Sequential variation of super periodic structures emerged in Bi-layered perovskite pillar-matrix epitaxial nanocomposite films with spinel ferrites

The phase stability of Aurivillius bismuth-layer structured Bi5Ti3FeO15 (BTFO15) has been investigated in an epitaxial pillar-matrix nanocomposite system with spinel ferrites. Depending on the growth temperature a variety of super periodic structures of BTFOs appeared, denoted by the general formula BTFO15 center dot nBiFeO(3) with almost continuous values of n between -0.5 and +1. In nanocomposites with CFO, n takes the positive values from n = 0, increasing up to n = 1 corresponding to Bi6Ti3Fe2O18 (BTFO18), as the growth temperature decreases. In contrast, in nanocomposites with NFO, n takes the negative values from n = 0, decreasing close to -0.5 corresponding to a well-known intergrowth structure of Bi4Ti3O12 (BIT)-BTFO15, as the growth temperature increases. The formation mechanism of such super periodic structures is discussed in terms of the ordering of Bi2O22+ layers in the perovskite blocks, driven by the Fe3+ transfer between BTFO15 and spinel ferrites as starting materials during phase separation, depending on the degree of excess or deficiency of the Bi amount.

Automated summary

The phase stability of Aurivillius bismuth-layer structured Bi5Ti3FeO15 (BTFO15) was investigated in an epitaxial pillar-matrix nanocomposite system with spinel ferrites. Different super periodic structures of BTFOs appeared depending on the growth temperature, denoted by BTFO15 center dot nBiFeO(3) with continuous values of n between -0.5 and +1. The formation mechanism of such structures was discussed in terms of the ordering of Bi2O22+ layers in perovskite blocks, driven by Fe3+ transfer between BTFO15 and spinel ferrites during phase separation.