Search

A comparative analysis of five different methods was made to determine which is best for evaluating the elastic, dielectric and piezoelectric constants of four piezoelectric materials. These materials are a polyvinylidene fluoride, lead zirconate titanate/epoxy 1-3 composite, vinylidene-trifluoroethylene copolymers and lead metaniobate ceramic. Results show that the 'Piezoelectric Resonance Analysis Program' method outperform the Institute of Electrical and Engineers Standard 176, nonlinear regression method and methods of Smits and Sheritt et al.

Er/Pr-doped K0.5Na0.5NbO3 ceramics have been fabricated and the effects of Pr3+ on their photoluminescence properties have been investigated systematically. The visible upconversion emissions, near-infrared and mid-infrared downconversion emissions of Er3+ ions under the excitation of 980 nm have been studied in detail. The effects of Pr3+ on PL properties and energy-transfer processes have also been elucidated. By selecting an appropriate excitation source, simultaneous visible downconversion emissions of Er3+ and Pr3+ ions can be realized, and the emission colors of the ceramics can be tuned via the concentration of Pr3+ ions in a wide range from yellowish green to yellow. Our results also reveal that the photoluminescence emissions of the ceramics can be enhanced by the alignment of polarization of the ferroelectric host. [ABSTRACT FROM AUTHOR]

0.91K0.47Na0.47Li0.06NbO3-0.09NaSbO3 lead-free piezoelectric ceramics were prepared at 1000°C using a sintering aid comprising of Cu and Ba in a molar ratio of 71.5/28.5. A dense structure with a high density of 4.43 g/cm3 was obtained for the ceramic added with 2.5 wt% of the sintering aid. Probably due to the smaller grains and doping of Cu2+, the piezoelectric coefficient and dielectric loss were reduced to 120 pC/N and 1.0%, respectively. The ceramics were then fabricated into vibratory gyro sensors of dimensions 0.6 mm × 0.6 mm × 4 mm; and good sensitivity (~0.7 mV/dps) was obtained in the range of −360 to 360 dps. [ABSTRACT FROM AUTHOR]

Lead-free ceramics (1- x)NaNbO3- xLiTaO3 were synthesized by an ordinary solid-state reaction method. Rietveld analysis reveals that the crystal structure changes from one orthorhombic phase with Pbcm space group to another orthorhombic phase with P2221 space group when increasing x. The morphotropic phase boundary between two different orthorhombic symmetries is formed at 0.14 < x < 0.18. Excess LiTaO3 causes an abnormal grain growth behavior. The pure NaNbO3 presents four current peaks in the I- E loop, indicating electric-field-induced transitions. A low LiTaO3 doping induces ferroelectricity in the initially antiferroelectric (AFE) NaNbO3. Enhanced ferroelectricity is obtained at x = 0.02-0.12. The addition of LiTaO3 makes the ceramics undergo a transition from an antiferroelectricity dominant to a ferroelectricity dominant phase state. The optimum d33, kp, Qm, and Pr values of 46 pC/N, 18.3%, 1333, and 27.1 μC cm−2 are obtained when x equals 0.12, and the ceramic exhibits good temperature stability because of its high TC. [ABSTRACT FROM AUTHOR]

A study was conducted to analyze a novel process for preparing lead zirconate titanate (PZT)/poly(vinylidene fluoride-trifluoroethylene) 1-3 composites supporting piezoelectrically active phases. Sintered PZT rods were inserted into a prepoled copolymer matrix. The dipoles in the two phases were aligned in either the same or opposite directions. Results indicated that bandwidth is improved when the phases are poled in the same direction and the resonance peaks related to the H- and T-modes overlap.

