Search results for "Dielectric loss"
showing 10 items of 59 documents
Dielectric study of orientational disorder in (CO2)1−x(N2O)xmixed crystals
1990
The dipolar relaxation dynamics of solid solutions of carbon dioxide and nitrous oxide has been investigated using dielectric spectroscopy. The temperature dependence of the relaxation rate reveals an ideal Arrhenius behavior for all concentrations, with energy barriers which scale linearly between the two pure compounds. The attempt frequencies are anomalously high. The distribution of relaxation times due to the static random fields as introduced by the substitutional impurity molecules is almost negligible. The melting temperature is determined by a critical relaxation rate of 40 kHz.
Dielectric Spectroscopy of Recycled Polylactide
2014
The effects of multiple mechanical recycling on amorphous polylactide (PLA) were simulated by means of five successive injection-grinding cycles. The influence of the induced thermo-mechanical degradation on the dielectric properties of PLA was analysed. The relaxation spectra were studied in terms of the complex dielectric permittivity (ε0 and ε00) and the dielectric loss tangent, tg(d) in the frequency range from 102 to 107 Hz over the temperature interval from 0 C to 140 C. It was possible to distinguish two relaxations zones, one at low temperatures and high frequencies (b relaxation) and another at higher temperatures and lower frequencies (a relaxation). The individual relaxations wer…
Single particle jumps and correlated ionic motions in glass-ceramics
1993
Using impedance spectroscopy, the ion transport in poorly Li-conducting aluminosilicate glass ceramics and their precursor glasses has been measured for temperatures 50 K < T < 550 K and covering a frequency range of more than 14 decades from 10 mHz up to 3 THz. In addition to the familiar cooperative ionic motion dominating at high temperatures, for the first time dielectric relaxation due to elementary hopping processes is observed well below room temperature.
Determination of the apparent activation energy of dielectric relaxation phenomena by means of the representation of ε” as a function of T at constan…
1984
Abstract The main purpose of this work is to justify the use of the positions of the maxima of e” versus T curves when calculating the apparent activation energy in secondary dielectric relaxations or in the relaxation associated with the glass transition. To exemplify this, phenomenological models as well as experimental results for methacrylic polymers are discussed.
FILTER RESPONSE OF RESONANT WAVEGUIDE DIELECTRIC GRATINGS AT PLANE-WAVE CONICAL INCIDENCE
2009
An accurate and efficient formulation is presented for the electromagnetic analysis of dielectric waveguide gratings under plane-wave conical incidence. An arbitrary number of dielectric bars can be placed inside each one-dimension periodic cell, including the effect of dielectric losses. The reflectance of a dielectric waveguide grating under conical incidence is compared with theoretical results presented by other authors, finding a very good agreement. A single-layer reflection filter has been designed centered at λ0=1.5 μm whose spectral and angular responses are shown. For this structure, the effect of the asymmetry of the distribution of the refraction index in the reflectance has bee…
Dielectric and dynamic-mechanical behaviour of ethylene-vinyl alcohol copolymers
1983
Abstract Dynamic-mechanical and dielectric measurements on ethylene-vinyl alcohol copolymers with two different vinyl alcohol contents and, for comparison on polyvinylalcohol and low density polyethylene, have been carried out in order to clarify the nature of the relaxation peak. The relaxation peak observable in the dielectric loss curves of the copolymers has been assigned to the interfacial polarization, MWS type, occurring between hydrogen bonded hydroxyl groups and the apolar polyethylene segments. The shoulder also present in the e″-T curves of the copolymers seems to correspond to the glass transition peak which is hidden since the dielectric loss curve increases quickly because of …
Improve the dielectric properties of PrSrNi0.8Mn0.2O4 compounds by longer mechanical milling
2018
Abstract Structural and dielectric properties of PrSrNi 0.8 Mn 0.2 O 4 ceramics elaborated by a rapid method combining mechanical milling and heat treatment were studied for the first time. The raw materials are milled at different times ( t mil = 0, 5, 10, 20 and 30 h) and annealed at 1300 °C for 8 h to produce a revealed PrSrNi 0.8 Mn 0.2 O 4 single phase, exhibiting tetragonal structure with space group I 4/ mmm . This result was confirmed by using the TEM/ED pattern for sample milled at 30 h using the [001] orientation. The corresponding lattice images show a well-ordered compound, indicating the absence of stacking faults and the growth of the crystallites. Giant dielectric response …
Quantum paraelectric and induced ferroelectric states in
1996
Nominally pure has been studied by dielectric spectroscopy using small (linear regime) as well as large electrical fields (non-linear regime) up to . In addition measurements of the specific heat and its field-dependent contribution have been carried out. The field dependence of the dielectric constant and the specific heat can be well described by the transverse Ising Hamiltonian including tunnelling and external field terms. It gives evidence for the existence of polar clusters at low temperatures which are supposed to be associated with the quantum paraelectric state below in accord with recent free-energy calculations. The low-field third-harmonic susceptibility which measures the polar…
Properties of Ni–Zn ferrite thin films deposited using spray pyrolysis
2012
Abstract Nanocrystalline, homogeneous spinel Ni 1 − x Zn x Fe 2 O 4 thin films were deposited on glass substrates by using spray pyrolysis of metal nitrate aqueous solutions. The thickness of deposited films was below 500 nm, but crystallite size was under 30 nm. It has been shown that the DC resistivity, dielectric loss and optical band gap of deposited films are influenced by the zinc content. High DC resistivity and low dielectric losses of thin Ni 1 − x Zn x Fe 2 O 4 films are explained by mixed n-p conductivity and nanograin structure of spray pyrolysis deposited coatings which are changing with the ratio of Ni/Zn.
Effects of 3rd-harmonic voltage content on dielectric losses of solid insulating materials
1981
Dielectric losses in solid insulating materials subjected to voltages containing 3rd harmonics are studied. By simple theoretical analysis, some curves are obtained showing the behaviour of the ratio between the dielectric losses in the distorted steady state and in a reference sinusoidal steady state, against 3rd-harmonic content. The reference sinusoidal voltage amplitudes were selected in two different ways; namely, such as to have either peak value or effective value equal to those of distorted waveform.Separate effects of harmonic content and of effective value of the applied voltage are shown through the correspondence of every 3rd-harmonic phase angle. Percentage differences between …