Advanced piezoelectric composites: development and properties

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

L5, Linnanmaa Campus

Topic of the dissertation

Advanced piezoelectric composites: development and properties

Doctoral candidate

Master of Science (Technology) Tuomo Siponkoski

Faculty and unit

University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Microelectronics Research Unit

Subject of study

Electronics Materials and Devices

Opponent

Professor Sohini Kar-Narayan, University of Cambridge, United Kingdom

Custos

Docent Jari Juuti, University of Oulu

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Advanced Piezoelectric Composites: Development and Properties

In the thesis research, two types of piezoelectric materials were developed and characterized: flexible printable ceramic-polymer composites and all-ceramic composites that can be fabricated even at room temperature.

Piezoelectric materials are very versatile, as they can be used to convert mechanical energy into electrical energy and vice versa. They are widely used in various sensors, actuators and energy harvesters. One of the most familiar applications of piezoelectric components can be found, for example, in buzzers, ultrasound imaging devices, camera stabilizers or radar sensors for vehicles.

In the dissertation, an piezoelectric composite in ink-form was developed, and it was used to fabricate flexible beams by printing techniques. It was observed that by optimizing the composition of the composite and substrate stiffness, piezoelectric properties of the printed beams could be significantly improved while maintaining the flexibility of the structure. The composition optimization was realized by adjusting the ceramic filler amount and by coating the filler particles. Stiffness of the beam structure was tuned by adding a thin metal layer to the polymer substrate or using different thin metal films as substrate.

In all-ceramic composites’ research, a new ultra-low temperature manufacturing method of ceramic composites ("upside-down" method) was developed by applying it for the first time to piezoelectric materials. The method enabled lowering the fabrication temperature from the 800–1000 °C , used in traditional all-ceramic composites, even down to room temperature. The lowest temperature was achieved with a water-soluble ceramic binder. With another, organotitanate based binder, the lowest manufacturing temperature was 300 °C. The achieved piezoelectric properties in both all-ceramic composites were comparable even to materials produced at high temperature. Piezoelectric composites with similar performance have not been successfully manufactured at these temperatures before. An accelerometer prototype was also made from one of the composite materials and its sensitivity corresponded to the values of similar type commercial sensors.

Altogether, the results achieved in the thesis pave the way for new printable piezoelectric composite materials and structural solutions broadening their application field and utilization possibilities. In addition, developed new methods brings new interesting aspects for sustainability of the all-ceramic composites, especially with respect of energy savings, while obtaining high performance.
Last updated: 7.12.2022