DE1941280C3 - Semiconducting ceramic resistor with positive temperature coefficient - Google Patents

Description

The invention relates to a semiconducting ceramic Resistance with a positive temperature coefficient consisting mainly of barium titanate with a grade of - in each case in oxide form - at least 0.2 mol% silicon and at least 0.23 mol% of rare Earth, bismuth and / or antimony.

A semiconducting ceramic ·. rather, understanding with barium titanate of this type is known from "IEEE Transactions on Component Parts", 1963, pp. 53-57, and also from DE-PS 9 29 350. The SiO ₂ acts as a "mineralizer" to improve the sintering behavior of the ceramic and to reduce the voltage dependence of the specific resistance.

It is known that barium titanate ceramic, which is normally an insulator, can be doped with certain elements become semiconducting with a steep rise in a certain temperature range Temperature resistance curve. It is because of these properties that such semiconducting ceramics are found diverse application for temperature control, current regulation or the like. For this use it is it is desirable that the temperature coefficient of the specific resistance is as steep as possible, over a Extends as large an area as possible and lies in a relatively low temperature range.

In "Proceedings 1955 Electronic Component Symposium" is about studies with semiconducting Barium titanate ceramics reported that to achieve a positive temperature coefficient of resistance are doped with lanthanum, as well as studies on the low-barrier contacting such ceramics using indium gallium. As a substitute for lanthanum as a dopant there are others Elements such as bismuth, thorium and rare earths for substituting the BaFium ions or tungsten, niobium and tantalum have been proposed to substitute the titanium ions. Later systematic investigations (Jour ^ nal of the Physical Society of Japan, 1959, pages 1159-1174) about the usability and optimal Concentrations of a variety of doping elements have shown, however, that only with certain doping devices, especially rare earths, Bismuth and antimony, ceramic properties are achievable while others, due to their semiconductor properties Valences also considered elements, especially manganese, the ceramic is not semiconducting make and therefore do not come into consideration as doping elements.

The subject of the earlier German patent 14 15 430 is also a semiconducting one doped with antimony Barium titanate ceramic, in which the Curie point u_; d the ίο Location of the resistance-temperature curve through partial Replacement of the barium atoms by strontium atoms can be shifted, with a reduction in the achievable maximum temperature coefficient of the electrical resistance by adhering to a specific Amount ratio between strontium and antimony is counteracted.

In all of the ceramics mentioned so far, the temperature-dependent increase in resistance extends over a relatively small range of only about three powers of ten for the specific resistance.

There are also from JP-AS 12 146/66 and 3 855/67

Ι «*» 11 * ΙαΪ · α> «Ί '* Da« .. »*! *» · - ·. · »!. ** -. *» !!. ~ ._ * L> l. _n __. Λ '. ~. _! __ iia.iL/ivii.uiiuv υαι iuiiiLtiaitaLi \ ci aiiuncii ucnainii, uic cmc doping with rare earths, bismuth or antimony, the barium ions of which are partially replaced by strontium. Tin, lead or zirconium are substituted and which also contain a maximum of 0.03 wt.% Manganese (corresponds to 0.128 mol%) / ·.

As a result of the addition of manganese, these ceramics have a steep and too low temperature shifted resistance increase over a large range of approx. five powers of ten of the specific Resistance. However, these ceramics have the disadvantage that they have this favorable course of the Show resistance characteristics only at low input voltages, while at higher input voltages the resistance at higher temperatures and thus the resistance characteristic drops sharply. Further these ceramics have the property that they are in an atmosphere with low oxygen partial pressure high temperatures and then lose their favorable resistance characteristic.

The invention is based on the object of a semiconducting ceramic resistor with positive To create temperature coefficient of the type mentioned, starting from a small Specific resistance at room temperature has a large temperature coefficient over a large Range of specific resistance even when high voltages are applied and also after the previous one Has heat treatment in an atmosphere other than air.

To achieve this object, according to the invention, a semiconducting ceramic resistor is described at the outset specified type characterized in that the ceramic also - in oxide form - 0.Ϊ 3 to 0.45 Mol% manganese contains that the content of silicon is up to 15 mol% and that the content of rare Earth. Bismuth and / or antimony exceeds that of manganese by 0.1 to 1.2 mol%.

It has been found that the manganese in combination with the other specified additives and in Compliance with the specified proportions in concentrations significantly higher than 0.03% by weight can be used, whereby not only a very steep temperature-resistance curve over a A large range of specific resistance can be achieved with a low room temperature resistance can, but also this property when creating

higher input voltages is retained, and that the ceramic also has a particularly good resistance against heat treatment in an atmosphere other than air as well as particularly good and against high Stress insensitive lifetime under operating conditions.

