Optimization of the dielectric properties and energy storage density in (K2O, SrO)–Nb2O5–B2O3–Al2O3–SiO2 glass–ceramics

A series of niobate glass–ceramics with different ratios of Sr/K have been synthesized by conventional controlled-crystallization method. The phase structure, microstructure, and dielectric properties of the (K2O, SrO)–Nb2O5–B2O3–Al2O3–SiO2 (KSN-BAS) glass–ceramics were investigated. The DSC analysis showed that the thermal stability of these as-annealed glasses was increased as the Sr concentration increased. The crystal phases of KSr2Nb5O15 and SrNb2O6 were obtained in the KSN-BAS samples. The microstructure could be modified with the replacement of K by Sr. The correlation between the breakdown strength and the activation energy was studied by the measurement of complex impedance spectra. The dielectric constants of all samples exhibited excellent stability from −80 to 120 °C and dielectric losses below 0.027. When the ratio of Sr/K was 1, a maximum dielectric constant was exhibited about 130.62. But the optimization of the breakdown strength of 1020.47 kV/cm was obtained about in the KS60 glass–ceramic. An optimal energy storage density could reach up to 5.67 J/cm3 in the KSN-BAS glass–ceramics. The charge–discharge efficiency of the KS50 glass–ceramic capacitor was tested by a special circuit and the efficiency could maintain about 83.6 % in a short time (20 ms).