Improved dielectric strength and loss tangent by interface modification in PI@BCZT/PVDF nano-composite films with high permittivity

The Ba 0.859 Ca 0.141 Zr 0.106 Ti 0.894 (BCZT) nano-particles were modified by polyimide (PI) through a chemical coating method. And the PI@BCZT/polyvinylidene fluoride (PVDF) flexible composite films were fabricated by solution casting method. The transmission electron microscopy and scanning electron microscopy results show that the nano-particles is about 50 nm, PI is uniformly coated on the surface of BCZT nano-particles about 7–10 nm as well as there are uniform and improved dispersion in the matrix after modification. A series of dielectric properties were carried out. The results show the 50 vol% composites own a remarkably enhanced dielectric permittivity (ε r  = 130) at 100 Hz. After modification, the breakdown strength has increased from 20 to 96 kV mm −1 and the loss tangent is reduced from 1.8 to 0.2 at 100 Hz compare with un-modified composites in 40 vol% dopant. With the increase of dopant, ferroelectricity of composites can be enhanced. The optimal residual polarization is 40 vol% PI@BCZT composites, which possess 1.025 μC/cm 2 under 50 kV/mm external electric field. In addition, after modification, thermo-gravimetric analysis exhibits the degradation temperature Td 5% and Td 10% of PI@BCZT/PVDF composites can be enhanced about 5–10 °C and show better thermal stability than un-modified composites.