Search results for "Permittivity"
showing 10 items of 176 documents
Dielectric spectroscopy measurements of the sub-Tg relaxations in amorphous ethyl cellulose: A relaxation magnitude study
2005
Amorphous ethyl cellulose exhibits three secondary relaxations at temperatures below its glass transition. The fitted parameters that describe these processes and the comparison with other polysaccharides allow to ascribe the relaxations to lateral groups on one hand and to local main chain motion on the other hand. Their contributions to the dielectric constant overlap and induce a broad dielectric losses peak. The amplitude of one of these relaxations is found to decrease regularly with time. It is believed it comes from a gradual change of the polar groups chemical environment that constrains their motion.
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…
Radio and Microwave Spectroscopy of 0.2PMN-0.4PSN-0.4PZN Relaxor Ceramics
2005
Dielectric spectroscopy results of 0.2PbMg 1/3 Nb 2/3 O 3 -0.4PbSc 1/2 Nb 1/2 O 3 -0.4PbZn 1/3 Nb 2/3 O 3 ceramics are reported for 200 < T < 450 K and 20 Hz < v < 11 GHz. Dielectric constant is very high (more than 12000) in the vicinity of the peak. Anomalous broad dielectric relaxation has been observed near and below the temperature of the maximum permittivity, T m (at 1 kHz). The distribution of relaxation times have been calculated directly from the dielectric spectra. At higher temperatures than the maximum permittivity, T m the distribution of the relaxation times is symmetrically shaped (Cole-Cole function satisfactory describes the dielectric response). At lower temperatures, the …
Dielectric spectroscopy of an aligned liquid crystalline side chain polymer using high pressures
1995
Abstract The complex permittivity of a liquid crystalline side group polymer has been measured at pressure from ambient up to 300 MPa. The samples were initially not aligned, then planar and finally homeotropically aligned by the field of a 7.2 Tesla magnet. Temperatures ranged up to 130°C, and measurement frequencies from 5 Hz to 5 MHz. The equilibrium permittivity es has been interpreted in terms of an effective dipole moment μ. The frequency of maximum loss has been analysed in terms of enthalpy of activation and volume of activation for α and β relaxation processes.
Germanium modified BaTiO3as a promising electroceramics
2016
ABSTRACTThe polycrystalline sample of BaTi0.95Ge0.05O3 was prepared by solid-phase reaction using a conventional method. The morphology of investigated sample was characterised by scanning electron microscopy (SEM). The results allowed to determining the stoichiometry of the material and evaluate their microstructure. High quality samples were investigated, the grains are well shaped without of a glassy phase. The dielectric properties of the BaTi0.95Ge0.05O3 ceramics were determined. The results were compared with these ones obtained for pure BaTiO3. The obtained data indicated that the substitution of Ge+4 ions had an influence on the values of the real (ϵ′) and imaginary (ϵ″) parts of el…
Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties
2016
International audience; Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO2) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3–5.3 nm.…
Thermal and conductivity dependence of GaAs based acoustic biosensors
2016
GaAs BAW sensors using shear acoustic waves were developed for biological detection and quantification. The sensor consists of a 50–350µm thick membrane where thickness shear acoustic waves were produced with a lateral field excitation (LFE). The LFE electrode arrangement is located on one side of the membrane. The other side is dedicated for proteins or cells capture through a bio-functionalized interface formed on the GaAs surface. Sensitivity of this type of sensor had been evaluated by modeling to 0.1ng.Hz−1. Detection needs to be done in liquid environment with complex biological analytes such as blood or plasma. These analytes can inevitably induce temperature and surface charge varia…
Structural and in depth characterization of newly designed conducting/insulating TiN O /TiO2 multilayers obtained by one step LP-MOCVD growth
2001
Abstract TiNxOy/TiO2 multilayers have been grown by LP-MOCVD using titanium isopropoxide (TIP) precursor during the whole growth, but with an ammonia flow interrupted for the TiO2 layers. The one step growth process used to grow these structures allowed to stack the conducting and insulating layers without any growth breakdown. SIMS and TEM analyses showed the presence of an alternated insulating/conducting layers structure. Moreover, electrical measurements allowed to measure the dielectric part of insulating TiO2 stacked in these structures, whose permittivity was found to be about 80 for a MOS structure. Thus, such multilayers may lead to very promising applications in the microelectroni…
Influence of Compressive Stress on Dielectric and Ferroelectric Properties of the 0.9PbSc0.5Nb0.5O3-0.1PbLu0.5Nb0.5O3Ceramics
2014
0.9PbSc0.5Nb0.5O3-0.1PbLu0.5Nb0.5O3ceramics were prepared by a solid-state mixed-oxide technique. The phase formation and microstructure were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The influences of compressive stress (0 – 1500 bar) applied parallel to the electric field on the dielectric and ferroelectric properties of these ceramics were investigated. The results showed that the compressive stress had pronounced effects on these properties. With increasing pressure, the electric permittivity maximum decreases and shifts to higher temperature, thermal hysteresis, dielectric dispersion and polarization decrease. The obtained results were …
Setup for Characterization of the Non-Linear Electric Susceptibility in the Microwave Range Applied to a Glass Ceramic
2019
A resonator method exciting eigenresonances of three coupled cylindrical dielectric resonators allows characterizing the non-linear response of low loss and high permittivity materials at frequencies of about 1 GHz. To reach the necessary sensitivity for dielectric non-linearities, the setup ensures that the measured intermodulation can be ascribed to the material under test while all other intermodulation sources are excluded. Electric field amplitudes of several V/mm are obtained at an input power of 100 W. The setup was used to characterize the third order non-linear susceptibility of a glass ceramic.