Improved dielectric and ferroelectric properties of high Curie temperature (1−x)BiFeO3–xPbTiO3 ceramics by aliovalent ionic substitution

Ceramics of 0.67Bi(Fe1−xTix)O3+x∕2–0.33PbTiO3 (x=0, 0.005, 0.01, 0.02, 0.04) were prepared by solid state reactions, with a relative density of 94%–97%. The dielectric and ferroelectric properties of the ceramics have been significantly improved by means of aliovalent ionic substitution of Ti4+ for Fe3+, which reduces the electric conductivity. The temperature variation of the dielectric constant has been measured up to the Curie temperature as high as TC=650°C. A saturated dielectric hysteresis loop with a remnant polarization (Pr) of 9μC∕cm2 is displayed in the 0.5mol% Ti4+-substituted sample at room temperature. Pr reaches 17μC∕cm2 in the sample with 2mol% Ti4+ even though the hysteresis loop is not saturated, suggesting that a much higher saturated polarization can be expected in the Ti4+-substituted BiFeO3–PbTiO3 ceramics.