resumo
The maximum solubility of aluminum cations in the perovskite lattice of Sr0.7Ce0.3Mn1-xAlO3-delta is approximately 15%. The incorporation of Al3+ increases oxygen ionic transport due to increasing oxygen nonstoichiometry, and decreases the tetragonal unit cell volume and thermal expansion at temperatures above 600 degrees C. The total conductivity Of Sr0.7Ce0.3Mn1-xAlxO3-delta (x=0-0.2), predominantly electronic, decreases with aluminum additions and has an activation energy of 10.2-10.9 kJ/mol at 350-850 degrees C. Analysis of the electronic conduction and Seebeck coefficient Of Sr0.7Ce0.3Mn0.9Al0.1O3-delta, Measured in the oxygen partial pressure range from 10(-18) to 0.5 atm at 700-950 degrees C, revealed trends characteristic of broad-band semiconductors, such as temperature-independent Mobility. The temperature dependence of the charge carrier concentration is weak, but exhibits a tendency to thermal excitation, whilst oxygen losses from the lattice have an opposite effect. The role of the latter factor becornes significant at temperatures above 800 degrees C and on reducing p(O-2) below 10(-4) to 10(-2) oxygen permeability of dense Sr0.7Ce0.3Mn1-xAlxO3-delta (x=0-0.2) membranes. limited by both bulk ionic COnCILICtiOll and SUrfaceexchange, is Substantially higher than that of (La, Sr)MnO3-based materials used for solid oxide fuel cell cathodes. The average thermal expansion coefficients of Sr0.7Ce0.3Mn1-xAlxO3-delta ceramics in air are (10.8-11.8) x 10(-6) K-1. (c) 2005 Elsevier Ltd. All rights reserved.
palavras-chave
OXIDE FUEL-CELLS; ELECTROCHEMICAL PROPERTIES; ELECTRICAL-PROPERTIES; SEEBECK COEFFICIENT; PEROVSKITES; PERFORMANCE; TECHNOLOGY; CONDUCTORS; MEMBRANES; CATHODE
categoria
Materials Science
autores
Marozau, IP; Kharton, VV; Viskup, AP; Frade, JR; Samakhval, VV
nossos autores
Jorge Ribeiro Frade
Professor(a) Jubilado(a)