Effect of La3+ content on the properties of ferroelectric Bi4-xLaxTi3O12 (BLT) thin films prepared by aqueous chemical solution deposition

Abstract

Lanthanum substituted bismuth titanate thin films were deposited using an aqueous chemical solution deposition method. Varying the composition of Bi4-xLaxTi3O12, with x = 0.5, 0.65, 0.75 and 0.85, is shown to have a large influence on the microstructure and properties of the films. Increasing the amount of La3+, x, from 0.5 to 0.85 led to a decrease of the remanent polarization (P-r) from 6.2 to eventually 0 mu C/cm(2). This decrease of P-r is explained by means of X-ray diffraction (XRD) study, which shows that there is an increased preference for c-axis orientation upon increasing the La3+ concentration. Furthermore, a strong decrease of the grain size upon increasing x is observed in a scanning electron microscopic (SEM) study. The concurrent increase of domain pinning on the grain boundaries is a second effect which may be responsible for the deterioration of the ferroelectric property at larger x.