Size and morphology effects on the high pressure behaviors of Mn 3 O 4 nanorods.

The high-pressure behaviors of Mn 3 O 4 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 CaTi 2 O 4 -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 Mn 3 O 4 bulk and nanoparticles, Mn 3 O 4 nanorods show obviously different phase transition behaviors. Upon compression, the phase transition sequence of Mn 3 O 4 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 Mn 3 O 4 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 Mn 3 O 4 nanorods are crucial factors for their high pressure behaviors.