Microwave sintered Bi0.90La0.10Fe0.95Mn0.05O3 nanocrystalline ceramics: Impedance and modulus spectroscopy

Multiferroic Bi0.90La0.10Fe0.95Mn0.05O3 (BLFMO) nanoceramics were synthesized by PVA sol-gel method, followed by microwave sintering. The structural, microstructural and electrical properties of BLFMO were investigated. The crystal symmetry and unit cell dimensions were determined from the experimental data using Rietveld analysis. BLFMO revealed only one electroactive region as verified from impedance and modulus spectroscopy. Overlapping large polaron tunneling transport mechanism was observed from AC conductivity analysis. Conduction below 250 °C (−30 °C≤T≤250 °C) was attributed to translational hopping while above 250 °C (250 °C≤T≤350 °C) corresponds to electron hopping between charge defects. The relative permittivity varies from 66 to 203 at 1 kHz over the measured temperature range (−150 °C≤T≤350 °C). The electrical conductivity of the microwave sintered BLFMO has been discussed based on defect reaction with Mn doping. The measured DC conductivity in the range of 10−13 S/cm at −130 °C to 10−4 S/cm at 350 °C revealed the insulating behavior of the sample. At room temperature, the DC resistivity of the sample was over ~50 MΩ cm. The stretching constant (β) obtained from KWW (Kohlrausch-Williams-Watts) equation indicates that the sample inclined towards ideal Debye behavior as the temperature increases.