Total and hole conductivity in the BaZr1 − x Y x O3 − α system (x = 0.02−0.20) in oxidizing atmosphere

Кузьмин, А. В.; Balakireva, V. B.; Плаксин, С. В.; Горелов, В. П.

doi:10.1134/s1023193509120064

Cited by 31 publications

(17 citation statements)

References 11 publications

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“…Such discrepancy might be partly due to the difference in the atmosphere for measurement. For example, the transport number reported by Kuz'min et al [38] is around 0.67 for BaZr0.9Y0.1O3-δ in moist air, but smaller values are obtained by Zhu [37] (~ 0.5) and this work (0.38) in moist oxygen atmosphere. Such difference is considered to be due to the decreased contribution of ionic conduction with the increasing partial pressure of oxygen.…”

Section: Discussioncontrasting

confidence: 54%

Transport properties of acceptor-doped barium zirconate by electromotive force measurements

Han

Noda

Onishi

et al. 2016

International Journal of Hydrogen Energy

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In this work, a systematic work was performed to investigate the electrochemical transport properties of acceptor-doped BaZrO3 by measuring electromotive force on various gas concentration cells. For the measurements in the wet oxidizing atmosphere, where significant hole conduction occurs, the transport numbers of the ionic conduction in the oxidizing atmosphere were corrected by taking the effect of electrode polarization into consideration. The results revealed that regardless of whether Sc, Y, In, Ho, Er, Tm or Yb was doped, proton conduction predominates in the reducing atmosphere with the transport number close to unit. However, the contribution of ionic conduction weakens, and the contribution of hole conduction enhances, when the samples are exposed to the moist oxidizing atmosphere. In addition, introducing Ba-deficiency results in degraded electrochemical conductivity, but the transport number in either the moist reducing or the moist oxidizing atmosphere does not change obviously.

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Section: Discussioncontrasting

confidence: 54%

Transport properties of acceptor-doped barium zirconate by electromotive force measurements

Han

Noda

Onishi

et al. 2016

International Journal of Hydrogen Energy

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“…Hole conductivity in Y-doped BaZrO 3 has been measured by several research groups. [6][7][8][9] When fitted to the Arrhenius-like expression T σ h = Ae −Ea/kT (8) these conductivities (σ h ) yield activation energies (E a ) within the range of 0.6 eV to 1.1 eV. In previous work 24 we calculated the activation energy for the hole conductivity based on the endothermic oxidation reaction in Eq.…”

Section: Hole Conductivitymentioning

confidence: 99%

“…One of the most promising materials in this aspect is acceptordoped BaZrO 3 since it combines high proton conductivity with chemical stability, and with yttrium as dopant currently yields the best performance. [1][2][3][4][5] Several experimental studies [6][7][8][9] have revealed that besides being a proton conductor, Y-doped BaZrO 3 is also an oxide ion and hole conductor. With the presence of multiple conducting species there is a possibility for different applications, which for optimal performance will require a profound understanding of these charge carriers.…”

Section: Introductionmentioning

confidence: 99%

Polaronic contributions to oxidation and hole conductivity in acceptor-dopedBaZrO3

2016

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Acceptor-doped perovskite oxides like BaZrO3 are showing great potential as materials for renewable energy technologies where hydrogen acts an energy carrier, such as solid oxide fuel cells and hydrogen separation membranes. While ionic transport in these materials has been investigated intensively, the electronic counterpart has received much less attention and further exploration in this field is required. Here, we use density functional theory (DFT) to study hole polarons and their impact on hole conductivity in Y-doped BaZrO3. Three different approaches have been used to remedy the self-interaction error of local and semi-local exchange-correlation functionals: DFT+U , pSIC-DFT and hybrid functionals. Self-trapped holes are found to be energetically favorable by about −0.1 eV and the presence of yttrium results in further stabilization. Polaron migration is predicted to occur through intraoctahedral transfer and polaron rotational processes, which are associated with adiabatic barriers of about 0.1 eV. However, the rather small energies associated with polaron formation and migration suggest that the hole becomes delocalized and band-like at elevated temperatures. These results together with an endothermic oxidation reaction [A. Lindman et al., Phys. Rev. B 91, 245114 (2015)] yield a picture that is consistent with experimental data for the hole conductivity. The results we present here provide new insight into hole transport in acceptor-doped BaZrO3 and similar materials, which will be of value in the future development of sustainable technologies.

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“…Total and partial conductivities of yttrium-doped BaZrO 3 have been determined experimentally by several research groups. [20][21][22][23]61 With a fit to the Arrhenius like expression…”

Section: Conductivitymentioning

confidence: 99%

“…the reported hole conductivities σ h yield activation energies E a in the range 0.62 eV to 1.05 eV. [20][21][22][23] To compare the experimental hole conductivities with our results for the hole concentrations the mobility of the holes is required. While the mobility and hence the diffusion coefficient have been experimentally determined for both protons and oxygen vacancies in yttrium-doped BaZrO 3 , the hole mobility is unknown.…”

Section: Conductivitymentioning

confidence: 99%

Implications of the band gap problem on oxidation and hydration in acceptor-doped barium zirconate

Lindman

Erhart²,

Wahnström³

2015

Phys. Rev. B

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Charge carrier concentrations in acceptor-doped proton-conducting perovskites are to a large extent determined by the hydration and oxidation of oxygen vacancies, which introduce protons and holes, respectively. First-principles modeling of these reactions involves calculation of formation energies of charged defects, which requires an accurate description of the band gap and the position of the band edges. Since density-functional theory (DFT) with local and semi-local exchangecorrelation functionals (LDA and GGA) systematically fails to predict these quantities this can have serious implications on the modeling of defect reactions. In this study we investigate how the description of band gap and band edge positions affects the hydration and oxidation in acceptordoped BaZrO3. First-principles calculations are performed in combination with thermodynamic modeling in order to obtain equilibrium charge carrier concentrations at different temperatures and partial pressures. Three different methods have been considered: DFT with both semi-local (PBE) and hybrid (PBE0) exchange-correlation functionals, and many-body perturbation theory within the G0W0-approximation. All three methods yield similar results for the hydration reaction, which are consistent with experimental findings. For the oxidation reaction, on the other hand, there is a qualitative difference. PBE predicts the reaction to be exothermic while the two others predict an endothermic behavior. Results from thermodynamic modeling are compared with available experimental data, such as enthalpies, concentrations and conductivities, and only the results obtained with PBE0 and G0W0, with an endothermic oxidation behavior, give a satisfactory agreement with experiments.

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Total and hole conductivity in the BaZr1 − x Y x O3 − α system (x = 0.02−0.20) in oxidizing atmosphere

Cited by 31 publications

References 11 publications

Transport properties of acceptor-doped barium zirconate by electromotive force measurements

Transport properties of acceptor-doped barium zirconate by electromotive force measurements

Polaronic contributions to oxidation and hole conductivity in acceptor-dopedBaZrO3

Implications of the band gap problem on oxidation and hydration in acceptor-doped barium zirconate

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