JPH07302681A - Ceramic heater element - Google Patents

Abstract

PURPOSE:To provide a ceramic heater element of low cost and high performance. CONSTITUTION:A ceramic heater element comprises a heat generating part having a specific resistance of 1X10<-2>-5X10<0>OMEGAcm, and mainly comprising molybdenum silicide - aluminum oxide mixed material. As additive, at least one sort of ZrC, WC, TaC, TiC, NbC, HfC, and MoC is included in total quantity of 0.01-10% volume %.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a ceramic heating element.

[0002]

2. Description of the Related Art Conventionally, molybdenum disilicide having resistance to oxidation has been used as a material of a heating portion in a ceramic heating element, for example, a rapid temperature rising element for gas ignition. However, molybdenum disilicide showed a metallic electric conduction characteristic and had a resistance value of 3.5 times or more of room temperature at a high temperature of 1000 ° C. or more, which impeded rapid temperature rise.

Although SiC is added to prevent the above-mentioned drawbacks, if SiC is added, it becomes difficult to sinter, so firing by hot pressing is required. Therefore, not only the productivity of firing becomes low, but also the sintered body having extremely high hardness after firing has to be subjected to predetermined mechanical processing, for example, processing into an element shape, which makes it difficult to reduce the manufacturing cost. Was becoming.

Further, when SiC is added, since SiC reacts with impurities in the material of the element because it is a semiconductor, it is difficult to adjust the resistance value of the element, and the resistance changes with use. It is stable.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost, high-performance ceramic heating element which has alleviated the above drawbacks.

[0006]

The above objects are achieved by the present invention described in (1) to (12) below. (1) The heat generating part has a specific resistance of 1 × 10 ^{−2 to} 5 × 10 ⁰ Ωcm and contains a molybdenum silicide-aluminum oxide mixed material as a main component, and Zr, W, Ta, Ti, N as additives.
A ceramic heating element composed of a ceramic sintered body containing 0.01 to 10 volume% of at least one of b, Hf, and Mo carbides. (2) The ceramic heating element according to (1) above, which contains the additive in a total amount of 0.05 to 5% by volume. (3) When the vertical axis represents the ratio R of the specific resistance of the heating portion temperature of 1000 ° C. or more to the specific resistance of the heating portion temperature of 20 ° C. and the horizontal axis represents the element temperature T, the heating portion is a straight line of R = T / 1000. R
The ceramic heating element according to (1) or (2) above, which has a temperature coefficient of resistance in a region surrounded by a straight line of 3T / 1000. (4) The composition ratio of molybdenum silicide and aluminum oxide, which are the main components of the material of the heat generating portion, is 40/60 to 15 in volume ratio.
/ 85, The ceramic heating element according to any one of the above (1) to (3). (5) The ceramic heating element according to any one of (1) to (4), wherein the heating portion is supported by a ceramic insulating layer. (6) First and second high resistance conductive ceramic sintered bodies in which the heat generating portion is layered with a high resistance conductive ceramic material on at least a part of each surface of the electrically insulating ceramic sintered body layer. A layer and a connecting portion integrally formed with the first and second high resistance conductive ceramic sintered body layers by a high resistance conductive ceramic material, and in the heat generating portion, the first and second The ceramic heating element according to any one of (1) to (5) above, wherein a current path extending from one of the high resistance conductive ceramic sintered body layers to the other through the connecting portion is formed. (7) A low resistance is provided on at least a part of the same surface as the first and second high resistance conductive ceramic sintered body layers or on the surface of the first and second high resistance conductive ceramic sintered body layers. Formed of a conductive material, the first and second respectively
The ceramic heating element according to (6) above, which includes first and second lead layer layers electrically connected to the high-resistance conductive ceramic sintered body layer. (8) The ceramic heating element according to the above (7), wherein the first and second lead part layers are conductive ceramic sintered body layers formed of a low resistance conductive ceramic material. (9) The main components of the first and second lead layers are molybdenum silicide simple substance or molybdenum silicide-aluminum oxide mixed system, and the composition ratio of molybdenum silicide and aluminum oxide is 5/5 to 5 by volume. The ceramic heating element according to the above (8), which is 10/0. (10) The first and second high-resistance conductive ceramic sintered body layers are mainly composed of aluminum oxide or a molybdenum silicide-aluminum oxide mixed system, and the composition ratio of molybdenum silicide and aluminum oxide is volume. The ceramic heating element according to any one of (6) to (9), wherein the ratio is 0/10 to 2/8. (11) The ceramic heating element according to any one of (1) to (10), wherein the outer surface is covered with a heat-resistant and oxidation-resistant protective film that is chemically and thermally stable. (12) The ceramic heating element according to the above (11), wherein the protective film is formed of at least one of silica, alumina and chromia.

