Structural study of Bi4Ti3O12 using neutron powder diffraction data

摘要

Recently, a thin Him of Bi_4Ti_3O_(12) (BTO) has been widely studied as one of candidate materials for applications of ferroelectric random access memory due to its large remnant polarization at room temperature. The crystal structure of BTO consists of pervoskite type units, Bi_2Ti_3O_(10) (A_(n-1)B_nO_(3n+1) for n = 3), and interleaved BiiOi layers along the r-axis. In the Bi_2O_2 units, Ti ions are surrounded by oxygen octahedrons, and Bi ions occupy the outside of TiO(l octahedrons |1, 2|. Although the crystal structural information of BTO is essential to understand the remnant polarization at room temperature, the structural study of BTO has not been performed sufliciently because the difference between two kinds of crystal systems, monoclinic and orthorhombic, is subtle.