Structure and Magnetic Properties of Yttrium-Doped M-Type Strontium Ferrite

Abstract

In this paper we have prepared yttrium-doped M-type strontium ferrite SrY_xFe_(12-x)O₁₉ (x = 0, 0.25, 0.5, 0.75, 1) calcined materials by solid-phase sintering method at 1150 °C for 3 h. Then the calcined materials were pressed for magnets under the condition of oriented magnetic field and sintered in 1295 °C for 3 h. We have used X-ray diffraction, scanning electron microscope and magnetic tester analyze the phase structure of the sintered magnets, the surface morphology of the sintered magnet and the magnetic properties of the sintered magnets, respectively. The results showed that with the increase of yttrium-doped, the lattice constant ‘a’ increases first of all and then decreases ‘c’ increases slowly, a/c first increases and then decreases, crystal X-ray density d_x-ray approximation increases linearly. SEM showed that the magnet has prepared a typical hexagonal structure morphology. Magnetic studies showed that with the doping of yttrium increase, the remanence B_r increasing monotonically, intrinsic coercivity H_cj and maximum energy product (BH)_max and coercivity magnetic induction H_cb are first increases and then decreases. When the x = 1, have the maximum remanence B_r with 420.7 mT, but the intrinsic coercivity H_cj decreases to a minimum value; when x = 0.75 the intrinsic coercivity H_cj have a maximum value of 323.7 KA·m^-1 and the remanence B_r reach 410.4 mT.