DE1465389A1 - Thermistor - Google Patents

Description

xiie Carborundum Company 10/21 64

Niagara falls, N.I., USA.

U65389

The arfindun; r refers to a thermistor that is suitable for relatively high temperatures.

Thermistors are wärjneempfindliche Y / iderstände that either a positive or a negative cons-state coefficients are a function of several factors ", for example, on the composition i'heriiiistorkörpers. In general, the previously known thermistors _o more thermistors are used with a negative coefficient. Of enügten generally for specific purposes but were not suitable for very high temperatures.

The invention aims to create thermistors, which are suitable for higher temperatures than before, and relates to material compositions for the Thermistor body and on materials that give sensitivity to high temperature temperatures.

The thermistors according to the invention are at 150 ⁰ C and at ⁰ C 6QO have a resistivity in which the "ratio of Y / iderstandes at 150 C is large relative to the resistance at 6OG ⁰ C,

The drawings explain the invention.

9Q9813 / 09 $ 1

_ 2 -

The Hg.l and 2 show two possible shapes of one Thermistor according to the invention.

Fig.3 is a diagram of the temperature sensitive circuit in a thermistor according to the invention.

Mg.4 graphically shows the changes in the specific Resistance of the 'thermistors according to the Mg. 1-3 «

Mg.5 shows graphically the changes in the specific Resistance according to Example 19 below at changing temperatures.

Bs is known that thermistors for temperatures up to 1000 ° C, and sometimes higher, are made of certain ceramic Mixtures can be made. The inventive. Thermistors should essentially be used in the temperature range from 300 ° C. to about 1000 ° C. be. Such thermistors have a negative temperature coefficient of resistance, i.e. they have a resistivity at 600 G of no more than 5 x 10 ohm-cm and a resistance ratio (approx.

17 denoted ER) of about 3 χ 10: 4 x "10. The resistance ratio SR is the resistance ratio of a body of 150 ° 0 in ohm-cm to the resistance of a body at 600 ° 0, and this resistance ratio shows the resistance change in this: temperature range.

The ceramic bodies for such thermistors can have very different compositions. Bodies of oxides of polyvalent metals according to the formula M0.M'0 ^r , where M and M ^{1 are} from one group, are particularly applicable

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polyvalent metals (Gr-,) of which at least the ability of one electron lies in the 3d orbit, while the ability of at least one of the electrons of group G 2 lies in the 4d trajectory, and the Valence of all jlectrons of group G3 lie exclusively in the "s" and "p" orbital tracks, where, if u is a metal of the first group G 1, M ^{1 is} a metal of the other groups G 2 and G 3, and when H is a metal of group G 2, M 'is a metal of group G 3, and 0 and O ^{1 represent} a corresponding number of oxygen atoms, and that the thermistor has a small proportion, before. about 5 mol fo or less, contains at least one metal oxy ^ ds which modifies the resistance.

Thermistors made from solid solutions are particularly useful of tin oxide (which is a G3 dietal oxide) and titanium dioxide (which is a G 1 metal oxide), because these ihermistors can be used at temperatures up to 1000 ° C, and at an easily measurable resistance to these high temperatures have and also a high resistance ratio EE.

example 1

A mixture of finely divided SnOp and p was produced, the SnO _{2 being present} at 85 mol ^c β> and the TiCp at 15 mol fo. 0.5 mol of antimony trioxide was added to this solution as a modifier for the resistance. These powders were mixed, wet milled for two hours, and dried. The dried mixture was sieved through a sieve with an ash width of 0.95 mm and mixed with two% by weight of dry dextrin and moistened with enough water to produce good dimensional properties. The mixture was then pressed into small bars at a pressure of 420 kg / cm

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As the bars were pressed, the oxy-wire was pressed around wire electrodes placed in the mold near the ends of the bars. These electrodes consisted of a platinum wire with p, 31 mm 0 * The shaped rods were then placed on a suitable base in an electrically "heated" ceramic furnace and fired in an oxidizing atmosphere up to about 1300 ° 0 at an average of 200 ° 0 per hour . The bars were left at a temperature of about 1300 ° C for ten hours and were then cooled and tested. The resistance tests at different temperatures were carried out at 1 kc with a bridge and with alternating current. The resistance at 150 ° C was 4 »63 10 ohm-cm, and the resistance at 600 ° O was 6.18 10 ohm-cm. So the resistance ratio ER was 7.49 x 10 ² .

BelBpial 2 * ■

A thermistor body was produced according to Example 1, and the metal oxide mixture was also the same, with the exception that 5 mol $> of zinc oxide was added as a stabilizer. The resistivity of the thermistor at 150 ° C

r \ & 2?

or 600 C was 4 * 28 χ 10 or 7 »49 * 10, and the ratio BE was 5.71 ι 10 ³ .

