New method to acquire in situ information on crystal structures changed by chemical reactions.

In this project, we will be the first to determine structural changes at unit cell level during oxidation and reduction processes in situ in gasses and liquids with electron diffraction tomography. In situ means that the data is collected on the sample while it is still in the environment where the reaction occurred. Such oxidation and reduction processes are important in the field of energy materials, a research field with very high activity worldwide as sustainable energy is of vital importance for our whole society. Changes in structures under oxidation and reduction processes dictate ion conduction paths and reversibility, thus efficiency, capacity and lifetime of the different technologies. Such structural changes are currently followed using X-ray and neutron powder diffraction techniques, because the materials are usually only active as submicron particles. Although these techniques can uncover very important structural changes, they are often plagued by peak overlap of different phases and peak broadening due to the small crystal sizes, making the results less conclusive and leaving some structures unsolved. Using electrons will allow performing in situ single crystal experiments on the individual particles within a powder sample, due to the much stronger interaction between electrons and matter. Single crystal data has a lot of advantages over powder diffraction data for structure determination and will allow uncovering information and determining structures out of reach of in situ powder diffraction techniques. Precession electron diffraction tomography is already used for structure determination from ex situ single crystal data. Using this technique in situ, we will monitor how structures of materials change under oxygen atmosphere or reducing hydrogen atmosphere, under hydration or carbon dioxide, or under electrochemical oxidation and reduction. Our goal is to be the pioneers in using this technique of in situ PEDT and to demonstrate to the international materials science community the high value of the technique by providing missing structural information on several compounds from the field of energy materials. The compounds are selected from the fields of lithium-ion and polyanionic battery materials, solid oxide fuel cells, proton conducting fuel cells and chemical looping in order to reach a wide audience.

Keywords:STRUCTURE EVOLUTION, ENERGY TECHNOLOGY, STRUCTURE DETERMINATION, TEM

Disciplines:Phase transformations