TiNiSn, ZrNiSn and HfNiSn are members of a large group of intermetallic compounds which crystallize in the cubic MgAgAs-type structure. Polycrystalline samples of these compounds have been prepared and investigated for their thermoelectric properties. With thermopowers of about –200 μV/K and resistivities of a few mΩcm, power factors S2/ρ as high as 38 μW/K2 cm were obtained at 700 K. These remarkably high power factors are, however, accompanied by a thermal conductivity which is too high for applications. In order to reduce the parasitic lattice thermal conductivity, solid solutions Zrl−xHfxNiSn, Zrl−xTixNiSn, and Hfl−xTixNiSn were formed. The figure of merit of Zr0.5Hf0.5NiSn at 700 K (ZT = 0.41) exceeds the end members ZrNiSn (ZT = 0.26) and HfNiSn (ZT = 0.22).

The rare-earth compounds R3Cu3Sb4 (R=La, Ce, Gd, Er) were synthesized in order to evaluate their potential for thermoelectric applications. Melting in closed tantalum tubes was used to get the materials without loss of volatile Sb components. The structure and the thermal expansion coefficients of these compounds were determined by temperature-dependent x-ray diffraction measurements. We also determined the effective magnetic moments of the rare-earth ions and their valence state. The resistivity of the compounds was measured over a large temperature range from 2 to 470 K. Hall-effect measurements were performed in the range from 30 to 470 K. Additionally, the thermopower and the thermal conductivity were determined. On the basis of the measured data, an estimation of the thermoelectric potential of this group of materials will be given.