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→Construction: Pointing out that CdSe/Se is active junction (see metal rectifier) and that CdSe forms by reaction from SnCd alloy and Se (presumption) |
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==Construction==
[[File:Structure selenium rectifier.svg|thumb|Typical structure of a selenium rectifier{{clarify|contradicts associated text (no Bi/Ni layer)|date=August 2016}}]]
[[Selenium]] rectifiers are made from stacks of [[aluminum]] or [[steel]] plates coated with about 1 [[μm]] of [[bismuth]] or [[nickel]]. A much thicker layer of selenium (50 to 60 μm) doped with a [[halogen]] is deposited on top of the thin metal [[plating]]. The selenium is then converted into polycrystalline gray (hexagonal) form by [[Annealing (metallurgy)|annealing]]. Cadmium selenide forms by reaction of the selenium with the tin-cadnium alloy and the CdSe-Se [[heterojunction]] is the active rectifying junction. Each plate is able to withstand about 20 volts in the [[Peak inverse voltage|reverse direction]]. The metal squares, or disks, also serve as [[heat sink]]s in addition to providing a mounting place for the selenium disks. Plates can be stacked indefinitely to withstand higher voltages. Stacks of thousands of miniature selenium disks have been used as high-voltage rectifiers in [[television set]]s and [[photocopy machine]]s.
==Use==
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