One embodiment of the invention is through the addition of titanates other than barium titanate or Zirconates and / or stannates marked

An addition of Al2O3 is particularly advantageous more than 0.5 mole percent to the semiconducting ceramic resistor according to the invention. Through this there is a decrease in the rate of water absorption of the semiconducting ceramic resistor achieved

As a base material for the production of the semiconducting Ceramic resistor according to the invention, a customary ke / amic composition can be selected, the barium titanate alone or as a main component (i.e. not less than 50%), optionally with one or more Additives (e.g. titanates other than barium titanate such as z. B. Cäieiurnikanal or struntium titanate Zir "'. Onatt.n or stannates). Particularly preferred is a base material in which no more than 40% of the Barium titanate are replaced by strontium titanate.

The ceramic semiconductor resistors obtained in this way have a markedly large, positive temperature dependence of the resistance and favorable switching properties, since the specific resistance increases suddenly in a certain temperature range. The ceramic semiconductor resistor has only a low dependence of the specific resistance on the voltage, even at high Temperatures. In addition, it is excellent and insensitive to the applied voltage Lifetime, and the resistance-temperature characteristic when treated under atmospheric conditions Influences hardly influenced

Accordingly, the ceramic semiconductor resistor of the invention can be used as a thermal element in the High voltage regulation, current regulation, in thermostats or the like. Can be used.

The invention is explained in more detail below using an example.

Using BaCO ₁ , SrCO ₃ , CaCO ₃ , TiO ₂ . Ce ₂ (CO)) BYO ₃ , MnCOj. SiO ₂ and AlvO ₃ as starting materials, the compositions given in Table 1 were produced, the added amounts of Ce ₂ (CO ₃ )) and Y ₂ Oj to facilitate comparison in each case as molar ratios of Ce or CeOi 5 and Y or YOi 5 are specified. Similarly, the amount of manganese is only given in relation to the manganese content. The samples No. 1. 2, 5. H and 17 are not within the inventive limits. Each composition was placed in a polyethylene-lined ball mill along with agate balls and wet-milled for 20 hours. After removing the water, the resulting mixture was calcined at 1170 ° C. for 1 hour. The calcined material was placed in a ball mill along with agate balls and about 3 percent by weight vinyl caustic and mixed for about 20 hours 800 kg / cm ² pressed into a round disc about 14 mm in diameter and about 3 mm thick. The pressed material was sintered in a tunnel furnace in an autogenous atmosphere at 1370 ° C. for 1 hour

An indium-gallium alloy was placed as an electrode on each surface of the sample thus obtained applied with ohmic contact. The temperature dependence of the specific resistance was measured by applying a direct voltage of 0.5 to 1.5 volts per 1 mm of thickness. The results are in Table 2 given. Some typical results are shown in FIG. 1 shown graphically

From Table 2 and F i g. 1 it can be seen that there is a large, positive temperature dependence of the resistance only in those ceramic semiconductor resistors in which manganese and one or more rare earth elements. Bismuth and antimony are present in certain quantitative proportions. If the proportion of rare earths, bismuth and / or antimony is too small compared to that of manganese, the specific resistance at room temperature exceeds 10 ⁶ Ω-cm, and the positive temperature dependence of the resistance is small. In the case of the composition according to the invention, the specific resistance at room temperatures is small and the positive temperature dependence is markedly large. In particular, it can be seen from Fig. 1 that the ceramic bodies according to the invention (solid lines 3, 4, 24) have a low specific resistance at ordinary temperature, a pronounced positive resistance-temperature characteristic and a steep increase in the specific resistance compared to that outside of the Invention lying composition (dashed line 2). The ceramic bodies according to the invention thus have excellent switching properties.

The above samples were kept at a temperature which was so high that the specific resistance reached its maximum, ie about 200 ^° C., and a direct voltage of 1 to 100 volts per 1 mm thickness was applied. The dependence of the resistivity on the voltage under these conditions was measured and is shown in FIG. 2 shown. It can be seen from this figure that the ceramic bodies according to the invention (solid lines 3, 4 and 24) show a small drop in specific resistance even at high voltage and a low voltage dependency at high temperature, compared with the composition outside the invention (dashed line 2).

As you can see from Fig. 2, changes to you logarithmic value of the specific resistance almost proportional to the applied voltage per Thickness unit. It can thus be used as a measure of the voltage dependence of the specific resistance a resistance-voltage coefficient can be calculated according to the following equation

Resistance-voltage coefficient% / V = 2.303 log (resistance at 50 V -resistance at 10V) _

The results are shown in Table 2, from which it can be seen that the dependence of the specific Resistance to voltage at high temperature is significantly improved by the addition of silicon will. The reason why the addition of silicon is limited to 0.2 to 15 mol% is that one

An amount less than 0.2 mole percent does not effectively improve stress dependency and An amount of more than 15 mole percent does not result in a good quality of the ceramic body.

