On the variability of reported ionic conductivity in nanoscale YSZ thin films

Jiang, Jun; Hertz, Joshua L.

doi:10.1007/s10832-013-9857-1

Cited by 48 publications

(40 citation statements)

References 57 publications

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“…10%, as seen in experiment. 41,42 Thus, combining these two results with the results of we conclude that these simple EPP are able to describe oxygen-vacancy dynamics in crystalline HfO 2 very well.…”

Section: B Diffusion In Hfosupporting

confidence: 63%

Ion migration in crystalline and amorphous HfOX

Schie

Müller

Salinga

et al. 2017

The Journal of Chemical Physics

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The migration of ions in HfO x was investigated by means of large-scale, classical molecular-dynamics simulations over the temperature range 1000 ≤ T/K ≤ 2000. Amorphous HfO x was studied in both stoichiometric and oxygen-deficient forms (i.e., with x = 2 and x = 1.9875); oxygen-deficient cubic and monoclinic phases were also studied. The mean square displacement of oxygen ions was found to evolve linearly as a function of time for the crystalline phases, as expected, but displayed significant negative deviations from linear behavior for the amorphous phases, that is, the behavior was sub-diffusive. That oxygen-ion migration was observed for the stoichiometric amorphous phase argues strongly against applying the traditional model of vacancy-mediated migration in crystals to amorphous HfO 2 . In addition, cation migration, whilst not observed for the crystalline phases (as no cation defects were present), was observed for both amorphous phases. In order to obtain activation enthalpies of migration, the residence times of the migrating ions were analyzed. The analysis reveals four activation enthalpies for the two amorphous phases: 0.29 eV, 0.46 eV, and 0.66 eV (values very close to those obtained for the monoclinic structure) plus a higher enthalpy of at least 0.85 eV. In comparison, the cubic phase is characterized by a single value of 0.43 eV. Simple kinetic Monte Carlo simulations suggest that the sub-diffusive behavior arises from nanoscale confinement of the migrating ions. Published by AIP Publishing. [http://dx

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Section: B Diffusion In Hfosupporting

confidence: 63%

Ion migration in crystalline and amorphous HfOX

Schie

Müller

Salinga

et al. 2017

The Journal of Chemical Physics

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“…22,23 As a result there is a wide range of values for the conductivity of nanoscale YSZ. 12 The major reason for the divergent findings is the difficulty of controlling both the chemical composition and microstructure of the grain boundaries in polycrystalline ceramics. The concept of nanostructuring of solid electrolytes has also attracted the attention of many researchers due to the prospect of enhancing the proton conductivity at low temperatures.…”

Section: ■ Introductionmentioning

confidence: 99%

Ionic Conductivity of Mesostructured Yttria-Stabilized Zirconia Thin Films with Cubic Pore Symmetry—On the Influence of Water on the Surface Oxygen Ion Transport

Elm

Hofmann

Suchomski

et al. 2015

ACS Appl. Mater. Interfaces

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Thermally stable, ordered mesoporous thin films of 8 mol % yttria-stabilized zirconia (YSZ) were prepared by solution-phase coassembly of chloride salt precursors with an amphiphilic diblock copolymer using an evaporation-induced self-assembly process. The resulting material is of high quality and exhibits a well-defined three-dimensional network of pores averaging 24 nm in diameter after annealing at 600 °C for several hours. The wall structure is polycrystalline, with grains in the size range of 7 to 10 nm. Using impedance spectroscopy, the total electrical conductivity was measured between 200 and 500 °C under ambient atmosphere as well as in dry atmosphere for oxygen partial pressures ranging from 1 to 10(-4) bar. Similar to bulk YSZ, a constant ionic conductivity is observed over the whole oxygen partial pressure range investigated. In dry atmosphere, the sol-gel derived films have a much higher conductivity, with different activation energies for low and high temperatures. Overall, the results indicate a strong influence of the surface on the transport properties in cubic fluorite-type YSZ with high surface-to-volume ratio. A qualitative defect model which includes surface effects (annihilation of oxygen vacancies as a result of water adsorption) is proposed to explain the behavior and sensitivity of the conductivity to variations in the surrounding atmosphere.

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“…The bulk YSZ conductivity was obtained by linear regression of 9 different samples, compiled in Ref. 33. The conductivity of bulk GDC was obtained by linear regression of 3 different samples.…”

Section: Resultsmentioning

confidence: 99%

A Precise, Reduced-Parameter Model of Thin Film Electrolyte Impedance

McNealy

Jiang

Hertz

2015

J. Electrochem. Soc.

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The extreme shape factors inherent in characterizing thin film electrolytes can present a challenge to quantitative interpretation of impedance spectra. Here, the impedance of a thin film ceramic electrolyte with surface microelectrodes is modeled via direct numerical solution of current conservation. Faradaic and non-faradaic currents at the electrode-electrolyte interface are modeled phenomenologically using a formulation based on the Butler-Volmer equation. The model is able to reproduce complex, experimentally obtained impedance spectra for Pt/YSZ and Pt/GDC cells using only four adjustable, physically intuitive parameters: electrolyte conductivity, permittivity, exchange current density, and double layer capacitance. Equivalent circuit models typically used to fit these spectra instead require six or more adjustable parameters with ambiguous physical meaning. Notably, the model described here is able to capture a heretofore unexplained intermediate frequency arc seen in the experimental results. A parametric study enables the mechanism of the intermediate frequency feature to be identified as a spreading resistance in the electrolyte that vanishes at high frequencies due to low-impedance dielectric transport of current across the electrode-electrolyte interface. The fitting results are validated by comparison of the parameter values with literature reports.

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On the variability of reported ionic conductivity in nanoscale YSZ thin films

Cited by 48 publications

References 57 publications

Ion migration in crystalline and amorphous HfOX

Ion migration in crystalline and amorphous HfOX

Ionic Conductivity of Mesostructured Yttria-Stabilized Zirconia Thin Films with Cubic Pore Symmetry—On the Influence of Water on the Surface Oxygen Ion Transport

A Precise, Reduced-Parameter Model of Thin Film Electrolyte Impedance

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