Facile route to prepare grain-oriented multiferroic Bi7Fe3−xCoxTi3O21 ceramics

A facile route was developed to fabricate Bi7Fe3−xCoxTi3O21 (BFCTO) ceramics in which the micrometer sized grains were highly [0 0 1] oriented. The preparation involved dry pressing nanoplates with high aspect ratio under low axial pressure (10 MPa), and subsequently sintering the green compact at high temperature without applied pressure. The formation mechanism and the effects of Co doping on the orientation were investigated. The results indicated that the orientation degree of BFCTO grains was depended on the aspect ratio of nanoplate powder, which increased with the increase of doping amount of Co. The degree of orientation was achieved as high as 0.91 in Bi7Fe2CoTi3O21 ceramic. The saturation magnetization (2 Ms) values were larger when surfaces of the oriented grains were perpendicular to the direction of applied magnetic field, indicating obvious anisotropic magnetism. This fabrication method provided an economical yet convenient approach to manufacture grain-oriented complex oxide ceramics with improved magnetic property.