Jw. Stevenson et al., Influence of cobalt and iron additions on the electrical and thermal properties of (La,Sr)(Ga,Mg)O3-delta, J ELCHEM SO, 147(9), 2000, pp. 3213-3218
(La,Sr)(Ga,Mg)O3-delta (LSGM) perovskite compositions doped with Co or Fe w
ere prepared by a combustion synthesis technique. Small doping levels of Co
or Fe (less than or equal to 10 mol% on the B-site) resulted in increased
electrical conductivity at low temperatures (due to the introduction of ele
ctronic charge carriers into the lattice), but at high temperatures the ele
ctrical conductivity was dominated by ionic conduction and was similar in m
agnitude to that of the base LSGM composition. Higher additions of Co or Fe
resulted in much higher electrical conductivity in which the electronic co
mponent was dominant. A reversible weight loss at elevated temperatures was
observed in all of the compositions as the lattice oxygen stoichiometry de
creased with increasing temperature. This loss of lattice oxygen correlated
with a reduction in the rate of increase (or even a net decrease) in elect
rical conductivity with increasing temperature. This behavior was attribute
d to the elimination of electronic charge carriers (and a reduction in vale
nce of some of the Co or Fe cations in the material) as lattice oxygen vaca
ncies were formed. The thermal expansion of the materials increased substan
tially with increasing Co content, while only slight increases in thermal e
xpansion were observed with increasing Fe content. (C) 2000 The Electrochem
ical Society. S0013-4651(00)01-088-0. All rights reserved.