Iranian Journal of Materials Science and Engineering

    The structural and dielectric properties of iron and bismuth co-substituted BaTiO₃ ceramic with the formula: B_0.95Bi_0.05Ti_1-xFe_xO₃ for x=0.00 to 1.00, synthesis with solid state route, were characterized.     The X-ray diffraction results show a tetragonal phase for x=0.00. While for x=0.40 to 0.80 we observed a coexistence of tree phase tetragonal, hexagonal and pseudo-cubic. And at x=1.00 only the pseudo-cubic phase is present and the other phase disappeared. The Raman results indicate the existence of tetragonal band for x≤0.40, and an appearance of characteristic bands of Fe³⁺ ions for more than 0.40 of Fe content. The SEM micrographs show an increase in grain size with the increase of Fe content and it reaches a maximum at x=0.40.  And the Mossbauer spectroscopy indicates that our samples is paramagnetic at room temperature and that the Fe is   oxidized under Fe³⁺ with no existence of Fe²⁺ and Fe⁴⁺ ions. The temperature dependence of dielectric permittivity was investigated in the frequency range from 20 Hz to 2MHz. The results show three dielectric relaxation phase transitions from a rhombohedral ferroelectric to orthorhombic ferroelectric (T_R-O) then to a tetragonal ferroelectric phase (at T_O-T), and finally to cubic paraelectric at the Curie temperature (T_C).  In addition, the temperature of phase transition shifted to the lower temperature with the increase of Fe content for all the phase transitions. And the maximum of dielectric permittivity increases for T_R-O while for T_T-O and T_m phases transitions, it reaches a maximum at x=0.60 and x=0.80 respectively and then decreases.