Electrical Conductivity of Single Crystalline Nickel Oxide

Abstract

The electrical conductivity of single crystalline NiO was found to be proportional to the 1/4 power of the oxygen pressure for oxygen partial pressures between loo and 10-4 atm over the temperature range of 900 to 1200 "C. These results are in agreement with singly ionized cation vacancies as the predominant nonstoichiometric defect. The sum of the enthalpies of formation of nonstoichiometric disorder and activated enthalpy of movement of an electron hole was found to remain constant when thermodynamic equilibrium was maintained. The activated enthalpy of movement of an electron hole, however, was found to obey the "Meyer-Neldel" relationship, that is, it increased as the concentration of electron holes decreased. An argument has been offered for the explanation of the "Meyer-Neldel" rule. This explanation involves consideration of another equilibrium between free electron holes and those trapped a t imperfections (such as dislocations) which are not usually considered in the usual theory of point defects in nonstoichiometric compounds.Es wurde gefunden, daB die elektrische Leitfahigkeit von einkristallinem NiO im Temperaturbereich von 900 bis 1200 "C fur Sauerstoffpartialdricke zwischen loo und a t exponentiell vom Sauerstoffdruck mit einem Exponenten 1/4 abhlngt. Diese Ergebnisse befinden sich in Ubereinstimmung mit einfach ionisierten Kationenlucken als dominierende nichtstochiometrische Defekte. Es wurde gefunden, daB die Summe der Bildungsenthalpien der nichtstochiometrischen Fehlordnung und der aktivierten Wanderungsenthalpie eines Elektronenlochs konstant bleibt, wenn das thermodynamische Gleichgewicht aufrechterhalten wird. Es wurde jedoch gefunden, daB die aktivierte Wanderungsenthalpie eines Elektronenlochs die ,,Meyer-Ne1delsche"Beziehung befolgt, d.h. sie wachst mit kleiner werdender Konzentration der Elektronenlocher. Eine Erklarung der ,,Meyer-Neldelschen" Regel wird vorgeschlagen, die ein verschiedenes Gleichgewicht zwischen freien Elektronenlochern und denen an Defekten (wie Versetzungen) getrappten berucksichtigt, was gewohnlich in der ublichen Theorie der Punktdefekte in nichtstochiometrischen Verbindungen nicht berucksichtigt wird.

Bifunctional Electrocatalytic Activity of Nitrogen-Doped NiO Nanosheets for Rechargeable Zinc–Air Batteries

“…Transition-metal oxides (particularly cobalt, nickel, and manganese oxides) are one of the most promising alternative catalysts because of their abundant reserves and strong corrosion resistances. − Among them, porous nickel oxides (NiO x ) nanosheets are considered the most suitable alternatives owning to high superior catalytic activities, safety, low cost, and easy preparation . However, the inherent low electronic conductivities, poor ion transport kinetics, and cycling durability of nickel oxides restrict their extensive use. , Recently, material design strategies demonstrated that the electrocatalytic activities of NiO x -based electrocatalysts can be efficiently increased by increasing the conductivity or inducing more active sites, e.g., by designing nanostructured NiO (nanoflakes or nanosheets), introducing foreign dopants (Fe-doped NiO) or constructing heterostructures to accelerate the electron transfer (Co 3 O 4 @NiO, Ni@NiO). − Among them, N doping has been widely used to improve the catalytic activities of the electrocatalysts since the electron-donor activities (N-doped Ni 2 P 4 O 12 ) or more available active surface area (N-doped Co 3 O 4 nanosheets, N-doped MoS 2 , or MoSe 2 nanosheets). ,− In addition, porosity engineering is also an effective strategy to develop high-efficiency electrocatalysts, which can expose and utilize more active sites and provide continuous charge transport pathways. , …”

Point defect diagrams for pure and doped nickel oxide $$ {\hbox{N}}{{\hbox{i}}_{{1} - \delta }}{\hbox{O}} $$ in the temperature range of 1,173–1,673 K (II)

“…Many authors obtained the value of the exponent 1=n s close to~1/6 [12,16,17,38]. In most works, higher values were obtained (1/5), also close to 1/4 [10,11,22,23,25]. Using the above fact as a basis, it is assumed that in Ni 1Àd O, single ionized vacancies are also present.…”

High‐Temperature Oxidation

“…Similar approaches can be applied to nonstoichiometric compounds with cation vacancies (Cu 2-d O-type oxide), oxygen interstitials (UO 2 þ d -type oxide), and so on [80,[82][83][84][85][86].…”