JPH0380502A - Thermistor material and thermistor element - Google Patents

Abstract

PURPOSE:To enhance high temperature stability by incorporating silicon carbide and boron carbide, and one or more types of oxides of aluminum, silicon and group 2A element as conductive path forming substances in such a manner that the content of the silicon carbide is specific amount or less, and composing it of a sintered material containing a specific amount of boride of group 4A element. CONSTITUTION:Matrix substance containing silicon carbide and boron carbide, one or more types of oxides of aluminum, silicon and group 2A element is contained as conductive path forming substance. The content of the silicon carbide is 1.24 or less to that of the matrix substance by volume, and composed of sintered material containing 0.01-10wt.% of boride of group 4A element in terms of group 4A element. As the oxide of the matrix substance, Al2O3, SiO2, MgO, CaO, SrO, BaO, etc., are used. The boron carbide in the sintered material is represented by B4C. Thus, high temperature stability, easy control of resistance value, easy glass sealing, and high chip processing can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Prior Art> The present invention relates to a thermistor material and a thermistor element that are effective when applied to a thermistor element having negative resistance temperature characteristics for high temperatures.

Prior art and its problems A thermistor is a temperature sensor that utilizes the temperature dependence of the electrical resistance of a temperature-sensitive resistor, and is widely used for temperature measurement, temperature control, etc. Particularly for high-temperature applications, they are used, for example, in automobile exhaust gas temperature detection sensors, oil and gas combustion control sensors, and the like.

The material of the temperature-sensitive resistor of the conventional high-temperature thermistor element, that is, the thermistor material, is fluorite type (Zr0l-
zirconia type such as CaO-Y2O2-Nd202-ThO), spinel type (MgO-NiO-AjtOs-Cr
zOa-FezOs etc; Co0-Mn0-Ni0-
AJzOs-CrzOs-CaSiOs etc.; Ni0z
-Coo-Affi203 etc.; Mg0-Ajz03-
CrzOa-LaCrOz, etc.) Corundum type (Ag2
01-Cr203-Mn02-CaO-3iO, etc.)
In addition, sintered bodies of complex oxides such as perovskite type and rutile type are used.

Since these materials are composite oxide sintered bodies, they do not change significantly over time due to factors such as +) having a crystal transformation point below 1000°C, and ++) forming barriers between particles. Many are stable. In particular, since zirconia is an oxygen ion conductor, it undergoes redox reactions and changes significantly over time.

Furthermore, since it is a multi-component composite oxide, there are large variations in properties such as resistance value.

Furthermore, in these devices, the value of the thermistor constant B is large, and the temperature coefficient of resistance of the thermistor is too large, making it impossible to provide a thermistor that covers a wide temperature range from room temperature to high temperature. In particular, it could not withstand use at temperatures above 500°C.

On the other hand, various thermistor elements whose main components are silicon carbide or boron carbide are known.

For example, Japanese Patent Publication No. 42-19061 describes a thermistor element in which a trace amount of a group 3B or 5B element is added to single crystal silicon carbide as a p-type or n-type impurity.

However, since this method involves the production of a single crystal, productivity is low and manufacturing costs are high.

Further, although this material exhibits a very stable electrical resistance value at high temperatures, when the device is used in the atmosphere at high temperatures, it is subject to surface oxidation, particularly at temperatures above 400°C. Therefore, a protective film is required. As a method for forming this protective film, sealing of the chip with glass is preferable since it is the easiest to manufacture.

However, in the above-mentioned thermistor element, silicon carbide tends to foam due to reaction with glass in the step of glass sealing, and glass sealing cannot be performed.

Further, US Pat. No. 4,086,559 describes a thermistor element using thermally decomposed polycrystalline equiaxed silicon carbide to which p-type impurities are added at 0.7 vol. % or less.

Also, U.S. Patent Nos. 4,359,372 and 44,245
No. 07 describes a sputter thin film thermistor element made of silicon carbide or boron carbide containing a small amount of impurities.

However, these thin-film type thermistors have low productivity and high manufacturing costs like single crystal thermistors. Furthermore, glass sealing cannot be performed.

Therefore, in the latter sputtered thin film, glass is vapor-deposited as a protective film to suppress foaming, but in this case, productivity is further reduced.

On the other hand, composite sintered bodies of oxide and non-oxide materials are also known. This material has higher productivity than single crystals or thin films.

As such a composite sintered body, the following composite sintered body mainly composed of silicon carbide is known.

(A) Silicon carbide as the main component, Be, BeO%B,
B203, BN, B4 C in terms of element 2
Polycrystalline silicon carbide sintered body containing 0 wt% or less (U.S. Pat. No. 4,467,309) (B) 0.5 to 10 wt of one or more types of aluminum compounds such as aluminum and aluminum oxide to silicon carbide
% of polycrystalline sintered body (Japanese Unexamined Patent Publication No. 60-49607).

