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Hydrothermal Synthesis and Properties of Ce1−xMxO2-δ(M = La, Bi, Sm, Pr, Tb) Solid Solutions
Published online by Cambridge University Press: 10 February 2011
Abstract
A systematic study of hydrothermally prepared Ce1−x,MxO2−δ, (M= Sm, Bi, Pr, Tb; x= 0-0.30) solid solutions, promising materials for application in solid oxide fuel cells and oxygen membranes is presented. Ultrafine particles of uniform crystallite dimension, ∼ 20 nm can be formed in 30 min. under hydrothermal conditions (260°C, 10 MPa). The small particle size (20-50 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramics at 900-1350°C, significantly lower temperatures than 1600-1650°C required for samples prepared by solid state techniques. The solubility limit of Bi2O3, in CeO2, was determined to be around 20 mol. %. The maximum conductivity, σ600°C ∼ 4.4 × 10−3 S/cm with Ea = 1.01 eV, and σ600°C = 5.7 × 10−3 S/cm with Ea ≈ 0.9 eV was found at x= 0.20 and x= 0.17 for Bi and Sm, respectively. In the Ce-Pr/Tb oxide systems, in addition to the high oxide ion conductivity, electronic conductivity occurs through the hopping of small polarons by a thermally activated mechanism (electron hopping from the Pr3+/Tb3+ to a neighboring Pr4+/Tb4+ ion).
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- Copyright © Materials Research Society 1999
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