Stratum-like structured metal alloy cathode

One of the methods for fabrication of metal alloy Ir–La cathodes is a sequential application of the alloy components suspensions in layers followed by their sintering. As a result of the components interdiffusion, an alloy layer with the proper phase composition is formed: Ir2La. At the temperature 1250 °Cbr, the life of such monolayer cathodes under thermionic emission is about 2000 h. To increase the active material reserve further, and hence the cathode life, the following approach was realised: alternating layers of iridium and lanthanum were deposited in sequence several times with intermediate annealing. Such stratum-like structured cathodes can contain a higher quantity of lanthanum up to the theoretical limit. A disadvantage of this method is the fact, that though some protective environment is used during the application of the suspension, it is not possible to completely exclude oxidation of the active alloy component lanthanum. This disadvantage can be avoided by a new method of creation of alloy Ir–La layers, based on saturation of iridium surface with lanthanum from its gas phase. The technology of the iridium surface saturation with lanthanum from gas phase helps to realise tip cathode field emitters from two-phase alloy with high curvature radius.