Influence of Bi nonstoichiometry on the energy storage properties of 0.93KNN–0.07BixMN relaxor ferroelectrics

Abstract

Ceramic-based dielectric capacitors are becoming more and more important in electronic devices. The ceramics of 0.93K0.5Na0.5NbO3–0.07Bix(Mg1∕3Nb2∕3)O3 (0.93KNN–0.07BixMN) (x=0.60, 2/3, 0.75 and 0.95) were successfully fabricated by virtue of the solid reaction process in this work. The results showed that the amount of Bi content has a significant impact on the ceramics of 0.93KNN–0.07BixMN. XRD indicates that all specimens exhibit a pure perovskite structure and existing oxygen vacancy in the specimens. The mean grain size for all specimens belong to submicron scale, and the sample of x=0.95 owns the smallest grain size is 0.11μm. The maximum dielectric constant increases but the phase transition temperature Tm exhibits a contrary tendency at 1MHz with increasing Bi concentration. Besides, all ceramics are relaxor ferroelectric. The impedance analysis further revealed that the activation energy of the ceramics increases with Bi content. Eventually, the highest η of 58.8% and Wrec of 1.30J/cm3 are simultaneously achieved in the sample with x=0.60. Overall, we demonstrate in this work that stoichiometry control of Bi in 0.93KNN–0.07BixMN ceramics is a practical method to obtain the desired structural, dielectric and energy storage properties.

Keywords

• Oxygen vacancy
• nonstoichiometry
• energy storage