(C) Silicon carbide sintered body made by thermally diffusing B into silicon carbide and adding a small amount of B (Japanese Patent Publication No. 60-52562) However, since these have a high SiC content, they are sealed with glass due to foaming as described above. It is difficult to stop.

Furthermore, if silicon carbide is used as the main material, it is difficult to process, and cutting into a thermistor chip is difficult.

Furthermore, there is a drawback that the value of B increases to 10,0OOK or more, and the temperature coefficient of the thermistor becomes too large to cover a wide temperature range.

Furthermore, when examining the relationship between the composition ratio and resistivity (ρ) of the thermistor materials, it is found that with these materials, ρ changes rapidly even with a slight change in the composition ratio, making it difficult to control the resistance. Furthermore, JP-A-55-140201 discloses that SiC is the main component, 2 to 15 wt% Rung and 20
Thick film thermistors containing ~50 wt% glass have been described. However, in this case as well, the powdered SiC and glass foam violently during the printing and firing steps, and it is very difficult to control this.

Furthermore, JP-A-60-37101 discloses a sintered material made of silicon carbide, silicon nitride, and semiconductor oxides such as zirconium oxide, nickel oxide, zinc oxide, cobalt oxide, chromium oxide, and titanium oxide; Furthermore, °
Aluminum oxide, zirconium oxide, 3A, 4A,
Nitride, boride, carbide of group 5A and 6A transition elements,
A material made by sintering a composite material of silicide or silicide is described.

Products made by sintering silicon carbide, silicon nitride, and semiconductor oxide composite materials: 1) The semiconductor oxide is easily reduced during firing, making it difficult to control electrical resistance, and is susceptible to the influence of the operating atmosphere due to oxygen defects, etc. Easy to accept.

11) Compared to silicon carbide and silicon nitride, semiconductor oxides have a lower firing temperature, so the firing conditions for composite materials are difficult.

As described in ri)+), when a semiconductor oxide is reduced, its electrical resistance value decreases significantly, so its specific resistance value is 5.
It is difficult to make it more than several tens of cm at 00°C. Therefore, in order to make an element of 10'' to 10'Ω commonly used in thermistor circuits, the distance between the electrodes must be long, which causes problems in miniaturization and high response.

In addition, nitrides, borides, carbides, and silicides of group 3A, 4A, 5A, and 6A transition elements are electrically close to good conductors, so when combined with aluminum oxide and zirconium oxide, the composition is small. The electrical resistance value changes rapidly due to a change in the ratio, and it is difficult to control it.

Further, the above-mentioned Japanese Patent Application Laid-Open No. 60-37101 describes some specific compositions of thermistor materials.
Among these, 36wt%S i C-”7 described in this publication
wt%B4C-55wt%Co O-2wt%Li
In No. 20, Li is easily diffused by voltage application, and co
is unstable at around 500°C. Furthermore, with these compositions, the resistance is less than 60 Ωcm at 500° C., and therefore, the electrodes cannot be spaced from each other, making it impossible to reduce the size. Furthermore, 65wt
%S i C-35, wt% A422 0.11 parts by weight with 9 parts by weight of T i O2 added, and 3-7
wt%SiC-20wt%A A 20335wt%T
In iO2-8wt%T a 20 s, T i O2 is contained in an amount larger than 0.5 in volume ratio of SiC, so T
iOt is reduced by SiC and the firing atmosphere to become a conductor, but its resistance is difficult to control, and the stability of the resistance value at 500°C is affected. In addition, specific examples of the sintered bodies described in the same publication include 5iC5S i3N4
, Aff□03. One or more types of ZrO2 and N i O
, ZnO, Coo, Crz 0sTi○2, but these metal oxide semiconductors are easily reduced by carbides, are weak in the atmosphere, have a low electrical resistance value of the element, and are 500' It has drawbacks in some respects, such as the fact that the valence is likely to change at C or higher.

Therefore, it is stable even when used at high temperatures, especially at temperatures of 400 to 800'C, and the resistance value is easy to control.
Moreover, as a thermistor material that can be easily sealed with glass,
The present inventors first included silicon carbide and/or boron carbide as a conductive path forming material, and a matrix material containing one or more of aluminum, silicon, and oxides of group 2A elements, and A thermistor material composed of a sintered body whose content is 1.24 or less by volume with respect to the content of the matrix material has been proposed (Japanese Patent Application Laid-Open No. 64-64202).

However, in the future, chip processability is still insufficient, chipping occurs during chip processing, and
The durability of diamond grinding wheels for processing is low.

