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Lead chalcogenide materials have drawn attention in recent years because of their outstanding thermoelectric properties. Bulk n-type materials of AgPbmSbTe2+m have been reported to exhibit high figure of merit, ZT, as high as 1.7 at 700 K. Recent reports have shown p-type lead selenide-based compounds with comparable ZT. The analogous material AgPbmSbSe17 shares a similar cubic rock-salt structure with PbTe-based compounds; however, it exhibits a higher melting point, and selenium is more abundant than tellurium. Using solid solution chemistry, we have fabricated cast AgPb15SbSe17 samples that show a peak power factor of approximately 17 μW/cm K2 at 450 K. Increasing the strength of such materials is commonly achieved through powder processing, which also helps to homogenize the source materials. Pulsed electric current sintering (PECS) is a hot-pressing technique that utilizes electric current through the die and sample for direct Joule heating during pressing. The mechanisms present during PECS processing have captured significant research interest and have led to some notable improvements in sample properties compared with other densification techniques. We report the thermoelectric properties of PECS samples of AgPbmSbSe17 along with sample fabrication and processing details.

The title compounds were synthesized from the elements by heating the corresponding stoichiometric mixtures at high temperature. Their structures were determined from single-crystal X-ray diffraction. Na2Ba4Ga2Sb6 (Pnma, Z = 8, a = 12.3468(10) Å, b = 10.6621(10) Å, c = 13.8344(10) Å) contains chains of ∞[Ga2Sb6]10–. The repeating unit is made of an edge-sharing Ga-centered tetrahedron GaSb2(μ-Sb)2 and another Ga-centered tetrahedron but with additional antimony that is exo-bonded to one of the corners forming Sb–Sb dumbells, i.e. GaSb(Sb–Sb)(μ-Sb)2. The unit connects to neighboring units via sharing two corners of the tetrahedra, i.e. [Ga2Sb5Sb2/2]. Li13Ba8GaSb12 (C2/m, Z = 2, a = 18.0650(10) Å, b = 4.9407(10) Å, c = 13.0123(10) Å, β = 126.728(10)°) contains three different types of anions: single-atom anions of Sb3–, dumbells of Sb4–, and isolated Ga-centered tetrahedra of GaSb4 9–. The two compounds are electronically balanced, and this is confirmed by four-probe conductivity and magnetic measurements. Their very narrow band gaps, 0.014 and 0.049 eV for Na2Ba4Ga2Sb6 and Li13Ba8GaSb12, respectively, make them potential thermoelectric materials.

The title compound, C21H24N2O3, crystallizes as a racemic mixture of R,R and S,S enanti­omers. The three-dimensional packing is stabilized by a system of hydrogen bonds and weak C—H⋯O inter­actions.

In the title compound, C23H16O4S, the dibenzo[c,h]chromene ring system is almost planar. The trans-substituted thio­phenyl and methoxy­carbonyl groups are in an anti­periplanar conformation. The mol­ecules are linked into dimers through weak inter­molecular C—H⋯O hydrogen bonds [H⋯O = 2.53 A]. The mol­ecule has a thienyl-ring flip disorder.

We report a systematic study of the thermoelectric properties of PbSe doped with Ga, In, and excess Pb as a function of carrier density and temperature. All metal dopants efficiently generate electron carriers in the crystal lattice with densities as high as ∼1020 cm−3 measured by the Hall effect. The Seebeck coefficient as a function of carrier density at room temperature was found to be similar for all dopants, while at 700 K substantial differences were observed with PbSe-In exhibiting a larger response. Infrared spectral reflectivity measurements at room temperature showed that both Ga and In substitution in PbSe weakens the curvature of the dispersion relation of the conduction band compared to Pb. This electronic effect contributes a larger density of states in transport processes at high temperatures. We have obtained thermoelectric figures of merit of ∼0.9 at 900 K, exceeding that of PbTe for T > 800 K.

The effect of K and K-Na substitution for Pb atoms in the rock salt lattice of PbTe was investigated to test a hypothesis for development of resonant states in the valence band that may enhance the thermoelectric power. We combined high temperature Hall-effect, electrical conductivity and thermal conductivity measurements to show that K-Na co-doping do not form resonance states but2 can control the energy difference of the maxima of the two primary valence sub-bands in PbTe. This leads to an enhanced interband interaction with rising temperature and a significant rise in the thermoelectric figure of merit of p-type PbTe. The experimental data can be explained by a combination of a single and two-band model for the valence band of PbTe depending on hole density that varies in the range of 1-15 x 10^19 cm^-3., Comment: 8 figures

We report the synthesis, structure, spectroscopic properties, charge and thermal transport, and electronic structure of a new member of the Zintl family, Yb(5)Al(2)Sb(6). The compound crystallizes in the Ba(5)Al(2)Bi(6) structure type and requires the addition of Ge or Si in the synthesis, which appears to act as a catalyst. Yb(5)Al(2)Sb(6) has an anisotropic structure with infinite anionic double chains cross-linked by Yb(2+) ions. Polycrystalline ingots of Yb(5)Al(2)Sb(6) prepared in the presence of 0.5 mol equiv of Ge showed room-temperature conductivity, thermopower, and thermal conductivity of approximately 1100 S/cm, approximately 20 microV/K, and approximately 3.8 W/m.K, respectively. Investigations of other solid solutions of Yb(5)Al(2)Sb(6), doping effects, and chemical modifications are discussed. Sr only partially replaces Yb in the structure leading to Sr(0.85)Yb(4.15)Al(2)Sb(6). Electronic structure calculations performed using a highly precise full-potential linearized augmented plane wave method within the density functional theory scheme show the presence of a negative band gap and suggest incomplete electron transfer and a metallic character to the compound.

The iron arsenide CaFe(4)As(3) features a three-dimensional network derived from intergrown Fe(2)As(2) layers and Ca ions in channels. Complex magnetic interactions between Fe atoms give rise to unexpected transitions and novel direction-dependent magnetic behavior.