The Photoelectric and Thermionic Properties of Platinum Coated Glass Filaments

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Abstract
The photoelectric and thermionic properties of platinum sputtered glass filaments are discussed, special attention being given to the effect of temperature, and to electrolysis of potassium through the glass to or from the sputtered coating. When electrolysis is away from the surface, the photoelectric threshold is independent of the temperature up to 450° and is close to 2720A. With electrolysis toward the surface the threshold remains at 2720A up to 260°C above which it shifts toward the red with rising temperature, reaching a maximum value of about 4300A at 410°C. Electrolysis produces identical effects on the photoelectric and thermionic emissivity for electrons; the effect on positive ion emission is similar, also, except that a peculiar maximum in the emissivity occurs for a specific electrolysis potential. Ultraviolet radiation has no effect on the thermionic emission of electrons or positive ions from this type of filament.

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