Description:

Using high-resolution transmission electron microscopy (HRTEM), researchers obtained structure images of strontium titanate (SrTiO₃) with a clearly resolved oxygen sublattice along different crystallographic directions in the bulk lattice and for a Σ3 tilt grain boundary (GB).  In this HRTEM image of a Σ3(111)[1-10] GB of SrTiO₃ along the [1-10] direction the strontium, titanium, and oxygen are atomically resolved in both the bulk and the GB. Oxygen atoms show dark contrast on a bright background. The inset shows the intensity profile along the GB, in which the O column marked by an arrow shows reduced occupancy. Comparison with image simulations showed that the grain boundary contains oxygen vacancies. Measurements of atom displacements near the grain boundary revealed close correspondence with theoretical calculations.  It is important to understand these nano-sized features in materials, as most materials are formed of many individual grains (like these) rather than a single crystal, and the grain boundaries have a large effect on the mechanical and electrical properties of the material.

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