Field dependent energy density and induced relaxor ferroelectric to relaxor antiferroelectric property investigation in potassium modified NKBT-ST ceramics

Lead free 0.60 (Na0.5-xKxBi0.5TiO3) - 0.40 (SrTiO3) perovskite ferroelectric ceramics were synthesized effectively by a conventional solid-state reaction root. X - ray diffraction and Rietveld refinement revealed the co-existence of dual phase crystal symmetries for the ceramics around the morphotropic phase boundary in all samples. The coexistence of rhombohedral (R3c) and cubic (Pm3m) phases occurred up to the dopant concentration x = 0.07, succeeding a tetragonal (P4bm) with cubic (Pm3m) symmetries were observed for higher dopant concentrations x = 0.12 and 0.15 respectively. SEM micrographs indicate that the formation of well packed dense micro-structure with the nonuniform distribution. Temperature dependent dielectric measurement provoke the dielectric relaxation at low temperature near at depolarization temperature (Td). And then, the incorporation of ST in NKBT host matrix triggers the shifting of Curie temperature (Tm) towards the low temperatures. A stable relaxor ferroelectric like behavior up to the dopant concentration x = 0.07, and antiferroelectric like relaxor behavior was triggered progressively up to x = 0.15 was observed through in P-E loop studies. The electric field dependent recoverable energy storage performance at room temperature was calculated and a significant energy storage density (Wrec) and energy storage efficiency (eta) values noticed for x = 0.15 ceramic, which shows the x = 0.15 ceramic optimistic for energy storage applications in dielectric capacitors.