Influence of thermal and thermoelectric treatments on structure and electric properties of B2O3–Li2O–Nb2O5 glasses

Abstract A transparent glass with the composition 60B 2 O 3 –30Li 2 O–10Nb 2 O 5 (mol%) was prepared by the melt quenching technique. The glass was heat-treated with and without the application of an external electric field. The as-prepared sample was heat-treated (HT) at 450, 500 and 550 °C and thermoelectric treated (TET) at 500 °C. The following electric fields were used: 50 kV/m and 100 kV/m. Differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, dc and ac conductivity, as a function of temperature, were used to investigate the glass and glass-ceramics properties. LiNbO 3 crystals were detected, by XRD, in the 500 °C HT, 550 °C HT and 500 °C TET samples. The presence of an external electric field, during the heat-treatment process, improves the formation of LiNbO 3 nanocrystals at lower temperatures. However, in the 550 °C HT and in the TET samples, Li 2 B 4 O 7 was also detected. The value of the σ dc decreases with the rise of the applied field, during the heat-treatment. This behavior can indicate an increase in the fraction of the LiNbO 3 crystallites present in these glass samples. The dc and ac conduction processes show dependence on the number of the ions inserted in the glass as network modifiers.The Raman analysis suggests that the niobium ions are, probably, inserted in the glass matrix as network formers.These results reflect the decisive effect of temperature and electric field applied during the thermoelectric treatment in the structure and electric properties of glass-ceramics.