Glass-ceramic nanocomposites in the [(1 − x)PbO–xBaO]–Na2O–Nb2O5–SiO2 system: Crystallization and dielectric performance

Abstract

The crystallization process, microstructure and dielectric properties of [(1 − x)PbO–xBaO]–Na2O–Nb2O5–SiO2 (PBNNS) (0 ≤ x ≤ 1) glass-ceramics prepared by controlled crystallization were investigated. The crystallization strategies for acquiring nano-crystallized PBNNS glass-ceramics were monitored by differential thermal analysis (DTA). X-ray diffraction (XRD) analysis revealed a major crystal phase transition in PBNNS glass matrix as the crystallization temperature increased. At low temperatures (700–750 °C), the major crystal phases precipitating in the glass matrix are identified as Pb2Nb2O7 for x = 0, Ba2NaNb5O15 for x = 1 and their solid solution for 0.2 ≤ x ≤ 0.8; while at higher temperatures (≥850 °C), heat treatment produces different crystalline phases, PbNb2O6 and NaNbO3 for x = 0, Ba2NaNb5O15 and NaNbO3 for x = 1, and the solid solution of these three phases for 0.2 ≤ x ≤ 0.8. Corresponding to the result of phase transition, microstructural observation proves increasing crystallite sizes with increasing temperature of heat treatment. At different crystallization temperatures, the dielectric properties of the [(1 − x)PbO–xBaO]–Na2O–Nb2O5–SiO2 glass-ceramics show a strong dependence on the chemical composition x. At low temperatures (700–750 °C), a maximum of the dielectric constant of the PBNNS glass-ceramic is found for the composition x = 0.6; while at higher crystallization temperatures (≥850 °C), the dielectric constants of all samples (0 ≤ x ≤ 1) exhibit decreasing values with increasing x.