Ferroelectric and piezoelectric properties of lanthanoid-substituted Bi4Ti3O12 thin films grown on (111)Pt and (100)IrO2 electrodes

We investigated he effect of film orientation on piezoelectric and ferroelectric properties of (Bi(3.25)Ln(0.75))Ti3O12 (Ln=La, Nd, and Sm). c-axis-oriented films were grown on (111)Pt electrodes with nondoped Bi4Ti3O12 buffer layers. The films grown on (100)IrO2 electrodes showed predominantly (111) and (110) orientation. The piezoelectric coefficient d(33,f) and the remanent polarization P-r were larger for (111)- and (110)-oriented films than for c-axis-oriented films. This relation was independent of the type of lanthanide species used as Bi substituting ion. This strongly indicates that the direction of the spontaneous polarization vector does not turn toward the c axis due to such substitutions, as was recently proposed in the literature. (c) 2005 American Institute of Physics.