High reliability, long lifetime and low temperature, high emission current density oxide cathodes are presented in this paper. The characteristics of these cathodes, such as dc and pulse emission, evaporation, resistance to poisoning and lifetime, are discussed. They have been widely applied to TWTs and klystrons with high power, long pulse and high duty ratio. The results showed that high emission current density and long lifetime can be realized. (c) 2005 Elsevier B.V. All rights reserved.