Size and morphology effects on the high pressure behaviors of Mn3O4 nanorods

The high-pressure behaviors of Mn3O4 nanorods were studied by high pressure powder synchrotron X-ray diffraction and Raman spectroscopy. We found that the initial hausmannite phase transforms into the orthorhombic CaTi2O4-type structure, and then to the marokite-like phase upon compression. Upon decompression, the marokite-like phase is retained at the ambient pressure. Compared with Mn3O4 bulk and nanoparticles, Mn3O4 nanorods show obviously different phase transition behaviors. Upon compression, the phase transition sequence of Mn3O4 nanorods is similar with the nanoparticles, while the decompression behavior is consistent with the bulk counterparts. The hausmannite phase shows higher stability and smaller bulk modulus in Mn3O4 nanorods than those of the corresponding bulk and nanoparticles. We proposed that the higher phase stability and compressibility of the nanorods are concerned with their nanosize effects and the rod morphology. Both the growth orientation and the suppressed Jahn–Teller distortion of the Mn3O4 nanorods are crucial factors for their high pressure behaviors.