Highly (100) and (111) oriented lead zirconium titanate (PZT) thin films have been grown by using reactive rf-sputtering. PZT thin films with rhombohedral composition have been grown in different orientations using selective rapid thermal annealing cycles. The polarization versus electric field curves and the resistivity of the films were measured using a standardized RT66A ferroelectric test system. The dielectric constant and the loss were determined using an impedence analyzer. The PZT(100) oriented films showed larger dielectric constant and loss than the PZT(111) films. The PZT(100) films possessed sharper square-like hysteresis loops compared to the PZT(111) films, as expected from our phenomenological calculations.

Results on growth, characterization and resonator applications of AIN thin films grown by pulsed dc reactive magnetron sputtering are presented. In order to allow deposition on electrode films, moderate deposition temperatures of 300 to 400 °C were applied. On (001) sapphire, monocrystalline films were obtained. On (111)-textured platinum films, a columnar and (001) textured microstructure was established which exhibited quasi single-crystal properties in relevant materials constants, such as e33, e31, and c33. The films have been successfully applied in bulk wave resonators operating at GHz frequencies, allowing for the derivation of acoustic parameters. A zero thermal frequency drift was obtained with a membrane resonator due to a SiO2 layer as compensating element.

New piezoelectric power devices -such as ultrasonic motors, piezoelectric actuators and piezoelectric transformers- have been studied intensively in recent years. The piezoelectric ceramics in these devices are often subjected to a high level of vibration, and the electromechanical characteristics of piezoelectric ceramics at high vibration levels vary when changes in vibration level are accompanied by changes in temperature. The effects of temperature and of vibration level on specific electromechanical characteristics of typical piezoelectric ceramics were therefore separated by using two measurement methods: the continuous-voltage-wave method, which results in an increased temperature; and the burst-voltage-wave method, which does not. The elastic, dielectric and piezoelectric constants were found to be sensitive to temperature but comparatively insensitive to vibration level. Mechanical loss, however, was found to be a function of both temperature and vibration level.

Losses in piezoelectrics are considered in general to have three different mechanisms; dielectric, mechanical and piezoelectric losses. This paper deals with the phenomenology of losses, first, then how to measure these losses separately in experiments.

The successful development of smart structures using piezoelectric sensors and actuators depends on a thorough characterization of the mechanical limits of these materials. However, fundamental discrepancies between theoretical predictions and empirical observations of their cracking behavior hinder attempts to provide appropriate design guidelines. The complex microstructure of a piezoelectric ceramic leads to severe nonlinear effects at the crack tip, motivating a physics-based investigation of the fracture mechanics. Specifically, the switching and saturation that occur at the level of individual polar domains require a multiscale viewpoint in order to evaluate the conditions which control crack advance. We introduce a model for domain switching based on discrete electric dipoles superimposed on a homogeneous medium with the macroscopic material properties. Each dipole then represents the deviation of a given domain's polarization vector from the linear constitutive law. Within this framework, we develop a relationship between the apparent loads applied to a cracked sample and the local energetic forces driving the crack. Shrinking the length scale down to the crack tip reveals a “singularity conversion”, from the apparent combination of stress and electrical intensity factors to purely mechanical effective opening forces. Using the energy release rate derived from these local stress singularities to predict the dependence of failure load on applied electric field, we are able to reproduce the trends observed in the laboratory.

