@article{58510,
abstract = {{Today’s ultrasonic transducers find broad application in diverse technology branches and most often cannot be replaced by other actuators. They are typically based on lead-containing piezoelectric ceramics. These should be replaced for environmental and health issues by lead-free alternatives. Multiple material alternatives are already known, but there is a lack of information about their technological readiness level. To fill this gap, a small series of prestressed longitudinally vibrating transducers was set up with a standard PZT material and two lead-free variants within this study. The entire process for building the transducers is documented: characteristics of individual ring ceramics, burn-in results, and free vibration and characteristics under load are shown. The main result is that the investigated lead-free materials are ready to use within ultrasonic bolted Langevin transducers (BLTs) for medium-power applications, when the geometrical setup of the transducer is adopted. Since lead-free ceramics need higher voltages to achieve the same power level, the driving electronics or the mechanical setup must be altered specifically for each material. Lower self-heating of the lead-free materials might be attractive for heat-sensitive processes.}},
author = {{Scheidemann, Claus and Bornmann, Peter and Littmann, Walter and Hemsel, Tobias}},
issn = {{2076-0825}},
journal = {{Actuators}},
number = {{2}},
publisher = {{MDPI AG}},
title = {{{Lead-Free Ceramics in Prestressed Ultrasonic Transducers}}},
doi = {{10.3390/act14020055}},
volume = {{14}},
year = {{2025}},
}
@inproceedings{62300,
author = {{Claes, Leander and Hölscher, Jonas and Friesen, Olga and Scheidemann, Claus and Hemsel, Tobias and Henning, Bernd}},
booktitle = {{2025 International Congress on Ultrasonics}},
pages = {{142–145}},
publisher = {{AMA Service GmbH}},
title = {{{Estimation of third order elastic constants of piezoceramics using DC biased impedance measurements}}},
doi = {{10.5162/ultrasonic2025/a18-a6}},
year = {{2025}},
}
@inproceedings{64798,
abstract = {{Lead-containing piezoelectric ceramics are still the base for today’s ultrasonic transducers used in broad applications. This is partly due to missing powerful lead-free piezoelectric ceramic parts in the commercial market. There has been much research on lead-free materials but developing them into marketable parts seems to be an ongoing process. The actual exemption of ROHS has expired, but as the new exemption has already been requested, ceramic suppliers keep on selling lead containing products. Nevertheless, these should be replaced by lead-free alternatives for environmental and health issues.
This contribution focuses on exploring the technological readiness level of lead-free hard piezoceramics for prestressed ultrasonic transducers. A small series of bolted Langevin transducers was set up with standard PZT material and three commercial lead-free variants. Results of the building process from individual ring ceramic characteristics to transducer load tests are presented. The main finding of this study is that the lead-free materials technically can compete with the standard PZT for medium-power applications. Some adaptations in the ultrasonic system must be done: the geometry must be altered to fit resonance frequency, and higher voltages or thinner ceramics are needed to achieve the same vibration level at low load. For reaching same power, the volume of lead-free ceramics must be 1.5 to 3 times larger. As already promoted in literature, mechanical losses at high vibration levels are smaller for the lead-free materials. This might help to argument lead-free piezoelectric materials in some applications.
References
1. Directive 2011/65/EU of the European Parliament and of the Council of 8 June 2011 on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment. EUR-Lex Document 02011L0065-20240801. Available online: http://data.europa.eu/eli/dir/2011/65/2024-08-01 (accessed on 24 January 2025).
2. Langevin, P. (1918) Method and Apparatus for Transmitting and Receiving Submarine Elastic Waves Using the Piezoelectric Properties of Quartz. French Patent Office; Patent No. FR505703.
3. Hemsel, T.; Twiefel, J. (2023) Piezoelectric Ultrasonic Power Transducers. In Encyclopedia of Materials: Electronics; Academic Press: Oxford, UK; pp. 276–285. https://doi.org/10.1016/b978-0-12-819728-8.00047-4.
4. ATHENA Technologie Beratung GmbH (2025) Description of Ultrasound Generator. Available online: http://shop.myathena.de/epages/12074748.sf/de_DE/?ObjectPath=/Shops/12074748/Products/AM200 (accessed on 13 January 2025).