[0007]

[Operation and effect] By adding an appropriate amount of metal carbide to the molybdenum silicide-aluminum oxide mixed material, it becomes possible to add a semiconductor-like electric resistance-temperature characteristic and control the positive resistance temperature characteristic. In this case, it is desirable that the additive itself does not exhibit semiconductor-like behavior, but exhibits semiconductor-like behavior when added to the composition of the heating portion of the ceramic heating element. In other words, it suffices if control can be performed so that the positive temperature coefficient is reduced in the entire composition system. Further, in the present invention, as the metal oxide, ZrC, WC, TaC, TiC, Nb
Since at least one of C, HfC and MoC is used, firing can be performed without using hot pressing.

Therefore, the mechanical processing applied to the element can be performed in the stage of the green chip before firing.
It is extremely easy to machine and can be manufactured at low cost. This is particularly effective in machining a slit or the like, which is a void for stress relaxation required when increasing the capacity of the heating element.

[0009]

Specific Structure The specific structure of the present invention will be described in detail below.

[0010]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

In the ceramic heating element of the present invention, the heating portion has a molybdenum silicide-aluminum oxide mixed material as a main component, and Zr, W, Ta, Ti, N as additives.
It is composed of a ceramic sintered body containing at least one of b, Hf and Mo carbides. The above-mentioned carbide is usually ZrC, WC, TaC, TiC, Nb.
C, HfC and MoC are used.

The above-mentioned molybdenum silicide-aluminum oxide mixed material has a specific resistance in the sintered body of 1 × 10 ^-2 .
It is set in the range of 5 × 10 ⁰ Ωcm. This specific resistance is 1
When it is less than × 10 ^-2 , the resistance becomes too low to be used as a heating element, and when it exceeds 5 × 10 ⁰ Ωcm, the resistance becomes too high and the temperature does not rise to 1200 ° C or higher.

The composition ratio of molybdenum silicide and aluminum oxide, which are the main components of the material of the heat generating portion, is 40 / volume ratio.
It is preferably 60 to 15/85, and particularly 35/65 to 20/80. If the content of molybdenum silicide is less than 15% by volume, the resistance will be too high, and if it exceeds 40% by volume, the resistance will be too low and the calorific value will be extremely low. Molybdenum silicide and aluminum oxide exist as separate phases, and their average grain sizes are both 0.2 to
It is about 30 μm.

On the other hand, the additives ZrC, WC, Ta
The specific resistance of the sintered body of C, TiC, NbC, HfC and MoC is often about 10 ⁻⁶ Ωcm.

The total content of the above additives is 0.01-.
10% by volume, preferably 0.05 to 5% by volume, particularly preferably 0.1 to 3% by volume is desirable. If the added amount of the additive is less than 0.01% by volume, no effect is obtained and 10
This is because when the content exceeds the volume%, it is difficult to sufficiently densify it when firing is performed without using hot pressing.
These additives are usually present at grain boundaries or meeting points.

As the additive, SiC may be further added in the range of 0.01 to 2% by volume of the total amount of the material of the heat generating portion.

A binder and a solvent are added to the above raw materials,
The slurry for the heat generating part is adjusted by mixing, and the green sheet for the heat generating part is formed by using this slurry by the doctor blade method or the like. Hereinafter, the slurry for the heat generating portion may be referred to as a resistance slurry.

