Selenium rectifier

Bismuth Selenium Tantalum rectifiers, selenium Cadmium rectifying tubes Boron nitride recycling... 

Selenium exhibits both photovoltaic action, where light is converted directly into electricity, and photoconductive action, where the electrical resistance decreases with increased illumination. These properties make selenium useful in the production of photocells and exposure meters for photographic use, as well as solar cells. Selenium is also able to convert a.c. electricity to d.c., and is extensively used in rectifiers. Below its melting point selenium is a p-type semiconductor and is finding many uses in electronic and solid-state applications. 

Iodine cataly2es the conversion of amorphous selenium to the black, semiconducting metallic modification, and is used for this purpose in the manufacture of photoelectric cells and electric rectifiers (see Seleniumand selenium compounds). 

Applications Although a wide range of metals can be sputtered, the method is often commercially restricted by the low rate of deposition. Applications include the coating of insulating surfaces, e.g. of crystal vibrators, to render them electrically conducting, and the manufacture of some selenium rectifiers. The micro-electronics industry now makes considerable use of sputtering in the production of thin-film resistors and capacitors . ... 

Sulfur vapor consists of a mixture of species that includes S8, S6, S4, and S2 (which like 02 is paramagnetic). Because the S8 molecule is nonpolar, it is soluble in liquids such as CS2 and C6H6. Selenium also consists of cyclic molecules that contain eight atoms, and tellurium is essentially metallic in character. In their vapors, several species are found that contain 2, 6, or 8 atoms. Both are useful as semiconductors, and selenium has been used in rectifiers. Because the electrical conductivity of selenium increases as the intensity of illumination increases, it has been used to operate electrical switches that open or close as a light beam is broken. Selenium was also used in light meters, but other types of meters are now available that are more sensitive. Table 15.1 gives a summary of the properties of the group VIA elements. 

Selenium photovoltaic cell, 22 100, 103 Selenium pink glass, 22 97 Selenium rectifiers, 22 99-100 Selenium ruby glass, 22 96-97 Selenium sulfide... 

Crystalline selenium is a p-type semiconductor. It acts as a rectifier that can change electric current from alternating current (AC) to direct current (to DC). It has photovoltaic proper-... 

The photosensitive nature of selenium makes it useful in devices that respond to the intensity of light, such as photocells, light meters for cameras, xerography, and electric eyes. Selenium also has the ability to produce electricity directly from sunlight, making it ideal for use in solar cells. Selenium possesses semiconductor properties that make it useful in the electronics industry, where it is a component in some types of solid-state electronics and rectifiers. It is also used in the production of ruby-red glass and enamels and as an additive to improve the quality of steel and copper. Additionally, it is a catalyst (to speed up chemical reactions) in the manufacture of rubber. 

Beryllium connections and contacts are employed for switchgear and relays. Beryllium oxide is used as substrata for electronic circuits. Cadmium is used in television and fluorescent light phosphors. Cadmium, nickel and mercury are employed in batteries such as "nicad" cells and mercury cells. Mercury is used in fluorescent lamps, electrical switches, and outdoor lamps, as well as instruments for measuring pressure, temperature, and density. Selenium is employed as a photoreceptor in copying machines, and as a semiconductor in rectifiers. Lead applications include lead add storage batteries, a component in color television glass, and, in its oxide form, use as a dielectric material. 

Rectifier - [OILS, ESSENTIAL] (Vol 17) - [SEMCONDUCTORS - SILICON-BASED SEMICONDUCTORS] (Vol 21) -selenium [SELENIUM AND SELENIUM COMPOUNDS] (Vol 21)... 

Cognate preparations. Cyclohexane-1,2-dione. Equip a 1-litre, three-necked flask with a reflux condenser, thermometer and dropping funnel. Place 250 g (2.55 mol) of pure cyclohexanone in the flask, heat to 70-80 °C and add a solution of 280 g (2.52 mol) of pure selenium dioxide in 1500 ml of rectified spirit from the dropping funnel over a period of 2 hours, maintaining the temperature at 70-80 °C. Reflux the reaction mixture for a further 2 hours. Distil off as much of the alcohol as possible and decant the liquid residue from the elemental selenium. Wash the latter several times with ether, and combine the... 

For electrolyses without potential control any DC power source (batteries or selenium rectifiers are the simplest ones) capable of delivering 1 —4 A at an applied voltage of 50—100 V will serve well for small-scale synthetic work. For electrolyses with potential control the circuit of Fig. 1 can be used, at least in principle, but of course suffers from the disadvantage of requiring continuous... 

A major use of selenium has been in photoelectric devices. Its conductivity increases with illumination, and this provides a way of measuring light intensity or operating electrical switches. However, newer types of photocells are available that are made of other materials (such as cadmium sulfide). A second and more important use of selenium is in rectifiers to convert alternating current to direct current. Also, some pigments contain selenium and tellurium compounds, and both elements have been used in vulcanization of rubber. Selenium compounds have been used in dandruff treatment shampoos, and low levels of selenium may be necessary for dietary balance. Some studies have shown that persons whose diets are deficient in selenium may have a higher incidence of heart attacks. 

It is used for decolorising glass and in photoelectric cells. The electrical conductance of Se in the metallic form is increased as much as 200 times by light. Another application is in the iron-selenium barrier-layer cell which generates a current when illuminated. This system also operates as a rectifier because current flows more readily from iron to selenium than in the opposite direction when an external potential is applied. 

Fig. 35. Circuits for medium- and high-pressure lamps. Key to (b) Tj-10 amp Variac Tj-59G37 General Electric transformer Li, L -Th, 1.5 amp dc Cj, Cj, C3-8 /rf, 1500 DCWV X-selenium rectifiers (Federal Telephone and Radio Corp. 131H24AX1) Ri-50000 ft, 150 W Ra-500 fl, 100 W rheostat, (a) From ref. 9 (b) from ref. 127.

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