Structural, elelectrical and energy storage properties of BaO-Na2O-Nb2O5-WO3-P2O5 glass-ceramics system
Résumé
Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na(2)O-2.5[(1 - x)Nb2O5-xWO(3)]-1P(2)O(5) (x = 0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 degrees C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), x-ray powder diffraction (XRD), Raman, impedance spectroscopy, and the P-E hysteresis loops. All of these techniques allowed the identification of Ba2Na4W2Nb8O30 phase with tungsten bronze structure embedded in the glassy matrix. The density of glass-ceramics was found to increase with increasing tungsten content to reach a maximum at x. =. 0.3 and then decreases. Dielectric and conductivity parameters were found to be governed by the presence of oxygen vacancies. Room temperature energy storage property which depends on the composition X, was performed using P-E hysteresis loops of the glass-ceramics. The optimum discharge density was obtained for B3 with an energy efficiency of 73.77%.