Mg 2 Si 1Àx Ge x compounds were prepared from pure elements by melting in tantalum crucibles. The reaction was conducted under an inert gas in a special laboratory setup. Samples for thermoelectric measurements were formed by hot pressing. Structure and phase composition of the obtained materials were investigated by x-ray diffraction (XRD). Morphology and chemical composition were examined by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS), respectively. Thermoelectric properties, i.e., the Seebeck coefficient, the electrical conductivity, and the thermal conductivity, were measured in the temperature range of 500 K to 900 K. The effect of Bi and Ag doping on the thermoelectric performance of Mg-Si-Ge ternary compounds was investigated. The electronic structures of binary compounds were calculated using the Korringa-Kohn-Rostoker (KKR) method. The effects of disorder, including Ge substitution and Bi or Ag doping, were accounted for in the KKR method with coherent potential approximation calculations. The thermoelectric properties of doped Mg 2 Si 1Àx Ge x are discussed with reference to computed density of states as well as the complex energy band structure.

We report a study on a hybrid mode-locked fiber laser with two saturable absorbers: slow and fast, integrated in a single device. Amorphous antimony telluride (Sb(2)Te(3)) layer was deposited on side-polished fiber to form the slow saturable absorber due to the third order nonlinear susceptibility of Sb(2)Te(3). Additionally, an unsymmetrical design of the device causes polarization-dependent losses and together with polarization controller allows to use a nonlinear polarization evolution to form the artificial fast saturable absorber. Sub-200 fs soliton pulses with 0.27 nJ of pulse energy were generated in the hybrid mode-locked Er-doped fiber laser. Differences in the dynamics of mode-locked laser are further investigated with the use of slow and fast saturable absorbers solely, and compared with the hybrid device. Joint operation of two saturable absorbers enhances the laser performance and stability. The conducted experiments allowed to define roles of each mechanism on the pulse shaping in the laser cavity.

For the first time, the high entropy, transition metal-based chalcogenides are synthesized. The materials are characterized by the pentlandite structure, exhibiting promising functional properties with regard to multiple possible applications.

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We present a study on a antimony telluride (Sb 2 Te 3 )-deposited side-polished fiber device as a saturable absorber for Yb-doped modelocked fiber lasers. Thin layers of Sb 2 Te 3 with variable length were deposited by a pulsed magnetron sputtering technique. We demonstrate measured characteristics of the device and show that it can be treated as a hybrid component -tunable polarizer with saturable absorption properties. The polarizing extinction ratio varies from 1.5 dB up to 17.1 dB with increasing length of the deposition. The fiber components were employed in all-normal Yb-doped fiber cavities. All devices enabled for mode-locked operation by means of hybrid mode-locking or nonlinear polarization evolution mechanism. In particular, the laser with 2 mm long Sb 2 Te 3 absorber emitted 5.9 ps pulses with 4 mW of average output power.

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Degradation of CoSb 3 in air was studied at 500, 600 and 700°C. The type and extent of degradation was evaluated on the basis of specimen mass change, scale thickness, visual inspection and systematic analysis of chemical composition, phase composition and microstructure of specimen surfaces, fractures and crosssections. It has been found that at the investigated temperatures, CoSb 3 is neither sufficiently stable nor oxidation-resistant. Antimony and cobalt react readily with oxygen by 500°C. The oxide scales are complex, with the predominant constituents being cobalt-antimony oxides, CoSb 2 O 4 and CoSb 2 O 6 . A tentative reaction mechanism is proposed.

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