When the ceramic heating element of the present invention is used as a rapid temperature raising heating element for gas ignition or the like, its resistance temperature coefficient is m, and the resistance of the heating portion temperature is 1000 ° C. or more with respect to the resistance value of the heating portion at room temperature. When the ratio of the values is R and the element temperature is T, the following equation R = mT / 1000 is shown in the graph of FIG.
And the element temperature T on the horizontal axis, R = T / 1000
It is necessary to be within the region surrounded by the straight line of R and the straight line of R = 3T / 1000. By setting the temperature coefficient of resistance of the heat generating portion within the above range, it is possible to achieve a temperature rise from room temperature to 1000 ° C. within 5 seconds, and an element that does not overheat to 1600 ° C. or more. When the temperature coefficient of resistance of the heat generating portion deviates below the above range, heat generation exceeding 1600 ° C. occurs, and when it deviates upward, rapid heat generation is hindered.

The heating portion is preferably supported by the ceramic insulating layer.

The ceramic heating element of the present invention preferably has a structure as shown in FIG. 2, for example. This ceramic heating element includes an electrically insulating ceramic sintered body layer 1 and a first layer of electrically conductive ceramic material having a high resistance formed on at least a part of each of both surfaces of the electrically insulating ceramic sintered body layer 1. And second high resistance conductive ceramic sintered body layers 2a and 2b, and a connecting portion 2c integrally formed with the first and second high resistance conductive ceramic sintered body layers by a high resistance conductive ceramic material. And a heat generating portion 2 having a current path extending from one of the first and second high resistance conductive ceramics sintered body layers 2a, 2b to the other via the connecting portion 2c, and the first and second heat generating portions. 2. A low resistance conductive material on at least a part of the same surface as the high resistance conductive ceramic sintered body layers 2a, 2b or on the surfaces of the first and second high resistance conductive ceramic sintered body layers 2a, 2b. Formed by Has respectively a first and second first and second lead portions layers 3 and 4 which are connected high resistance conductive in the sintered ceramic layer electrically. The ceramic heating element also includes terminal electrodes 5, 6 connected to the first and second lead portion layers.

In the above structure, as is apparent from the figure, the rapid heating element of the present invention is preferably formed in a rectangular plate shape as a whole, and the tip of the end portion in the lengthwise direction is formed. The heat generating portion 2 is formed on the. In the present specification, the "heat generating portion" may include not only the resistor but also a part of the electrically insulating ceramic sintered body layer 1. That is, the heat-generating portion is a portion that substantially bears heat-generating action, and in the illustrated example, indicates the tip side from the tip surfaces of the lead layer layers 3 and 4. In these, the tip portion of the electrically insulating ceramic sintered body layer 1 is used. Is included.

The electrically insulating ceramic sintered body layer comprises an insulating first component which is a metal oxide, a metal silicide and /
Alternatively, it is formed of a ceramic mainly containing a conductive second component which is a metal carbide. In this case, only the insulating first component may be used, but it is preferable to further contain the conductive second component. This improves durability.

As the metal oxide, aluminum oxide,
At least one powder selected from zirconium oxide, chromium oxide, titanium oxide, tantalum oxide, magnesium aluminum oxide, mullite and the like is used.

As the metal silicide, at least one powder of molybdenum, tungsten and chromium silicide is used. As the metal carbide, at least one kind of powder of silicon and titanium carbide is used. Of the above, it is most preferable to use a silicide, especially molybdenum silicide, as the second component.

Of the above, it is particularly preferable to form the electrically insulating ceramic sintered body layer with a ceramic containing aluminum oxide and molybdenum silicide as main components. By making the heat generating portion and the main component the same, it is possible to improve the bonding between the heat generating portion and the electrically insulating ceramic sintered body layer.

