Characterization of piezoelectric material for micro thermal harvesters

Abstract

This paper presents the first realizations of a novel concept for thermal energy harvesting at micro scale. The devices proposed here are based on a two-step transduction combining thermo-mechanical and piezoelectric conversion. In this contribution, we present for the first time results on micro fabricated structures with integrated piezoelectric layers, focusing mainly on the characterization of the piezoelectric material. The process flow to get a bilayered bistable structure is briefly described, highlighting the way how to control the initial deflection. The characterization of the piezoelectric thin film is presented then. The e31,f coefficient is measured in both sensor and actuator mode and is found to be equal to -0,91 C.m-2 in both configurations. This value, close to the state-of-the-art, is very promising for the future thermal harvesting applications. Finally the buckling of a structure actuated by a voltage was observed and the corresponding displacement measured by laser interferometry.