Excellent energy density and power density achieved in K0.5Na0.5NbO3-based ceramics with high optical transparency

Abstract (K0.5Na0.5)NbO3 (KNN)-based ceramics have been widely investigated and regarded as promising lead-free materials because of their good energy storage properties, transparency and nontoxicity. Herein, a strategy of composition driving to increase densification and decrease the average grain size of KNN ceramics was proposed to optimize both transparency and breakdown strength. The results show that the introduction of KBN dramatically reduced the average grain size to 100 nm and enhanced the breakdown strength to 330 kV∙cm−1, and the representative 0.85KNN-0.15KBN ceramic exhibits a high energy density of 6.56 J∙cm−3, an excellent recoverable energy density of 3.39 J∙cm−3, an ultrahigh power density of 47.69 MW∙cm−3 and a maximum transparency of ∼83.3% at the wavelength of 1600 nm. Additionally, it is found that the 0.85KNN-0.15KBN ceramic shows an excellent temperature stability of energy storage properties in the temperature range of 20–120 °C. These results reveal the novel 0.85KNN-0.15KBN ceramic can be used as potential dielectric materials for transparent electronic devices.