Study of the Second-Order Ferroelectric Transition in Tri-Glycine Sulfate

Concepts

Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsMaterials PhysicsSolid State PhysicsDielectric MaterialsDielectric PropertiesDielectric ResponseDielectricsFerroelectric MaterialsPhase TransitionsDielectric ConstantFerroelectric Dielectric ResponseFerroelectric PropertiesFerroelectricityPolarizationSpontaneous Polarization

Abstract

Results of measurements of the dielectric constant, dielectric nonlinearity and spontaneous polarization of tri-glycine sulfate are given. These data demonstrate clearly that this material exhibits a second-order ferroelectric transition. The properties discussed are described in terms of the usual expansion of the free energy in even powers of the polarization F(P,T)=F(O,T)+A(T-T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> )P 2 +BP 4 +CP 6 , where A,T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> ,B and C are constants and T and P are the temperature and polarization, respectively. From the various data taken it is found that A=1.96×10 −3 (°C) −1 , T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> =49.8°C,B=2.0×10 −10 (esu/cm 2 ) -2 and C=8.4×10 −19 (esu/cm 2 ) −4 . From these results the nonlinearity of the dielectric constant above the Curie point is calculated at various temperatures.