Incommensuate antiferroelectric tin-modified lead zirconate titanate ceramics, PbNb0.02[(Zr1−x,Snx)1−yTiy]0.98O3, have been studied by Sawyer-Tower polarization and electrically-induced strain (ε-E) techniques. Sawyer-Tower polarization studies revealed antiferroelectric-ferroelectric (AFE-FE) P-E loops. Investigations then revealed that the electrically-induced strain associated with the AFE-FE transformation was not realized until field strengths significantly above that required for polarization saturation. It is believed that the electrically-induced strain is decoupled from the polarization due to AFEFE switching by the modulation of the phase of a <110> incommensurate structure. At field strengths above saturation, the commensurate rhombohedral ferroelectric state is believed to be induced from an incommensurate orthorhombic ferroelectric, and the electrically-induced strain is then realized.

Calcium-doped lead titanate ceramics exhibiting piezoelectric anisotropy were fabricated for applications in ultrasonic transducers, infrared detectors and surface acoustic wave devices. Transmission electron microscopy and X-ray diffraction techniques were used to characterize the development of the piezoelectric anisotropy and the dependence of the piezoelectric anisotropy on microstructure. Electron diffraction patterns indicated that most of the ferroelectric domains in samples with [CaA] up to 30 mole% were 90° domains. The size of the ferroelectric domains was not related to piezoelectric anisotropy. Ferroelectric domains could not be detected above this concentration. Measurements of the temperature dependence of dielectric properties at different frequencies did not show any ferroelectric relaxor behavior.

Two kinds of measuring method of the high-power characteristics of piezoelectric transducers are described. One is the measurement method at the resonance frequency and another is the measurement method at the antiresonance frequency. The vibrational velocity dependences of the equivalent circuit constants and the temperature rise were measured by using each measurement method under the constant vibrational velocity control. These results are useful for designing the ultrasonic power devices such as the ultrasonic motor, and also useful for investigating the new advanced piezoelectric materials for high power use. Especially, by using the results obtained at the antiresonance frequency, a stable state driving method, named as antiresonance driving, with high-efficiency and low-temperature rise can be achieved.

Heat treatment of bare single-domain LiNbO3 plates near the Curie temperature induces a local polarization reversal, thereby yielding a ferroelectric inversion layer. For a sufficiently long heat treatment the inversion layer thickness becomes equal to one half of the plate thickness. Similar domain inversion is also induced by heat treatment of protonexchanged LiTaO3. These domain inversion phenomena and a model for explaining the mechanism are reviewed.

The inversion layer has piezoelectric constants opposite in sign to those of the uninveiled domain. Therefore, a LiNbO3 plate with such an inversion layer can be used as a piezoelectric actuator similar to the bimorph, because bending motion or torsional motion can be piezoelectrically produced, depending on the plate orientation. The measured characteristics of these actuators are presented and demonstrated to exhibit excellent linearity and no hysteresis.

Composite materials have found a number of structural applications, but their use in the electronics industry has been relatively limited. As the function of electroceramic composites are better understood, we can expect this picture to change. In this paper some of the piezoelectric composite sensor and actuator studies carried out in our laboratory during the past decade will be reviewed. The ideas that provide a basic understanding of functional composites have previously been discussed [1]. This paper describes recent advances in the processing and properties of composites possessing 0-3, 1-3, and 2-2 connectivity made of polymers, metals and ferroelectric ceramics. The introduction of open spaces in the previous connectivity patterns allows the development of new designs of several piezoelectric composites with connectivity patterns of 0(0)-3, 1(0)-3, 2(0)-2-2, and 2-0-2. As in most electronic systems that are developed with improved properties a push toward lower cost and smaller sizes of the piezoelectric ceramics, together with improved reliability and performance occurs. The piezocomposites with open spaces in their structures clearly demonstrate the growth of the functional ceramics into the field of the smart ceramics as the materials for the beginning of the next century.

Various composites of BSTO combined with other nonelectrically active oxide ceramics have been formulated. In general, the composites have adjustable electronic properties which can be tailored for use in various electronic devices. Two applications, which are of interest in regard to the composites being discussed here, are phased array antennas and capacitor-varistor monolithic devices. For the phased array antennas, these properties include reduced dielectric constants, ε′, where ε = ε′ - iε″, and loss tangents, tan δ. The reduction of the dielectric constant and lowering of the loss tangents reditce the overall impedance mismatch and the insertion loss of the device. In addition, the overall tunability, change in the dielectric constant with applied voltage, is maintained at a sufficiently high level for all dielectric constants of interest. Another application (for one of the composite materials) is a combined capacitorvaristor device. In general, this would be used to protect against spurious voltage surges and voltage transients in electronic micro-circuits. The microstructures, including grain size and phase analysis, have been examined using SEM and X-ray diffraction.

