Ordered-Defect Sulfides as Thermoelectric Materials
The thermoelectric behavior of the transition-metal disulfides n-type NiCr2S4 and p-type CuCrS2 has been investigated. Materials prepared by high-temperature reaction were consolidated using cold-pressing and sintering, hot-pressing in graphite dies or spark-plasma sintering in tungsten carbide dies. The consolidation conditions have a marked influence on the electrical transport properties. In addition to the effect on sample density, altering the consolidation conditions results in changes to the sample composition, including the formation of impurity phases. Maximum room-temperature power factors were 0.18 mW m−1 K−2 and 0.09 mW m−1 K−2 for NiCr2S4 and CuCrS2, respectively. Thermal conductivities of ca. 1.4 W m−1 K−1 and 1.2 W m−1 K−1 lead to figures of merit of 0.024 and 0.023 for NiCr2S4 and CuCrS2, respectively.