Temperature dependence of Cole-Cole and dielectric strength parameters of TGS crystal

ABSTRACT

The well known ferroelectric crystal triglycine sulphate (TGS) still shows new interesting aspects, walking up and down the temperature through the Curie (∼ 49°C) point, on large temperature and frequency range (1–10⁷ Hz). Crystals were grown at 54°C, in paraelectric phase, by slow solvent evaporation in order to avoid mechanical tension due to domains present in ferro phase. Silver paste was used to paint electrodes on the cleaved and polished samples. Both components of permittivity vs. frequency were continuously measured, sliding down the temperature at a rate of 0.6°C/min, using Alpha-A Novocontrol spectrometer. The Cole-Cole diagrams of high (H) and low (L) frequency relaxation was drawn at several temperatures, in two versions “as measured” and “NO losses” (corrected for conduction), in order to discern the influence of conductions at several frequencies. The essential parameters of arcs Cole-Cole (the radius and the circle coordination centers) of H/L relaxation shows different temperature dependences down the Curie point till the room temperature. The remarkable pattern of slope changes appear at the temperatures 35°C, 41°C and 46°C in several representations, which are probably related with the crystal lattice dynamic. About 40°C seems to be the limit of transition influence on the ferroelectric parameters.

KEYWORDS:

• Ferroelectrics
• dielectric spectroscopy
• conductivity
• two type of relaxation

Acknowledgments

The authors are really indebted to Dr. Constantin Paul Ganea from the National Institute of Materials, Bucharest-Magurele, for experimental data registration and for excellent collaboration.