GB1154190A - Improvements in Cryogenic Capacitors - Google Patents

Abstract

1,154,190. Capacitors. GENERAL ELECTRIC CO. 16 Aug., 1967 [1 Sept., 1966], No. 37803/67. Heading H1M. A capacitor having a high dielectric constant and low loss at cryogenic temperatures comprises a dielectric film consisting of a powdered ferroelectric ceramic and a water-soluble binder adhering to one electrode, a second electrode in contact with the dielectric film and leads connected to each electrode, the capacitor further comprising means, e.g. liquid nitrogen, for maintaining it at a temperature not exceeding - 196‹ C. The dielectric film may be coated on a polyester film, or impregnated into a glass mat or paper. The ferroelectric material may be titanium dioxide, barium titanate or strontium titanate, or mixtures thereof and the binder may be sodium or other metal silicate, boric acid, sodium or other borate, glycol borate, phosphoric acid, phosphates such as aluminium or ammonium phosphate, carboxymethylcellulose, gum tragacanth, polyvinyl alcohol, starch paste, animal glue or mixtures thereof. Preferably the electrodes are aluminium or copper sheet or foil. The blended ferroelectric material plus binder, optionally including antifoam agents, wetting agents and glycerine, may be cast on a glass plate and partially dried, and an aluminium foil applied thereto. The film and electrode are peeled from the plate and the second electrode applied. Stacks of capacitors may be built up, or a second dielectric film applied over the second electrode and a rolled capacitor made.