Electric Field Assisted Hot Forging of Bismuth Titanate

摘要

An electric field applied across a specimen during the forging process is expected to affect the kinetics of grain growth and orientation. In addition, just as a field can align molecules in a nematic liquid with the axis of greatest polarizability in the direction of the applied field, it is possible that the polar axis in a crystallite may also be aligned during the high temperature densification process. This may improve the electric or piezoelectric properties of certain low symmetry ferroelectric materials. The idea is to combine crystallographic alignment, densification and poling all into one step, and approach single crystal-like properties in a polycrystalline ceramic. Electric fields (both DC and AC) were applied transverse to the forging direction of the low symmetry ferroelectric Bi_4Ti_3O_(12). The AC field was found to have little influence on crystallographic orientation. The DC field was found to have a profound effect; aligning the polar axis during forging, and yielding further anisotropy in the ferroelectric hysteresis.