OPTICAL-AND-REFRACTIVE INVESTIGATIONS OF CRITICAL INDICES OF PHASE TRANSITIONS IN CRYSTALS

Bohdan Andriyevskyy

Koszalin University of Technology

Temperature dependences of the refractive indices and linear thermal expansion of TGS in the range of phase transition (PT) were already studied [1-3], but the corresponding critical indices have not been determined. The goals of the present investigation were precise measurements of temperature dependences of interferometric retardation of the sample-air type for the TGS in the range of 2nd order PT at 322 K, calculation of the temperature dependences of refractive indices and linear thermal expansion for the main crystal physics directions, and the study of these dependences using the corresponding critical indices 2β.
[1] A.S. Sonin, A.S. Vasilevskaya. Electrooptical crystals. Atomizdat, Moscow, 1971 (in Russian).
[2] L.G. Lomova, A.S. Sonin, T.A.Regulskaya. Spontaneous electrooptic effect in the triglycine sulphate single crystals. Kristallografiya, 13, No 1 (1968) 90 (in Russian).
[3] N.A. Romanyuk, A.M. Kostetskii, B.V. Andrievskii. Dispersion of the refractive index and some characteristics of absorption spectra for triglycine sulphate crystal’s group. Phys. Solid State, 19, No. 10 (1977) 1809.
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