Спектры комбинационного рассеяния поликристаллических сульфатов лития, натрия и калия в предпереходной температурной области ниже структурного фазового перехода

Molecular relaxation processes in lithium sulfate (Li2SO4), sodium sulfate (Na2SO4) and potassium sulfate (K2SO4) were studied by Raman spectroscopy. A decrease in the order parameter in the low-temperature phase is observed when approaching a phase transition, which, for example, is typical of a first-order phase transition close to the second. The existence of the pretransition region in the studied sulfates Li2SO4, Na2SO4 and K2SO4 was found.