Improved dielectric and ferroelectric properties of high Curie temperature (1-x)BiFeO_3-xPbTiO_3 ceramics by aliovalent ionic substitution

摘要

Ceramics of 0.67Bi(Fe_(1-x)Ti_x)O_(3+x/2)-0.33PbTiO_3 (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 Ti~(4+) for Fe~(3+), which reduces the electric conductivity. The temperature variation of the dielectric constant has been measured up to the Curie temperature as high as T_C=650℃. A saturated dielectric hysteresis loop with a remnant polarization (P_r) of 9 μC/cm~2 is displayed in the 0.5 mol% Ti~(4+)-substituted sample at room temperature. P_r reaches 17 μC/cm~2 in the sample with 2 mol% Ti~(4+) even though the hysteresis loop is not saturated, suggesting that a much higher saturated polarization can be expected in the Ti~(4+)-substituted BiFeO_3-PbTiO_3 ceramics.