Rt. Baker et al., PROCESSING AND ELECTRICAL-CONDUCTIVITY OF PURE, FE-SUBSTITUTED AND CR-SUBSTITUTED LA0.9SR0.1GAO3, Journal of the European Ceramic Society, 18(2), 1998, pp. 105-112
The material La0.9S0.1GaO3 and four B-site substituted variants with 5
or 20% Fe or Cr for Ga substitution were prepared by solid stare reac
tion starting from oxide and carbonate precursors. The materials were
characterised by scanning electron microscopy (SEM), X-ray diffraction
(XRD) and impedance spectroscopy (IS) in air. The sintered samples ap
peared to have orthorhombic symmetry, had densities higher than 90% of
theoretical and had average grain sizes of approx. 1-2.5 mu m. Howeve
r, second phases were detected by XRD and SEM images showed evidence o
f a liquid, Sr-rich second phase in all samples. The high grain bounda
ry impedances measured were attributed to concentration of this second
phase at the grain boundaries. Generally, conductivity increased and
activation energy of conduction decreased with increasing degree of su
bstitution. Increasing p-type electronic conductivity involving CP3+/C
r4+ or Fe3+/Fe4+ couples is suggested. Raising the sintering temperatu
re of these materials was shown to increase both their average grain s
ize and their total conductivity. (C) 1997 Elsevier Science Limited.