GB271116A - Improvements in or relating to photo-electric cells - Google Patents

Abstract

271,116. Westinghouse Electric & Manufacturing Co., (Assignees of Zworykin, V K.). May 15, 1926, [Convention date]. Void [Published under Sect. 91 of the Acts]. Vacuum tubes.-Photo-electric cells are provided with light-sensitive metal by immersing the glass envelope 5 of the cell, freed from oxygen and containing a heated cathode 8, in a fused salt 3 maintained at a positive electric potential relatively to the cathode 8, metal ions from the salt 3 replacing corresponding metal ions in the glass and these latter ions being liberated as the metal in the container 5. The glass and salt are chosen so that the ions from the salt do not alter the structural homogeneity of the glass when they replace the ions in the glass : in introducing potassium, fused potassium nitrate and a glass containing potassium, less than 1 per cent of lead, and no sodium are used. whilst in introducing caesium or rubidium, the glass is preferably such that these metals are the only metals replaced by electrolysis. The salt 3 such as anhydrous potassium nitrate is fused in an iron crucible 1 heated by a coil 4 in heat-insulating material 2 or by a Bunsen burner. The envelope 5 is supported by a clamp 11 pivotally adjustable on a verticallyadjustable horizontal arm 12 and is evacuated by a pump to a pressure of 10<-5> mm. or filled with inert gas such as argon. The cathode 8 is heated to incandescence to emit electrons by current from a battery 24 or a transformer supplied from the source of current for the coil 4. The salt 3 is maintained at a temperature of 335‹ C., and a battery 25 in series with a current meter 27 for determining the amount of potassium produced maintains the crucible 1 positive. Alternating current may be used instead of the battery 25, the cathode 8 acting as a rectifier. Potassium ions reaching the inner surface of the envelope 5 are neutralized by electrons from the filament 8 and the potassium vaporizes and may be condensed by a cooling coil 21 to form a sensitive deposit 22 in contact with a lead-in wire 6. The deposit 22 may be activated with hydrogen to form the hydride. A prior publication of a similar method of introducing sodium into thermionic tubes is referred to.