<Problems to be Solved by the Invention> The purpose of the present invention is to provide a material that is stable even when used at high temperatures, particularly at temperatures of 400 to 800°C, whose resistance value can be easily controlled, and which can be easily sealed with glass. The object of the present invention is to provide a thermistor material with high chip processability and a thermistor element with excellent characteristics by applying this material.

〈Means for solving problems〉 Such objects are achieved by the invention described below.

That is, the present invention contains silicon carbide and/or boron carbide as a conductive path forming material, and a matrix material containing one or more of aluminum, silicon, and oxides of group 2A elements, and the content of silicon carbide is The content of the matrix substance is 1.24 or less in volume ratio, and further 0.01 to 10 wt% in terms of group 4A elements.
This thermistor element has a thermistor material characterized by being composed of a sintered body containing a boride of a Group 4A element, and a thermistor chip formed from the thermistor material.

<Function> The improvement in chip processability in the present invention is achieved by
Unlike Publication No. -64202, this is achieved by intentionally adding a boride of a group 4A element to the sintered body raw material, or by generating a boride of a group 4A element during sintering.

In addition, in sample No. 807.808 of Example 8 of JP-A-64-64202, 0.2 wt% of T 1
An example of sintering with the addition of ZrO2 and ZrO2 is shown, but under these conditions TiBg and ZrBg do not form.

<Specific structure of the invention> Hereinafter, a specific configuration of the present invention will be explained in detail.

The thermistor material of the present invention is composed of a sintered body containing silicon carbide and/or boron carbide as a conductive path forming material and an oxide matrix material.

The content of silicon carbide is 1.24 or less in volume ratio to the content of the matrix material.

This is because if this volume ratio exceeds 1.24, the resistance value decreases, and foaming occurs in the glass sealing process described below, making it difficult to form a device by glass sealing.

Note that the volume ratio of silicon carbide/matrix material is O-1
, 24, the quantitative ratio of silicon carbide and boron carbide is 1:
Various quantitative ratios from 0 to O:1 are possible.

In addition, the volume ratio of silicon carbide, boron carbide, and matrix material can be determined by mirror-finishing the cut surface of the sintered body, observing it with an electron microscope, calculating the area ratio of each component, and using this as the volume ratio. good.

The matrix material is a sintered body of one or more of oxides of Aj2, Sl and group 2A elements.

By using such an oxide sintered body as the matrix material, foaming during glass sealing etc. is reduced.

Such oxides include aluminum oxide (Aβ2
03 In particular, it may be α-Aβ203). Alternatively, silicon oxide (SiO2) or even aluminum oxide-silicon oxide in various quantitative ratios may be used. By using silicon oxide, cutting workability is improved and chipping becomes easier. Moreover, instead of or in addition to these, one or more oxides of Group 2A elements may be used.

By containing an oxide of a Group 2A element, the electrical resistance value can be easily controlled, and positional variations in the electrical resistance value that occur within the sintered wafer are also reduced.

Also, cutting processability becomes easier.

Group 2A elements (Be, Mg%Ca%Sr.

As the oxide of Ba), magnesium oxide (MgO)
Particularly preferred are calcium oxide (Cab), strontium oxide (SrO), and barium oxide (Bad).

The amount of the oxide of the Group 2A element may be appropriately determined within the range of 0 to 100% of the matrix material depending on the desired electrical resistance value. Furthermore, the matrix material is AI
In addition to one or more oxides of l, Si and group 2A elements,
It may contain one or more oxides of Group 4A elements.

By containing an oxide of a group 4A element, the electrical resistance value can be easily controlled, its variation within the sintered body is reduced, and cutting workability is also improved.

As oxides of group 4A elements (Ti, Zr, Hf), titanium oxide (TiO2), zirconium oxide (ZrO2)
is preferred.

The amount of oxides of these Group 4A elements is 0.5 or less, especially 0.3 in volume ratio to the content of silicon carbide and boron carbide.
It is as follows.

This is because when the volume ratio exceeds 0.5, the oxides of group 4A elements are reduced by SiC and B4C during firing and become conductive, and SiC%84C does not become the main material for forming conductive paths, resulting in high temperatures. This is because the thermistor characteristics and its stability deteriorate.

Specific examples of oxide sintered bodies that form such matrix materials include α-AI2*Os, 3102, mullite (3AjtOa・2SiO2), steatite (
MgO・SiO□) Forsterite (2MgO・
5in2) Zircon (ZrO1sio□) Porcelain (
SiO□・Aj, 0. ), magnesia (MgO), Aj
20a-CaOA1203-TiOa, Ba(lSiO
z, etc., “Engineering Properties
of CeramicsDatabook to
Guide Materials 5electi
on for Structural Applic
ations ” Battele Memor
ial Institute Columbus L
aboratries P445-P447, P2S
5, P469, P472, and the composite oxides described in P479 to P480.

