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51. Guest editors' note

Author

Petzelt, Jan, primary, Hlinka, Jiří, additional, Hilczer, Bożena, additional, and Pawłowski, Antoni, additional

Published
2014
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55. Guest Editorial

Author

Hilczer, Bożena, primary, Noda, Yukio, additional, Petzelt, Jan, additional, and Roleder, Krystian, additional

Published
2014
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56. Dielectric properties of carbon nanofibre/alumina composites

Author

Ministry of Education, Youth and Sports (Czech Republic), Consejo Superior de Investigaciones Científicas (España), European Commission, Czech Science Foundation, Ministerio de Economía y Competitividad (España), Fernández-García, Lucía, Suárez, Marta, Menéndez, José Luis, Pecharromán, Carlos, Nuzhnyy, Dmitry, Bovtun, Viktor, Savinov, Maxim, Kempa, Martin, Petzelt, Jan, Ministry of Education, Youth and Sports (Czech Republic), Consejo Superior de Investigaciones Científicas (España), European Commission, Czech Science Foundation, Ministerio de Economía y Competitividad (España), Fernández-García, Lucía, Suárez, Marta, Menéndez, José Luis, Pecharromán, Carlos, Nuzhnyy, Dmitry, Bovtun, Viktor, Savinov, Maxim, Kempa, Martin, and Petzelt, Jan

Abstract

Carbon nanofibre (CNF)/Al2O3 composites with concentrations between 1 and 9 vol.% of CNF were prepared by the traditional ceramic processing route followed by spark plasma sintering. The dielectric properties of these composites have been studied in a broad frequency range from mHz to the infrared range. Unlike conventional composites, the percolation threshold in this system is more complex depending on the particles topology. Positive and negative variations by several orders of magnitude in the low frequency AC conductivity have been detected for concentrations near the threshold at ∼2 vol.% of CNF. To explain these results, a modified percolation model has been proposed which takes into consideration the effect of the concentration of the filler on the microstructure of the composite. © 2013 Elsevier Ltd. All rights reserved.

Published
2013

62. Guest Editorial

Author

Roleder, Krystian, primary, Hilczer, Bożena, additional, Petzelt, Jan, additional, and Glogarová, Milada, additional

Published
2010
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65. Guest Editorial

Author

Bhalla, Amar S., primary, Fridkin, Vladimir M., additional, Ishibashi, Yoshihiro, additional, Lang, Sidney B., additional, Petzelt, Jan, additional, and Taylor, Deborah J., additional

Published
2010
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68. Properties of BaTiO3 confined in nanoporous Vycor and artificial opal silica

Author

Nuzhnyy, Dmitry, primary, Vaněk, Přemysl, additional, Petzelt, Jan, additional, Bovtun, Viktor, additional, Kempa, Martin, additional, Gregora, Ivan, additional, Savinov, Maxim, additional, Krupková, Radmila, additional, Studnicka, Václav, additional, Bursík, Josef, additional, Samoylovich, Mihail, additional, and Schranz, Wilfried, additional

Published
2010
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69. Ferroelectric and Incipient Ferroelectric Properties of a Novel Sr9−xPbxCe2Ti12O36(x = 0−9) Ceramic System

Author

Kamba, Stanislav, primary, Savinov, Maxim, additional, Laufek, František, additional, Tkáč, Ondřej, additional, Kadlec, Christelle, additional, Veljko, Sergiy, additional, John, Elizabeth J., additional, Subodh, Ganesanpotti, additional, Sebastian, Mailadil T., additional, Klementová, Mariana, additional, Bovtun, Viktor, additional, Pokorný, Jan, additional, Goian, Veronica, additional, and Petzelt, Jan, additional

Published
2009
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77. Lattice dynamics and dielectric spectroscopy of BZT and NBT lead-free perovskite relaxors – comparison with lead-based relaxors.

