Sylvia E. Gebhardt

Photo:
Sylvia E. Gebhardt
First Name:
Sylvia E.
Last Name:
Gebhardt
Bio:

Sylvia E. Gebhardt is Senior Research Scientist at the Department Smart Materials and Systems of the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden, Germany. She studied Material Science at the Technical University Bergakademie Freiberg, Germany and at Leeds University, UK. She received the Diploma degree in 1996 and was awarded a Ph.D. degree in 2000 for her thesis on development and characterization of fine-scaled 1‑3 piezocomposites for ultrasonic transducers. Her research interests are focused on the materials synthesis of ferroelectric, piezoelectric, and electrocaloric compositions as well as on the development of ceramic components based on thick films, multilayers, microstructures, fibers, and composites for capacitors, sensors, actuators, and ultrasonic transducers.

Affiliation:
Fraunhofer IKTS, Institute for Ceramic Technologies and Systems, Dresden, Germany

Advanced Technologies for the Manufacture of Future Piezoceramic Components

The trend towards complex structures or highly miniaturized devices demands for new technology solutions to manufacture piezoceramic components.

Piezoceramic thick films with typical thickness of 20-150 µm fulfil microsystems requirements for low profile and compact devices. They are of great importance for applications, where construction height is limited, outgassing has to be prevented, and complex structures are needed. Using stencil- or screen-printing technology, net-shaped structures can easily be applied together with isolation and electrode layers. Based on hybrid technology, piezoceramic function can be combined with 3D electronic packaging, semiconductor devices, and passive SMD components. Miniaturized and highly compact devices are possible, which are needed as sensors for process monitoring in context with industry 4.0 applications, actuators for optical control and ultrasonic transducers for non-destructive evaluation.

Ultrasonic imaging plays an important role in medical and material diagnostics. The demand for more precise control requires higher resolution, which can only be obtained using high-frequency ultrasonic transducers. The soft mold process developed at Fraunhofer IKTS enables the fabrication of fine-scale 1-3 piezocomposites via slip casting. The basis of this approach are master molds, which are structured by microsystems technologies. That allows a high variety of rod size, shape, spacing, and arrangement. The combination of silicon industry based micro-structuring and ceramic molding is possible through soft plastic templates taken from the master mold into which a ceramic slurry is poured and demolded after drying. Based on the technology, ultrasonic transducers with operating frequencies up to 40 MHz can be manufactured.

Piezoceramic fibers allow for the development of customized sensors, actuators, and ultrasonic transducers. Using a phase inversion process, piezoceramic fibers with diameters of 100 to 800 µm can be produced on large scale. They can be integrated into polymer matrices to build piezofiber composites. While piezocomposites with aligned fiber arrangement are advantageous for actuators and ultrasonic transducers, sensors and energy harvesters also accept random arrangement. Recent research focuses on single-fiber ultrasonic transducers for 3D-ultrasound-computer tomography (USCT) systems, where opening angle and bandwidth are enhanced compared to dice-and-fill composites.

The presentation will give an overview covering design aspects, technology, and applications of piezoceramic components beyond conventional powder pressed parts.