Dielectric Relaxation in BaTiO3–Bi(Zn1/2Ti1/2)O3 Ceramics
A dramatic improvement in the dielectric and electrical properties has been observed in ceramics of 0.8BaTiO3–0.2Bi(Zn1/2Ti1/2)O3 through the introduction
of Ba vacancies. It possesses a high relative permittivity (εr > 1150) along with a low dielectric loss (tan δ < 0.05) that is maintained up to temperatures as high as 460°C. It is also characterized
by a high resistivity of 70 GΩ‐cm, which remains constant up to 270°C. Analysis of complex impedance (Z*) and complex electric modulus (M*) data, measured over the frequency range of 1–106 Hz, revealed a number of important findings.
At high temperatures (T > 255°C), a complex plane analysis of Z″ versus Z′ and the frequency dependence of Z″ suggests an electrically inhomogeneous microstructure for the stoichiometric composition. The stoichiometric composition
exhibited activation energies of ~1 eV which suggests an extrinsic conduction mechanism. However, the introduction of Ba vacancies resulted in electrically homogeneous microstructure. An overlap of the Z″ and M″ peaks
in the frequency domain and much larger activation energies were observed, on the order of half of the band gap, suggesting an intrinsic conduction mechanism. A more detailed analysis of the data reveals insights into the physical mechanisms underpinning the dielectric and ac conductivity.