US2326580A - Resistance material - Google Patents

Description

Aug. 10, 1943.

C. H TRENKLE RESISTANCE MATERIAL Filed March 27, 1942 lNl/ENTO/ BVCH. THEN/(LE ATTORNEY Patented Aug. 10, 1943 Charles H. Trenkle, Bid to Bell Telephone La New York, N. Y.,

gew oo'd, N. Y., assignor boratories, a corporation of New York Incorporated,

Application March 27, 1942, Serial No. 436,471 8 Claims. (01. 201-76) This invention relates to resistors and resistance materials which have high negative temperature coefficients of resistance, and to meth ods of making such resistors. and resistance materials. More specifically, it relates to resistance materials containing combinations of. metal oxides.

It is known that resistance materials having certain desirable characteristics may be made from heat treated combinations of metal oxides. By employing the proper proportions of these oxides for the resistance materials, series of units may be made having a wide range of specific resistance but all within a comparatively narrow range of high resistance temperature coeificients. For example, the specific resistances of manganese oxide and nickel oxide are relatively high, but a heat treated combination of the two oxides in any proportion has a lower specific resistance than either of them. Furthermore, if these oxides are mixed in such proportions that the atomic ratio of manganese to nickel i in the order of from 2 to 1 to 4 to 1, a minimum specific resistance may be obtained. The resistancetemperature coefficient of each of these oxides is relatively high in absolute value and this value is not appreciably reduced the two oxides.

for combinations of A further reduction in specific resistance may be obtained by adding to a mini- '7 mum specific resistance composition of manganese and nickel oxides, an oxide of cobalt. A

substantially m nimum resistance for this ternary composition may be obtained when the cobalt atoms comprise from to 40 per cent of the total metal atoms present.

One object of this invention is to further improve resistors and resistance materials made from oxides of metal.

Another object of this invention is to improve the resistance characteristics of resistors and resistance material containing oxides of manganese, nickel and cobalt,

A further object of this invention is to con trol the specific resistance of the resistance materials without appreciably affecting their resistance temperature coefficients.

One feature of this invention resides in the addition of a copper oxides of manganese, nickel and cobalt, in the formation of resistance material.

In accordance with another feature of this invention large variations in resistance are obtained by small changes in the copper content of resistance materials containing manganese, nickel, cobalt and copper oxides.

compound to the combinedbody with relatively low "resistivity is too high in iof, body required, and the essary to obtain the required resistance, with a that by adding very small in which:

Fig. 1 is a sectional view of a resistor illustrating one embodiment of this invention; and

Fig. 2 is a sectional view of a difierent resistor illustrating another embodiment of the invention.

It has been known, heretofore, that the addition of a suitable copper compound to manganese oxide or-a combination of manganese and nickel oxides, would reduce the specific resistance thereof. However, it has also been found that in oxide combinations containing copper atoms, there have been undesired resistance variations due to factors forming a necessary part of the manufacturing processes following formation of the resistance material. For example, high sensitivity to heating and cooling rates. Although appreciable additions of copper would markedly reduce the specific resistance, lack of uniformity and reproducibility due to the other factors was a definite disadvantage. Given the problem of making an extremely smallresistance resistance, the necessity of using a material of low specific resistance is apparent. In a situation where the manganese, nickel, copper oxide combination of minimum amount of copper neccombination of nickel, manganese and copper oxidesjis high enough to notedjdifiiculties, a different resistance material appears to be indicated. It has been discovered cobalt 'oxide composition, specific resistance can be obtained without the previously noted deleterious effects. For example, if to a composition of oxides in which the approximate atomic ratio of metals is 52Mnz16Niz32Co there is added a small amount of a copper compound so that the resulting oxide mixture has an atomic ratio of metals of approximately -Mn :16Ni:30Co:4Cu, a six fold reduction in specific resistance is attained. In such a composition the amount of copper with relation to the total metal present is about 4 per cent. The absence of difiiculties with this composition previously ascribed to the presence of copper may be due to the relatively small amount of copper present therein. Whatever the reason may be, the fact remains that tests show that combinaresistance for the size aggravate the above-,

tions of this approximate composition have the required low specific resistance and are not subject to the previously noted handling difficulties.

asaasso opposite faces of the disc and the leads soldered thereto.

