Design of novel ceramics with crystalline-oriented layers produced by electrophoretic deposition under a high magnetic field

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Anisotropic designs of ceramics have attracted attention, because of their improved electrical, mechanical and other properties. Texture structured ceramics have been produced by hot forming, Templated Grain Growth (TGG) and so on. However, shape and orientation direction are limited, when using these techniques. On the other hand, we have reported that development of texture can be controlled by slip casting in a strong magnetic field followed by heating even for diamagnetic ceramics such as alumina, titania, zinc oxide and so on. Electrophoretic deposition (EPD) is also applied to shaping textured ceramics from stable colloidal suspension which is placed in a strong magnetic field. We demonstrate in this study that laminar ceramics with different crystalline-oriented layer are produced by EPD in a strong magnetic field. The alumina powder was dispersed in a suspension by using an ultrasonic homogenizer and a magnetic stirrer. The suspension was placed in a superconducting magnet, and then a strong magnetic field of 10T was applied to the suspension to rotate each particle by a magnetic torque attributed to the anisotropic susceptibility. The direction of the electric field relative to the magnetic field was altered to control the dominant crystal faces. The sintering was conducted at 1873K for 2h in air without a magnetic field. We confirmed in our previous reports that c-axis of alumina with the hexagonal unit cell was parallel to the direction of magnetic field. The composite with different crystalline-oriented layer was fabricated by alternately changing the angle between the directions of the magnetic and electric fields layer by layer during EPD in 10T. Bending strength of laminar composite depended on the direction of multilayered microstructure. Crack was propagated by bending in a zig-zag path. The crack path was along the direction of orientation in each layer.