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This work combines a 99.2% efficient GaN-based low-voltage fast-switching half-bridge converter with a Si-based high-voltage slow-switching and almost lossless switched capacitor multiplexer using a partial power processing approach to a six-level prototype with 99.74% efficiency. A loss breakdown shows how the ideal partial power processing efficiency is theoretically increased to 99.84% by using four additional voltage levels, but then reduced to the measured efficiency by the additional static and dynamic losses of the multiplexer. For electrocaloric heat pumps, an emerging technology for cooling and heating applications with zero global warming potential, such high charging efficiencies enable a high heat pump system coefficient of performance (COP). Based on available data of electrocaloric lead magnesium niobate (PMN)-based samples, and based on a first-principle and best-case analysis for Carnot-like cycles, it is predicted that the 99.74% electrical charging efficiency in combination with the electrocaloric material data enables to surpass 50% of the thermal Carnot limit (for cooling with a heat pump). Ultra-high efficiency of power converters thus pave the way towards future electrocaloric heat pumps of competitive system performance.

This paper reports on the fabrication of 1–3 piezocomposites for ultrasonic transducers with operating frequencies up to 40 MHz based on recent developments of the soft mold technique. Compared to the established dice-and-fill technique, the soft mold process allows for the manufacturing of 1–3 piezocomposites with higher variability of pillar design and distribution as well as smaller structural size. Consequently, spurious modes generated by the lateral composite layout can be pushed to higher frequencies, which allows for increased operating frequency. Different designs of circular piezoceramic pillars in hexagonal arrangement with decreasing diameters and spacings have been developed and characterized in order to shift spurious modes to frequencies approximately twice the desired working frequency. The influence of the lateral composite layout on resonance modes is investigated by analyzing the produced transducers with respect to their electrical impedance spectra. Experimental results are explained in detail and compared to modeled data. Results show that by downsizing pillar diameter from 30 to $15~\mu \text{m}$ and pitch from 40 to $19~\mu \text{m}$ , the first spurious mode could be shifted from ~42 to ~78 MHz. Thereby, the soft mold process proves to be suitable for the fabrication of 40-MHz ultrasonic transducers based on 1–3 piezocomposites.

The requirements of our third generation 3D ultrasound computer tomography system (USCT) led to a transducer array design based on single-fibre piezocomposites. The used piezoelectric ceramic fibres exhibit a thickness to diameter ratio of 4/3. This ratio results in a proximity of the dominant axial and lateral vibration resonances. The standard Krimholtz-Leedom-Matthaei (KLM) model considers only one spatial dimension. This limits the validity of the modelled predictions for our application. By adding a coupled transmission line in series to the axial resonator, the standard model can be extended to take additional spatial dimensions into account. Using model parameters from literature resulted in a low model-to-measurement fit. To enhance the prediction accuracy, a brute-force optimisation over four model parameters was conducted. With the optimal parameter set, a fit of 90.3% could finally be achieved. The necessary model parameter changes were found reasonable for the piezocomposite design. With the presented model enhancement it is now possible to consider both dominant vibration modes of our transducers.

Process monitoring and controlling with detailed real-time information such as the cutting force is required for improving the performance of milling processes. This paper presents a novel system for measuring the cutting force in the direct vicinity of the indexable insert. The outlined concept makes use of piezoelectric thick film sensors mounted directly below the insert. The unique design and features of the new sensor enable accurate and continuous force measurements as well as the indication of wear. The results of the experimental investigations are presented and compared to results of a conventional dynamometer.

Electrocaloric device structures have been developed as multilayer ceramics (MLCs) based on fundamental research carried out on PMN-8PT bulk ceramics. Two different MLC structures were prepared with nine layers each and layer thicknesses of 86 μm and 39 μm. The influence of the device design on its properties has been characterized by microstructural, dielectric, ferroelectric, and direct electrocaloric measurement. For direct characterization two different methods, ie temperature reading (thermistor and thermocouple) and heat flow measurement (differential scanning calorimetry), were used. A comparison of results revealed a highly satisfactory agreement between the different methods. This study confirms that MLCs are promising candidates for implementation into energy-efficient electrocaloric cooling systems providing large refrigerant volume and high electrocaloric effect. Due to their micron-sized active layers, they allow for the application of high electric fields under low operation voltages. We measured a maximum electrocaloric temperature change of ΔT=2.67 K under application/withdrawal of an electric field of ΔE=16 kV mm−1, which corresponds to operation voltages below 1.5 kV.

