Phase transitions of tridymite MC: A low frequency Raman spectroscopic study

In-situ high-temperature Raman spectra of tridymite starting from MC modification were measured up to 500 °C. Low frequency Raman spectra (ν = 15-100 cm-1) of the high-temperature modifications (OP, OS, OC, and HP) were reported for the first time. It was noted that there are significant changes in the low frequency region upon the transitions, and those transition temperatures are consistent with those reported in previous studies except OC/HP transition. The OC/HP transition was detected at around 470 °C. This temperature is about 70 °C higher than the transition temperature determined by previous X-ray diffraction studies. The disagreement on the transition temperature is discussed.