Anomalies in the electrical conductivity of nickel oxide above room temperature

Vernon, M. W.; Lovell, M. C.

doi:10.1016/0022-3697(66)90087-4

Cited by 31 publications

(6 citation statements)

References 11 publications

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“…This oxide is known to have E ∼ 0.7 eV for 120 ≤ T ( • C) ≤ 250 • C and E ∼ 0.3 eV for 250 ≤ T ( • C) ≤ 900. 12,13 Thus, the estimated E dependence on the NiO content provides further evidence that the transport mechanisms in the NiO concentration regions (1), (2), and (3) are due to ionic, mixed, and electronic charge carriers, respectively.…”

Section: Resultsmentioning

confidence: 85%

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Electrical properties of YSZ/NiO composites prepared by a liquid mixture technique

Esposito

Florio

Fonseca

et al. 2005

Journal of the European Ceramic Society

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Section: Resultsmentioning

confidence: 85%

“…For intermediary NiO compositions (region 2), a clear discontinuity of the Arrhenius behavior is observed at T ∼ 250 • C, a temperature found to be NiO-concentration independent and close to the Néel temperature of NiO. 13 In order to describe the ρ(T) curves of the NiO compositions m > 20 curves, two Arrhenius processes were used.…”

Section: Resultsmentioning

confidence: 99%

Electrical properties of YSZ/NiO composites prepared by a liquid mixture technique

Esposito

Florio

Fonseca

et al. 2005

Journal of the European Ceramic Society

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“…5,19 NiO exhibits a discontinuity in the Arrhenius plots at a temperature close to the Néel temperature ͑T N Ϸ 250°C͒, and the activation energies are ⌬E Ϸ 0.7 and 0.3 eV for T Ͻ T N and T Ͼ T N , respectively. 5,19 The ͑T͒ data at low temperatures ͑T Ͻ 400°C͒ shown in Fig. 3 indicated that the NiO content had a large influence on the electrical conductivity of the composite.…”

Section: Resultsmentioning

confidence: 99%

“…4 NiO is a p-type semiconductor, the charge carriers being the electron holes due to Ni vacancies. 5,19 NiO exhibits a discontinuity in the Arrhenius plots at a temperature close to the Néel temperature ͑T N Ϸ 250°C͒, and the activation energies are ⌬E Ϸ 0.7 and 0.3 eV for T Ͻ T N and T Ͼ T N , respectively. 5,19 The ͑T͒ data at low temperatures ͑T Ͻ 400°C͒ shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Mixed Ionic–Electronic YSZ/Ni Composite for SOFC Anodes with High Electrical Conductivity

Fonseca

Florio

Esposito

et al. 2006

J. Electrochem. Soc.

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The preparation of the ZrO 2 :8 mol % Y 2 O 3 /NiO ͑YSZ/NiO͒ composites by a modified liquid mixture technique is reported. Nanometric NiO particles dispersed over the yttria-stabilized zirconia ͑YSZ͒ were prepared, resulting in dense sintered specimens with no solid solution formation between the oxides. Such a feature allowed for the electrical characterization of the composites in a wide range of relative volume fraction, temperature, and oxygen partial pressure. The main results indicate that the composites have high electrical conductivity, and the transport properties in these mixed ionic-electronic ͑MIEC͒ composites are strongly dependent on the relative volume fraction of the phases, microstructure, and temperature. These parameters should hence be taken into consideration for the optimized design of MIEC composites for electrochemical applications. In this context, the composite was reduced under H 2 for the preparation of high-conductivity YSZ/Ni cermets for use as solid oxide fuel cell anode material with relatively low metal content. Mixed ionic-electronic conductors ͑MIECs͒ have attracted a great deal of attention due to the variety of possible applications and interesting electrical properties.1-3 These materials are thought to be used in high-temperature electrochemical devices such as gas separation membranes and solid oxide fuel cell ͑SOFC͒ electrodes. 2,3The mixed conduction can be either an intrinsic property of singlephase materials ͑like cerium oxide and some rare-earth manganites͒ or a result of the mixture of ionic and electronic conductors ͑MIEC composite͒.3 The main advantage of the MIEC composite is the possibility for tailoring the properties according to optimized parameters for a specific application.3 In this context, the SOFC anode is the cermet ZrO 2 :Y 2 O 3 /Ni ͑YSZ/Ni͒, produced by the reduction of the precursor composite ZrO 2 :Y 2 O 3 /NiO ͑YSZ/NiO͒.4 Both the cermet and the oxide precursor are MIEC composites and must fulfill several requirements for a high-performance SOFC. An important issue regarding this anode material is the reduction of the Ni volume fraction for better matching of the thermal expansion coefficient with the electrolyte, while both high electric conductivity and catalytic activity must be preserved. 4 In fact, the final properties of the anode cermet are strongly dependent on the precursor composite, and various studies deal with the fabrication of the YSZ/NiO composite aiming for the production of SOFC anodes, but rather few papers report a more detailed microstructural and electrical characterization of the precursor composite.5-7 The usually high temperatures ͑ജ1500°C͒ reported for the densification of the composite promote the YSZ destabilization or solid solution formation due to the reaction with NiO, resulting in a considerable reduction of the electrical conductivity. [8][9][10] It is well known that the electrical properties of composites depend not only on the electrical properties of each phase but also are strongly influenced by microstructu...

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“…Gadoliniumdoped ceria is an oxygen ion conductor with activation energy (Ea) values reported in the 0.6-1.0 eV interval, over a wide range of both temperature and oxygen partial pressure (20). On the other hand, NiO is a p-type semiconductor, which exhibits a discontinuity in the Arrhenius plots at a temperature close to the Néel temperature (T N ~250°C) (21). The (22,23).…”

Section: Resultsmentioning

confidence: 99%

Study of Ceria-Nickel Composites for Anode Catalytic Layer for Direct Ethanol SOFC

Fonseca¹,

Tabuti²,

Noronha³

et al. 2013

ECS Trans.

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A hydrothermal route was used to synthesize gadolinia-doped ceria with highly dispersed Ni particles. The microstructural and electrical properties of the cermet revealed that Ni attained percolation at relatively low volume fraction. The cermet was used as a catalytic layer deposited onto the standard Ni-based anode and allowed for the stable operation under ethanol. No evidence of carbon deposits was identified after 50 hours of continuous operation under dry ethanol. Such a result was attributed to both the catalytic properties of the ceria layer and the operation mechanism of gradual internal reforming.

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Anomalies in the electrical conductivity of nickel oxide above room temperature

Cited by 31 publications

References 11 publications

Electrical properties of YSZ/NiO composites prepared by a liquid mixture technique

Electrical properties of YSZ/NiO composites prepared by a liquid mixture technique

Mixed Ionic–Electronic YSZ/Ni Composite for SOFC Anodes with High Electrical Conductivity

Study of Ceria-Nickel Composites for Anode Catalytic Layer for Direct Ethanol SOFC

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