Emission material for impregnating electron tube cathode - with porous sintered matrix, contains aluminium, barium, calcium, strontium and opt. tungsten

摘要

Electron tube has a porous sintered matrix cathode impregnated with emission material (I) in the form of Al, Ba and/or Ca cpd(s). The novelty is that (I) contains 0.01-5 (0.05-2.0) (wt.)% Sr. The change in emission properties with time is minimised. The cathode is esp. useful in moving field tubes. Pref. (I) also contains 1-12 (4-10, esp. 6-8)% W and the porous matrix consists of W. (I) is prepd. by fusing a mixt. of Al2O3, BaCO3, CaCO3 and 0.1-10 (0.2-5, esp. 0.5-2)% SrCO3 at 1250-2500 deg.C. Fusion can be carried out in a W boat or 1-11 (4-10, esp- 6-8)%W powder or 1.5-13.5 (5-11.5, esp. 7-9.5)% W oxide can be added.