Preparation by sol-gel method and characterizations of (Bi4-xLax)Ti3O12 thin films

Abstract

(Bi4-xLax)Ti3O12 (abbreviated as BLT) thin films were prepared by Sol-Gel processing method with the initial materials of bismuth nitrate (Bi(NO3)3·5H2O), lanthanum nitrate (La(NO3)3·6H2O), and tetrabutyl titanate ((C4H9O)4Ti). The X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies were performed for determining the change of the crystal lattice constant, the surface morphology, the chemical composition of the films, and the chemical bonding energy of the ions in the films. It was found that BLT thin films have high c-axis orientation with monoclinic structure, and the crystal lattice constants of the films are different from those reported in the literature. The a and b values of the lattice remain constant, but the c value reduces with an increasing lanthanum content x. The chemical composition of the films, and chemical bonding energy of bismuth and lanthanum ions in the near surface region are different from those in the inside region of the films. The films are bismuth enriched in the surface region, and the composition in the "bulk" region is agreement with the stoichiometry.