5. Littmann, W.; Hemsel, T.; Kauczor, C.; Wallaschek, J.; Sinha, W. (2003) Load-adaptive phase-controller for resonant driven piezoelectric devices. Proc. World Congr. Ultrason. 2003, 48, 547–550.
6. Scheidemann, C., Bornmann, P., Littmann, W., & Hemsel, T. (2025). Lead-Free Ceramics in Prestressed Ultrasonic Transducers. Actuators, 14(2), 55. https://doi.org/10.3390/act14020055
}},
author = {{Scheidemann, Claus and Bornmann, Peter and Littmann, Walter and Hemsel, Tobias}},
keywords = {{lead free piezoelectric ceramics, bolted Langevin transducer, medium power ultrasound.}},
location = {{Vilnius, Lithuania}},
title = {{{Bolted Langevin transducers with leadfree piezoelectric ceramics}}},
year = {{2025}},
}
@inproceedings{64800,
abstract = {{Intensive ultrasonic cleaning of surfaces by means of a lead-free ultrasonic transducer with focusing sonotrode
Ultrasonic cleaning baths are probably a coincidental development: After underwater sonars had already been successfully used to detect submarines before 1920, it was probably observed in this environment that the ultrasonic oscillators not only showed a self-cleaning effect but also cavitation damage. At the beginning of the 1950s, the first ultrasonic cleaning devices finally came onto the market. Today, the range of applications ranges from household appliances for jewellery and eyewear cleaning to classic cleaning baths for metal parts and systems for cleaning highly sensitive electronic components. There is a certain gap in handheld, mobile cleaning equipment. Although devices for spot cleaning of textiles are known, the cleaning effect is usually low.
Due to the directive 2011/65/EU on the restriction of the use of hazardous substances in electrical and electronic equipment (RoHS) [1] lead should no longer be used in technical devices. As today’s standard ceramics for medium and high-power ultrasonic transducers typically contain lead, there is a need to explore the use of lead-free ceramics in this field. Honda [2] already offers a cleaning transducer based on lead-free piezoelectric ceramics, but it is designed to be used in cleaning baths.
This article presents the model-based development of a highly innovative ultrasonic cleaner. On the one hand, lead-free piezoelectric ceramics are used, and on the other hand, a special sonotrode has been developed that concentrates the sound in such a way that a strong cavitation and thus cleaning effect is achieved with comparatively low power in a short time. Coupled field finite element method was used to find an appropriate geometry for the focussing sonotrode. The comparison of simulation and measurement results shows that the lead-free piezoceramics used do their job well and can keep up with standard ceramics, but more ceramic volume is needed to achieve same power. An advanced control concept was elaborated to ensure continuous hard cavitation at varying distances between the sonotrode and the part to be cleaned. Cleaning results for different surfaces and contaminations are presented. The concept of the focusing sonotrode shows that a convincing cleaning result can be achieved even with low power and in short time, provided that the oscillation system and control electronics are suitably coordinated.
References
[1] http://data.europa.eu/eli/dir/2011/65/2024-08-01
[2] https://en.honda-el.co.jp/product/ceramics/lineup/lead_off/lead-off
}},
author = {{Hemsel, Tobias and Scheidemann, Claus and Bornmann, Peter and Littmann, Walter and Sextro, Walter}},
location = {{Paderborn, Germany}},
title = {{{Intensive ultrasonic cleaning of surfaces by means of lead-free ultrasonic transducer with focussing sonotrode}}},
year = {{2025}},
}
@inproceedings{61755,
author = {{Scheidemann, Claus and Hemsel, Tobias and Sextro, Walter}},
location = {{Vilnius, Lithuania}},
title = {{{Time dependent material characteristics of prestressed piezoelectric ceramics in langevin transducers}}},
year = {{2025}},
}
@inproceedings{61757,
author = {{Scheidemann, Claus and Porzenheim, Julius and Hemsel, Tobias and Sextro, Walter}},
location = {{Paderborn, Germany}},
title = {{{Investigation of the Setting Behaviour of Mechanically Biased Piezoelectric Ultrasonic Transducers}}},
year = {{2025}},
}
@inproceedings{62299,
author = {{Friesen, Olga and Scheidemann, Claus and Claes, Leander and Hemsel, Tobias and Henning, Bernd}},
booktitle = {{2025 International Congress on Ultrasonics}},
pages = {{138–141}},
publisher = {{AMA Service GmbH}},
title = {{{Sensitivity Analysis and Material Parameter Estimation of a Pre-Stressed Langevin Transducer}}},
doi = {{10.5162/ultrasonic2025/a18-a4}},
year = {{2025}},
}
@inproceedings{64803,
abstract = {{Nowadays ultrasound technology is established in various fields of application like industrial production or medical technology. Besides high power ultrasound applications like ultrasonic cleaning and ultrasonic welding, which are often not strongly restricted regarding their weight, costs, and construction space, there are many applications in the low to medium power range like handheld surgical instruments, medical inhalers, or ultrasonic cutters. For the latter there is often a strong demand for low weight and construction space and low costs to be competitive in mass production. Another challenge that arises from the RoHS-directive [1] is, that new ultrasonic devices should avoid the use of lead-containing PZT-materials. Against this background there is a demand for lead-free, small and lightweight and cost-effective ultrasonic transducers.
