Ferroelectric and piezoelectric properties of lanthanoid-substituted Bi_4Ti_3O_(12) thin films grown on (111)Pt and (100)IrO_2 electrodes

摘要

We investigated the effect of film orientation on piezoelectric and ferroelectric properties of (Bi_(3.25)Ln_(0.75))Ti3O_(12) (Ln=La, Nd, and Sm). c-axis-oriented films were grown on (111)Pt electrodes with nondoped Bi_4Ti_3O_(12) buffer layers. The films grown on ((100)IrO_2 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.