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PbTe and SnTe in their p-type forms have long been considered high-performance thermoelectrics, and both of them largely rely on two valence bands (the first band at L point and the second one along the Σ line) participating in the transport properties. This work focuses on the thermoelectric transport properties inherent to p-type GeTe, a member of the group IV monotellurides that is relatively less studied. Approximately 50 GeTe samples have been synthesized with different carrier concentrations spanning from 1 to 20 × 10 20 cm − 3 , enabling an insightful understanding of the electronic transport and a full carrier concentration optimization for the thermoelectric performance. When all of these three monotellurides (PbTe, SnTe and GeTe) are fully optimized in their p-type forms, GeTe shows the highest thermoelectric figure of merit (zT up to 1.8). This is due to its superior electronic performance, originating from the highly degenerated Σ band at the band edge in the low-temperature rhombohedral phase and the smallest effective masses for both the L and Σ bands in the high-temperature cubic phase. The high thermoelectric performance of GeTe that is induced by its unique electronic structure not only provides a reference substance for understanding existing research on GeTe but also opens new possibilities for the further improvement of the thermoelectric performance of this material.

ABSTRACT:Panax notoginseng (Sanqi) is a cardiovascular herb containing ginsenosides that are believed to be responsible for the therapeutic effects of Sanqi. The aim of this study was to evaluate rat exposure to ginsenosides after oral administration of Sanqi extract and to identify the key factors affecting their absorption and disposition. Ginsenosides were administered to rats, either in the form of Sanqi extract or as pure chemicals. The ginsenosides Ra 3 , Rb 1 , Rd, Re, Rg 1 , and notoginsenoside R 1 were the major saponins present in the herbal extract. Systemic exposure to ginsenosides Ra 3 , Rb 1 , and Rd after oral administration of the extract was significantly greater than that to the other compounds. Considerable colonic deglycosylation of the ginsenosides occurred, but the plasma levels of deglycosylated metabolites were low in rats. Poor membrane permeability and active biliary excretion are the two primary factors limiting systemic exposure to most ginsenosides and their deglycosylated metabolites. In contrast with other ginsenosides, biliary excretion of ginsenosides Ra 3 and Rb 1 was passive. Meanwhile, the active biliary excretion of ginsenoside Rd was significantly slower than that of other saponins. Slow biliary excretion, inefficient metabolism, and slow renal excretion resulted in long-circulating and thus relatively high exposure levels for these three ginsenosides. For these reasons, plasma ginsenosides Ra 3 , Rb 1 , and Rd were identified as pharmacokinetic markers for indicating rat systemic exposure to Sanqi extract. This is a systematic investigation of the absorption and disposition of ginsenosides from an herb, the information gained from which is important for linking Sanqi administration to its medicinal effects.

In Te-free (Bi,Sb)2Se3, structural transition induced electronic band convergence and intensified phonon scattering triple the thermoelectric ZT to 1.0.