Ir-coated dispenser cathode for CRT

A compact dispenser cathode has been developed for application to cathode ray tubes (CRTs). A cathode emitter, comprising BaO, CaO, and Al/sub 2/O/sub 3/ in a molar ratio of 4:1:1, was impregnated into a porous tungsten pellet. An intermetallic compound of tungsten and iridium was formed on the cathode pellet. Heater ratings were 6.3 V*0.2 A. Emission characteristics were measured by using color CRTs. As a result, a cathode peak loading of 15 A/cm/sup 2/ was ensured in the space-charge region. Furthermore, life tests with a peak loading of 7.5 A/cm/sup 2/ were conducted over 10000 h. The decrease in emission current after 10000 h was within only 10% of the initial value. Reliability of cathode performance was assured in terms of breakdown potential between the heater and the cathode, emission characteristics, life performance, grid emission, and the drift in cutoff potential. In addition, the effects of the coating thickness on the emission characteristics are discussed.<
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