The composition ratio of the insulating first component and the conductive second component in the electrically insulating ceramic sintered body layer 1 is 10: 0 to 8: 2 by volume, preferably 10: 0 to 9. 3: 0.
It is desirable to set to 7. When the conductive second component exceeds 20% by volume, the insulation due to the insulating first component breaks down and it becomes easier to have conductivity.

The slurry for the electrically insulating ceramic sintered body layer 1 is adjusted by adding a binder and a solvent to the above raw materials and mixing them. Hereinafter, this slurry may be referred to as an insulating slurry.

The first and second lead portion layers 3 and 4 are also an insulating first component which is a metal oxide and a metal silicide and / or a metal carbide, like the electrically insulating ceramic sintered body layer 1. It is formed of a ceramic containing a conductive second component as a main component. At this time, only the conductive second component may be used, but it is preferable to add the insulating second component in terms of durability and the like. As the metal oxide, metal silicide and metal carbide, the same ones as described above can be used. It is desirable to use aluminum oxide and molybdenum silicide in the first and second lead layers as in the case of the electrically insulating ceramic sintered body layer. By using the same material as the electrically insulating ceramic sintered body layer and the heat generating portion, the coupling between these and the first and second lead portion layers becomes particularly good.

The composition ratio of the insulating first component and the conductive second component in the first and second lead layers is 5: 5 by volume.
It is desirable to set it to ˜0: 10, preferably 5: 5 to 1: 9. When the content of the conductive second component is less than 50% by volume, heat generation in the lead layer becomes too large.

The slurry for the lead layer is adjusted by adding a binder and a solvent to the above raw materials and mixing them. Hereinafter, this slurry may be referred to as a conductive slurry.

The insulating first component and the conductive second component have grain sizes of about 1 to 50 μm and about 1 to 50 μm, respectively.

In some cases, the first and second lead portion layers may be layers formed by baking, spraying, plating, sputtering, etc., of a metal or alloy instead of the ceramic layers. Examples of metals that can be used include platinum,
As palladium and alloys, stainless steel, nickel-chromium-aluminum, cobalt, yttrium-based alloys Ni-Cr-Al-Y, Co-Cr-Al-Y, Ni-
Co-Cr-Al-Y and Ni-Cr are mentioned.

The terminal electrodes are made of palladium, silver, nickel, aluminum, solder or the like. In the case of palladium, silver and nickel, it is formed by baking, and in the case of aluminum, it is formed by thermal spraying.

The above ceramic heating element has a thickness of 100 to 2000 μm and a width of 200 to 500 μm.
It is desirable to set the length to 0 μm, preferably 800 to 3000 μm, and the length to 15 to 70 mm, preferably 25 to 50 mm.

When the thickness is less than the above range, the mechanical strength is weak, and when the thickness is more than the above range, the heat capacity becomes too large and the temperature rising rate becomes slow, and the thermal shock resistance decreases, and cracks are generated at the time of rapid temperature rising. Cause of. If the width is less than the above range, the mechanical strength is weak and handling becomes difficult.
The heat generation capacity becomes smaller. Further, when the oxidation of the conductor progresses after a long period of use, the ratio of the oxide layer is likely to increase, and the influence of the oxidation becomes stronger. On the other hand, when it exceeds the above range, the heat capacity becomes too large and the temperature rising rate becomes slow. Moreover, even if the heat dissipation area becomes large, the temperature rise becomes slow. Further, the thermal shock resistance is lowered, which causes a crack to occur when the temperature is rapidly raised.

If the length of the element is less than the above range, it becomes difficult to install the terminal electrode sufficiently apart from the heat generating portion, and the temperature of the terminal electrode portion becomes high.
On the other hand, when the length exceeds the above range, it becomes vulnerable to mechanical shock and the like, and it becomes difficult to handle.

The electrically insulating ceramic sintered body layer 1 and the first and second high resistance conductive ceramic sintered body layers 2
It is desirable that the thicknesses of a and 2b are both set in the range of 1 to 1000 μm, preferably 10 to 500 μm. 1
If it is less than μm, it has no mechanical strength, and it tends to cause through holes and the like, which easily causes an electrical short circuit.
On the other hand, when it exceeds 1000 μm, the heat capacity becomes large,
At the same time that the temperature rising rate becomes slower, the element is more likely to be destroyed by the thermal shock caused by the sudden temperature rise.

