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ABSTRACT: Impedance/admittance and dielectric spectroscopy were used to investigate the effect of temperature on the electrical response
of liquid-phase sintered Zn2SnO4-SnO2 ceramics. The measurements were performed over a wide frequency range (100Hz to 10MHz) at different temperatures. The real
and the imaginary part of the complex impedance traced semicircles in the complex plane. The resistance and the capacitance
of bulk and grain-boundary regions were determined by modeling the experimental results using several equivalent circuits
taking into account bulk deep trap states. Admittance complex diagrams were also determined in order to understand better
the conduction mechanisms occurring in the polycrystalline Zn2SnO4-SnO2 system.
KeywordsDielectric properties-electrical properties-solid-state ceramics
Journal of Electronic Materials 04/2012; 39(4):447-455. · 1.47 Impact Factor
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M. V. Nikolic,
K. M. Paraskevopoulos, T. Ivetić,
T. T. Zorba,
S. S. Vujatovic,
E. Pavlidou,
V. Blagojevic,
A. Bojicic,
O. S. Aleksic,
N. Nikolic,
W. König,
P. M. Nikolic
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ABSTRACT: Single crystals of lead telluride doped with Nd were synthesized using the Bridgeman method. Room temperature far infrared
reflectivity spectra were measured for PbTe samples with Nd content in the range 0.2–0.9at.%. Optical reflectivity in the
far infrared range was measured in the temperature range between 10 and 300K for a highly polished PbTe sample with 0.6at.%
Nd. The experimental diagrams were numerically analyzed with a fitting procedure using a modified plasmon–phonon model. Two
local modes were noted and their origin was discussed. Optical electron mobility was calculated for all analyzed samples.
Journal of Materials Science 04/2012; 45(21):5910-5914. · 2.02 Impact Factor
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ABSTRACT: A single crystal Bi0.9Sb0.1 ingot was synthesized using the Bridgman technique. Thermal diffusivity and electronic transport properties of single crystal cleaved plates (00l) were determined from PA photoacoustic phase and amplitude spectra obtained using the photoacoustic method with a transmission detection configuration. Both the PA phase and amplitude were measured versus the modulation frequency and numerically analyzed. EDS analyses done to determine chemical composition of the studied samples as well as to check sample homogeneity. Hall effect measurements data were used for the photoacustic measurements.
Science of Sintering. 01/2010;
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ABSTRACT: The effects of Bi(2)O(3) addition on the phase composition, microstructure and optical properties of ZnO-SnO(2) ceramics were investigated. Starting powders of ZnO and SnO(2) were mixed in the molar ratio 2:1. After adding Bi(2)O(3) (1.0 mol.%) this mixture was mechanically activated for 10 min in a planetary ball mill, uniaxially pressed and sintered at 1300 degrees C for 2 h. Far-infrared reflection spectra were measured (100-1000 cm(-1)). To investigate the occurred differences in FTIR spectra, the Bi(2)O(3)-doped sample was examined more carefully with a Perkin-Elmer FTIR spectrometer (Perkin Elmer, Waltham, MA, USA) connected with a Perkin-Elmer FTIR microscope and itemized points of interest were also studied with SEM-EDS.
Journal of Microscopy 01/2009; 232(3):498-503. · 1.63 Impact Factor
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ABSTRACT: The effects of Bi2O3 addition on the phase composition, microstructure and optical properties of ZnO–SnO2 ceramics were investigated. Starting powders of ZnO and SnO2 were mixed in the molar ratio 2:1. After adding Bi2O3 (1.0 mol.%) this mixture was mechanically activated for 10 min in a planetary ball mill, uniaxially pressed and sintered at 1300°C for 2 h. Far-infrared reflection spectra were measured (100–1000 cm–1). To investigate the occurred differences in FTIR spectra, the Bi2O3-doped sample was examined more carefully with a Perkin–Elmer FTIR spectrometer (Perkin Elmer, Waltham, MA, USA) connected with a Perkin–Elmer FTIR microscope and itemized points of interest were also studied with SEM-EDS.
Journal of Microscopy 11/2008; 232(3):498 - 503. · 1.63 Impact Factor
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P.M. Nikolić,
K.M. Paraskevopoulos,
T.T. Zorba,
E. Pavlidou,
N. Kantiranis,
S.S. Vujatović,
O.A. Aleksić,
M.V. Nikolić, T. Ivetić,
S. Savić,
N. Labus,
V. Blagojević
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ABSTRACT: Far infrared spectra of sintered PbTe doped with boron were analyzed. The measured infrared spectra were fitted using a modified plasmon-phonnon interaction model with two additional oscillators (at about 195 cm-1 and 285 cm-1) representing local B-impurity modes. The obtained results were compared with previously published data for a single crystal PbTe sample doped with boron.
