Low-Temperature Sintering of Barium Hexaferrites With Bi2O3/CuO Additives

Barium hexaferrites BaFe₁₂O₁₉ with Bi₂O₃/CuO additives were synthesized by the conventional oxide ceramic process. The results manifest that Bi₂O₃ additives mainly concentrate on the grain boundary regions, while CuO additives could both enter into the grain and segregate at the grain boundary regions. The appropriate sintering temperature of barium hexaferrites with Bi₂O₃ and Bi₂O₃+ CuO additives reaches 1020 °C and 920 °C, respectively. As the amount of Bi₂O₃ is 3 wt%, the specimens of BaFe₁₂O₁₉ show saturation magnetization (Ms) of 346 kA/m, remanence (Mr) of 227 kA/m, and density (d) of 5.06 g/cm³. Meanwhile, the combination of 3 wt% Bi₂O₃ and 3 wt% CuO additives significantly promotes grain growth and sintering densification, with a high saturation magnetization of 371 kA/m and density of 5.23 g/cm³ for BaFe₁₂O₁₉, which are pretty close to the theoretical values (380 kA/m, 5.28 g/cm³). Moreover, the corresponding remanence could also rise by 10% compared with that in the sintered samples with 3 wt% Bi₂O₃.