Effects of Na2O content on crystallization and dielectric properties of Na2O-PbO-Nb2O5-SiO2 glass-ceramic

Na2O-PbO-Nb2O5-SiO2 glass-ceramic were synthesized by melt-quench process. The crystallization processing of the dielectric phases were carried out at temperature range from 750 to 900 degrees C. The effects of Na2O content on crystallization and dielectric properties of Na2O-PbO-Nb2O5-SiO2 glass-ceramic were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and dielectric constant measurements. The results show that Pb2Nb2O7, NaNbO3 and PbNb2O6 are the crystallization phases which would be formed from the Na2O-PbO-Nb2O5-SiO2 glass at the temperature range from 750 to 900 degrees C. For a definite Na2O content, the dielectric constant increases with crystallization temperature. The initial crystallization temperature of NaNbO3 phase decreases with the increase of Na2O content, leading to the increase of dielectric constant of the glass-ceramic. Formation of PbNb2O6 phase at 850 and 900 degrees C would greatly increase the dielectric constant of Na2O-PbO-Nb2O5-SiO2 glass-ceramics, but the increase of Na2O content will inhibit the crystallization of PbNb2O6 phase.