Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10636993 | Solid State Sciences | 2005 | 11 Pages |
Abstract
Iron incorporation into lanthanum aluminate-based solid electrolyte leads to increasing oxygen ionic and p-type electronic conductivities. The oxygen ion transference numbers of perovskite-type La0.90Sr0.10Al0.85âxFexMg0.15O3âδ (x=0.2-0.4), determined by faradaic efficiency measurements in air, vary from 6.9Ã10â4 to 1.6Ã10â2 at 1073-1223 K, increasing with temperature and decreasing when iron content increases. In order to study the behavior of transition metal cations dissolved in a lattice of cations with stable oxidation state, the total conductivity and Seebeck coefficient of La0.90Sr0.10Al0.65Fe0.20Mg0.15O3âδ were measured at 1073-1223 K in the oxygen partial pressure range from 10â20 to 0.5 atm. The p-type electronic conduction dominating under oxidizing conditions, with hole mobility activation energy of 15 kJâmolâ1, occurs via a small-polaron mechanism. Reducing oxygen pressure results in increasing ionic conduction, which becomes predominant at p(O2) lower than 10â10 atm. The activation energy for ionic transport, 87-107 kJâmolâ1, decreases with reducing p(O2) due to a decreasing contribution of the vacancy formation enthalpy. Contrary to the Fe-substituted aluminates, dense ceramics of La(Sr)Al(Mg,M)O3âδ (M = Co, Ni) cannot be obtained under atmospheric oxygen pressure due to La2MO4-based phase segregation in the course of sintering at temperatures above 1400 K.
Keywords
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
E.V. Tsipis, V.V. Kharton, N.V. Vyshatko, J.R. Frade, F.M.B. Marques,