Promising Thermoelectric Performance Research Articles

Phase stability, crystal structure and thermoelectric properties of Cu doped AgSbTe2

CuxAg1-xSbTe2 samples withx = 00.3 are prepared by a combined process of melt-quenching and spark plasma sintering (SPS). X-ray powder diffraction (XRD) analysis indicates that single phase samples with the NaCl-type structure are obtained for the Cu-doped samples before SPS treatment, whereas a small quantity of Ag2Te impurities coexist with the main cubic phase for the sample without Cu. According to our thermoanalysis and XRD results, the substitution of Cu for Ag can effectively prevent the precipitation of Ag2Te, but this also leads to the presence of a minor amorphous phase in the melt-quenched sample. The amorphous phase crystallizes into Sb7Te metastable phase at about 540 K, which finally transforms into the stable Sb2Te3 compound. After the SPS treatment of the melt-quenched sample, the sample withx=0.1 remains a single phase with the face-centered-cubic crystal structure, while Sb7Te and Sb2Te3 are precipitated as the second phases for the samples withx = 0.2 and 0.3, respectively. The electrical conductivity increases and the Seebeck coefficient decreases with the addition of Cu due to the existence of the second phase in the samples withx = 0.2 and 0.3. Accordingly, thermal conductivities also increase with the addition of Cu, leading to the reduced thermoelectric performance of thex= 0.2 and 0.3 samples. For the sample withx = 0.1, its power factor is comparable to that of the literature reported AgSbTe2 compound. As a result of so-called alloying effect, the phonon scattering effect is enhanced due to the partial replacement of Ag by Cu, leading to the reduced thermal conductivity of thex = 0.1 sample. Therefore, the Cu0.1Ag0.9SbTe2 sample exhibits the promising thermoelectric performance and a dimensionless thermoelectric figure of merit (ZT) value of 1 is achieved at 620 K.

Assessment of thermoelectric performance of Cu2ZnSnX4, X=S, Se, and Te

A recent experiment on In-doped Cu2ZnSnSe4 [X. Y. Shi et al., Appl. Phys. Lett. 94, 122103 (2009)] has shown promising thermoelectric performance characteristics. In this letter, we analyze relevant electronic and transport properties of Cu2ZnSnSe4 and similar compounds, Cu2ZnSnS4 and Cu2ZnSnTe4, to assess their potential as thermoelectric materials. Using density functional theory and Boltzmann transport equations, we determine Seebeck coefficients, conductivities, and power factors of closely related polymorphs with space groups, I4¯, I4¯2m, and P4¯2m for each compound. Based on their electronic structure and transport properties, we conclude that other two compounds could have similar potential as thermoelectric materials.

Thermal Stability and Phase Purity in Polycrystalline Ba8Ga x Ge46−x

Polycrystalline Ba 8 Ga x Ge 46-x exhibits promising thermoelectric performance with the figure of merit ZT close to that of single crystals. Polycrystalline Ba 8 Ga x Ge 46-x is promising for applications, but reproducibility and thermal stability of thermoelectric properties need to be demonstrated. Polycrystalline samples of Ba 8+d Ga x Ge 46-x -type clathrates (15.0 ≤ x ≤ 16.8 with varied nominal Ga content and d = 0 or 0.2) were prepared by direct reaction of the elements, followed by ball milling and hot pressing. Trace Ge impurity was observed (< 1.0 wt.%) depending on the synthesis method. The electrical resistivity was stable in measurements up to 1000 K, regardless of Ge impurity. However, measurements to 1050 K resulted in irreversible increase in carrier concentration while the carrier mobility remained unchanged.

Synthesis and Transport Properties of Polycrystalline Co-Filled Type-I Clathrate Compound (Sr,Ba)&lt;sub&gt;8&lt;/sub&gt;Ga&lt;sub&gt;16&lt;/sub&gt;Ge&lt;sub&gt;30&lt;/sub&gt;

Ga-substituted Ge based type-I clathrates with the general formula A8X16Y30 display promising thermoelectric performance. Using high purity elemental Sr, Ba, Ga, and Ge as starting materials, polycrystalline co-filled type-I clathrate compound (Sr,Ba)8Ga16Ge30 were successfully achieved by combining melting and Spark Plasma Sinter (SPS) method. The temperature dependence of thermal conductivity, electronic conductivity and Seebeck coefficient were reported. The calculated ZTmax is 0.28 at 700K. Enhanced thermoelectric performance would be expected through adjusting Sr/Ba ratio and framework atoms.

Sm-substitution effects on structural and transport properties of PbSe

Polycrystalline single phase of Pb 1− x Sm x Se ( x = 0.00–0.09) samples were prepared by the solid state reaction. XRD and SEM/EDAX methods were used for structural and chemical characterization of the obtained materials. The investigated samples were also characterized by the measurements of the samarium concentration dependence of the electrical conductivity and Seebeck coefficient. The power factor shows that these materials have the potential for high temperature applications with promising thermoelectric performance.

Thermoelectric Properties of K2Bi8Se13−xSx Solid Solutions

AbstractDerivatives of β-K2Bi8Se13 are an interesting series of materials for thermoelectric investigations due to their very low thermal conductivity and highly anisotropic electrical properties. Up to now substitutions on the Bi and alkali metal sites have been studied in order to tune the thermoelectric properties. In this work, the thermoelectric properties of the sulfur-substituted K2Bi8Se13−xSx (0&lt;x&lt;13) are presented with respect to Seebeck coefficient, the electrical and thermal conductivity as a function of temperature. Seebeck coefficient measurements showed the n-type character of all members while electrical conductivity shows higher values compare to the other solid solution series of the same type. The lattice thermal conductivity is affected due to the Se/S disorder. The temperature dependence of the figure-of-merit ZT shows that these materials have potential for high temperatures applications with promising thermoelectric performance.