In many of the above-mentioned applications, pre-stressed Bolted-Langevine-Transducers (BLT) based on lead-containing PZT-materials are established to generate ultrasonic vibrations. These are quite advantageous in many ways and can be built tailored to each application and even for high power of thousands of watts. But due to the required steps during their manufacturing process (machining parts, assembly, pre-stressing, frequency tuning, …), these transducers remain expensive. Furthermore, due to the operation in resonance, the construction space of these transducers is linked to their wavelength and cannot be reduced remarkably.
For these reasons, our aim is to present an innovative lead-free ultrasonic transducer for low to medium power applications, that is based on bending vibrations instead of longitudinal vibrations. This design enables to build very small transducers. Furthermore, due to their simple construction, these transducers can be built at low manufacturing costs and are well suited for industrial mass production. The use of lead-free piezoelectric materials makes this transducer design ready for future applications.
In our contribution we will present the model-based design of a lead-free 30 kHz bending transducer for applications up to 10 W. Furthermore, the comprehensive experimental analysis of this transducer-prototype in applications like mist generation or ultrasonic drilling will be presented. The results will be compared to a PZT-based bending transducer and a classical BLT to show the potential and limits of these kind of transducers and lead-free materials.
}},
author = {{Bornmann, Peter and Littmann, Walter and Scheidemann, Claus and Hemsel, Tobias}},
location = {{Paderborn, Germany}},
title = {{{Innovative lead-free ultrasonic bending transducers for low to medium power applications}}},
year = {{2025}},
}
@inproceedings{64802,
abstract = {{Power ultrasonic actuators are used in various industrial, automotive and medical applications. Examples are ultrasonic welding of plastics or metal, surgery processes like cutting of tissue or bone, and the excitation of cavitation in liquids for ultrasonic cleaning. From a physical point of view, many of these processes are characterised by non-constant damping conditions for the ultrasonic actuators, since the systems need to be driven in unloaded as well as in high-loaded states. To get high power output, the piezoelectric actuators are usually driven in or near resonance at precisely defined vibration amplitudes. This is a quite complicated task especially if cost or mass optimized PZT transducers are used or if lead-free piezoelectric ceramics are applied to replace lead-containing materials. In particular the sudden change between loading states is very challenging for electronic excitation and control. The present contribution gives insight into typical problems that may arise in context with sudden load-changes during operation, e.g. uncontrolled jumps in voltage and velocity amplitudes. Measurements on ultrasonic power actuators being abruptly immersed into water at high amplitude are discussed for illustration. Observations during spontaneous load-changes are explained, and it is shown that several problems may be defused by driving the actuators in antiresonance or using a particular driving point in-between resonance and antiresonance (“falling edge control”). The different control strategies are investigated always using just one single hardware.}},
author = {{Littmann, Walter and Bornmann, Peter and Hemsel, Tobias and Scheidemann, Claus}},
location = {{Paderborn, Germany}},
title = {{{Power ultrasonic actuators with suddenly changing loads: How to control the amplitudes in resonance, antiresonance, or in-between}}},
year = {{2025}},
}
@article{57467,
