Fabrication of oxidation-resistant β-FeSi2 film on Mg2Si by RF magnetron-sputtering deposition

We study the oxidation of Mg2Si and analyze its kinetics using the Johnson–Mehl–Avrami (JMA) equation. Above 450 °C, Mg2Si reacts with O2 in air to yield MgO and Si. The Avrami exponent (n) is equal to ∼0.5, and it depends on the reaction temperature and time; this indicates that the oxidation is controlled by the diffusion-controlled reaction. In order to improve the oxidation-resistance of Mg2Si, β-FeSi2 films were fabricated on sintered Mg2Si samples by RF magnetron-sputtering deposition at RT followed by post-annealing at 600 °C in vacuum. An oxide layer having a thickness of 8 ± 3 μm was observed on the uncoated Mg2Si samples after heat treatment in air at 600 °C for 3 h. However, no oxide layer was formed on Mg2Si samples coated with 0.7-μm thick β-FeSi2 films. The β-FeSi2 layer effectively prevented the diffusion of oxygen at 600 °C and improved the oxidation-resistance of Mg2Si.