Low-temperature resistivity, Seebeck coefficient, thermal conductivity, and heat-capacity measurements were performed on Ba8Ga16Sn30. This compound crystallizes in a cubic type-VIII clathrate phase, space group I¯43m, with the Baatoms residing inside voids created by a tetrahedrally bonded network of Ga andSn atoms. Ba8Ga16Sn30 exhibits semiconducting behavior above 150 K with a low thermal conductivity and thus may hold potential for thermoelectric applications.

Compounds with clathrate-hydrate type crystal lattice structures are currently of interest in thermoelectric materials research. This is due to the fact that semiconducting compounds can be synthesized with varying doping levels while possessing low, even ‘glass-like’, thermal conductivity. Up to now most of the work has focused on type I Si and Ge clathrates. Sn-clathrates however are viewed as having the greatest potential for thermoelectric cooling applications due to the larger mass of Sn and the expected small band-gap, as compared to Si and Ge clathrates. Transport properties on type I Sn-clathrates has only recently been reported [1–3]. In this report we present ongoing experimental research on both type I and II clathrates with an emphasis on the thermal transport of these novel materials. We present thermal conductivity data Si-Ge and Ge-Sn alloys as well as on a type II Ge clathrate for the first time, and compare these data to that of other clathrate compounds.

In order to grow large single crystals of the La2‐xSrxCuOy and Bi2+xSr2‐zCuOy families of high Tc superconductors, we have studied the relationships between nominal Sr composition in the starting materials and the Sr compositions of the resulting products. We present growth, x‐ray, and composition data for these samples.

Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, λ = 13.8Å (disordered structure) and X = 16.6Å (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 × 10−13 sec and 2 × 10−13 sec, respectively.