Post-Variscan vein-type Co-Ni-Bi ores of the Bieber deposit, Spessart mountains, Germany, which are related to the Permian Kupferschiefer, have been investigated by ore microscopy, X-ray powder diffraction and electron-probe microanalysis. The samples contain a variety of ore minerals, notably skutterudite, native bismuth, cobaltite, alloclasite, niccolite, maucherite, gersdorffite, rammelsbergite/pararammelsbergite, safflorite, loellingite and emplectite. The ores display structures indicative of multiple brecciation and complex zoned arsenide assemblages. Three sequential stages of deposition are identified, which are (1) the Cu stage, (2) the main Co-Ni-Bi stage, and (3) the late stage. The arsenide minerals, notably skutterudite, diarsenides and sulpharsenides, show a large range of compositional variation in Co-Ni-Fe space. A relatively limited number of skutterudite and diarsenide compositions lie outside the compositional fields established in the literature. Skutterudite and diarsenides are characterized by a significant substitution of As by S up to 0.44 a.p.f.u. and 0.31 a.p.f.u., respectively, which is larger than the range previously reported for these minerals. Sulpharsenide compositions can be grouped into three populations, which conform to cobaltian arsenopyrite, cobaltite and gersdorffite. They display highly variable As/S ratios between 0.95:1.00 and 1.29:0.73, consistent with experimental data. Estimates of the formation temperatures, based on the presence of dendritic native bismuth and emplectite, are in the range 100–300°C, similar to different post-Variscan mineralization styles widespread in Central Europe. Comparison of the Co-Ni-Bi vein assemblage with the framework of available paragenetic information and radiometric age data for regional mineralization events indicates an age of mineralization of ~150–160 Ma for the Bieber deposit.

N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubic symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. This knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.

Nanostructuring is one of the effective approaches to lower the thermal conductivity of thermoelectric materials for improving its figure of merit. The nano-sized uniform skutterudite Co1−xNixSb3 (x = 0, 0.05, 0.075, 0.125, 0.15, and 0.25) thermoelectric powders were synthesized in triethylene glycol solution by using CoCl2, NiCl2, and SbCl3 as precursors and NaBH4 as the reductant. Different synthesis conditions were studied to pursue pure and uniform skutterudite CoSb3 powders. The powders were characterized by X-ray diffraction, field emission scanning electron microscope, and energy-dispersive X-ray analysis. Experimental results show that a Ni-doped skutterudite Co1−xNixSb3 single phase was obtained at 290 °C for 12 h. The powders are spherical, small, and uniform. As x increases from 0 to 0.25, the unit-cell parameter a increases from 0.9044 to 0.9065 nm and the particle size increases from 10 to 30 nm.

The RuSb2Te compound has been synthesized and structurally characterized from powder X-ray diffraction data. RuSb2Te has the skutterudite structure, Im3 symmetry, unit-cell parameter a = 9.2665(1) Å, V = 795.70(1) Å3, Z = 8, and Dc = 7.88 g/cm3. The Sb and Te atoms randomly occupy the crystallographic 24g position; no indications of ordering of Te and Sb atoms have been detected.

Crystal structure of the skutterudite-related phase has been refined by the Rietveld method from X-ray powder diffraction data. Refined crystallographic data for CoSn1.5Te1.5 are a=12.9063(2) Å, c=15.7837(3) Å, V=2276.89(4) Å3, space group R3 (No. 148), Z=24, and Dx=7.50 g/cm3. The crystal structure of the title compound can be viewed as a modification of the skutterudite structure (CoAs3)—it is isostructural with CoGe1.5Te1.5 and IrSn1.5Te1.5. In the structure of CoSn1.5Te1.5, the Sn and Te atoms exhibit long-range ordering, which results in lowering of the original cubic symmetry of the skutterudite structure to the trigonal one.

The crystal structure of skutterudite-related phase IrGe1.5Se1.5 has been refined by the Rietveld method from laboratory X-ray powder diffraction data. Refined crystallographic data for IrGe1.5Se1.5 are a=12.0890(2) Å, c=14.8796(3) Å, V=1883.23(6) Å3, space group R3 (No. 148), Z=24, and Dc=8.87 g/cm3. Its crystal structure can be derived from the ideal skutterudite structure (CoAs3), where Se and Ge atoms are ordered in layers perpendicular to the [111] direction of the original skutterudite cell. Weak distortions of the anion and cation sublattices were also observed.