Effects of pH and calcination temperatures on the formation of citrate-derived hexagonal barium ferrite particles

The BaFe12O19 particles derived from the aqueous solutions containing Ba(NO3)2, Fe(NO3)3, and C3H4(OH)(COOH)3 in a molar ratio of 1:12:19 at different pH conditions, adjusted by NH4OH, were examined using XRD, FT-IR, DSC, TG, TEM, and SQUID. At pH ≥ 8, the nanoparticles with single crystalline barium hexaferrite phase can be obtained at temperatures as low as 650 °C. By using the solution of pH 3, the pure crystalline barium hexaferrite nanoparticles with better morphological development of its crystallites and magnetic properties can be produced at temperatures at or above 700 °C. The BaFe12O19 particles derived from the solution of pH 3 and at 900 °C exhibited magnetic properties of 61.7 emu/g in magnetization (measured at 30 kOe), 30.8 emu/g in remanence magnetization, and 5.1 kOe in coercive force. The compositions and the corresponding reactions for the solid prepared from the solution of pH 3 at different temperature ranges were calculated and postulated.