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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 17:59 |
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Conference: Bucharest University Faculty of Physics 2017 Meeting
Section: Solid State Physics and Materials Science
Title:
Investigation of the electric parameters of BaTiO3 ceramics around ferroelectric-paraelectric phase transition
Authors:
Florin RADULESCU (1), Ciceron BERBECARU (1,2)
Affiliation:
1) Bucharest University, Faculty of Physics, Atomistilor, nr. 405, P.O. Box MG-11, Bucharest-Magurele, Romania
2) Romanian Materials Science - Crystal Growth Society, 077125 Bucharest, Romania
E-mail
florin_yo92@yahoo.com, berbecaru2ciceron@yahoo.com
Keywords:
perovskites, BaTiO3 ceramics, dielectric parameters, frequency and temperature
Abstract:
Barium titanate (BT) is one of the most important ferroelectrics with perovskitic structure. Ceramic BT samples around 1 mm thickness and 0.6 cm2 in the surface were prepared by solid state reaction and covered with silver electrodes for electric measurements. Electric parameters (permittivity and losses, electrical impedance and resistance) were investigated on large temperature (room temperature÷200 oC) and frequency (40 Hz÷5 MHz) ranges crossing up and down the Curie temperature (TC). A homemade thermostat system was used for a precise temperature control (minimum velocity around 0.1 oC/min). A Hioki 3532 RLC bridge was used for frequency control and measurements of electric parameters. A system computer with interfaces and specialized software were used for automated registering and subsequent investigations of the experimental data.
Permittivity increase with increasing the temperature having maxims at Tc and decreasing values above Tc. Also dielectric constant decrease with the frequencies increase with comparable dispersions in the ferroelectric and paraelectric phases. Losses with local maxims around Tc decrease their values with the frequencies increase but at higher temperatures and at low frequencies strongly increase their values. Electric impedance of the ceramics strongly decrease with increasing the temperatures having minims at Tc and increased values above Tc and show a significant decrease with frequencies increase. At some selected and fixed temperatures in a double log representation the impedance versus frequencies show a remarkable linearity.
Results were analyzed on the basis of an equivalent RC parallel circuit for the samples. The calculated resistance of samples shows a similar behavior with the impedance having higher values compared with both impedance and capacitive reactance of the ceramics. The experimental measurements also confirmed this behavior. It was concluded that on the investigated temperature and frequency ranges the electric parameters are strongly related to the electric capacity of the ceramics.
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