Author

Petzelt, Jan, Nuzhnyy, Dmitry, Bovtun, Viktor, Kempa, Martin, Savinov, Maxim, Kamba, Stanislav, and Hlinka, Jiri

Subjects
*IMPEDANCE spectroscopy, *PEROVSKITE, *LEAD, *CRYSTAL lattices, *TITANIUM dioxide, *METAL quenching
Abstract

Appearance of the polar nanoregions (PNR) and their manifestation in the dielectric spectra is discussed for lead-free Ba(ZrxTi1−x)O3(BZT-x) and (Na1/2Bi1/2)TiO3(NBT) ceramics. Phonon softening is not as pronounced as in the lead-based relaxors, but the relaxation contribution is dominating in all cases, caused by the dynamics of the off-centred ions (Ti4+, Bi3+, Pb2+). In the lead-based relaxors, where there is no relation between the quenched chemical clusters at the B-sites and PNR, which concern the A-site Pb-ion correlations, the relaxation dynamics follows the Vogel–Fulcher behaviour with a clear freezing. However, in BZT and NBT, the PNR are smaller, since they are localised within the small quenched chemical clusters of BaTiO3and BiTiO3, respectively. Their dynamics is Arrhenius-like, which indicates hopping of the off-centred Ti4+and Bi3+ions, respectively, without their complete freezing. BZT can be classified as a dipolar glass and NBT as a nanoscopic ferroelectric with peculiar Bi-ion dynamics. [ABSTRACT FROM PUBLISHER]

Published
2015
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81. Far infrared response of α- and αt-(BEDT-TTF)2I3

Author

Zelezný, Vladimir, Petzelt, Jan, Swietlik, Roman, Gorshunov, Boris P., Volkov, Alexander, Kozlov, Gennadij, Schweitzer, Dieter, and Keller, Heimo J.

Subjects
Tetrathiafulvalen , Organischer Supraleiter , Infrarot-Spektrum
Abstract

The temperature dependence of the reflectivity of α- and αt-(BEDT-TTF)2I3 was determined in the 10-700 cm-1 range. Moreover the transmission spectra of α-phase between 10 and 33 cm-1 were studied. Using Kramers-Kronig analysis the IR conductivity and permittivity were calculated. The similarity of α t and β-phases was confirmed. The spectra in the metallic phase are dominated by a broad electronic peak between 200 and 500 cm-1 which can be understood as due to transitions across the small gap whose origin is discussed. In the spectra a rich phonon peak structure is observed, mostly of vibronic origin. It is suggested that non totally symmetric modes of BEDT-TTF molecule can couple with electrons., On a déterminé la dépendance en température de la réflectivité des phases α et αt de (BEDT-TTF)2I3 dans le domaine 10-700 cm-1. En outre, on a étudié les spectres de transmission de la phase α entre 10 et 33 cm-1. La conductivité infrarouge et la permittivité ont été calculées au moyen d'une analyse Kramers-Kronig. Des similarités ont été notées entre les phases αt et β. Des transitions à travers un petit gap (dont l'origine reste à discuter) permettent d'interpréter le pic élargi de la phase métallique situé entre 200 et 500 cm-1. Une structure foisonnante en pics est attribuée à des effets vibroniques. Nous suggérons que des modes impartiellement symétriques de la molécule BEDT-TTF peuvent être couplés aux électrons.

Published
1990

84. Ferroelectric properties of dense nanocrystalline BaTiO3ceramics

Author

Buscaglia, Maria Teresa, primary, Buscaglia, Vincenzo, additional, Viviani, Massimo, additional, Petzelt, Jan, additional, Savinov, Maxim, additional, Mitoseriu, Liliana, additional, Testino, Andrea, additional, Nanni, Paolo, additional, Harnagea, Catalin, additional, Zhao, Zhe, additional, and Nygren, Mats, additional

Published
2004
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99. Far infrared and Raman spectroscopy of ferroelectric soft mode in SrTiO3 thin films and ceramics

Author

Petzelt, Jan, primary, Ostapchuk, Tetyana, additional, Gregora, Ivan, additional, Hoffmann, Susanne, additional, Lindner, Johannes, additional, Rafaja, David, additional, Kamba, Stanislav, additional, Pokorny, Jan, additional, Bovtun, Viktor, additional, Porokhonsky, Viktor, additional, Savinov, Maxim, additional, Vaněk, Přemysl, additional, Rychetský, Ivan, additional, Peřina, Vratislav, additional, and Waser, Rainer, additional

Published
2001
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