5-5 -

With the "wipe ff run dmi slurp iron 85 mol $ snog and 15 mol TiOg Thermi8torkörpit were mountains · shares _t Ht al · modifying oxides contained 3 mol £ Zinkoacyd and a small amount of Antl * ontrioxyd or" Iya-bftlpeatoxyd. ~ See applied Terfahren, entepraoh de * of the example 1. You. Kbrjer had an epenifieoheη Wideretejad and a ti »wie felgi; t ''

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example

4th 5

Additive

0.5 Ta ₂ O ₅ 0.2 Ta ₂ O ₅ 0.2 Sb ₂ O ₅

ape 25. Resistance
in ohm-cm

150 ⁰ O

600 ° C

4.72 χ 10 ⁷ 6.82 χ 10 ² 6.92 χ IO ⁴

5.76 χ 10 ⁵ 5.76 χ ΙΟ ¹ 1.0 χ IO ⁴

3.09 x 10 ⁷ 1.33 x 10 ² 2.32 χ IO ⁵

Examples 6-10

In these examples, the mixture was 60 mol <fo p and 40 mol # TiO ₂ . As a modifier for the resistance, 0.5 mol fo Sb ₂ O _{5 was} used with various proportions of ZnO for the purpose of stabilization.

example O Additive
mol io spec.
in
150 ⁰ O X resistance
ohm-cm
600 1.49 ⁰ O 10 ³ 3.53 X IO ¹ 6th 1 ZnO 5.3 X IO ⁴ 3.13 X io ³ 4.63 X 10 ⁵ 7th 3 ZnO 1.45 X IO ⁹ 8.56 X IO ² 3.0 X 10 ⁵ 8th 5 ZnO 2.56 X IO ⁶ 7.54 X io ^a 4.61 X 1O ⁺ 9 10 ZnO 3.48 X OK ⁷ 1.92 X 10 ³ 3.90 X 10+ 10 ZnO 7.49 IO ⁷ X

The manufacture of these ffihermistors took place as well as described in example 1.

Examples 11-15

In this example the concentration was 40 mol <f * SnO ₂ and 60 mol # (EiO _{2. Various percentages of Sb 0} O, and Ta ₀ Or- were used as modifiers for the resistance, with and without zinc oxide described in example 1.

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example Additive
mol fo special resistance
in ohm-cm
150 ° C 600 10 ⁸
10? 6.93
5.98 0 X
X O 10 ⁵
10 ⁵ SE X
X 10 ⁴
10+ 11
12th 1.0 Ta ₂ O ₅
5.0 Ta ₂ O ₅ 1.36 χ
©, 45 x 10 ⁹ 1.71 X 10 * 1.96
1.58 X 10 ⁴ 13th 1.0 · Ta ₂ O ₅ ; 3 ZnOl, 39 x 10 ⁷ 1.57 X ΙΟ ⁵ 8.12 X 1O ⁺ 14th 1.0 Sb ₂ O ₃ ; 3 ZnO 2.94 x 10 ⁷ • 2.57 X 10 * 1.87 X 10 ⁴ 15th 2.0 Sb ₀ O,; 3 ZnO 5.04 x 1.96

In these examples, and also in the other examples, the mol percentages of the additives relate individually on the basic mix.

Examples 16-17

These examples relate to thermistors of a solid oxide solution and the basic mixture contains 20 mol i> SnO ₂ and 80 mol <fi TiO _2. In both examples 3 mol $> ZnO were used as stabilizing agent, together with Sb ₀ O ^ in example 16 and with Ta _n Oc in the case of

2 3 "■. 2 5

game 17 as a modifier for resistance,

Example additive specific resistance ER.

mol ia in ohm-cm

16 2 Sb ₂ O ₃ 1.03 x 10 ⁸ 2.67 x 10 ⁴ 3.86 χ ΙΟ ³

17 2 Ta ₂ O ₅ 1.89 x 10 ⁹ 1.62 χ ΙΟ ⁴ 1.17 x

The preparation was as described in Example 1.

Example 18

Using the method described in Example 1, a thermistor body was produced with a ratio of 98 mol 4 SnOg and 2 mol 56 IiO ₂ . The body contained 0.2 mol fi as a modifier for the resistance (calculated using reference - * - ■ et: 909813/0981

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on the basic mixture) Antimony trioxide »The thermistors had a resistivity at 150 ° C and 600, respectively

, 2

of 1.13 x ICr or 9.8 χ 10 °. The resistance ratio HR is therefore 1.15 ± 10 '

Example 19

To match the thermistors with the previous examples, a body was produced which only contained tin oxide as its main component and also 3 mol $ ZnO and 0.2 mol * f " SbgO", calculated from the proportion of SnO ₂ * the specific resistance in ohms -cm of this body was 1.6 10 ² at 150 ° O and 2.0 10 ° at 600 ° O, and the resistance ratio EE was 8 χ 10. The use of such bodies as thermistors is not given because of the very low resistance at high temperatures and because of the very low resistance behavior.

The 3? Ig. 1 and 2 show two of many possible porrns a resistor according to the invention.

In 3? Ig.l a thermistor 11 is shown, which the ioria of a cube hole in which the wires 13, 14 "are embedded are.

