Reduction behavior of SnO 2 in the tin-bearing iron concentrates under CO–CO 2 atmosphere. Part II: Effect of quartz

Formation mechanisms of Fe3-xSnxO4 by a chemical vapor transport (CVT) process

Our former study reported that Fe-Sn spinel (Fe_3-xSn_xO₄) was easily formed when SnO₂ and Fe₃O₄ were roasted under CO-CO₂ atmosphere at 900-1100 °C. However, the formation procedure is still unclear and there is a lack of theoretical research on the formation mechanism of the Fe-Sn spinel. In this work, the reaction mechanisms between SnO₂ and Fe₃O₄ under CO-CO₂ atmosphere were determined using XRD, VSM, SEM-EDS, XPS, etc. The results indicated that the formation of Fe_3-xSn_xO₄ could be divided into four steps: reduction of SnO₂ to solid phase SnO, volatilization of gaseous SnO, adsorption of gaseous SnO on the surface of Fe₃O₄, and redox reaction between SnO and Fe₃O₄. During the roasting process, part of Fe³⁺ in Fe₃O₄ was reduced to Fe²⁺ by gaseous SnO, and meanwhile Sn²⁺ was oxidized to Sn⁴⁺ and entered into Fe_3-xSn_xO₄. The reaction between SnO₂ and Fe₃O₄ could be summarized as Fe₃O₄ + xSnO_(g) → Fe_3-xSn_xO₄ (x = 0-1.0).