Ab initio study of yttria-stabilized cubic zirconia surfaces

Ballabio, Gerardo; Bernasconi, Marco; Pietrucci, Fabio; Serra, Stefano

doi:10.1103/physrevb.70.075417

Cited by 69 publications

(88 citation statements)

References 22 publications

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“…During the MD simulations, we observe substantial diffusion of oxygen ions and, as a consequence, both left and right sides of the crystals are covered by half monolayers of oxygen ions, which we define as surface layers. The oxygen-terminated (0 0 1) surface of YSZ qualitatively agrees with medium-energy ion scattering (MEIS) experiments and ab initio calculations [57][58][59]. However, no cation moves away from its randomly chosen initial site during the equilibration even at high temperatures.…”

Section: Initializing Structuressupporting

confidence: 70%

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Atomistic simulations of surface segregation of defects in solid oxide electrolytes

2010

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Section: Initializing Structuressupporting

confidence: 70%

“…Method ( calculations [57][58][59]. On the other hand, depletion in the inner layers is due to the Coulomb repulsion between oxygen vacancies.…”

Section: Referencesmentioning

confidence: 99%

Atomistic simulations of surface segregation of defects in solid oxide electrolytes

2010

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“…9 %. The order of surface energies is the same as found for oxides with the fluorite structure such as UO 2 [18] and our substrate material cubic Y-stabilised ZrO 2 [21,22]. Thus for 24 % Y doped ZrO 2 , Ballabio et al [22] found relaxed surface energies γ(100) = 1.75 J/m 2 , γ(110) = 1.44 J/m 2 and γ(111) = 1.04 J/m 2 .…”

Section: Energetics Of Surfaces and Surface Structuresmentioning

confidence: 62%

“…The order of surface energies is the same as found for oxides with the fluorite structure such as UO 2 [18] and our substrate material cubic Y-stabilised ZrO 2 [21,22]. Thus for 24 % Y doped ZrO 2 , Ballabio et al [22] found relaxed surface energies γ(100) = 1.75 J/m 2 , γ(110) = 1.44 J/m 2 and γ(111) = 1.04 J/m 2 . Note, however, that the order of surface energies for In 2 O 3 is different to that proposed by Hao et al, who suggested a sequence γ(110) > γ(100) > γ(111) on the basis of the morphologies In 2 O 3 nanocrystals prepared by vapour transport [23].…”

Section: Energetics Of Surfaces and Surface Structuresmentioning

confidence: 62%

Dopant and Defect Induced Electronic States at In2O3 Surfaces

Egdell

2015

Defects at Oxide Surfaces

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This article reviews the impact of defects and doping on the surface electronic structure of indium oxide, a wide gap oxide semiconductor which under degenerate doping becomes an important transparent conducting material. Topics covered include recent evidence for carrier accumulation at In 2 O 3 surfaces when there is a low bulk doping level and the profound effects of doping on core and valence photoemission spectra. The importance of molecular beam epitaxy in growth of single crystal samples is emphasised. IntroductionTransparent conducting oxides (TCOs) combine the usually orthogonal properties of optical transparency in the visible region with a high electrical conductivity [1][2][3][4]. TCOs already find widespread application as the window electrode in display devices including liquid crystal displays and electroluminescent display devices. A TCO electrode is also an essential component in many designs of solar cell [5,6]. In addition there is a growing interest in "transparent electronics" where TCO materials are employed in a more active role, for example in light emitting diodes [7] or lasers operating in the ultraviolet regime. The TCO market is worth around $1.6 billion per annum, with upward of 80 % of this sum based on LCD displays. Indium oxide (In 2 O 3 ) is amenable to n-type doping with Sn to give a prototype TCO usually-but somewhat misleadingly-referred to as indium tin oxide or ITO. At present ITO dominates the TCO market as the material offers a better combination of conductivity and transparency than alternatives such as doped ZnO or SnO 2 . In principle, doped CdO could achieve better performance [8], but Cd is highly toxic. Despite some recent reports of respiratory disease and even deaths [9] among workers in the ITO industry, indium is generally regarded as relatively