The application of piezoelectric transducers to structural body parts of machines or vehicles enables the combination of passive mechanical components with sensor and actuator functions in one single structure. According to Herold et al. [1] and Staeves [2] this approach indicates significant potential regarding smart lightweight construction. To obtain the highest yield, the piezoelectric transducers need to be integrated into the flux of forces (load path) of load bearing structures. Application in a downstream process reduces yield and process efficiency during manufacturing and operation, due to the necessity of a subsequent process step of sensor/actuator application. The die casting process offers the possibility for integration of piezoelectric transducers into metal structures. Aluminum castings are particularly favorable due to their high quality and feasibility for high unit production at low cost (Brunhuber [3], Nogowizin [4]). Such molded aluminum parts with integrated piezoelectric transducers enable functions like active vibration damping, structural health monitoring or energy harvesting resulting in significant possibilities of weight reduction, which is an increasingly important driving force of automotive and aerospace industry (Klein [5], Siebenpfeiffer [6]) due to increasingly stringent environmental protection laws. In the scope of those developments, this paper focuses on the entire process chain enabling the generation of lightweight metal structures with sensor and actuator function, starting from the manufacturing of piezoelectric modules over electrical and mechanical bonding to the integration of such modules into aluminum (Al) matrices by die casting. To achieve this challenging goal, piezoceramic sensors/actuator modules, so-called LTCC/PZT modules (LPM) were developed, since ceramic based piezoelectric modules are more likely to withstand the thermal stress of about 700 °C introduced by the casting process (Flössel et al., [7]). The modules are made of low temperature cofired ceramic (LTCC) tapes with an embedded lead zirconate titanate (PZT) plate and are manufactured in multilayer technique. For joining conducting copper (Cu) wires with the electrode structure of the LPM, a novel laser drop on demand wire bonding method (LDB) is applied, which is based on the melting of a spherical CuSn12 braze preform with a liquidus temperature Tliquid of 989.9 °C (Deutsches Kupfer-Institut Düsseldorf, [8]) providing sufficient thermal stability for a subsequent casting process. Keywords: Active noise reduction, Laser assisted wire bonding, Smart structures, Piezoelectric transducers, Die casting, Lightweight design

Schnellere Entwicklungszeiten, kürzere Produktlebenszyklen sowie die Zunahme kundenspezifischer Lösungen erfordern Werkzeugmaschinen, die ihr Verhalten selbstständig so anpassen, dass zu jedem Zeitpunkt eine qualitativ und produktiv optimale Verarbeitung erfolgt. Ein neuartiges, hochintegriertes Sensorsystem ermöglicht eine genaue und kontinuierliche Kraftmessung bei Fräsprozessen zur Prozesssteuerung und Verschleißerfassung.

Scanning Acoustic Microscopes for nondestructive imaging commonly use strong focusing single element probes with center frequencies up to 230 MHz. Depending on the test scenario and the materials a resolution down to 10 µm is reachable. This high resolution means a small extension of the sensitivity zone in lateral and axial direction and leads to the necessity of multiple C-Scans for the inspection of a volume. Using an annular-array transducer, the focal point can be shifted in axial direction. Thus, multiple scans in different depth can be replaced by a single scan. To achieve a comparable resolution to strong focused single element transducers it is necessary to increase the center frequency of annular-array transducers. So we present a prototype of a probe, that contains a planar annular-array transducer with a center frequency of 20 MHz and an aperture of 5.4 mm, separated into four quartered rings (16 elements). The characterization of the sound field, using a spherical reflector, shows a sensitivity zone with a lateral extension of 300 µm for focusing without a lens.

Solid-state refrigeration using the electrocaloric effect (ECE) in ferroelectric materials is a promising alternative to the conventional vapor-compression technology. In spite of growing interest to the investigation of the ECE, direct measurements of the effect are still rare. In this paper, we report on a modification of a differential scanning calorimeter for direct ECE measurements. The importance of proper estimation of the thermal correction factor and use of proper values of the heat capacitance for correct ECE measurements is discussed. The ECE measurements were performed for Ba(Zr0.2Ti0.8)O3 and Ba(Zr0.12Ti0.88)O3 bulk ceramics. Large electrocaloric temperature changes of 0.54 and 0.34 K are achieved under the application of an electric field of 2 kV/mm for the Ba(Zr0.12Ti0.88)O3 and Ba(Zr0.2Ti0.8)O3 samples, respectively. The relation between the directly measured ECE values and frequently used indirect estimation based on Maxwell's relations is discussed.

