CHARACTERIZATION OF FERROELECTRIC PHASE-TRANSITION IN GPI CRYSTAL

The dielectric behaviour of a glycine phosphite [GPI: Gly . H3PO3] cry stal is investigated around its ferroelectric phase transition. The te mperature dependence of the dielectric constant is measured for de bia s fields up to 200 kV/m. The dielectric constant is also measured in t he paralectric phase as a function of electric field at constant tempe ratures. The results are discussed on the basis of the classical state equation and the equation coefficients are estimated. The obtained re sults lead to the conclusion that the ferroelectric phase transition i n GPI has an intermediate character between critical and tricritical o ne.