Hydrothermal processing and dielectric property measurement of barium titanate /polymer thin films

David Edward Collins, Purdue University

Abstract

Hydrothermal processing was used as a low temperature route to fabricate thin film composites (<1 >μm thick) of BaTiO3 and styrene-based polymers. Films were formed by the in-situ precipitation of BaTiO3 within the polymer matrix below 90°C. In composites of BaTiO3 and a polybutadiene/polystyrene triblock copolymer, films were composed of a continuous layer of BaTiO3 particles (60 to 180 nm) on the surface and an interior composite structure of smaller BaTiO3 particles (5 to 20 nm) in segregated regions distributed throughout the matrix. After the initial nucleation of 20 nm particles on the film surface, growth occurred by heterogeneous nucleation of 5 nm particles on existing BaTiO3. Despite the observance of distinct substructure, each overall particle exhibited a single crystal morphology as determined by electron diffraction and lattice continuity. Although the film surface morphology was greatly influenced by changes in the reaction environment, the internal morphology was consistent regardless of the reaction conditions. These films are contrasted with composites of BaTiO3 and a polystyrene/poly(maleic anhydride) block copolymer in which a similar microstructure to that of the BaTiO3-SBS system was found, except that the particulate phase was homogeneously dispersed throughout the matrix. The dielectric properties were found to be primarily dependent on the internal film morphology such that an increase in the particulate dispersion without increasing the dielectric constant of the matrix doubled the dielectric constant of the composite material. The formation mechanisms and dielectric property measurements of these films are discussed.

Degree

Ph.D.

Advisors

Slamovich, Purdue University.

Subject Area

Materials science

COinS