Improving the Thermoelectric Performance of Tetrahedrally Bonded Quaternary Selenide Cu 2 CdSnSe 4 Using CdSe Precipitates

The creation of a microstructure that allows electron transport while blocking phonons is considered to be ideal for improving the performance of thermoelectric materials. Various thermoelectric materials exhibiting high figure of merit due to decreased thermal conductivity based on a complex crystal structure and the creation of secondary phases that result in coherent interfaces with the matrix have been reported recently. We report herein a Cu2CdSnSe4–CdSe composite that exhibits low thermal conductivity (∼ 0.56 W m−1 K−1), resulting in high thermoelectric figure of merit (ZT) of ∼ 0.65 (at 725 K). The extremely low thermal conductivity of the composite is attributed to scattering of a wide spectrum of phonons at (1) coherent interfaces between the Cu2CdSnSe4 matrix and CdSe precipitates, (2) the multiple elements and complex crystal structure of Cu2CdSnSe4, and (3) nanovoids formed due to vaporization of Cd during hot pressing at 1073 K. In addition to the improved ZT, the compatibility factor of this composite material is very close to that of p-type Bi2Se3 at around 573 K, suggesting its importance for the development of segmented thermoelectric power generators for use in the intermediate temperature range with the promise of high efficiency.