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Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes

Kharton, V. V. ; Shaula, A. L. ; Patrakeev, M. V. ; Waerenborgh, J. C. ; Rojas, D. P. ; Vyshatko, N. P. ; Tsipis, E. V. ; Yaremchenko, A. A. ; Marques, F. M. B.

Journal of the Electrochemical Society, 2004, Vol.151 (8), p.A1236-A1246 [Periódico revisado por pares]

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  • Título:
    Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes
  • Autor: Kharton, V. V. ; Shaula, A. L. ; Patrakeev, M. V. ; Waerenborgh, J. C. ; Rojas, D. P. ; Vyshatko, N. P. ; Tsipis, E. V. ; Yaremchenko, A. A. ; Marques, F. M. B.
  • É parte de: Journal of the Electrochemical Society, 2004, Vol.151 (8), p.A1236-A1246
  • Notas: ObjectType-Article-2
    SourceType-Scholarly Journals-1
    ObjectType-Feature-1
    content type line 23
  • Descrição: The oxygen ionic conductivity of apatite-type La9.83Si4.5Al1.5-yFeyO26-delta (y = 0-1.5), La10-xSi6-yFeyO26plus/minus delta (x = 0-0.77; y = 1-2), and La7-xSr3Si6O26-delta (x = 0-1) increases with increasing oxygen content. The ion transference numbers, determined by faradaic efficiency measurements at 973-1223 K in air, are close to unity for La9.83Si4.5Al1.5-yFeyO26+delta and La10Si5FeO26.5, and vary in the range 0.96-0.99 for other compositions. Doping of La9.83(Si,5Al)6O26 with iron results in an increasing Fe4+ fraction, which was evaluated by Mossbauer spectroscopy and correlates with partial ionic and p-type electronic conductivities, whereas La-stoichiometric La10(Si, Fe)O26+delta apatites stabilize the Fe 3+ state. Among the studied materials, the highest ionic and electronic transport is observed for La10Si5FeO26.5, where oxygen interstitials are close neighbors of Si-site cations. Data on transference numbers, total conductivity, and Seebeck coefficient as a function of the oxygen partial pressure confirm that the ionic conduction in Fe-substituted apatites remains dominant under solid oxide fuel cell operation conditions. However, reducing p(O2) leads to a drastic decrease in the ionic transport, presumably due to a transition from the prevailing interstitial to a vacancy diffusion mechanism, which is similar to the effect of acceptor doping. Iron additions improve the sinterability of silicate ceramics, increase the n-type electronic conductivity at low p(O2), and probably partly suppress the ionic conductivity drop. The thermal expansion coefficients of apatite solid electrolytes in air are (8.8-9.9) x 10-6 K-1 at 300-1250 K.
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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