Relaxor ferroelectric behavior of BaBi_4Ti_4O_(15) aurivillius ceramic

摘要

Aurivillius type compound BaBi_4Ti_4O_(15) (BBT) ceramic was prepared by solid state reaction route and its electrical properties were studied. X-ray diffraction (XRD) pattern showed orthorhombic structure with space group A21am confirming it to be an m = 4 member of the Aurivillius oxide. The scanning electron microscope of the sintered pellet showed a plate-like morphology of grains which is a characteristic feature of the Aurivillius compounds. The temperature and frequency dependence dielectric study showed a shifting of transition temperature with frequency indicating relaxor type behavior in the material. The diffuseness parameter (γ) established the relaxor nature and it was attributed to the A-site cationic disorder. The dielectric relaxation obeyed the Vogel-Fulcher (VF) relation and various parameters like activation energy for relaxation, freezing temperature, relaxation frequency were determined after nonlinear curve fitting. The temperature dependence of dielectric constant at temperatures much higher and lower than T_m was analyzed by two exponential functions, which gives an idea about the production of polar clusters at high temperature and the distribution of freezing temperatures at lower temperature. Various other associated parameters were calculated by nonlinear curve fitting and their significance has been explained.