Enhancement of electrical conductivity and emission stability of oxide cathodes using Ni addition

An investigation has been carried out into the use of conductive phase additions to enhance the conductivity and emission behavior of the oxide cathode coating as used in CRTs. Electrical and emission characteristics have been studied for various additions of filamentary nickel (Ni) added to the sprayed strontium-barium carbonate precursors prior to spray deposition, followed by conventional thermal conversion and activation processes in vacuum. The conductivity and the electronic activation energy have been studied as a function of temperature in the range 300 to 1250 K, during conversion and activation processes allowing the conduction behavior to be compared to conventional materials. The conduction behavior has been found to change as a function of heat-treatment temperature as the conduction paths develop and subsequently evolve in the microstructure of the resultant composite coating during conversion, activation and subsequent aging/service life conditions, with metallic-dominated conduction at temperatures below 850 K and pore conduction mechanisms dominating at higher temperatures. The emission characteristics immediately after conversion are impaired by the Ni addition, however, the long-term emission characteristics show improvement with the conductive phase.