Search results for "low frequency"

showing 10 items of 97 documents

Structure and dynamic dielectric behaviour of ferroelectric [NH2(CH3)2]3Sb2Br9(DMABA)

2000

The crystal structure of DMABA has been determined at 293 and 180 K. It crystallizes in the monoclinic P21/c space group. The structure was refined to R1 = 0.0466 for 1269 independent reflections at 293 K and R1 = 0.038 for 1728 reflections at 180 K. DMABA is isomorphous with the chlorine analogue, DMACA. Its anionic sublattice forms corrugated two-dimensional layers in the bc plane. There are two crystallographically independent, disordered dimethylammonium cations in the crystal structure. One of them occupies cavities inside the polyanionic layers; the other is located between the layers. The temperature dependence of lattice parameters has been determined between 100 and 290 K. The pres…

PermittivityCrystallographyPhase transitionChemistryLattice (order)General Materials ScienceCrystal structureDielectricLow frequencyCondensed Matter PhysicsFerroelectricityMonoclinic crystal systemJournal of Physics: Condensed Matter
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Dielectric Characterization of Fruit Nectars at Low RF Frequencies

2015

Dielectric properties of apple, apricot, peach, and pear nectars were studied in the frequency range from 15 kHz to 30 MHz and the temperature range from 25 to 60 degrees C. Both the relative dielectric constants and the dielectric loss factors decreased by increasing frequency and increased linearly with increasing temperature with values in the order 10(4)-10(2) and 10(5)-10(2), respectively. The power dissipation densities and the power penetration depths were found to increase linearly with temperature. Power dissipation densities remained essentially constant for all the samples while power penetration depths decreased significantly on increasing frequency. The dependence of each of th…

PermittivityMaterials scienceRF heatingSettore CHIM/10 - Chimica Degli AlimentiAnalytical chemistryPhysics::OpticsRelative permittivityDielectricLow frequencyAtmospheric temperature rangeDissipationFruit nectarPermittivityDielectric heatingdielectric constant dielectric loss dielectric spectroscopy fruits apple juice conduction fruit nectar RF heating.Dielectric constantDielectric lossFruit juiceDielectric loss factorLow frequencySettore CHIM/02 - Chimica FisicaFood ScienceInternational Journal of Food Properties
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Low frequency nonlinearity in layered ferroelectrics BaBi<inf>2</inf>Nb<inf>2</inf>O<inf>9</inf> and SrBi<inf&…

2010

The dielectric nonlinearity in layered ferroelectric ceramics of BaBi 2 Nb 2 O 9 and SrBi 2 Ta 2 O 9 is studied by analysing polarisation loops and measuring dielectric permittivity as a function of frequency. In case of BaBi 2 Nb 2 O 9 the system has a broad phase transition manifesting essential features of a slow relaxation of polarisation; in case of SrBi 2 Ta 2 O 9 the processes contributing to polarisation switching are driven by rearrangement of the domain structure.

PermittivityPhase transitionNonlinear systemMaterials scienceCondensed matter physicsFerroelectric ceramicsvisual_artRelaxation (NMR)Electronic engineeringvisual_art.visual_art_mediumCeramicDielectricLow frequency2010 10th IEEE International Conference on Solid Dielectrics
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Anomalous Broad Distribution of Relaxation Times in Mixed PMN-PSN Ceramics

2007

Dielectric permittivity of 0.8PMN-0.2PSN ceramic was measured in the frequency range from 20 Hz to 3 GHz. The typical ferroelectrics relaxor dielectric dispersion was observed. From the frequency dependence of complex dielectric permittivity, the distribution of relaxation times was calculated. The low frequency limit of the distribution of relaxation times diverges according to the Vogel–Fulcher law with the freezing temperature T f = 226 K which is lower than in PMN ceramics, obtained previously. The comparison of distributions of relaxation times between 0.8PMN-0.2PSN and pure PMN tends to the conclusion about smaller polar nano regions in 0.8PMN-0.2PSN ceramic.

PermittivityRange (particle radiation)Materials scienceCondensed matter physicsRelaxation (NMR)Low frequencyCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsNuclear magnetic resonancevisual_artNano-visual_art.visual_art_mediumPolarCeramicCole–Cole equationFerroelectrics
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Low and Infra-Low Frequency Measurements in Lead Titanate Solid Solutions

2006

The study of PSN-PT ferroelectric relaxor ceramics exhibiting extreme values of some physical parameters near the morphotropic phase boundary is reported. The results are discussed to account for the relaxor properties related to defects and disordering of the PSN-PT system.

Phase boundaryFerroelectric relaxorMaterials scienceMineralogyDielectricLow frequencyCondensed Matter PhysicsFerroelectricityAtomic and Molecular Physics and Opticschemistry.chemical_compoundchemistryvisual_artvisual_art.visual_art_mediumGeneral Materials ScienceCeramicLead titanateComposite materialSolid solutionSolid State Phenomena
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Pressure Dependence of the Low-Frequency Dielectric Constant in III-VI Semiconductors

1999

In this work we report on the pressure dependence of the low-frequency dielectric constant parallel to the c-axis (e∥) in GaS, GaSe, and InSe as obtained from direct capacitance measurements. A large increase of e∥ with pressure has been observed. The pressure change of the lattice polarizability along the c-axis is calculated in the framework of a rigid-ion model from the change of the angle of the anion–cation bond with respect to the layer plane, which results in a slight increase of the lattice contribution. Consequently, the pressure behaviour of e∥ is proposed to arise from the large increase of the electronic polarizability along the c-axis. This is explained through a decrease of th…

