Home About us Contact
|
Home About us Contact | ||
|
|
||
Piezoelectric Constant (piezoelectric + constant)
Selected AbstractsPiezoelectric and Electric-Field-Induced Properties of a Ferroelectric Bent-Core Liquid CrystalADVANCED MATERIALS, Issue 37 2009Antal Jákli A new adamantane bent-core liquid crystal exhibiting a metastable ferroelectric phase with large polarization is synthesized and characterized. The material shows reversible switching between a birefringent (opaque) and an optically isotropic (clear) state. In the clear state, the observed piezoelectric constant is comparable to those of commercial solid-state piezotransducers. [source] Hydrothermal Synthesis and Spark Plasma Sintering of (K, Na)NbO3 Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Nan Liu A facile hydrothermal route was adopted for synthesis of lead-free piezoceramics (K, Na)NbO3 powders. The influences of temperature and KOH/NaOH concentration on the resultant powders were investigated. Although two similar perovskite phases appeared when K/Na ratio tended toward 1:1, the two-phase coexistence tendency was weakened by increasing hydrothermal reaction temperature, and consequently only one phase could be obtained after spark plasma sintering. Reasonably good ferroelectric and piezoelectric properties were obtained for the samples after postannealing, whose piezoelectric constant (d33) reached 135 pC/N. The optimal remnant polarization (Pr) and mechanical quality factor (Qm) were 26.2 ,C/cm2 and 164, respectively, which were both twice as much as those of the samples using powders prepared from solid-state reaction. [source] Effect of A Site Substitution on the Properties of CaBi2Nb2O9 Ferroelectric CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Xiaodong Zhang The effect of A-site substitution on the piezoelectric coefficient, high-temperature dc resistivity, and thermal depoling behavior of Aurivillius phase CaBi2Nb2O9 ferroelectric ceramics was investigated. Ceramics with the general formula of Ca1,xMxBi2Nb2O9, where M=Na, (Na,Ce), (Na,La), and La, were prepared by conventional solid-state sintering. All the ceramics were single-phase ferroelectrics with high Curie points (,900°C). The doped ceramics, Ca0.9Na0.1Bi2Nb2O9, Ca0.9(NaLa)0.1Bi2Nb2O9, Ca0.95La0.05Bi2Nb2O9, and Ca0.9La0.1Bi2Nb2O9, had improved resistance to thermal depoling compared with Ca2Bi2Nb2O9 and were stable up to 800°C. The donor dopants increased the dc electrical resistivity, while the acceptor dopants decreased it. The donor-doped Ca0.95La0.05Bi2Nb2O9 had a higher piezoelectric constant (d33=12.8 pC/N) compared with CaBi2Nb2O9 (d33=5.8 pC/N), and its electrical resistivity was higher than 106,·cm at 600°C. These properties suggest that doped CaBi2Nb2O9 ceramics might be good candidates for high-temperature piezoelectric applications. [source] Enhancing Electrical Properties in NBT,KBT Lead-Free Piezoelectric Ceramics by Optimizing Sintering TemperatureJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008Ya-Ru Zhang Conventional sintering of (Na1,xKx)0.5Bi0.5TiO3 (abbreviated as NKBTx, x=18,22 mol%) lead-free piezoelectric ceramics was investigated to clarify the optimal sintering temperature for densification and electrical properties. Both sintered density and electrical properties were sensitive to sintering temperature; particularly, the piezoelectric properties deteriorated when the ceramics were sintered above the optimum temperature. The NKBT20 and NKBT22 ceramics synthesized at 1110°,1170°C showed a phase transition from tetragonal to rhombohedral symmetry, which was similar to the morphotropic phase boundary (MPB). Because of such MPB-like behavior, the highest piezoelectric constant (d33) of about 192 pC/N with a high electromechanical coupling factor (kp) of about 32% were obtained in the NKBT22 ceramics sintered at 1150°C. [source] Structural and Electrical Properties of Er2O3 -Doped Na1/2Bi1/2TiO3 Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Mengjia Wu Sodium bismuth titanates Na1/2Bi1/2TiO3 (NBT) doped with 0,3 wt% Er2O3 were prepared by the conventional solid-state reaction method. The X-ray diffraction results revealed that the sintered Er-doped NBT ceramics exhibited a pure perovskite structure with Er3+ concentrations ranging from 0 to 1 wt%. At a low Er2O3 concentration, the Er-doped NBT ceramics showed enhanced electrical properties with dielectric constant ,33T/,0=636, a low dielectric dissipation factor (tan ,=3.3%), a low coercive field (Ec=4.56 kV/mm), and a high piezoelectric constant (d33=75 pC/N). The relationship between the composition and properties of Er-doped NBT ceramics has been discussed. [source] Microstructures and Piezoelectric Properties in the Li2O-Excess 0.95(Na0.5K0.5)NbO3,0.05LiTaO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007Min-Soo Kim As a candidate for lead-free piezoelectric materials, Li2O-excess 0.95(Na0.5K0.5)NbO3,0.05LiTaO3 (NKN,5LT) ceramics were developed by a conventional sintering process. The sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN,5LT ceramics was observed with varying Li2O content. This grain-growth behavior was explained in terms of interface reaction-controlled nucleation and growth. In the 1 mol% Li2O excess NKN,5LT samples sintered at 1000°C for 4 h in air, the electromechanical coupling factor and the piezoelectric constant of NKN,5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively. [source] Ferroelectric and Piezoelectric Properties of Na1,xBaxNb1,xTixO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006J. T. Zeng Piezoelectric ceramics Na1,xBaxNb1,xTixO3 with low BaTiO3 concentrations x have been prepared by the solid-state reaction method, and their ferroelectric and piezoelectric properties