Structural, dielectric and ferroelectric properties of Bi(Fe1-xTix)O3+x/2-PbTiO3 ceramics with MPB compositions

Dense ceramics of 0.67Bi(Fe_1-xTi_x)O_3+x/2-0.33PbTiO₃ (x=0, 0.005, 0.01, 0.02, 0.04) with MPB compositions have been synthesized by solid state reactions. Structural characterization by X-ray diffraction (XRD) reveals the simultaneous presence of a tetragonal, an orthorhombic, and a rhombohedral phases in 0.67BiFeO₃-0.33PbTiO₃. The electric conductivity decreases with the increasing Ti⁴⁺ substitution amount. As a result, the temperature dependence of dielectric constant of the Ti⁴⁺-doped ceramics were measured up to their ferroelectric Curie point (T_C) as high as 650degC, and the saturated dielectric hysteresis loop with remnant polarization of 9 muC/cm² was obtained in 0.5 mol% Ti⁴⁺-doped ceramic. A Pr of 17 muC/cm² was displayed in unsaturated P-E loop of 2 mol% Ti⁴⁺-doped sample, which indicates that a much higher saturated polarization can be expected on the Ti⁴⁺-substituted BiFeO₃-PbTiO₃ ceramics.