Matrix-mediated formation of hierarchically structured SnO crystals as intermediates between single crystals and polycrystalline aggregates

Crystalline SnO grown in a Sn₆O₄(OH)₄ matrix exhibited hierarchical architectures, such as stepped bipyramids, stacked meshes, and rosettes, which were not categorized into the classical assortment of crystal morphologies. The complex architectures consisting of small building units were found to be produced through stacking and/or branching growth accompanied with a decrease in the unit size and degradation of the crystallographic symmetry in their assembly. This particular morphological evolution is presumed to be achieved by increasing the driving force of crystallization in the presence of abundant precursor species supplied from the matrix.