Epitaxial films are a useful tool to study the interplay between the microstructure and the electrocaloric properties in order to optimize the performance of these materials. Therefore, epitaxial 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-PT) films were grown by pulsed laser deposition on (001)-oriented single crystalline SrTiO3 (STO) substrates using an epitaxial La0.7Sr0.3CoO3 buffer as bottom electrode and additional Au top electrodes on the surface of the PMN-PT layer. The main goal of our study was to characterize the influence of the laser fluence on the structural properties. Our data show that pyrochlore-free PMN-PT films can be realized for low fluences. The relative permittivity and the polarization were determined as a function of temperature to verify the ferroelectric quality of our films.

Integration of piezoceramic particles into polymers is considered to meet current and future challenges of function integration in lightweight engineering. Especially composites with integrated piezoceramic transducers for sensory tasks such as condition or structural health monitoring are gaining importance. A possible, mass production compatible manufacturing approach is the direct formation of a piezoceramic particle-electrode-assembly during the processing by integrating the ceramic and its electrodes into the polymer matrix. The piezoelectric particles are then fully surrounded by the polymer matrix, forming a so-called 0–3 composite (Newnham et al., 1978). However, it is unpoled and inactive and thus requires poling to activate the piezoelectric properties. It is known that poling of piezoelectric particles in a polymer matrix is difficult due to the misfit in dielectric constants of polymer and ceramic. To overcome this obstacle, a poling process that is conducted during the uncured stage of the polymer matrix is introduced in the present paper, making use of the relatively low electrical resistance of the selected polymer in the uncured state. In a first step, the method is modelled and experimentally verified using specimen made of PZT pearls embedded in epoxy resin. In these preliminary experiments, effective piezoelectric charge coefficients up to 28.6 pC/N were achieved. The method is transferred and integrated into the production of fibre-reinforced polyurethane composites. Effective piezoelectric charge coefficients of 5.5 pC/N are obtained for the polyurethane based composites.

The electrocaloric effect (ECE) in ferroelectric materials is a promising candidate for small, effective, low cost, and environmentally friendly solid state cooling applications. Instead of the commonly used indirect estimates based on Maxwell's relations, direct measurements of the ECE are required to obtain reliable values. In this work, we report on a custom-made quasi-adiabatic calorimeter for direct ECE measurements. The ECE is measured for two promising lead-free materials: Ba(Zr0.12Ti0.88)O3 and Ba(Zr0.2Ti0.8)O3 bulk ceramics. Adiabatic temperature changes of ΔTEC = 0.5 K at 355 K and ΔTEC = 0.3 K at 314 K were achieved under the application of an electric field of 2 kV/mm for the Ba(Zr0.12Ti0.88)O3 and Ba(Zr0.2Ti0.8)O3 samples, respectively. The quasi-adiabatic ECE measurements reliably match other direct EC measurements using a differential scanning calorimeter or an infrared camera. The data are compared to indirect EC estimations based on Maxwell's relations and show that the indirect measurements typically underestimate the effect to a certain degree.

Piezoceramic actuators based on thick film technology offer the opportunity of integrated solutions for smart microsystems. Especially in adaptive micro-optics, where the height of devices is limited, outgassing has to be inhibited and complex actuator structures are required, screen printed actuators are of great interest. The paper highlights our recent research on micro-positioning stages for integration into a plenoptic camera. The first concept is based on through-thickness polarized lead zirconate titanate (PZT) thick films printed on a 45 mm × 44 mm × 0.17 mm LTCC (Low Temperature Cofired Ceramics) frame with 4 mm wide legs. Driving with an electrical field of 2 kV/mm resulted in an upright stroke of 115 μm. The second concept combines through-thickness and in-plane polarized thick films on four cantilever beams of an Al2O3 based micro-positioning stage. Because of the combination of d31- and d33-mode of excitation, each cantilever beam will provide an s-shaped bending profile allowing for a planar and tilt free lift of 130 μm at 1.66 kV/mm. Both actuator concepts were exploited to adjust position of a micro-lens array between main lens and image sensor in a plenoptic camera setup. With that, working range of the plenoptic camera could be extended.