Various liquid motions such as streaming and droplet formation on the surface of surface acoustic wave (SAW) propagating substrate are called SAW streaming. In this paper, the liquid dynamic motions excited by the SAW fabricated on 128° rot. Y-X LiNb03 at the frequency of 50 MHz with various pulse widths are demonstrated. The SAW streaming system are also tested for use as a micropump. Theoretically, SAW streaming force can be derived based on the acoustic streaming theory. The calculated SAW streaming force is found to be very large and strong enough to expel a droplet from a liquid surface.

Nonlinear behavior in a water drop vibration induced by the SAW streaming force is also experimentally investigated as a model of inverse bubble oscillation. We succeed in detecting the transformation of the water drop vibration with a single pulse frequency spectrum to 1/2 and its harmonics.

A new equivalent circuit for the vibratory gyroscope and an analyzing and controlling method for the vibration mode axis of the vibrator have been studied. The vibrator of this gyroscope consists of a piezoelectric-ceramic cylinder. On its outer cylindrical surface, interdigital electrodes are formed. And these electrodes are used for poling, AC excitation as well as detection. In order to prevent some deviation of the performance of the gyroscope due to the adhesion process, these electrodes are directly printed on the cylinder surface.

By changing the electrodes pattern and making a groove on the surface of the vibrator, the vibration mode axis can be easily controlled. Optimum design suited for demanded specifications can then be obtained.

Solid solutions of lead zirconate titanate (PZT) and lead magnesium niobate (PMN) doped with barium/strontium were developed for use in miniature electrostrictive actuators. The microstructural features of the materials were determined by high-resolution transmission electron microscopy (HREM) and by x-ray diffractometry. The response and the strain hysteresis were measured by applying a sinusoidal or a rectangular voltage pulse. Pulses of variable amplitude and width were applied to the elements to study the switching behavior of 90° domain walls in the materials and to elucidate the initial zero-position “walk off” mechanism. The strain hysteresis or remanent strain of PZT decreased with increasing PMN concentration. A barium-doped PZT (Ba-PZT) composition containing 4 mole% of PMN exhibited ferroelectric relator behavior with a field-induced strain much larger than those of lead magnesium niobate (PMN) electrostrictive materials and a small remanent strain hysteresis.

Stresses near the end of an internal electrode in a multilayer electrostrictive ceramic actuator are studied in detail. A finite element program capable of overcoming two major difficulties is developed. The program solves both the mechanical and electrical coupling problem and the nonlinear electric field and electric displacement relationship for these materials. Results indicate that the stress difference between the coupled and the uncoupled cases can only be distinguished when a stress singularity is present. Tensile stresses are found both in front, and behind, the end of an internal electrode. The magnitude of the stresses is predetermined by the material constants.

DX centers are semiconductor dopants which form deep states due to a large lattice relaxation. At low temperature, the DX centers exhibit persistent photoconductivity. When exposed to light in a spatial pattern, the photocarriers are confined to the illuminated regions by Coulomb interaction with the localised DX centers. The resulting spatial modulation of the free carrier density gives rise to a modulation of both the electrical conductivity and the dielectric constant. We demonstrate both effects by measurements of the conductance anisotropy and optical diffraction of samples exposed to excitation in a striped pattern. Erasure is achieved by thermal annealing. The constrast ratio of the conductivity modulation is greater than 108; in our experiment it is limited to ∼100 by light scattering. We estimate that 100nm resolution is feasible. Optical diffraction efficiencies up to 40% have been demonstrated in a stripe-illuminated thick sample. The persistence of the written patterns at low temperature is potentially useful in high-density data storage applications and the fabrication of erasable submicron devices.

We report a liquid crystal smart reflector, consisting of a cholesteric liquid crystal doped with dye. Light entering the liquid crystal is absorbed by the dye, generating heat which raises the average temperature of the liquid crystal. This in turn changes the pitch length of the cholesteric liquid crystal, causing an increase in its reflectivity, and thus reducing the amount of light absorbed by the dye molecules. A negative feedback stabilized condition is reached, in which the reflectivity is proportional to the incident light intensity. This effect is demonstrated both theoretically and experimentally.

Lead zirconate titanate (PZT) films of up to 60 μm in thickness have been fabricated on a wide variety of substrates using a new sol gel process. The dielectric properties (∈ = 900), ferroelectric (Ec = 16 kV/cm and Pr = 35 μC/cm 2) and piezoelectric properties are comparable to bulk values. The characteristic Curie point of these films is at 420 °C. Piezoelectric actuators have been developed by depositing thick PZT films on both planar and coaxial substrates. Stainless steel cantilevers and optical fibres coated with a PZT film exhibit flexure mode resonant vibrations observable with the naked eye. A low frequency in-line fibre optic modulator has been developed using a PZT coated optical fibre. The high frequency resonance of a 60 μm film on a aluminum substrate has been observed.