have been studied. The ceramics are classic ferroelectrics when x,0.10, and the ferroelectric,paraelectric phase transition becomes diffusive when x,0.15. A low doping level of BaTiO3 changes the NaNbO3 ceramics from antiferroelectric to ferroelectric. With the increase in BaTiO3 doping level, the Curie temperature of ceramics decreases linearly and the remnant polarization and coercive field also decrease, while their dielectric constant increases. Na0.9Ba0.1Nb0.9Ti0.1O3 ceramics show the largest piezoelectric constant d33 (147 pC/N) and good sinterability, suggesting that it is a good candidate for lead-free piezoelectric ceramics. [source] Microstructure, dielectric, and piezoelectric properties of 0.38Bi(Gax Sc1,x)O3,0.62PbTiO3 high temperature piezoelectric ceramicsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1 2008Yihang Jiang Abstract 0.38Bi(Gax Sc1,x)O3,0.62PbTiO3 (BGSPTx) ceramics have been prepared by using the conventional mixed oxide method. X-ray diffraction analysis revealed that BGSPTx has a pure perovskite structure, and the crystal symmetry of BGSPTx changed from rhombohedral to tetragonal with increasing Ga content (x). The Curie temperature (TC) of BGSPTx ceramics is in the range of 448,467 °C for different x. The ferroelectric phase transition of BGSPTx was found to be of the first order type according to the Curie,Weiss law. For x = 0.125, BGSPTx ceramics show enhanced piezoelectric properties: piezoelectric constant d33 = 420 pC/N and d31 = ,142 pC/N, planar and thickness electromechanical coupling factors kp = 56.27% and kt = 56.00%, respectively. The high- TC of BGSPTx coupled with its excellent piezoelectric properties suggests those future high-temperature applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ferroelectric, piezoelectric, pyroelectric and Raman spectroscopy studies on BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramicPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2008Z. Abdelkafi Abstract The hysteresis, piezoelectric and pyroelectric properties were measured in the temperature range near the ferroelectric,paraelectric phase transition. The BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramic exhibits typical ferroelectric P ,E hysteresis behavior with a remanant polarization, Pr, of about 7.52 ,C/cm2 detected at 155 K. The electromechanical properties of this composition were measured using the resonance method. The ceramic provides high piezoelectric performance at the temperature of transition (Tmax = 216 K): the piezoelectric constant is d31 = 140 pC/N and the electromechanical coupling factor was kP = 22%. The pyroelectric study confirms the dielectric and ferroelectric measurements. The pyroelectric coefficient is about 125 nC/cm2 K at Tmax. Raman spectra of BaTi0.9(Fe1/2Nb1/2)0.1O3 ceramic were taken at various temperatures and measured over the wave number range from 150 to 1300 cm,1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of electric control catheter and tweezers for thrombosis sample in blood vessels using piezoelectric polymeric fibers,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2006Yoshiro Tajitsu Abstract Poly- L -lactic acid (PLLA) has recently attracted attention as a polymer which exhibits a high shear piezoelectric constant. In this study, it was possible to control the piezoelectric motion of the PLLA fiber by applying d.c. voltage and a.c. voltage similar to a piezoelectric actuator. Then, on the basis of the experimental results, an electric control catheter and tweezers, using PLLA fibers (PLLA fiber catheter/tweezers) was developed. In the demonstration, it was assumed that thrombosis in blood vessels occurred and it was attempted to remove the thrombosis from the affected area using the PLLA fiber catheter and tweezers. This very delicate operation was attempted under a microscope. Using the PLLA fiber catheter and tweezers, the affected area was excised. A video movie of the test demonstration was recorded using a CCD video camera. All stages proceeded well in this study. Copyright © 2006 John Wiley & Sons, Ltd. [source] Investigations of the bond-selective response in a piezoelectric Li2SO4·H2O crystal to an applied external electric fieldACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2009O. Schmidt Piezoelectric lithium sulfate monohydrate, Li2SO4·H2O, was analyzed with respect to the relationship between the static structural properties of the crystal and its response to an external electric field. The static electron density was determined via standard low-temperature X-ray data collection at 90,(5) K using an Enraf,Nonius CAD-4 diffractometer, Mo K, radiation and multipole model refinement. Then a synchrotron-radiation experiment using the D3 beamline at HASYLAB was conducted in order to investigate the structural deformations in Li2SO4·H2O caused by an applied external electric field. In particular, the shifts of Bragg-peak positions induced by the electric field were measured and the piezoelectric constants d211, d222, d233 and d213 of Li2SO4·H2O were obtained from the shifts. With the same experimental setup the variations of more than 100 Bragg intensities were measured under an applied electric field. The data were used to refine the corresponding displacements of individual atoms within the unit cell. The distortions of the cation,anion bond lengths in the LiO4, LiO3(H2O) and SO4 tetrahedra were evaluated and then analyzed in terms of the electron-density-related properties of the Li,O and S,O bonds. The two lithium structural units were found to be strongly deformed by the applied electric field, while the SO4 tetrahedron changed less. This is in agreement with the low bond strength of the Li,O bonds. [source] | |||||||||||||