The effect of direct integration of PZT into LTCC by sintering on its polarization behavior is studied. Due to the typically small thermal expansion of PZT, compressive stresses are expected after cooling, which should promote poling. However, measurements show a strongly reduced remanent polarization compared to free PZT. Analysis of thermal expansion reveals that thermal shrinkage of the PZT is larger than that of LTCC. The impact of this finding on the poling behavior is simulated for the LTCC/PZT module, confirming the experimental observations and allowing for conclusions concerning the suitability of the PZT for integration into LTCC structures.

In this article, the challenging manufacturing process of a deformable mirror for the wave front correction of a high energy laser is described. During this process, the low temperature co-fired ceramic (LTCC) membrane as the base component with integrated sensors must endure several postfire processes at temperatures of up to 900°C without any degradation of the sensors' characteristics. To optimize the sensors, various combinations of resistor and conductor pastes and different geometries are characterized. The usability and the performance of the sensor elements after temperature treatment are investigated by measuring the resistance and its resistance temperature characteristic.

High frequency ultrasonic transducers have attained a lot of interest for high-resolution imaging, especially for non-destructive testing and biomedical imaging applications. Conventional dice-and-fill technique for fabrication of 1–3 piezocomposites becomes laborious and time-consuming as pillar size and gap width decrease. The soft mold process offers the opportunity for fabrication of fine-scale piezoceramic arrays with free design of ceramic pillars and different spatial distribution. Here, we report on the development of a 20 MHz ultrasonic transducer. Different designs of piezoceramic rods and spacings have been tested and characterized to shift spurious modes to frequencies approximately twice as working frequency. Ceramic pillars based on triangle and half hexagon cross sections tend to topple during sintering. Best results have been obtained using circular pillars in hexagonal arrangement with sintered dimensions of 34 µm diameter, 160 µm height and 10 µm spacing. 1–3 piezocomposites based on these structures show a coupling coefficient k t = 0.6 at the thickness resonance of 20 MHz. First resonance of pillar-to-pillar periodicity is measured at 37 MHz far enough away from thickness mode resonance.

This paper reports research into the use of a crossed-electrode two-dimensional thick film lead zirconate titanate ultrasonic transducer array for particle manipulation under the control of electronics based on field programmable gate arrays. The array consists of 30 × 30 transducer elements defined by electrode crosspoints and works at approximately 7.25 MHz. Laser vibrometry of the array surface displacement profile demonstrates that single or multiple elements can be addressed and multiplexed with bespoke electronics. The array has also been demonstrated for particle manipulation with planar resonators. The results suggest potential to create dexterous acoustic tweezing devices with reconfigurable electronics and batch-produced screen-printed ultrasound transducer arrays with large number of elements.

The electrocaloric effect (ECE) of BaZr$_{x}$Ti$_{1-x}$O$_3$ (BZT) is closely related to the relaxor state transition of the materials. This work presents a systematic study on the ECE and the state transition of the BZT, using a combined canonical and microcanonical Monte Carlo simulations based a lattice-based on a Ginzburg-Landau-type Hamiltonian. For comparison and verification, experimental measurements have been carried on BTO and BZT ($x=0.12$ and $0.2$) samples, including the ECE at various temperatures, domain patterns by Piezoresponse Force Microscopy at room temperature, and the P-E loops at various temperatures. Results show that the dependency of BZT behavior of the Zr-concentration can be classified into three different stages. In the composition range of $ 0 \leq x \leq 0.2 $, ferroelectric domains are visible, but ECE peak drops with increasing Zr-concentration harshly. In the range of $ 0.3 \leq x \leq 0.7 $, relaxor features become prominent, and the decrease of ECE with Zr-concentration is moderate. In the high concentration range of $ x \geq 0.8 $, the material is almost nonpolar, and there is no ECE peak visible. Results suggest that BZT with certain low range of Zr-concentration around $x=0.12 \sim 0.3 $ can be a good candidate with relatively high ECE and simutaneously wide temperature application range at rather low temperature.

One potential use of ferroelectrics is as active material in electrocaloric cooling systems. These systems promise a more energy efficient cooling process than vapor compression, thermoelectric or other current cooling systems. Currently different design types of electrocaloric cooling devices are in the focus of research. In this paper, we present an electrocaloric cooling device demonstrator working as “Active Electrocaloric Regenerator” (AER) and employing relaxor ferroelectric elements as active material. The device design is such that it allows the integration of different material systems and regenerator designs as well as a broad variation of operational parameters.

Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) compounds, which are typically used for high performance actuator applications due to their outstanding piezoelectric properties, show, in addition, a pronounced electrocaloric (EC) effect. The study of epitaxial films is a useful tool to analyze the correlation between the microstructure and EC properties in order to optimize the performance of these materials. Therefore, the 0.9PMN-0.1PT films were grown by a pulsed laser deposition on (001) as well as (111) oriented SrTiO3 single crystalline substrates using a La0.7Sr0.3CoO3 buffer as the bottom electrode and additional Au top electrodes. The structural properties determined by a high resolution X-ray and electron microscopy techniques indicated an undisturbed epitaxial growth. The anisotropy of the ferroelectric domain structure was investigated by a vertical and lateral piezoresponse force microscopy showing clear differences between the two orientations. A significant reduction of the thermal hysteresis was observed in the T-dependent polarization measurements for (111) oriented PMN-PT films, whereas the indirectly determined EC properties yield a maximum DT of around 15 K at 40 °C for a field of about 400 kV/cm for both film orientations.

This work investigates the polarization behavior of low-temperature cofired ceramic (LTCC)/PZT sensor-actuator-modules fabricated by packaging of ceramic PZT plates between alumosilicate-corundum LTCC green layers and subsequent sintering at elevated temperatures. Polarization evaluation was done by applying the laser intensity modulation method (LIMM) where a thermal wave travelling into the ferroelectric PZT ceramic plate is generated by an intensity-modulated laser beam. The penetration depth of the thermal wave was varied with the modulation frequency allowing the separation of pyroelectric response contributions at different regions from the surface to the frequency-dependent penetration depth of the thermal wave.

This paper reports the development of a two-dimensional thick film lead zirconate titanate (PZT) ultrasonic transducer array, operating at frequency approximately 7.5MHz, to demonstrate the potential of this fabrication technique for microparticle manipulation. All layers of the array are screen-printed then sintered on an alumina substrate without any subsequent patterning processes. The thickness of the thick film PZT is 139±2μm, the element pitch of the array is 2.3mm, and the dimension of each individual PZT element is 2×2mm(2) with top electrode 1.7×1.7mm(2). The measured relative dielectric constant of the PZT is 2250±100 and the dielectric loss is 0.09±0.005 at 10kHz. Finite element analysis was used to predict the behaviour of the array and to optimise its configuration. Electrical impedance spectroscopy and laser vibrometry were used to characterise the array experimentally. The measured surface motion of a single element is on the order of tens of nanometres with a 10Vpeak continuous sinusoidal excitation. Particle manipulation experiments have been demonstrated with the array by manipulating Ø10μm polystyrene microspheres in degassed water. The simplified array fabrication process and the bulk production capability of screen-printing suggest potential for the commercialisation of multilayer planar resonant devices for ultrasonic particle manipulation.

Theelectrocaloric effect (ECE) in ferroelectric materials is a promising mechanism for the development of small, effective, low cost, and environmentally friendly solid state refrigerators. During the last decade, an increased interest has been paid to studies of this effect. Getting reliable values requires direct measurements of the ECE instead of the frequently used indirect estimates based on Maxwell's relation. In this paper, we report on the modification of a differential scanning calorimeter for direct ECE measurements. The importance of proper estimation of the heat capacitance and thermal losses for the correct ECE measurements is discussed. The ECE was measured for bulk ceramics Ba(Zr 0.2 Ti 0.8 )O 3 . The temperature change reaches a value of ΔT EC = 0.44 K at 305 K under an electric field of 2 kV/mm. The obtained data are compared with results of the evaluation of the indirect ECE.

3-D Ultrasound Computer Tomography (USCT) is aimed at early detection of breast cancer. The system uses Synthetic Aperture Focusing Technique (SAFT) for reconstruction of images. 2041 unfocused ultrasound transducers with approx. 2.5MHz center frequency, 1MHz bandwidth and 36° opening angle at −3dB. The system was optimized for highest image quality within a Region Of Interest (ROI). The analysis shows that to increase the size of ROI for the next generation USCT, the opening angle of transducers needs to be increased to 60° while the other characteristics should be preserved or even improved. The approach presented in this paper for fabricating the transducers fulfilled the expectation of reproducible transducer arrays regarding disc thickness and fibre position and size. The mean electrical impedance and phase of the fibres were approx. 10 kΩ and −30° respectively. Though the −3dB opening angle is successfully increased to 61.6°, unexpectedly the characteristics of all the fibres possess great variability and the absolute sound pressure is down by approx. 80%.

