In this work, we demonstrate the use of high performance nanostructured PbTe-based materials in high conversion efficiency thermoelectric modules.

X-ray structural analysis and high-temperature thermoelectric properties measurements are performed on polycrystalline samples of artificial mineral Cu12−xNixSb4S13 tetrahedrite. Analysis of the atomic displacement parameter manifests low-energy vibration of Cu(2) out of CuS3 triangle plane. The vibration results in low lattice thermal conductivity of less than 0.5 W K−1 m−1. By tuning of the Ni composition x and decrease of electronic thermal conductivity, dimensionless thermoelectric figure of merit for x = 1.5 achieves 0.7 at 665 K, which is a considerably high value among p-type Pb-free sulfides. Because the tetrahedrite is an environmentally friendly material, it constitutes a good thermoelectric material for use in support of a sustainable society.

Carbon-substituted MgB 2 single crystals, Mg(B 1-x C x ) 2 of 0.3-1.0 mm size were grown for x=0.02-0.15 by a high-pressure technique. The doping dependence of lattice constants studied in a range of x=0.0-0.2 shows a monotonic decrease in a, while the c parameter remains almost invariant. Using X -ray diffraction and Auger electron spectroscopy, the solubility limit of C in MgB 2 was estimated to be about 15±1%, which is substantially larger than that reported for the polycrystalline samples synthesized by encapsulation techniques.Measurements of temperature dependence of magnetization and resistivity showed a dramatic decrease in T c with C -substitution, followed by complete suppression of superconductivity for x>0.125. Resistivity measurements in magnetic fields parallel and perpendicular to the basal plane of the crystals showed a nearly isotropic state in the heavily -doped crystals (x>0.1).

We report the discovery of a family of ternary platinum phosphides APt3P (A = Ca, Sr, and La), which crystallize in an antiperovskite-based structure closely related to that of the heavy fermion superconductor CePt3Si. All three phosphides showed superconductivity at low temperatures and the highest critical temperature T(c) = 8.4  K was observed for SrPt3P. The analysis of specific heat C(T) for SrPt3P shows clear evidence for very strong coupling s-wave superconductivity with a large ratio between superconducting gap Δ0 and T(c), 2Δ0/k(B)T(c) ∼ 5, and the presence of low-energy phonons. The presence of multiple Fermi surface pockets was inferred from the nonlinear magnetic field dependence of Hall resistivity, which we argue might play a role in realizing the strong coupling of charge carriers with the low-lying phonons.

Here we report the growth of sub-millimeter MgB 2 single crystals of various shapes under high pressure in Mg-B-N system. Structure refinement using a singlecrystal X-ray diffraction analysis gives lattice parameters a=3.0851 (5) . It was found that as sintering temperature increased, the sample quality was improved, but for the heat treatment above 950 o C the gold started to melt and to adhere strongly to MgB 2. Preparation of high-density bulk MgB 2 materials at a higher temperature (950-1250 o C) and 3.5 GPa was reported in BN crucibles 7) . However, the samples prepared at 1250 o C apparently showed inhomogeneous structure in macroscopic scale, indicating the occurrence of contamination from the crucible wall. PACSThese results are not quite favorable for crystal growth of MgB 2 under high-pressure.In this letter, we report the successful growth of high-quality MgB 2 single crystals under high pressure in the Mg-B-N system. Using the crystals, we carried out structure refinement and measured anisotropic superconducting properties of magnesium diboride. were used for refinement after absorption correction by a ψ-scan. The structure was refined by the full-matrix least-square procedure.The temperature dependence of the magnetization M(T) was measured by a SQUID (MPMS XL, Quantum Design) for 37 crystals of different shape (total weight 0.25mg) aligned with the c-axis perpendicular to the sample holder. In-plane electrical resistivity was measured for several plate-like crystals of typical size of 500x100x20 µm 3 in a four-probe configuration using a low frequency (17.8Hz) ac technique with a voltage resolution of less than 0.3nV. To study the anisotropic superconducting properties, the resistivity measurements were performed in the magnetic fields up to 7Tesla applied parallel and perpendicular to the Mg and B planes.The Mg-B-N system has been extensively studied during last 40 years [8][9][10] . In this system Mg and Mg-containing compounds act as the catalysts for the 4 transformation of boron nitride (BN) from hexagonal to cubic form under high pressure and the formation of MgB 2 and MgB 6 crystals has been observed 11). These compounds were formed as the intermediate phases in Mg-BN system, during the synthesis of cubic boron nitride, but MgB 2 was decomposed after prolong heat treatment.We found that the lower limit for MgB 2 crystal growth in "pressure- , using polycrystalline and powdered sample, refined structural data were previously unavailable. It has been proved to be very difficult to avoid the formation of impurity phases (MgO and MgB 4 ) in polycrystalline samples and thus the precise structure refinement is almost impossible. In this study well-formed single crystals were chosen for structure analysis to minimize of absorption effects. The refined crystallographic data, atomic coordinates, and thermal parameters are listed in Table 1 .In the final part of this letter we briefly characterize the superconducting properties of our MgB 2 single crystals. .In Fig.5(a) we present the resistive supe...