Spark Plasma synthesis and diffusion of Cu and Ag in vanadium mixed valence oxides |
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Authors: | Jean Galy J Ph Monchoux |
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Affiliation: | (1) Centre d’Elaboration de Matériaux et d’Etudes Structurales-CNRS, 29, rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France |
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Abstract: | Spark Plasma sintering (SPS) technique allows powders to be compacted at low temperature with a very short holding time. The
powder loaded into a carbon die is heated via direct current pulses and simultaneously submitted to an uni-axial pressure
of several MPa. Full density of the sample is achieved within minutes. This process is used to study Cu and Ag metals interactions
with V2O5 oxide. Syntheses of M
x
V2O5 phases (M = Cu, Ag) have been achieved within minutes. Thus Cu and Ag atoms penetrate microcrystals of V2O5 oxide at a high speed, shearing its crystal network and simultaneously rebuilding the crystal structures of the prototype
networks β, β′, ε or δ M
x
V2O5. To account for the formation of these phases identified by X-ray diffraction, structural mechanisms are proposed. Cu and
Ag atomic diffusion parameters have been determined from energy dispersive X-ray spectroscopy (EDX) and electron micropobe
analysis (EPMA) line scans. High values of diffusion coefficients have been determined. Cu atoms diffuse faster than Ag, D
Cu ≈ 4 × 10−8 m2/s and D
Ag ≈ 0.5–1 × 10−9 m2/s in ε and δ M
x
V2O5 phases, respectively. Their formation may also be used as a model for further investigations into the diffusion mechanisms
of atoms in solids and for a better understanding of the SPS process.
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