Structural and Magnetic Properties Evolution of Co-Nd Substituted M-type Hexagonal Strontium Ferrites Synthesized by Ball-Milling-Assisted Ceramic Process

摘要

M-type hexagonal Sr1-x Co (x) Nd (x) Fe12-x O-19 (x = 0, 0.08, 0.16, and 0.24) has been synthesized by ball milling, followed by calcination in air. The calcined products have been characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra, and vibrating sample magnetometry. XRD and SEM analyses confirm the formation of M-type Sr hexaferrite with platelet-like morphology when Sr1-x Co (x) Nd (x) Fe12-x O-19 (x = 0, 0.08, 0.16, and 0.24) precursors are calcined at 950A degrees C in air for 2.5 h. Lattice parameters "a" and "c" values of Sr1-x Co (x) Nd (x) Fe12-x O-19 reflect a very small variation after doping of Nd3+ and Co2+ ions. Average crystallite size of Sr1-x Co (x) Nd (x) Fe12-x O-19 sample, calcined at 1150A degrees C, decreased obviously after doping of Co2+ and Nd3+ ions. This is because the bond energy of Nd3+-O2- is much larger than that of Sr2+-O2-. Magnetic characterization indicates that all the samples exhibit good magnetic properties. Substitution of Sr2+ and Fe3+ ions by Nd3+ and Co2+ ions can improve the specific saturation magnetizations and remanence of Sr1-x Co (x) Nd (x) Fe12-x O-19. Sr0.84Co0.16Nd0.16Fe11.84O19, calcined at 1050A degrees C, has the highest specific saturation magnetization value (74.75 +/- 0.60 emu/g), remanence (45.15 +/- 0.32 emu/g), and magnetic moment (14.34 +/- 0.11 mu (B)); SrFe12O19, calcined at 1150A degrees C, has the highest coercivity value (4037.01 +/- 42.39 Oe). These magnetic parameters make this material a promising candidate for applications such as high-density magnetic recording and microwave absorbing materials.