Vibrational Spectra of Ion–Molecular Carbonate Crystals in the Pretransition Region near Structural Phase Transitions

Abstract

Molecular relaxation processes in lithium (Li₂CO₃), sodium (Na₂CO₃), and potassium (K₂CO₃) carbonates are studied by Raman spectroscopy. It is found that the first-order structural phase transition in Li₂CO₃, Na₂CO₃, and K₂CO₃ carbonate crystals is extended. The existence of a pretransition region in the studied Li₂CO₃, Na₂CO₃, and K₂CO₃ carbonates is demonstrated.