Showing papers by "L. E. Cross published in 1997"
TL;DR: In this article, a ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers and tested in water in the frequency range of 0.3 to 2 MHz.
Abstract: Millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers. First generation transducer arrays with diaphragms varying in size from 0.2 to 2 mm were tested. Second generation 8/spl times/8 arrays have also been built and tested in water in the frequency range of 0.3 to 2 MHz. Improvements to the sol-gel process have yielded high-quality, crack-free PZT films up to 12 /spl mu/m in thickness, which leads directly to higher sensitivity and figure of merit for acoustic transducers. The longitudinal piezoelectric coefficient d/sub 33/ is 140 to 240 pC/N, measured through a double beam laser interferometer. Remanent polarization of 28 /spl mu/C/cm/sup 2/, a coercive field of 30 kV/cm, and dielectric constant of 1400 were measured on 4-/spl mu/m thick films. Test results are presented, including frequency response, beam patterns, and sensitivity. High-resolution acoustic images have been generated using these transducers and a four-element underwater acoustic lens. Potential applications for these transducers include high-frequency imaging sonars, medical ultrasound, ultrasonic communication links, and flaw detection (NDT).
253 citations
TL;DR: In this paper, the incorporation of activators (Eu3+ and Ce3+, Tb3+) in these very porous powders was checked by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence investigations.
54 citations
TL;DR: In this article, the diffuse phase transition in ferroelectrics with mesoscopic heterogeneity has been discussed within the context of a superparaelectric model by using the Ginzburg-Landau formalism.
Abstract: The diffuse phase transition in ferroelectrics with mesoscopic heterogeneity has been discussed within the context of a superparaelectric model by using the Ginzburg-Landau formalism. In the Curie region ferroelectrics with mesoscopic heterogeneity are treated as {open_quotes}superparaelectrics{close_quotes} consisting of a mass of polar clusters, each of which has Ising character. Based on the mean-field theory, the influence of the finite-size effects of polar clusters on their structural instability has been discussed by considering a coherent lattice coupling between two structurally different regions. In particular, we have analytically derived the explicit solutions of the distribution of local polarizations. In turn, the processes of polar nanophase precipitation and coarsening have been also discussed in conjunction with the local chemical or structural inhomogeneity. Moreover, we have also analyzed the relationship between the local polarization distribution and the static dielectric susceptibility in ferroelectrics with the nanometric scale heterogeneity. The width of the Curie region is dependent upon the distribution of the sum of localized correlation length, which reflects the size distribution of heterogeneity. The presented analysis reveals that the diffuse phase transition is closely associated with the existence of nanometric polar clusters and their physical size distribution. Intriguingly, our theoretical results bear a very closemore » resemblance to most experimental observations. {copyright} {ital 1997} {ital The American Physical Society}« less
49 citations
14 Feb 1997
TL;DR: In this article, a comparative experimental investigation of electromechanical characteristics of these devices along with conventional d31 bimorph and unimorph actuators was conducted in this work, and the experimental results showed that the decrease in the mechanical quality factor and resonant frequency of bending vibrations in d31 unimorph, RAINBOW, CRESCENT (CERAMBOW), and THUNDER with increasing electric field is much smaller than that in bimomorph and d33 unimorph elements.
Abstract: During the last several years novel piezoelectric bending actuators have been developed: RAINBOW, CERAMBOW, CRESCENT, d33 bimorph and THUNDER. A comparative experimental investigation of electromechanical characteristics of these devices along with conventional d31 bimorph and unimorph actuators was conducted in this work. All transducers were fabricated from soft piezoelectric ceramics. The experimental results show the d33 bimorph and unimorph elements have superior quasistatic characteristics as compared to other type of bending-mode actuators. All these piezoelectric devices demonstrate a significant dependence of electromechanical performance on the magnitude of the driving electric field. It was found that the decrease in the mechanical quality factor and resonant frequency of bending vibrations in d31 unimorph, RAINBOW, CRESCENT (CERAMBOW) and THUNDER with increasing electric field is much smaller than that in bimorph and d33 unimorph actuators. The dependence of the behavior of these devices on the operating conditions governs the selection of a particular device for a specific application.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
41 citations
TL;DR: In this paper, the dielectric response of a ferroelectric multilayer, having a designed heterogeneity, has been studied near its phase transition range by use of the Landau-Ginzburg theory.
