It was demonstrated here how excess O could be incorporated into a titanate perovskite-based lattice. A new family of layered perovskites, La4Srn-4TinO3n+2, was investigated by using X-ray diffraction, neutron diffraction, transmission electron microscopy, thermogravimetric analysis and density and magnetic measurements. Such layered perovskites were known to be able to accommodate extra O, beyond the parental ABO3 perovskite, via crystallographic shears. The structure evolved with increasing n. Firstly, the perovskite blocks became more extensive and O intergrowth layers moved further apart. The spacing between the intergrowth layers then increased further and their repetition became more sporadic. Finally, the layered structure was lost in La2Sr4Ti6O19-δ. In this structure, excess O was accommodated within the perovskite framework as randomly distributed short-range linear defects. These defects became more dilute as the cubic perovskite (n = ∞) composition was approached.

Studies on the Reorganization of Extended Defects with Increasing n in the Perovskite-Based La4Srn-4TinO3n+2 Series. J.Canales-Vázquez, M.J.Smith, J.T.S.Irvine, W.Zhou: Advanced Functional Materials, 2005, 15[6], 1000-8