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Charge Carrier Generation Caused by X-Rays in Organometallic Materials

100%
Godlewski J., Signerski R., Jarosz G., Stizza S., Berrettoni M.
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vol. 96
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issue 2
295-301
EN
Organometallic compounds play an exceptional role among organic compounds. Due to their structure a number of these compounds demonstrate interesting properties in various phenomena. Organometallic compounds show special properties in the case of X-ray absorption owing to considerable differences between the absorption coefficients of metals and light elements. The analysis of processes of charge carrier generation as a result of X-ray absorption in chosen organometallic compounds is the subject of this paper. Spectral dependences of charge carrier photogeneration efficiency around the Cu K-edge in copper phthalocyanine and copper acetylacetoniane have been specially considered. It has been observed that the photocurrent spectrum in these materials follows the absorption spectrum but mutual relation is not directly proportional. Experimental results connected with current-voltage and current-intensity characteristics have been analysed, as well. The obtained relationships have been compared with adequate results connected with charge carrier photogeneration in visible area and UV in organic materials. It has been observed that the X-ray photogeneration of charge carriers in the examined range of energy differs from the mechanisms of charge carrier generation in visible area and UV. The basic differences arise from the participation of secondary electrons, which are generated due to Auger electrons, Compton effect, and metal fluorescence. The process of charge carrier generation as a result of X-rays absorption is characterized by strong recombination of charge carriers in channels in which charge carriers are generated by high energetic secondary electrons.
2
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Superconducting Properties of BiPbSrCsCuO and BiSrCaCuO Glass-Ceramics

100%
Miller W., Borówko K., Gazda M., Stizza S., Natali R.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
627-631
EN
In this work we study the main differences between the superconducting properties of the Bi_4Sr_3Ca_3Cu_4O_x and (Bi_{0.8}Pb_{0.2})_4Sr_3Ca_3Cu_4O_x glass-ceramics. The Bi_4Sr_3Ca_3Cu_4O_x and (Bi_{0.8}Pb_{0.2})_4Sr_3Ca_3Cu_4O_x glass-ceramics prepared in the same conditions contain similar amounts of the superconducting 2212 phase, however their superconducting and normal-state electrical properties differ significantly. The main reason which makes BiSrCaCuO glass-ceramics worse superconductor than BiPbSrCaCuO is its microstructure.
3
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Superconducting Transition in Granular Bi-Sr-Ca-Cu-O Superconductors

86%
Gazda M., Kusz B., Sadowski W., Stizza S., Natali R., Di Stasio V.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
485-491
EN
In this work we study the superconducting transition in the samples containing relatively small granules of high-T_c Bi-Sr-Ca-Cu-O superconductors. The samples were obtained by the glass-ceramic technology. Two-stage character of the superconducting transition was studied. Pairing transition temperature depends on the magnetic field. Coherence transition is very sensitive to the current flowing through the sample, magnetic field and the phase composition and microstructure of the sample. The analysis of superconducting transition by means of the logarithmic derivative of the fluctuation conductivity shows the mesoscopic granularity of the samples.
4
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Conductivity and Superconductivity of (Bi,Pb)_4Sr_3Ca_3Cu_4O_x Glass-Ceramics

86%
Gazda M., Kusz B., Stizza S., Chudinov S., Natali R., Piętosa J., Bienias A.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
617-625
EN
In the (Bi,Pb)-Sr-Ca-Cu-O system, materials of various electrical and superconducting properties may be produced by a glass-ceramic method. Phase composition, structure, microstructure and also electrical properties of the material change as a result of heat treatment. Depending on the heat treatment conditions, either a superconductor with the critical temperature between 8 and 105 K or material without a superconducting transition may be obtained. The properties of the material change so much because during annealing three oxide superconductors belonging to the bismuth family are formed. (Bi_{0.8}Pb_{0.2})_4Sr_3Ca_3Cu_4O_x glass was prepared by a standard technique of quenching homogenized and melted substrates. The glass-ceramic samples were obtained by annealing of the glass beneath melting temperature. Structure and microstructure of glass-ceramic samples were studied with scanning electron microscopy and X-ray diffraction method. Superconducting properties were studied by means of electrical conductivity and magnetization measurements. In this paper we present the influence of the phase composition, structure and microstructure on the electrical conductivity in the normal state and the superconducting properties of (Bi,Pb)_4Sr_3Ca_3Cu_4O_x glass-ceramics.
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