Grain Orientation and Electrical Properties of Hot-Forged Bi₄Ti₃O₁₂ Ceramics

The effect of grain orientation on the dielectric properties of hot-forged ferroelectric Bi₄Ti₃O₁₂ ceramics has been investigated and the properties are compared with ordinarily fired ones. The degree of grain orientation f calculated from X-ray diffraction patterns is found to be as large as 0.95. The temperature dependences of the dielectric constant ε_s and loss tangent tan δ are measured with a Q-meter at 12 MHz in the perpendicular [⊥] and parallel [//] directions to the forging axis, and considerable anisotropies, such as ε_s[⊥]/ε_s[//]=5 at the Curie temperature of about 680°C, are seen. The remanent polarization P_r is calculated for both cases of perfect (f=1) and random (f=0) grain orientations. Observed P_r values from hysteresis loops are smaller than calculated ones, the ratio of the former to the latter being about 82% for the hot-forged ceramics.