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

Ceramics of 0.67Bi (Fe1-x Tix) O3+x2 -0.33PbTi O3 (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 9 μC cm2 is displayed in the 0.5 mol % Ti4+ -substituted sample at room temperature. Pr reaches 17 μC cm2 in the sample with 2 mol % Ti4+ even though the hysteresis loop is not saturated, suggesting that a much higher saturated polarization can be expected in the Ti4+ -substituted BiFe O3 -PbTi O3 ceramics.