Effect of K2O addition on glass structure, complex impedance and energy storage density of NaNbO3 based glass-ceramics

Abstract

(40-x)Na2O-xK2O-40Nb2O5-20SiO2 (x = 0, 5, 10, 15 mol%) glass-ceramics are synthesized by traditional melts method. The glass-ceramics are tested by X-ray diffraction (XRD) techniques, and NaNbO3 as major phase led a high permittivity. A microstructure with nanoscale grains enclosed by glass phase is observed by scanning electron microscope (SEM). With the increase of content of K2O, a relaxed glass network structure is obtained, and more kinds of phase are formed. Permittivity comes to 174 approximately when x = 5 mol%. In addition, the activation energy (Ea) of residual glass phase for Na2O-K2O-Nb2O5-SiO2 glass-ceramics firstly increase then decrease. Breakdown strength (BDS) of all samples increase and then decrease with the increase of content of K2O, and maximum BDS is obtained when x = 10 mol%. And maximum theoretical energy density is 1.43J/cm3 when x = 5 mol%.