Science of Sintering. 01/2007;
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ABSTRACT: Mixtures of ZnO and SnO2 powders, with molar ratio of 2:1, were mechanically activated for 40, 80 and 160 minutes in a planetary ball mill. The resulting powders were compacted into pellets and non-isothermally sintered up to 1200°C with a heating rate of 5°C/min. X-ray diffraction analysis of obtained powders and sintered samples was performed in order to investigate changes of the phase composition. The microstructure of sintered samples was examined by scanning electron microscopy. The photoacoustic phase and amplitude spectra of sintered samples were measured as a function of the laser beam modulating frequency using a transmission detection configuration. Fitting of experimental data enabled determination of photoacoustic properties including thermal diffusivity. Based on the results obtained a correlation between thermal diffusivity and experimental conditions as well the samples microstructure characteristics was discussed. .
Science of Sintering. 01/2007;
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ABSTRACT: The effects of small amounts (0.5; 1.0 and 1.5 mol. %) of bismuth oxide on the microstructure and electrical properties of ZnO-SnO2 ceramics have been studied. Starting powders of ZnO and SnO2 were mixed in the molar ratio 2:1. After adding Bi2O3 this mixture was mechanically activated for 10 minutes in a planetary ball mill, uniaxially pressed and sintered at 1300ºC for 2h. The phase composition of the sintered samples was analyzed by X-Ray Diffraction (XRD) and by Energy Dispersive Spectrometer (EDS). Morphologies were examined by Scanning Electron Microscopy (SEM). An Impedance/Gain Phase Analyzer (HP 4194A) was used to measure the impedance spectra (100Hz - 10MHz) at different temperatures. The electrical DC resistivity/conductivity at different temperatures was measured using a High Resistance Meter (HP 4329A).
Science of Sintering. 01/2007;
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ABSTRACT: Room temperature far infrared reflectivity spectra of single phase spinel zinc-stannate thin films, prepared by rf magnetron sputtering on a glass substrate, and bulk sintered samples were measured. The sintered samples were obtained by mechanical activation of starting ZnO and SnO2 powders for 10 min followed by sintering at 1300 °C for 2 h. The reflectivity diagrams obtained for bulk samples were numerically analyzed using the four-parameter model of coupled oscillators. The optical parameters were determined for six observed ionic oscillators belonging to the spinel structure and two additional oscillators originating from the sintering procedure resulting from pores and grain boundaries. The reflectivity diagrams obtained for thin film samples were analyzed using the four-parameter model for optical phonons with a standard optical multi-layer technique.
Materials Science and Engineering: B. 138(1):7-11.
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ABSTRACT: A mixture of starting ZnO and SnO2 powders (molar ratio 2:1) were mechanically activated for 10, 40, 80 and 160 min in a planetary ball mill and then isothermally sintered at 1300 °C for 2 h in order to obtain Zn2SnO4 ceramics. X-ray diffraction analysis confirmed single-phase polycrystals. Far infrared reflection spectra were measured (100–1400 cm−1). The same oscillators were observed, but the highest intensity of reflectivity peaks was obtained for the powder activated 10 min and it gradually decreased with longer times of mechanical activation. This is in agreement with microstructure analysis where longer times of mechanical activation lead to increased porosity and defects. Using group theory six ionic oscillators were calculated for single crystal Zn2SnO4 spectra, but two more oscillators were observed in the obtained experimental spectra, which could be the result of mechanical activation and sintering. The FIR experimental results were numerically analyzed and oscillator parameters were calculated.
Journal of the European Ceramic Society.
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ABSTRACT: Single-phase zinc-stannate thin films of different thickness values were prepared by radio frequency magnetron sputtering on a silica substrate. Rietveld analysis of X-ray diffraction data confirmed that the films had an inverse spinel structure, with a cation inversion parameter of 0.8. Room temperature far and mid infrared reflectivity spectra were measured in the range 50–4000 cm− 1. The reflectivity diagrams were analyzed using the four-parameter model of coupled oscillators for optical phonons with a standard multi-layer technique taking into account the thin-film layer and the substrate. The optical parameters were determined for seven oscillators belonging to the spinel structure. Their origin was discussed in relation to non-stoichiometry of the thin film and cation disorder in the crystal lattice. Born effective charges were calculated from the transversal/longitudinal splitting.
Thin Solid Films.
