Synthesis and structural characterization of a turbostratically disordered polymorph of (PbSe)1.18(TiSe2)2 is reported. The structure of this compound consists of an intergrowth between one distorted rock salt structured PbSe bilayer and two transition metal dichalcogenide structured Se–Ti–Se trilayers. In addition to the lattice mismatch, there is extensive rotational disorder between these constituents. The electrical resistivity of (PbSe)1.18(TiSe2)2 is a factor of 9 lower at room temperature, and the Seebeck coefficient is almost double that reported for the crystalline misfit layered compound analogue.

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A modification of the modulated elemental reactants synthetic technique was developed and used to synthesize eleven members of the [(SnSe) 1.15 ] m (TaSe 2 ) n family of compounds, with m and n equal to integer values between 1 and 6. Each of the intergrowth compounds contained highly oriented intergrowths of SnSe bilayers and TaSe 2 monolayers with abrupt interfaces perpendicular to the c-axis. The c-lattice parameter increased 0.579(1) nm per SnSe bilayer and 0.649(1) nm per Se−Ta−Se trilayer (TaSe 2 ) as m and n were varied. ab-plane X-ray diffraction patterns and transmission electron microscope images revealed a square in-plane structure of the SnSe constituent, a hexagonal in-plane structure for the TaSe 2 constituent, and rotational disorder between the constituent layers. Temperature dependent electrical resistivity, measured on several specimens, revealed metallic behavior, and a simple model is presented to explain the differences in resistivity as a function of m and n.

International audienceA semi-automatic technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is described. It is based primarily on the projected reciprocal lattice geometry, but also utilizes the intensity of reflections that are extracted from precession-enhanced electron diffraction spot patterns of polycrystalline materials and multi-material composites. At the core of the method, experimental (precession-enhanced) electron diffraction spot patterns are cross correlated with pre-calculated templates for a set of model structures. The required hardware facilitates a scanning-precession movement of the primary electron beam on the polycrystalline and/or multi-material sample and can be interfaced to any newer or older mid-voltage TEM. The software that goes with this hardware is so flexible in its intake of experimental data that it can also create crystallite orientation and phase maps of nanocrystals from the amplitude part of Fourier transforms of high resolution TEM images. Experimentally obtained crystallite orientation and phase maps are shown for a clausthalite nanocrystal powder sample, polycrystalline aluminum and copper films, fine-grained palladium films, as well as MnAs crystallites that are partly embedded in a GaAs wafer. Comprehensive open-access and commercial crystallographic databases that may provide reference data in support of the nanocrystal phase identification process of the software are briefly mentioned. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei