Kinetic analysis of the reduction of a ternary system of Bi, Sb and Te oxides by hydrogen for BiSbTe3 synthesis

Abstract

Reduction in a hydrogen atmosphere of Bi2O3, Sb2O3 and TeO2 mixes oxides for the synthesis of BiSbTe3 was analysed. The reduction reactions of Sb2O3 and Sb2O4 oxides, as well as Bi2O3+Sb2O3 and Sb2O3+3TeO2 mixtures, were also evaluated. The reduction of Sb2O4 is investigated for the first time. The reactions of the mixed oxides systems also were not the subject of research so far despite being used for synthesis of the (Bi,Sb)2Te3 material. The study comprised of kinetic analysis of TGA curves performed with non-parametric and isoconversional methods. Insight into powders’ structure during the process was taken to identify processes taking place. The results show, that Sb2O3 present in the reduced oxidizes to Sb2O4. This redox process between Sb oxide and another oxide takes place directly. The self-heating effect caused by elemental tellurium is diminished in the presence of Bi, because Bi-Te phases decrease the content of the elemental Te.