Sol-gel processed ferroelectric barium titanate thin films and ceramics

Ferroelectric barium titanate BaTiO₃, thin films and ceramics were prepared by polymeric sol-gel processing technique from barium acetate, Ba(CHCOO)₂, and titanium isopropoxide, Ti[OC ₃H₇]₄, precursors. It is shown that the ceramic prepared from the sol-gel derived powder give higher packing density and piezoelectric coupling constant, d₃₃, as compared to conventional ceramics prepared by solid state reaction. By properly adjusting the viscosity of the stock solution and using spin coating technique, it has been possible to fabricate homogeneous and uniform films of BaTiO₃ on different substrates. The as grown films are amorphous, which can be crystallized into ferroelectric tetragonal phase by a post deposition annealing at 700°C. The lattice constants of the films are close to the bulk values. The polarization hysteresis, C-V and G-V measurements as well as the dielectric anomaly at about 125°C clearly establish the ferroelectricity in the films. The dielectric and ferroelectric properties of bulk ceramics and thin films are compared and discussed