The chemical formulas of these oxide sintered bodies are shown in parentheses, but the stoichiometric composition may be slightly different. In addition, the average grain size is usually 0.1 to 250 1. In particular, O is in the range of 1 to 10 μm.

Silicon carbide in the sintered body is represented by the chemical formula SiC, and the stoichiometric composition may be slightly different. In addition, the average grain size is usually 0.1~
It is in the range of 15 μm.

Boron carbide in the sintered body is represented by the chemical formula 84C, and its stoichiometric composition may be slightly different. In addition, the average particle size is usually 0.1 to 15 μm.
within the range of

In the present invention, boron carbide, silicon carbide, or boron carbide and silicon carbide form a conductive path in a matrix material to exhibit thermistor characteristics.

The conductive path formed from these is stable at high temperatures of 400° C. or higher and has good thermistor characteristics.

Next, the case where aluminum oxide (α-A42gO-) is applied to the oxide sintered body of the matrix material will be described in more detail. In this case, the composition is expressed in wt% obtained by chemically analyzing the above sintered body.

The contents of aluminum oxide, silicon carbide, and boron carbide were respectively x in order at x + y + z = 100 wt%.
When expressed as wt%, ywt%, and zwt%, the composition of aluminum oxide, silicon carbide, and boron carbide (x, y+
z) is shown in Figure 1, in the ternary composition diagram A (100, O, O), B (0, O, Zoo) C (
50,50,O) and does not include point A or point B. In this case, preferably
D (95,0,5)E (5,0,95)C(5
0,50,O)F (95,5,O), more preferably D (95,0,5)G
(50,0,50) C(50,50,O), F (
95,5,O), particularly preferably D(95,0,5)H(80,0,20)I
(65,35,O), F (95,5,O) provides more favorable results.

This composition range is defined as A (
100, O, O) point, that is, 100 wt% of aluminum oxide or matrix material, the resistance is high even at high temperatures, and when the B (0,0,100) point, that is, 100 wt% of boron carbide, it is difficult to form a sintered body. This is because, below the BC line, the B constant becomes large when used as a thermistor element, making it difficult to form a sintered body.

When it becomes below the DF line, B4C and/or Si
Due to the effect of C addition, a desired resistance value can be obtained, and when the resistance value is equal to or higher than the EC line, sinterability is improved and a good thermistor chip can be obtained.

Then, the amount of Al2zOs exceeds the GC line and the amount of Al2zOs is 50w.
When the content is t% or more, the sinterability becomes even better.

In such cases, one of the effects of adding B, C and/or SiC is to reduce the resistance of the 8β203 or matrix material. The effect of this resistance reduction is expressed within the region surrounded by DGCF, and within this region B
As the amount of 4C and/or SiC increases, the resistance value gradually decreases. However, once the GC line is exceeded, the resistance change is saturated and the resistance value hardly decreases.

Therefore, in the area surrounded by the GEC, it can normally be used as a thermistor, but depending on the raw material used, the resistance value may be too low to be used as a thermistor. Therefore, it is not restricted by raw materials,
In particular, it is preferable that the resistance value be equal to or higher than the GC line, since the resistance value can be controlled to a desired value by adjusting the amount of addition.

To be more specific, the raw material SiC contains O, Afi, Fe, Ti, etc. in addition to free C and Si, but the SiC content is 99% or more and is used within the area surrounded by GCE. It is possible. However, if the purity is less than the above range, the resistance value becomes small below the GC line.

In addition, raw material B4C has O. N, Fe, etc. are contained as impurities, but if the purity is about 99 wt% or more, it will be 104
It has a saturation resistance value of Ωcm or more and can be used within the area surrounded by GEC, but if the purity is less than the above, it will not be GC.
The resistance value becomes smaller below the line.

Note that the area surrounded by this DHIF is more preferably J (90, 0.10)K (85, 0.15)
L (80, 20, O), M (70, 30, O
), an even more preferable resistance value can be obtained.

In the above, α-A I2 is used as the matrix material.
Using 20 m alone, α-A! t 20 s, Si
The preferred composition ranges have been described where the contents of C, B, and C are x, y, and z.

When using 203 to α-8 instead of another matrix material, the theoretical density of the other matrix material is ρ3, α
-A 12z When the theoretical density of Os is ρa, A=
100/(1)-X/ρa+z), the matrix material is A x p m / p a parts by weight,
SiC may be used in an amount of A1 parts by weight, and B4C may be used in an amount of Az parts by weight. Each composition range determined by (Aρ1m x/pa, Ay, Az) corresponding to (x, y, z) of point A-M in FIG. 1 is the preferred content weight range of each component. be.