The total thickness of the heat generating portion is 100 to 200.
It is desirable to set it in the range of 0 μm, preferably 500 to 1000 μm. If it is less than 100 μm, it has no mechanical strength and cannot be used. In addition, if it is used for a long time, it reacts with the oxide layer generated in the conductor, and the insulation deterioration easily occurs. On the other hand, if it exceeds 2000 μm, the heat capacity becomes too large, it takes time to raise the temperature, and the thermal shock resistance also decreases. Furthermore, in terms of heat generation characteristics,
It is desirable that the connecting portion 2c of the heat generating portion should be 200 to 2000 μm on the tip side of the electrically insulating ceramic sintered body layer. The first and second high resistance conductive ceramic sintered body layers 2a, 2b are formed on the electrically insulating ceramic sintered body layer 1 with a minimum of 100 μm, particularly a minimum of 500 μm, and a maximum of the maximum electrically insulating ceramic sintered body layer 1. It is desirable to exist in length. With such a length, the soaking area of the heat generating portion is expanded, the occurrence of cracks due to repeated temperature rise is reduced, and the thermal shock resistance and durability are improved.

The thickness of the first and second lead portion layers 3 and 4 is about 1 to 1000 μm.

Although not shown, it is preferable that the outer surface of the ceramic heating element is covered with a chemically and thermally stable heat-resistant and oxidation-resistant protective film.

The protective film is preferably formed of one or more of silica, alumina and chromia.
The protective film is preferably formed of silica. The thickness of this protective film is 0.1-10.
It is about 0 μm. Then, this protective film can be formed by an oxidation treatment method, a method of dipping in the metal solution, a sol-gel method, a coating method, or the like. Among the oxidation treatment methods, the method of forming silica on the surface of the element by energizing the element in an oxidizing atmosphere such as air to generate heat at a temperature higher than that in normal use is most preferable.

In such a ceramic heating element, especially in a ceramic rapid heating element, if the size is increased in order to increase the heat capacity, the thermal expansion due to the rapid heating causes cracks or breakage in the heating portion. There was a fear. Such a problem becomes remarkable particularly when using molybdenum silicide having a large coefficient of thermal expansion.

Therefore, in the present invention, the stress caused by the thermal expansion is relaxed by improving the structure, and the above-mentioned cracks and breakages are suppressed. That is, in the ceramic heat generating element of the present invention, the heat generating portion is provided with a stress relaxation void such as a slit or a minute opening to substantially divide the heat generating portion and suppress the stress of each portion, thereby generating heat. It is preferable to prevent cracking or destruction of the entire part.

Next, a method of manufacturing the ceramic heating element according to the present invention will be described. In the following description, the manufacture of the ceramic heating element having the structure shown in FIG. 2 will be described.

In this manufacturing, first, raw materials for the electrically insulating ceramic sintered body layer, the heat generating portion and the first and second lead portion layers are prepared.

This preparation was carried out by using a powder of an insulating first component (hereinafter, aluminum oxide, which is the main component of the heat generating portion, may also be referred to as an insulating first component) and a conductive second component (hereinafter
Molybdenum silicide, which is the main component of the heat generating portion, may also be referred to as the conductive second component), powder for the electrically insulating ceramic sintered body layer, the heat generating portion and the first and second lead portion layers, It is carried out by measuring the above composition ratios and adding thereto the additives such as the metal carbide, the binder and the solvent as described above. In the following description, aluminum oxide, which is the main component of the heat generating portion, may be referred to as an insulating first component, and molybdenum disilicide may be referred to as a conductive second component.

The prepared materials are mixed by, for example, a ball mill to obtain the above-mentioned insulating slurry, resistance slurry and conductive slurry. Mixing time is, for example, 3
It may be about 24 hours. Each green sheet is formed using these slurries.