In Pig.2 the thermistor 16 is rod-shaped, and in the The wires 17 and 16 are embedded in the ends of the rod.

The termiators in the previous examples had di ··· Jarm.

.1

Xn the Sohaltdittgramm naoh? Ig.3 "ind those with 21, ZZ bezilohaet, 23 lit dtr thermistor, 24 a" • laii and 25, 26 Hind the Auelaaaklemmen. Irhbht the temperature 'read thermistor »23, then v« rrln «irt *« r against and de a thermal gate, and thus increased ileii,

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under constant voltage of terminals 21, 22, the current flows through through the coil of the relay 24. The relay armature is thus attracted, so that the current to the Outlet terminals 25> 26, which can be connected to an alarm or control device.

Me Mg. 4 shows the specific resistance when the temperatures change, namely for temperatures between 150 ° and about 700 ° C for thermistors according to Examples 1, 2 and 11. The dashed line shows the characteristics of the thermistor according to Example 1, the broken line The line shows the characteristic of a thermistor according to Example 2 and the solid line shows the characteristic of a thermistor according to Example 11. The curves allow a comparison of some of the previously described thermistors. It turns out that all three thermistors have a specific resistance at temperatures of around 400 ° 0 to around 700 ° C, which is significantly below 1 χ 10 ⁵ , and at 150 ° C above 1 χ 10 ⁶ . So there is a temperature range that is useful for thermistors.

5 shows a similar resistance-temperature diagram for a thermistor according to Example 19 »which therefore does not contain any TiOp. It is clear that the resistance this body is so small at high temperatures that the body cannot be used as a thermistor.

From the foregoing results that include in the production of thermistors from mixtures of zinc oxide and titanium oxide, the ratio of these two oxides may be mutually very different · antimony trioxide or Ta ₂ Oc, in mol-percentage of between about 0.1? 6 to 5 # of the solution of SnO ₀ and TiO _{9 are} added, and the antimony oxide then acts as a modifier

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for the resistance. Zinc oxide, which has a stabilizing effect in many compositions, can be added up to 10 mol io to the basic composition. The zinc oxide not only increases the resistance of the resistance at high temperatures, but it also gives an almost linear response to temperature changes, especially at high temperatures.

Instead of the previously described thermistors in fform The thermistors can be made of rods. other shapes such as balls, cubes, discs and curls. The lead wires, made of any material can exist, can also be omitted and replaced by mechanical contact with metal electrodes. With the appropriate Selection of the body shape of the thermistors and the size, and depending on whether lead wires or other If contacts are present, different types of thermistors can be made which have different resistances.

Other solid solutions of useful metal oxides for thermistors are solutions containing predominantly TiOp, ZrOp, SCpO, and Y ₂ O *. Modifiers for such oxides are Ta ₂ O, - and MoO ,. Here, too, ZnO can be used as a stabilizing agent.

Patent claims:

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Claims (1)

Thermistor, characterized in that it consists mainly of a solid solution of oxides of polyvalent metals, corresponding to an iOrniel MO.M ¹ O ¹ , where M and M 'are selected from a group of such polyvalent metals (G-,), of which at least the valence of an electron lies in the 3d orbit, while the valence of at least one of the electrons of the group (G ₂ ) lies in the 4d orbit, and the valence of all electrons of the group (G,) is exclusively in the "s "and" p "revolving tracks, where when M is a metal of the first group (G-,), M ^{1 is} a metal of the other group (Gp and G-); and when M is a metal of the group (Gp), M ^{1 is} a metal of the group (G,), and 0 and O ^{1 represent} a corresponding number of oxygen atoms, and that the thermistor contains a small proportion, of about 5 mol # or less, of at least one metal oxide, that modifies the resistance. 2. Thermistor according to claim 1, characterized in that a small proportion of ZnO is used as a stabilizing agent is added. 3. Thermistor according to claim 1 or 2, characterized in that M is titanium and M ^{1 is} tin. 4. Thermistor according to Anspruoh 1 or 2, characterized in that M is zirconium and M ^{1 is} titanium; 5. Thermistor according to Claim 1 or 2, characterized in that M is scandium and M 'is yttrium 9Q9813 / 0981 τ η - li - Thermistor according to claim 1 or 2, characterized in that it consists of a solid solution of SnOp and TiOp and at least one as a modifier for resistance of 5 mol # or less
contains oxides SbO * or Ta ₂ O ₅ 7. Thermistor naoh claim 6, characterized in that the molar ratio SnO ₂ : TiO _{2 is} about 98 »2 to
2 »8 is. 8. Thermistor naoh claim 7 »daduroh characterized in that the mole percentage of the modifier
active oxides about 0.1 $ - 5 #> calculated on SnO ₂ and TiO ₂ together. 9. Thermistor naoh claim 8, characterized in that about 0.1 mol # - 5 mol 56 Sb ₂ O * is added. 10. Thermistor naoh claim 8, characterized in that about 0.1-5 mol ^ Ta ₂ O _{5 is} added. 90981 3 / .09 84, '