In such a case, the theoretical density of each component is
le Memorial In5titut Co.
lumbus Laboratories and can be easily calculated therefrom.

a-An□Oa is p a = 3, 98 g/cm3
B4C is 2.52 g/cm", SiC is 3.21 g/cm", and in addition, for example, 2Mg0.5iOi is 3.71 g/cm3.

The sintered body of the present invention preferably has such a weight ratio composition, but the volume of SiC/matrix material measured as described above is 1.24 or less.

In addition, the actual density of the sintered body is 75% of the theoretical density of the sintered body.
Above, it is particularly preferable that it is 90 to 100%, especially 95 to 100%. This improves the temporal change characteristics of the electrical resistance value of the element.

In the sintered body of the present invention, a part of silicon carbide or boron carbide is converted into oxides (silicon oxide, boron oxide) during firing.
It may change to

Alternatively, a part of the oxide may be changed to carbide.

However, the content of boron oxide is 0-1 wt%, especially 0.
It is preferable that 1=0.5 wt%.

This is because boron oxide, especially B*Os, becomes glassy, increases the glass phase, and has a low melting point, making it difficult to control the electrical resistance and the particle size of the sintered body.

In addition to a matrix material and silicon carbide and/or boron carbide as a conductive path forming material, the present invention further contains a boride of a group 4A element as a chip processability improving agent.

As a boride of group 4A element, titanium boride (TiB
*) Zirconium boride (ZrB2) is preferred,
In particular, T i B * is optimal.

By containing these, the occurrence of chipping is significantly reduced, and the life of the diamond grindstone during processing is dramatically improved.

These borides of group 4A elements are contained in the thermistor material in an amount of 0.01 to 10 wt% in terms of group 4A elements.

This means that if it is less than 0.01 wt%, the present invention is not effective.
Moreover, if it exceeds 10 wt%, its conductivity deteriorates the characteristics of SiC or B4C as a conductive path forming material, and the high temperature thermistor characteristics and stability deteriorate.

In this case, the content of borides of group 4A elements is 0.1 to
8wt%, especially 0.5-6wt%, even 1-5wt
% is preferable. These borides of Group 4A elements usually exist at grain boundaries or within grains.

Their presence can be confirmed using an analytical electron microscope, and their content may be measured by quantitative analysis using X-ray diffraction.

The thermistor material of the present invention contains a matrix material, silicon carbide and/or boron carbide as a conductive path forming material, a boride of a group 4A element as a chip processability improver, and a group 3A element boride as a subcomponent. It can be constructed from a sintered body containing one or more elements, preferably 0.01 to 10 wt% in terms of element.

The Group 3A element may be contained as an elemental metal, a compound, or a composite of these elements.

As group 3A elements, Y and Ce are particularly preferable, and when contained as a compound, oxides of these elements (Y
zOs, CeOa) or carbides are preferred.

By containing these elements preferably in an amount of 0.01 to 10 wt% in terms of element, the electrical resistance value can be easily controlled and positional variations in the electrical resistance value within the sintered wafer are reduced.

Also, instead of or in addition to the Group 3A elements, iron may be used as a subcomponent, preferably as an elemental metal or as an oxide (Fe20a
), one or more forms of carbides may be included.

Fe• also has the same effect as the 3A group elements.

The content of Fe is preferably 0.01 to 10 wt% in terms of element.

In addition, group 8 elements other than iron, such as C01N l % R
In materials such as U, the amount of oxygen vacancies tends to change at operating temperatures of 500° C. or higher, and as the content increases, electrical resistance deteriorates over time. For this reason, although the inclusion of elemental metals, oxides, carbides, etc. of group 8 elements other than iron is not excluded, it is preferably twt% or less, particularly O-0.5wt%, in terms of element.

Such an effect can also be achieved with oxides of group 2A elements and group 4A elements, as described above regarding the matrix material. As described above, the preferred content of these components is all or part of the matrix material, and is preferably 0.01 wt% or more in terms of element.

Furthermore, the Group 2A elements and Group 4A elements, preferably Mg, Ca, Sr, Ba%Ti.

One or more types of Zr may be a single element or a carbide, and preferably at a content of 0.01 to 10 wt% in terms of element, the resistance value can be easily controlled and its variation is reduced. .

Furthermore, if necessary, other subcomponents may also be contained in the form of simple substances, oxides, carbides, etc.

First, although the inclusion of Group 5A and Group 6A elements has no effect, their inclusion is not necessarily excluded. However, since addition of a large amount deteriorates the thermistor characteristics, it is preferable that the amount does not exceed 10 wt%, especially 1 wt% in terms of element.

Next, it is particularly preferable that Group IA elements such as Na%Li are not contained. This is because when voltage is applied to the thermistor element, these ions move and diffuse.
This is because the resistor easily deteriorates over time. Further, when the glass is sealed, these particles tend to diffuse into the glass, resulting in characteristic deterioration.

