Improvement of thermoelectric power of n-type earth-abundant iron rich alloy by microstructure engineering

Due to the exhaustion of rare metal resources and the hazard of toxic material to the environment, development of cost-effective, nontoxic, and earth-abundant thermoelectric materials has become more urgent. This study introduces a nontoxic, earth abundant n-type iron-based cost-effective Fe-2.3C-Si-5Mn-7V-8Cr thermoelectric material that is prepared by a simple melting method. Significant increase in both electrical conductivity and Seebeck coefficient are achieved by several heat treatment processes to optimize the distribution and grain size of VC, Cr_23-xFe_xC₆ typed chromium carbide as well as base matrix. As a result, the power factor of the sample that is normalized at 1150 °C is about 0.75 mWm^-1K ^-2 in maximum value, which is 2.6 times larger than that (0.29 mWm^-1K^-2) of as-cast sample. The highest ZT value of the sample that is normalized at 1150 °C is 0.028 at 868 K, which is 4.3 times larger than that of as-cast sample (0.0065 at 964 K) in present study, indicating that a proper heat treatment process would remarkably enhance ZT value. This research provides extremely valuable data for the future researches on thermoelectric alloys.