Dielectric Properties of Multiferroic Composite Consisting Lithium Ferrite and Bismuth Titanate Synthesized by Combustion Method

In this work, lithium ferrite and bismuth titanate have been synthesized to fabricate a multiferroic composite by microwave-induced combustion method. Multiferroic composites with the formula (where x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) were prepared. X-ray diffraction patterns showed that perovskite structure of bismuth titanate and spinel structure of lithium ferrite have been formed successfully in the as-synthesized nanostructured powders. Dielectric properties were examined by a LCR meter. Multiferroic composites containing the higher content of Li ferrite (70 wt % and 90 wt% Li ferrite), in comparison to the pure bismuth titanate and Li ferrite, indicate higher values of dielectric constant. In bismuth titanate and the composite with 10 wt% Li ferrite, dielectric constant remains constant as the frequency changes; in contrast, this character decreases significantly with frequency for Li ferrites and the other composites in such a way in Li ferrite, dielectric constant decreases from 8500 at 100 Hz to 180 at 1 MHz. Some dielectric peaks are observed in the dielectric constant vs. temperature plots which more or less shift to the higher temperatures as the bismuth titanate increases. For instance, the maximum dielectric constant of 2250 is observed at 25 ºC for Li ferrite; nevertheless, the maximum value of 5990 is found at 400 ºC for sample containing 70 wt% bismuth titanate.