Influence of Ba Substitutions on Microstructure and Magnetic Properties of La–Ca–Co System Permanent Ferrite

Abstract

La0.6Ca0.4−xBaxO⋅n/2(Fe1−yCoy)2O3(x = 0, 0.05, 0.1, 0.15 and 0.2) permanent ferrite materials were prepared by ceramic technique. The topography and the structure were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. The magnetic properties were measured using vibrating sample magnetometer (VSM) and digital magnetometer. Single M-phase and flake-like grains were obtained for samples without Ba substitution(x = 0), and the magnetic properties of the pre-sintering La–Ca–Co ferrite were as follows: Br = 440 mT, Hcb = 296 kA/m, Hcj = 426 kA/m, (BH)max = 36.6 kJ/m3 and Hk/Hcj = 0.83. When Ca was substituted by Ba, pre-sintered powder presents single M-phase structure and close three-dimensional size of grains, resulting in an improved rectangle ratio of sintered magnet. The rectangle ratio of sintered magnet reaches a maximum of 0.93 when x = 0.1. By optimizing process parameters, M-type La–Ca–Ba–Co sintered magnet was prepared with Br = 445 mT, Hcb = 337 kA/m, Hcj = 420 kA/m, (BH)max = 38.6 kJ/m3 and Hk/Hcj = 0.95.