Fabrication and Characterization of Fully Inkjet Printed Capacitors Based on Ceramic/Polymer Composite Dielectrics on Flexible Substrates

The preparation of fully inkjet printed capacitors containing ceramic/polymer composites as the dielectric material is presented. Therefore, ceramic/polymer composite inks were developed, which allow a fast one-step fabrication of the composite thick films. Ba0.6Sr0.4TiO3 (BST) is used as the ceramic component and poly(methyl methacrylate) (PMMA) as the polymer. The use of such composites allows printing on flexible substrates. Furthermore, it results in improved values for the permittivity compared to pure polymers. Three composite inks with varying ratio of BST to PMMA were used for the fabrication of composite thick films consisting of 33, 50 and 66 vol% BST, respectively. All inks lead to homogeneous structures with precise transitions between the different layers in the capacitors. Besides the microstructures of the printed thick films, the dielectric properties were characterized by impedance spectroscopy over a frequency range of 100 Hz to 200 kHz. In addition, the influence of a larger ceramic particle size was investigated, to raise permittivity. The printed capacitors exhibited dielectric constants of 20 up to 55 at 1 kHz. Finally, the experimental results were compared to different theoretical models and their suitability for the prediction of εcomposite was assessed.