With the retreating sources of carbon based fuels, thermoelectric materials can play an important role in the future of environmentally friendly power generators. Sb based framework have in some cases shown some promising properties as thermoelectric materials. The physical properties may be modified with doping or incorporation of new elements. Zn4Sb3 and Cd4Sb3 are structurally related with a Sb-based network and Zn/Cd occupying the rest of the positions. Both structures undergo order-disorder α–β transition of the Zn/Cd positions, at 254 K and ~355 K respectively. The previously ordered interstitial atoms become distributed in the structure and the two high temperature phases are isostructural (R-3c). Cd4Sb3 was synthesized from melt-quench, flux synthesis with Sn, Bi and In. The syntheses made with In resulted in interstitial-free β-Cd4Sb3 with the composition Cd11.7In1.5Sb10. This compound exhibits no phase transitions until decomposition. ZnSnSb2 and InSb both exhibit the cubic sphalerite structure. ZnSnSb2 is metallic and InSb narrow band-gap semiconductor. Attempts were made to fine-tune the electrical properties by probing the mutual solid solubility range. The formula [ZnSnSb2]x[2(InSb)]1-xSn4 and 0<X<1 with 0.1 increments for the whole composition range was used. Resistivity changes from semiconducting to metallic conduction between x=0.9 and x=0.8. In the attempt to dope Zn4Sb3 by In a novel metastable compound with the composition Zn9Sb6In2 was found. Another novel phase was discovered with the composition Zn5Sb4In2-δ (δ=0.15).  The two phases have the same Sb-framework with a CuAl2 structure. Zn and In arrangements fill the square antiprisms formed by the stacking of 32434 nets in anti configuration. The filling of the antiprisms in the two phases are different, in Zn9Sb6In2 the antiprisms have two filling arrangements, an In or Zn3 triangles. In Zn5Sb4In2-δ the antiprisms are filled with an In and a Zn that occupies a split position to form a hetero-atomic dimers.

abstract: The challenging search for clean, reliable and environmentally friendly energy sources has fueled increased research in thermoelectric materials, which are capable of recovering waste heat. Among the state-of-the-art thermoelectric materials β-Zn4Sb3 is outstanding because of its ultra-low glass-like thermal conductivity. Attempts to explore ternary phases in the Zn-Sb-In system resulted in the discovery of the new intermetallic compounds, stable Zn5Sb4In2-δ (δ=0.15) and metastable Zn9Sb6In2. Millimeter-sized crystals were grown from molten metal fluxes, where indium metal was employed as a reactive flux medium.Zn5Sb4In2-δ and Zn9Sb6In2 crystallize in new structure types featuring complex framework and the presence of structural disorder (defects and split atomic positions). The structure and phase relations between ternary Zn5Sb4In2-δ, Zn9Sb6In2 and binary Zn4Sb3 are discussed. To establish and understand structure-property relationships, thermoelectric properties measurements were carried out. The measurements suggested that Zn5Sb4In2-δ and Zn9Sb6In2 are narrow band gap semiconductors, similar to β-Zn4Sb3. Also, the peculiar low thermal conductivity of Zn4Sb3 (1 W/mK) is preserved. In the investigated temperature range 10 to 350 K Zn5Sb4In2-δ displays higher thermoelectric figure of merits than Zn4Sb3, indicating a potential significance in thermoelectric applications. Finally, the glass-like thermal conductivities of binary and ternary antimonides with complex structures are compared and the mechanism behind their low thermal conductivities is briefly discussed. / Dissertation/Thesis / Ph.D. Chemistry 2011