PZT thick films on various substrates are of great interest for applications as pressure sensors, micropumps, ultrasonic and pyroelectric transducers, deformable mirrors and ferroelectric printing forms. Until now, functional properties and microstructure of such films were still not sufficiently solved. Concerning the application as a printing form in an electrostatic printing process a homogeneous microstructure of the PZT film is necessary in order to homogenize the relevant surface potential. Though PZT thin films show very fine grains and thus allow excellent resolution, their surface potential is unstable due to the low internal resistance. Therefore, we have performed an investigation in order to find out whether the combination of thick and thin film technology results in films which can be homogeneously polarized on a scale

For the optimization of thin piezoelectric fibers it is necessary to determine their dielectric, elastic and piezoelectric properties. We developed analytical approximations to calculate the elastic coefficient S-33,f(E) of the fibers from the effective coefficients C-33,eff(E) and S-33,eff(E) of 1-3 composites containing such fibers. The analytic solutions have been checked by modeling with the Finite-Element-Method and compared with experimental results of model structures containing rods of soft PZT ceramic with known material properties. The elastic coefficients of the 1-3 composites were determined using the resonance method with different sample geometries for different vibration modes. The new method was applied to characterize the elastic properties of undoped PZT fibers with a Zr-content from 48 to 58 mol%. The elastic coefficient S-33(E) of the fibers shows a maximum value of 15*10(-12) m(2)/N at a Zr/Ti ratio of 51/49.

Based on high pressure die casting (hpdc) technology, this study deals with the integration of piezoceramic modules into aluminum castings. Despite of the severe thermal and mechanical loads during the casting process, a successful integration of polymer based piezoceramic modules is possible. Measurements show the influence of the distance of the module to the neutral axis on the functionality. In addition wall thickness influences the performance of the module. In order to quantify the efficiency of the actuatoric functionality in the integrated state, a beam bending model is used. A comparison of the theoretical to the experimental behavior shows nearly no loss of module performance in thin-walled parts but a decrease of the performance with increasing wall thickness.

An emerging demand for the precise manipulation of cells and particles for applications in cell biology and analytical chemistry has driven rapid development of ultrasonic manipulation technology. Compared to the other manipulation technologies, such as magnetic tweezing, dielectrophoresis and optical tweezing, ultrasonic manipulation has shown potential in a variety of applications, with its advantages of versatile, inexpensive and easy integration into microfluidic systems, maintenance of cell viability, and generation of sufficient forces to handle particles, cells and their agglomerates. This article briefly reviews current practice and reports our development of various ultrasonic standing wave manipulation devices, including simple devices integrated with high frequency (>20 MHz) ultrasonic transducers for the investigation of biological cells and complex ultrasonic transducer array systems to explore the feasibility of electronically controlled 2-D and 3-D manipulation. Piezoelectric and passive materials, fabrication techniques, characterization methods and possible applications are discussed. The behavior and performance of the devices have been investigated and predicted with computer simulations, and verified experimentally. Issues met during development are highlighted and discussed. To assist long term practical adoption, approaches to low-cost, wafer level batch-production and commercialization potential are also addressed.

Structural devices with integrated adaptive functions are demanded in lightweight engineering especially in automotive and aerospace industries and mechanical engineering. As base of such systems, piezocomposites are of high interest. They can be made from piezoceramic components, e.g. plates, fibers, or more complex three-dimensional structures, integrated into matrix materials. We developed the polysulfone spinning process as an appropriate technique to produce dense piezoceramic components with different shapes. The paper reports on fabrication and properties of PZT fibers, fiber fragments and spherical samples (pearls). Potential applications of customized PZT components for smart structures and ultrasonic transducers are shown.

Screen-printed lead zirconate titanate (PZT) thick film actuators are beneficial for miniaturized devices due to their flat profile and accurate net-shaped fabrication. Sintering progress and piezoelectric performance depend on the type and amount of sintering additive. Cantilever structures were fabricated by the use of screen printing technology with a systematic variation of the sintering additive content and for two different piezoceramic base materials. Their microstructure, small and large signal properties were characterized. Based on the experimental data we developed an actuator frame to lift a micro-lens array within a low-profile microscope by 115 μm.

