| 摘要 |
796,896. Selenium rectifiers. STANDARD TELEPHONES & CABLES, Ltd. Feb. 17, 1956 [Feb. 24, 1955], No. 5000/56. Class 37. A method of making a selenium rectifier comprises forming a layer of hexagonally crystalline cadmium selenide on the selenium before the application of a counter electrode. Such a layer is of low resistance and limits diffusion of counter electrode material into the selenium during operation. The layer may be formed by simultaneously evaporating cadmium and selenium in vacuum from separate vaporizers on to a selenium layer heated to 130-140‹ C. by heating wires at the back of the base-plate. Measured small doses of Cd and Se may be used in the vaporizers and the bases may be exposed to such vaporizers several times to give the required layer thickness. Before the application of the Cd and Se the Se may be treated with thallium or alkali, e.g. caesium salt solutions, or with evaporated solid or gaseous material, and the Cd and Se may be applied before or after conversion of the Se to its high conductivity form. A small quantity of thallium which may be required for the forming process may be applied before or with the first portions of Cd and Se by vaporization of a eutectic alloy of 83 per cent by weight of thallium and 17 per cent of cadmium. The Cd and Se may be evaporated simultaneously or in rapid sequence. In the latter case the first portion of Cd is replaced by the alloy. Reference has been directed by the Comptroller to Specification 630,785. |
