O-97 Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes [] = Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes / V. V. Kharton, A. L. Shaula, M. V. Patrakeev, J. C. Waerenborgh, D. P. Rojas, N. P. Vyshatko, E. V. Tsipis, A. A. Yaremchenko, F. M. B. Marques // Journal of the Electrochemical Society. - 2004. - V. 151, N 8. - С. A1236-A1246. - Библиогр.: с. A1246 (35 назв.) . - ISSN 0013-4651 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): КИСЛОРОД -- ИОНЫ -- ИОННЫЙ ПЕРЕНОС -- ЭЛЕКТРОЛИТЫ -- СТРУКТУРА ТИПА АПАТИТА -- ТВЕРДЫЕ ЭЛЕКТРОЛИТЫ -- ЭЛЕКТРОЛИТЫ ТВЕРДЫЕ -- ИОННАЯ ПРОВОДИМОСТЬ -- ПРОВОДИМОСТЬ ИОННАЯ -- ДОБАВКИ -- ИСТОЧНИКИ ТОКА -- ИОНЫ КИСЛОРОДА -- ЖЕЛЕЗО -- Fe Аннотация: The oxygen ionic conductivity of apatite-type La9.83Si4.5Al1.5-yFeyO26 + - delta (y = 0-1.5), La10-xSi6-yFeyO26 + - 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, Al)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 Fe3+ 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)x10(-6) K(-1) at 300-1250 K |