High-power piezoelectric energy harvester produced using [001]-textured (Na, K)NbO3-based lead-free piezoceramics

High-power piezoelectric energy harvesters (PEHs) require piezoceramics with a large k(p) and d(33) but small epsilon(T)(33)/epsilon(0) values. The [0 0 1]-textured 0.96(Na, K)(Nb1-xSbx)-0.04SrZrO(3) piezoceramics (x = 0.025 and 0.045) exhibited the improved electromechanical coupling factor (k(p)) and piezoelectric charge constant (d(33)); however, the increase of dielectric constant (epsilon(T)(33)/epsilon(0)) was not significant. Further, the textured piezoceramic with x = 0.045 shows the large d(33) x g(33) value of 21.5 pm(2)/N, where g(33) is piezoelectric voltage constant, indicating that texturing is a good technique to fabricate the piezoceramics for PEH. The impedance curve of the PEH consisting of the metal substrate and textured piezoceramic shows a piezoelectric resonance peak at a low frequency, which is the same as the mechanical resonance frequency of the PEH. Hence, the PEH can be considered a piezoelectric material. The figure of merit of the PEH was determined using the mechanical quality and electromechanical coupling factor calculated from the impedance curve of the PEH. A large power output of 1.7 mW was obtained from the type-1 PEH at the resonance frequency produced using the textured thick film (x = 0.045). Hence, this PEH can be used as a permanent power source for microelectronic devices in the Internet of Things.