Elastic and anelastic behaviour of icosahedral quasicrystals

A theory is developed, based on theoretical-group analysis, to describe the linear, reversible, time-dependent response of an icosahedral quasicrystal, containing point defects, to a stress field and known as anelastic relaxation. We obtain also anelastic relaxation relationships for the practical Young’s, shear and Poisson’s moduli.     

Temperature dependence of piezoelectric, elastic and dielectric coefficients at radial resonance of piezoceramics with an aurivillius-type structure

Aurivillius-type structure compounds are considered good candidates for piezoelectric materials at high temperature, due to their high ferro-paraelectric phase transition temperature. Despite this fact, very few papers have been published on the study of piezoelectric properties at the expected working temperatures. An iterative automatic method has been used in this work to characterize the piezoelectric, electromechanical, and elastic properties at radial resonance of thin ceramic disks with composition (SrBi2Nb2O9)0.35(Bi3TiNbOg)0.65 [SBN/BTN 35/65], from room temperature up to the ferro-paraelectric phase transition. Ceramics were prepared by sintering or by recrystallization after hot-pressing of mechanically activated precursors. By this new method, ceramics with controlled texture and microstructure are obtained. The influence of the processing route in the properties of the ceramics, over the whole temperature range of piezoelectric activity, is discussed. Values of d31 = 2.1 pC/N and kp = 2.9% at 500 degrees C are achieved.     

Identification of eigenmodes of volume piezoelectric resonators in resonant ultrasound spectroscopy

Eigenmodes of volume piezoelectric resonators used in resonant ultrasound spectroscopy (RUS) are considered. A novel method for the identification of these modes is proposed, which is based on the measurement of a temperature shift of the resonance frequency. A good coincidence of the measured and calculated eigenmode spectra is demonstrated for a quartz crystal. In comparison to the other methods of identification, the proposed approach is simple to implement and provides reliable results in solving RUS problems.     

Elastic and piezoelectric properties of La3Ga5SiO14 and La3Ga5.5Ta0.5O14: an application of resonant ultrasound spectroscopy

The electromechanical properties of La/sub 3/Ga/sub 5/SiO/sub 14/ (LGS) and La/sub 3/Ga/sub 5.5/Ta/sub 0.5/O/sub 14/ (LGT) have been studied at room temperature on 25 samples using resonant ultrasound spectroscopy (RUS). The RUS method facilitates simultaneous determination of all independent elastic and piezoelectric constants of a sample within the same frequency range and yields sample parameters with high internal consistency. Consequently, the spread of the experimental results presented here is significantly lower than the scatter of literature data obtained by different experimental techniques.     

用ATR法测量晶体的压电系数和电光系数

提出了一种测量晶体压电系数和电光系数的新方法。晶体厚度和折射率的变化导致衰减全反射(ATR)谱的同步角发生移动,进而引起反射率的变化。选择两个不同阶导模的工作角,施加电压分别测出反射光强的变化,可得到压电系数和电光系数。反射率相对于厚度和折射率的灵敏度分别可达到10^8m^-1和10^3。该方法可同时测量压电系数和电光系数,测量灵敏度高,样品结构简单,实验装置简便,所需的测量电压低。     

Elastic, dielectric, and piezoelectric losses in piezoceramics: how it works all together

The quality factor along with electromechanical coupling coefficient (CEMC) is commonly used as a measure of the energy efficiency of a piezoelectric transducer (PT) working as an energy converter. Losses in piezoceramics are phenomenologically considered to have three coupled mechanisms: dielectric, elastic, and piezoelectric. Their cumulative performance first of all determines the PT quality factor characterizing the efficiency of vibrational energy accumulation, and related to it dissipative effects. The extended definition of the PT electromechanical quality factor (EMQ) with permanent energy exchange between electrical source of excitation and PT was proposed. The EMQ analysis has been conducted on the basis of complex material constants for both stiffened and unstiffened canonical vibrational modes. The efficiency of mechanically free and electrically excited piezoceramic transducers in a wide frequency range of PT harmonics, especially between the fundamental resonance and antiresonance frequencies, was investigated, and the effect of piezoelectric loss anomaly with extremely low total losses was predicted. Particularly, optimization of PT excitation with connected reactive (capacitive) element was conducted to provide higher PT mechanical vibrational characteristics with less total losses. The requirements to the piezoceramic material parameters, types of transducer vibrations, and especially to the piezoelectric loss factor in the range of physically valid values were established to provide maximal EMQ.     

