Synthesis and characterization of β-MnO2 single crystals with novel tetragonous morphology

β-MnO2 single crystals with novel tetragonous morphology have been hydrothermally prepared in an HCl solution at 180 °C for 24 h without using templates, catalysts, and organic reagents. The structure of the obtained β-MnO2 was systematically investigated by X-ray diffraction, SEM and TEM microscopy, FT-IR spectroscopy, DSC–TGA analyses, and chemical compositional analyses. The morphology of β-MnO2 could be controlled by the hydrothermal treatment temperatures and the hydrothermal reaction times. β-MnO2 single crystals with diameters 200–600 nm and lengths up to 1–5 μm not only had novel tetragonous morphology, but also had high purity.