Electrical properties of lithium niobium silicate glasses


Lithium niobate (LiNbO3) is a ferroelectric material in the crystalline form and considerable interest has recently been shown in the study of its properties in a glass structure. A 34SiO(2)-33Li(2)O-33Nb(2)O(5) (mol%) glass was prepared using the conventional melt-quenching method. LiNbO3 crystals were precipitated in the glass matrix by a heat-treatment (HT) process. These glasses were studied by differential thermal analysis, X-ray power diffraction (XRD), scanning electron microscopy, dc electrical conductivity (sigma(dc)), ac conductivity (sigma(ac)) and dielectric measurements. LiNbO3 crystal phase was detected by XRD on the sample HT at 600 degreesC. The dc and ac conductivity, at 300 K, decreases with the increasing of the HT temperature. The dielectric study in function of frequency, at constant temperature, was made using the modulus (M*) model and a distribution of relaxation times was observed. The dielectric data was fitted with the complex non-linear least squares procedure, revealing that a resistor in parallel with a constant phase element is the best equivalent circuit. The dielectric constant value, measured at 1 kHz and room temperature, decreases from 102 to 62 with the increasing of the HT temperature, suggesting a random orientation of the dipolar moments associated with the LiNbO3 nanocrystals. (C) 2003 Elsevier B.V. All rights reserved.



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Materials Science


Graca, MPF; Valente, MA; da Silva, MGF

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