This paper describes the development of a space qualified active mirror—the Articulating Fold Mirror—which forms part of the scheme for recovering the optical performance of the Hubble Space Telescope. Three Articulating Fold Mirrors are incorporated into the optical train of the Jet Propulsion Laboratory's Wide Field and Planetary Camera-2, which was installed into Hubble by astronauts in December, 1993. Each Articulating Fold Mirror utilizes six electrostrictive ceramic multilayer actuators to precisely position a mirror in tip and tilt in order to correct the spherical aberration of the Hubble Space Telescope's primary mirror. Flight qualification aspects of the electrostrictive actuators are described. Pre- and postrepair images from the Wide Field and Planetary Camera, showing the effect of the optical correction, are presented.

A system to detect and locate impacts by foreign bodies on a surface was developed and tested. Fiber optic extrinsic Fabry-Perot interferometer (EFPI) strain sensors were attached to or embedded in the surface, so that stress waves emanating from an impact could be detected. By employing an artificial neural network to process the sensor outputs, the impact location could be inferred to centimeter range accuracy directly from the arrival time data. In particular, the network could be trained to determine impact location regardless of material anisotropy. Results demonstrate that a back-propagation network identifiesimpact location for an anisotropic graphite/bismaleimide plate with the same accuracy as that for an isotropic aluminum plate.

Modified BaTiO3 ceramics are candidate materials for infrared sensors in nightvision equipment. Measurements of dielectric constants, dielectric losses, pyroelectric coefficient, and heat capacities as functions of temperature and frequency are performed. Crystallographic and grain size data are also presented. It is shown that additions of these impurities to BaTiO3 alters the temperature of phase transformations and, with it, dielectric and pyroelectric properties. The results of these measurements were compared with those of PZT and PbTiO3 ceramics, which are currently the favoredmaterials for uncooled detector arrays, as well as PbTiO3 and PZT thin films. It is concluded that these oxide ceramics offer the combination of preparative ease of property modification and show good performance at low impurity concentrations.

The resistivity of the as-fabricated thermistor material, nickel-iron-manganite, changes during initial aging in the temperature range of 150-300ºC before becoming stable.X-ray photoelectron spectroscopy (XPS) was used to determine if any valency change or chemical shift of the cations or oxygen occurred during aging. The goal of the study was to identify any ionic changes that might affect thermistor stability. The only observed changes in 2p3/2 peaks due to aging were those related to Ni ions; the same peaks for Mn, Fe, and the 0-Is peak were unchanged. The changes in the Ni 2p3/2 peak may possibly be related to: (a) the migration of Ni2+ ions from octahedral to tetrahedral sites, (b) subtle changes in the energy states of Ni2+ which promoted a more stable ionic structure, or (c) the presence of Ni3+ ions, some of which revert to Ni2s+.

Thin-film thermocouples are well suited for “smart” processes where the mass of traditional two-lead thermocouples inhibits their wide utilization. However, currentthin-film thermocouples lack the robustness desired for abrasive environments. To addressthis issue, thin-film refractory metal thermocouples consisting of combinations of molybdenum, tantalum, tungsten, vanadium, or nickel were produced by ion-beam sputtering on an alumina substrate. To speed up the process of sampling a large number of material combinations, the thermocouples were made small, about 200 nm thick, 2.5 mm wide, and 12 mm long. An apparatus was fabricated to measure the thermo-electric responses of these short-length thermocouples. Materials design and heat-transfer issues relating to the applicationsand testing of these thermocouples are discussed.

Polydomain materials with periodic (modulated) domain structures are of potential practical importance since they can possess unique and desirable mechanical and physical properties. A twin related domain formation can be a result of constrained structural, ferroelectric or ferromagnetic transformations. The thermodynamic theory on the deformation of layer composites containing a polydomain (polytwin) ferroelectric component is analyzed. The deformation of the layer composite under different directional electric fields and constraints is calculated.

NON-INVASIVE photoresponse (photocurrent/voltage, reflectance and transmittance) from ferroelectric thin films and memory capacitors, with its strong dependence not only on the remanent polarization, but also on the film microstructure, crystal orientation, and nature of the interfaces (state of formation/degradation, etc.) offers an excellent “tool” for probing the ferroelectric capacitors at virtually any stage of fabrication, including on-line quality control. In fact, simultaneous measurement of spectral photoresponse and spectral reflectance, as a distinctive signature of the device probed, is an ideal, high speed, non-invasive means of evaluation for such thin films at high spatial resolution (∼ 100 nm) using beam scanning. This paper discusses three aspects of such evaluation. First, the spectral transmittance of the film as a direct function of the microstructure, second, the use of band-gap illumination (365 nm) to condition a fatigued capacitor; and third, the optical E field interaction with the ferroelectric capacitor, yielding a high speed photoresponse which is related to the remanent polarization and the operational history (status of internal fields) of the ferroelectric capacitor. Combined, these different kinds of photoresponses provide a good signature of the device quality.