Ukrainian Journal of Physical Optics 

R.Vlokh, O.V.Vlokh, I.Skab, I.Girnyk

The given part of this review paper is devoted to the collection and analysis of experimental results obtained by different researches that have investigated the temperature dependencies of birefringence as well as Raman scattering and IR spectrums of langbeinites at phase transitions. Given paper shows that optical methods of investigation of phase transitions particularly in langbeinites lead to obtaining important information about the temperature behavior of order parameter and lattice dynamic at phase transition. For example on the base of birefringence study of the isolated point of second order phase transition on the line of the first order was found on the concentration-temperature phase diagram of K₂Cd_2xMn_2(1-x)(SO₄)₃ solid solutions. On the base of Raman scattering spectrums study one can conclude that phase transitions in langbeinites are of order-disorder type with ordering of the sulfate anions.

Key words: langbeinites, phase transition, Raman scattering, birefringence.

PACS: 42,33.SS-b.,77.80.B,78.20.Jq,78.30.-J

doi 10.3116/16091833/3/4/231/2002

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