A strategy for high performance of energy storage and transparency in KNN-based ferroelectric ceramics.

• The doping of SSN increased the band gap width and decreased the grain size. • The ceramic possesses an energy density of 4.42 J/cm3 and an efficiency of 60%. • The transmittance of the ceramic is 76.7% and 84.5% at 780 and 1378 nm, respectively. • 0.825KNN-0.175SSN ceramic exhibited a small strain effect of 0.022%. Lead-free transparent ferroelectric ceramics with superior energy storage properties are highly desirable for pulsed power technologies and the increased optical transparency demand. However, the transparency and energy storage density of lead-free bulk ceramics cannot meet the requirements of their wide applications due to the coarse microstructure and relatively low breakdown strength. In this study, a design strategy is proposed to optimize the energy storage characteristics and transparency of ceramics by introducing nanodomains, increasing the band gap energy and reducing the grain size. The results showed that submicron grain (0.21 μm) and large band gap energy (E g = 3.21 eV) were achieved through the introduction of the second component Sr(Sc 0.5 Nb 0.5)O 3 (SSN). An excellent transparency of up to 84.5% in the near-infrared region (1378 nm), a high energy density (W) of ~4.42 J·cm−3 and an extremely small strain of ~0.022% were simultaneously achieved in the 0.825(K 0.5 Na 0.5)NbO 3 -0.175Sr(Sc 0.5 Nb 0.5)O 3 (0.825KNN-0.175SSN) ceramics. These results revealed the potential applications of (K 0.5 Na 0.5)NbO 3 -based ceramics for energy storage and provide a feasible approach of domain engineering to develop new lead-free energy storage transparency materials. [ABSTRACT FROM AUTHOR]