Importance

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Abstract

An electron tube cathode is disclosed, comprising a base, electron emissive material layers formed on the base and containing alkaline earth metal oxides including barium, and reducing metal layers interposed between the emissive material layers. The metal layers comprise at least one metal selected from W, Mo, Ta and Ti. The metal layers further comprise any one of rhenium, yttrium or a mixture thereof in the amount of 3 to 5 wt % thereof. The amount of the entire metal layer is 8 to 15 wt % of the entire emissive layer comprising the emissive material layers and the metal layers. The entire metal layer has a thickness of 3 to 5 .mu.m. Each of the metal layers comprise at least one or more layers formed by means of a spraying method. The present invention provides advantages of enhancing emission characteristics and life characteristics of the cathode by increasing the amount of free Ba. The present invention further provides advantages of enabling an operation of the cathode at a lower temperature due to an increase of the radiant heat of the metal layer and the temperature of the cathode. The present invention also serves to enhance life characteristics of the cathode at a high current density of 3A/cm.sup.2 as well as thermal characteristics of the cathode and reduce electric power consumption.

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First Claim