Evolution of the crystalline structure in (Bi0.5Na 0.5)1-xBaxTiO3 thin films around the Morphotropic Phase Boundary

Abstract

(Bi0.5Na0.5)1-xBaxTiO 3 (BNBT), which exhibits compositions for the morphotropic phase boundary (MPB) where exist an intimate coexistence of the rhombohedral and tetragonal structures, is being considered as promising lead-free alternative to the well known Pb(Zrx, Ti1-x)O3 (PZT). In this work, BNBT thin films were fabricated by chemical solution deposition (CSD) with a wide range of compositions (x∼0.050-0.150) onto Pt/TiO 2/SiO2/(100)Si substrates. Structural studies by X-ray diffraction (λCu∼1.5406 Å) using a four-circle goniometer were carried out to determine the crystalline structure of the films. Rietveld analysis of the experimental X-ray patterns showed different volume fractions of the rhombohedral and tetragonal phases as a function of the Ba 2+ content and the coexistence of both phases, characteristic of a MPB region, for x?0.055-0.080. Finally, Rutherford backscattering experiments (RBS) were performed to determine the compositional profile of the films. This study revealed a homogenous composition of the BNBT films with abrupt film/substrate interfaces.