Variety of Aggregation and Growth Processes of Lanthanum Fluoride as a Function of La/F Activity Ratio. 2. Excess of F over La Region. Transformation of Amorphous to Crystalline Phase, POM, SAXS, WAXS, and XRD Study

Preparation of lanthanum hydroxy-fluorides using steady-state pF-stat experiments, which ensures constant, very low concentrations of the precipitation components and constant pH during the whole growth process, results in a structural evolution of objects with defined physical parameters and a variety of nonconventional morphologies. This structural evolution was characterized by a combination of techniques, namely, static and dynamic light scattering (SLS and DLS), small-angle and wide-angle X-ray scattering (SAXS and WAXS), X-ray diffraction (XRD), and polarized optical microscopy (POM). It is shown that after the immediate formation of an amorphous glassylike precursor, crystalline nanoparticles of high structural definition and monodispersity transit into hollow spheres with diameters of several hundred nanometers. These large vesicles contained smaller ones, which have shown the Maltese cross. After vesicle deformation and elongation into fibers with extreme length, the nanocrystals are transferred ...