Design and ferroelectric properties of polar-axis-oriented polycrystalline Bi4-xPrxTi3O12 thick films on Ir/Si substrates

A route for polar-axis-oriented films with Bi4Ti3O12 (BIT)-type structure was presented. Bi4-xPrxTi3O12 (x=0.0, 0.3, 0.5, 0.7) films were grown on Ir/Si substrates from chemical solutions and formation of IrO2 from Ir layers fostered the nucleation of grains with a and b axes mixed orientation by lattice matching and pseudo-orthogonal c axes was aligned in-plane. Furthermore, by setting the heat treatment temperature for grain growth above the Curie temperature T-C, the residual strain between the film and Si introduced lateral stress on cooling and aligned the ferroelectric polar axis separately along the film normal leaving the nonpolar axis in-plane. The polar-axis-oriented film exhibited superb ferroelectric properties with remanent and saturation polarizations of 2P(r)=92 and P-sat=50 muC/cm(2) (x=0.3). (C) 2003 American Institute of Physics.