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2024-11-22 2:06

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Conference: Bucharest University Faculty of Physics 2004 Meeting

Section: Solid State Physics and Materials Science

Title:

Dielectric characteristic of pure and doped TGS crystals

Authors:

H.Alexandru(1), C.Berbecaru(1), A.Dutu(1), L.Pintilie(2)

Affiliation:

(1)Bucharest University

(2)National Institute of Materials Physics Bucharest-Magurele, Romania

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Keywords:

dielectric crystals,ferroelectrics,hysteresis

Abstract:

Pure TGS crystals show higher and non-reproducible permitivity and losses in the ferroelectric phase, after crossing down the Curie point [1]. In contrast, doped TGS crystals (with L or D-alanine) show stable ferroelectric parameters, much lower permitivity and losses, higher polarization and pyroelectric coefficients, i.e. higher figure of merit of materials for IR detector applications. Hysteresis loop (HL) of the samples were recorded with a Sawyer-Tower modified circuit and Tektronics digital TDS 210 oscilloscope and saved on the computer. Peculiar behavior has shown HL of (L+D)-alanine doped crystals. Pyroelectric coefficients were recorded with computer controlled Keithley 6517 electrometer. Peak value of the pyroelectric coefficients of L versus D alanine doped TGS crystals shows a remarkable asymmetry, crossing up and down the Curie point. Doped samples show a peculiar dependence of the two unequal P+/P-- polarization components on the AC measuring field. A modeling procedure was realized by simulation of the bias field induced in pure TGS crystals, using a DC field. It has been previously shown [2] that un optimized DC electric field, applied on the doped pyroelectric wafer can increase the pyroelectric coefficient about four times at room temperature. References: [1] H.V.Alexandru, C.Berbecaru, Ferroelectrics 202 (1997) 173. [2] L.Pintilie, I.Matei, Ioana Pintilie, H.V.Alexandru, C.Berbecaru, Proceedings MRS, Boston, USA, Nov.2001, C7.13, pag.1-6.