Although specific embodiments of this invention have been shown and described, it will be understood that modifications may be madetherein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is: 1. A resistance material consisting of intimately mixed, collectively heat treated oxides of f'inanganese, cobalt, nickel and copper in which 1200 C. is satisfactory. The temperature and atmosphere of heat treatment are regulated in accordance with the resistance desired. The resistance of the material, as previously indicated. isa function of the relative amounts or the metallic elements present after the materials are combined. The atmosphere of heat treatment determines the amount of oxygen in the finished product which also affects the resistance value. The initial materials may be in the form of oxides, or other compounds of the required metallic elements which will produce a combined oxidic material upon proper treatment. For example,

all or some of the materials may be combined in the form of finely powdered carbonates which mixture may be changed to a combination of oxides by suitable calcining. Where a relatively small amount of one of the metallic elements is required, such as the copper in the present composition, it maybe added in theform of a soluble compound such'as a nitrate dissolved inwater.

Reference in this specification and the appended claims to totalmetal present, metallic elements, metals generally or to the specific metals manganese, nickel, cobalt or copper is not intended to refer to metals as such, but to the metallic elements in the resistance combination or a constituent thereof, the atomic viewpoint being intended. The resistor units may be made in several forms, two of which are shown in Figs. and 2, respectively.

A bead type unit, such as that shown in Fig. 1,

may be made by mixing the finely divided constituents and forming a paste with a suitable binder. The binder may be water or preferably comprises a solution of a compound of the metal appearing in the smallest proportions, in this case copper. For example, having obtained a mixture of the oxides of manganese, nickel and cobalt in proper proportions, these may be mixed "with water to which has been added a sufiicient amount of copper nitrate to give the desired amount of copper in the resistance composition.

The resulting paste is formed into bodies, such as bead It, on parallel wires ll of refractory conductive material, such as platinum'or an alloy of platinum and iridium. The bodies or beads are then dried and heat treated.

A unit of the disc or plate type, such as is shown in Fig. 2 may be made by intimately mixing the finely divided oxides, pressing them into a body 29 and heat treating said body. Contact electrodes may be applied to opposite faces of the heat treated disc by-any adequate means. A suitable connection can be made by applying metallic paste to the surfaces and imbedding conductive leads 22 therein. The units may then be heated to solidify the paste into electrodes 2| firmly bonding the leads 22: to the resistance body 2p. The electrodes may also be applied to the metallic elements are present in amounts according to thaorder given, the amount of manganese being the greatest and of the order. of

more than about one-half aridthe amount of copper being less than approximately one-sixth of the total metallic elements present.

2. A resistance material consisting of intimately mixed, collectively heat treated oxides of manganese, nickel, cobalt and copper in which of the total metal present, manganese comprises about 50 per cent, copper about 5 per cent, the

remainder cobalt and nickel of which remainder cobalt exceeds nickel and the sum of cobalt and nickel is less than the manganese.

3. A thermally sensitive resistance material consisting of intimately mixed, collectively heat treated oxides of manganese, nickel, cobalt and copper, the major portion of the material comprising the oxides of manganese, cobalt and nickel among which the manganese exceeds the sum of the cobalt and nickel and the cobalt exceeds the nickel, and a small remainder of copper oxide, the copper oxide content being less than about 5 per cent of the whole.

4. A resistance material consisting of 'intimately mixed, collectively heat treated oxides of manganese, nickel, cobalt and copper in which the manganese to nickel ratio ranges between 2 to 1 and 4 to 1, the cobalt is in the order of 30 per cent, and the copper in the order of 5 per cent of the total metal present.

5. A resistance material consisting of the combined oxides of manganese, nickel, cobalt and copper sintered at about 1200 C. and in which the atomic ratio of metalsis approximately 50 manganese 16 nickelz30 cobalt:4 copper.

6. A resistance material consisting of the combined oxides of manganese, nickel, cobalt, and

copper heat treated at a temperature between 800 and 1450 C. in which the percentage-range of metals with respect to the total metal present is 50 to per cent manganese, 13 to 18 per cent nickel, 25 to 40 per cent cobalt and 1 to 5 per cent copper.

7. A resistance material consisting of a composition of metal-oxygen compounds, the metal

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