Textured development of feeble magnetic ceramics by colloidal processing under high magnetic field

The controlled development of texture is one of the ways for effectively improving physical and mechanical properties. In this review paper, we introduce a new processing of textured ceramics with a feeble magnetic susceptibility by slip casting in a high magnetic field and subsequent heating. As an example of feeble magnetic ceramics, we demonstrate the fabrication of textured alumina in details. The susceptibility of diamagnetic a-alumina is very small, but the orientation energy of the alumina particle by a high magnetic field becomes greater than the thermal energy. α-Alumina with a rhombohedral structure shows anisotropic susceptibility, but this anisotropy has up to now been more or less ignored due to its very low value. However, in a high magnetic field, the energy of crystal anisotropy becomes comparable to or greater than the energy of thermal motion. The degree of orientation depends on the processing factors, such as heating temperature, particle size, applied magnetic field, concentration of the suspension, etc. This process technique confers several advantages and it is possible for this type of processing to be applied to other non-cubic ceramics, such as TiO₂, ZnO, SnO, hydrooxy apatite (HAP), AIN, SiC, Si₃N₄, etc.