US2232960A - Thermoelectric element and method of making the same - Google Patents

Description

Patented Feb. 25, 1941 Y TnEnMoELEcTnIc ELEMENT AND METHOD or AKING THE SAME Henry Reginald Milnes, Bingley, England No Drawing.

Application September 14. 1937,

lsggal No. 163,809. In Great Britain August 24,

6 Claims.

This invention relates to new compositions of matter, and more particularly to alloys for use as thermo-electric generator elements and to the method of producing said alloys.

The chief object of the present invention is to provide novel compositions of matter which may be used for thermo-electric generator elements. A thermo-electric generator apparatus in which thermo-electric elements according to the present invention are employed, is described in my copending application Ser. No. 163,810.

Another object of the invention is to produce a thermo-couple having positive and negative elements consisting of the new alloys.

3 According to the present invention, the substances which form the thermo-electric elements are each composed of an element of Group I of the periodic table saturated with selenium.

According to a further feature of the invention, each such substance is composed of two elements of Group I of the periodic table alloyed together in such proportions that the one element predominates over the other.

From another aspect, each substance comprises -17 copper or silver or an alloy of copper and silver in which either the copper or the silver predommates, in combination with selenium.

The selenium may be replaced by oxygen, tellurium or sulphur with a. certain but lesser dezm gree of success, or any or all of these three shall exceed that of the silver by about three times, while in an alloy in which the silver prevails the quantity of the latter shall be about twice that of the copper, although these proportions may be varied to a large extent.

' A selenium saturated copper-silver alloy. in which the copper predominates is hereinafter referred to as the positive element. A selenium saturated silver-copper alloy inwhich the silver predominates, is hereinafter referred to as the negative element. l

The positive element is preferably composed of copper, silver, copper oxide (CllzO or CuO) and 5 selenium. The addition of silver serves to lower the electrical resistance of the alloy. The addi-, tion of copper oxide gives improved results but is by no means an essential constituent. To the element-either with or without copper oxideadditions of other substances may be made for 5 particular purposes, in order to alter the hardness of the resultant alloy or to increase the melting point. It is preferred as an example of a low resistance alloy, that the composition of the positive alloy is about 70 per cent. of copper, about 24 per cent. of silver, and about 6 per cent. of copper oxide (C1120). The copper and silver are alloyed together by melting them together until mixed,

whereai-ter the alloy is allowed to cool to a dull red. The selenium is now sprinkled on the surface of the alloy, which will readily absorb it. The alloy is again heated until melted, stirred well and more selenium sprinkled on it after cooling to dull red. This process is repeated many times, adding more and more selenium, unoil the mixture will not absorb any more. Any further additions will result in the extra selenium going away as agas, but .the result is a mixture containing selenium to a little over saturation point. The C1120 or 0.10, when added, will readily absorb the extra selenium, and a little more selenium may need to be added to give full saturation.

A negative element consisting of silver selenium gives good results, but much improved results are obtained by the addition of copper, in which case the alloy has a preferred composition of about 66%rds per cent. of silver and about 33 l rd per cent. of copper. The impregnation with selenium or the alloying and impregnation is carried out similarly to copper alloy. No appreciable additions of other elements or metals may be made to this alloy, as otherwise the potential would be lowered or the polarity of the current generated would be reversed.

A current may be generated by combining a negative element (copper alloy+seleniuml with a positive element (copper-silver alloy+selenium), heating the Junction and withdrawing the produced current.

I claim:

1. A thermo-electric couple, comprising a positive thenno-electric element consisting of an alloy containing about three parts of copper and about one part of silver and being saturated with selenium, and a negative thermo-eleotric element consisting oi an alloy containing about two parts of silver, and one part oi. copper and being saturated with selenium.

2. An alloy suitable as a positive thermo-electrio element, said alloy consisting of about three parts 0! copper and about one part 0! silver and being saturated with selenium. I

3. An alloy suitable as a positive thermoelectric element, said alloy consisting of about '10 ,parts of copper, about 24 parts of silver and about 6 parts of copper oxide and being saturated with selenium.

4. A method 0'! producing an alloy for use as a positive thermo-electric element, said method comprising the steps of melting together about 70 parts of copper with about 24 .parts of silver until an alloy is formed, cooling the alloy to a dull red. sprinkling on the surface of the alloy 9. quantity of selenium which is absorbed by the latter, remelting the alloy, stirring the remoi-ten alloy thoroughly, and repeating the cooling, sprinkling, remelting and stirring steps until no more selenium is absorbed by the alloy after the last cooldull red, sprinkling on the surface of the alloy 9,

quantity of selenium which is absorbed by the latter, remelting the alloy, stirring the remolten alloy thoroughly, and repeating the cooling, 15

sprinkling, remelting and stirring steps until no more selenium is absorbed by the alloy after the last cooling step. I

HENRY REGINALD MILNES.