Time-resolved in situ powder X-ray diffraction reveals the mechanisms of molten salt synthesis

We report the first use of high-energy monochromatic in situ X-ray powder diffraction to gain unprecedented insights into the chemical processes occurring during high temperature, lab-scale metal oxide syntheses. During the flux synthesis of the n = 4 Aurivillius phase, Bi5Ti3Fe0.5Cr0.5O15 at 950 degrees C in molten Na2SO4 we observe the progression of numerous metastable phases. Using sequential multi-phase Rietveld refinement of the time-dependent in situ XRD data, we are able to obtain mechanistic understanding of this reaction under a range of conditions.