Dielectric and impedance spectroscopy study of Ba_0.8Bi_2.133Nb_1.6Ta_0.4O₉ ferroelectric ceramics, prepared by chemical route

Nanocrystalline ceramic powder of Ba_0.8Bi_2.133Nb_1.6Ta_0.4O₉ was synthesized by chemical precursor decomposition method. The single-phase formation of the compound was confirmed using an X-ray diffraction technique and was found to be a tetragonal phase at room temperature. Average crystallite size and particle size were found to be 41 and 48.5 nm, which were analyzed through XRD and TEM respectively. The dielectric constant and tangent loss were measured in the frequency range 1 kHz–1 MHz after sintering the sample at 900 °C for 4 h. The polarization behavior was studied at an applied voltage of 6.2 kV/cm. Electrical properties of the material were investigated using complex impedance spectroscopy (CIS) technique, which revealed the presence of both grain and grain-boundary effects in the materials, which is also evidenced from the scanning electron microscope image. Grain conductivity indicated Arrhenius-type thermally activated process. AC conductivity spectrum obeys Jonscher’s universal power law. The electric modulus analysis suggests the possibility of hopping mechanism for electrical processes in the system with a non-debye type relaxation, which is supported by the impedance data.