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“…29 This is likely due to enrichment of yttrium at the surface. 31 Because at SOFC operating temperatures the vacancies are mobile, the surface and bulk vacancies are in dynamic equilibrium. Therefore, the surface and bulk vacancy fractions are related by the equilibrium of the reaction…”

Section: Chemistry and Thermodynamic Properties On Yszmentioning

confidence: 99%

Modeling Electrochemical Oxidation of Hydrogen on Ni–YSZ Pattern Anodes

Goodwin

Zhu

Colclasure

et al. 2009

J. Electrochem. Soc.

155

217

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A computational model is developed to represent the coupled behavior of elementary chemistry, electrochemistry, and transport in the vicinity of solid-oxide fuel cell three-phase boundaries. The model is applied to assist the development and evaluation of H 2 charge-transfer reaction mechanisms for Ni-yttria-stabilized zirconia ͑YSZ͒ anodes. Elementary chemistry and surface transport for the Ni and YSZ surfaces are derived from prior literature. Previously published patterned-anode experiments ͓J. Mizusaki et al., Solid State Ionics, 70/71, 52 ͑1994͔͒ are used to evaluate alternative electrochemical charge-transfer mechanisms. The results show that a hydrogen-spillover mechanism can explain the Mizusaki polarization measurements over wide ranges of gas-phase composition with both anodic and cathodic biases. Establishing elementary charge-transfer reaction pathways is one of the most difficult aspects of understanding the fundamental behavior of solid oxide fuel cells ͑SOFCs͒. Most modeling efforts represent charge transfer in terms of activation overpotentials and the Butler-Volmer equation. The objective of the present paper is to develop an elementary representation of the transport, chemistry, and electrochemistry in the vicinity of an anode three-phase boundary ͑TPB͒ between gas-phase H 2 , a Ni anode, and a yttria-stabilized zirconia ͑YSZ͒ electrolyte. The approach is based upon quantitative models and previously reported patterned-anode experiments by Mizusaki et al. Mizusaki et al.2 developed model anode structures using thin nickel films on single-crystal YSZ. The nickel films were patterned lithographically into an array of lines. By varying the linewidth and spacing, it was possible to control the TPB length per unit area. Others have followed Mizusaki's lead, and several experimental studies have been reported. [3][4][5][6][7] Nevertheless, Mizusaki's 1994 paper stands as the most complete data set available. The experiments were carefully designed to impose both cathodic and anodic potentials and to systematically vary the H 2 partial pressure while holding H 2 O partial pressure constant and vice versa.In addition to electrochemical charge transfer, the model simultaneously represents the competing processes of surface-diffusive transport and nonfaradaic chemistry on the Ni and YSZ surfaces. The reaction pathways and rates for thermal surface reactions are drawn from independent experimental and theoretical literature. The reaction mechanisms are constructed hierarchically, beginning with the nonfaradaic processes, and then adding charge-transfer reactions at the TPB, without modifying the rates or equilibrium constants for the nonfaradaic reactions. In this way, it is possible to develop robust reaction mechanisms that are applicable over wide ranges of operating conditions.The model is used to evaluate the validity of two alternative charge-transfer pathways. One is an oxygen-spillover mechanism in which the rate-limiting reaction involves atomic oxygen from the YSZ surface crossing over to the Ni...

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Ab initio study of yttria-stabilized cubic zirconia surfaces

Cited by 69 publications

References 22 publications

Atomistic simulations of surface segregation of defects in solid oxide electrolytes

Atomistic simulations of surface segregation of defects in solid oxide electrolytes

Dopant and Defect Induced Electronic States at In2O3 Surfaces

Modeling Electrochemical Oxidation of Hydrogen on Ni–YSZ Pattern Anodes

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