The size-matching effect in 0.1Na1/3Ca1/3Bi1/3Cu3Ti4O12-xBa(Fe0.5Nb0.5)O3-(0.9-x)PVDF composites

High discharged energy density polymer composites are quite promising for capacitors and many other electronic devices. In this study, nano-sized Ba(Fe0.5Nb0.5)O3 (BFN) powders and micro-sized Na1/3Ca1/3Bi1/3Cu3Ti4O12 (NCBCTO) powders are embedded in 3-dimensionally connected poly(vinylidene fluoride) (PVDF) matrix, which has the potential to combine the high breakdown strength of the polymer with the high dielectric constant of the ceramics. The three-phase 0.1Na1/3Ca1/3Bi1/3Cu3Ti4O12-xBa(Fe0.5Nb0.5)O3-(0.9-x)PVDF composites were obtained by physical mixing, cold press technique and heat treatment. The dielectric permittivity of the composites is as high as 38.96 at 100 Hz when the value of x is 0.20. A large discharged energy density of 1.45 J cm−3 is achieved at a field of 600 kV/cm for the composites when the value of x is 0.05, which is attributed to the size-matching effect. The dense composites can be obtained when the hole defects between micro-sized NCBCTO powders and PVDF are filled with part of nano-sized BFN powders.