High conductivity, percolation behavior and dielectric relaxation of hybrid ZIF-8/CNT composites

The electrical behavior of hybrid ZIF-8/conducting composites remains poorly understood. Here, the hybrid ZIF-8/CNT composites are synthesized by an in situ growth of ZIF-8 on carbon nanotubes (CNT). The crystal structure, morphology and dielectric properties of the composites were investigated. Dielectric permittivity of as-prepared composites is improved more than 10 times by introduced CNT. The composites have a low percolation threshold (3.2%), where the dc conductivity increases by 4-5 orders of magnitude near the percolation threshold. Furthermore, we find three dielectric relaxation processes in the as-prepared ZIF-8 and ZIF-8/1%CHT composite by electrical modulus. One low-frequency dielectric relaxation associates with Maxwell-Wagner effect between composites and electrodes, while the two high-frequency dielectric relaxation attributes to the short-range hopping process of carries or dipoles orientation. The work provides deep insights on the intrinsic and extrinsic dielectric responses of ZIF-8 based composites and on the percolation behavior of hybrid ZIF-8/conducting materials composites. (C) 2020 Elsevier B.V. All rights reserved.