US3925261A

US3925261A - Exponential resistance material and method of manufacturing same

Info

Publication number: US3925261A
Application number: US489182A
Authority: US
Inventors: Inge Lauterbach-Dammler
Original assignee: Conradty Fa C
Current assignee: C Conradty Nuernberg GmbH and Co KG
Priority date: 1973-07-18
Filing date: 1974-07-16
Publication date: 1975-12-09
Anticipated expiration: 1992-12-09
Also published as: DE2336504B2; FR2237860A1; NL7409767A; SE395788B; GB1461116A; DE2336504A1; FR2237860B1; IE39620B1; IE39620L; IT1017155B; SE7409336L

Abstract

A voltage drop across a resistance element, wherein the resistance varies exponentially with the voltage, is expressed by the equation: E B X I1/n WHEREIN I is the current through the element, B is a constant and is equal to the voltage value at which the current through the element is equal to 1 Ampere, and E is the voltage drop. To achieve a variable B-value based on the resistance material itself and furthermore to achieve a greater dependence of the resistance on the voltage drop, the value of n can be selectively raised by varying the composition of the resistance element as follows: 50 - 90% ZnO 0.1 - 40% ZnF2 0.1 - 40% MeO wherein MeO is an oxide selected from the oxides of magnesium, calcium, strontium, barium, iron, cobalt, lead, boron, aluminum, bismuth, manganese, chromium, nickel, antimony, and mixtures thereof. An improved method of manufacturing such a resistance material is also described.

Description

United States Patent 91 Lauterbach-Dammler EXPONENTIAL RESISTANCE MATERIAL AND METHOD OF MANUFACTURING SAME [75] Inventor: Inge Lauterbach-Dammler,

[30] Foreign Application Priority Data July 18, 1973 Germany .t 2336504 [52] US. Cl. 252/519; 252/518; 252/520; 264/61; 264/67; 264/104 [51] Int. Cl. 01B 1/08 [53] Field of Search 252/518-521; 264/67, 61, 104

[56] References Cited UNITED STATES PATENTS 3,642,664 2/1972 Masuyama et a1 252/519 3,658,725 4/1972 Masuyama et a1 .t 252/519 X Primary Examiner-Benjamin R. Padgett Assistant Examiner-E. Suzanne Parr Attorney, Agent, or Firm-Gifford, Chandler & Sheridan 1 Dec. 9, 1975 [57 ABSTRACT A voltage drop across a resistance element, wherein the resistance varies exponentially with the voltage, is expressed by the equation:

E a x 1" wherein I is the current through the element, B is a constant and is equal to the voltage value at which the current through the element is equal to l Ampere, and E is the voltage drop. To achieve a variable B-value based on the resistance material itself and furthermore to achieve a greater dependence of the resistance on the voltage drop, the value of n can be selectively raised by varying the composition of the resistance element as follows:

50 90% ZnO 0.1 40% ZnF 0.1 40% MeO wherein MeO is an oxide selected from the oxides of magnesium, calcium, strontium, barium, iron, cobalt, lead, boron, aluminum, bismuth, manganese, chr0- mium, nickel, antimony, and mixtures thereof. An improved method of manufacturing such a resistance material is also described.

10 Claims, No Drawings EXPONENTIAL RESISTANCE MATERIAL AND METHOD OF MANUFACTURING SAME BACKGROUND OF THE INVENTION The invention relates to a resistance material wherein the resistance varies exponentially with the voltage drop and, more particularly, relates to a sintered ceterminal wires (pigtails) can be attached.

ramic material for non-linear resistance elements. The

invention also relates to a method of manufacturing such material.

Such resistance materials are well known and have been made from, for example, silicon carbide, titanium dioxide or zinc oxide. The voltage drop across elements made from such materials is given by the following equation:

wherein E is the voltage drop over the element, I is the current flowing through the element, and B is a constant reflecting the voltage value at current I 1 Ampere. The exponent n is, therefore, a direct measure of the magnitude of non-linearity based on p-n-transitions, on the contact among the individual grains, or on the material itself.

It is known that the B-value of a non-linear resistance element may be varied by sintering at varying temperatures and under different atmospheres. It is further known to adjust the B-value through the thickness of the resistance elements. Both procedures permit only a limited possibility of variation. Thus, when there is a change in temperature the desired n-value, in many cases, is not attained and when there is a change in thickness, desired small increments of resistance often are not attainable.

DESCRIPTION OF THE INVENTION It is therefore an object underlying the invention to provide a composition wherein the electrical resistance is greatly dependent on voltage and thus has a large nvalue anda variable B-value based on the material itself.

It is a further object to provide a method of manufacturing such a composition.

The first object is particularly advantageously solved by a composition comprising about 50-90% ZnO, about 0.1 40% ZnF and about 0.1 40% MeO; wherein MeO is an oxide selected from the oxides of magnesium, calcium, strontium, barium, iron, cobalt, lead, boron, aluminum, bismuth, manganese, chromium, nickel, antimony, and mixtures thereof. According to the invention, the B-value of the material may be varied within wide ranges by changing the ratio of the two components ZnO and ZnF,. If, meanwhile, the metal oxide content is kept unchanged, the n-value of the material remains nearly constant. However the nvalue can be adjusted to many values by varying the MeO content.

The following Examples and the Table explain in more detail the relationship of the electric properties of the compositions of the invention and the method of manufacture of the compositions.

