A combined experimental and theoretical approach to atomic structure and segregation at ceramic interfaces

In the last few years, the scanning transmission electron microscope has be come capable of forming electron probes of atomic dimensions. This makes po ssible the technique of Z-contrast imaging, a method of forming direct imag es at atomic resolution with high compositional sensitivity. Atomic column positions can be determined to high accuracy from the image, and columns co ntaining high-Z impurities will be visible. Atomic resolution electron ener gy loss spectroscopy is possible by locating the probe over particular atom ic columns or planes seen in the image. This provides complementary informa tion on low-Z species and chemical bonding. Such data represents an ideal s tarting point for first-principles theoretical calculations of energetics a nd dynamics, avoiding time-consuming searches of trial structures. Examples are shown of ordering in relaxer ferroelectrics, interfacial termination i n oxide-oxide and metal-oxide interfaces, and an impurity-induced structura l transformation of a ceramic grain boundary. Published by Elsevier Science Ltd.