Structure and oxide anion conductivity in Ln2(TO4)O (Ln=La, Nd; T=Ge, Si) |
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| Authors: | Laura León-Reina Enrique R Losilla Miguel AG Aranda |
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| Institution: | a Laboratorio de Difracción de Rayos-X, Servicios Centrales de Apoyo a la Investigación, Universidad de Málaga, 29071 Málaga, Spain
b Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga, Spain |
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| Abstract: | Oxy-silicate and oxy-germanate, Ln2(TO4)O (Ln=La and Nd, T=Ge and Si) compounds have been prepared. Oxy-germanates can be readily obtained as highly crystalline single phases, while, the oxy-silicates are difficult to prepare as pure phases. The crystal structure of Nd2(SiO4)O has been studied from a joint Rietveld refinement of neutron and laboratory X-ray powder diffraction data. The electrochemical characterisation indicates that these compounds display oxide anion conductivity with p-type electronic contribution under oxidising conditions. The apparent activation energies under dry flowing nitrogen, where p-type contribution is minimised, are 0.97(1), 1.05(3) and 1.17(4) eV, for Nd2(SiO4)O, La2(GeO4)O and Nd2(GeO4)O, respectively. The overall conductivities at 1173 K range from 1.2×10−4 S cm−1 for Nd2(SiO4)O to 1.3×10−6 S cm−1 for La2(GeO4)O. Finally, the stability of these compounds under very reducing conditions has been studied and partial degradation is reported. |
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| Keywords: | Oxide anion conductivity p-type electronic conductivity Neutron diffraction Oxy-apatite |
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