Abstract

Present work reports the synthesis, structural and magnetic properties of BaFe₁₁O_17.5 and La₂O₃ doped  (Ba La_0.05Fe₁₁O_17.575, BaLa_0.1Fe₁₁O_17.65, BaLa_0.2Fe₁₁O_17.80 and BaLa_0.3Fe₁₁O_17.95) ferrites produced through powder metallurgy method with escalated magnetic properties. Phase evaluation, crystal structure, microstructure, and magnetic properties thermomagnetic characteristics for the La doped and La free ferrites have been investigated at varying sintered temperatures. XRD studies revealed that BaFe₁₂O₁₉ phase is formed at 900  ̊C through the reaction of Fe₂O₃ and BaFe₂O₄. Electron microscopy studies elucidated that microstructural features depend critically on the heat treatment conditions as well as La content. La addition up to 1.0 mole found to be beneficial to refine particle size close to single domain wall size, which, in turn, led to enhance magnetic properties of the ferrite. Optimum magnetic properties for the La free BaFe₁₁O_17.5 are H_c=4.4kOe, B_r=1.9kG, and (BH)_max=0.85MGOe which were improved to H_c=4.9kOe, B_r=2.4kG and (BH)_max=1.2MGOe with La₂O₃ additive. The La₂O₃ acts as a grain growth inhibitor and led to enhance high coercivity of 4.9kOe in the ferrite. The dielectric constant and dielectric loss factor decrease monotonically with increasing applied frequency at the constant temperature. Permeability is found to be sensitive to density and microstructural components like grain size and porosity of the sintered ferrites.

Keywords: Isotropic sintered ferrites; Powder metallurgy; Dielectric properties; Magnetic properties; Microstructure