On samples which corresponded to the above, but about 11.5 mm in diameter and about 2.5 mm Thickness, an electrode was called ohmic Contact attached. The sample was held in still air at about 25 ° C and an alternating voltage exposed to 60 Hz. The measured voltage-current characteristic at thermal equilibrium is in F i g. 3, samples Nn 2, 3, 4 and 24 containing 0, 1, 2 and 2 Mölpfözenl silicon, respectively. the end This figure shows that the ceramic body according to the invention (solid lines 3, 4 and 24) show a good voltage characteristic. Especially in the case of sample no. 4, which is a relatively contains a large proportion of silicon, even at an input voltage of more than 320 V there is no increase in the

Amperage can be seen even though it has the lowest initial resistance of 9.4 Ω.

Sample Nos. 1 and 3 were heated in a nitrogen atmosphere for 30 minutes at 600 G ^0. The resistance-temperature curve was measured before and after the heat treatment. The results are shown in FIG. 4, the strong curves representing the values before the treatment and the thin curves representing the values after the treatment. It can be seen from this figure that the ceramic bodies according to the invention are hardly influenced by the treatment at high temperature in an atmosphere other than air and that their resistance-temperature characteristic is little changed. There is therefore a very large selection of materials that can be used as electrodes.

The invention is only seen in the entirety of the features of claim 1.

Table 1 Composition (mole) SrCO ₃ CaCO ₃ TiO ₂ Ce Y MnCO ₃ SiO ₂ AI ₂ O ₃ sample
Mr BaCO ₃ 10 100 0.3 0.1 ^ _ IN I. 89.7 10 - 102 0.5 - 0.2 - - 1 89.5 10 - 102 0.5 - 0.2 1 - 2 89.5 10 - 102 0.5 - 0.2 2 - 3 89.5 10 - 100 0.6 - 0.25 - 4th 89.15 10 - 100 0.6 - 0.25 0.5 5 89.15 10 - 100 0.6 - 0.25 1 6th 89.15 10 - 100 0.6 - 0.25 2 - 7th 89.15 10 - 100 0.6 - 0.25 5 - 8th 89.15 10 - 100 0.6 - 0.25 10 - 9 89.15 10 - 100 0.65 - 0.275 - - 10 89.1 10 - 100 0.65 - 0.275 03 _ 11th 89.1 10 - 100 0.65 - 0.275 1 - 12th 89.1 10 - 100 0.65 - 0.275 2 - 13th 89.1 10 - 100 0.65 - 0.275 5 - 14th 89.1 10 - 100 0.65 - 0.275 10 - 15th 89.1 10 - 100 0.7 - 03 - - 16 89 10 - 100 0.7 - 0.3 1 - 17th 89 10 - 100 0.7 - 03 2 - 18th 89 10 - 100 0.7 - 03 5 - 19th 89 8th - 101 - 0.7 0.2 2 - 20th 91.1 8th - 101 - 0.75 0.2 2 - 21 91.05 8th - 101 - 0.8 0.2 2 - 22nd 91 8th - 101 - 0.85 0.2 2 - 23 90.95 8th - 101 - 0.85 02 2 0.1 24 9055 8 2 101 - 0.85 02 2 - 25th 88.7 8 2 101 - 0.85 02 2 0.1 26th 88.7 8 2 101 - 0.85 02 2 0.25 27 88.7 8th - 101 - 05 02 2 - 28 90.85 8th - 101 - 1.0 025 2 - 29 90.75 8th - 101 - 1.1 025 2 - 30th 90.65 8th - 101 - 1.2 025 2 - 31 90.55 8th - 101 - 1.1 03 2 - 32 90.6 8th - 101 - 03 2 - 33 90.6 8th - 101 - U 0.3 2 - 34 90.6 8th - 101 - 1.2 0.4 2 - 35 90.4 8th - 101 - U 0.4 2 - 36 903 8th - 101 13th 0.4 2 - 37 90.1 8th - 101 0.85 02 5 - 38 9055 8th - 101 - 0R5 02 7th - 39 9055 8th - 101 - 0.85 02 10 - 40 9055 8th - 101 0.85 02 12th 41 9055 8th - 101 0.85 02 15th 42 9055 43

