UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-22 1:46
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Conference: Bucharest University Faculty of Physics 2010 Meeting


Section: Solid State Physics and Materials Science


Title:
Frequency investigations of the electric properties of TGS crystals


Authors:
Carmen Mandru Munteanu, Aida Apaz Ghiulnare, C. Berbecaru, A. Dafinei, H.V. Alexandru


Affiliation:
University of Bucharest, Faculty of Physics,

Romanian Materials Science – Crystal Growth Society, 077125 Bucharest, Romania,


E-mail
krmen63@yahoo.com ; aidutza_handy@yahoo.com ; berbecaru2ciceron@yahoo.com ; asdafinei@yahoo.com ; ria@infim.ro


Keywords:
pure and doped TGS crystals, temperature and frequency dependences of permittivity, Cole-Cole representations


Abstract:
Pure and D alanine doped triglycine sulphate (TGS) crystals were grown from aqueous solutions and some important characterization has already been made [1-4]. Temperature and frequency dependence of the dielectric parameters shall be jointly presented. Fresh cleaved, polished and silver painted samples were analysed. Pure TGS crystals show non reproducible values of the permittivity and dielectric loss crossing up and down the Curie point. Much more stable and much lower values of the permittivity and dielectric losses could be noticed for D alanine doped crystals. Permittivity and losses of pure TGS crystals show different frequency behaviour related to polar (ferroelectric) or nonpolar (paraelectric) state of crystals. Components of the complex permitivity were represented as Cole-Cole diagrams (C-C) at several temperatures, on the frequency range 45 Hz - 5 MHz. Coming from para to ferroelectric state, C-C diagrams surprisingly show two type of relaxation at low and high frequencies, having a different evolution in time. The mechanism of these relaxations and theirs time evolution is not clear yet and was not presented in the literature. Much smaller and stable values of permittivity and loss, vs. temperature and frequency, were found for doped crystals. Experimental results point out for a more stable structure with dipoles mobility decreased of doped vs. pure TGS crystals. Higher figure of merit of doped TGS crystals point to a major advantage for technical applications. References: [1] H.V.Alexandru, C.Berbecaru et al, Sensors and Actuators, A 113 (2004) 387-392 [2] H.V.Alexandru, C.Berbecaru et al, Applied Surface Science 253 (2006) 358-362 [3] C.Berbecaru, et al, Materials Science and Engineering: B 118 (2005) 141-146. [4] C. Berbecaru, Physica Status Solidi C 7 (2010) 1440– 1443.