Gel-combustion synthesis of CoSb2O6 and its reduction to powdery Sb2Co alloy

Abstract

Sb 2 Co alloy in powdery form was synthesized via reduction with gaseous hydrogen of the oxide CoSb 2 O 6 , obtained by the citrate gel-combustion technique. The precursor was an aqueous solution of antimony nitrate, cobalt nitrate and citric acid. The precursor solution with mole ratio Co(II)/Sb(V) of 1:2 was gelatinized by evaporation of water. The gel was heated in air up to the temperature of self-ignition. The product of gel combustion was a mixture of oxides and it had to be additionally thermally treated in order to be converted to pure CoSb 2 O 6 . The reduction of CoSb 2 O 6 by gaseous hydrogen yielded powdery Sb 2 Co as the sole phase. The process of oxide reduction to alloy was controlled by thermogravimetry, while X-ray diffractometry was used to control the phase compositions of both the oxides and alloys.

Nanosize La-filled CoSb3 skutterudite fabricated by electrospinning

“…Nevertheless, stability studies of such oxide phases under hydrogen and studies about their formation are rare and we have only found two that seems to confirm our reduction stage hypothesis (validated by the H 2 -TPR quantitative analysis). The first reported shows that the oxidation of CoSb 3 leads to a formation of CoSb 2 O 4 , CoSb 2 O 6 , and Sb 2 O 4[65], whereas the second study indicates that CoSb 2 is the final product of the reduction of CoSb 2 O 6 under hydrogen at temperatures ≥ 650 °C[66]. The formation of CoSb 3 can be explained by solid-state reaction (Eq.…”