Studies on the Reorganization of Extended Defects with Increasing n in the Perovskite‐Based La₄Sr_n–4Ti_nO_3n+2 Series

Abstract Perovskite titanates with nominal stoichiometry ABO_3+δ often exhibit quite interesting properties, but their structural characterization is not always rigorous. Herein, we demonstrate how excess oxygen can be incorporated in a titanate perovskite‐based lattice. A new family of layered perovskites La₄Sr_n–4Ti_nO_3n+2 has been investigated by means of X‐ray diffraction, neutron diffraction, transmission electron microscopy, thermogravimetric analysis, and density and magnetic measurements. Such layered perovskites are known to be able to accommodate extra oxygen beyond the parental ABO₃ perovskite in crystallographic shears. The structure evolves with increasing n. Firstly, the perovskite blocks become more extensive and the oxygen intergrowth layers move further apart; then the spacing between the intergrowth layers increases further and their repetition becomes more sporadic. Finally, the layered structure is lost for the n = 12 member (La₂Sr₄Ti₆O_19–δ). In this structure, excess oxygen is accommodated within the perovskite framework in randomly distributed short‐range linear defects. These defects become more dilute as the cubic perovskite, that is, n = ∞, composition is approached.