Transparent lead-free electro-optic (EO) ceramics ( K0.5 Na0.5) 0.9 Li0.1 Nb0.9 Bi0.1 O3 have been fabricated by pressureless sintering. The ceramics have a fine-grained structure and cubic-like symmetry. The comodification with Li and Bi induces a diffuse phase transition, causing the ceramics become relaxor-like and contain polar nanoregions. Our results reveal that excess Bi2 O3 can further enhance the changes in the crystal structure and dielectric behavior of the ceramics, causing them become more cubic-like and more relaxor-like, respectively. These can reduce the light scattering arisen from birefringence and domain walls, and thus improving the optical properties. For the ceramics added with 4 and 6 mol% excess Bi2 O3, the optical transmittance reaches a high value of 60%-70% in the near-infrared region. The ceramics also exhibits a good linear EO response, giving an effective EO coefficient of 30-40 pm/V. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a contactless power charger for a functional jacket. The contactless power conversion, using the contactless power transformer, is examined. The primary and secondary sides of the transformer are separated by a large air gap, and hence, the power transfer can be obtained without physical contact. The characteristics of the gapped transformer and the compensation methodology on both the primary side and secondary side, are investigated in detail. The contactless power converter using phase-locked loop control is presented. Experiments and results are disclosed. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics (Na1− xK x)(Nb1− ySb y)O3+ z mol% MnO2 have been prepared by a conventional solid-state sintering technique. Our results reveal that Sb5+ diffuses into the K0.5Na0.5NbO3 lattices to form a solid solution with a single-phase orthorhombic perovskite structure. The partial substitution of Sb5+ for B-site ion Nb5+ decreases the paraelectric cubic-ferroelectric tetragonal phase transition ( Tc) and the ferroelectric tetragonal-ferroelectric orthorhombic phase transition ( TO–F), and retains strong ferroelectricity. A small amount of MnO2 is enough to improve the densification of the ceramics. The co-effects of MnO2 doping and Sb substitution lead to significant improvements in ferroelectric and piezoelectric properties. The ceramics with x=0.45–0.525, y=0.06–0.08, and z=0.5–1 exhibit excellent ferroelectric and piezoelectric properties: d33=163–204 pC/N, kP=0.47–0.51, kt=0.46–0.52, ℇ=640–1053, tan δ=1.3–3.0%, Pr=18.1–22.6 μC/cm2, Ec=0.72–0.98 kV/mm, and TC=269°–314°C. [ABSTRACT FROM AUTHOR]

Evaluates the material parameters of piezoelectric materials namely elastic, dielectric and the piezoelectric constants of four piezoelectric materials. Methods used in evaluating the materials; Frequency dependence of the material parameters; Conclusions.

Well-developed, dense and fine-grained MgO–(Ba0.6Sr0.4)TiO3 with 40wt% MgO content (denoted as BST–MgO) bulk ceramics were fabricated by high-energy ball mechanochemical technique using a hybrid processing. Based on this technique, the fabrication temperature was as low as 1200°C i.e., 200°C lower than that required by using conventional solid-state process. At the same time, dense, homogeneous and crack-free ceramic–ceramic 0–3 nanocomposite BST–MgO thick film was obtained at 700°C using the spin-coating method. At 10kHz and room temperature, the BST–MgO bulk ceramics exhibited a moderate dielectric constant of about 500 and low loss tangent of less than 0.005; while for the nanocomposite thick films, the dielectric constant and loss tangent were about 140 and less than 0.03 (at 100kHz) respectively. In addition, both the bulk ceramics and thick film show a broad and diffused phase transition. The dielectric room-temperature tunabilities measured at 100kHz were found to be 4% at 1.5kV/mm for the bulk ceramic, and 17% at 10kV/mm for nanocomposite thick film. [ABSTRACT FROM AUTHOR]

Abstract: Bismuth-modified potassium sodium niobate K0.48Na0.52Nb1−x Bi x O3 (x =0.05–0.15) transparent lead-free ceramics were fabricated by a hot-pressing method. Both hot-pressing conditions (pressure, temperature and duration) and Bi-content were found to have strong influences on the density, transparency, electro-optical coefficient, and electrical properties of the ceramics. Under the typical hot-pressing conditions of 1060°C for 5h at 5.5MPa, the optimum Bi-content was found at 7.5at.% in the system under study. These ceramics display good optical transmission in the visible and particularly in the infrared regions. For visible light, the highest transmission value of a polished 0.5-mm thick plates is about 60% at a wavelength of 800nm; while for infrared, the transmission value is about 80% at 4000nm. The effective linear electro-optic coefficient of the ceramics was found to be 42pVm−1. The dielectric permittivity and loss tangent of the KNNB (x =0.075) ceramics were found to be 716 and 0.031 at room temperature. [Copyright &y& Elsevier]