Structural phase transitions in K₂CO₃(Raman scattering study)

Structural phase transitions in K 2 CO 3 have been investigated using light scattering techniques. The Raman spectrum of the high-temperature hexagonal phase consists of a very broad structureless band which suggests that the system is highly anharmonic. Below the hexagonal-monoclinic transition at T cl =693K the authors observe a soft mode which is assigned to librational motion of the CO 3 groups. Evidence of a cell doubling transition at T c2 =526K is found in the number of Raman active modes observed at low temperature, although a soft mode is not observed at the transition.