Pressure induced phase transitions in LiNaSO4 Original Research Article

Raman spectroscopic investigations are carried out on LiNaSO4 up to a pressure of 140 kbar. The behavior of the internal modes as a function of pressure suggests a structural transition at Further, the evolution of the Raman spectra suggests that the sulphate ions in the high pressure phase are orientationally disordered in the beginning. Upon subsequent increase of pressure, the misoriented sulphate ions are found to gradually order, and at pressures above 90 kbar, the system gets completely ordered. Comparison of the present results with the high pressure behavior of other binary and disulphates reveal that the increase in cationic size ratio beyond a critical value leads to orientational disordering in the high pressure phases.