Polymorphs and dielectric properties of BaTi1−xNixO3

We have studied the influences of the Ni doping on structural characterization and dielectric properties of BaTi1−xNixO3 (x = 0.0-0.1) prepared by conventional solid-state reaction. The composition is characterized by X-ray diffraction technique (XRD). Interestingly, there is the tetragonal-to hexagonal transformation in the crystal structure of BaTi1−xNixO3 at x = 0.06. Moreover, both hexagonal and tetragonal polymorphs coexist in the range 0.06 ⩽ x ⩽ 0.1. Complex dielectric constant (ε), ac conductivity (σac′), the normalized imaginary part of impedance Z″/Zmax″ and electric modulus M″/Mmax″ have been studied as a function of frequency and composition at room temperature and in the frequency range up to 13 KHz. The real part (ε′) of dielectric constant shows a step like relaxation behavior and has been explained qualitatively with the frame work of Kramers-Kronig transformation model. The universal dielectric response and the Jump relaxation model were considered and fitted for ac conductivity. The mismatch between the frequency dependence plots of Z″/Zmax″ and M″/Mmax″ peaks is observed. The short range hopping model seems to be most appropriate model for the conduction mechanisms in BaTi1−xNixO3.