Reaction mechanism and thermoelectric properties of In0:22Co4Sb12 prepared by magnesiothermy
Mécanismes de réaction et propriétés thermoélectriques de In0:22Co4Sb12 préparé par magnésiothermie
Résumé
The magnesioreduction synthesis of In 0.22 Co 4 Sb 12 with high In-rattler concentration from Sb 2 O 4 and In-doped Co 3 O 4 precursors is reported. This process directly yields a submicronic powder in a single step of 96 h at 810 K. The reaction mechanism has been investigated by stopping the reaction every 12 h and quantifying the existing phases by X-ray diffraction and Rietveld refinements. The precursors are first reduced in CoO and Sb 2 O 3 lower oxides, then form CoSb 2 O 6 and CoSb 2 O 4 intermediates which are finally reduced in In x Co 4 Sb 12. A powder with 350 nm average size and mostly composed of In-filled skutterudite phase with composition close to In 0.17 Co 4 Sb 12 is obtained. Upon spark plasma sintering, small residual amount of InSb reacts with the skutterudite matrix to form a single-phase densified pellet with composition close to In 0.22 Co 4 Sb 12. The resulting densified material with 1.8 µm average grain size shows a figureof-merit ZT max of 0.95 at 750 K.
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