resumo
Acceptor-type doping of perovskite-type La1-xSrxGa0.80-yMgyM0.20O3-delta (x = 0-0.20, y = 0.15-0.20, M = Fe, Co, Ni) leads to significant enhancement of ionic conductivity and oxygen permeability due to increasing oxygen vacancy concentration. The increase in strontium and magnesium content is accompanied, however, with increasing role of surface exchange kinetics as permeation-limiting factor. At temperatures below 1223 K, the oxygen permeation fluxes through La(Sr)Ga(Mg,M)O3-delta membranes with thickness less than 1.5 mm are predominantly limited by the exchange rates at membrane surface. The oxygen transport in transition metal-containing La(Sr)Ga(Mg)O3-delta ceramics increase in the sequence Co < Fe < Ni. The ionic conduction in these phases is, however, lower than that in the parent compounds, La1-xSrxGa1-yMgyO3-n. The highest level of oxygen permeation, comparable to that of La(Sr)Fe(CO)O-3- and La2NiO4-based phases, is observed for La0.90Sr0.10Ga0.65Mg0.15Ni0.20O3-delta membranes. The average thermal expansion coefficients of La(Sr)Ga (Mg,M)O3-delta ceramics in air are in range (11.6-18.4) x 10(-6) K-1 at 373-1273 K. Doping of LaGa0.65Mg0.15Ni0.20O3-delta with praseodymium results in moderate increase of the permeation fluxes, lower thermal expansion and an improved phase stability in reducing environments.
palavras-chave
IONIC-CONDUCTIVITY; ELECTRONIC CONDUCTIVITY; DOPED LAGAO3; LACO(M)O-3 M; PEROVSKITES; TRANSPORT; FE; OXIDE; CR; NI
categoria
Materials Science
autores
Yaremchenko, AA; Shaula, AL; Kharton, VV; Kovalevsky, AV; Naumovich, EN; Frade, JR; Marques, FBM
nossos autores
Aleksey Yaremchenko
Investigador Principal
Andrei Kavaleuski
Investigador principal
Fernando Manuel Bico Marques
Professor Catedrático
Jorge Ribeiro Frade
Professor(a) Jubilado(a)