Effect of employing Ni and Ag nano-particles as third phase on dielectric breakdown strength of BaTiO₃/PVDF composites

The Ni-BaTiO₃/polyvinylidene fluoride (Ni-BaTiO₃/PVDF) and Ag-BaTiO₃/PVDF three-component composites were prepared to improve the breakdown strength of the composites, in which Ni and Ag metal nano-particles were used as the third phase. The effects of addition, particle size and type of metals on the breakdown strengths of the composites were studied. The experimental results show that all breakdown strengths of Ni-BaTiO₃/PVDF and Ag-BaTiO₃/PVDF three-component composites increase firstly and then decline with the increase of Ni or Ag addition. And all composites give comparative dielectric constants than those without metals addition and each has maximum breakdown strength over the range of metal addition. For same type metal of Ni, addition with smaller size of Ni is better for enhancing the breakdown strength of the composites. Moreover with the same particle size and addition, Ni-BaTiO₃/PVDF composites show better breakdown performance. The breakdown strength of Ni(50 nm)-BaTiO₃/PVDF nanocomposite with 1.90% volume fraction of Ni reaches up to 200 kV/mm and its energy density is about five times of BaTiO₃/PVDF composite. The Coulomb blockade effect is employed to explain the dielectric breakdown strengths under high electric field of such kind of composties.