Four efficient n-type dopants have been found for ZrNiSn-based thermoelectric materials. These are Nb or Ta at the zirconium sites, and Sb or Bi at the tin sites. No suitable dopant was found for the nickel sites. In a alloy, a power factor of and a thermal conductivity of were measured at 300 K, resulting in a dimensionless figure of merit ZT = 0.12. These values are increased to and at 700 K.

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Using x-ray scattering we have measured the response of the incommensurate charge-density wave (CDW) modulation in the quasi-low-dimensional material 2H-NbSe2 to applied magnetic fields at low temperatures. The application of a magnetic field, either perpendicular or parallel to the layers of a single crystal of 2H-NbSe2, caused no significant change to either the correlation length or the intensity of the CDW satellites for magnetic fields up to 10 T. These results suggest that the enhancement of the resistance observed in low-dimensional CDW materials exposed to the applied magnetic field does not result from an appreciable conversion of carriers from the normal state to the CDW state. In addition 2H-NbSe2 is a superconductor at low temperatures (Tc = 7.2 K), whilst still within the incommensurate CDW state. This material therefore affords an opportunity to study any interaction between the CDW and superconducting condensates. High magnetic fields can suppress the superconducting state yet no change in the incommensurate CDW satellite correlation length or intensity was observed at high applied magnetic fields. These results conflict with spectroscopic measurements, which suggest a coupling between the superconducting gap excitations and the CDW.

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).

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