Production of iron-disilicide thermoelectric devices and thermoelectric module by the slip casting method

FeSi2 thermoelectric devices and thermoelectric modules were produced by the slip casting method, and their thermoelectric properties were evaluated. The starting materials were Fe0.91Mn0.09Si2 (p-type) and Fe0.98Co0.02Si2 (n-type). The powder concentration was 77 mass%, and the hydrogen exponents of p- and n-type were 8.5 and 7, respectively. The p- and n-type slips were simultaneously poured into a mold. The green body was demolded in approximately 10 min, then dried at 353 K for about 3 h in air. It was then sintered at 1443 K for 3 h, and annealed at 1123 K for 14 h. Both the sintering and annealing were performed in a vacuum of 10−2 Pa. The p–n junctions were formed within the range of 10 mm from the edge of the hot junction. The electrode was formed by silver brazing. Reliable electrodes can be obtained by adding ε-phase powder or nickel powder. They formed ohmic contacts with β-FeSi2. The open circuit voltage, the internal resistance and the maximum power output of the thermoelectric module consisting of 20 devices were 5.25 V, 15.2 Ω and 0.45 W, respectively, for the maximum temperature difference (=572 K).