Yttrium ferrites with enhanced dielectric properties

Yttrium ferrites composed by Y3Fe5O12 (YIG) and YFeO3 exhibit interesting dielectric properties, being a potential candidate for electronic applications. In this work, yttrium ferrites were prepared by the sol-gel method. The powders were pressed into pellets and treated at temperatures between 1000 and 1500 degrees C, using differential scanning calorimetry and thermogravimetry analysis measurements to decide that temperature range. X-ray and Raman spectroscopy were used to characterize the structure and scanning electron microscopy to observe the morphology. For all treatment temperatures, Y3Fe5O12 and YFeO3 crystal phases were present. YIG crystal phase grows with treatment temperature, reaching a maximum at the sample treated at 1400 degrees C, where YFeO3 crystal phase is minimum. The dielectric properties were measured using an impedance analyser, in the frequency range 100 Hz-1 MHz, and temperature between 200 and 400 K. The dielectric constant was improved with the growth of the Y3Fe5O12 phase in addition to the increasing of the grain size. The highest value of dielectric constant, maintaining low losses, was obtained for the sample treated at 1400 degrees C(epsilon' = 1750; epsilon '' = 314; tan delta = 0.18; f = 1 kHz). For all samples, it was identified one dielectric non-Debye relaxation process and the dependence of the relaxation time with temperature obeys an Arrhenius behaviour.