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Homogeneous powders of almost spherical particles of SrTiO3 with diameters of about 1 mu m and large surface areas of up to 186 m(2) g(-1) were obtained from a facile one-pot solvothermal synthesis. Thorough characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), (high-resolution) transmission electron microscopy, and nitrogen physisorption measurements revealed the hierarchical architecture of the particles down to the scale of a few nanometers. In contrast to SrTiO3 samples obtained by high-temperature solid-state reaction, the particles are neither agglomerated nor sintered above the micrometer scale. The samples exhibit enhanced photoelectrochemical properties in a 1.0 M KOH aqueous solution compared to their bulk counterpart. The formation mechanism of the SrTiO3 particles was systematically investigated on the basis of a series of XRD and SEM studies of the products obtained at different reaction temperatures and times. The growth of the hierarchically structured SrTiO3 particles mainly includes two stages: an intermediately formed amorphous TiO2 hydrate transforms in a subsequent step into the final SrTiO3 product. The latter step is a morphology-conserving transformation (pseudomorphosis). Further study indicates that ethylene glycol plays a dominant role in the formation of the hierarchical structures. SrTiO3 particles of polyhedral shapes with smooth surfaces are obtained when ethylene glycol is substituted by the strongly hydrated basic ionic liquid (IL) tetrabutylammonium hydroxide (TBAH) as the solvent.
