Local Atomic Structures for Tunable Ordered Arrangements of Crystallographic Shear Planes in Titanium-Chromium Oxide Natural Superlattices

The atomic structure of titanium-chromium oxide natural superlattices with different compositions having an ordered arrangement of crystallographic shear (CS) planes was investigated by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) and electron diffraction, using polycrystalline ceramics prepared by arc-melting and heat treatment. Analysis of the electron diffraction patterns revealed that not only the interspacing but also the direction of planar faults changed depending on the chromium concentration. HAADF-STEM observations showed that the atomic arrangements of CS planes deviating from (121)(rutile) are random arrangements of (121)(rutile) CS planes and (011)(rutile) antiphase boundaries. Using a random walk model and by calculating the specularity parameter, we found that the CS planes in titanium-chromium oxides behave as coherent interfaces for phonons based on the estimation of interface roughness.

Automated summary

The atomic structure of titanium-chromium oxide natural superlattices with ordered crystallographic shear planes was investigated using STEM and electron diffraction. It was found that the atomic arrangements of CS planes changed depending on the chromium concentration. The CS planes in titanium-chromium oxides behaved as coherent interfaces for phonons.