Search results for "Composite"
showing 10 items of 4584 documents
BST ceramics: Effect of attrition milling on dielectric properties
2004
Abstract The effect of grain size on the dielectric properties of Ba0.6Sr0.4TiO3 (BST) ceramics is investigated. Attrition milling is chosen to obtain nanometre particle size from micrometre particle size powders. Fine grained ceramics are obtained by hot uniaxial pressing (HUP). Additionally, the present study is focused on the effect of the nature of milling balls on loss tangent and permittivity. For that, three kinds of balls are tested: calcia, yttria or ceria stabilised zirconia balls. The properties of these samples are evaluated in the range of MHz. The balls induce an involuntary doping of powders which modifies the dielectric properties, especially the Curie temperature and loss t…
Dielectric properties and partial discharge endurance of polypropylene-silica nanocomposite
2010
This paper presents the results of the dielectric properties and partial discharge endurance measurements conducted on polypropylene (PP)-silica nanocomposite. The material compounds were analyzed with micro-Raman spectroscopy, X-ray tomography and transmission electron microscopy (TEM). ac and dc breakdown strength of the materials was measured. Dielectric response, capacitance and loss factor of the film samples were measured as a function of temperature and frequency. Partial discharge (PD) endurance of the reference PP and PP Silica nanocomposite was studied as a function of ac voltage. Material surfaces were analyzed after PD stress with optical microscopy. All dielectric measurements …
Effect of a filler on the dielectric properties of an epoxy resin
1983
The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
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.
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.…
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 …
Processing, basic characterization and standard dielectric measurements on PLZTx/65/35 (4 ≤x≤ 11) ceramics
2014
The influence of external stress (0–800 bar) on the dielectric properties of lead lanthanum zirconium titanate (PLZT) x/65/35 (4 ≤ x ≤ 11) ceramics was investigated. Applying uniaxial pressure leads to a change in the peak intensity of the electric permittivity (ϵ), in its frequency dispersion as well as in the dielectric hysteresis. The peak intensity of ϵ becomes broader and shifts to lower temperatures for PLZT x/65/35 with x = 4, 7, 9.75 and 11, with increasing pressure, on heating. It was concluded that applying uniaxial pressure induces an increase of Tm, and thus has a similar effect as the increase of the Ti ion concentration in the lead zirconium titanate (PZT) system. Results base…
Dielectric spectroscopy analysis of EVA-silicate nanocomposite insulating materials
2005
Nanocomposite materials show promising results for applications as electrical insulation. Among several materials presently under investigation, previous works indicate that polypropylene and ethylene-vinilacetate filled by nanosilicates present lower content of space charge and higher electric strength. However, efforts are needed to explain nanocomposite behaviour and characterize their electrical, thermal and mechanical properties. In this paper, the results of broad-band dielectric spectroscopy performed on ethylene-vinylacetate copolymer filled by layered micro and nanosized silicates are reported. The nanofillers consist of montmorillonite and fluorohectorite, that is, natural and syn…
Structural and Dielectric Properties of (Na0.5Bi0.5)0.70Ba0.30TiO3 Ceramics.
2003
Abstract A (Na0.5Bi0.5)0.70Ba0.30TiO3 ceramic has been studied by X-ray diffraction and by measurements of dielectric and ferroelectric properties between room temperature and 450 °C. A sharp increase in the electric permittivity and dielectric loss near 200 °C has been observed. This sharp increase in dielectric responses indicates a transformation between normal and relaxor ferroelectric states. It is found that polar regions can exist at higher temperatures. The X-ray diffraction study shows that the transformation corresponds to the first order phase transition from tetragonal to cubic. The use of the (Na0.5Bi0.5)0.70Ba0.30TiO3 ceramic for device application has also been indicated.