Effects of lanthanide dopants on the ferroelectric property of Bi4Ti3O12 thin films

Effects of lanthanide dopants on the structural and electrical properties of Bi(4-x)A(x)Ti(3)O(12) (A=La, Sm, Gd, Dy) with x=0.75 were investigated for thin films deposited by pulsed laser deposition. Changes in the lattice constant were observed depending on the ion size of dopants. As the ion size of dopant elements was decreased, the difference between a- and b-axis parameters became larger. Coercive field, measured from hysteresis loop, was increased as the ion size of doped lanthanide was decreased. Also, fatigue characteristic was improved by substituting lanthanide for Bi in Bi4Ti3O12. In addition to the chemical stability of oxygen, distortion of octahedra in the perovskite blocks in Bi(4-x)A(x)Ti(3)O(12) may be responsible for the observed changes in the ferroelectric characteristics.