A New Line Defect in NdTiO₃ Perovskite

Perovskite oxides form an eclectic class of materials owing to their structural flexibility in accommodating cations of different sizes and valences. They host well-known point and planar defects, but so far no line defect has been identified other than dislocations. Using analytical scanning transmission electron microscopy (STEM) and ab initio calculations, we have detected and characterized the atomic and electronic structures of a novel line defect in NdTiO₃ perovskite. It appears in STEM images as a perovskite cell rotated by 45°. It consists of self-organized Ti-O vacancy lines replaced by Nd columns surrounding a central Ti-O octahedral chain containing Ti⁴⁺ ions, as opposed to Ti³⁺ in the host. The distinct Ti valence in this line defect introduces the possibility of engineering exotic conducting properties in a single preferred direction and tailoring novel desirable functionalities in this Mott insulator.