Kinetic study on gas phase zinc reduction of silicon tetrachloride

Abstract

This report details a kinetic analysis on gas phase zinc reduction of silicon tetrachloride. Although this reaction has been known for at least several decades, and is expected to provide a new low cost production route for silicon materials for photovoltaic cells, little is known about the detailed reaction kinetics due to the difficulties in handling zinc vapor. Here, the reaction yields have been experimentally measured at various residence times using a quartz tube reactor over a range of temperatures from 870 °C to 1020 °C. Reaction yields increased to greater than 50% at 970 °C from ca. 20% at 870 °C when the residence time was 10 s. Possible elementary reaction steps have also been investigated by quantum chemical calculations. A two-step reaction model with SiCl 2 as an intermediate species has been proposed. This model describes the experimental data well. Furthermore, from experimental data and analytical solution of our reaction model, the overall reaction rate constants were obtained. The overall activation energy was 3.2 × 10 2 kJ mol −1.