The dielectric behavior of a thermoelectric treated B 2O 3–Li 2O–Nb 2O 5 glass

Abstract

A transparent glass with the composition 60B 2O 3–30Li 2O–10Nb 2O 5 (mol%) was prepared by the melt-quenching technique. Glass–ceramics, containing LiNbO 3 ferroelectric crystallites, were obtained by heat-treatment (HT) above 500 °C, with and without the presence of an external electric field. The dielectric properties of the glass and glass–ceramic were investigated, as a function of temperature (270–315 K), in the 10 mHz–32 MHz frequency range. The presence of an external electric field, during the heating process, improves the formation of LiNbO 3 crystallites. The rise of the treatment temperature and the applied field, during the heat-treatment, leads to a decrease in the dc electric conductivity ( σ dc), indicating a decrease of the charge carriers number. The dielectric permittivity ( ε′) values (300 K;1 kHz) are between 16.25 and 18.83, with the exception of the 550 °C HT sample that presents a ε′ value of 11.25. An electric equivalent circuit composed by an R in parallel with a CPE element was used to adjust the dielectric data. The results reflect the important role carried out by the heat-treatment and the electric field during the HT in the electric properties of glass–ceramics.