After that, the cross section of each green sheet is shown in FIG.
Are laminated so as to have the structure of. This stack has a pressure of 5
It is carried out by thermocompression bonding under the conditions of 0 to 2000 kg / cm ² and a temperature of 50 to 150 ° C.

After that, each element is cut into strips by a cutter. In this case, at most, four sides of the rectangle may be cut.

After the cutting, binder removal processing and firing are performed. The binder removal processing is desirably performed under the following conditions, for example.

Rate of temperature rise: 6 to 300 ° C./hour, especially 30
~ 120 ° C / hour Holding temperature: 900-1100 ° C /, especially 950-105
0 ° C. Holding time: 1 to 24 hours, especially 5 to 20 hours Atmosphere: Air, nitrogen gas, argon gas, nitrogen gas −
Hydrogen-steam

The firing is preferably performed under the following conditions, for example.

Temperature rising rate: 300 to 2000 ° C./hour, especially 500 to 1000 ° C./hour Holding temperature: 1400 to 1850 ° C. /, especially 1700 to 1
800 ° C. Holding time: 0.5 to 3 hours, especially 1 to 2 hours Cooling rate: 300 to 2000 ° C./hour, especially 500 to 1
000 ° C / hour

The firing atmosphere may be vacuum, argon gas, helium gas, hydrogen gas or the like.

Next, silver or the like is baked at predetermined positions on the surfaces of the first and second lead layers to form terminal electrodes, and the manufacture of the ceramic heating element is completed. Further, the lead wire may be electrically connected and fixed to the socket.

The protective layer is formed on the surface of the sintered body of the element obtained as described above. This protective film is formed by energizing the device in an oxidizing atmosphere to generate heat at a high temperature. The protective film is preferably formed at a temperature higher than the temperature in normal use.
For example, when the temperature in a normal use state is 1300 ° C., it is desirable to set the temperature higher than this, especially 1400 ° C. or higher. Therefore, it is desirable to determine the addition of the metal carbide in the heat generating part in consideration of this heat generating temperature.

In addition to the above, the protective film is formed by immersing it in a dispersion liquid in which the coating material is dispersed, or in a metal alkoxide or an alkoxide solution in which the coating material is dispersed, or when the coating material is silica. It is also possible to apply a silicon resin to the surface of the sintered body and bake it. When the protective film is formed by immersion in the dispersion liquid as described above, the terminal electrode is formed after the protective film is formed.

The rapid heating element of the present invention manufactured as described above is used for a gas igniter or the like, and its driving voltage is
For example, about 12V to 400V of the car battery is applied.

[0059]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

With respect to the mixture having a volume ratio of MoSi ₂ / Al ₂ O ₃ = 3/7, TiC was used for Samples 1 to 8 in a volume ratio of 0,0.001,0.01,0.1,1,5. , 1
0,15 was added, and a total amount of 100 g was put in a 1-liter alumina pot, and 0.5 liter of alumina balls having a diameter of 5 mm was put therein, and wet-mixed in ethanol for 24 hours. The average particle size of the raw material used was 0.5 μm.

After mixing, the mixture was placed in a heat resistant polybat, dried in air at 100 ° C., and further thoroughly mixed in an alumina mortar.

Then, the above mixture is put into a rod-shaped mold,
It was molded at a molding pressure of 1 t / cm ² .

After molding, this molded body was fired at 1800 ° C. in an argon gas atmosphere using a graphite heater. 180
The temperature was kept at 0 ° C. for 2 hours. Cooling was performed by natural cooling.

FIG. 10 shows the sintered body obtained as described above.
It processed with the diamond cutter as shown in. The thickness was 1 mm.

Then, the above processed product was subjected to 1400 in air.
Heat treatment was performed at 1 ° C. for 1 hour to form a silica protective film on the surface.

Finally, the silica film of the conductive portion was removed by sandpaper, an electrode P of Mo30-Ni70 (weight ratio) was baked there, and a Ni-coated copper wire was welded to the electrode P to obtain a sample No. of the element. .1-8 was formed.

