Authors: J.F. Lomax, E.A. Lomax, S.C. Lu, J.P. Calame, J.J. Fontanella, C.A. Edmondson, M.C. Wintersgill
Affilation: U.S. Naval Academy, United States
Pages: 247 - 250
Keywords: dielectric, Ultem, barium titanate, nanoparticle
The need for improved energy storage devices prompts interest in developing new dielectric materials for high energy capacitors. This work reports data on the properties of cast films of BaTiO3 nanoparticles (high dielectric) in the polyetherimide, Ultem® 1000. Ultem has good mechanical properties and a high glass transition temperature, Tg (217º C), but a low dielectric constant of about 3.1 (room temperature and pressure and audio frequencies). A series of cast films was made with up to 69% by mass BaTiO3 (0.33 volume fraction). Electrical and thermal properties showed good dispersion of the BaTiO3. The real part of the dielectric constant is reported and compared with predictions from theories of mixtures of materials. In a recently published equation, the dielectric constant of a composite is related to the dielectric constants of the components and the volume fraction of the the components using an empirical constant mu. The data reported here fit well when mu = 3.48, in contrast to the original Hanai equation (mu = 3) which underestimates the composite dielectic constant values. The complex impedance measurements show a low temperature relaxation assigned to water-associated defects in the polymer. The breakdown field decreases as nanoparticle content increases.