Phase Stability and Thermoelectric Properties of CuFeS2-Based Magnetic Semiconductor

Recently, based on measurement results below 400 K, we suggested that chalcopyrite CuFeS₂-based alloys hold promise as thermoelectric materials. In this study, we have investigated the phase stability of such compounds and measured their thermoelectric properties at temperatures above 400 K. Thermogravimetric data indicate that the samples synthesized by a spark plasma sintering method were stable up to 700 K, above which sulfur deficiency becomes prominent. The electrical resistivity of the electron-doped samples showed metallic behavior up to 700 K. The Seebeck coefficients show large negative values of about ?300 μV/K above 400 K. As a result, the power factor of Cu_0.97Fe_1.03S₂ is ~1 mW/K²m in the temperature range of 400 K to 600 K.