resumo
The oxygen hyperstoichiometry of K2NiF4-type La2Ni0.9Fe0.1O4+delta, studied by thermogravimetric analysis and coulometric titration in the oxygen partial pressure range 6 x 10(-5)-0.7 atm at 923-1223 K, is considerably higher than that of undoped lanthanum nickelate. The p(O-2)-T-delta diagram of iron-doped lanthanum nickelate can be adequately described by introducing point-defect interaction energy in the concentration-dependent part of defect chemical potentials and accounting for the site-exclusion effects. The critical factors affecting the equilibrium oxygen incorporation process include coulombic repulsion of interstitial anions, trapping of the p-type electronic charge carriers by iron, and interaction between Fe3+ and holes localized on nickel cations. Due to low chemical expansion of La2Ni0.9Fe0.O-1(4+delta) lattice, the thermodynamic functions governing oxygen intercalation, site-blocking factors and hole mobility are all independent of the defect concentrations. The predominant 3+ state of iron cations under oxidizing conditions was confirmed by the Mossbauer spectroscopy. The stability of La2NiO4-based phase in reducing atmospheres is essentially unaffected by doping. (c) 2007 Elsevier Ltd. All rights reserved.
palavras-chave
TRANSPORT-PROPERTIES; PEROVSKITE-TYPE; ION-TRANSPORT; CONDUCTIVITY; LA2NIO4+DELTA; STABILITY; OXIDES; NI; CO; TEMPERATURE
categoria
Chemistry; Physics
autores
Tsipis, EV; Naumovich, EN; Patrakeev, MV; Waerenborgh, JC; Pivak, YV; Gaczynski, P; Kharton, VV
nossos autores
Vladislav Kharton
Investigador Principal CovidadoGrupos