Morphology-tuned phase transition of MnO₂ nanorods under high pressure

The structural phase transition of MnO₂ nanorods was investigated using in situ high pressure synchrotron x-ray diffraction (XRD) and transmission electron microscopy (TEM). At pressures exceeding 10.9 GPa, a second-order structural phase transition from tetragonal to orthogonal, which was accompanied by fine-scale crystal twinning phenomena, was observed in MnO₂ nanorods. On account of the significant contribution of surface energy, the phase transition pressure exhibited appreciable hysteresis compared with the bulk counterparts, suggesting the enhanced structural stability of nanorod morphology. These findings reveal that the size and morphology exhibit a manifest correlation with the high pressure behavior of MnO₂ nanomaterials, providing useful insights into the intricate interplay between structure and properties.