Vol. 41, Issue 2, pp. 341-350

Abstract

An alternative to the Spindt-type cold cathodes are the layered ones made of composite materials. The classical example are nanostructured diamond and diamond-like carbon (DLC) layers which can be very good emitters. Nanostructured diamond and DLC layers are composed of two clearly distinguishable phases: the boundaries of the diamond nanocrystals or graphite in DLC are electrically conductive, while the bulk of the diamond is a dielectric. This overview deals with various composites made with several kinds of plasma spraying techniques and tested as the cold electron emitters. Following composites were made by the atmosphere plasma spraying (APS): Cr₂O₃ (additionally laser engraved and coated with Ti layer), Al₂O₃ + 13 wt% TiO₂, Al₂O₃ + 40 wt% TiO₂ and TiO₂ (additionally laser engraved), Cr₂C₃–NiCr and Cr₂C₃–NiCrAlY. Deposited with the suspension plasma spray (SPS) were titania coatings. Layers of ZrB₂ and ZnO + 3 wt% Al₂O₃ were deposited with controlled atmosphere plasma spray (CAPS). The parameters of these cathodes are comparable with DLC ones. One of the cathodes was successfully used in a prototype light source.