Structural deffects and diffuse scattering in brownmillerites

The aim of this proposed project is a comprehensive study of brownmillerite-type materials, regarding their structures, phase transitions, and in particular, their defects and disorder phenomena. Brownmillerites are important phases in cement clinkers, but they also have numerous applications in catalysis and other technological fields. For a better understanding of their properties, investigation of their structural features at the nanoscale is important. A choice of compounds has been selected, which show interesting structural features in simple binary brownmillerite systems: Ca2 (Fe,X) 2 O5 , with X=Al, Ga and Mn. These samples show phase transitions, antiphase boundaries and disorder proven by the occurrence of diffuse scattering. Furthermore, the class of layered brownmillerites Ca4 (Fe,Mn,X) 3 O9 (with X=Al and Ti), which show strong diffuse scattering, will be investigated. To achieve the targets of the project, sophisticated knowledge in diffuse scattering and modelling of disordered structures, as well as electron microscopy and the corresponding experimental facilities are needed. Therefore, the Research School of Chemistry (RSC) at the Australian National University was chosen as host institution of the project. The groups Disordered Materials and Solid State Inorganic Chemistry, headed by Prof. T. R. Welberry and Prof. R. L. Withers, respectively, are world-renowned in these fields. Moreover, the needed experimental equipment and expertise is available at the RSC: Prof. Welberry`s purpose-built diffractometers are the best laboratory instruments for recording the weak diffuse scattering from disordered materials. Two transmission electron microscopes are available for electron diffraction, high-resolution and in-situ high-temperature experiments. Combined with the outstanding experience in Monte Carlo simulations of disordered structures, the RSC, namely the research groups of Welberry/Withers, are the best possible host for this project. Apart from the primary research targets, the knowledge and experience, which will be gained in this project, will be a benefit for the Austrian scientific community. After the return of the applicant he will continue practising analysis of disordered materials in Austria with the aim of establishing the methods as routine tools. This methodology is of interest for many scientist not only in mineralogy/crystallography, but also in the fields of solid state chemistry, materials science and even pharmacy.