DIELECTRIC-PROPERTIES OF TRIGLYCINE SELENATE FERROELECTRIC NEAR THE PHASE-TRANSITION TEMPERATURE

The results of nonlinear-susceptibility experimental investigations ar e given. It has been confirmed that the dielectric data obtained in th e ferroelectric phase can be interpreted on the basis of Landau-tricri tical-point theory with equation of state E=A tau P+CP5, where T-t=(29 5.73+/-0.01) K, A=(1.172+/-0.003) x 10(10) V-2 J(-1) m, C=(1.46+/-0.03 ) X 10(15) V-6 J(-5) m(9). On the other hand, the paraelectric phase m easurements results indicate neither critical nor tricritical Landau b ehavior. The experimental evidence of such a duality is presented.