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2024-11-22 2:30

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Conference: Bucharest University Faculty of Physics 2015 Meeting

Section: Solid State Physics and Materials Science

Title:

Ceramic BaTiO3 doped with Ce³⁺ – dielectric properties

Authors:

Dorin RUSU 1), Danut BALAN 1), Ciceron BERBECARU 1)

Affiliation:

1) Electricity and Magnetism, Solid–State Physics, Biophysics Department,

Faculty of Physics, University of Bucharest, Bucharest – Magurele, 077125, Romania

E-mail

rusuadorin@gmail.com, danutz_nightshot@yahoo.com, berbecaru2ciceron@yahoo.com

Keywords:

ceramics, BaTiO3 doped with Ce, dielectric parameters, relaxor

Abstract:

Dielectric properties of pure Barium Titanate (BT) and 7.4 mol.% Ce3+ doped BaTiO3 (BT-7.4Ce3+) have been investigated on extended temperatures (–150 ÷ +150 oC) and frequency (42 ÷ 1106 Hz ) ranges, using a self-acting RLC bridge in line with a computer for collecting and further processing of experimental data with specialized programs. Pure BT ceramic, show three characteristic phase transitions in the investigated temperatures range, whereas BT–7.4Ce3+ ceramics displays decreased values of them. Permittivity values of the BT ceramics generally decreases in the BT–7.4Ce3+ doped materials, due to the heterovalent substitution of Ba2+ for Ce3+ ions which act as donors. Losses show comparable values for BT and BT–7.4Ce3+ ceramics, suggesting relative good charge compensation in doped ceramics. Above 100 oC and for low frequency values, some thermally activated mechanisms leads to the increase of losses value, most probably due to the electrons and vacancies which are always present in these materials obtained in the solid state sintering method. At low temperatures toward –100 oC some mobile charges increase the loss values in the BT–7.4Ce3+ ceramics. Permittivity of the BT–7.4Ce3+ ceramic shows decreasing values in the investigated frequency range with a low shift of the Curie temperature with increasing frequencies. For constant temperatures, permittivity and loss values present a more pronounced dispersion whether ceramics, are in the ferroelectric vs. paraelectric phase. The doped ceramics also displays increased and in the same time shifted maxima of losses toward high frequencies, up to Curie temperature with decreasing of their values above ferroelectric phase transition with the increasing frequency values. These features are characteristics of a relaxor-like behavior of the ceramics containing 7.4 mol.% Ce3+ in BaTiO3.