Morphotropic phase boundary and electrical properties of bisumuth sodium titanate-potassium niobate solid-solution ceramics

A morphotropic phase boundary (MPB) between (Bi1/2Na1/2)TiO3 (rhombohedral system) and KNbO3 (orthorhombic system) was determined by using X-ray diffraction and dielectric measurements. A solid solution, (1 - x)(Bi1/2Na1/2)TiO3-xKNbO(3) [BNTK-100x], shows a rhombohedral symmetry and orthorhombic symmetry at a composition of around 0 less than or equal to x less than or equal to 0.95 and 0.96 less than or equal to x less than or equal to 1.00, respectively. The dielectric constant, epsilon (s), at Curie temperature, T-c, was the largest value in the BNTKm-96 system. From these results, the MPB of the BNTK system seems to exist in BNTK-96. The BNTK ceramics were confirmed to be ferroelectric by observing their hysteresis loops. Resistivities, rho, of BNTK-100x (0.94 less than or equal to x less than or equal to 0.98) are 10(9)-10(12) Omega (.)cm. An electromechanical coupling factor, k(33), of BNTK-96 is 0.16, which is an unsaturated value.