Structural and magnetic properties of M–Ti (M = Ni or Zn) co-substituted M-type barium ferrite by a novel sintering process

Abstract

M2+ (Ni2+ or Zn2+) ion together with Ti4+ ion were substituted for two trivalent Fe3+ ions of M-type barium ferrite in the form of Ba(MTi)xFe12−2xO19 (x = 0.30, 0.60, 0.90 and 1.20). Samples were prepared by solid state reaction and sintered by a novel process. The samples were sintered by the sintering process at a high temperature of 1175 °C for 6 h and slowly downed to 800 °C at a rate of 1 °C per 1 min, and then cooled in air. This process could control contract deformation of grains and effectively reduce the pore formation. Under the novel sintering process, with x = 0.30–1.20, co-substitution of M–Ti caused no change to the single phase M-type barium ferrite structure, and the samples exhibited more homogeneous microstructure. The bulk density (ρ) increased with Zn–Ti contents, and the maximum density was 4.75 g/cm3 (x = 1.20), which was 89.7 % of theory density (5.29 g/cm3). Magnetic properties such as saturation magnetization (M s ) and coercivity (H c ) decreased with increasing of M–Ti substituted contents. Magnetic permittivity increased first, and then decreased at different x content under Ni–Ti and Zn–Ti substitution.