Influence of La, Mn and Zn Substitution on the Structure, Magnetic and Absorption Properties of M-Type Barium Ferrites

A series of M-type barium ferrites with chemicals composition BaFe12O19 and Ba0.7La0.3Fe(12-2x)(MnZn)xO19 (with x = 0.0, 0.2, 0.5) were synthesized using a chemical coprecipitation based technique. The sample was then called as BFO and BLF, BLFMZ-02 and BLFMZ-05, respectively. The structural parameters were measured by applying the full pattern fitting of Rietveld method using Fullprof program. The crystallite size was calculated using Scherrer formula and Williamson-Hall analysis method, and also confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The morphology of particle is composed of fine-grained aggregates with particle size distributions in the range of 70nm - 160nm. The lattice parameter (a = b and c), cell volume (Vcell) and density (ρ) of the samples were found to be changed with La, Mn and Zn substitution due to the dissimilar cationic radii of Ba2+ (1.49Å), La3+ (1.22Å), Fe3+ (0.64Å), Mn3+ (0.89Å) and Zn2+ (0.76Å) ions. The results of sample measurements with Vibrating Sample Magetometer (VSM) indicate that the magnetic behaviours showed that the saturation magnetization (Ms) increased gradually with the substitution of La3+, Mn3+ and Zn3+ ions, whereas the coercivity (Hc) was increase with addition of La3+ ions and then decrease significantly with the addition of Mn3+ and Zn2+ ions. The vector network analyzer (VNA) revealed that microwave absorption measured within 7 – 15 GHz frequency range indicated optimum reflection loss (RL) of-21.50dB at 10.5GHz for BLMZ-02 sample.

Effect of Sintering Temperatures on Structural, Magnetic and Microwave Properties of Barium Ferrites/Epoxy Composites

This research highlights the structural magnetic and microwave properties of nanoparticles of M-type hexagonal barium ferrites (BaFe12O19). The samples were sintered at varied sintering temperatures (800, 900, and 1000 °C). The effect of temperatures on the structural, magnetic and microwave properties was highlighted. Barium ferrites are well-known materials used for radar absorbing materials (RAM). RAM materials with good absorbing performance should have high permeability, small permittivity and high magnetic or dielectric loss at microwave frequency. High microwave absorption can be created effectively in magnetic materials, as well as wideband absorption. The structural, microstructural and microwave properties were analyzed via an X-ray Diffractometer (XRD), a Field Emission Scanning Electron Microscope (FESEM) and a Vector Network Analyzer (VNA), respectively. The XRD results showed a full phase hexagonal structure was formed in the samples sintered at 900 and 1000 ºC. BaFe12O19 composite with a thickness of 3 mm showed a minimum Reflection Loss (RL) at −9.01 dB at a frequency of 9.16 GHz at temperature 1000 ºC.