One step densification of printed multilayers by SPS : towards new piezoelectric energy harvester MEMS

Autonomous electronic devices and increasing use of wireless sensors, which are more and more effective, are facing the problem of energy autonomy. This autonomy can be achieved with preliminary storage and/or energy harvesting. Hence, for 20 years, the energy harvesting research field has intensively focused on the development of new materials and their integration in micro/nanogenerators. In this research area, Micro-Electromechanical System (MEMS) energy harvesters (EH) using piezoelectric materials is one of the most promising options, because of the availability of mechanical vibrations and of the simplicity of electromechanical conversion. Piezoelectric ceramics, commonly used in various applications, are attractive for EH, and among them, Pb(Zr1-xTix)O3 (PZT), despite its lead content, remains mostly studied because of its outstanding properties. For its ceramic process, the main objectives are improved densification, cost and energy efficient processing, and integration in microgenerators. In this context, SPS sintering of printed electrode PZT piezoelectric layers supported on stainless steel substrate (SS) is highly challenging. In this chapter, after a section devoted to piezoelectric EH, the device made of screen-printed PZT layers on SS substrate is presented. Then, the authors focus on the strategy to achieve, in one step, a cantilever transducer where the printed electrode PZT and the SS substrate are co-sintered by SPS. As a first part of this ambitious objective, microstructural, dielectric, and piezoelectric properties of the PZT pellet densified by SPS are presented and compared to PZT printed layers conventionally sintered