In situ spectroscopy in solid state chemistry

Spectroscopic studies can provide information on a large variety of physica l and chemical processes in solids. In this contribution, we report on stud ies of homogeneous, and heterogeneous solid state reactions as well as on s tudies of diffusion processes in complex oxides. Examples have been drawn f rom work performed by means of optical spectroscopy and Mossbauer spectrosc opy under in in situ conditions at high temperatures and at defined oxygen partial pressures. Examples for homogeneous reactions refer to order-disord er processes and their kinetics in nickel aluminate spinel and magnetite. S tudies of heterogeneous solid-solid and solid-gas reactions relate to the f ormation of cobalt aluminate spinel and to redox processes in fayalite, Fe2 SiO4. respectively. The diffusion of the iron cations in Fe2SiO4, has been observed by means of Mossbauer spectroscopy. Finally, an example is given o f the application of Mossbauer spectroscopy for providing insight into mech anically induced reactions (mechanochemistry) in a spinel. (C) 2001 Elsevie r Science B.V. All rights reserved.