Highly Coupled and Low Frequency Vibrational Energy Harvester Using Lithium Niobate on Silicon

LiNbO3 has been little studied for the piezoelectric energy harvesting applications. Although it is a cheap piezoelectric material without lead and toxic elements, it beneficiates of technological maturity in single crystal fabrication for optical and acoustic applications. In this Letter, we propose to investigate a (YXlt)/128°/90° LiNbO3 cut as it offers a transverse piezoelectric coupling of k23 = 0.49, which is comparable to that of commonly used PZT ceramics. A flexible beam of 65 mm length and a tip mass made of a LiNbO3 thick film bonded on silicon were studied under 0.1 g sinusoidal acceleration. The beam presented an open-circuit resonance frequency of 105.9 Hz and a displacement up to 1.5 mm. In the frame of a single degree of freedom lumped model with a rectifying bridge, the electromechanical coupling of the device (km2), the figure of merit km2Q, and the normalized average power density were compared to both Pb-based and Pb-free current devices. The generated power density by our device was 965 μW/cm2/g2, which is among the highest reported values compared to both Pb- and Pb-free vibrational harvesting devices.