High dielectric constant composites controlled by a strontium titanate barrier layer on carbon nanotubes towards embedded passive devices

To solve the conundrum of percolative dielectric composites, namely, large dielectric loss caused by direct contact between conductive fillers near the percolation threshold, researchers introduced a general method of coating an insulative shell on the conductive fillers. In this work, a core–shell-structured hybrid is synthesized by coating strontium titanate (STO) shell onto the multiwalled carbon nanotubes (MWCNTs) via sol–gel processing and compounded with epoxy resin as conductive filler to prepared the high dielectric constant percolative polymer composites. The STO shell outside the MWCNTs constrained the electrical conductivity of MWCNTs as an insulating layer and increased the dielectric constant of composites as a high dielectric constant ceramic. According to the dual function of STO shell, the composites of STO-coated MWCNTs and epoxy resin show an effectively improved dielectric constant and significantly reduced the dielectric loss. In the case of low filler loading amount at 11 wt%, the dielectric constant of the composite can reach 283 at 1000 Hz, and the dielectric loss is only 0.07.