Abstract
The aim of this research is the study of the structural, morphological
and electrical properties of a 44SiO2-33Li2O-23Nb2O5 (mol%) glass and
glass-ceramics. XRD, SEM, Raman and dielectric spectroscopy and
(Thermally stimulated DC) TSDC measurements were used to characterize
the samples. The LiNbO3 crystalline phase was detected, by XRD and Raman
spectroscopy, in the samples treated above 873 K. The volume ratio of
the particles increases with increase in heat-treatment temperature. The
behavior of the sigma(dc) and sigma(ac), with the increase of the
heat-treatment (HT) temperature, was related with the decrease of the
free ions number in the glass matrix and consequent increase of the
volume ratio between the LiNbO3 crystalline phase and the glass matrix.
The epsilon' value decreases with the increase of the HT temperature.
The complex impedance spectra were fitted to a equivalent electric
circuit. The Z `' vs. Z' plots of the samples HT below 873 K, indicate
the existence of a distribution of relaxation times. The TSDC
measurements revealed the presence of three depolarization peaks in the
as-prepared and 550HT treated sample. The sample HT575 presents two TSDC
peaks, and the samples HT600 and HT650 one TSDC peak. These peaks were
correlated with the structure and mobility of ions in the prepared glass
and glass-ceramics. The behavior of the dc and ac conductivities, TSDC
peaks and dielectrical characteristics reflect the important role
carried out by the treatment temperature in the formation of a glass
ceramic structure. (c) 2007 Elsevier B.V. All rights reserved.
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