Crystallization kinetics, breakdown strength, and energy-storage properties in niobate-based glass-ceramics

In this work, (100-x)(0.12 SrO-0.3 Na2O-0.1 Nb2O5)-xSiO2 (x = 30, 35, 40, 45, 50 mol%) glass-ceramics were prepared by using the meth-quenching-controlled crystallization method. Phase evolution, Crystallization mechanism, dielectric properties, dielectric breakdown strength (DBS), and energy-storage performances were comprehensively studied by varying SiO2 content. DSC studies revealed simultaneous occurrence of surface and internal crystallization mechanism in the glass-ceramics. XRD results showed three tungsten bronze structure SrNb2O6, Sr6Nb10O30, NaSr2Nb5O15 phases and perovskite structure NaNbO3 phase, which was quantified by the Reietveld refinement. It was found that dielectric constant and theoretical energy-storage density increased firstly and then decreased with the increase of the SiO2 contents. For x = 35 mol%, the theoretical energy-storage density reaches the maximal value of 15.3 J/cm3 due to the highest dielectric constant of 124 and DBS of 1669 kV/cm. And the highest DBS is related to the uniform and dense microstructure for x = 35 mol%. For practical applications in pulsed RLC circuit, the discharged efficiency increases from 74.2% to 91.5% with the increase of the SiO2 contents.