Table 2

Sample no. More specific resistance Ratio of Contradicting Ω · cm Resistances at Tension 200 and 25 ° C coefficient 25 ⁰ C 200 ° C % / V 1 2.1 · 10 2.9 ■ 10 " 1.4 · 105 -17.5 2 1.6 ■ 102 5.0 10 ' 3.1 · ΙΟ ' -15.3 3 5.4 x 10 1.6 · 10 ' 2.86 · 105 -7.0 4th 3.6 · 10 6.5 · 10 « 1.8 · ΙΟ ' -3.5. 5 2.5 102 2.5 · 10 ⁷ 1.0 · 10 ' -6.4 6th i, 24 · \ Qi 4.6 x 10 " 3.7 IO ⁴ ^ 1.75 7th 1.4 · ΙΟ ' 1.13. 10 ' 8.1 x 10 " ^ 2.30 8th 7.6 ■ 10 5.25 · ΙΟ » 6.9 · 10 ⁴ ^ 2.25 q 6.8 x 10 1.3 106 1.9 · 10 ⁴ -2.23 10 1.16 · 102 1.0 · 106 8.7 ■ 10 ' ^ -2.02 Il 6.4 102 1.16 'I0 ⁸ 1.82 10 ' -5.75 12th 2.5 102 1.4 · 10 ' 5.7 IO ⁴ -2.02 iJ 5.8 iü ' 4.2 iü ^; i, i · iö * = ■ 2.04 14th i, 2 · 102 4.8 · 10 ⁶ 4.0 ⁴ - 2.30 15th 1.76 · 102 2.55 10 ' 1.45 · 105 -2.13 16 2.4 102 4.0 10 ' 1.65 · 105 -2.40 17th 8.0 102 5.8 10 ' 7.2 ⁴ • -7.7Ο 18th 3.8 102 1.9 10 ' 5.0 ⁴ ^ -2.2D 19th 2.8 102 1.4 · ΙΟ ' 5.0 · 10 ⁴ -2.10 20th 1.76 ² 2.45 ΙΟ ⁶ 1.4 · ΙΟ ⁴ -1.72 21 1.25 · 102 2.6 10 ' 2.14 · 105 -2.3 22nd 8.9 · 10 1.2 - 10 » 1.36 · 106 -3.5 23 7.8 · 10 i, 6 108 2.1 · ΙΟ ⁶ -3.8 24 3.6 · 10 7.2 10 ' 2.0 x 10 ^b -3.5 25th 5.8 · 10 5.8 · 10 ⁶ 1.0 · ΙΟ ' -2.2 26th 4.0 102 1.2 - 10 " 3.0- ΙΟ ⁶ -1.0 27 2.4 102 9.8 10 ' 4.1 · 105 -1.6 28 3.2 102 OK · 10 » 3.1 105 -1.85 29 1.62 102 9.3 ■ 10 ⁸ 5.7 ⁶ -1.6 30th 1.14 102 8.7 108 7.6 106 -1.3 31 1.39 ■ 102 1.53 x 10 " 1.1 ■ 10 ' -1.1 32 2.7 W 3.8 - 10 " 1.4 · ΙΟ ⁶ -1.0 33 5.76 · ΙΟ ² 6.9 108 1.2 ■ 106 -1.0 34 6.0 · 10 ² 1.2 - 10 " 2.0 · ΙΟ ⁶ -1.0 35 2.72 - 103 6.5 · 108 2.4 ■ 105 -0.9 36 1.5 103 4.8-108 3.2-105 -1.1 37 3.75 · 10 ^J. 7.9 · 10 ⁸ 2.1 ■ 105 -1.0 38 6.8 ³ 1.1 x 10 " 1.6-105 -0.9 39 7.6 · 10 1.45 10 " 1.9 ■ 10 ' -2.1 40 6.8 · 10 5.6 · ΙΟ » 8.2 ■ 106 -2.0 41 6.6 · 10 1.56 10 ' 2.36 - ΙΟ ' -1.9 42 1.08 102 2.38 · 10 ' 2.2 · 105 -1.9 43 1.37 102 3.3 ■ 10 ' 2.4 ■ 105 - 1.7 For this purpose 4 figures drawings

Claims (3)

Patent claims: 1. Semiconducting ceramic resistor with positive temperature coefficient of mainly Barium titanate with a content of - each in oxide form - at least 0.2 mol% silicon and at least 0.23 mol% of rare earths, bismuth and / or antimony, characterized in that, that the ceramic also - in oxide form - contains 0.13 to 0.45 mol% manganese, that the content of silicon is up to 15 mol% and that the content of rare earths, bismuth and / or antimony exceeds that of manganese by 0.1 to 1.2 mol% 2. Semiconducting ceramic resistor according to claim 1, characterized by an additive titanates other than barium titanate or from zirconates and / or stannates. 3. bisecting ceramic resistor according to claim 1 and 2, characterized by a Addition of not more than 03 percent AljOj.