Ferroelectric nanocomposite based dielectric inks for reconfigurable RF and microwave applications
A novel ferroelectric ink comprising multiphase Barium Strontium Titanate (BST) in a polymer composite is described. The ink can be employed using direct-ink writing techniques to print high dielectric constant, low loss, and electrostatically-tunable dielectrics on substrates. The substrates can be flexible such as plastics or rigid, such as substrates comprising semiconductor materials or ceramics and the like. The dielectric ink is made by suspending pre-sintered nano/submicron-sized particles of BST in a thermoplastic polymer with a solvent. After printing with the ink, a low temperature curing process is performed at temperatures below 200° C., a temperature too low to sinter BST. Fully printed devices, such as a varactor and a phase shifter using direct ink writing methodologies are described.
1. A liquid ink, comprising:
a plurality of pre-sintered perovskite oxide particles, said plurality of pre-sintered perovskite oxide particles having a size distribution with a modal size in the range of 30 nm to 2000 nm;
a thermoplastic polymer configured to have a low loss tangent less than 0.001 at high frequencies;
a solvent configured to dissolve said polymer; and
a dispersant configured to disperse said plurality of pre-sintered perovskite oxide particles.
2. The liquid ink of claim 1 , wherein said pre-sintered perovskite oxide particles comprise Ba x Sr (1−x ) TiO 3 , with x in the range of 0.0≦x≦1.0.
3. The liquid ink of claim 2 , wherein said pre-sintered perovskite oxide particles comprise Ba x Sr (1−x ) TiO 3 , with x in the range of 0.5≦x≦0.7.
4. The liquid ink of claim 1 , wherein said polymer is a polymer selected from the group of polymers consisting of Topas Cyclic Olefin Copolymer, PTFE (Teflon), silicone rubber, butyl-rubber, epoxy resin, polymethylmethacrylate (PMMA), polyphenylene sulfide (PPS), Polystyrene (PS), Polyethylene (PE), Parylene C & N, and olypropylene-graft-poly(styrene-stat-divinylbenzene) (ER).
5. The liquid ink of claim 1 , wherein said solvent is a solvent selected from the group of solvents consisting of xylene, toluene, and Tetrahydrofuran(THF).
6. The liquid ink of claim 1 , wherein said dispersant is 4-tert-butycatechol.