The impact of calcination times and Pb substitution on the physical properties of Ba_0.5Sr_0.5 Fe₁₂O₁₉ nanoparticles

Abstract

Abstract The physical properties of hexaferrite depend strongly on the methods and conditions of preparation and the chemical substitutions. The permanent magnet is considered as one of the important applications of hexaferrite. This work investigates the effect of the chemical substitution of Sr by Pb in (Ba, Sr) hexaferrite by preparing Ba 0.5 Sr 0.5-x Pb x Fe 12 O 19 with x = 0, 0.1, 0.2, 0.3, and 0.5. These samples were prepared using co-precipitation and calcined for 2 and 4 h. The x-ray powder diffraction (XRD) analysis indicates that the crystalline size and lattice parameters are increased as Pb-content and the calcination times increase. The crystalline size increase is consistent with the grain size increase, determined by scanning and transmission electron microscopies. The lattice parameters a and c for the investigated samples, estimated from XRD and selected area electron diffraction, have the same trend. Energy dispersive x-ray (EDX) results confirm the successful substitution of Sr by Pb. Fourier transform infrared (FTIR) and Raman spectroscopy confirm the formation of hexaferrite. X-ray photoemission spectroscopy (XPS) analysis verified the oxidation states of constituent elements. The vibrating sample magnetometer (VSM) was used to probe the magnetic nature of the hexaferrite samples. As the Pb amount increases, the saturation magnetization ( M s ) and remanent magnetization ( M r ) vary between 45.09 to 62.27, and 19.21 to 30.58 emu g −1 , respectively. The coercivity ( H c ) values for the samples prepared at 4 h are higher than those at 2 h. The samples calcined for 4 h have higher maximum energy product ( BH max ) values, specifically the pure sample with 5804.12 J m −3 .