Functional Ceramics

Perovskite oxides such as strontium titanate (SrTiO₃) and barium titanate (BaTiO₃) are cornerstone materials in modern electronics and energy technologies. Their unique combination of ionic, electronic, and ferroic functionalities underlies a broad range of applications from capacitors, sensors, and varistors to solid oxide fuel cells and resistive memory devices. What makes these materials particularly fascinating is their tunability: subtle changes in composition, defect chemistry, or local structure can drastically alter their dielectric behavior, conductivity, and even catalytic performance. Understanding how these properties emerge from the atomic structure is therefore a central challenge in materials science.

At the heart of this complexity lie interfaces and grain boundaries, where the structural symmetry breaks and electronic charge redistributes. Dopant atoms tend to segregate at these boundaries, forming so-called space-charge layers that govern ionic transport, local potential barriers, and charge compensation mechanisms. These nanoscale features, though occupying only a small volume fraction, have a decisive influence on the macroscopic performance of perovskite ceramics. For example, they can control grain growth, modify conductivity, and dictate long-term stability during device operation or high-temperature cycling.

Advanced transmission electron microscopy (TEM) now makes it possible to directly visualize these local structures and their chemistry with near-atomic precision. Techniques such as scanning TEM (STEM) combined with electron energy loss spectroscopy (EELS), energy-dispersive X-ray spectroscopy (EDX), and differential phase contrast (DPC) imaging reveal how atoms rearrange, how dopants segregate, and how electronic states evolve across interfaces. When coupled with in-situ heating experiments and quantitative orientation or strain mapping, these approaches uncover how grain boundaries and defect networks change dynamically under realistic conditions.

Through such analyses, researchers aim to establish a direct link between atomic-scale structure, electronic configuration, and macroscopic functionality in perovskite oxides. By correlating structural order, defect chemistry, and Fermi-level variations, we can begin to rationally design materials with tailored electrical, ionic, and thermal behavior. This understanding does not only shed light on the fundamental physics of complex oxides but also informs the development of next-generation functional ceramics for sustainable energy and electronic technologies.

Details to this work have been published at

• Wang, D. et al. Grain boundary segregation in iron doped strontium titanate: From dilute to concentrated solid solutions. Acta Mater., 2024, 273, 119941.