Microstructures and dielectric properties of Sr0.6Ba0.4Nb2O6 ceramics with BaCu (B2O5) addition for energy storage

The Sr0.6Ba0.4Nb2O6 ceramics with BaCu(B2O5) (abbreviated as BCB) additive have been prepared via the solid state reaction route. The effects of BCB content on the sintering behavior, crystal structure, microstructure, dielectric property and energy storage property of Sr0.6Ba0.4Nb2O6 ceramics have also been investigated. XRD results show that Sr0.6Ba0.4Nb2O6 ceramics adopt the tetragonal tungsten bronze structure and the secondary phase SrB2O4 emerges when BCB content exceeds 4 wt%. SEM results reveal that the addition of BCB lowers the sintering temperature and improves the densification and microstructure of the Sr0.6Ba0.4Nb2O6 ceramics. An analysis of the dielectric and ferroelectric properties indicates that the values of dielectric constant and saturation polarization decrease with the increase of BCB additive. The breakdown strength (BDS) is notably improved due to the reduction of the grain size and dense uniform microstructure. And the highest BDS of 187 kV/cm can be achieved for the sample with 4 wt% BCB. Complex impedance spectra exhibit that the BDS is closely related to the activation energy of interface polarization. The sample with 4 wt% BCB addition possesses the maximum energy-storage density of 1.63 J/cm3, which is 1.9 times higher than that of pure Sr0.6Ba0.4Nb2O6 ceramics. This study provided the BCB added ceramic as an attractive candidate for making high-energy density capacitors.