Dielectric and piezoelectric properties of (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 lead-free ceramics for piezoelectric energy harvesters

The piezoelectric and dielectric properties of the (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 (x=0.12, 0.14, 0.18, 0.20 and 0.30) lead-free ceramics were investigated. Specimens were prepared by the conventional mixed oxide method and sintered at 1170 °C in air. Scanning electron microscopy indicated that increasing x from 0.12 to 0.30 causes a decrease in the grain size. The (1−x)(Bi,Na)TiO3–x(Bi,K)TiO3 ceramics shows a homogeneous microstructure and excellent dielectric and piezoelectric properties. Specimens with optimum composition showed a piezoelectric charge constant d33 of 166 pC/N, an electromechanical coupling factor kp of 0.5, a dielectric constant εr of 1591.32 at 1 kHz and generated power output of 37.49 nW/cm2.