EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Piezoelectric composites have wide ranging potential for advanced electronic devices, particularly as sensors, energy harvesters, and actuators, and have a number of advantages over single phase or monolithic piezoelectric ceramics. Introducing a low permittivity second phase into a piezoceramic leads to significant reductions in the bulk permittivity of the material, which is beneficial in terms of figures of merit for harvesting and sensing. By tailoring microstructures to optimise electric and mechanical field distributions during poling and device operation, the decreases in the piezoelectric coefficient commonly associated with decreasing the volume of active material can be avoided, leading to large increases in energy harvesting and sensing performance. Mechanical properties can also be tailored to yield improved impedance matching, thereby enabling more efficient transfer of mechanical energy into the active material, as well as providing a degree of flexibility not otherwise achievable in monolithic ceramic systems.

Despite recent advances in the processing technology of piezoceramic-based composites within a research environment, commercial manufacturing approaches still tend to involve either dice-and-fill of monoliths or arrange-and-fill of fibres, which are relatively inefficient from a waste and labour perspective. Newer techniques such as freeze casting and additive manufacturing offer the opportunity to create bespoke piezoelectric composites with electromechanical properties matched to their desired applications, but further research is required to fully understand the links between processing, structure and functional properties, as well as lifetime performance, before they become adopted in industry. This talk will focus on new directions in the fabrication of piezoelectric composites and the latest understanding of structure-property relationships of these materials across a range of length scales from ferroelectric domain through to macrostructure.