abstract = {{Additive manufacturing of metallic components often results in the formation of columnar grain structures aligned along the build direction. These elongated grains can introduce anisotropy, negatively impacting the mechanical properties of the components. This study aimed to achieve controlled solidification with a fine-grained microstructure to enhance the mechanical performance of printed parts. Stainless steel 316L was used as the test material. High-intensity ultrasound was applied during the direct energy deposition (DED) process to inhibit the formation of columnar grains. The investigation emphasized the importance of amplitude changes of the ultrasound wave as the system’s geometry continuously evolves with the addition of multiple layers and assessed how these changes influence the grain size and distribution. Initial tests revealed significant amplitude fluctuations during layer deposition, highlighting the impact of layer deposition on process uniformity. The mechanical results demonstrated that the application of ultrasound effectively refined the grain structure, leading to a 15% increase in tensile strength compared to conventionally additively manufactured samples.}},
author = {{Lehnert, Dennis and Bödger, Christian and Pabel, Philipp and Scheidemann, Claus and Hemsel, Tobias and Gnaase, Stefan and Kostka, David and Tröster, Thomas}},
issn = {{2073-4352}},
journal = {{Crystals}},
number = {{11}},
publisher = {{MDPI AG}},
title = {{{The Influence of Ultrasonic Irradiation of a 316L Weld Pool Produced by DED on the Mechanical Properties of the Produced Component}}},
doi = {{10.3390/cryst14111001}},
volume = {{14}},
year = {{2024}},
}
@inproceedings{56834,
author = {{Friesen, Olga and Claes, Leander and Scheidemann, Claus and Feldmann, Nadine and Hemsel, Tobias and Henning, Bernd}},
booktitle = {{2023 International Congress on Ultrasonics, Beijing, China}},
issn = {{1742-6596}},
pages = {{012125}},
publisher = {{IOP Publishing}},
title = {{{Estimation of temperature-dependent piezoelectric material parameters using ring-shaped specimens}}},
doi = {{10.1088/1742-6596/2822/1/012125}},
volume = {{2822}},
year = {{2024}},
}
@inproceedings{61756,
author = {{Scheidemann, Claus and Hemsel, Tobias and Sextro, Walter}},
location = {{Hannover, Germany}},
title = {{{Characteristic behavior of lead-free and lead-containing piezo ring ceramics in ultrasonic transducers}}},
year = {{2024}},
}
@inproceedings{51119,
author = {{Scheidemann, Claus and Hagedorn, Oliver Ernst Caspar and Hemsel, Tobias and Sextro, Walter}},
location = {{Jeju, Korea}},
title = {{{Experimental Investigation of Bond Formation and Wire Deformation in the Ultrasonic Wire Bonding Process}}},
year = {{2023}},
}
@inproceedings{47234,
author = {{Sehlmeyer, Birte and Kampmann, Rebecca and Scheidemann, Claus and Hemsel, Tobias and Getzlaff, Mathias }},
booktitle = {{Frühjahrstagung 2023, Sektion Kondensierte Materie (SKM)}},
location = {{Dresden}},
title = {{{Burst Mode of Ultrasonic Resonant Oscillations for Stimulation and Destruction of Tumor Cells}}},
year = {{2023}},
}
@inproceedings{47235,
author = {{Kampmann, Rebecca and Sehlmeyer, Birte and Scheidemann, Claus and Hemsel, Tobias and Getzlaff, Mathias}},
booktitle = {{Frühjahrstagung 2023, Sektion Kondensierte Marterie (SKM)}},
location = {{Dresden}},
title = {{{Burst Mode Characteristics of an Ultrasonic Transducer for Treatment of Cancer Cells}}},
year = {{2023}},
}
@inproceedings{51117,
author = {{Scheidemann, Claus and Hemsel, Tobias and Friesen, Olga and Claes, Leander and Sextro, Walter}},
location = {{Jeju, Korea}},
title = {{{Influence of Temperature and Pre-Stress on the Piezoelectric Material Behavior of Ring-Shaped Ceramics}}},
year = {{2023}},
}
@techreport{52045,
author = {{Scheidemann, Claus and Hemsel, Tobias and Sextro, Walter}},
publisher = {{LibreCat University}},
title = {{{Modellbasierte Ermittlung optimaler Prozessparameter für neuartige Ultraschallbondverbindungen}}},
doi = {{10.2314/KXP:1879655276}},
year = {{2022}},
}
@inproceedings{34104,
abstract = {{ue to the constantly growing energy demand of power electronics and the need to reduce the size of electronic components like power modules for e-mobility, new challenges arise for ultrasonic wire bonding: the electrical connection must endure higher thermal and mechanical stress while the connecting partners become more sensitive or require more energy to get bonded. Past investigations have shown already that multi-dimensional ultrasonic bonding and welding yield the same or even better bond quality while reducing the load on the components. This contribution is intended to show whether multidi-mensional thick wire bonding is a promising concept to over-come the new challenges. The focus is on experimental investi-gations of different bond tool trajectories in ultrasonic wire bonding of aluminum and copper wire on DCB's and chips. The bond quality is analyzed by shear tests, microsections and, in the case of aluminum bonding, by a new machine learning method for an objective automated evaluation of the sheared area.}},
