Critical Indices of the Ferroelectric Phase Transition in TGS Crystals

Abstract

Temperature dependencies of retardation, electron susceptibility and linear thermal expansion for three crystal-physic directions are obtained by means of optical investigations of the ferroelectric phase transition in TGS crystal using the James-type interferometer. Temperature dependencies of the spontaneous changes of the characteristics studied in the 39-49 • C range are fitted by the power low Y ∼ τ 2β with double critical indices 2β=0.87-0.95. Difference of 2β values from the unity is explained by the essential temperature dependence in the range close to the phase transition point for the coefficients of electrooptic, reversed piezoelectric and electrostriction effects.