Particle oriented bismuth titanate ceramics with high density was successfully developed by a novel process ing involving a high magnetic eld. The b axes of ne powder particles were oriented perpendicular to the applied magnetic eld in the green compact. High density was achieved by subsequent sintering. The micro structure showed highly anisotropic structure.

The effect of powder properties on the degree of crystal orientation of Bi4Ti3O12 (BIT) ceramics fabricated by a high-magnetic-field method was investigated. As expected, the degree of orientation of BIT ceramics exhibited little dependence on the crystallinity of the powder, and depended on the particle size of the powder. The degree of orientation increased up to 0.96 when the particle size increased from 0.5 to 1.2 µm. The particle size dependence of the degree of orientation was similar to the relationship between the order parameter and particle size, as derived from Langevin's theory on magnetic alignment. This suggests that the crystal orientation of ceramics fabricated by the high-magnetic-field method can be controlled by selecting the particle size of the powder used.

We succeeded in fabricating c-axis (00l) oriented ZnO ceramics by using a rotating magnetic field and a subsequent sintering treatment. The degree of orientation in the green compact was about 0.5 along (00l) on the Lotgering scale. The degree of orientation increased to 0.99 after sintering at 1573 K. Particles can also be oriented in a static magnetic field, but along the direction of the a-axis or a,b-axes (h00), (hk0). These results show that selected axes can be oriented by controlling the magnetic field. Control of the crystal form in microstructures is expected to result in improvements in and better miniaturization of functional ceramics.

Highly oriented Al-doped ZnO ceramics were prepared by a high magnetic field method and their anisotropic thermoelectric properties were examined. The c-axis oriented specimen along the ab-plane showed a higher electrical conductivity compared to the a-axis and non-oriented specimens as a result of high electron mobility. On the other hand, the differences in the Seebeck coefficients and thermal conductivities between oriented and non-oriented specimens were a small. Consequently, the dimensionless figure of merit of the c-axis oriented specimen increased by about 30% compared to the other specimens.