2022-07-01 16:40


Conference: Bucharest University Faculty of Physics 2019 Meeting

Section: Solid State Physics and Materials Science

Structure and Order in Ferroelectric Transition of TGS

Horia V. ALEXANDRU(1,2), Marinel DAN(1), Constantin Paul GANEA(3)

1) University of Bucharest, Faculty of Physics

2) Academy of Romanian Scientists

3) National Institute of Materials Physics - Bucharest Magurele



Triglycine sulphate crystal (TGS for short) has a typical second order phase transition around 49oC and has important applications in IR detection. Despite the abundant available literature, it lacks the AC conduction data around the transition and the description of stages in the ferroelectric state. In this contribution we intend to present some intriguing aspects near the transition point, the sequential distribution of parameters in ferro phase and the temperature extension of transition. Pure single crystals were grown from solution, in para phase at 52oC, by slow solvent evaporation. Dielectric dispersion of a pure TGS sample was studied on a large frequency (1-107 Hz) and temperature (-120 to +65oC) ranges, crossing up and down the Curie point (CP) several times. After the first up and down run through the CP, both components of permittivity increases more than one order of magnitude in ferroelectric phase. The system become metastable due to the relaxation process of ferroelectric domains. Two type of relaxation were highlighted. The higher frequency one, with a typical relaxation time τH ~ 10 -7 sec, has a non-Arrhenius temperature dependence and is related to the “critical slowing down” mechanism due to the long distance order in the lattice. The lower frequency relaxation (τL~10-3-10-1 sec) related with ferroelectric domain cropping has an Arrhenius thermal dependence with the activation energy of 0.7 eV (~28 KBT). An unusual middle frequency relaxation (τM~10-6-10-3 sec.) related to the higher frequency one, was found only on the Tc-35oC limited range, showing the influence extension of the ferroelectric transition.