Magnetic and absorption characteristics of Mn and Ti subsituted barium hexaferrite for microwave absorber

This paper reports our recent investigation on Mn⁺² and Ti⁺⁴ ions substituted Barium Hexaferrites. Materials of nominal compositions BaFe_12-2x(MnTi)_xO₁₉ (x = 0.0; 1.5 and 2.5) were prepared through a two-stage process by mechanical alloying and successive sintering. The first stage was the preparation of (Fe, Mn, Ti)₂O₃ obtained from partial substitution of Mn⁺² and Ti⁺⁴ ions in a single phase Fe₂O₃. This was followed by the second stage in which BaCO₃ and (Fe, Mn, Ti)₂O₃ components were mechanically alloyed. A successive solid state reaction at different sintering temperatures has lead to the formation of Mn and Ti substituted barium hex ferrite. Phase identification by XRD confirmed the single phase material. Microstructure by TEM showed grains are extremely fine about 30 nm in size. The electrons diffraction rings of the area shown uniform intensity around Debye rings indicating that grains are randomly oriented. Evaluation on the magnetic characteristic for the materials indicated that coercivity decreased progressively as the number of Mn⁺² and Ti⁺⁴ ions increased although this was also followed by a less significant decrease in the total magnetization. As to the microwave absorber, reflection and transmission coefficients as well as reflection loss in the frequency range 1-6 GHz were derived. In this paper, Absorption performances of nanocrystalline Mn and Ti substituted barium hex ferrite materials are also reported.