With respect to the obtained sample, the resistance ratio R, the heating time to the device temperature of 1000 ° C., and the saturation temperature were determined. The resistance ratio R is a resistance value Rr at room temperature (unit: Ω) and 1
The resistance value R ₁₁₀₀ (unit: Ω) at 100 ° C. was measured with a digital multimeter manufactured by Advantest, and the resistance value R ₁₁₀₀ was divided by the resistance value Rr. The temperature measurement was performed using a two-color thermometer manufactured by Chino. The results are shown in Table 1.

[0068]

[Table 1]

As can be seen from Table 1, TiC is 0.01
When added in an amount of 10 to 10% by volume, R is in the range of 3 to 1,
It is possible to rapidly raise the temperature to 1000 ° C. for 3 seconds or less, and obtain an element in which the heat generation temperature is limited to 1600 ° C. or less.

Next, by changing the additive species to TiC, ZrC,
A device sample was prepared in the same manner as above except that WC, TaC, NbC, HfC and MoC were added in the amounts shown in Table 2, and the resistance ratio R was measured. The results are shown in Table 2.

[0071]

[Table 2]

As can be seen from this table, T as an additive species
ZrC, WC, TaC, NbC, HfC instead of iC
It can be seen that also when MoC and MoC are used, the same characteristics as described above can be obtained.

Next, an element having the structure shown in FIG.
An exothermic test was conducted.

In the fabrication of the device, Al ₂ O _{3 is} commonly used as the main component of the ceramics of the electrically insulating ceramic sintered body layer, the heat generating portion and the first and second lead portion layers.
And MoSi ₂ were used and blended as follows. The same material as the sample No. 5 was used as the material of the heat generating part. Therefore, 1% by volume of TiC was added.

Al ₂ O ₃ MoSi ₂ Electrically Insulative Ceramic Sintered Body Layer 100% by Volume 0% by Volume (Insulating Layer) Heating Section (Resistance Layer) 70% by Volume 30% by Volume First and Second Lead Section Layers (Conductor) ) 20% by volume 80% by volume Average particle size of powder 0.4 μm 2 μm Binder Methacrylic binder Solvent Toluene

The above was mixed in a ball mill for 24 hours to prepare slurries, and these were used to prepare a sheet by the doctor blade method. Further, a sheet (not including a terminal electrode) was formed into a sheet as shown in FIG. Each sheet was cut into a predetermined size. Further, stack each sheet in a mold, and
Treated under the conditions of 20 ° C. and 500 kg / cm ² , the insulating layer,
The respective parts of the resistance layer and the conductive layer were adhered to obtain a molded product having the structure of FIG.

Next, the molded body was subjected to binder removal treatment in a nitrogen gas atmosphere in an alumina tubular furnace. The temperature was raised to 1000 ° C. at a temperature rising rate of 1 ° C./min, and the temperature was maintained for 1 hour, and then naturally cooled.

Next, firing was performed in an argon gas atmosphere. In this firing, first, the temperature was raised from room temperature to 1400 ° C. in 1 hour, and then from 1400 ° C. to 1800 ° C. in 30 minutes. The temperature was maintained for 1 hour, and then the material was cooled at a rate of 300 ° C./minute and fired. However, it was naturally cooled below 800 ° C.

Further, silicone is applied to the entire element,
Heat treatment in air at 1400 ° C for 1 hour to a thickness of about 1 μm
A silica protective film which is a dense SiO ₂ film was formed. After this, sandblast the protective film on the terminal electrode,
A silver electrode was baked on this portion to make a sample of a rapid heating element. The element dimensions are 2.0 (width) × 25.0 (length) × 1.0 (thickness) mm.

An exothermic test was conducted on the above samples under the following conditions. Initial resistance value: 5Ω Applied voltage: 20V Load: 27W

The heat generation temperature and the like of both the samples of Examples and Comparative Examples reached 1000 ° C. in 2 seconds after the start of energization, reached the maximum value (saturation temperature) of 1480 ° C. in 4 seconds, and 20 after the stop of energization.
The temperature was lowered to about 90 ° C. in seconds. Further, the temperature coefficient of resistance of the element is a straight line indicated by R = T / 1000, and R = 3T /
It was within the area surrounded by the straight line indicated by 1000.