Switching current measurements have been carried out on relaxorferroelectric single crystal-pure PZN, and the solid solution (1-x) Pb(Zni1/3 Nb2/3)O3 - x PbTiO3 with x= 0.04, 0.09, 0.10. Measurements have been done for crystallographic directions [001] and [111] for all these compositions. Switching times versus the applied field showed the following results. Pure PZN along [111] and 0.90PZN—O. 10PT along [001], and [111] showed an exponential dependence. Along [001] the PZN showed a linear fit. For solid solution single crystals-0.96PZN -0.04PT and 0.91PZN £ 0.09PT, a linear fit was obtained for the reciprocal switch times versus applied field for both the directions. If we draw a parallel picture with the reported barium titanate data, it appears that the polarization reversal is controlled by nucleation along [111]- spontaneous direction for PZN and [001], [111]for 0.90PZN - O.10PT. The mobility of the reversed domains controls the reversal along [001] for PZN and the solid solution single crystals with rhombohedral composition along [001] and [111]. The transient current curves showed two maximum points for crystals with x = 0.04 and 0.09. This is attributed to the co-existence of the two phases in 0.96PZN -0.04PT and 0. 91PZN - 0.09PT crystals.

Composites of ferroelectric ceramic in polymer matrix have been developed and characterized for their ability to be employed as embedded sensors for the health monitoring of olymer composite structures. In this paper results illustrating the response of embedded composite sensors to dynamic loads are presented and discussed. Furthermore, the ability of the composite sensors to act as actuators, generating diagnostic waves in composite structures, has been investigated.

A new method is proposed for the characterization of properties of piezoelectric materials using depth-sensing indentation involving both mechanical and electrical measurements. First, a rigorous general theory is presented for axisymmetric indentation of piezoelectric solids with anisotropic properties. The theoretical results facilitate the prediction of the indentation load versus the depth of penetration of indenter into the substrate, as well as some transient electrical effects for different electrical boundary conditions. Used in conjunction with instrumented indentation experiments at the nanoscopic, microscopic or macroscopic size scales, these results lead to the prediction of some of the elastic, dielectric and piezoelectric constants as well as the activation energy for depolarization. The predictions of the theory as well as the validity of the approach have been substantiated further with detailed indentation experiments on PZT-4 and barium titanate using either a conducting indenter or an insulated indenter. The theoretical predictions of the coupled electrical-mechanical indentation of piezoelectric solids have also been checked with finite element analyses. The implications of the proposed method for the design and characterization of piezoelectric materials and for quality control in commercial production are also addressed.

This Paper investigates the bending behavior of piezoelectric laminates under combined mechanical and electrical loading. The laminate has a PZT - 5H ceramic core sandwiched by graphite/epoxy plates. Three-point bending tests and in-situ acoustic emission measurements were conducted on the PZT-5H laminates preloaded by an applied electric field. The results show that the PZT-5H core fractures first and then delaminaton occurs along the tensile stressed interface between the PZT ceremic and the graphite/epoxy layer. Finite element analysis was performed to analyze stresses in the sandwich structure under combined mechanical and electrical loading. Consequently, the bending strength of the PZT core was evaluated from the experiment data. The electric field, either positive or negative, reduces the fracture strength of the pzt core.

Materials such as langasite (La3Ga5SiO14) and related compounds are promising candidates for piezoelectric applications at high temperatures. In particular, langasite does not exhibit phase transformations up to the melting point of 1470 °C. Langasite was investigated with respect to potential applications in high temperature resonator devices. In contrast to current resonator materials, we have observed bulk oscillations at temperatures of up to 750 °C in langasite devices. At 700 °C the mass load response for 0.78 mm thick resonators is approximately 0.10 µg/Hz.

At elevated temperatures, the bulk resistivity of the resonator devices cannot be neglected due to attenuation of the resonance signal. Therefore, the temperature dependence of the electrical properties of langasite resonator devices, including bulk resistivity, capacity and resonance frequency were measured and are presented. The electrical conductivity is characterized by an activation energy of 105 kJ/mol. In order to confirm langasites stability with respect to oxidation-reduction reactions, we examined the oxygen diffusivity by measuring 18O tracer profiles by SIMS. The diffusivity along the Y-axis is given by D = 5-10−5 exp(-140 kJ/mol / RT) cm2/s in the temperature range from 500 to 800 °C. Langasite shows low oxygen diffusion coefficients with respect to other materials which might be investigated using a langasite microbalance. This would, for example, enable oxygen diffusion kinetics to be examined in YBa2Cu3O6 at 600 °C by means of 18O/16O exchange.

