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/cm² 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.