Characterization of piezoelectric material for micro thermal harvesters

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 e(31,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

Fabrication of bilayer plate for a micro thermal energy harvester

International audienceThe fabrication process of a micro device introducing a new concept for thermal energy harvesting based on a two-step conversion is presented in this paper. An initially curved bilayer plate, which one of the layers is piezoelectric, is in contact with a hot source. The thermo-mechanical behavior leading to the buckling of the device is illustrated by finite elements simulations. The stresses generated by the buckling will create electrical charges through the piezoelectric effect, the piezoelectric layer being directly integrated to the device. The process flow for the employed bilayer structure aluminum nitride - aluminum will be detailed. The initial deflection of the plate was controlled by fabrication parameters during the thin films deposition. The first thermo-mechanical buckling was observed

Electrical characterization of a buckling thermal Energy harvester

International audienceThis paper presents the electrical characterizations of a novel concept for thermalenergy harvesting at micro scale. The devices presented here are based on a two-steptransduction combining thermo-mechanical and piezoelectric conversion. The piezoelectriclayer is directly integrated into a buckling bilayer plate made of aluminium and aluminiumnitride. For the first time, we have characterized the structures electrically and we haveinvestigated their output power during the buckling. Firstly, we have used an insulating tip tomake the plate buckle in order to have an estimation of the output power due to piezoelectriccontribution only, and to eliminate any pyroelectric contribution that might be present duringthe thermal actuation. Then, we heated up the structure and we collected the output signal withan instrumentation amplifier in order to measure the voltage generated during the buckling.The output power during the mechanical and the thermal buckling is compared in the paper

Electrical characterization of a buckling thermal energy harvester

This paper presents the electrical characterizations of a novel concept for thermal energy harvesting at micro scale. The devices presented here are based on a two-step transduction combining thermo-mechanical and piezoelectric conversion. The piezoelectric layer is directly integrated into a buckling bilayer plate made of aluminium and aluminium nitride. For the first time, we have characterized the structures electrically and we have investigated their output power during the buckling. Firstly, we have used an insulating tip to make the plate buckle in order to have an estimation of the output power due to piezoelectric contribution only, and to eliminate any pyroelectric contribution that might be present during the thermal actuation. Then, we heated up the structure and we collected the output signal with an instrumentation amplifier in order to measure the voltage generated during the buckling. The output power during the mechanical and the thermal buckling is compared in the paper

Modeling of the thermo-mechanical efficiency of the bimetalstrip heat engines

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