Titanium enrichment and strontium depletion near edge dislocation in strontium titanate [001]/(110) low-angle tilt grain boundary

Abstract

Dislocations are linear lattice defects in a crystalline solid. Since the unusual atomistic environment of the dislocation may greatly influence various material properties, control of the composition would offer more opportunities to obtain unique one-dimensional structures. In the present study, we have characterized the structure of dislocations in a low-angle tilt grain boundary of strontium titanate (SrTiO 3 ). High-spatial resolution elemental mapping by electron energy loss spectroscopy combined with scanning transmission electron microscopy has enabled visualization of the enrichment of titanium (Ti) and the depletion of strontium (Sr) near the dislocation cores. The Ti enrichment and the Sr depletion have been observed at all of the dislocations, and the grain boundary is considered to be Ti excess. The extra Ti ions are located on the positions different from the normal perovskite lattice, suggesting that the local structure is largely reconstructed. It has been proposed that tensile strain at the dislocations may be a cause of the Ti enrichment.

Low‐angle twist grain boundary in SrTiO3 fabricated by spark plasma sintering techniques

“…The dislocations with an [001] edge component, composed of a stacking fault with 2 parallel Ti–O layers, compensate for the relatively small terrace widths of the original (100) SrTiO 3 surface steps that are present prior to diffusion bonding. The atomic (Figures and ) and electronic structures (Figures and ) resemble those previously observed after conventional diffusion bonding . Diffusion bonding in the SPS apparatus, therefore, results in geometrically expected defect structures to accommodate twist and tilt components of the grain boundary, while the dislocation density on the grain‐boundary plane is higher due to the accelerated heating and bonding times.…”

Applications of STEM-EELS to complex oxides

“…While the mechanisms underlying CMR are not completely clear yet, it is widely accepted that minor nanoscale fluctuations of chemical composition can trigger not just CMR but also other manifestations of strong electronic correlations such as orbital ordering or charge ordering [24]. In this scenario, STEM-EELS techniques have been extensively used to simultaneously study the structure, chemistry and electronic properties of perovskite oxides both in bulk and also in low dimensionality environments such as thin films, nanowires, nanostructures, etc [5,9,11,14,23,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In this section we will focus on two examples.…”

Room-Temperature Plastic Deformation of Strontium Titanate Crystals Grown from Different Chemical Compositions

“…In general, point defects act as barriers to dislocation motion and result in work hardening of materials followed by nucleation and growth of cracks, leading to brittle fracture. In fact, both Sr and O vacancies have been reported to be present around dislocations in SrTiO 3 [14][15][16], forming a Cottrell atmosphere [1]. However, the influence of point defects on the dislocation mobility in SrTiO 3 has not been examined.…”