Synthesis of bulk β-FeSi2 crystal

The feasibility of adopting two methods to synthesizing the bulk crystal of β-FeSi2 was examined: one involving two-step Bridgmann growth with a three-zone furnace and another involving melting growth with a single zone furnace. As-grown iron disilicides were annealed in the furnaces at different temperatures for various durations. Experimental results indicate that a larger β-FeSi2 crystal can be obtained using the two-step fast Bridgmann growth method with post-annealing at 1073 K for 300 h. Fast cooling and adding some copper impurities to the raw materials were found to promote the growth of β-Fesi2. The iron disilicide crystal, with a large contribution from the β phase, supported a higher thermoelectric power. A thermoelectric power of 450 μV/K was obtained at 300-900 K for the sample with copper doping. The energy band gap of β-FeSi2 samples was about 0.82-0.88 eV, determined by measuring the temperature-dependent resistivity.