Effect of piezoelectric layer thickness and poling conditions on the performance of cantilever piezoelectric energy harvesters on Ni foils

Lead zirconate titanate (PZT) films grown on flexible Ni foils were utilized to explore the effects of thickness and poling conditions on the performance of mechanical energy harvesters. In the case of Mn doped 1μm thick (001) oriented sol-gel PZT (52/48) films on Ni foil, the dielectric constant and |e31,f| are 390 at 10 kHz and 11.3 C/m2, respectively, after hot poling. This film has a large figure of merit (e31,f2εr), of around 0.4 C2/m4, for piezoelectric energy harvesting. Unimorph cantilever beams were easily fabricated from PZT films on Ni foil using simple mechanical cutting. The maximum power increases from 12 to 60 μW as the thickness of Nb doped PZT film increases from 1 to 3 μm at resonance frequency (∼70 Hz) at 0.5 G. The optimum poling condition (150 °C, at 3 times the coercive for 15 min) enhanced the voltage and power output of the cantilever harvester prepared using (1 μm) PZT films on Ni foil. It was found that the power performance of harvesters strongly depends on the thickness of the film with resonant harvesters of the same footprint area (0.385 cm2) using PZT films on Ni foils.