HP007 modeling permittivity and conductivity contrast on electric energy storage properties of dielectric composites

The electric field distribution, field and power density enhancement factors, power loss and stored electric energy in dielectric composites were calculated using the boundary-element method (BEM). The composites consist of a low permittivity host containing either spherical conducting inclusions having dielectric coating shells, or dielectrically or conductively graded spherical dielectric particles. It is shown that the local electric field and power density enhancement effects diminish as the thickness of shells, the number of grading layers or the degree of nonlinearity of grading increases. The reduced enhancement effects significantly increase the normalized stored electric energy due to the fact that with a reduced enhancement factor a higher voltage can be applied. Frequency effects for composites with conductivity-graded particles were also considered. The results of these studies have implications for the design of high energy density dielectric composites.