UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Solid State Physics and Materials Science


Title:
Temperature and frequency dependence of the electrical parameters in the ferroelectric transition of the TGS crystals


Authors:
M. Budes, C. Berbecaru, H.V. Alexandru


Affiliation:
University of Bucharest, Faculty of Physics, Bucharest, Romania


E-mail
matei.budes@yahoo.com ; berbecaru2ciceron@yahoo.com ; horia@infim.ro


Keywords:
pure and d:alanina doped TGS crystals, electrical parameters, temperature and frequencies investigations


Abstract:
Pure and d:alanina doped TGS crystals were grown in dynamic or static regime, [1]. Samples of ~1cm2 surfaces and ~1.4 mm thickness were investigated in the temperature range -20 ÷ +65 degC and 120 Hz ÷ 5 MHz frequency range. Electrical parameters: permittivity and losses, serial and parallel capacity Cs, Cp, serial and parallel resistance Rs, Rp were temperature and frequency investigated using a Hioki 3532-50 type automatic RLC bridge in line with a computer for automatic registering and subsequent processing of the experimental data. Pure crystals show nonreproducible values of the permittivity and dielectric losses crossing up and down the Curie point. More stable and much lower values of the permittivity and dielectric losses could be noticed for the dielectric permittivity of d:alanina doped crystals as previously shown, [2]. Rs and Rp of the electric equivalent circuit of the crystals shows minima around the Curie temperature, 49 degC. Much higher values of Rs, Rp were found for d:alanina doped crystals due to pining of the polarization induced by the dopant. For pure and doped TGS crystals, losses present a complicated pattern of evolution versus temperature with much lower values in the paraelectric phase. All investigated parameters show decreasing values with the frequency increase. Our experimental results point out for a more stabilized structure with decreased mobility of the dipoles in the structure of the doped versus pure TGS crystals. [1] H.V. Alexandru, C. Berbecaru, Cryst. Res. and Technol., 30 (1995) 307. [2] C. Berbecaru, H.V Alexandru, Mater.Sci.Eng. B 118 (2005) 141.