Structural and dielectric properties of ferroelectric Sr_1_-_xBa_xBi_2(Nb_0_._5Ta_0_._5)_2O_9 and Sr_0_._5Ba_0_._5Bi_2(Nb_1_-_yTa_y)_2O_9 ceramics

Abstract

Ferroelectric Sr_1_-_xBa_xBi_2(Nb_0_._5Ta_0_._5)_2O_9and Sr_0_._5Ba_0_._5Bi_2(Nb_1_−_yTa_y)_2O_9 were synthesized by solid state reaction route. X-ray diffraction studies confirm the formation of single phase layered perovskite solid solutions over a wide range of compositions (x=y=0.0, 0.25, 0.50, 0.75 and 1). The lattice parameters and the Curie temperature $(T_c)$ have been found to have linear dependence on x and y. Transmission electron microscopy (TEM) suggest the lowering of orthorhombic distortion with increasing Ba^2^+ substitution. Variations in microstructural features as a function of x and y were monitored by scanning electron microscopy (SEM). The dielectric constant at room temperature increases with increase in both x and y. Interestingly Ba^2^+ substitution on Sr^2^+ site induces diffused phase transition and diffuseness increases with increasing Ba^2^+ concentration