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Wyświetlanie 1-15 z 34
Tytuł:
Polymer-oxide composites: toward new optical materials
Autorzy:
Nedilko, S.
Powiązania:
https://bibliotekanauki.pl/articles/1052642.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Ch
78.55.-m
78.66.Sq
Opis:
Brief summary concerning properties of the polymer matrix incorporated with inorganic, e.g. oxide particles, micro/nanocomposites and opportunity to use these composites as optical materials for modern optics and optoelectronic devices is presented in the work. Structure and morphology of the several sets of the new polymer micro/nanocomposites based on the microcrystalline cellulose incorporated with micro/nanoparticle of various oxides (NaNO₂, La_{1-x}Sm_{x}VO₄, La_{1-x}Eu_{x}VO₄ and K₂Eu(PO₄)(MoO₄)), were prepared by "dry" and "wet" cool pressing procedure. Morphology of these composites was described as ensemble of cellulose plates and located gains of the oxide particles. Temperature dependences of complex dielectric permittivity and luminescence properties of the composites were studied. Temperature and electromagnetic field frequency dependences of the dielectric permittivity revealed influence of oxide particles on the characteristics of the microcrystalline cellulose. Both wide band (matrix emission) and narrow lines (RE ions emission) of visible luminescence (350-750 nm range) of the composites is excited in the range 250-550 nm. The luminescence characteristics displayed effect of cellulose on the electronic system of the Sm³⁺ and Eu³⁺ ions and effect of oxide particles on the cellulose matrix was shown, too. Spectral characteristics and high intensity of luminescence showed perspectives of studied composites to be used as light converters in LED and elsewhere as optics luminescent materials.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 829-837
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Properties of Triglycine Sulphate Crystals Admixtured with L-Threonine
Autorzy:
Czarnecka, A.
Stankowska, J.
Mielcarek, S.
Powiązania:
https://bibliotekanauki.pl/articles/1931325.pdf
Data publikacji:
1994-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Ch
Opis:
The influence of L-threonine admixture on the dielectric properties of triglycine sulphate (TGS) crystals was studied. With increasing concentration of the admixture in the solution from which the crystals were grown, their maximum permittivity and spontaneous polarization were found to decrease, their Curie point was found not much different than that for pure TGS crystals (322 K), the coercive field and bias field increased. The domain structure of the obtained crystals was also studied by the liquid crystal method.
Źródło:
Acta Physica Polonica A; 1994, 85, 5; 849-858
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Dielectric Studies of Ferroelectric [NH$\text{}_{2}$(CH$\text{}_{3}$)$\text{}_{2}$]$\text{}_{3}$Sb$\text{}_{2}$Cl$\text{}_{9}$ Crystals under Moderate Pressure
Autorzy:
Zdanowska-Frączek, M.
Olszewski, M.
Frączek, Z. J.
Jakubas, R.
Powiązania:
https://bibliotekanauki.pl/articles/2047740.pdf
Data publikacji:
2007-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.45.Gm
77.84.Fa
77.22.Ch
77.80.Bh
Opis:
The effect of pressure on the dielectric properties of [NH$\text{}_{2}$(CH$\text{}_{3}$)$\text{}_{2}$]$\text{}_{3}$Sb$\text{}_{2}$Cl$\text{}_{9}$ crystal was analyzed for a few values of hydrostatic pressure within the range from 0.1 MPa to 300 MPa and for temperatures from the range of 220-350 K. The measuring frequency was 1 kHz. The pressure-temperature phase diagram obtained was nonlinear. The temperature dielectric permittivity anomalies related to the paraelectric-ferroelectric phase transition temperature (T$\text{}_{c}$) gradually increase up to 66 MPa and then decrease with subsequent increase in pressure. The character of the temperature dielectric permittivity anomalies, typical of the continuous ferroelectric transition, remains unchanged with increasing pressure. Additionally, the pressure dependences of the Curie-Weiss constants for the crystal in paraelectric (C$\text{}_{+}$) and ferroelectric (C$\text{}_{-}$) phases were evaluated and discussed. The results indicated a complex mechanism of the ferroelectric phase transition.
Źródło:
Acta Physica Polonica A; 2007, 112, 3; 549-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and Birefringent Properties of [(CH$\text{}_{3}$)$\text{}_{2}$NH$\text{}_{2}$]$\text{}_{5}$Cd$\text{}_{2}$CuCl$\text{}_{11}$ Solid Solutions in the Region of Their Phase Transitions
Autorzy:
Eliyashevskyy, Yu.
Kapustianyk, V.
Dacko, S.
