Browsing by Author "Novak P."

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    Dielectric behaviors at microwave frequencies and Mössbauer effects of chalcedony, agate, and zultanite
    (Institute of Physics Publishing, 2015) Parali L.; Şabikoʇlu I.; Tucek J.; Pechousek J.; Novak P.; Navarik J.
    In this study, dielectric properties within 8-12 GHz microwave frequencies, inductively coupled plasma-atomic emission spectrometry, Fourier transform infrared spectrometry, synchronized two thermal analyses, and 57Fe Mössbauer spectroscopy analysis of chalcedony, agate, and zultanite samples from Turkey are presented. Agate and chalcedony show the same nine vibrational absorption peaks obtained unlike zultanite from FTIR spectra in the 350 cm-1 to 4000 cm-1 range, ε′ values of chalcedony, agate and zultanite derived at 10.5 GHz were 4.67, 4.41, and 7.34, respectively, ε′ and ε″ values of the studied samples at the microwave frequencies are related to the percentage weight of their constituent parts in their chemical compositions. 57Fe Mössbauer spectroscopy results confirm the existence of iron-containing islands in the crystal structure of zultanite, agate, and chalcedony samples, equipped them with magnetic features typical for magnetic nanoparticles including superparamagnetism. The presence of iron-containing islands significantly affects the magnetic, dielectric, and optical properties of studied samples that are not observed for pure minerals without any foreign inclusions. © 2015 Chinese Physical Society and IOP Publishing Ltd.
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    The effect of neodymium substitution on the structural and magnetic properties of nickel ferrite
    (Elsevier B.V., 2015) Şabikoğlu I.; Parali L.; Malina O.; Novak P.; Kaslik J.; Tucek J.; Pechousek J.; Navarik J.; Schneeweiss O.
    Nickel ferrite NiFe2O4 is a typical soft magnetic ferrite with high electrical resistivity used as high frequency magnetic material. Neodymium (Nd3+) doped NiFe2O4 materials were fabricated using solid state reaction. The properties of the obtained material were investigated by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR), magnetic measurements on SQUID and Mössbauer spectroscopy. It was found that the material consists of two different phases: Nd3+ doped NiFe2O4 and NdFeO3. The Nd3+ ions occupy cation sites of the NiFe2O4 inverse spinel structure. NdFeO3 phase occurred when the level of Nd3+ atoms exceed a percolation limit. The presence of both phases was confirmed by SEM observations. The Mössbauer spectra analysis showed two sextets, which can be ascribed to iron atoms in tetrahedral and octahedral positions. From their intensities it is concluded that Nd3+ occupies octahedral sites in the spinel structure of NiFe2O4, which were originally occupied by Ni2+. © 2015 The Authors.
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    A digital measurement system based on laser displacement sensor for piezoelectric ceramic discs vibration characterization
    (Elsevier GmbH, 2016) Parali L.; Pechousek J.; Şabikoʇlu I.; Novak P.; Navarik J.; Vujtek M.
    This study describes the innovative design of a digital measurement system based on a laser displacement sensor (LDS) as a vibrometer which is capable to measure a dynamic displacement response dependence on a stimulated vibration. The frequency response of a piezoelectric ceramic disc is obtained by processing the input/output signals obtained from the function generator and digital oscilloscope (digitizer) cards driven by a personal computer. Resonant frequencies of vibration are achieved utilizing the swept-sine signal excitation following the peak values in the signal response measured by LDS. The analogue signal from LDS controller represents directly a mechanical vibration of a piezoceramic disc. The test measurement results indicate that the system can distinguish resonance frequencies of piezoelectric ceramic discs up to 40 kHz with the resolution 1 Hz. Piezoelectric coefficient d33 and its linearity along the excited voltage amplitudes have been calculated by the applied methods as a demonstration of a successful system concept. The results achieved are in compliance with the reference value declared by the manufacturer of the piezoceramic disc. © 2015 Elsevier GmbH. All rights reserved.
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    Calibration of gamma-ray detectors using Gaussian photopeak fitting in the multichannel spectra with a LabVIEW-based digital system
    (Institute of Physics, 2017) Schlattauer L.; Parali L.; Pechousek J.; Sabikoglu I.; Celiktas C.; Tektas G.; Novak P.; Jancar A.; Prochazka V.
    This paper reports on the development of a gamma-ray spectroscopic system for the (i) recording and (ii)rocessing of spectra. The utilized data read-out unit consists of a PCI digital oscilloscope, personal computer and LabVIEW™ programming environment. A pulse-height spectra of various sources were recorded with two NaI(Tl) detectors and analyzed, demonstrating the proper usage of the detectors. A multichannel analyzer implements the Gaussian photopeak fitting. The presented method provides results which are in compliance to the ones taken from commercial spectroscopy systems. Each individual hardware or software unit can be further utilized in different spectrometric user-systems. An application of the developed system for research and teaching purposes regarding the design of digital spectrometric systems has been successfully tested at the laboratories of the Department of Experimental Physics. © 2017 European Physical Society.