Structural, dielectric and energy storage properties of BaO–Na2O–Nb2O5–P2O5 glass-ceramics

A series of (1−x)[(2BaO–0·5Na2O)–1P2O5] –xNb2O5 (BNPN, x=0·41, 0·43, 0·45, 0·48) glass-ceramics based on phosphate glasses have been prepared via a controlled-crystallisation route. The structure, dielectric properties, interfacial polarisation and energy storage properties were systematically investigated. The x-ray diffraction results showed the simultaneous presence of Ba2NaNb5O15 tungsten bronze structure (TTB) and the NaNbO3 perovskite. A stable dielectric constant over a temperature range from 25–200°C, low dielectric losses less than 0·03 and excellent frequency stability at room temperature were obtained. The decrease of niobium content promoted the TTB crystallisation with improvement of the high dielectric properties of the system. The optimum of the dielectric constant and recoverable energy storage density were obtained for BNP41 crystallised at 1000°C. Analyses of the complex impedance indicated that the niobium content and crystallisation temperature affect the interfacial polarisation.