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Solid solubility and transport properties of Ce1−xNdxO2−δ nanocrystalline solid solutions by a sol-gel route

Published online by Cambridge University Press:  31 January 2011

Liping Li
Affiliation:
Physics Department, Jilin University, Changchun 130023, People's Republic of China
Xiaomin Lin
Affiliation:
Physics Department, Jilin University, Changchun 130023, People's Republic of China
Guangshe Li*
Affiliation:
Research Center of Supercritical Fluid Technology, Department of Chemical Engineering, Tohoku University, Sendai 980–8579, Japan
Hiroshi Inomata
Affiliation:
Research Center of Supercritical Fluid Technology, Department of Chemical Engineering, Tohoku University, Sendai 980–8579, Japan
*
b) Address all correspondence to this author. e-mail: guangshe@hotmail.com
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Abstract

Ce1−xNdxO2−δ (x = 0.05 to 0.55) nanocrystalline solid solutions were prepared by a sol-gel route. X-ray diffraction analysis showed that Ce1−xNdxO2−δ crystallized in a cubic fluorite structure. The lattice parameter for the solid solutions increased linearly with the dopant content. The solid solubility of Nd3+ in ceria lattice was determined to be about x = 0.40 in terms of the nearly constant lattice parameters at a dopant level larger than x = 0.40. First-order Raman spectra for Ce1−xNdxO2−δ at a lower dopant content exhibited one band associated with the F2g mode. At higher dopant contents, F2g mode became broadened and asymmetric, and a new broad band appeared at the higher frequency side of the F2g mode. This new band was assigned to the oxygen vacancies. The electron paramagnetic resonance spectrum for x = 0.05 showed the presence of O2 adsorbed on sample surface at g = 2.02 and 2.00 and of Ce3+ with a lower symmetry at g = 1.97 and 1.94. Further increasing dopant content led to the disappearance of the signals for O2. Impedance spectra showed the bulk and grain boundary conduction in the solid solutions. The bulk conduction exhibited a conductivity maximum and an activation energy minimum with increasing dopant content. Ce0.80Nd0.20O2−δ was determined to give promising conduction properties such as a relatively high conductivity of σ700 °C = 2.44 × 10−2 S cm−1 and moderate activation energy of Ea = 0.802 eV. The variations of conductivity and activation energy were explained in terms of relative content of oxygen vacancies Vö and defect associations {CeCe ′Vö}/{NdCe ′Vö}.

Type
Articles
Copyright
Copyright © Materials Research Society 2001

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