This paper reports the fabrication and evaluation of a two-dimensional thick film PZT ultrasonic transducer array operating at about 7.5 MHz for particle manipulation. All layers on the array are screen-printed and sintered on an Al2O3 substrate without further processes or patterning. The measured dielectric constant of the PZT is 2250 ± 100, and the dielectric loss is 0.09 ± 0.005 at 10 kHz. Finite element analysis has been used to predict the behaviour of the array and impedance spectroscopy and laser vibrometry have been used to characterise its performance. The measured deflection of a single activate element is on the order of tens of nanometres with 20 Vpp input. Particle manipulation experiments have been performed by coupling the thick film array to a capillary containing polystyrene microspheres in water.

In nondestructive testing Structural Health Monitoring (SHM) has become very attractive because it allows for permanent and online damage detection and characterization of structural components. SHM systems using transmission and receiving of ultrasonic waves are mainly based on piezoceramic transducers made of piezoceramic-polymer-composites. We introduce a new generation of SHM transducers which are fully based on inorganic materials showing a distinguished improve of temperature and chemical stability. Using ceramic multilayer technology piezoceramic discs are integrated into a package of low temperature cofired ceramic sheets enabling for the production of compact ultrasonic transducers with integrated electronic circuits and signal processing units.

Epitaxial BaZr x Ti1−x O3 (BZTO) thin films with Zr contents of x = 0, x = 0.12 and x = 0.2 were grown by pulsed laser deposition on (0 0 1)-oriented single crystalline SrTiO3 substrates utilizing an additional conducting SrRuO3 buffer layer. It was found that the oxygen pressure during the deposition heavily influences the lattice constants and the microstructure of BZTO. A low of 0.01 mbar gives rise to a significant tetragonal distortion. Texture measurements reveal that an undisturbed epitaxial growth is only achieved for BZTO films prepared in 0.01 mbar oxygen. In contrast, the formation of twins was observed for higher . A detailed microstructural analysis indicates that the sample preparation in low prevents a preferential growth of columnar grains within the BZTO layers and leads to smoother film surfaces. BZTO thin films deposited with optimized deposition parameters show characteristic ferroelectric polarization behavior. The saturation polarization at room temperature declines with increasing Zr content and the characteristic ferroelectric hysteresis diminishes. Temperature-depended measurements of the relative permittivity reveal the existence of a broad transition range and a significant shift of the phase transition temperature to lower values for increasing Zr content.

Microelectronic substrates like silicon, alumina and LTCC (Low Temperature Cofired Ceramics) allow for high robustness and reliability, 3D packaging (electrical connection, channels, cavities and membranes) as well as integration and application of electronic components whereas piezoceramic materials offer sensor and actuator operations. To combine the advantages of both, integrated solutions are of great interest. This paper deals with two approaches of monolithic integration, (i) screen printing of piezoceramic thick films on microelectronic substrates and subsequent post firing and (ii) integration of pre-fired piezoceramic components into green LTCC multilayer packages and subsequent sintering. Functionality of smart microsystems not only depends on the outer design and construction but to a great part on interaction of substrate and piezoceramic material properties. A thorough choice of materials as well as the understanding and prevention of chemical reactions are necessary to build effective systems.

Structural Health Monitoring (SHM) systems allow for permanent and online characterization of condition and health of structural components. We introduce novel SHM modules fully based on inorganic materials which show a distinguished improve of temperature and chemical stability compared to known piezoceramic-polymer-patches. Using ceramic multilayer technology lead zirconate titanate (PZT) discs are integrated into a package of low temperature cofired ceramic (LTCC) sheets enabling for the production of compact ultrasonic transducers with integrated electronic circuits and signal processing units.

In this paper the challenging manufacturing process of a deformable mirror for the wave front correction of a high energy laser is described. During this process the LTCC membrane as the base component with integrated sensors must endure several postfire processes at temperatures of up to 900°C without any degradation of the sensors' characteristics. In order to optimize the sensors, various combinations of resistor and conductor pastes and different geometries are characterized. The usability and the performance of the sensor elements after temperature treatment are investigated by measuring the resistance and its resistance temperature characteristic.

