Structure and dielectric properties of Dy-BST/PVDF nanocomposites

This paper uses Dysprosium doped Barium Strontium Titanate (Dy-BST) ceramic nanoparticles prepared via a solid-state process as dielectric fillers in polyvinylidene fluoride (PVDF) based nanocomposites. Dy-BST/PVDF nanocomposites were synthesized by casting method. A high-resolution transmission electron microscope validates that the size of Dy-BST nanoparticles is in the range of 10 to 30 nm with a polycrystalline structure. The impact of the Dy-BST nanoparticle contents (0–25 vol%) on the microstructure, dielectric, and breakdown strength properties of Dy-BST/PVDF nanocomposites were examined. The XRD of the Dy-BST/PVDF nanocomposite films confirms the cubic phase of the Dy-BST and both α-phase and β-phase of pure PVDF films. The measured permittivity showed a very clear dispersion step accompanied by dynamic peak relaxation at higher frequencies and/or lower temperature originating from the terminal γ-relaxation. As the temperature increases, real and imaginary parts of complex permittivity increase linearly with decreasing frequency, indicating the conductivity contribution. The breakdown (BD) voltage and permittivity were used in the COMSOL Multiphysics-based finite element method to get the breakdown field strength and calculate the corresponding energy density. The energy density showed a maximum value of about three times higher than that of pure PVDF. Therefore, the proposed nanocomposites with Dy-BST nanoparticles as fillers are promising for high energy density applications.