Dielectric properties of amorphous BiFeO3

An amorphous material based on multiferroic BiFeO(3)was obtained, using melt quenching method. Its dielectric properties were studied within the temperature range -200 to 600 degrees C. The material is characterized by a high dielectric permittivity epsilon approximate to 10(4)(at 200 degrees C and a frequency of 100 Hz), due to the contribution of migration polarization. Using the DTA method, the glass transition temperatureT(g)approximate to 400 degrees C and crystallization temperatureT(cr)approximate to 490 degrees C were determined. It was found that the temperaturesT(g)andT(cr)correspond to anomalies of epsilon, the superposition of which forms a diffuse maximum of the dielectric permittivity. Staged annealing leads to decrease of these anomalies and their shift along the temperature axis in opposite directions. Substantially below ofT(g)two thermally activated dielectric relaxation processes were revealed. The relaxation time of one of them is obeyed to the Arrhenius law with an activation energyU approximate to 0.53 eV and preexponential factor tau(0)approximate to 4.38 10(-12)s.