Dielectric properties of lead-free BNT-based ferroelectric ceramics near the morphotropic phase boundary

A series of [(1-x)Bi0.5Na0.5TiO3-xBi0.5K0.5TiO3]-0.06BaTiO(3) ([(1-x)BNT-xBKT]-0.06BT) and (1-y) (Bi0.5Na0.5TiO3-0.18Bi(0.5)K(0.5)TiO(3))-yBaTiO(3) ((1-y) (BNT-0.18BKT)-yBT) ternary ceramics which compositions around the morphotropic phase boundary (MPB) were prepared using a conventional solid-state technique. The dependence of BKT and BT content on the phase structure, dielectric, ferroelectric and energy storage density were researched. The BKT and BT were completely dispersed into the crystal lattice of BNT host, and a co-existing rhombohedral and tetragonal phase is found in y = 0.04-0.08 near the morphotropic composition. Fine grain of approximately 1.09 mu m and high relative density of approximately 98% was achieved in x = 0.18 and y = 0.06 samples, and it also showed an enhanced dielectric property of epsilon(r) similar to 3557 and tan delta similar to 0.06. In addition, the introduction of BT decreased the maximum polarization and the coercive field, which conducive to increase the energy storage density. The largest energy density of similar to 2.0 J cm(-3) was showed in [0.86BNT-0.14BKT]-0.06BT ceramics and 0.96(BNT-0.18BKT)-0.04BT ceramics under 90 kV/cm, which was attributed to slender P-E loops with a low coercive field (E-c = 26.2 kV/cm) and the highest polarization difference (Delta P = 15 mu C/cm(2)). The results indicate that lead-free BNT-BKT-BT ferroelectric ceramics near the MPB composition are broad development prospects for dielectric materials.