The content of group IA elements is 0 to 1 wt% in terms of elements, especially O
It is preferably 0°001 wt%.

Furthermore, the inclusion of Group 7A elements is also not preferred.

This is because the valence of group 7A elements tends to change, and their properties tend to change over time.

The content of the Group 7A element is preferably 0 to 1 wt%, particularly O to 0.05 wt% in terms of element.

Furthermore, since groups 1B and 2B also tend to change over time, it is preferable that the content is 0 to 1 wt%, particularly O to 0.05 wt% in terms of element.

In addition, B, group 3B elements other than AI2, Ga, In,'
rJ2 may also be contained in an amount of about 0 to 1 wt% or less.

However, other than C, SL, 0, N, 4B group, 5B group, 6B
Group, 7B group elements, etc. are unfavorable due to their characteristics, so O~1 w
The content is preferably t%.

Note that trace amounts of nitrides, silicides, borides, etc. may be contained as subcomponents.

The total amount of these subcomponents is preferably 10 wt% or less.

When these subcomponents in the sintered body are contained as compounds, their stoichiometric compositions may be slightly different. In addition, the average particle size is usually in the range of 1 to 5 in the case of a single metal, and in the case of a compound, it is usually 0.1
It is in the range of ~5-.

Furthermore, if necessary, the above-mentioned subcomponents or compounds that change into these by sintering, such as carbonates, organometallic compounds, etc., are added.

Powders of Group 2A, Group 3A, Group 4A, and Fe metals or compounds generally have an average particle size of 1 to 5μ and a purity of 9.
5 wt% or more is used. Alternatively, a solution may be added.

Such a sintered body can be obtained as follows.

A predetermined amount of matrix material powder such as aluminum oxide and silicon carbide powder and/or boron carbide powder are wet-mixed using a ball mill or the like with the addition of a solvent such as ethanol or acetone.

The powder of the above-mentioned oxide such as aluminum oxide (AJ2□03) generally has an average particle size of 0.1 to 5 and a purity of 99.
5 wt% or more is used.

These oxides may be compounds that become oxides by sintering, such as carbonates and organometallic compounds.

The silicon carbide (SLC) powder used generally has an average particle size of 0.5 to 5-5 and a purity of 98 wt% or more.

Boron carbide (84C) powder generally has an average particle size of 0.
5 to 511x1 and a purity of 97 wt% or more is used.

The boride of the 4A group element may be added, for example, as TiB2 powder, and generally has an average particle size of 0.1 to 5-5 and a purity of 98 wt% or more.

In addition, when a boron-containing substance such as boron carbide is contained in a raw material, the boride of a group 4A element can be used as an oxide,
It may be added in the form of a single substance.

At this time, by controlling the sintering conditions as described later, for example, B, C and TiOz react, and for example, T
i B 2 is generated.

In such a case, for example, A I220s is mixed as a matrix material with 84G and/or SiC as a conductive path forming material, and Ti0 is added as a group 4A element source.
When calcining with the addition of
CiTI Cb T t s A 11%Ti, Ti
2Si.

3 (Aβ20n) 2 (S i Oi) may be formed as a by-product.

These compositions may be contained in an amount of 10 wt% or less, particularly 1 wt% or less.

These may be added as powders with purity and particle size similar to those described above.

The amount of solvent is approximately 100 to 120 wt% of the powder.

Further, a dispersant or the like may be further added as necessary.

Thereafter, the above mixture is pressure-molded at room temperature, and then sintered under pressure or hot press in an oxygen atmosphere or a non-oxidizing atmosphere.
The compact is obtained by sintering the compact by a HP) sintering method, a hot isostatic pressing (HIP) method, or the like, and then allowing it to cool.

The pressure during pressure molding is approximately 500 to 2000 kg/c.

The non-oxidizing atmosphere during sintering may be various atmospheres such as an inert gas such as N2Ar or He, H, Co, various hydrocarbons, a mixed atmosphere thereof, or even a vacuum.

In the case of pressureless sintering method, atmospheric pressure is sufficient, and the sintering temperature is 1400℃.
It is effective at temperatures between 1900°C and 1900°C, particularly between 1600 and 1900°C, more preferably between 1750 and 1800°C.

If the temperature is lower than 1400°C, it will not be sufficiently densified even if sintered for a long time, and if the temperature is higher than 1900"C, A
l1. This is because the interaction between oxides such as O and SiC and/or B4C becomes intense.

Sintering time is usually 0.5 to 20 hours.

For HP sintering method, press pressure is 150-250 Kg
/c#, firing temperature is 1400-18o.

°C, especially 1500-1800 °C, more preferably 165 °C
0 to 1750°C is preferred.

