In Situ X-ray Scattering of Tin Oxide Nanoparticles during Chemical Vapor Synthesis

Gas phase production processes of nanoparticles (NPs) such as Chemical Vapor Synthesis (CVS) enable the generation of NPs with high purity, crystallinity, narrow size distribution, and a low degree of hard agglomeration. The design of materials with desired properties is enabled by a control of CVS process parameters, which demands a fundamental understanding of CVS. Ex situ investigation of the CVS process may suffer from artifacts due to particle collection, oxidation, or aging. This may be circumvented by in situ studies. Such studies are described here using small- and wide-angle X-ray scattering of tin oxide NPs as a model system. We demonstrate the formation of crystalline order as well as variation of morphology, size, and agglomeration as a function of process temperature and pressure. Results are compiled in a size-temperature pseudo-phase diagram of the CVS process.