[Brief description of drawings]

FIG. 1 is a graph for explaining a preferable temperature coefficient of resistance in a ceramic heating element of the present invention.

FIG. 2 is a perspective view showing an example of the overall structure of the ceramic heating element of the present invention.

FIG. 3 is a plan view showing a structure of a sample ceramic heating element formed to confirm the effects of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electrically insulating ceramics sintered body layer 2 Heating parts 2a, 2b 1st and 2nd high resistance conductive ceramics sintered body layer 2c Connection part 3, 4 1st and 2nd lead part layers 5, 6 Terminal electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Miki 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Masatada Yodogawa 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Within the corporation

Claims (12)

[Claims] 1. The heat generating portion is 1 × 10 ^{−2 to} 5 × 10 ⁰ Ωcm.
Of which the main component is a molybdenum silicide-aluminum oxide mixed system material, and Zr, W, Ta, and
A ceramic heating element constituted by a ceramic sintered body containing at least one kind of carbides of Ti, Nb, Hf and Mo in a total amount of 0.01 to 10% by volume. 2. The total amount of the additives is 0.05 to 5% by volume.
The ceramic heating element according to claim 1, which contains. 3. When the vertical axis represents the ratio R of the specific resistance of the heating portion temperature of 1000 ° C. or more to the specific resistance of the heating portion temperature of 20 ° C. and the horizontal axis represents the element temperature T, R of the heating portion is T = T / 1000. The ceramic heating element according to claim 1 or 2, which has a temperature coefficient of resistance in a region surrounded by a straight line and a straight line of R = 3T / 1000. 4. The composition ratio of molybdenum silicide and aluminum oxide, which are the main components of the material of the heat generating portion, is 40/6 in volume ratio.
The ceramic heating element according to any one of claims 1 to 3, which is 0 to 15/85. 5. The ceramic heating element according to claim 1, wherein the heating portion is supported by a ceramic insulating layer. 6. The first and second high resistance conductive ceramic calcinations wherein the heat generating portion is layered with a high resistance conductive ceramic material on at least a part of each of both surfaces of the electrically insulating ceramic sintered body layer. And a connecting part integrally formed with the first and second high resistance conductive ceramics sintered body layers by a high resistance conductive ceramic material. 6. The ceramic heating element according to claim 1, wherein a current path extending from one of the second high resistance conductive ceramic sintered body layers to the other through the connecting portion is formed. 7. A low-resistivity layer is formed on the same surface as the first and second high resistance conductive ceramics sintered body layers or at least a part of the surface of the first and second high resistance conductive ceramics sintered body layers. 7. The ceramic heating element according to claim 6, further comprising first and second lead portion layers formed of a resistive conductive material and electrically connected to the first and second high resistance conductive ceramic sintered body layers, respectively. . 8. The ceramic heating element according to claim 7, wherein the first and second lead portion layers are conductive ceramic sintered body layers formed of a low resistance conductive ceramic material. 9. The first and second lead portion layers are mainly composed of molybdenum silicide or molybdenum silicide.
It is an aluminum oxide mixed system, and the composition ratio of molybdenum silicide and aluminum oxide is 5/5 to 10 / by volume.
The ceramic heating element according to claim 8, which is 0. 10. The first and second high resistance conductive ceramics sintered body layers, the main component of which is aluminum oxide simple substance or a molybdenum silicide-aluminum oxide mixed system, and the composition ratio of molybdenum silicide and aluminum oxide. And a volume ratio of 0/10 to 2/8.
Any of the ceramic heating element. 11. The ceramic heating element according to claim 1, wherein the outer surface is covered with a chemically and thermally stable heat-resistant and oxidation-resistant protective film. 12. The ceramic heating element according to claim 11, wherein the protective film is formed of at least one of silica, alumina and chromia.