High‐power piezoelectric energy harvester produced using [0 0 1]‐textured (Na, K)NbO <sub>3</sub> ‐based lead‐free piezoceramics
Sun‐Woo Kim, Seok‐June Chae, Dae‐Su Kim, Jong–Un Woo, Eun‐Ji Kim, Su‐Hwan Go, Jae‐Min Eum, Hyung‐Won Kang, Seung Ho Han, Sahn Nahm
Abstract
Abstract High‐power piezoelectric energy harvesters (PEHs) require piezoceramics with a large k p and d 33 but small ε T 33 / ε 0 values. The [0 0 1]‐textured 0.96(Na, K)(Nb 1− x Sb x )–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 ( ε T 33 / ε 0 ) was not significant. Further, the textured piezoceramic with x = 0.045 shows the large d 33 × 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.