We have investigated the effect of Sb-deficiency on the thermoelectric figure of merit (zT) of Zn4Sb3 prepared by solid state reaction route. At high temperatures, the Seebeck coefficient (S) and electrical conductivity ({sigma}) increase with increase in Sb deficiency whereas the thermal conductivity (k{appa}) decreases giving rise to an increase in the overall zT value. The observations suggest that creation of vacancies could be an effective route in improving the thermoelectric properties of Zn4Sb3 system. This coupled to nanostructuring strategy could lead to the ultimate maximum value of zT in this system for high temperature thermoelectric applications.
We report a strategy based on introduction of point defects for improving the thermoelectric properties of FeSb2, a promising candidate for low temperature applications. Introduction of Sb deficiency to the tune of 20% leads to enhancement in the values of electrical conductivity ({sigma}) and Seebeck coefficient (S) accompanied with a concomitant suppression in lattice thermal conductivity (k{appa}lat) values in samples prepared using conventional solid state reaction route. These observations in polycrystalline FeSb2-x provides ample motivation for a dedicated exploration of thermoelectric behavior of the corresponding single crystalline as well as hot-pressed polycrystalline counterparts.
Thermoelectric properties of the chemically-doped intermetallic narrow-band semiconductor FeGa3 are reported. The parent compound shows semiconductor-like behavior with a small band gap (Eg = 0.2 eV), a carrier density of ~ 10(18) cm-3 and, a large n-type Seebeck coefficient (S ~ -400 mu V/K) at room temperature. Hall effect measurements indicate that chemical doping significantly increases the carrier density, resulting in a metallic state, while the Seebeck coefficient still remains fairly large (~ -150 mu V/K). The largest power factor (S2/{rho} = 62 mu W/m K2) and corresponding figure of merit (ZT = 0.013) at 390 K were observed for Fe0.99Co0.01(Ga0.997Ge0.003)3.
Thermoelectric properties of graphene nanoribbons with periodic edge vacancies and antidot lattice are investigated. The electron-phonon interaction is taken into account in the framework of the Hubbard-Holstein model with the use of the Lang-Firsov unitary transformation scheme. The electron transmission function, the thermopower and the thermoelectric figure of merit are calculated. We have found that the electron-phonon interaction causes a decrease in the peak values of the thermoelectric figure of merit and the shift of the peak positions closer to the center of the bandgap. The effects are more pronounced for the secondary peaks that appear in the structures with periodic antidot.
Although SbSe2-based layered compounds have been predicted to be high-performance thermoelectric materials and topological materials, most of these compounds obtained experimentally have been insulators so far. Here, we present the effect of Bi substitution on the thermoelectric properties of SbSe2-based layered compounds NdO0.8F0.2Sb1-xBixSe2 (x = 0-0.4). The room temperature electrical resistivity is decreased to 8.0 * 10^-5 ohmm for x = 0.4. The electrical power factor is calculated to be 1.4 * 10^-4 W/mK^2 at 660 K, which is in reasonable agreement with combined Jonker and Ioffe analysis. The room-temperature lattice thermal conductivity of less than 1 W/mK is almost independent of x, in contrast to the point-defect scattering model for conventional alloys. The present work provides an avenue for exploring SbSe2-based insulating and BiSe2-based conducting systems.
We present a study of the electronic properties of Tl5Te3, BiTl9Te6 and SbTl9Te6 compounds by means of density functional theory based calculations. The optimized lattice constants of the compounds are in good agreement with the experimental data. The band gap of BiTl9Te6 and SbTl9Te6 compounds are found to be equal to 0.589 eV and 0.538 eV, respectively and are in agreement with the available experimental data. To compare the thermoelectric properties of the different compounds we calculate their thermopower using Motts law and show, as expected experimentally, that the substituted tellurides have much better thermoelectric properties compared to the pure compound.