Effects of chemical modification on the electrical properties of 0.67BiFeO3-0.33PbTiO3 ferroelectric ceramics

Ceramics of the BiFeO3-PbTiO3 solid solution are expected to exhibit interesting ferroelectric and magnetoelectric properties. Chemical modifications were carried out to improve the dielectric performance of the materials. Ceramics of 0.67BiFeO3-0.33PbTiO3, 0.67BiFe0.98Ti0.02O3-0.33PbTiO3 (via B site Ti4+ modification) and 0.67BiFeO3-0.33PbTiO3 sintered under O2 flow were synthesised. The frequency-dependence of the impedance was measured at various temperatures and analysed. The dielectric properties were improved by B site Ti4+ modification and by sintering in O2 flow. The temperature dependences of dc conductivity of the grains for the three ceramic samples were derived from impedance analysis by fitting their impedance data to an electric equivalent circuit of three RC components. The temperature dependences of both the dc conductivity of the grains and the measured ac conductivity (at high and low frequencies) show that the conductivity for O2-sintered sample is the lowest, and the conductivity of 0.67BiFe0.98Ti0.02O3-0.33PbTiO3 is lower than that of 0.67BiFeO3-0.33PbTiO3. This result is consistent with the dielectric properties of the respective ceramics. The mechanism of the electric conduction is discussed in relation to the chemical modifications and related defect chemistry. 12 refs.