We report on the synthesis of Sb 2 Te 3 nanoparticles with record-high figure of merit values of up to 1.5. The central thermoelectric parameters, electrical conductivity, thermal conductivity and Seebeck coefficient, were independently optimized. The critical influence of porosity for the fabrication of highly efficient thermoelectric materials is firstly demonstrated, giving a strong guidance for the optimization of other thermoelectric materials.Thermoelectric materials directly convert heat fluxes into useable electricity and are therefore discussed as a key-enabler in waste heat recovery. For this vision, the main challenge is to develop thermoelectric materials with sufficiently high conversion efficiencies, expressed by the material's figure of merit zT = a 2 sT/k, where a, s, k and T are Seebeck coefficient, electrical conductivity, thermal conductivity, and temperature, respectively. a 2 s is called power factor. It is assumed that zT D 1.5 is necessary for most technical applications. 1 Nanostructuring of thermoelectric materials has been demonstrated experimentally and theoretically to greatly improve the figure of merit by reducing the lattice contribution to the thermal conductivity. 2,3 Different types of scattering centers for the heat carrying phonons were implemented as design concepts for thermoelectric materials, such as nanoscale precipitates or interfaces. 4,5 To effectively scatter the broad spectrum of phonon wavelengths, a hierarchical design of the nano-and microstructure was developed which led to record-high zT values. 6 On the other hand, an increase of disorder in the nano-and microstructure of a crystal simultaneously increases the charge carrier scattering, which limits the nano-and microstructuring approach since the charge carrier mobility gets affected adversely. A high electrical conductivity further requires a high charge carrier concentration. The latter compromises the Seebeck coefficient which is best when the charge carrier concentration is low. Thus, to optimize a thermoelectric material, a careful decoupling of the competing and interrelated thermoelectric transport coefficients is mandatory.We herein report on a strategy that allows to individually address and optimize each of the three thermoelectric transport coefficients in the nanobulk fabrication process as demonstrated for a standard thermoelectric material, Sb 2 Te 3 . Synergistic effects result in a dramatic enhancement of zT up to 1.5 around 300 1C. This specific versatile approach opens up a new synthetic strategy to a general route to highly efficient thermoelectric materials.Control of the charge carrier concentration is the first important aspect in optimizing the performance of a thermoelectric material. Metal chalcogenides such as Sb 2 Te 3 have a phase width (are not line compounds) and are intrinsically doped by anti-site defects. As a consequence, the Seebeck coefficient of Sb 2 Te 3 obtained by traditional synthetic approaches tends to be lower than required for thermoelectric application. Thus, the an...

A systematic study on the microwave-assisted thermolysis of the single source precursor (EtSb)Te (1) in different asymmetric 1-alkyl-3-methylimidazolium- and symmetric 1,3-dialkylimidazolium-based ionic liquids (ILs) reveals the distinctive role of both the anion and the cation in tuning the morphology and microstructure of the resulting SbTe nanoparticles as evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). A comparison of the electrical and thermal conductivities as well as the Seebeck coefficient of the SbTe nanoparticles obtained from different ILs reveals the strong influence of the specific IL, from which CmimI was identified as the best solvent, on the thermoelectric properties of as-prepared nanosized SbTe. This work provides design guidelines for ILs, which allow the synthesis of nanostructured thermoelectrics with improved performances.

Reactions of homoleptic isonitrile ligated complexes or clusters of d(10)-metals with the potent carbenoid donor ligand GaCp* are presented (Cp* = pentamethylcyclopentadienyl). Treatment of [Ni4(CNt-Bu)7], [{M(CNR)2}3] (M = Pd, Pt) and [Pd(CNR)2Me2] (R = t-Bu, Ph) with suitable amounts of GaCp* lead to the formation of the heteroleptic, tri- and tetranuclear clusters [Ni4(CNt-Bu)7(GaCp*)3] (1), [{M(CNt-Bu)}3(GaCp*)4] (M = Pd: 2a, Pt: 2b), and [{Pd(CNR)}4(GaCp*)4] (R = t-Bu: 3a, Ph: 3b). The reactions involve isonitrile substitution reactions, GaCp* addition reactions, and cluster formation reactions. The new compounds were investigated for their ability to undergo Ga/Zn exchange reactions when treated with ZnMe2. The novel tetranuclear Zn-rich clusters [Ni4GaZn7(Cp*)2Me7(CNt-Bu)6] (4) and [{Pd(CNR)}4(ZnCp*)4(ZnMe)4] (R = t-Bu: 5a, Ph: 5b) were obtained and isolated. The electronic situation and geometrical arrangement of atoms of all compounds will be presented and discussed. All new compounds are characterized by solution (1)H, (13)C NMR and IR spectroscopy, elemental analysis (EA), liquid injection field desorption ionization mass spectrometry (LIFDI-MS) as well as single crystal X-ray crystallography.

Treatment of [Mo(N(2))(PMe(3))(5)] with two equivalents GaCp* (Cp* = η(5)-C(5)(CH(3))(5)) leads to the formation of cis-[Mo(GaCp*)(2)(PMe(3))(4)] (1), while AlCp* did not react with this precursor. In addition, [Ni(GaCp*)(2)(PPh(3))(2)] (2a), [Ni(AlCp*)(2)(PPh(3))(2)] (2b), [Ni(GaCp*)(2)(PCy(3))(2)] (3a), [Ni(GaCp*)(2)(PMe(3))(2)] (3b), [Ni(GaCp*)(3)(PCy(3))] (4) and [Ni(GaCp*)(PMe(3))(3)] (5) have been prepared in high yields by a direct synthesis from [Ni(COD)(2)] and stoichiometric amounts of the ligands PR(3) and ECp* (E = Al, Ga), respectively. All compounds have been fully characterized by (1)H, (13)C, and (31)P NMR spectroscopy, elemental analysis and single crystal X-ray diffraction studies.