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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:28 |
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Conference: Bucharest University Faculty of Physics 2002 Meeting
Section: Solid State Physics and Materials Science
Title:
Hysteresis Loop Simulation Of Doped Tgs Crystals
Authors:
H.V.Alexandru, C.Berbecaru, M.Lisca, L.Nedelcu
Affiliation:
Faculty of Physics, University of Bucharest
E-mail
Keywords:
Abstract:
Triglycine sulphate crystal (NH2CH2COOH)H2SO4 –TGS, is intensively studied for infrared and gas detector applications. Pure TGS crystals exhibit unstable dielectric permytivities due to non-reproducible domains re-polarization in ferroelectric phase. Pure and doped TGS crystals where grown by solvent evaporation in paraelectric phase at 5254 oC. L or D alanina was used as dopant at molar concentration in solution of ~60 %. The growth rates, the dopage and the parameters along the “b” ferroelectric axis of the crystals are quite different in opposite directions.
A modified Sawyer-Tower circuit, in line with Tektronics TDS 210 digital oscilloscope and computer was used to record the hysteresis loops (HL) versus the ac measuring electric field and temperature. Several distortions of the HL have been noticed. All components P+, P, coercive field EC and bias field EB depend on the applied electric field in a peculiar manner. The maximum value of P+ 3.54.0 C/cm2 was recorded, at a.c. field of ~3 kV/cm, which exceed the usual value of PS 2.72.8 C/cm2 for pure TGS.
A sample showing an unusual distorted HL, with a surface of ~0.8 cm2, was scanned on 24 locations, separated by scratching one electrode. The panel of the recorded HLs shows indeed, that the bias field corresponding to dopage, depends on the growth zone corresponding to particular crystallographic faces.
A simulation of TGS dopage was made using several bias fields values, superposed to the measuring a.c. field, on recorded HL. There is a qualitative agreement of the simulated parameters with the parameters of the doped crystals, but not in details.
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