Structural and dielectric spectroscopy studies of the M-type barium strontium hexaferrite alloys (Bax Sr1-xFe12O19)

The M-type barium hexaferrite BaxSr1-xFe12O19 (where 0 < x < 1) alloys were prepared by a new ceramic procedure. The samples were studied using X-ray diffraction and Rietveld analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, infrared and Mossbauer spectroscopy. The X-ray analysis indicates that the all the samples present a hexagonal structure. The IR spectra showed three main absorption bands in range of 400-600 cm(-1) corresponding to SFO100 and BFO100. The Mossbauer spectra showed a superposition of five subspectra associated with the five sites of the iron ion, which in the ferric state. The SEM studies showed that the hexaferrites presented grains that varied in the range of 260-305 nm. The dielectric properties: dielectric constant (epsilon') and dielectric loss (tg delta) were measured at room temperature in the frequency range from 100 Hz to 40 MHz. The samples present a nonlinear behavior for the dielectric constant at 100 Hz, 1 kHz and 1 MHz. The dielectric constant is not following the linear mixing rule for the samples. The structural, dielectric and magnetic properties of the composite barium hexaferrite phases were discussed in view of applications as a material for permanent magnets, high density magnetic recording and microwave devices.