If the temperature is lower than 1400°C, a dense sintered body cannot be obtained, and if the temperature is higher than 1800°C, the interaction between the matrix material such as β203 and SiC and/or B and C becomes intense.

Sintering time is generally 1 to 30 hours.

In the case of the HIP sintering method, a compact of raw material powder is pre-sintered in an oxygen atmosphere or a non-oxidizing atmosphere (for example, in a vacuum up to 1200°C, and then preferably in an Ar atmosphere), and then in a HIP furnace. This pre-sintered body is sintered.

The temperature of the preliminary sintering is preferably 1400 to 1650°C, and the time is preferably 1 to 50 hours.

In addition, the sintering temperature in the HIP method is 1200 to 1500
℃, sintering time is 1-50 hours, pressure is 1000-150
0 kg/crrr, and may be carried out in an oxygen atmosphere or an inert atmosphere such as Ar.

In this case, at room temperature, oxygen gas, Ar gas, etc.
Pressure is increased to 0 Kg/crrf, and then pressure is applied by heating as described above.

The above sintering conditions are common to both cases in which borides of group 4A elements are used in advance and cases in which borides of group 4A elements are generated. In order to occasionally generate borides of Group 4A elements, the following profile may be used.

In the cold sintering method, the heating rate is 1 to 100'C/min, the sintering temperature is 1600 to 1900°C, and the holding time at the sintering temperature is 0.5 to 20 hours.

In addition, in the HP method, the heating rate is 1 to 100"C/min,
The sintering temperature is 1400 to 1800°C, and the holding time at the sintering temperature is 1 to 30 hours.

Furthermore, in the HIP method, the temperature increase rate is 1 to 100'C/min,
Pre-sintering temperature 1400-1650℃, holding time at pre-sintering temperature 1-50 hours, sintering temperature 1200-1500℃
, the holding time at the sintering temperature is 1 to 50 hours.

In this way, by increasing the holding time at the sintering temperature in particular, the formation of borides of group 4A elements is promoted, and the grain size of the matrix material becomes coarser in the range of about 10 times or less, making it difficult to process chips. Improves sex.

The thermistor material produced in this way has a resistance value of 500
It is about 102~1O7Ωcm at ℃, and 400~800
There is almost no change in resistance value even when used or stored in the temperature range of ℃. Also, the value of B is 1o at 50 to 480℃.
It is from oo to 5000.

When such thermistor material contains 0.01 to 10 wt% of a boride of a group 4A element, chip processability is dramatically improved.

The thermistor characteristics, glass sealing characteristics, etc. can be changed to the same characteristics as those described in JP-A-64-64202.

For example, regarding the relationship between the composition ratio and resistivity (ρ) of the thermistor material, the change in ρ depending on the amount added is not steep, and it has become easy to obtain a desired low resistance by changing the composition ratio.

One element - 1kΩ Group 2A 100-400 3A group　　　　130~14゜ 4A group 60-3o.

Fe 20-80 The thermistor material produced as described above is applied to the thermistor element of the present invention as a thermistor chip.

As the thermistor element of the present invention, a so-called glass-sealed thermistor element is particularly preferred.

Such a glass-sealed thermistor element 1, for example, as shown in FIG. It has a structure in which the two parts are connected and sealed with glass 5.

Regarding various thermistor elements, please refer to Japanese Patent Application Laid-Open No. 64-6420.
This is detailed in Publication No. 2.

<Effects of the Invention> The thermistor material of the present invention has extremely good chip processability, significantly reduces the occurrence of chipping, and significantly improves the life of the processing grindstone.

Furthermore, it is stable even when used at high temperatures, particularly at temperatures of 400 to 800°C. Furthermore, since the B value can be made considerably low, the temperature coefficient of the thermistor is also small, and the applicable temperature range can be widened. Furthermore, when examining the relationship between the composition ratio and resistivity, the change in resistivity is not steep, and resistance can be controlled by changing the composition ratio. Therefore, the composition range of the target resistance range is expanded, and mass productivity and quality are improved.

When such a thermistor material is applied to a glass-sealed thermistor element, it has the advantage of less foaming. In addition, if you form a so-called integrated thermistor element that is integrated with other materials by heating the presser and joining them, the dimensional accuracy will be good, and dimensional changes will be avoided like when raw materials are integrated by sintering. and variations in characteristics are extremely reduced.

<Examples> Hereinafter, specific examples of the present invention will be shown, and the present invention will be explained in detail.

Example 1-2 and average particle size 1.2-8β203 (purity 99.9wt% or more), average particle size 1.0-SiC (purity 99.5wt%)
or more) B, C with an average particle size of 1,2- (purity 98wt%)
or more) TiBz with an average particle size of 1.2 μm (purity 98 wt%)
or more) ZrBz with an average particle size of 1.8- (purity 98 wt%)
or more), Ti02 with an average particle size of 0.5- (purity 99wt%)
(above) were weighed in the proportions shown in Table 1, and mixed using acetone in a ball mill for 20 hours.

