Hole-doping effect on the thermoelectric properties and electronic structure of CoSi

Abstract

We report the effect of Al substitution on the temperature-dependent electrical resistivity, Seebeck coefficient, as well as thermal conductivity in the binary compound cobalt monosilicide. It is found that the substitution of Al onto the Si sites causes a dramatic decrease in the electrical resistivity and lattice thermal conductivity. A theoretical analysis indicated that the reduction of lattice thermal conductivity arises mainly from point-defect scattering of the phonons. For xу0.05 in the CoSi 1Ϫx Al x system, the Seebeck coefficient changes sign from negative to positive, accompanied by the appearance of a broad maximum. These features are associated with the change in the electronic band structure, where the Fermi level shifts downwards from the center of the pseudogap due to hole-doping effect. While the thermoelectric performance improves with increasing Al substitution, the largest figure-of-merit ZT value among these alloys is still an order of magnitude lower than the conventional thermoelectric materials.

Effects of Ge and B substitution on thermoelectric properties of CoSi

“…Secondly, crystal growth was performed on an optical floating zone system type FZ-20035W apparatus at a rate of 5-7. 5 crystals was determined by the X-ray Laue back scattering method.…”

Elastic, thermodynamic, and electronic properties of MnSi, FeSi, and CoSi

“…21 CoSi is a diamagnetic semimetal with very high residual resistivity, implying existence of a fairly large number of defects. 22 It was widely studied as a potential material for the thermoelectric applications. [22][23][24] Electronic properties of MnSi, FeSi, and CoSi are generally well in agreement with the band structure and density-of-state calculations ͑see, for instances, Refs.…”

“…22 It was widely studied as a potential material for the thermoelectric applications. [22][23][24] Electronic properties of MnSi, FeSi, and CoSi are generally well in agreement with the band structure and density-of-state calculations ͑see, for instances, Refs. 25-28͒ though the gap closing in FeSi is not reproduced in the calculations.…”

Environmental-friendly thermoelectric materials

“…It is regarded as potential thermoelectric materials due to its high electrical conductivity (1 m Ω cm) and decent Seebeck coefficient (~80 µ V/K at 300 K). The power factor of CoSi is relatively similar to those observed in the state-of-the-art TE materials such as bismuth tellurite [17,18,134].…”

“…increases the charge carriers by adding different dopants; enhancement of phonon scattering by promoting crystallographic disorder; and nanostructuring [17,18,134,135].…”