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Dielectric relaxation of pure TGS crystals

C. MÎNDRU1, C. P. GANEA2, H. V. ALEXANDRU1,*

Affiliation

  1. Faculty of Physics, University of Bucharest, Romania
  2. National Institute of Materials Physics, Bucharest-Magurele, Romania

Abstract

Pure triglycine sulphate crystals (TGS) show peculiar dielectric behavior in the ferroelectric phase, after crossing down the Curie point. Dielectric dispersion was investigated on the frequency range 1 Hz ÷ 10 MHz. Temperature was changed at a sliding rate of 0.6 o C/minute, crossing up and down, several times, the Curie point between 65 o C and -120 o C. The second component of permittivity, drawn versus the frequency, shows two types of relaxation in the ferroelectric phase, with the characteristic time of τL ~10-3 sec and τH ~10-7 seconds. The first is recognized to be related with ferroelectric domain wall relaxation (domain cropping), although not clearly understood yet. The second one is ascribed to the “critical slowing down” effect, similar to the relaxation in the paraelectric phase, above TC. A third, middle relaxation time, seems to be a sort of interaction of the two previously mentioned relaxation mechanisms. Papers from the literature, analyzing molecular dynamics and structural changes, could not correlate the flipping time ~10-11 sec of the NH3 group of the glycine GI in the structure (the main responsible of the ferroelectric transition), with the mentioned relaxation times. Several aspects of the dielectric parameters evolution, related to the two relaxation processes on the large temperature range shall be analyzed and discussed..

Keywords

Ferroelectric crystals; Triglycine sulphate; Dielectric spectroscopy; Permittivity relaxation.

Submitted at: Feb. 8, 2012
Accepted at: Feb. 20, 2012

Citation

C. MÎNDRU, C. P. GANEA, H. V. ALEXANDRU, Dielectric relaxation of pure TGS crystals, Journal of Optoelectronics and Advanced Materials Vol. 14, Iss. 1-2, pp. 157-162 (2012)