Fabrication of Lead-free (K0.5Na0.5)1−xAgxNbO3 Ferroelectric Ceramics and Their Dielectric Properties

In this study, lead-free (K 0.5 Na 0.5 ) 1− x Ag x NbO 3 ( x = 0.00, 0.10, 0.15, 0.20, 0.25, and 0.30) ferroelectric ceramics were fabricated using solid-state synthesis without A-site and B-site manufacturing step. The (K 0.5 Na 0.5 ) 1− x Ag x NbO 3 ceramics were sintered at 1110 °C for 4 h after calcination at 800 °C for 3 h. The sintered sample was dense, and the grain size was 1.02 ~ 7.8 μm. For x ≤ 0.2, the sintered ceramic samples had a single perovskite structure. The temperature dependence of the dielectric constant in the (K 0.5 Na 0.5 ) 1− x Ag x NbO 3 was measured at 1 kHz using an LCR meter. The high dielectric constant properties could be obtained in (K 0.5 Na 0.5 ) 1− x Ag x NbO 3 ceramics. The orthorhombic-to-tetragonal phase transition temperature and ferroelectric Curie temperature decreased linearly with increasing mole fraction of the Ag content. The Curie temperature shifted from 393 °C for (K 0.5 Na 0.5 )NbO 3 ceramics to 317 °C for (K 0.5 Na 0.5 ) 0.7 Ag 0.3 NbO 3 ceramics. The maximum dielectric constant was 8930 at 330 °C in the (K 0.5 Na 0.5 ) 0.8 Ag 0.2 NbO 3 ceramics.