This paper presents an original linear piezoelectric motor for applications in space and robotics. The originality of this motor consists in the combination of longitudinal and shear modes of vibration of the stator. These two modes are mixed to produce an elliptical vibration of the surface of the stator in contact with a slider. The motion of the linear slider is obtained through friction forces that develop at the interface between the stator and the slider.

This motor is being developed for applications in active truss members of variable geometry structures, such as those used in space. Currently, these structures employ stepper motors. It is expected that replacing these electromagnetic devices with ultrasonic motors will offer the following advantages: position-locking without power supply, compactness, nonmagnetic operation, and lower power consumption.

This paper details the design of this motor and emphasizes the novel concept that was developed to combine the longitudinal and shear modes of vibration.

Sensorineural hearing loss results from the inability of the inner ear cochlear organ of Corti to transduce mechanical energy incident in the cochlea to electrical signals in auditory nerve fibers. Cochlear implant devices are used to alleviate this condition. Piezoelectric materials offer the unique scope of functioning as cochlear implants, possibly enabling simplification of the process of electrical stimulation and enhancing knowledge of the workings of both the healthy and artificially stimulated inner ear. The requirements imposed on such a device are discussed. It is believed that flexible piezoelectric PVDF and ceramic-polymer composites are best suited for this application. The design of a device which utilizes the bending piezoelectric mode, and results of testing the same in air are presented. Present work is aimed at understanding the fundamental dynamic piezoelectric properties in this mode and is expected to result in a device suitable for in vitro and in vivo testing.

Shape memory alloys (SMA) have generated a lot of new ideas in engineering. Application is however so far limited to clamps and springs. With respect to smart structures sensing as well as control has to be included. While sensing looks to be relatively feasible control is the big challenge. This paper describes some aerospace related smart structures ideas using SMAs and discusses the challenges which need to be solved before these ideas have can be realised.

Effective use of Shape Memory Alloys (SMAs) depends upon detailed knowledge of their thermiomechanical behavior. In this paper, thermomechanical behavior of SMAs is studied using a novel ACES methodology. More specifically, variation of modulus of elasticity of equiatomic NiTi is studied, as a function of temperature. The results show that the modulus of elasticity of the NiTi studied herein varies from 38 GPa to 72 GPa as the temperature changes from –15 °C to 190°C, corresponding to phase transition from martensite to austenite. Comparison of Analytical, Computational, and Experimental Solutions (ACES) results showed good correlation.

Films deposited on corrugated surfaces develop non-uniform stresses when cooled from the deposition temperature. A disclination model shows that the stresses have rhombohedral and tetragonal components which can preferentially stress induce the martensite variants. The deflection of NiTi/Si bimorphs caused by the formation of martensite should thus be different if the NiTi/Si interface is corrugated or not. Experimental results confirm this expectation.

Electro-magnetic nozzleless melt-spinning method was developed by combining the control of the flow down of the molten metals after electromagnetic float-melting(i.e. levitation) with rapid solidification by rotating roll. The metallurgical grain microstructures can be changed by rotating roll speed. It was confinned that the produced, intermetallic TiNi and NiAl system alloy thin plates showed the strong crystal anisotropy, higher shape memory functional properties than those of the conventionally processed melt-worked samples having its same origin. As new SMAs by using this method, ferromagnetic shape memory, FePd alloy having very large magnetostriction and super high temperature shape memory, RuTa alloy having the transformation over 1000°C were developed. Moreover, our recent study on the advanced rapid-solidification machine to produce many kinds of short fibers as well as ribbons is introduced. Finally, harmonic material design for sensor/actuator stacking composite system, namely “Smart Board” for aircraft structures will be introduced.

