Cubic-stabilized zirconia and alumina composites as electrolytes in planar type solid oxide fuel cells

Mori, M.; Abe, Toshio; Itoh, Hibiki; Yamamoto, Osamu; Takeda, Yasuo; Kawahara, T

doi:10.1016/0167-2738(94)90206-2

Cited by 149 publications

(106 citation statements)

References 7 publications

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“…The Arrhenius plot for σ t , (b), is not linear, consistent with that reported for various YSZ samples on many other occasions. 3,7,8,10,28,29 This non-linearity is widely attributed to trapping of oxygen vacancies in vacancy-dopant complexes at low temperatures: 30 at higher temperatures, dissociation of the complexes occurs and the trapping enthalpy is not included in the activation energy. The total conductivity, σ t , at high temperatures, would therefore represent the hopping of free vacancies.…”

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confidence: 99%

“…Many data sets, especially for compositions that exhibit high oxide ion conductivity, show distinct curvature of the Arrhenius plots which is attributed to the trapping at lower temperatures of mobile oxide ion vacancies in vacancydopant defect complexes. 3,[7][8][9][10] Two possible defect complexes that are widely discussed are the charged dimer, (Y Zr V…”

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confidence: 99%

“…The high frequency plateau in C corresponds to a permittivity, of ∼25, using: [8] where e 0 is the permittivity of free space, 8.854 × 10 −14 Fcm −1 . This ε value is attributed to the bulk permittivity, ε ∞ of the crystal.…”

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Electrical Properties of Yttria-Stabilized Zirconia, YSZ Single Crystal: Local AC and Long Range DC Conduction

Vendrell

West

2018

J. Electrochem. Soc.

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Widely-used complex plane analysis of impedance data is insufficiently sensitive to characterize fully the bulk properties of YSZ single crystal. Instead, more extensive data analysis is needed which uses a combination of parallel, admittance-based formalisms and series, impedance-based formalisms. Bulk electrical properties are measured at higher frequencies and contain contributions from both long range conduction and local dielectric relaxation. At lower frequencies, electrode-sample contact impedances are measured and are included in full equivalent circuit analysis. The impedance of YSZ crystal of composition 8 mol% Y 2 O 3 in the (110) orientation, with Pt electrodes, was measured over the temperature range 150-750 • C and frequency range 0.01 Hz-3 MHz. Full data analysis required (i) a parallel constant phase element (CPE)-resistance (R) combination to model the electrode response, (ii) a series R-C element to represent local reorientation of defect dipoles and (iii) a R-C-CPE element to represent long range oxide-ion conduction; (ii) and (iii) together model the bulk response. The dielectric element underpins all discussions about defect structure and properties of YSZ but has not been included previously in analysis of impedance data. The new equivalent circuit that is proposed should allow better separation of bulk and grain boundary impedances of YSZ ceramics. Yttria-stabilized zirconia (YSZ) is a very well-known oxide ion conductor that is used as the solid electrolyte in solid oxide fuel cells and oxygen gas sensors.1-3 It usually takes the form of a high-density ceramic in which the bulk resistance in series with a grain boundary resistance gives the overall sample resistance. 4 In almost all cases, the grain boundary resistance is present and cannot be eliminated readily by attention to ceramic processing conditions. The nature of the grain boundary impedance is often unclear, although significant compositional differences from the bulk, associated with dopant segregation, may be involved. 5,6 In order to measure sample impedances, sample-electrode contacts are necessary and therefore, appropriate consideration of their associated impedances forms part of the overall impedance analysis. For YSZ, contact impedances include contributions from the blocking of oxide ions at the sample-electrode interface, charge transfer resistances associated with the O 2− /O 2 redox couple and the diffusion of O 2 molecules between the surrounding atmosphere and the sampleelectrode interface. Usually, electrode contact impedances are wellseparated on a frequency scale from bulk/grain boundary impedances because they have much higher associated capacitances, C: typically (1-10) × 10 −6 F for the electrode contact compared with ∼ 1 × 10 −10 F for a grain boundary capacitance and (2-3) × 10 −12 F for a bulk capacitance. Relaxation frequencies, ω, are given ideally by ωτ = 1, where τ = RC and therefore, the frequency maxima of impedance semicircles, arcs or peaks associated with bulk/grain boundary impedances are usuall...

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Electrical Properties of Yttria-Stabilized Zirconia, YSZ Single Crystal: Local AC and Long Range DC Conduction

Vendrell

West

2018

J. Electrochem. Soc.

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“…However, some data also indicates that such an addition improves mechanical properties, but reduces electrical conductivity [65][66][67]. Controversial increase in flexural strength up to 480 MPa, without changes of ionic conductivity, have also been reported [68].…”

Section: Zirconia -Baesed Electrolytesmentioning

confidence: 99%

Composite Oxide Electrolytes for Electrochemical Devices

Dudek¹

2008

Advances in Materials Sciences

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This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than monophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al 2 O 3 inclusions into cubic yttria -zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd 2 Ti 2 O 7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness K Ic of 8YSZ ceramics was also significantly improved by Nd 2 Ti 2 O 7 addition.Heterophase oxide ionic conductors in the system Calcium zirconate -cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO 3 is lower than that for calcia -stabilized zirconia (13CSZ). Hence CaZrO 3 -based materials perform better at low oxygen concentration at molten alloys.On the other hand composite layered ceramics involving Ce 0.8 Sm 0.2 O 2 /Bi 0.8 Eb 0.2 O 2 or Ce 0.9 Gd 0.1 O 2 /BaCe 0.8 Y 0.2 O 3 /Ce 0.9 Gd 0.1 O 1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600-800 o C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.

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“…The minimum grain boundary resistivity was reported at l0 wt% A1203. Other authors have reported a beneficial effect for the grain boundary conductivity at about 1 -2 wt% alumina level [3,4,7]. Drennan and Butler have reported that alumina acts as a scavenging agent for silica, a common impurity present in most zirconia powders [8].…”

Section: Introductionmentioning

confidence: 99%

The effect of alumina addition on the conductivity, microstructure and mechanical strength of zirconia — yttria electrolytes

Badwal

Ciacchi

Zelizko

1998

Ionics

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Abstract. The effect of alumina additions on the ionic conductivity and mechanical properties of 3 and 8 mol% Y203-ZrO 2 compositions has been investigated. Such materials are of interest for use in fuel cells and other similar applications. Sintered specimens were characterised by XRD, SEM, impedance spectroscopy, four -probe DC conductivity and mechanical strength measurements. Alumina additions had no affect on the conductivity degradation behaviour at 1000 ~ and the activation energy but resulted in an increase in the strength of 8 mol% Y203 -ZrO2 composition by about 25%. However, a significant drop in the ionic conductivity well above what could be accounted for by the decrease in the volume fraction of the conducting phase, was observed.

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Cubic-stabilized zirconia and alumina composites as electrolytes in planar type solid oxide fuel cells

Cited by 149 publications

References 7 publications

Electrical Properties of Yttria-Stabilized Zirconia, YSZ Single Crystal: Local AC and Long Range DC Conduction

Electrical Properties of Yttria-Stabilized Zirconia, YSZ Single Crystal: Local AC and Long Range DC Conduction

Composite Oxide Electrolytes for Electrochemical Devices

The effect of alumina addition on the conductivity, microstructure and mechanical strength of zirconia — yttria electrolytes

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