Search results for "Permittivity"
showing 10 items of 176 documents
Structure and dielectric properties of Na<inf>1/2</inf>Bi<inf>1/2</inf>TiO<inf>3</inf>-BaTiO<inf>3</inf&…
2012
Dielectric properties, polarization and x-ray diffraction are studied for (1−x)Na 1/2 Bi 1/2 TiO 3 -xBaTiO 3 solid solutions in a concentration range above the morphotropic phase boundary. It is showed that all the studied compositions have tetragonal structure with maximal tetragonality slightly above the morphotropic phase boundary. Ferroelectric relaxor behavior is observed in a wide concentration range of BaTiO 3 . Stability of the relaxor state decreases with increasing BaTiO 3 concentration, but only for compositions with low Na 1/2 Bi 1/2 TiO 3 content the normal ferroelectric-paraelectric phase transition, which is characteristic to pure BaTiO 3 , occurs. Mechanisms, which influence…
Dielectric characterization of biocompatible hydrogels for application to Epidermal RFID devices
2015
Functionalized skin-like membranes are currently under investigation for the design of a new class of Epidermal Electronics devices for sensing and healing applications. The dynamic response of epidermal antennas in presence of absorption and release of fluids is a key-point to design RFID radio-sensors and actuators. This paper addresses the characterization of the dielectric property of PVA-based biocompatible hydrogel membranes in the UHF RFID band by means of a modified ring resonator. Samples having different compositions are measured in the dry state as well as when exposed to a progressive release of body fluids emulating perspirations or wound exudates. It was found that the permitt…
Relation of Dielectric Permittivity and Electric Field Dependence of Polarization in Some Relaxors with Perovskite Structure
2011
The dielectric nonlinearity is studied in ferroelectric relaxors 0.92PbMg1/3 Nb2/3O3-0.08PbTiO3, 0.4Na1/2Bi1/2TiO3-0.5SrTiO3-0.1PbTiO3 and Pb0.9075La0.0925 (Zr0.65Ti0.35)0.9775O3. It is shown that above the temperature of dielectric permittivity maximum nonlinearity of dielectric permittivity corresponds to electric field dependence of polarization. The influence of electric field on distribution of relaxation times is studied below the maximum of dielectric permittivity. The role of internal bias field in Pb0.9075La0.0925(Zr0.65Ti0.35)0.9775O3 ceramics is discussed.
Development and characterization of xyloglucan-poly(vinyl alcohol) hydrogel membrane for Wireless Smart wound dressings
2018
Abstract Hydrogel-based smart wound dressings that combine the traditional favourable properties of hydrogels as skin care materials with sensing functions of relevant biological parameters for the remote monitoring of wound healing are under development. In particular, lightweight, ultra-high frequency radiofrequency identification (UHF RFID) sensor are adjoined to xyloglucan-poly(vinyl alcohol) hydrogel films to battery-less monitor moisture level of the bandage in contact with the skin, as well as wireless transmit the measured data to an off-body reader. This study investigates the swelling behavior of the hydrogels in contact with simulated biological fluids, and the modification of th…
ZrTiO4 materials obtained by spark plasma reaction-sintering
2014
Zirconium titanate (ZrTiO4), have many attractive properties such as high resistivity, high dielectric constant, high permittivity at microwave frequencies and excellent temperature stability for microwave properties. Zirconium titanate dense materials are proposed for many structural applications, but fully reacted and completely dense pieces are difficult to obtain by conventional routes. In this work, fully dense zirconium titanate materials (∼98%) were obtained at lower temperatures (1300-1400 C) and short processing time by non-conventional technique; spark plasma-reaction sintering (SPRS). Homogeneous and stable starting powders mixture with the adequate composition was prepared from …
INFLUENCE OF ZIRCONIUM ON STRUCTURAL, MICROSTRUCTURAL AND FERROELECTRIC PROPERTIES OF BaZr0.20Ti0.80O3 CERAMIC
2009
ABSTRACT Barium zirconium titanate BaZrxTi1-xO3 ceramics have been obtained by conventional method. The X-ray diffraction analysis showed that the BaZr0.20Ti0.80O3 crystallizes in the cubic structure. The lattice parameter a increases with temperature, at temperature ∼308 K a small deviation is observed. The performed EDS study revealed that the samples were perfectly sintered and that the material was chemically homogeneous. It contains a little glassy phase and the grains are well shaped. The zirconium content (20 mol%) in the examined solid solution caused downward shift of the temperature T m . The increase of the achieved permittivity values ϵm was observed as well.
Proton glass behavior and hopping conductivity in solid solutions of antiferroelectric betaine phosphate and ferroelectric betaine phosphite.
1991
Measurements of the dielectric permittivity are reported for solid solutions of antiferroelectric betaine phosphate and ferroelectric betaine phosphite at frequencies 10 −2 Hz T c the dielectric response is dominated by ac and dc conduction. The 40% sample exhibits pure relational behavior indicative of a transition into an orientational glass state
True Nanoferroics with the Properties Absent in Corresponding Bulk Samples
2013
The Chapter covers the theoretical and experimental approaches to the investigations of the physical properties, which are inherent in ferroics of nanosize and absent in corresponding bulk materials. Namely, the strong surface influence along with other effects of geometrical confinement generates number of physical effects, which do not occur in bulk ferroics samples. One example of such phenomena is room-temperature ferromagnetism in nanoparticles and thin films of undoped CeO2, HfO2, SnO2, Al2O3 and other nonmagnetic (in bulk samples) oxides. Theo other striking example is appearance of so-called spontaneous flexoeffects (i.e. flexoelectric, flexomagnetic, flexoelastic) in ferroic nanosa…
Dielectric polarization in PLZT X/65/35 and PbMg1/3Nb2/3O3at the diffuse phase transition
1992
Abstract The transformation of the hysteresis loops in PLZT x/65/35 in the region of diffuse phase transition is discussed in relation to the behaviour of dielectric permittivity. The Vogel-Fulcher type dielectric relaxation is used to describe the discussed phenomena.
Electrocaloric Effect in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3Solid Solutions
2012
Electrocaloric effect is studied in a group of triple solid solutions 0.4Na1/2Bi1/2TiO3-(0.6-y)SrTiO3-yPbTiO3. Contribution of electric field-induced phase transition in the total value of temperature change, caused by electric field, is evaluated. The highest value of electrocaloric effect is observed for composition 0.4Na1/2Bi1/2TiO3-0.4SrTiO3-0.2PbTiO3, in which the depolarization temperature, characteristic for relaxor ferroelectrics, merges with the temperature of maximum of dielectric permittivity. Applicability of thermodynamic description is discussed.