The hysteresis of thin film shape memory actuators affects the frequency of actuators switching between martensite and austenite. Therefore the hysteresis properties of thin films of TiNi, Ti(Ni,Cu) and Ti(NiPd) deposited onto metallic substrates by DC-Magnetron sputtering have been investigated. The substrates have different expansion coefficients to establish biaxial tensile and compressive film stresses, respectively. The results show, that the hysteresis width is significantly affected by the stress state of the shape memory film and in principal depends on the temperature range of measurement. In contrast, the difference Af-Mf remains unchanged. In some alloys zero hysteresis width could be obtained.

The mechanical fatigue life and tensile property of a Ti-41at.%Ni-8.5at.%Cu alloy, which was solution-treated after some thermo-mechanical treatments, were investigated at 370±1 K as a function of deformation speed. The tensile properties were also investigated at 295±1 K as a function of deformation speed. The B2→B19 martensitic transformation start temperature, Ms, of the alloy was determined to be 338 K by a differential scanning calorimetry, while that of the as-rolled alloy could not be determined. Two types of fatigue tests were carried out by using plate-shaped specimens of 3.5 mm width and 1.5 mm thickness with sinusoidal waveform stresses of 20 Hz and 0.5 Hz frequencies being applied respectively. The fatigue life obtained from the 20 Hz tests was superior to that from the 0.5 Hz tests, the former being about 2 times longer than the latter at the same stress level. Tensile tests were performed at three tensilem speeds of 8.3 × 106, 8.3 × 10−5 and 8.3 × 10−3 m/s. In all the stress - strain curves obtained, an apparent yielding was observed after the liner elastic deformation. The apparent yielding is due to the occurrence of martensitic transformation. The critical stress for inducing martensite and tensile fracture stress increased with increasing tensile speed. Therefore, it is clear that fatigue and tensile properties of Ti-Ni-Cu shape memory alloys are strongly affected by not only test temperature but also deformation speed.

Polycrystalline NiTiHf films with around 9at% Hf have been successfully deposited from a single NiTiHf target using a DC magnetron sputtering system. Free standing films were obtained by depositing the films on single crystal silicon substrates. Thickness of the films was controlled between 10-12µm. In this investigation, the effects of deposition temperature on the crystallinity and transformation temperatures of the films were studied. Substrate temperature during deposition was varied between 300°C and 700°C at 100°C intervals. The influence of heat treatment temperature on the properties of the films was also investigated. The heat treatment temperature was between 300°C and 800°C at 100° C intervals. Transformation temperatures of these films were determined by differential scanning calorimetry (DSC). The crystallinity was determined using x-ray diffractometry. It was found that all the as-deposited films were crystalline even when the substrate temperature was as low as 300°C. Both martensite and austenite transformation temperatures increase with increasing substrate temperature and increasing heat treatment temperature.

The objective of this development program was to demonstrate the feasibility of producing superelastic NiTi shape-memory alloy (SMA) foil material by the low pressure plasma spraying (LPPS) process for the development of robust, corrosion resistant and long life sealing technology.

A conventional LPPS facility was retooled for the use of electric wire arc spraying and the process parameters were reconfigured. Foil specimens sprayed up to 1.5mm thickness showed good ductility after consolidation heat treatment at 950'C for 1 hour. Subsequent rolling of the foil specimens to a thickness of 0.5mm exhibited superelastic behavior. The amount of superelasticity will have to be determined. In addition, thin (0.2 mm) and thick (0.76mm) wall tubes have been produced in the 12.5mm diameter range. These samples were heat treated and subjected to Hot Isostatic Pressing (HIP). Metallographic examination revealed dense, solid microstructures after heat treatment and rolling, and hot isostatic pressing respectively.

It was concluded, that this development established the feasibility to produce near net shape superelastic NiTi foil with a retooled Low Pressure Wire Arc Spraying (LPWAS) process, modified to permit substitution of NiTi-wire for NiTi-powder as feed stock.