author = {{Scheidemann, Claus and Kirsch, Olaf and Hemsel, Tobias and Sextro, Walter}},
booktitle = {{2022 IEEE 9th Electronics System-Integration Technology Conference (ESTC)}},
publisher = {{IEEE}},
title = {{{Experimental Investigation of Multidimensional Ultrasonic Heavy Wire Bonding}}},
doi = {{10.1109/estc55720.2022.9939478}},
year = {{2022}},
}
@inproceedings{25265,
abstract = {{Waveguide-based methods can be used for the non-destructive determination of acoustic material parameters. One of these methods is based on transmission measurements of cylindrical polymeric specimens. Here, the experimental setup consists of two transducers, which excite and receive the waveguide modes at the faces of the cylinder. The measurement, as well as a forward model, are used to determine material parameters of the polymeric specimen in an inverse approach.
1-3 piezoelectric composites are used as an active element because they can be approximated by a thickness vibration only. This allows an easy identification of Mason model parameters to characterise the transducers’ vibration behaviour.
However, sensitivity analysis shows a high uncertainty in the determination of the mechanical shear parameters due to the uniform excitation. To increase the sensitivity to these shear motions, arbitrary excitations were investigated by means of numerical simulation.
In order to be able to realise the determined optimal excitation, new transducer prototypes were designed. By subdividing the electrodes of the active element, for example, ring-shaped excitation is feasible. Furthermore, it can be shown that modelling these transducers with a one-dimensional Mason model is sufficient.}},
author = {{Dreiling, Dmitrij and Itner, Dominik and Feldmann, Nadine and Scheidemann, Claus and Gravenkamp, Hauke and Henning, Bernd}},
booktitle = {{Fortschritte der Akustik - DAGA 2021}},
location = {{Wien}},
publisher = {{Deutsche Gesellschaft für Akustik e.V. (DEGA)}},
title = {{{Application and modelling of ultrasonic transducers using 1-3 piezoelectric composites with structured electrodes}}},
year = {{2021}},
}
@inproceedings{17355,
abstract = {{Ultrasonic wire bonding is a process to form electrical connections in electronics well established industry. Typically, a clamping tool is pressed on the wire and forced to vibrate at relative high frequency 40 to 100 kHz. The ultrasonic vibration is transmitted through the wire into the interface between wire and substrate. Due to frictional processes, contamination like oxide layers are removed from the contact zone, the surface roughness is reduced, and with increasing bond duration an metallic connection of wire and substrate is established. It is known that the amount of ultrasonic energy over time directly influences the strength and reliability of the bond connection, but the determination of optimum bond parameters is still a challenging experimental task. For this, in the past different model approaches have been presented, to calculate the bond quality by simulation. Measuring the friction between wire and substrate to validate these models is a challenging task at ultrasonic bonding frequency. Therefore a versatile test rig for bonding experiments at frequencies lower than 1 kHz is setup to get detailed insight into the different phases of the connection process. It includes a piezoelectric force sensor for the measurement of the three-dimensional process forces, an electrodynamic shaker for the vibration excitation and a conventional tension-compression testing machine to apply the bond normal force. Using this test rig, it is possible to observe the different phases of bond formation in detail, validate and enhance existing models and finally optimize bond parameters for different processes.}},
author = {{Schemmel, Reinhard and Scheidemann, Claus and Hemsel, Tobias and Kirsch, Olaf and Sextro, Walter}},
booktitle = {{CIPS 2020; 11th International Conference on Integrated Power Electronics Systems}},
pages = {{1--6}},
title = {{{Experimental analysis and modelling of bond formation in ultrasonic heavy wire bonding}}},
year = {{2020}},
}