H 99 Ionic and electronic conductivity of La9.83-xPrxSi4.5Fe1.5O26 + or - delta apatites [] = Ionic and electronic conductivity of La9.83-xPrxSi4.5Fe1.5O26 + or - delta apatites / A. A. Yaremchenko, A. L. Shaula, V. V. Kharton, J. C. Waerenborgh, D. P. Rojas, M. V. Patrakeev, F. M. B. Marques // Solid State Ionics. - 2004. - V. 171, N 1-2. - С. 51-59. - Библиогр.: с. 59 (30 назв.) . - ISSN 0167-2738 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): АПАТИТЫ -- ИОННАЯ ПРОВОДИМОСТЬ -- ПРОВОДИМОСТЬ ИОННАЯ -- ЧИСЛА ПЕРЕНОСА -- ЭЛЕКТРОННАЯ ПРОВОДИМОСТЬ -- ПРОВОДИМОСТЬ ЭЛЕКТРОННАЯ -- ИМПЕДАНС -- ТВЕРДЫЕ ЭЛЕКТРОЛИТЫ -- ЭЛЕКТРОЛИТЫ ТВЕРДЫЕ -- ОКСИДЫ -- МЕССБАУЭРОВСКАЯ СПЕКТРОСКОПИЯ -- СПЕКТРОСКОПИЯ МЕССБАУЭРОВСКАЯ Аннотация: The incorporation of praseodymium in the apatite-type lattice of La9.83-xPrxSi4.5Fe1.5O26 + or - delta (x = 0-6) decreases the unit cell volume, suppresses Fe4+ formation according to Mossbauer spectroscopy, and increases p- and n-type electronic contributions to total conductivity, studied by the impedance spectroscopy and modified faradaic efficiency (FE) and electromotive force (EMF) methods at 973-1223 K. The additions of praseodymia have no essential effect on the ionic transport, with an activation energy of 99-109 kJ/mol, under oxidizing conditions. Contrary to the Al-containing analogue, La9.83Si4.5Al1.5O26, exhibiting p(O2)-independent conductivity at oxygen pressures from 10(-20) to 0.5 atm, the ionic conductivity of La9.83-xPrxSi4.5Fe1.5O26 + or - delta decreases on reducing p(O2) below 10(-14)-10(-12) atm. The observed behavior suggests a presence of hyperstoichiometric oxygen, critical for the level of ionic conduction and compensated by the formation of Fe4+ or Pr4+. The ion transference numbers in air vary in the range 0.979-0.994 for La9.83-xPrxSi4.5Fe1.5O26+delta, whilst for La9.83Si4.5Al1.5O26 the p-type electronic contribution to the total conductivity is lower than 0.5%. The average thermal expansion coefficients (TECs) of silicate-based solid electrolytes are (8.8-9.4)x10(-6)K(-1) at 300-1200 K and (14.2-15.8)x10(-6)K(-1) at 1200-1350 K |