Czapla, Z.
Batiuk, A.
Sveleba, S.
Powiązania:
https://bibliotekanauki.pl/articles/2044636.pdf
Data publikacji:
2006-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.40.-b
77.22.Ch
Opis:
On the basis of the optical and dielectric investigations of [(CH$\text{}_{3}$)$\text{}_{2}$NH$\text{}_{2}$]$\text{}_{5}$Cd$\text{}_{2}$CuCl$\text{}_{11}$ solid solutions the existence of phase transitions at T$\text{}_{1}$=175 K and T$\text{}_{2}$=117.5 K was confirmed. Both phase transitions were found to be shifted toward lower temperatures with respect to the corresponding transitions in the "host" [(CH$\text{}_{3}$)$\text{}_{2}$NH$\text{}_{2}$]$\text{}_{5}$Cd$\text{}_{3}$Cl$\text{}_{11}$ crystals. It was found that the proton conductivity in [(CH$\text{}_{3}$)$\text{}_{2}$NH$\text{}_{2}$ ]$\text{}_{5}$Cd$\text{}_{2}$CuCl$\text{}_{11}$ crystals is realized through the Grotthus mechanism. The investigations of the birefringent properties confirmed existence of the structural changes at T$\text{}_{0}$=320 K connected with the complex co-operative effect involving weakening of the hydrogen bonds and modification of the Jahn-Teller distortion with temperature.
Źródło:
Acta Physica Polonica A; 2006, 109, 2; 171-178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric and AC Conductivity οf Potassium Perchlorate, $KCLO_{4}$
Autorzy:
Abdelmoneim, H.
Powiązania:
https://bibliotekanauki.pl/articles/1537744.pdf
Data publikacji:
2010-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ph
77.22.Ch
77.84.Bw
Opis:
The AC conductivity σ (ω) and the complex dielectric permittivity ε*(ω) were studied as function of temperature 300 K < T < 600 K and at some selected frequencies (1-20 kHz) for polycrystalline sample of $KClO_4$. The differential thermal analysis (DTA) thermograph was also performed. The combined data support each other and indicate the existence of a structural phase transition at ≈ 575 K. Moreover, the temperature dependence of the ac conductivity behaves in accordance with Arrhenius relation, whereas the frequency dependent conductivity obeys the power law $σ(ω) = Aω^{s(T)}$. The behavior of s with temperature suggests that the hopping over the barrier model prevails. No evidence for the existence of a ferroelectric phase transition at the transition temperature.
Źródło:
Acta Physica Polonica A; 2010, 117, 6; 936-940
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Complex Dielectric Coefficient of Breast Phantom Prepared for Breast Cancer Detection
Autorzy:
Sayinti, A.
Açikalin, E.
Çoban, K.
Vertii, A.
Powiązania:
https://bibliotekanauki.pl/articles/1400036.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Ch
Opis:
Microwave measurement techniques attract attention due to its practical solutions in breast cancer imaging. Early detection of cancer is the purpose of these imaging studies. For these imaging processes, phantoms which reflect the properties of the area to be imaged are produced. The produced homogeneous phantoms are imaged by stepper frequency of radar technology, as the narrow bands are used for heterogeneous mixtures. Phantoms are used since 70's until today. Different methods are experimented for producing phantoms of tissue, muscle, fat, skin, etc. Iron powder, polymer materials, various oils and gelatins used today are the materials used for producing the phantoms. In this study, phantom breast imaging is aimed. Phantoms breast and breast tumor samples are created. For phantoms and tumor samples, reflection and transmittion measurements are done with Network Analyzer in X-Band (8.2-12.4 GHz). Complex permittivity is calculated with Agilent 85071 Material Measurement Software-Fast Method (NIST-iterative method). It was considered breast phantom with tumor model for 3D imagine at 2-3.5 GHz frequency range.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 464-466
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ballistic Transport Phenomena in Nanostructures of Paraelectric Lead Telluride
Autorzy:
Grabecki, G.
