Thibault Dufay

Transverse piezoelectric coefficient measurement of flexible lead zirconate titanate thin films

Highly flexible lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), thin films have been realized by modified sol-gel process. The transverse piezoelectric coefficient d31 was determined from the tip displacement of bending-mode actuators made of PZT cantilever deposited onto bare or RuO2 coated aluminium substrate (16 μm thick). The influence of the thickness of ruthenium dioxide RuO2 and PZT layers was investigated for Pb(Zr0.57Ti0.43)O3. The modification of Zr/Ti ratio from 40/60 to 60/40 was done for 3 μm thick PZT thin films onto aluminium (Al) and Al/RuO2 substrates. A laser vibrometer was used to measure the beam displacement under controlled electric field. The experimental results were fitted in order to find the piezoelectric coefficient. Very large tip deflections of about 1 mm under low voltage (∼8 V) were measured for every cantilevers at the resonance frequency (∼180 Hz). For a given Zr/Ti ratio of 58/42, it was found that the addition of a 40 nm thick RuO2 interfacial layer between the aluminium substrate and the PZT layer induces a remarkable increase of the d31 coefficient by a factor of 2.7, thus corresponding to a maximal d31 value of 33 pC/N. These results make the recently developed PZT/Al thin films very attractive for both low frequency bending mode actuating applications and vibrating energy harvesting.

New process for transferring PZT thin film onto polymer substrate

This paper reports a simple, quick and cheap method for transferring Pb(Zr,Ti)O3 (PZT) thin film onto polymer substrate. To achieve a low-cost transfer process, piezoelectric thin film are deposited onto a sacrificial commercial aluminium substrate to target polymer substrate by a wet etching technique. This novel flexible piezoelectric structure was characterized to evaluate its crystal structure and its morphologic properties. This new process should allow to develop novel applications for low frequency vibrations energy harvesting.

Flexible PZT/aluminium thin films characterizations for energy harvesting at very low frequencies (∼ 1 Hz)

With the objective to harvest the airflow energy, flexible PbZrTiO3(PZT) thin films have been deposited onto ultra thin aluminium (Al) foil (16 μm).The piezoelectric properties of a PZT/aluminium cantilever have been investigated, and the measurements show d31 values around 30 pm/V. Due to use of a very lightweight substrate, a very large deflection (in the millimeter range) of the tip of the beam have been observed, which is very promising for actuators applications. In a next step, PZT/aluminium films have been encapsulated with laminated polyethylene terephthalate (PET) in order to increase the flexibility of the device. The obtained structures were subjected to sinusoidal stress at very low frequencies (0.3 to 8 Hz) and the output voltages across a resistive load have been measured and compared to the theory with a good agreement. In addition, an intermediate ruthenium dioxide (RuO2) layer has been used at the PZT/aluminium interface and its influence on the piezoelectric properties and the harvested power has been demonstrated.