Improvement of Crystallinity in Sol-Gel Derived (Bi,La)₄Ti₃O₁₂ Films by Optimizing Dry-Gel Structures

We realized excellent ferroelectric properties with sol-gel derived (Bi,La)₄Ti₃O₁₂ (BLT) films by modifying dry gel structures just before the crystallization annealing. The dry gel structures were controlled by the oxygen pressure during baking process at 350°C. By this simple process, dried gel became very porous and thus crystallization mechanism was greatly enhanced. The maximum remanent polarization (Pr) of 27 C/cm² was achieved with an 80 nm BLT film. Although the Pr is greatly enhanced, the coercive field (Ec) was kept less than 55 kV/cm (Vc∼0.4 V). And, this film also shows the excellent fatigue property up to 10¹⁰ stress cycles.