Electrical properties of BaTiO _3 nanoparticles in poly(ether imide)

摘要

The relative permittivity has been measured at audio frequencies and low temperatures for nanocomposites composed of poly(ether imide) (PEI) and BaTiO _3 nanoparticles, the nanoparticles in a cavity and polycrystalline BaTiO _3. The data at room temperature, for the real part of the relative permittivity versus nanoparticle content of the heat-treated nanocomposites, are found to follow a recently proposed modified Hanai equation. Also, a low-temperature relaxation region (in the vicinity of 20K) is found in the heat-treated nanocomposites. This relaxation region is also observed in measurements on the nanoparticles packed in a cavity and for the polycrystalline BaTiO _3 materials. A relaxation associated with water in the PEI is observed in the as-prepared nanocomposites. Finally, the breakdown strength of the heat-treated nanocomposites is found to decrease as the nanoparticle content increases. Microstructure-level simulations of electric field statistics were carried out and show that matrix field intensification cannot account for all of the variation of breakdown strength with nanoparticle concentration.