Optimizing energy storage performance under moderate electric field in La2O3@NBST relaxor ferroelectric ceramics via a chemical coating

Dielectric capacitors are highly valued in power electronics for their high power density and stability. However, achieving high energy density in small devices under moderate electric fields remains challenging. In this study, La 2 O 3 -coated (Na 0.5 Bi 0.5 ) 0.4 Sr 0.6 TiO 3 ceramics (La 2 O 3 @NBST) were successfully synthesized via chemical coating method. In addition, the influence of La 2 O 3 content on the microstructure, dielectric and energy storage properties of the ceramics were systematically studied. Due to the effectively refinement of grain size and promotion of uniform, dense microstructure formation by La 2 O 3 coating, both the resistivity and breakdown strength of ceramics have been significantly enhanced. Moreover, the remarkable reduction in the remnant polarization ( P r ) stems from strengthened relaxor behavior, which is a consequence of La 2 O 3 -induced phase transition from the rhombohedral ( R 3 c ) to the tetragonal ( P 4 bm ) phase. Notably, a discharge energy density of 2.01 J/cm 3 and an energy efficiency of 78% could be achieved in the 4 wt% La 2 O 3 @NBST ceramic, along with good cycling stability after 10 5 cycles and temperature stability from 30 °C to 120 °C. This work establishes a theoretical basis for the chemical coating method in optimizing lead-free energy storage ceramics, showcasing its application potential in high-performance dielectric capacitors.