The Research On Dielectric Tunability Of Antiferroelectric Ceramic/polystyrene Composites

Ceramic/polymer composites with high dielectric constant, low dielectric loss and good flexibility are made from ceramics and polymers, which are the hotspot in the research of composite materials. In the research of ceramic/polymer composites, most of them were about piezoelectric, pyroelectric, and magnetoelectricity properties of ferroelectric ceramic/polymer composites. Ferroelectric ceramics’ loss and permittivity are too high to conform to the theoretical model. And the permittivity change with the external incentive smally, which limit the application in the electric field modulation devices. Antiferroelectric ceramics can produce the antiferroelectric- ferroelectric phase transition, and mutation of size and dielectric properties if induced by electric field electric field, temperature and pressure.Few researchers have focused on electric field affect dielectric properties of antiferroelectric ceramic/polymer composites. In this article we study antiferroelectric ceramic/polymer composite materials from the content of ceramics, the modification of organic – inorganic interface, and the addition of conductive phase, which can lay foundation for antiferroelectric ceramic/polymer composites used in the electric field modulation devices.In the choice of the content of the ferroelectric ceramics, we chose the Lead barium lanthanum zirconium tin titanate(PBLZST) and Polystyrene(PS) as the raw material, and studied the influence on microscopic structure and dielectric properties by the content of PBLZST in PBLZST/ PS composite. The dielectric constant, loss, and tunability rate are increased with the increase of ceramic content.When content of PBLZST is at 20 vol%, the dielectric constant(ε), the loss(tanδ) and the tunability rate are minimum, respectively are 10, 0.009, 0.1%. And the interface between the two phase is not very distinct. When content of PBLZST is at 80 vol%, the dielectric constant(ε), the loss(tanδ) and the tunability rate are maximum, respectively are 51, 0.055, 4%. And there were a lot of gaps and defects in materials.In the problem of poor interface compatibility for ceramic and polymer in composite material, we studied the influence on composite interface and dielectric properties by adding different content of silane coupling agent KH550 acted as modifier. Compared with not adding KH550 in composite, the dielectric constant and tunability rate of the composite modified with KH550 were increased, the dielectric loss was reduced.When content of KH550 is at 10 wt %, the dielectric constant(ε)is 87, the loss(tanδ)is 0.007, and the tunability rate is 7%. The appropriate amount of silane coupling agent can improve the interface effect of organic and inorganic phase in composite material, so as to improve the dielectric constant and reduce the dielectric loss. In addition, KH550 can form single molecule insulation layer on the surface of polymer, so as to increase the electric field of ceramic phase and improve tunability rate of the PBLZST/PS composite.Finally, in the problem of low tunability rate of the PBLZST/PS composite, we studied the influence on dielectric properties by adding nano carbon powder, carbon nanotubes, graphene these three kinds of conductor. When the content of C is at 1 wt % and the applied electric field is 100 V/mm, the maximum tunability rate is 48%. When the content of CNT is at 0.4 wt % and the applied electric field for 100 V/mm, the maximum tunability rate is 40%. When the content of GNS is 0.6 wt % and the applied electric field for 100 V/mm, the maximum tunability rate is 25%. The appropriate amount of conductive phase in PBLZST/PS composite material on the one hand can improve the electrical conductivity of polymer and increase the rate of the distribution of electric field on the ceramic particles, on the other hand can form small amount of conductive path between PBLZST particles in composite and increase the rate of the distribution of ceramic particles.