Ion Doping Effects on the Lattice Distortion and Interlayer Mismatch of Aurivillius-Type Bismuth Titanate Compounds

Taking Bismuth Titanate (Bi(4)Ti(3)O(12)) as a Aurivillius-type compound with m = 3 for example, the ion (W(6+)/Cr(3+)) doping effect on the lattice distortion and interlayer mismatch of Bi(4)Ti(3)O(12) structure were investigated by stress analysis, based on an elastic model. Since oxygen-octahedron rotates in the ab-plane, and inclines away from the c-axis, a lattice model for describing the status change of oxygen-octahedron was built according to the substituting mechanism of W(6+)/Cr(3+) for Ti(4+), which was used to investigate the variation of orthorhombic distortion degree (a/b) of Bi(4)Ti(3)O(12) with the doping content. The analysis shows that the incorporation of W(6+)/Cr(3+) into Bi(4)Ti(3)O(12) tends to relieve the distortion of pseudo-perovskite layer, which also helps it to become more stiff. Since the bismuth-oxide layer expands while the pseudo-perovskite layer tightens, an analytic model for the plane stress distribution in the crystal lattice of Bi(4)Ti(3)O(12) was developed from the constitutive relationship of alternating layer structure. The calculations reveal that the structural mismatch of Bi(4)Ti(3)O(12) is constrained in the ab-plane of a unit cell, since both the interlayer mismatch degree and the total strain energy vary with the doping content in a similar trend to the lattice parameters of ab-plane.