Structural and magnetic properties of Ca-substituted barium W-type hexagonal hexaferrites

• Various Ba1−xCaxCo2Fe16O27 (x=0, 0.1, 0.3, 0.4 and 0.5) ferrites are W-type phase with a space group of p63/mmc and no any extra peak were observed in the powder XRD patterns.The lattice constants a and c decrease as Ca contents increases.
• Three weight loss steps corresponding to one sharp exothermic peak have been observed in the TG curve.
• The shape and diameters of most the grains remains almost independent of Ca2+ substitution by scanning electron microscopy.
• The saturation magnetization and the intrinsic coercive force increases with the increase of the Ca substitution amount.
• The real part of complex permittivity (ε′) and imaginary part (ε″) increase with more addition of Ca2+ amount. The imaginary part of complex permittivity (μ′) increases and the real part (μ′′) goes down after Ca2+ is doped. Furthermore, the Ca2+ ions doped in the ferrite improved microwave absorbency.

A series of W-type hexagonal ferrites with the composition Ba1−xCaxCo2Fe16O27 (x=0, 0.1, 0.3, 0.4 and 0.5) were synthesized using a sol–gel method. The effects of doping on structural and magnetic properties are studied by X-ray diffraction, thermal analyzer, scanning electron microscopy, vibrating sample magnetometer and vector network analyzer, respectively. The X-ray diffraction analysis shows that the samples belong to the W-type hexagonal ferrite. The lattice constants a and c decreases as Ca contents increases. The grains exhibit well defined hexagonal shape. The saturation magnetization and the intrinsic coercive force increases with the increase of the Ca substitution amount. The real part of complex permittivity (ε′) and imaginary part (ε″) increase with more addition of Ca2+ amount. The imaginary part of complex permittivity (μ′) increases and the real part (μ′′) goes down after Ca2+ is doped. Furthermore, the Ca2+ ions doped in the ferrite improved microwave absorbency.