Crystallization Mechanisms and Energy-Storage Performances in BaO-SrO-Na2O-Nb2O5 Based Glass-Ceramics

摘要

The [x BaO, (1-x) SrO]-Na2O (x=0.0, 0.2, 0.5, 0.8) niobate-based glass-ceramics were prepared through the controlled crystallization method. Crystallization mechanism, phase structure, dielectric properties, and energy-storage properties were studied by adjusting Ba/Sr ratio. It was found that the surface and internal crystallization occurred simultaneously at first crystallization peak, while surface crystallization occurred at second crystallization peak. With Ba/Sr ratio increasing, dielectric constant increased firstly and then decreased, while dielectric loss firstly decreased and then increased. When x=0.2, optimal dielectric constant of 88 and dielectric loss of 0.0055 were obtained, which is related to the solid solution phase Sr0.5Ba0.5Nb2O6. Breakdown strength (BDS) showed a behavior of increase before decrease. The highest BDS reaches 1975kV/cm for x=0.2, which is attributed to uniform and dense microstructure. Correspondingly, the theoretical energy-storage density was increased up to 15.4J/cm(3). Also, discharged efficiency reaches a high value of 91%. Discharged power density of 0.65MV/cm(3) was obtained for x=0.2 in the RLC pulsed circuit.