Powiązania:
https://bibliotekanauki.pl/articles/2047366.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Jc
73.21.Hb
73.23.Ad
77.22.Ch
Opis:
This is a review of our recent developments in the physics of lead telluride nanostructures. PbTe is a IV-VI narrow gap paraelectric semiconductor, characterized by the huge static dielectric constant ε >1000 at helium temperatures. We nanostructurized this material by means of e-beam lithography and wet chemical etching of modulation doped PbTe/Pb$\text{}_{1-x}$Eu$\text{}_{x}$Te quantum wells. Magnetoresistance measurements performed on the nano-structures revealed a number of magnetosize effects, confirming a ballistic motion of the carriers. The most important observation is that the conductance of narrow constrictions shows a precise zero-field quantization in 2e$\text{}^{2}$/h units, despite a significant amount of charged defects in the vicinity of the conducting channel. This unusual result is a consequence of a strong suppression of the Coulomb potential fluctuations in PbTe, an effect confirmed by numerical simulations. Furthermore, the orbital degeneracy of electron waveguide modes can be controlled by the width of PbTe/Pb$\text{}_{1-x}$Eu$\text{}_{x}$Te quantum wells, so that unusual sequences of plateau conductance can be observed. Finally, conductance measurements in a nonlinear regime allowed for an estimation of the energy spacing between the one-dimensional subbands.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 127-139
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrocaloric Cooling - A New Application of Relaxor Ferroelectrics
Autorzy:
Suchaneck, G.
Gerlach, G.
Powiązania:
https://bibliotekanauki.pl/articles/1031012.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.70.+a
84.60.Bk
77.80.Jk
77.22.Ch
Opis:
Until now, relaxor ferroelectrics are considered as a class of disordered materials possessing peculiar structures and properties which are not yet generalized into a universal model explaining the significant amount of experimental data available. In this work, we demonstrate that one feature of relaxor ferroelectrics - the extraordinary dielectric response - is well-suited for application in electrocaloric refrigerators. We consider the electrocaloric effect with special attention to relaxor ferroelectrics, the dielectric response in the temperature region of interest, the efficiency and the figure of merit of relaxor ferroelectrics for electrocaloric application.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 1003-1005
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multiferroic Cobalt Ferrite-Lead Iron Tungstate Composites
Autorzy:
Kulawik, J.
Szwagierczak, D.
Guzdek, P.
Powiązania:
https://bibliotekanauki.pl/articles/1490917.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.-y
75.60.Ej
75.85.+t
77.22.Ch
Opis:
The paper presents dielectric, magnetic and magnetoelectric properties of multiferroic bulk composites based on $CoFe_2O_4$ ferrite and $Pb(Fe_{2//3}W_{1//3})O_3$ relaxor. X-ray diffraction analysis and scanning electron microscopy observations of ceramic samples revealed two-phase composition and fine grained microstructure with uniformly distributed ferromagnetic and ferroelectric phases. Dielectric permittivity measured in a temperature range 218-773 K at frequencies of 10 Hz-2 MHz exhibits high and broad maxima attributed to dielectric relaxation. The hysteresis determined in a temperature range 4-393 K for magnetic field changing from - 80 kOe to 80 kOe is typical of hard magnetic materials. Saturation magnetizations and coercivities were found to decrease with increasing temperature. The courses of zero field cooled and field cooled magnetization versus temperature curves measured in the temperature range 4-393 K imply spin glass behavior of the ferrite and antiferromagnetic transition of the relaxor at low temperatures. The ferrite-relaxor composite shows high magnetoelectric voltage coefficient which distinctly increases with increasing frequency of ac magnetic field and is slightly higher for higher ac and dc magnetic fields.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 122-124
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electric relaxation in Nb₆VSb₃O₂₅-ceramics
Autorzy:
Groń, T.
Filipek, E.
Piz, M.
Kukuła, Z.
Pawlus, S.
Powiązania:
https://bibliotekanauki.pl/articles/1070621.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Ch
77.22.Gm
77.84.Bw
Opis:
Broadband dielectric spectroscopy measurements of Nb₆VSb₃O₂₅ showed that in both the real (ε') and imaginary (ε'') components of permittivity there is visible relaxation process strongly obscured by dc conductivity. Application of the electric modulus representation of the data enables to study temperature evolution of this relaxation together with conductivity relaxation. It was showed that the activation energies for both processes are close. Low-frequency loss tangent increases strongly with temperature, suggesting that in the compound under study additional energy losses are associated with the conduction of electric current, as determined by the Joule-Lenz law.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 355-358
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Measurement of Complex Permittivity of Oil-Based Ferrofluid in Magnetic Field
Autorzy:
Kúdelčík, J.
Hardoň, Š.
Varačka, L.
