GB1265881A - - Google Patents

Abstract

1,265,881. Cathode materials and processing. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 1 April, 1969 [4 April, 1968], No. 16969/69. Heading H1D. A thermionic electrode comprises a metal sheet support having on one surface an electronemissive coating and on the other surface a coating of a getter material which diffuses through the support and has an activating influence on the electron-emissive coating. The sheet metal support may be of Mo, Ni-plated Fe, Ni or "cathode-Ni" (i.e. Ni with a small amount of Mg, Al, Si or Zr) and between 20 and 100 Ám thick. The getter material, which is of the high temperature type since it is heated together with the emissive material, may be Zr, Ti, La, Ce or Th and may contain 20-60% by weight of W and/or Ni powder. In coating the support with getter material, metal particles, e.g. of V, Mo, Fe, Co or, preferably, Ni, are first sintered on to the support surface and the getter material, generally in the form of hydrides, is provided in the interstices between the metal particles and the coating thus formed compressed between rollers to trap the getter. The coating of emissive material on the other face of the support may be provided in a similar manner, and may comprise Ba, Ca and Sr carbonates with 1-10% by weight of Ti, Zr, Hf or Th, having a density of between 1 mg. and 10 mg. per square centimetre of emitting surface. The electrode is activated by heating. In an example the support strip is "cathode-Ni" containing 0À03-0À09% by weight of Mg, is 50 Ám thick and the coatings on each surface are 10 Ám thick, the getter being Zr with 30% by weight of Ni. The getter material is also an activator for the emissive coating, e.g., the getter may include Zr which diffuses through the support to reduce, for instance, BaO to free Ba. The electrode may be used in a diode or triode, Figs. 1 and 5 (not shown) and may comprise a cylindrical support with the emissive layer on the outside and the getter layer on the inside surface and housing a heater. Alternatively, in a low pressure Hg vapour lamp for example, Figs. 2 and 7 (not shown), the emissive layer is on the inside and the getter on the outside of a cylindrical support. Furthermore the electrode may be used in an electron gun of cathode ray tube. Electrode dimensions are given in a number of examples. In manufacturing a support, Ni particles may be magnetically aligned prior to sintering.