Stages in ferroelectric transition of TGS

• Published in: Ferroelectrics 2019-10, Vol.551 (1), p.211-228
• Main Author: Alexandru, H. V.
• Format: Article
• Language: English
• Subjects: activation energies; conductivities; Conductivity; Crystal growth; Crystals; Curie temperature; Evaporation; Ferroelectric crystals; Ferroelectric materials; ferroelectric unstable stage; Ferroelectricity; limited transition; Parameters; Temperature; Temperature dependence; TGS dielectric spectroscopy; Triglycine sulfate
• ISSN: 0015-0193; 1563-5112
• DOI: 10.1080/00150193.2019.1658048

Ferroelectric crystal triglycine sulfate (TGS) present distinct properties, in the ferro phase, on four temperature stages: Tc-45-40-35-30 (25)°C for all measured parameters. The lower limit of the ferroelectric transition was for first time estimated to be about 24 °C down the Curie point. Crystals grown by slow solvent evaporation in para phase, were cleaved and polished plates were silver paste painted as electrodes. Alpha-A Novocontrol spectrometer was used for dielectric spectroscopy measurements (1-10 6 Hz), crossing down-up-down the Curie point, between 65 °C and −120 °C at a pace of 0.6 °C/minute. Surprisingly, in all three runs Z2, Z3, Z5 crystal properties appear unstable on the temperature interval 45 °C-Tc. In the run Z3, the conductivity falls down two order of magnitude, 4 °C before crossing up the Curie point. The frequency coefficient N shows distinct ranges of linear temperature dependence on the interval 25-45 °C showing, in Arrhenius coordinate, the activation energies close to the values of A.C. conductivity. On the zone 45 °C-Tc, N coefficient shows also a non-Arrhenius temperature dependence. At the other end, down 25 °C towards zero Celsius, N increases rapidly from 0.2 towards 0.8, suggesting the influence of the ferro transition was closed. Literature data of some other parameters were listed, to sustain the temperature stages.