Powiązania:
https://bibliotekanauki.pl/articles/1030262.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.65.Cb
77.22.Gm
77.22.Ch
Opis:
The changes of dielectric parameters in oil-based ferrofluid have been measured in an external magnetic field. The frequency dependent real permittivity and the dissipation factor were measured within the frequency ranges from 1 mHz to 2 MHz by a capacitance method. These parameters have been studied in combined electric and magnetic field, when fields were parallel and perpendicular. The Cole-Cole model has been used to analyze measured data. When a magnetic field was applied, the interaction between the magnetic field and magnetic moments of nanoparticles led to the aggregation of magnetic nanoparticles to new structures - thick chains which had influence on the value of dielectric permittivity. At constant magnetic field the dependence of real permittivity and tanδ on angle between the electric and magnetic field (anisotropy) were measured, too. The various influences of magnetic field development on the investigated liquid are discussed.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 931-933
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the Low Frequency Polarization Mechanisms in Magnetic Fluids
Autorzy:
Marin, C.
Malaescu, I.
Savici, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399307.pdf
Data publikacji:
2013-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Mm
77.22.Ej
77.22.Ch
31.30.jn
Opis:
The dielectric behaviour of a magnetic fluid with magnetite particles dispersed in kerosene was analyzed. Therefore, the frequency (f) and temperature (T) dependences of the complex dielectric permittivity, ε (f, T), over the ranges 4 kHz to 2 MHz and 25C to 90C were measured. Based on the experimental results of ε (f, T) and using the Clausius-Mossotti equation, we have determined the temperature dependence of the real part of the total polarizability α', of a magnetic fluid. The computations have taken into account that the magnetic fluid consists of three components, namely magnetite particles, surfactant, and carrier liquid. The results show that at a given frequency, α' increases with temperature in the low frequency range (4 kHz to 100 kHz) and decreases with temperature above 100 kHz. This behaviour demonstrates that in low frequency range the polarization mechanism related to the deformation of the counter ions atmosphere around each particle is predominant and above 100 kHz the orientation of the dipole moments is the main polarization mechanism of the magnetic fluid. These measurements enabled the evaluation of the effective dipole moment of the magnetic fluid, in order of $1.21 \times 10^{-30} C m$.
Źródło:
Acta Physica Polonica A; 2013, 124, 4; 724-727
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microwave X-Band Resonances in Doped Cd₂Nb₂O₇ Monocrystals
Autorzy:
Waplak, S.
Ostrowski, A.
Wencka, M.
Bednarski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1030214.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.Fc
77.22.Ch
77.80.B-
77.84.Ek
Opis:
Cadmium pyroniobiate (CNO) is the ferroic material with unusual diffuse phase diagram which includes both relaxor and nanocluster domains. We present the data for CNO crystals with several admixtures of paramagnetic ions studied on X and S microwave bands at zero-external magnetic field and classical EPR conditions. Our results lead to an assertion of a ferroelectric resonance effect due to "electronic ferroelectricity". The data fit well to the Falicov-Kimball theoretical model applicable to strongly-correlated-electron or mixed-valence systems.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 7-11
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Study of Pressure Induced fcc-sc Phase Transition in Fullerene C$\text{}_{60}$
Autorzy:
Trybuła, Z.
Krupski, M.
Powiązania:
https://bibliotekanauki.pl/articles/2014286.pdf
Data publikacji:
2000-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Wz
62.50.+p
64.70.-p
77.22.Ch
Opis:
Phase transition in polycrystalline fullerene C$\text{}_{60}$ from fcc phase to a simple cubic phase sc induced by hydrostatic pressure up to 0.5GPa was studied by dielectric method. Pressure coefficient dT$\text{}_{c}$/dp=144±8 K/GPa was determined. This value is consistent with pressure coefficients obtained with other experimental techniques.
Źródło:
Acta Physica Polonica A; 2000, 98, 4; 389-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Temperature on the Magneto-Dielectrics Effect of Oil-Based Ferrofluid
Autorzy:
Kúdelčík, J.
Hardoň, Š.
Bury, P.
Timko, M.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1030417.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.65.Cb
77.22.Gm
77.22.Ch
Opis:
The effect of temperature on the magneto-dielectrics behavior was studied by dielectric spectroscopy in the transformer oil-based ferrofluid with magnetic nanoparticles upon the effect of an external magnetic field. The frequency dependence of complex permittivity and dissipation factor were measured within the frequency range from 1 mHz to 10 kHz at different temperatures by a capacitance method. The dielectrics parameters were measured as a function of the external magnetic field in the range of 0-200 mT, parallel to the direction of the electric field as a function of temperature in the range of 15-35°C. The interaction between magnetic field and magnetic moments of nanoparticles led to the aggregation of magnetic nanoparticles to new structures which had influence on dielectric parameters. The dependence of these parameters at constant magnetic field on angle between the direction of the electric and magnetic fields (anisotropy) has been measured, too.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 483-485
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 34

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