Crystallization Behavior and Dielectric Properties of Ferroelectric Glass-ceramics Containing BNN and NN Crystals

Glass samples with compositions of 16Na2O-8BaO-26Nb2O5-50SiO2 (mol%) were prepared using the melt-quenching method and then heat-treated under different temperatures and times. The resulting crystallization behavior was then studied through X-ray diffraction and scanning electron microscopy, and the dielectric properties were measured using an impedance analyzer in the frequency range 10 Hz–10 MHz. The experimental results showed that all of the obtained glass-ceramic samples heat treated using different temperatures and times contained mixed-crystalline phases between Ba2NaNb5O15 (BNN) with tungsten-bronze structure and NaNbO3 (NN) with a perovskite structure. The crystals of these two phases were distributed randomly throughout the bulk glass-ceramics at the nano-scale. The plots of the dielectric constant versus the measurement temperature reveal a serial phase transition with a complex mechanism of the dielectric relaxation. The serial phase transition is related to the dielectric response of both the...