Matthew K. Beekman

Inorganic clathrate-II materials of group 14: synthetic routes and physical properties

Crystalline open-framework and nanoporous materials have long attracted the attention of chemists, physicists, and materials scientists. The intriguing structures such materials exhibit are often intimately related to the unique physical properties they possess. This article reviews recent developments in the preparation and characterization of one such class of inorganic materials, those comprised of group 14 elements crystallizing with the clathrate-II crystal structure. These materials correspond to expanded forms and, in some cases, metastable allotropes of Si, Ge, and Sn. Just as interesting as the structure and properties that group 14 clathrate-II materials display is the diverse range of synthetic techniques used to prepare them and these techniques are discussed. We review the work to date characterizing the physical properties of group 14 clathrate-II materials with emphasis placed on structure–property relationships, in particular with regard to the electronic and transport properties.

In-plane thermal and thermoelectric properties of misfit-layered [(PbSe)0.99]x(WSe2)x superlattice thin films

The in-plane thermal conductivity is measured to be three times lower in misfit-layered [(PbSe)0.99]x(WSe2)x superlattice thin films than disordered-layered WSe2 because of interface scattering despite a higher cross-plane value in the former than the latter. While having little effect on the in-plane thermal conductivity, annealing the p-type [(PbSe)0.99]2(WSe2)2 films in Se increases the in-plane Seebeck coefficient and electrical conductivity because of decreased defect and hole concentrations. Increasing interface density of the annealed films by decreasing x from 4 to 2 has weak influence on the in-plane thermal conductivity but increases the Seebeck coefficient and decreases the room-temperature electrical conductivity.

New Layered Intergrowths in the Sn-Mo-Se System

Several new metastable layered intergrowths based on tin monoselenide and molybdenum diselenide, [(SnSe)1+δ]m[MoSe2]n, have been prepared by self-assembly from elemental nanolaminate precursors deposited by physical vapor deposition. The thin-film specimens were characterized by laboratory x-ray reflectivity and diffraction, synchrotron x-ray diffraction, electron probe microanalysis, and scanning transmission electron microscopy techniques, all of which indicate the formation of intergrowths with precise layering and well-defined composition. Analysis of in-plane diffraction originating from the individual components yields a structural misfit of δxa0=xa00.06 and suggests turbostratic misorientation of the individual layers. In contrast to most known [(MX)1+δ]m[TX2]n-type chalcogenide compounds, electrical transport data for the [(SnSe)1+δ]1[MoSe2]1 composition are consistent with semiconducting behavior.

Magnetic and Electronic Properties of Eu 4 Sr 4 Ga 16 Ge 30

Magnetization, static and ac magnetic susceptibility, nuclear forward scattering, and electrical resistivity measurements have been performed on polycrystalline

Synthesis and thermal conductivity of type II silicon clathrates

{mathrm{Eu}}_{4}{mathrm{Sr}}_{4}{mathrm{Ga}}_{16}{mathrm{Ge}}_{30}

Synthesis and single-crystal X-ray diffraction studies of new framework substituted type II clathrates, Cs8Na16AgxGe136−x (x<7)

, a type I clathrate that has divalent strontium and europium ions encapsulated within a

Electron structure and temperature-dependent shifts in 133 Cs NMR spectra of the Cs 8 Ge 136 clathrate

mathrm{Ga}text{ensuremath{-}}mathrm{Ge}

NMR Study of Slow Atomic Motion in Sr8Ga16Ge30 Clathrate

framework. These data are compared with those of type I clathrates

Characterization of Delafossite-Type CuCoO 2 Prepared by Ion Exchange.

{mathrm{Eu}}_{8}{mathrm{Ga}}_{16}{mathrm{Ge}}_{30}

Synthesis and thermoelectric properties of antifluorite materials

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