Effect of low sintering temperature on the structural and magnetic properties of M-type strontium hexaferrite

A pure M-type strontium hexaferrite with nominal composition SrFe 12 O 19 was prepared via modified conventional citrate precursor method. The basic idea of investigation was to improve the quality of hexagonal ferrite without high temperature sintering as these ferrites are generally known for high temperature sintering techniques. Thermogravimetric analysis (TGA/DTA) of powdered sample was carried out to identify the desired crystallization point suitable for the formation of M-phase. After dividing the sample into two equal parts, the prepared sample was sintered at two different temperatures, 800˚C and 910˚C. The properties of the material were investigated via using important characterization techniques, XRD, FESEM, FTIR, Raman spectroscopy (RS) and VSM respectively. The XRD confirmed the formation of M-phase along with some impurities of Fe 2 O 3 and these results were strongly supported via both FTIR and RS. On increasing the sintering temperature, the average crystallite size was found to increase from 25nm to 33nm. The FESEM analysis confirmed the formation of densely packed grains some hexagonal platelets along with agglomerates. The magnetic parameters saturation magnetization (M s ), magnetic coericivity (H c ) and squarenes ratio (SQR) were investigated by using VSM. The value of M s for ferrite sample sintered at 910˚C was found to be 92emu/g but at the same time the H c value was found in the range of few hundreds of Oestered. This kind of behavior was due to the smaller grain size and the presence of impurity phase which was totally against the nature strontium hexaferrite. Such properties of M-type hexagonal ferrite was found very rare and procured to be an excellent candidate for switching devices, recording media, high frequency applications and many more.