Abstract: The dielectric response of a ferroelectric multilayer, having a designed heterogeneity, has been studied near its phase transition range by use of the Landau-Ginzburg theory. The coherent lattice coupling between ultrathin layers can be significantly strong, resulting in a broad phase transition of the superlattice system as a whole. The thickness of layers and their spatial distribution hold the keys for enhancing dielectric properties in a broad temperature range.
36 citations
01 Jan 1997
TL;DR: In this paper, a comparative experimental investigation of electromechanical properties of bending actuators along with conventional d 3 1 bimorph and unimorph actuators was conducted in order to evaluate their quasistatic properties.
Abstract: During the last several years novel piezoelectric bending actuators have been developed: RAINBOW, CERAMBOW, CRESCENT, d 3 3 bimorph and THUNDER A comparative experimental investigation of electromechanical characteristicsof these devices along with conventional d 3 1 bimorph and unimorph actuators was conducted in this work. All transducers were fabricated from soft piezoelectric ceramics. The experimental results show that d 3 3 bimorph and unimorph elements have superior quasistatic characteristics as compared to other type of bending-mode actuators. All these piezoelectric devices demonstrate a significant dependence of electromechanical performance on the magnitude of the driving electric field. It was found that the decrease in the mechanical quality factor and resonant frequency of bending vibrations in d 3 1 unimorph, RAINBOW, CRESCENT (CERAMBOW) and THUNDER with increasing electric field is much smaller than that in bimorph and d 3 3 unimorph actuators. The dependence of the behavior of these devices on the operating conditions governs the selection of a particular device for a specific application.
30 citations
TL;DR: In this paper, a hot isostatic pressing (HIP) treatment on presintered samples of PMN-PT relaxor ferroelectric lead magnesium niobate-lead titanate ceramics was proposed to reduce the aging behavior.
Abstract: The abnormal aging behavior, i.e., severe aging in the electric field induced piezoelectric coefficient while very weak dielectric aging, observed in the relaxor ferroelectric lead magnesium niobate-lead titanate (PMN-PT) ceramics under a dc electric bias field, can be significantly reduced by hot isostatic pressing (HIP) treatment on presintered samples. The aging can also be reduced by doping suitable amounts of either La (donor) or Mn (acceptor). We suggest that the reduction in the aging is due to the introduction of additional random fields into the material, which reduces the probability of the growth of micropolar regions into metastable and/or stable macropolar domains. The abnormal aging behavior and the effectiveness of HIP in reducing it indicate the importance of the elastic energy in controlling the aging and relaxor behavior in PMN-PT relaxor ferroelectrics.
28 citations
06 Jun 1997
TL;DR: In this paper, a novel piezoelectric bending actuator CRESCENT was developed, which is a stress-biased ceramic-metal composite actuator, and an extensive experimental investigation of this device in the cantilever configuration was carried out.
Abstract: Piezoelectric actuators have significant potential for use in smart systems like vibration suppression and acoustic noise canceling devices. In this work, a novel piezoelectric bending actuator CRESCENT was developed. CRESCENT is a stress-biased ceramic-metal composite actuator. The technology involves the use of the difference in thermal contraction between the ceramic and the metal plates bonded together at a high temperature by a polymeric agent to produce a stress-biased curved structure. An extensive experimental investigation of this device in the cantilever configuration was carried out. The tip displacement, blocking force and electrical admittance and were chosen to characterize the performance of the actuator under quasistatic conditions. The device fabricated at optimum temperature exhibits large tip displacement and blocking force and possesses superior electromechanical characteristics to conventional unimorph actuators.
21 citations
TL;DR: A morphotropic phase boundary between rhombohedral and tetragonal phase regions has been identified to lie in the composition range x=0.4-0.45 by means of X-ray diffraction, and dielectric, pyroelectric, and piezoelectric measurements.
