1,721,465 research outputs found
Strong and anisotropic magnetoelectricity in composites of magnetostrictive Ni and solid-state grown lead-free piezoelectric BZT–BCT single crystals
No full textAimed at developing lead-free magnetoelectric (ME) composites with performances as good as lead (Pb)-based ones, this study employed (001) and (011) oriented 82BaTiO3-10BaZrO3-8CaTiO3 (BZT–BCT) piezoelectric single crystals, fabricated by the cost-effective solid-state single crystal growth (SSCG) method, in combination with inexpensive, magnetostrictive base metal Nickel (Ni). The off-resonance, direct ME coupling in the prepared Ni/BZT–BCT/Ni laminate composites was found to be strongly dependent on the crystallographic orientation of the BZT–BCT single crystals, as well as the applied magnetic field direction. Larger and anisotropic ME voltage coefficients were observed for the composite made using the (011) oriented BZT–BCT single crystal. The optimized ME coupling of 1 V/cm Oe was obtained from the Ni/(011) BZT–BCT single crystal/Ni composite, in the d32 mode of the single crystal, when a magnetic field was applied along its [100] direction. This performance is similar to that reported for the Ni/Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN–PZT) single crystal/Ni, but larger than that obtained from the Ni/Pb(Zr,Ti)O3 ceramic/Ni composites. The results of this work demonstrate that the use of lead-free piezoelectric single crystals with special orientations permits the selection of desired anisotropic properties, enabling the realization of customized ME effects in composites.11Nsciescopu
Hydrothermally fabricated epitaxial PbTiO(3) patterns patterned lithographically by etching in hydrothermal KOH solution
No full textWe would like to thank Dr. Krishna Kumar K.P. of Korea Advanced Institute of Science and Technology for his fruitful discussion with us.We investigated the chemical etching behavior of heteroepitaxial PbTiO(3) films on Nb-doped SrTiO(3) substrate with mono-+c-domain fabricated by using hydrothermal epitaxy. The as-fabricated films were patterned lithographically into submicron-sized patterns with various lateral sizes using KOH solution and the etching mechanism is suggested. Our study reveals the feasibility of fabricating patterned nanodomains in PbTiO(3) films by scanning probe microscopy domain engineering and a chemical etching process. Further, our study shows that an analysis of the distribution and morphology of polarized ferroelectric nanodomains in PbTiO(3) is possible through a precise control over the applied bias voltage, pulse width, and time. (C) 2008 American Institute of Physics.This research was supported by the National Research Laboratory Program (Contract No. M10400000024-04J0000-02410)
Diffuse dielectric anomaly of BaTiO3 in the temperature range of 400-700 degrees C
No full textThe diffuse dielectric anomaly is a well-known dielectric relaxation behavior of perovskite oxide materials, which is commonly observed in the temperature range of 400-700 degreesC. However, the detailed mechanism of the relaxation phenomenon is not clearly understood yet. The suggested relaxation models do not explain why the dielectric relaxation behavior appears as the temperature-dependent diffuse: peak. It is believed that previous studies have mainly focused on the frequency dependence of the dielectric relaxation and the variation of the relaxation time, which are usually characterized with the thermally activated process. In this study, we systematically investigated the temperature-dependent behavior of the dielectric relaxation with the remodified Debye equation in the ceramic and the single crystals of BaTiO3. We have confirmed that the diffuse dielectric anomaly is due to the competitive effects between the dielectric relaxation and the disturbance of the electrical conduction. We also suggest that the variation of the relaxation strength is related with the electrical conductivity. 2002 Published by Elsevier Science Ltd.This work is partially supported by Brain Korea project in 2001
Dielectric relaxation in Pb0.9La0.1TiO3 ceramics in the temperature range of 400-700 degrees C
No full textThe dielectric properties of Pb0.9La0.1TiO3 ceramics were investigated at intermediate frequencies (10(2)less than or equal tof less than or equal to 10(6) Hz) in the temperature range of 400-700 degreesC. The limitation of the application of Debye relaxation model was discussed to explain the temperature-dependent behavior of the dielectric relaxation. The dielectric relaxation strength was considered as an important fitting variable through the modified Debye equation. The diffuse dielectric anomaly was successfully described by introducing the exponential decay form for the relaxation strength in the modified Debye equation. (C) 2002 American Institute of Physics.This work is partially supported by the Brain Korea Project in 2001
Effect of film density on electrical properties of indium tin oxide films deposited by dc magnetron reactive sputtering
No full textTin-doped indium oxide (ITO) films were fabricated using dc magnetron reactive sputter deposition of an In 10 wt. % Sn alloy target in an Ar and O-2 gas mixture. To understand the relationship between the electrical properties of ITO films and O-2 partial pressure, the resistivity, carrier concentration and mobility, film density, and intrinsic stress in the films were measured as a function Of O-2 partial pressure. It was found experimentally that an ITO film having both maximum conductivity and carrier mobility has a film density close to its theoretical density. For the ITO film with density close to theoretical, the mean free path was the same as the grain size (=columnar diameter). This indicated that the electrical characteristics of the ITO films discussed here depend strongly on the grain size. However, for the ITO films with density lower than theoretical, the mean free paths were smaller than the grain size. It is suggested that electron scattering at pores and voids within the grain is the major obstacle for electron conduction in the ITO films having a lower density. The measurements of intrinsic stress indicate that the density of ITO films is determined by bombardment of oxygen neutrals on the growing film. (C) 2001 American Vacuum Society.This work was partly supported by the Brain Korea 21 project
Obstacle avoidance for redundant manipulators using directional-collidability/temporal-collidability measure
No full textWe present an efficient obstacle avoidance control algorithm for redundant manipulators using new measures called directional-collidability measure and temporal-collidability measure. Considering relative movements of manipulator links and obstacles, the directional-collidability/temporal-collidability measure is defined as the sum of inverse of predicted collision distances/times between manipulator links and obstacles. These measures are suitable for obstacle avoidance control since relative velocities between manipulator links and obstacles are as important as distances between them. Also, we present a velocity-bounded kinematic control law which allows reasonably large gain to improve the system performance. Simulation results are presented to illustrate the effectiveness of the proposed algorithm
Dynamic behaviour of domains during poling by acoustic emission measurements in La-modified PbTiO3 ferroelectric ceramics
No full textIn order to study the dynamic behaviour of domains during poling, the acoustic emission (AE) characteristics of two La-modified PbTiO3 ferroelectric ceramics in which 90 degrees and 180 degrees domains were respectively dominant have been investigated. One sample was a 15 mol% La-doped ceramic with a high tetragonality ratio (c/a=1.021) and the other was a 24 mol% La-doped ceramic where the tetragonality ratio was close to unity (c/a=1.007). The acoustic emission behaviour of the former sample consisted of both burst as well as continuous emission, with the latter sample mainly showing continuous emission. Energy distributions made it possible to distinguish between the AE signals resulting from 90 degrees and 180 degrees domain switching. From the observed results, it was confirmed that most of the AE occurred due to 90 degrees domain switching. By introducing an alternative switching behaviour for the 90 degrees domains, the behaviour of the AE generation during poling could be explained
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