Phase Transition of BaCO3 Under High Temperature and High Pressure

Aiming at exploring the phase transition behavior of BaCO3 under high temperature and high pressure, the differential scanning calorimeter (DSC) was employed to characterize the process of phase transition of BaCO3 from room temperature to 1 200 ℃, and Raman spectrometer was adopted to analyze the phase transition features of BaCO3 from atmospheric pressure to 15.2 GPa. According to the DSC analysis results, there were two endothermic peaks of BaCO3 at 808 ℃ and 955 ℃, which corresponded to the transitions of orthorhombic phase to trigonal phase and trigonal phase to cubic phase, respectively. When the pressure rose from atmospheric pressure to 10.6 GPa, the frequency shift of all Raman modes of BaCO3 increased monotonically, and no phase transition of BaCO3 was found under the pressure below 10.6 GPa. The phase transition of BaCO3 from orthorhombic (Pmcn) to trigonal (P31c) structure occurred around 10.6 GPa, and no further change in BaCO3 phases could be recognized in the spectra when the pressure exceeded 10.6 GPa. From the Raman spectra of pressure released BaCO3, v1 symmetric stretching band of the [CO3] did not retrogress from high pressure phase (trigonal structure) of BaCO3 to ambient phase (orthorhombic structure). © 2019, Materials Review Magazine. All right reserved.