6161619531
Structure and Thermoelectric Properties of the Vapor-Phase Condensation LAST Rostyslay Jaworski. Jaroslay Jaworski, Volodymyr Makoyyshyn
Vasyl Stefanyk Precarpathian National University, lvano-Frankivsk, Ukrainę
Lead Telluride - efficient thermoelectric materials for medium temperaturę rangę (500-850) K. The high interest for it research, which has not diminished over the years, due to a unique physical and Chemical properties, and relatively simple technology for high-quality crystals.
In 2004 was reported about high-performance thermoelectric materials with generał Chemical formula Pi8Ag2-xSbxTe2o- This materiał was named LAST. This compounds have mainly the structure of NaCI (Fm3‘m symmetry), thus can be considered as PbTe doped by antimony and silver.
It was found that the thermoelectric properties of compounds LAST are very sensitive to Chemical composition. LAST materials both n- and p-type can be obtained by adjusting the Chemical composition, which makes the system particularly promising for use in power generation. Therefore, it makes sense to optimize the composition for better thermoelectric properties.
The synthesis of compounds with warehouses Pbi8AgosSbi5Te2o, Pbi8Ag1SbiTe2o, Pbi8Ag1,5Sb0,5Te2o carried out in vacuumed quartz ampoules to a residual pressure of 10"4 Pa, which were placed in a two-zone furnace. Measurement of electrical parameters condensation was carried out at room temperaturę at constant magnetic and electric fields on the developed automated installation that provides a process for measuring electrical parameters and initial registration and data Processing. The resulting samples were investigated by atomie force microscopy (AFM) Nanoscope 3a Dimention 3000 (Digital Instruments USA) in the periodic contact.
From the AFM images shows that the vapor-phase condensation formed of nanosized crystallites pyramidal shape. Established that the average size of the nanocrystals with thickness of condensate inereased. Changing the composition does not significantly affect the shape and dimensions of nanocrystals but structures based compounds Pbi8Ago,5Sb,,5Te2o grain size inereases with thickness much fasterthan Pbi8Ag15Sbo,sTe2o.
Established that electrical conductivity (o) of the thickness (d) inereases for all of these structures. The smali values of the conductivity (o) and the Hall's mobility (p) with the substantial concentration of n-type carriers (n = 1019 cm’3), were caused by the phase inhomogeneity of the condensate: there were not only PbTe but Sb8Te3 and Sb. The current carrier mobility (p) of the condensates adequately replaces with a thickness (d): slightly inereases with d.
For room temperatures under experimental dependences of conductivity (o) from the inverse thickness (1/d) condensates mean free path of carriers \ is calculated according to Taylor's model for thin films based on Pbi8Agoi5-Sbii5Te2o is ~ 24 nm, and for Pbj8Agi,5-Sbo,sTe2o ~ 31 nm, due to the different structural perfection condensates.
The average length of free path of the current carriers and their mobility are determined at presence scattering on the surface and the intergrain limits of the nanocrystals. It is shown that the dominant carrier is scattering carrier on the surface, not on the intergrain limits, due to its huge size of the nanocrystals in the thin film structures.
The thermoelectric parameters of the surface layer is defined and the significant quantities of their Seebeck's coefficient is found by using Petrits's model.
Wpływ temperatury na stabilność fumaranu żelaza w suplementach diety dla kobiet: zastosowanie spektroskopii Móssbauera M. Kadziołka-Gaweł, K. Pająk
Zakład Fizyki Jądrowej i Jej Zastosowań, Instytut Fizyki, Uniwersytet Śląski w Katowicach
W pracy zbadano stan żelaza w fumaranie żelaza FeC4H204 w wybranych suplementach diety dla kobiet metodą spektroskopii Móssbauera. Do analizy wybrano suplementy, powszechnie dostępne i popularne wśród kobiet, takie jak: Prenatal® Classic, Pregnacare® Original oraz Falvit®. Określenie stopnia utlenienia żelaza (Fe2+ lub Fe3+) oraz jego zawartości w produkcie farmaceutycznym jest ważne z punktu widzenia jakości samego produktu jak również, przyswajalności Fe przez organizm. Badane suplementy zostały wygrzane w następujących temperaturach: 323K, 373K, 423K, 473K and 573K. Uzyskane, w temperaturze pokojowej, widma móssbauerowskie próbek wyjściowych wskazują na
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