This paper reports on new results of the development of a unimorph laser beam shaping mirror based on Low Temperature Cofired Ceramics (LTCC). The deformable mirror is actuated by a side screen printed piezoceramic thick film based on lead zirconate titanate (PZT). The reflective surface is electroplated copper that is diamond machined to flatten the surface. We introduce the solder jet bumbing fixation technology to mount the deformable mirror into a metallic mounting. This assembling technology introduces very little energy input and thus also very little deformation into the mirror. The material of the mounting is CE7 that is especially thermal adapted to the deformable mirror. We will present results on deflection and resonance frequency for two different mirror designs.

LTCC technology has recently been used for microfluidic elements, e.g. channels, cavities and other passive fluidic components. However, microfluidic systems having enhanced functionality, e.g. differential pressure sensors, dosing devices and pumps, require active components that include electrically driven actuators. Up to now, only piezo-cantilevers, electromagnetic and thermo-pneumatic actuators have been engineered for the LTCC integration [1–4]. Due to their specific properties, they are not suitable for all applications that require an actuator. Therefore, a review on actuators capable of being integrated in LTCC is given. On the one hand, the actuators are compared according to their functional properties, e.g. stroke and switching energy, so that actuators can be figured out that fulfil the requirements of a microfluidic system to be designed. On the other hand, the technological challenges to be coped with in the integration of the actuators are listed. Both the functional properties of an actuator and the possibility to integrate it decide on the suitability for a specific application. Using our evaluation method, we introduced actuators for two different microfluidic applications, a piezo-electrically controlled throttle for a DMFC (Direct Methanol Fuel Cell) application and an electrostatic valve for a differential pressure sensor.

This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number of degrees of freedom from silicon wafers with bimorph piezoelectric actuation. The mirror may be used on its own, or as a segment of a larger mirror. The typical size of one segment is 100 to 200 mm; the production process relies on silicon wafers and thick film piezoelectric material deposition technology; it is able to lead to an actuation pitch of the order of 5 mm, and the manufacturing costs appear to grow only slowly with the number of degrees of freedom in the adaptive optics.

This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number of degrees of freedom, by assembling segmented silicon mirrors with bimorph piezoelectric actuation. The production process relies on silicon wafers and thick film PZT deposition technology; it is able to lead to an actuation pitch of the order of 5 mm, and the manufacturing costs appear to grow only slowly (linearly or less) with the number of degrees of freedom in the adaptive optics.

Al2O3, silicon and low temperature cofired ceramics (LTCC) are key functional materials, forming the substrate basis in microsystems technologies. They allow for three dimensional component integration, high robustness and excellent reliability. The combination of these substrate materials with piezoelectric films offer advanced sensor, actuator and ultrasonic transducer solutions which open up new fields of applications. We developed a PZT thick film paste with excellent dielectric and electromechanical properties. In combination with special electrode and barrier layers a technology was achieved allowing for the development of custom products.

PZT thick films with thicknesses between 5 and 150 μm are of great interest for microsystems applications where direct coating onto microelectronic substrates and high electromechanical performance are required. Dense PZT thick films have been obtained by combining a PZT-PMN powder with a low melting point glass and the eutectic forming oxides Bi2O3 and ZnO. Densification is due to transient liquid phase formation with additional incorporation of cations into the growing PZT grains during sintering. PZT thick films prepared by this method show excellent dielectric, ferroelectric and piezoelectric properties. They have been applied on various substrates, like Al2O3, ZrO2, Low Temperature Cofired Ceramics (LTCC) and silicon wafers which are basis materials for microsystems technology. The influence of the substrate material on the PZT thick film properties and the role of buffer layers will be discussed.

This paper gives a summary on advanced piezocomposite transducers and the perspective of their applications in the field of smart structures, health monitoring and diagnostics. At present, three different low profile piezocomposite actuator types are commercially available. The designs are arising from the R&D work at MIT in the years 1991/92 funded by the US Department of Defence. Smart Material is manufacturing Macro Fiber Composites (MFC), licensed by NASA in a full-scale production. A new MFC- design using the 3-1 coupling has been developed, recently. It allows for the reduction of drive voltage down to 360 V. Fraunhofer IKTS focused its development on custom shape composites making use of PZT tubes and plates. New actuator devices for active interfaces have been introduced for the first time. All piezocomposite design forms show different performance data, which are summarised in the present paper to provide design engineers with necessary informations in view of intended applications.