Improvement of thermoelectric properties for FeSi2 by addition of oxide

Abstract

In resent years, there are various energy problems and environmental problems, such as the lack of fossil fuels and global warming, due to the burning of fossil fuels that lead to the generation of CO2 and NOx. Therefore, successive studies have been carried out using thermoelectric power, which can convert thermal energy into electric energy directly using temperature differences. Our goal is the improvement of thermoelectric properties for FeSi2. FeSi2 is a cheap and eco-friendly resource. We investigated the decrease in thermal conductivity of FeSi2 by the addition of oxide. Fe, Si and Co powders were mixed to form the composition n-type FeSi2. Oxide was added to the sample and they were mixed. The resulting powder was molded at 153 MPa in a 10 mmφ die. The molded sample was calcined at 670 K for five hours in air atmosphere, calcined at 1463 K for two hours in a vacuum, and then heat-treated at 1033 K for twelve hours keeping in a vacuum. And thermoelectric properties were measured by DC method, four-probe method and laser flash method. As for figure of merit, n-type FeSi2 added with 1 wt% of Dy2O 3 and 3 wt% of Ta2O5 showed higher value than the unadditive n-type FeSi2. The highest performance was 0.3×10-3 K-1 at 614 K on the n-type FeSi2 added with 1 wt% of Dy2O3. As for dimensionless figure of merit, the highest performance was 0.24 at 864 K on the n-type FeSi2 added with 3 wt% of Ta2O5.