Elastic, piezoelectric, and dielectric characterization of modified BiScO3-PbTiO3 ceramics

The perovskite solid solution system (1-x)BiScO3-(x)PbTiO3 represents an interesting new family of high-temperature piezoelectric materials. Compositions near the morphotropic phase boundary (x approximately 0.64) have been reported to have high Curie temperatures (Tc > 450 degrees C) and good piezoelectric coefficients (d33 approximately 460 pC/N). In this work, manganese additions were used to improve the high-temperature electrical resistivity and RC time constant of compositions near the morphotropic phase boundary. The addition of manganese was found to shift Tc to slightly lower temperatures (442 degrees C and 456 degrees C for x = 0.64 and x = 0.66, respectively). The piezoelectric activities of the modified materials were found to be reduced slightly due to the hardening effect of manganese; however, the temperature stability and resistivity of the modified materials were significantly enhanced. In this paper we present, for the first time, a complete set of materials constants, including the elastic (sij, cij), piezoelectric (dij, eij, gij, hij), dielectric (epsilonij, betaij), and electromechanical (kij) coefficients and compare them to both unmodified 0.36BiScO3-0.64PbTiO3 and PZT5A ceramics.     

Acoustoelectric detection of ultrasound power with composite piezoelectric and semiconductor devices

The acoustoelectric interaction between an ultrasound wave propagating in a thin piezoelectric plate and an adjacent semiconductor results in a current that is proportional to the ultrasound intensity. These devices, inherently insensitive to the phase of the acoustic wavefront, can be used for large-area total power meters as well as spot intensity meters. They have broadband response and are capable of following the envelope of typical diagnostic imaging pulses. A previously derived model describing the interaction is reviewed. Experimental results obtained with several detectors are presented, including sensitivity and frequency response.     

Flexural vibrations and resonance of piezoelectric cantilevers with a nonpiezoelectric extension

A piezoelectric cantilever (PEC) is a flexural transducer consisting of a piezoelectric layer [e.g., lead zirconate titanate (PZT)] bonded to a nonpiezoelectric layer (e.g., stainless steel). A PEC with a thin nonpiezoelectric extension has two distinctive sections, each with a different thickness, different axial density, and elastic-modulus profiles and has been increasingly used as an in-situ biosensor. It has the advantages of dipping only the nonpiezoelectric extension part in an aqueous solution without electrically insulating the piezoelectric section as well as serving as the bonding pad for receptor immobilization. In this study, we examined the effect of the thin nonpiezoelectric extension on the flexural resonance spectrum and resonance vibration waveforms of PEC; in particular, how the length ratio between the piezoelectric section and the nonpiezoelectric extension section affects the resonance frequencies and resonance peak intensities of PEC. Theoretical resonance frequencies and resonance vibration waveforms were obtained using an analytical transcendental equation we derived by solving the flexural wave equation. Both experimental and theoretical results showed that the two-section structure distorted the flexural vibration waveforms from those of PEC without an extension. As a result, the higher-mode resonance peaks of PEC with a nonpiezoelectric extension could be higher than the first resonance peak due to the two-section structure. With PEC that has a piezoelectric section of 0.25-mm thick PZT bonded to 0.07 mm thick stainless steel of various length 11 and a 0.07-mm thick nonpiezoelectric extension of length l2, we showed that the first-mode-to-second-mode resonance peak intensity ratio had a maximum of 5.6 at l1/l2 = 0.75 and the first-mode-to-second-mode resonance frequency ratio a minimum of 2.2 at 11/12 = 1.8. These findings will undoubtedly help optimize the design and performance of PEC.     

