large volume changes during lithium ion insertion/extraction .…”

Behavior of MgFe2O4 Films on MgO in an Electric Field

“…1 This driving force could be an oxygen potential gradient, 1-7 a temperature gradient, 8,9 a nonhydrostatic stress, 10 or, as in the case of the present study, an applied electric field. [11][12][13][14][15][16][17] Kinetic demixing and decomposition become issues of practical importance when oxides are utilized for their high-temperature properties, e.g., their chemical inertness and electrical insulating properties. At high temperatures the structural elements of an oxide become mobile.…”

High-Temperature Current Collection Enabled by the in Situ Phase Transformation of Cobalt–Nickel Foam for Solid Oxide Fuel Cells

“…Therefore, at the initial stage of oxidation, the surface is populated with an excess amount of cobalt, leading to the formation of CoO and Co–Ni spinel oxide, and the subsequent incorporation of nickel gradually transforms CoO into the Co–Ni spinel. The XRD results in Figure a suggest that the single-phase Co–Ni spinel oxide foam can be obtained at the initial stage of operation within 100 h, which is beneficial for performance because the electrical conductivity of CoO is significantly lower than that of the Co–Ni spinel − and the presence of CoO in the current collector would increase the ohmic resistance of the stack. Figure b shows the elemental mapping results of Co and Ni at the cross section of the Co–Ni alloy foam, and both Co and Ni are homogeneously distributed.…”