Phase Transition and vibration properties of MnCO₃ at high pressure and high-temperature by Raman spectroscopy

The high pressure and high-temperature behavior of MnCO₃ was investigated up to 55 GPa at ambient temperature and up to 573 K at ambient pressure by Raman spectroscopy, respectively. Some new modes were detected at ∼16 and ∼32 GPa, which were assigned to MnCO₃-I below 16 GPa and to MnCO₃-II above 32 GPa, and to a coexisting phase of them in between. The high pressure vibration properties of all Raman modes, especially high frequency modes, were systematically reported. The coexisting phase of MnCO₃-I and MnCO₃-II had much easier compressibility than the MnCO₃-II phase. The thermal stability of MnCO₃ was at least to 573 K and its thermal expansion along the c axis was easier than a and b axes.