Polaronic relaxation in La0.8Bi0.2Fe0.7Mn0.3O3

In this work, the dielectric properties of La0.8Bi0.2Fe0.7Mn0.3O3 ceramics have been investigated in a temperature range of 76–320 K and a frequency range of 300 Hz–10 MHz. Two thermally activated dielectric relaxations were observed with the activation energy around 0.283 ± 0.007 eV for the low-temperature relaxation and 0.268 ± 0.007 eV for the high-temperature relaxation. Annealing in N2 and O2 can destroy and create the high-temperature relaxation, respectively. But the treatments have no significant influence on the low-temperature relaxation. The low-temperature relaxation was found to be bulk effect related to the dipolar effect due to the hopping polarons, and the high-temperature relaxation was associated with the Maxwell–Wagner relaxation due to surface-layer effect caused by hopping polarons blocked and trapped at the surfaces of the sample.

► Dielectric properties of La0.8Bi0.2Fe0.7Mn0.3O3 ceramics have been investigated.
► Two thermally activated dielectric relaxations were observed.
► The low-temperature relaxation was found to be bulk effect.
► The high-temperature relaxation was associated with the Maxwell–Wagner relaxation.
► These relaxations were confirmed to be closely linked with the localized polarons.