The mixed slurry was dried and granulated and filled into a graphite mold with an inner diameter of 77 mm.

This was hot press sintered in an Ar atmosphere with a sintering profile shown in Table 1 at a press pressure of 200 to 3001 g/cm2.

The obtained sintered body was found to be Al2203, B, and C as a result of X-ray diffraction.
and/or SiC was confirmed to exist.

1. In sample N002.4.6.8 of the present invention,
It was confirmed that borides of Group 4A elements were present and had the compositions shown in Table 1, and that T i B 2 or ZrBa was present at grain boundaries and inside grains.

Furthermore, in sample No. 2.4.6.8, A 1
A coarsening of the grain size at 220 s was observed.

In sample No. 6.8, at the same time as TiBa was generated, trace amounts of TiC%TiTiAr1, TiSi%B,,C2,9(AI
2z 0s) 2 (B, Ox), 3 (Aj2a
Creation of 0x)2(SiO-) etc. was observed.

The SiC/A 1220s volume ratio is determined by mirror-polishing the surface of the sintered body and from this electron micrograph.
The area ratio of /B and C is calculated.

Table 2 also shows the density ratio (%) of the density of the sintered body to the theoretical density.

After cooling, the sintered body measuring 50 x 50 x 0 and 5 mm was taken out from the mold and processed using a peripheral slicing machine to form chips into 0.75 x 0.75 x 0.5 mm.

The conditions for the peripheral slicing machine are as follows.

Diamond blade "400-'0.2mm Grinding wheel rotation speed 30.OOOrpm Grinding fluid Aqueous grinding fluid Cutting processing speed I Q mm/sec The number of slice lines until the diamond blade breaks at this time is shown in Table 2 as the grinding wheel life.

In addition, the number of chips (per 0.1 mm) at a depth of 5 mm or more from the cut surface was measured for 10 chips, and the average number of chips is also shown in Table 2.

Electrodes were attached to these chips using a predetermined method, and the resistivity ρ (Ω
・cm) and thermistor constant B were measured. The results are also listed in Table 2.

A diameter of 0. Lead wires each having a length of 3 mm and a length of 65 mm were connected using a parallel gap welding method.

The thus obtained product was inserted into borosilicate glass having a diameter of 2.5 mm and a length of 4 mm, and the glass was sealed at 850° C. in an Ar gas atmosphere. This was subjected to aging treatment to produce various thermistor elements as shown in FIG.

For these products, changes in resistance values were measured at the initial stage and after storage at 500° C. for 5000 hours.

For evaluation, the change in resistance value was calculated as ゛(ΔR/R,)xlooo (%), where ΔR1 was the initial resistance value as Ro.

The results are shown in Table 2.

Each of these samples maintained good properties even after glass sealing.

From these results, the effects of the present invention are clear.

Note that these results were similarly achieved for all the compositions described in JP-A-64-64202.

[Brief explanation of drawings]

Figure 1 shows Al220 in the thermistor material of the present invention.
It is a ternary diagram showing the composition range of 'a B4CS i C. FIG. 2 is a sectional view showing an example of the thermistor element of the present invention. Explanation of symbols 1...Thermistor element 5...Glass 11...Thermistor chip 33.35...Electrode layer 43.45...Lead body application agency TDC Co., Ltd.

Claims (7)

[Claims] (1) Contains silicon carbide and/or boron carbide as a conductive path forming material, and a matrix material containing one or more of aluminum, silicon, and oxides of group 2A elements, and the content of silicon carbide is A thermistor comprising a sintered body having a volume ratio of 1.24 or less to the content of the substance and further containing a boride of a group 4A element in an amount of 0.01 to 10 wt% in terms of a group 4A element. material. (2) The thermistor material according to claim 1, wherein the density of the sintered body is 75% or more of the theoretical density. (3) The matrix material further contains an oxide of a group 4A element, and the matrix material further contains an oxide of a group 4A element,
The thermistor material according to claim 1 or 2, wherein the content of the oxide of the group A element is 0.5 or less in volume ratio. (4) The thermistor material according to any one of claims 1 to 3, further comprising 0.01 to 10 wt% of a group 2A element or carbide in terms of a group 2A element. (5) The thermistor material according to any one of claims 1 to 4, further comprising 0.01 to 10 wt% of a simple substance, oxide, or carbide of a group 3A element, calculated as a group 3A element. (6) Further add 0.01 iron, oxide or carbide.
The thermistor material according to any one of claims 1 to 5, comprising ~10 wt%. (7) A thermistor element having a thermistor chip formed from the thermistor material according to any one of claims 1 to 6.