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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:52 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Solid State Physics and Materials Science
Title:
Investigation of Rochelles salt properties around high Curie temperature point
Authors:
Adrian Rotaru(1), Laurentiu Sufaru(2), Ciceron Berbecaru(1,2)
Affiliation:
(1)Faculty of Physics, University of Bucharest,Electricity and Magnetism, Solid-State Physics, Biophysics Department
(2)Laboratory for Materials Science and Crystal Growth
Faculty of Physics, University of Bucharest
Romanian Materials Science – Crystal Growth Society,
Bucharest – Magurele 077125, Romania
E-mail
rotarue@gmail.com ; laurentiu16@lycos.com ; berbecaru2ciceron@gmail.com
Keywords:
Rochelle salt crystals, permittivity and losses, piezoelectric measurements.
Abstract:
Pure Rochelle salt (RS) crystals were grown from aqueous solutions, by slow decrease of temperature. Fresh cleaved, polished and silver paste painted samples of ~ 0.6 cm2 surfaces and ~1.2 mm thickness were investigated in the + 18 – +30 grd C and 42 Hz – 5 MHz temperature and frequency ranges. Permittivity and losses, tan delta, were temperature and frequency investigated using a Hioki 3532-50 type automatic RLC bridge in line with a computer and GPIB interface, for automatic registering and subsequent processing of the experimental data with specialized software. Some measurements were automatically performed using a homemade automatic thermostatic system, heating and cooling the samples around the high Curie temperature (HCP). Pure crystals display reproducible values of permittivity and dielectric losses, in the limits of the experimental errors, crossing up and down HCP temperature, ~24 grd C. Temperature and time evolutions of ferroelectric domains are responsible for this behavior. For pure RS crystals, losses in the ferroelectric phase shows higher values related to paraelectric phase. All investigated parameters (permittivity and losses) shows decreasing values with the frequency increase, except some peculiar frequencies. Piezoelectric investigations were also performed around HCP. Smaller differences between the resonant and antiresonance frequencies were registered compared with fresh grown crystals. Also electromechanical coupling k and piezoelectric coefficient d14 shows smaller values than fresh grown crystals. These behaviors demonstrate the importance of crystallization water in the piezoelectric response of the RS crystals, the loss of water lowering the values of measured parameters.
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