Effect of iron and tungsten substitution on the dielectric response and phase transformations of BaTiO3 pervoskite ceramic

The dielectric properties of iron and tungsten co-substituted BaTiO3 perovskite ceramic with a compositional formula: BaTi0.5(Fe0.33W0.17)O3, prepared by the traditional solid-state route, were systematically characterized. The temperature dependence of the dielectric properties was investigated in the frequency range 1 kHz to 1 MHz. Three dielectric relaxations were observed in the present ceramic which originated from phase transitions from a cubic paraelectric to a tetragonal ferroelectric at the Curie temperature (TC), then to an orthorhombic ferroelectric (at TT-O), and finally to a rhombohedral ferroelectric (at TO-R) similar to those of pure BaTiO3. The dielectric relaxation behavior was analyzed with various models. The best way to characterize the degree of the dielectric relaxation for relaxor ferroelectrics was established using the experimental data. It was shown that the temperature dependence of the static dielectric constant can be well described by an exponential function, while the temperature dependence of the relaxation time was described by a power function.