Longitudinal and transverse magnetoelectric voltage coefficients of magnetostrictive/piezoelectric laminate composite: theory

This paper presents a novel, long-type of magnetostrictive and piezoelectric laminate composite design in which the layers are, respectively, magnetized/poled along their length axes, and a theory for modeling its behavior. Using piezoelectric and magnetostrictive constitutive equations, and an equation of motion, a magneto-elasto-electric bieffect equivalent circuit is developed. The circuit is used to predict the longitudinal and transverse magnetoelectric (ME) voltage coefficients of our Terfenol-D/Pb(Zr/sub 1-x/Ti/sub x/)O/sub 3/ laminate design. It is found that the longitudinal ME voltage coefficient is significantly higher (/spl sim/5x) than the transverse one, and that our new laminate design has significantly higher ME voltage coefficients under small applied direct current (DC) magnetic bias fields than designs reported previously by other groups. Experimental values were found to be coincidental with predicted ones.     

Longitudinal and transverse magnetoelectric voltage coefficients of magnetostrictive/piezoelectric laminate composite: experiments

Magnetostrictive Terfenol-D (Tb(x)Dy(1-x)Fe2) and piezoelectric (Pb(Zr(1-x)Ti(x))O3) magnetoelectric (ME) laminate composites have been investigated experimentally for various modes of operation: longitudinal magnetized/longitudinal polarized (L-L mode), transverse magnetized/longitudinal polarized (T-L mode), and transverse magnetized/transverse polarized (T-T mode) ME modes. We report their experimentally determined performance characteristics based on our previously developed equivalent circuits for these various modes. Predicted and experimental results are in agreement that the L-L mode laminates have enhanced ME effects, and that, under low or zero magnetic bias, the L-L mode ME voltage coefficients are up to a factor of 5-20x higher than those of the T-L mode or T-T mode laminates. The maximum ME voltage coefficient of the L-L mode laminates is over 86 mV/Oe under a bias of 500 Oe.     

Vibrations of an elastic structure with shunted piezoelectric patches: efficient finite element formulation and electromechanical coupling coefficients

This article is devoted to the numerical simulation of the vibrations of an elastic mechanical structure equipped with several piezoelectric patches, with applications for the control, sensing and reduction of vibrations. At first, a finite element formulation of the coupled electromechanical problem is introduced, whose originality is that provided a set of non‐restrictive assumptions, the system's electrical state is fully described by very few global discrete unknowns: only a couple of variables per piezoelectric patches, namely (1) the electric charge contained in the electrodes and (2) the voltage between the electrodes. The main advantages are (1) since the electrical state is fully discretized at the weak formulation step, any standard (elastic only) finite element formulation can be easily modified to include the piezoelectric patches (2) realistic electrical boundary conditions such that equipotentiality on the electrodes and prescribed global charges naturally appear (3) the global charge/voltage variables are intrinsically adapted to include any external electrical circuit into the electromechanical problem and to simulate shunted piezoelectric patches. The second part of the article is devoted to the introduction of a reduced‐order model (ROM) of the problem, by means of a modal expansion. This leads to show that the classical efficient electromechanical coupling factors (EEMCF) naturally appear as the main parameters that master the electromechanical coupling in the ROM. Finally, all the above results are applied in the case of a cantilever beam whose vibrations are reduced by means of a resonant shunt. A finite element formulation of this problem is described. It enables to compute the system EEMCF as well as its frequency response, which are compared with experimental results, showing an excellent agreement. Copyright © 2009 John Wiley & Sons, Ltd.     

The impact of piezoelectric PVDF on medical ultrasound exposure measurements, standards, and regulations

This paper describes the development of PVDF hydrophones for characterizing medical ultrasound fields. The polymer hydrophone approaches that have resulted from this work are discussed, with emphasis given to the spot-poled membrane design that has become the de facto reference device for these measurements. The various national and international standards and regulations that have followed from the successful use of PVDF hydrophones also are summarized. The works discussed encompass polymer-based hydrophones designed primarily for diagnostic and lithotripsy exposure measurements, both in water and in vivo. The advent of these hydrophones has made possible accurate and reliable measurements of exposure levels encountered in medical ultrasound and, thus, has allowed questions of ultrasound bioeffects and device safety to be addressed in a consistent and scientifically sound manner.     

