Enhanced thermoelectric performance of chalcogenide Cu 2 CdSnSe 4 by ex-situ homogeneous nanoinclusions

Quaternary chalcogenide Cu2CdSnSe4 distributed with ex-situ homogeneous nanoinclusions has been synthesized by ball milling, followed by spark plasma sintering. The Cu2CdSnSe4 nanocrystallites with sizes ranging from 20 to 30 nm were prepared via colloidal synthesis, while the Cu2CdSnSe4 matrix was made by the traditional solid state reaction method. It is found that nanocrystallite inclusions strongly enhance electrical conductivity while preserving the Seebeck coefficient. In addition, these inclusions significantly reduce the lattice thermal conductivity through scattering phonons with all-scale length due to the polymorphous structure feature of Cu2CdSnSe4 composites. These concomitant effects result in an enhanced thermoelectric performance with the dimensionless figure of merit ZT reaching a peak value of 0.5 at 760 K, which is a 65% improvement compared to that of the pure Cu2CdSnSe4 matrix. These observations demonstrate an exciting scientific opportunity to raise the figure of merit via ex-situ homogeneous nanoinclusions, not only for quaternary chalcogenides but also for other promising thermoelectric materials.