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The best p-type skutterudites so far are didymium filled, Fe/Co substituted, Sb-based skutterudites. Substitution at the Sb-sites influences the electronic structure, deforms the Sb 4 -rings, enhances the scattering of phonons on electrons and impurities and this way reduces the lattice thermal conductivity.In this paper we study structural and transport properties of p-type skutterudites with the nominal composition DD 0.7 Fe 2.7 Co 1.3 Sb 11.7 {Ge/Sn} 0.3 , which were prepared by a rather fast reaction-annealing-melting technique. The Ge-doped sample showed impurities, which did not anneal out completely and even with ZT > 1 the result was

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Quaternary chalcogenide compounds Cu2+xZnSn1−xSe4 (0 ≤ x ≤ 0.15) were prepared by solid state synthesis. Rietveld powder X-ray diffraction (XRD) refinements combined with Electron Probe Micro Analyses (EPMA, WDS-Wavelength Dispersive Spectroscopy) and Raman spectra of all samples confirmed the stannite structure (Cu2FeSnS4-type) as the main phase. In addition to the main phase, small amounts of secondary phases like ZnSe, CuSe and SnSe were observed. Transport properties of all samples were measured as a function of temperature in the range from 300 K to 720 K. The electrical resistivity of all samples decreases with an increase in Cu content except for Cu2.1ZnSn0.9Se4, most likely due to a higher content of the ZnSe. All samples showed positive Seebeck coefficients indicating that holes are the majority charge carriers. The thermal conductivity of doped samples was high compared to Cu2ZnSnSe4 and this may be due to the larger electronic contribution and the presence of the ZnSe phase in the doped samples. The maximum zT = 0.3 at 720 K occurs for Cu2.05ZnSn0.95Se4 for which a high-pressure torsion treatment resulted in an enhancement of zT by 30% at 625 K.