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Micro-structures and magnetic properties of Mg-Al substituted in barium hexa-ferrite prepared by co-precipitation method

In this study, Mg-Al substituted barium hexa-ferrite of BaFe12-2xMgxAlxO19 (x=0-0.2) materials using co-precipitation method at a calcination temperature of 1200°C for 2 hours were carried out. The precursor concentrations of the mixture were varied to identify the optimum sample. The final powder was characterized by using XRD, FE-SEM, and VSM. The XRD shows that the Mg-Al substitution was not change the micro-structures of barium hexa-ferrite. FE-SEM observation was carried out on the surface of hexagonal shape of barium hexa-ferrite. The magnetic properties shows that the decreases saturation (Ms), remanence (Mr) and coercivity (Hc). The optimum condition was obtained on x=0.2 with Ms=29.28 emu/g, Mr=15.33 emu/g, Hc=1259 Oe.

Previous study on the barium hexa-ferrite doped Al and Mn (0.12, 0.24; and 0.42 wt%) sintered at 1000 and 1100 °C for 2 hours [13]. The results suggested that show decrease of the magnetic flux, saturation, and remanence values as the additive concentration increases. Shaayan et al. [14], reported that the synthesis of BaFe12-xAlxO19 at a calcination temperature of 1100 °C for 9 h using a mechanical alloying method, resulted that the decrease of the saturation magnetization in addition of Al. Kumar et al. [15] reported that the synthesis of BaMgxFe(12-x)O19 using the sol gel method with calcination temperature at 1100 o C for 2 hours. The results confirmed that, Mg has been substitution in BaFe12O19 with single phase hexagonal structure.
In this study, Mg-Al substituted barium hexa-ferrite of BaFe12-2xMgxAlxO19 (x=0-0.2) materials using co-precipitation method at a calcination temperature of 1200 o C for 2 hours were carried out.

Experimental Method
Barium hexa-ferrite with doping materials of Mg-Al (x=0-0.2) were synthesized using a co-precipitation method where barium chloride (BaCl2), iron chloride (FeCl3), magnesium chloride (MgCl2), and aluminium chloride (AlCl3) were used as the raw materials. The materials were dissolved in 25 ml of HCl (37%) and magnetically stirred for 30 minutes at room temperature. The solution was then mixed with aquadest of 50 ml in a beaker glass and was stirred using a magnetic stirrer at 500 rpm until homogeneous solution is obtained. The solution was washed 10 times using distilled water until a neutral pH of 7 is obtained and was dried in the oven for 15 hours at a temperature of 100 °C. Then, the powder was calcinated at a temperature of 1200°C for 2 hours and at a heating rate of 10 °C/minutes.
The final powder of barium hexa-ferrite material were analysed using X-ray Diffraction (Rigaku Smartlab), Field Emission Scanning Electron Microscopy (JEOL), Vibrating Sample Magnetometer (VSM250 Dexing Magnet Ltd). Figure 1 shows the XRD pattern of Mg-Al substituted barium hexa-ferrite calcinated at a temperature of 1200ºC. The samples with substituted of Mg-Al have single phase of BaFe12O19 with hexagonal crystal structure. In addition, the additive is likely occur as the ions, where Mg-Al ions replace Fe ions [16]. Figure 2 shows that the FE-SEM images of BaFe12-2xMgxAlxO19 powder samples (x=0-0.2) prepared by co-precipitation method after temperature calcination at 1200 o C for 2 hours in the air atmosphere. From Figures 2 for all FE-SEM images, it can be seen that the particle inside the sample was grown with relatively uniform shape. The particles were nearly hexagonal shape with average 5 µm.     Figure 3 represents that the hysteresis curves of BaFe12-2xMgxAlxO19 (x=0-0.2). The characteristic magnetic parameters of BaFe12-2xCoxNixO19 (x=0-0.2) are listed in Table 1. It can be seen that the substitution of the Mg-Al ions caused decrease the values of Saturation (Ms), Remanent (Mr), Coercivity (Hc). The decreases in magnetic parameters were due to the net alignment of grain magnetization. Considering the above results, Mg and Al have paramagnetic of magnetic properties, then Fe is ferromagnetic [16].

Conclusion
Mg-Al substituted barium hexa-ferrite of BaFe12-2xMgxAlxO19 (x=0-0.2) materials using co-precipitation method at a calcination temperature of 1200 o C for 2 hours were carried out. The XRD shows that the Mg-Al subtitution was not change the micro-structures of barium hexa-ferrite. FE-SEM observation was carried out on the surface of hexagonal shape of barium hexa-ferrite. The magnetic properties shows that the decreases saturation (Ms), remanence (Mr) and coercivity (Hc). The optimum condition was obtained on x=0.2 with Ms= 29.28 emu/g, Mr= 15.33 emu/g, Hc= 1259 Oe, and is suitable as an absorber of microwave material.