High dielectric constant of barium strontium titanate/polyimide composite

Abstract

This research aim is to investigate the dielectric constant of barium strontium titanate(BaSrTiO3)/polyimide composite. The BaSrTiO3 particles were prepared from barium hydroxide octahydrate, strontium nitrate and titanium (IV) isopropoxide by sol-gel method. The polyimide was prepared by two-step polymerization method, with PMDA and 4’4-ODA as primary materials. The effects of content and size of filler on thermal and electrical properties of BaSrTiO3/ polyimide composite including dielectric constant, dielectric loss and thermal stability were investigated. The dielectric constant and dielectric loss of composites exhibited higher values with increasing the BaSrTiO3 particles loading and decreased with the frequency of generator increased. The effect of surface modification by three types of silane coupling agents on the dielectric properties of BaSrTiO3/ polyimide composite was compared with unmodified composite. The result indicated that the silane coupling agents treated ceramic filler/polyimide composite exhibited lower the dielectric constant and dielectric loss than the unmodified surface composite. The effect of hybrid size of different particles type between BaSrTiO3 and SrTiO3 were evidenced that the suitable weight ratio between BaSrTiO3 and SrTiO3 about 9:1 to give the maximum dielectric constant and dielectric loss of composite.