Life Characteristics and Changes in the Emitting Layer of Low Temperature Operating Cathode

Abstract

An electron emitter pellet for low temperature operating cathode has been developed by integrating a mixture of (Ba, Sr, Ca)CO₃ powder, Ni powder and Sc₂O₃ powder using hot isostatic pressing (HIP). During the exhaustion process of cathode ray tube (CRT), an emitting layer composed of oxide emitter is formed on the pellet surface. During emission, this emitting layer plays an important role. In this study, we performed life tests of the pellet at high current density. Emission properties were evaluated by measuring maximum cathode currents and observing cathode images. In addition, time course changes of the emitting layer were examined. Superior life characteristics of less than 3% and 20% reduction in the maximum cathode current 1.5×10₄h and 3.5×10₄h, respectively, after the start of the high current application life test with an average current density of 3A/cm₂, ten times as large as practical current density of CRTs, were obtained. These conditions reveal that the pellet exhibits superior life properties against high current loads. The emitting layer on the pellet surface develops irregularities 1.5×10₄h after the start of the life test, with a part of Ni exposed. The emission properties of the pellet do not deteriorate regardless of such irregularities in the emitting layer; this is considered to be because Ba is supplied from the inside of the pellet, and BaO covers the entire pellet surface.