CARS spectroscopy and optical interferometry of glow discharge plasma in nitrogen

The methods of spectroscopy of coherent anti-Stokes Raman scattering of light (CARS), optical interferometry, and emission spectroscopy are used to investigate the functions of distribution of nitrogen molecules over vibrational and rotational levels in the ground electron state. Also measured are the rate of gas heating and the distributions of gas and electron density and of translational temperature in the cross section of the discharge cuvette in plasma of dc glow discharge and contracted discharge. The obtained functions of distribution of nitrogen molecules over rotational and vibrational levels are well approximated by the Boltzmann and Treanor distributions, respectively. The radial dependence of the distribution of energy release in plasma of contracted discharge is suggested, and a solution is found of heat equation, which describes the distribution of translational temperature over the cuvette radius.     

钙钛矿型低铅压电陶瓷的制备与性能研究

采用传统陶瓷工艺制备了钙钛矿型低铅压电陶瓷xPbTi0.4716Zr0.4834（Mn1/3Sb2/3）0.0450O3-（1-x）（K0.485Na0.485Li0.03）NbO3[xPMS-（1-x）KNLN],研究了该陶瓷体系的结构和介电、压电与铁电性能以及这些结构和性能与工艺条件的关系。XRD分析表明,随着烧结温度的升高,陶瓷晶相由焦绿石相与赝立方钙钛矿相共存转变为单一的四方钙钛矿相;SEM分析表明,在烧结过程中产生了以（K0.485Na0.485Li0.03）NbO3组分为主的液相,并在烧结温度提高的过程中产生孔洞出现-孔洞消失的现象;电学测试表明,xPMS-（1-x）KNLN陶瓷具有良好的性能,在x=0.75、烧结温度为1250℃时,陶瓷的性能参数为压电常数d33=182pC/N,机电耦合系数kp=34.5%,居里温度TC=165℃,剩余极化强度Pr=21.2μC/cm2,矫顽场强Ec=1.47kV/mm,介电常数εr=1879,介电损耗tanδ=0.92%。     

On-line coupling of capillary electrochromatography, capillary electrophoresis, and capillary HPLC with nuclear magnetic resonance spectroscopy

A novel capillary NMR coupling configuration, which offers the possibility of combining capillary zone electrophoresis (CZE), capillary HPLC (CHPLC), and for the first time capillary electrochromatography (CEC) with nuclear magnetic resonance (NMR), has been developed. The hyphenated technique has a great potential for the analysis of chemical, pharmaceutical, biological, and environmental samples. The versatile system allows facile changes between these three different separation methods. A special NMR capillary containing an enlarged detection cell suitable for on-line NMR detection and measurements under high voltage has been designed. The acquisition of 1D and 2D NMR spectra in stopped-flow experiments is also possible. CHPLC NMR has been performed with samples of hop bitter acids. The identification and structure elucidation of humulones and isohumulones by on-line and stopped-flow spectra has been demonstrated. The suitability of the configuration for electrophoretic methods has been investigated by the application of CZE and CEC NMR to model systems.     

Analysis of vibration waveforms of electromechanical response to determine piezoelectric and electrostrictive coefficients

We developed a possible method to determine both coefficients of piezoelectricity (d) and electrostriction (M) at the same time by a waveform analysis of current and vibration velocity in the resonance state. The waveforms of the current and vibration velocity were theoretically described using the equations of motion and piezoelectric constitutive equations, considering the dissipation effect. The dissipation factor of the d coefficient and M coefficient is dielectric loss tangent tan δ. The waveforms measured in all of the ceramics, such as Pb(Zr,Ti)O(3) (PZT), Pb(Mg,Nb)O(3) (PMN), and 0.8Pb(Mg(1/3)Nb2/3)O(3)-0.2PbTiO(3) (PMN-PT), were well fitted with the calculated waveform. This fitting produced both the d and M coefficients, which agreed with those determined via the conventional methods. Moreover, the respective contributions of both piezoelectricity and electrostriction to the d value determined in the resonance-antiresonance method were clarified.