The structure of the complex oxide PbMnO2.75 solved by precession electron diffraction

Abstract

X-ray diffraction has been used for nearly a century to solve crystal structures and the methods that have been developed make it the prominent method of structure resolution today. Structures have been solved from single crystals of a few tens of µm in diameter or even less using synchrotron radiation techniques. Powders, even if they contain more than one phase, have also been used for X-ray diffraction structure determination. However, with the trend in fundamental research and applications towards materials on the nanometre scale, X-ray diffraction reaches its limits for structure resolution more and more often. Single crystals of less than 1 µm3 are not suitable for X-ray diffraction experiments and powders always present the difficulty of peak overlap that in the case of complex phases often prevents the determination of the cell parameters, without even speaking of structure determination. In these cases electron crystallography can be a powerful tool for the determination of the atomic structures of crystals. Its advantages are the fact that an individual nanometre-sized particle can be used as a single crystal for electron diffraction and in the possibility to obtain real space images of atomic resolution. The “classical” electron diffraction suffers from multiple scattering which prevents a simple relationship between the measured intensities and the structure factor amplitude. Therefore precession electron diffraction, which largely reduces multiple diffraction, has to be used to obtain reliable diffraction data.