Speaker
Description
Strontium titanate (STO) is a material with promising properties for applications in thermoelectricity, catalysis, fuel cells and other fields but its properties are highly sensitive to stoichiometry and the presence of impurities and other defects, particularly grain boundaries. Transmission electron microscopy (TEM) has been instrumental in studying the atomic-scale structure of STO; however, it provides limited chemical and three-dimensional information. These gaps can normally be filled by using atom probe tomography (APT) but this has faced challenges in analyzing STO, particularly the early fracture of specimens. In this study, we demonstrate that metal-coated STO specimens can be successfully analyzed, with nearly 100% yield. We apply this method to both undoped and 1 at% Nb-doped STO, achieving a sensitivity capable of detecting as little as 0.7 at% Nb. Additionally, we report on successful APT analysis of a bicrystal STO grain boundary. Direct comparison with scanning transmission electron microscopy (STEM) of the facetted grain boundary reveals a Sr depletion of 30% within a 2 nm wide region. This work presents a robust APT methodology for reliable, high-resolution chemical analysis of STO at the nanometer scale.
