Synthesis of low coercive BaFe₁₂O₁₉ hexaferrite for microwave applications in low-temperature cofired ceramic

Abstract

Polycrystalline M-type barium hexaferrite (BaFe₁₂O₁₉) samples have been synthesized by solution combustion route at different pH and calcination conditions in order to reduce the coercivity for microwave applications in low-temperature cofired ceramic (LTCC) substrates. Structural, morphological, and magnetic properties of BaFe₁₂O₁₉ were studied by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. The formation of a single-phase hexagonal structure was confirmed by XRD. The Raman spectra reveal all characteristic peaks of BaFe₁₂O₁₉, illustrating the phase purity and crystal lattice symmetry of the synthesized material. Mössbauer spectra illustrate the existence of Fe³⁺ cations at all five crystallographic lattice sites. The microstructural features observed by FESEM disclose the growth of nanoregime particles into hexagonal platelet particles after calcination at temperatures from 800°C to 1200°C. The VSM results show a lower coercivity (1350 Oe to 3500 Oe) together with reasonably high saturation magnetization (55 emu/g to 60 emu/g) and a high bulk resistivity (>10⁹ Ω-cm) at room temperature. The dependence of magnetic and electrical properties on the preparation and processing conditions is also discussed.