Phase transitionCondensed matter physicsChemistrybusiness.industryDielectricLow frequencyPressure dependenceCondensed Matter PhysicsCapacitanceElectronic Optical and Magnetic MaterialsSemiconductorPolarizabilityLattice (order)businessphysica status solidi (b)
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DIELECTRIC PROPERTIES OF LEAD-FREE [(1-x)(Na0.5Bi0.5)-xBa]Zr1−yTiyO3CERAMICS (x = 0.01, 0.06, 0.085, 0.09, 0.1 AND y = 0.96, 0.97)

2008

ABSTRACT Lead-free ceramics based on (Na0.5Bi0.5TiO3, NBT)-(Ba(Ti, Zr)O3, BTZ) were prepared by solid phase synthesis and hot pressing sintering process and their dielectric properties have been studied. The obtained results were compared with these for pure NBT. The obtained samples show pure perovskite structure. Low frequency (100 Hz-100 kHz) investigations reveal the diffuse phase transitions and relaxorlike behaviour. The obtained results are discussed in terms of inhomogeneity of ions distribution, their ferro- and antiferroactivity and internal stresses. The NBT-BTZ system is expected to be a new promising candidate for lead-free electronic ceramics.

Phase transitionMaterials scienceAnalytical chemistryMineralogySinteringDielectricLow frequencyCondensed Matter PhysicsHot pressingFerroelectricityElectronic Optical and Magnetic MaterialsIonControl and Systems Engineeringvisual_artMaterials ChemistryCeramics and Compositesvisual_art.visual_art_mediumCeramicElectrical and Electronic EngineeringIntegrated Ferroelectrics
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LEAD-FREE (Na0.5Bi0.5)1-xBaxTiO3 SINGLE CRYSTALS (0 ≤ x ≤ 0.05) AND THEIR DIELECTRIC AND PYROELECTRIC PROPERTIES

2009

ABSTRACT Lead-free single crystals of Na0.5Bi0.5TiO3-BaTiO3 (NBT-BT) system were prepared by Czochralski method and their dielectric and pyroelectric properties have been studied. The results were compared with these for pure NBT. The obtained samples show pure perovskite structure with rhombohedral symmetry at room temperature. Low frequency (100 Hz–100 kHz) investigations reveal the diffuse phase transitions. The obtained results are discussed in terms of local electric and strain fields caused by different ionic radius of (Na, Bi) and Ba ions. The NBT-BT system is expected to be a new promising candidate for lead-free electronic crystals.

Phase transitionMaterials scienceIonic radiusAnalytical chemistryDielectricLow frequencyCondensed Matter PhysicsFerroelectricityElectronic Optical and Magnetic MaterialsIonPyroelectricityCrystallographyControl and Systems EngineeringMaterials ChemistryCeramics and CompositesElectrical and Electronic EngineeringPyroelectric crystalIntegrated Ferroelectrics
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<title>Dielectric response to low and infra-low frequency in layered ferroelectrics</title>

2006

Features of dielectric response to frequencies in the 0.25.1000 Hz range in ceramic samples of BaBi2Nb2O9, Na0,5Bi8.5Ti2Nb4O27, Na0,5Bi8.5Ti2Ta4O27, and K0,5Bi8.5Ti2Nb4O27 compounds are reported. Considerable relaxation of e'(T) and e"(T) maximums has been observed at all frequencies in BaBi2Nb2O9. Na0,5Bi8.5Ti2Nb4O27 and Na0,5Bi8.5Ti2Ta4O27 are characterised by broad maximums on e'(T) at frequencies below 100 Hz and a weak anomaly in K0,5Bi8.5Ti2Nb4O27 at temperatures well below the paraelectric phase transition. Increasing values of e' are observed at low temperatures in compounds containing sodium. The observed features of dielectric response are explained by largescale charge fluctuatio…

Phase transitionRange (particle radiation)Materials scienceCondensed matter physicsNiobiumMineralogychemistry.chemical_elementDielectricLow frequencychemistryvisual_artvisual_art.visual_art_mediumRelaxation (physics)CeramicAnomaly (physics)SPIE Proceedings
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Experimental and numerical study of noise effects in a FitzHugh–Nagumo system driven by a biharmonic signal

2013

Abstract Using a nonlinear circuit ruled by the FitzHugh–Nagumo equations, we experimentally investigate the combined effect of noise and a biharmonic driving of respective high and low frequency F and f. Without noise, we show that the response of the circuit to the low frequency can be maximized for a critical amplitude B∗ of the high frequency via the effect of Vibrational Resonance (V.R.). We report that under certain conditions on the biharmonic stimulus, white noise can induce V.R. The effects of colored noise on V.R. are also discussed by considering an Ornstein–Uhlenbeck process. All experimental results are confirmed by numerical analysis of the system response.

PhysicsArtificial neural networkGeneral MathematicsApplied MathematicsNumerical analysisAcousticsMathematical analysisGeneral Physics and AstronomyStatistical and Nonlinear PhysicsWhite noiseLow frequencyNonlinear systemAmplitudeColors of noiseBiharmonic equationChaos, Solitons & Fractals
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