Abstract: A morphotropic phase boundary between rhombohedral and tetragonal phase regions has been identified to lie in the composition range x=0.4–0.45 by means of X-ray diffraction, and dielectric, pyroelectric, and piezoelectric measurements. Some curvature to this boundary at high temperatures is indicated in the temperature dependences of the dielectric constants and pyroelectric coefficients of poled specimens.
19 citations
TL;DR: In this article, a sub-millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers.
Abstract: Sub-millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers. 8/spl times/8 transducer arrays have been tested in water in the frequency range of 0.3 to 2 MHz. An improved sol-gel process has yielded crack-free PZT films up to 12 /spl mu/m in thickness, 12/spl times/ thicker than previously reported. Sensitivity, frequency response, acoustic images and beam patterns are presented. High-resolution acoustic images at a range of 2 m were made using the arrays and an acoustic lens. Applications include high-frequency imaging sonars, medical ultrasound, ultrasonic communication links, and flaw detection.
13 citations
TL;DR: In this article, Cavity perturbation and Hakki-Coleman post-resonance (PR) methods were used for measuring the dielectric constant (e′) and the tangent loss (tan δ) on single-crystal LaSrGaO 4.
TL;DR: In this article, the fabrication of monolithic transducer arrays on silicon wafers is described, and results of air and in-water testing are presented, including frequency response, beam patterns, and output capacitance.
Abstract: Millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers. The fabrication of monolithic transducer arrays on silicon wafers is described. Transducers have been tested in water in the frequency range of 0.5 to 4 MHz. Individual transducer diaphragms varied from 0.2 to 2 mm in size. Improvements to the sol-gel process have yielded high-quality, crack-free PZT films up to 12 μm in thickness, which leads directly to higher sensitivity and figure of merit for acoustic transducers. The longitudinal piezoelectric coefficient d33 is 140–180 pC/N, measured through a double beam laser interferometer. Remanent polarization of 34 μC/cm2, a coercive field of 42 kV/cm, and dielectric constant of 1400 were measured on 4-μm thick films. Results of air and in-water testing are presented, including frequency response, beam patterns, and output capacitance. High-resolution acoustic images of have been generated using these transducers and a four-el...
14 Feb 1997
TL;DR: Barium and Strontium A-site substitution of the phase transformation behavior of (Pb0.98-(delta )La0.02A(delta )) (ZrxSnyTiz)O3 (A equals Ba, Sr) ceramics have been investigated in this article.
Abstract: Electric field induced antiferroelectric (AFE) to ferroelectric (FE) phase transformations are accompanied by large strain and significant hysteresis. The properties of these materials can be tailored to fit specific applications such as high strain actuators and charge capacitors. As an attempt to reduced hysteresis, Barium and Strontium A-site substitution of the phase transformation behavior of (Pb0.98-(delta )La0.02A(delta )) (ZrxSnyTiz)O3 (A equals Ba, Sr) ceramics have been investigated. The ceramic samples in this study produced 0.2% to 0.3% strain level. Barium proved to be a strong FE stabilizer with decreasing both switching field and hysteresis, while Strontium proved to be a strong AFE stabilizer. Some practical data, including temperature stability and current requirements, are also to be discussed.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: The PANEL (Piezoelectric Acoustic Noise ELiminator) transducer was developed for air acoustic noise cancellation in the frequency range of 200-1000 Hz as mentioned in this paper.
Abstract: The PANEL (Piezoelectric Acoustic Noise ELiminator) transducer was developed for air acoustic noise cancellation in the frequency range of 200–1000 Hz. It has a thin panel structure, occupies less volume, and is lighter than an equivalent electromagnetic transducer. This device consists of a U‐shaped configuration of piezoelectric bimorph and unimorph actuators bridged by a triangular amplifying diaphragm, which acts as an effective source of the sound radiation into air. The role of the diaphragm is twofold: it amplifies by a factor of 5–20 the tip displacement of the piezoelectric actuators and it also increases the sound emitting area. Amplitude of the vibrations and usable frequency range of the transducer depend on the dimensions and material of the actuators and diaphragm. The overall dimensions of the device fabricated were 52×50×24 mm. Soft PZT ceramics were used. The diaphragm was made of a carbon fiber reinforced composite. The diaphragm vibrations reach 500 μm rms well below the fundamental res...