High output performance of piezoelectric energy harvesters using epitaxial Pb(Zr, Ti)O₃ thin film grown on Si substrate

For a high power density in piezoelectric energy harvesters, both a large direct piezoelectric coefficient (e_31,f) and a small relative permittivity constant (ε_r,33) are required. This study proposed an energy harvesting device made of an epitaxial Pb(Zr, Ti)O₃ (PZT) thin film grown on a Si substrate. The epitaxial PZT thin film is deposited on the Si substrate by RF magnetron sputtering. The epitaxial PZT thin film grown on Si substrate has a ε_r,33 constant of 318. The output voltage as a function of input displacement was measured using a shaker to evaluate the direct e_31,f coefficients and energy harvester output characteristics. According to the figure of merit defined as (e_31,f)²/ε₀ε_r,33, the epitaxial PZT/Si cantilever is 32 GPa. At a resonant frequency of 373 Hz under an acceleration of 11 m/s², the epitaxial PZT/Si cantilever has a high output power of 40.93 μW and power density of 108.3 μW/cm²/g² without any damage, which is very promising for high power energy harvester applications.