EXAMPLE 1 Two mole each of Bi O C0 0,, MnO, and Sb O (a preferred composition) were homogeneously mixed with varying amounts of ZnO and ZnF After a presintering at 600C the material was ground, compacted to As can be seen from the values in Table l, the B- value increases nearly linearly with increasing ZnF content, whereas the n-value of 20 to 25 remains nearly constant.

EXAMPLE 2 Three mole of each of Bi.,o,, C0 0 Mn0 and Sb O were homogeneously mixed together with varying amounts of ZnO and ZnF and were further processed according to the procedure described in Example l.

The electrical values of the resulting element are listed in Table 1 (numbers 7-9). A comparison with Examples 1 to 6 shows that a small change in the metal oxide content effects a considerable change in the nvalue.

Repetition of the fore going examples with a wide variety of compositions having difiering ZnO to ZnF, ratios and difiering proportions of the oxides of the invention established that the advantages of the invention were attained when the ZnO was in the range of about 50-90%, the ZnF, was in the range of about 0.1 40%, and the MeO was in the range of about 0.1 40%. Further, the composition was found to be particularly useful when the ZnF content was about 1-8% and the MeO content was about 2-l6%.

Similarly, repetition of the above examples with presintering at various temperatures and annealing the formed element at various temperatures showed that the best forming conditions for the resistance mate rial was presintering at about 600900C and annealing at about lO00-l400C.

It is, of course, to be understood that the present invention is not limited to the specific examples given, but also comprises any modifications within the scope of the appended claims.

I claim:

1. A composition adapted for use as an electrical resistance element wherein the electrical resistance varies exponentially with the voltage drop across the elementksaigl vp ltage drop being given by the equation:

X I wherein E is said voltage drop; I is the current through the element, B is a constant equal to the voltagevalue at which the current is equal to l Ampere, and n is a number; said composition comprising about 50-90% ZnO, about 0.1 40% ZnF and about 0.1 40% MeO; wherein MeO is an oxide selected from the oxides of magnesium, calcium, strontium, barium, iron, cobalt, lead, boron, aluminum, bismuth, manganese, chromium, nickel, antimony, and mixtures thereof.

2. The composition according to claim 1 in which the ZnF proportion is about l8% and the MeO content is about 246%.

3. The composition according to claim 1 wherein said MeO is approximately equal molar proportions of Bizoa, C030, Mnoz, and Sb203.

4. The composition according to claim 2 wherein said MeO is approximately equal molar proportions of Bigoa, C0304, M1102, and sbgoa.

5. The composition according to claim 1 wherein said composition is in the form of a resistance element.

6. The method of manufacturing a composition adaptable for use as an electrical resistance element which method comprises the steps of a. forming a homogeneous mixture of about 50-90% ZnO, about 0.1 40% ZnF and about 0.1 40% MeO wherein MeO is an oxide selected from the oxides of magnesium, calcium, strontium, barium, iron, cobalt, lead, boron, aluminum, bismuth, manganese, chronium, nickel, antimony, and mixtures thereof;

b. sintering said mixture at about 600-900C.;

c. grinding the sintered mixture;

d. compacting the resulting mixture; and

e. annealing the resulting material at about 1000 7. The method according to claim 6 wherein said ground mixture is compacted to the form of a resistance element.

8. The method according to claim 6 wherein said MeO is approximately equal molar proportions of Blzoa, C0304, Mnoz, and Sb203.

9. The method according to claim 7 wherein said MeO is approximately equal molar proportions of Bi o C0 0 Mno and Sb O 10. The method according to claim 6 and further comprising the step of positioning metal electrical contacts on portions of said resistance element.

Claims

1. A COMPOSITION ADAPTED FOR USE AS AN ELECTRICAL RESISTANCE ELEMENT WHEREIN THE ELECTRICAL RESISTANCE VERIES EXPONENTIALLY WITH THE VOLTAGE DROP ACROSS THE ELEMENT, SAID VOLTAGE DROP BEING GIVEN BY THE EQUATION:

2. The composition according to claim 1 in which the ZnF2 proportion is about 1-8% and the MeO content is about 2-16%.

3. The composition according to claim 1 wherein said MeO is approximately equal molar proportions of Bi2O3, Co3O4, MnO2, and Sb2O3.

4. The composition according to claim 2 wherein said MeO is approximately equal molar proportions of Bi2O3, Co3O4, MnO2, and Sb2O3.

6. The method of manufacturing a composition adaptable for use as an electrical resistance element which method comprises the steps of a. forming a homogeneous mixture of about 50-90% ZnO, about 0.1 - 40% ZnF2, and about 0.1 - 40% MeO wherein MeO is an oxide selected from the oxides of magnesium, calcium, strontium, barium, iron, cobalt, lead, boron, aluminum, bismuth, manganese, chronium, nickel, antimony, and mixtures thereof; b. sintering said mixture at about 600*-900*C.; c. grinding the sintered mixture; d. compacting the resulting mixture; and e. annealing the resulting material at about 1000* - 1400*C.

7. The method according to claim 6 wherein said ground mixture is compacted to the form of a resistance element.

8. The method according to claim 6 wherein said MeO is approximately equal molar proportions of Bi2O3, Co3O4, MnO2, and Sb2O3.

9. The method according to claim 7 wherein said MeO is approximately equal molar proportions of Bi2O3, Co3O4, MnO2, and Sb2O3.

10. The method according to claim 6 and further comprising the step of positioning metal electrical contacts on portions of said resistance element.