Structural, thermal and magnetic properties of barium-ferrite powders substituted with Mn, Cu or Co and X (X = Sr and Ni) prepared by the sol-gel method

In this study, Ferrite A (undoped barium hexaferrite), Ferrite B (MnCuNi-doped barium hexaferrite), Ferrite C (MnCuSr-doped barium hexaferrite), Ferrite D (MnCoNi-doped barium hexaferrite) and Ferrite E (MnCoSr-doped barium hexaferrite) powders were prepared by sol-gel processing. The produced powders were calcined at 550 °C for 6 h and sintered at 1000 °C for 5 h to obtain the required phases. The powders were characterized by differential thermal analysis/thermogravimetric analysis (DTA/TG), X-ray diffractometry (XRD) and scanning electron microscopy (SEM), and vibrating-sample magnetometry (VSM). The XRD patterns indicated that the pure barium ferrite phase was not obtained. The presence of M-type BaFe _11.6Mn _0.4O ₁₉ was confirmed in the Ferrite B and Ferrite D patterns. In the Ferrite C pattern, there were the phases of BaFe ₁₂O ₁₉, Ba ₂Cu ₂Fe ₁₂O ₂₂ (X or Z-type) and Sr ₃Fe ₂O _6.16. The Ba _0.5Sr _0.5Fe ₁₂ phase was easily observed in the Ferrite E pattern. The results showed that the dopant materials significantly change the particle shape of Ferrite A powders, but also lower the value of the coercivity. A higher saturation magnetization was observed for the Ferrite D powder.