Effect of NaNbO3 Crystalline Aggregates on the Electrical Properties of SiO2-Na2O-Nb2O5 Glass-Ceramics
The presence of NaNbO3 crystallites in a glass matrix has scientific and technological interest due to their electrical properties and potential applications in microwave, pyroelectric and piezoelectric devices. A glass with the composition 60SiO2-30Na2O-10Nb2O5 (% mole) was prepared by the melt-quenching method. NaNbO3 microcrystallites were precipitated on the surface of the glass by heat-treatment. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, dc and ac conductivity measurements were used in the study of the glass and glassceramic materials. The number of particles, precipitated in the surface of the glass-ceramic samples, increases from the 650 to the 750°C and decrease in the 800°C sample. In all these samples the particles size thickness increases with the rise of the heat-treatment temperature. In the 750 and 800°C samples it was observed the presence of a white surface layer formed by NaNbO3 crystallites aggregations. The dc conductivity (σdc) decreases with the rise of the heat –treatment temperature up to 750°C and the dielectric constant value, at 1kHz and room temperature, has a maximum value of 34.94 for the 800 °C treated sample.
Paula Maria Vilarinho
M. P.F. Graça, M. G. Ferreira da Silva, M. A. Valente, "Effect of NaNbO3 Crystalline Aggregates on the Electrical Properties of SiO2-Na2O-Nb2O5 Glass-Ceramics", Materials Science Forum, Vols. 514-516, pp. 274-279, 2006