Structure and electrical properties of (Na_0.5Bi_0.5)_1−x Ba _x TiO₃ ceramics made by a citrate method

(Na_0.5Bi_0.5)_1−x Ba _x TiO₃ (x = 0–0.12) powders were synthesized by a citrate method, and the structure and electrical properties of the resulting ceramics were investigated. A gradual change of crystal structure with the increase of BaTiO₃ concentration was detected together with a significant evolution in grain size and shape. A rhombohedral-tetragonal morphotropic phase boundary (MPB) near x = 0.06 at room temperature was ascertained for the ceramics. The dielectric constant (ɛ _r) and dissipation factor (tanδ) attain maximum values at x = 0.08 and x = 0.06, respectively. The specimen of x = 0.06 provides the maximum piezoelectric constant (d ₃₃ = 180 pC/N) and electromechanical coupling factor (k _p = 0.28), accompanied by a large remanent polarization of P _r = 37.1 μC/cm² and a low coercive field of E _c  = 42.7 kV/cm.