JPS6246957A - Positive characteristic semiconductor ceramic with reductionresistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a positive conductor having a PTC characteristic in which the electrical resistance value increases by 8 times when the Curie temperature is exceeded. The present invention relates to a positive characteristic semiconductor porcelain having reduction resistance and used in self-temperature control type heaters, temperature sensors, etc. used in a hostile atmosphere.

[Prior art] Conventionally, Y, La, Sm, Ce, and Q were added to barium titanate.
In porcelain to which rare earth elements such as a or transition elements such as Nb and Ta are added and fired at 1200 to 1400°C in the atmosphere, the electrical resistance increases suddenly at one point.
It is known to exhibit so-called positive characteristics (PTC characteristics). Taking advantage of this characteristic, it is used in heaters, temperature sensors, etc.

A characteristic semiconductor featuring a conventional barium titanate semiconductor! Semiconductor devices using a 2-type device have a problem in that when used in a reducing atmosphere such as hydrogen gas or gasoline, the characteristic PTC characteristic thereof deteriorates.

For example, when used as a self-temperature-controlled heater, due to deterioration of PTC characteristics (hereinafter referred to as R-T deterioration),
Even if the temperature reaches the temperature that should be controlled, the resistance value does not increase, and in the worst case, there is a problem that the PTC element may melt due to energization. In addition, RT deterioration does not occur in a reducing atmosphere (43), but it is also known that RT deterioration occurs to varying degrees even in a neutral atmosphere such as nitrogen or argon gas. ing.

As a result of the above, the environment in which semiconductor elements using positive characteristic semiconductor porcelain whose main component is barium titanate semiconductor has been limited has been limited. Furthermore, when used in the above-mentioned reducing atmosphere environment, the element 11 must be enclosed in a case 4 made of resin or metal and shielded from the environment as shown in Fig. 4. There wasn't. This has led to problems such as a decrease in performance due to poor heat dissipation, and high costs due to an increase in the number of parts and assembly man-hours.

[Problems to be Solved by the Invention] The present invention overcomes the above-mentioned problems and provides a positive characteristic semiconductor porcelain that has good reduction resistance and does not require encapsulating an element in a predetermined case. The purpose is to

Furthermore, in order to overcome the above-mentioned prior art, the present invention relates to a positive characteristic semiconductor porcelain having reduction resistance (Patent Application No. 59-281) related to an unknown earlier application filed by the same applicant as the present application.
418).

In the positive characteristic semiconductor porcelain related to the unknown earlier application, the flux component is 0.14 to 2.88 mff 1 part (7)
TiOz and 0.1~1,6Wffll(7)A
It is composed of R203 and 0.1 to 1.61 fM part (7) SiOz. In the present invention, a zinc compound is further added to the flux component consisting of these three components to achieve the desired purpose.

[Means for Solving the Problems] The positive characteristic semiconductor porcelain having reduction resistance of the present invention includes a barium titanate-based composition, and a 0.00000000000000000000000 barium titanate-based composition.
2-1, 6'fim section Noah) Ltmit (A, l!
tO3), titanium dioxide (Ti02) of 0°14 to 2.88 times, silicon dioxide (SiO2) of 0.1 to 1.6fflffi, and 100 mol of the above barium titanate-based silk composition. On the other hand, the zinc contained in l! i
and a flux component consisting of the zinc-containing ffMr (0.05 to 0.5 mol of a zinc compound).

One-intermittent barium (Ba
CO3) and titanium oxide (TiOz) are usually mixed in equimolar amounts. However, depending on the purpose of use, it is not necessary that the moles be equimolar, and a barium titanate composition as shown in general formula (1) or (2) may be used.

Bat xM3xTiO3---<1>BaT
i l yMsyo3 ... (2) Here, MS and MS are semiconductor cracking agents selected from commonly used rare earth elements and transition elements, and MS is Yl
Any rare earth element such as La, 5IIISCe1Ga, etc. may be used, and as the MS, any transition element such as Nb or Ta may be used. Also, the values of X and y are each 0. ○01～0
．． A range of 0.005.0.0005 to 0.005 is desirable.

The flux component, which is the most distinctive feature of the present invention, is composed of alumina (A 203), titanium dioxide (Ti 02), silicon dioxide (Sin2), and a zinc compound, and the addition ratio of each flux component is barium titanate. Al zo3 is 0.2 to 1.6 per 100 m of the system composition.
Weight i 1 part, T'i0z 0.14 to 2.88 weight part, S
When i 02 is 0.1 to 1.61 parts ffi and the zinc compound is 100 mol of the barium titanate-based composition,
The zinc content is 0.05 to 0.5 in terms of zinc contained.
It is a mole. Each of the flux components needs to be added within the range, and it is not preferable if the amount added is less than the range or too much. Furthermore, as the amount of the flux component added increases, the specific resistance of the positive characteristic semiconductor ceramic tends to increase. In order to solve this problem, the flux component should have a content of 0.2 to 0.
4 parts by weight, 0.14 to 1.15 parts by weight of TiOz, 0.2 to 0.8 parts by weight of 5iOz, and 100 moles of the barium titanate-based composition, converted to the contained zinc. It is preferable that the zinc gold content is contained in an amount of 0.05 to 0.2 mol. If each component is within this content range, the resistivity of the positive characteristic semiconductor porcelain obtained is often 100.
It is less than Ωcm, making it suitable for application to automobile parts.

The zinc compound, which is one of the flux components mentioned above, is usually zinc oxide (ZnO), but is not limited to this. It is acceptable as long as it is included in The raw material for the zinc compound may be ZnO, zinc carbonate (ZnCO3), zinc nitrate (Zn (NO
3) t ), zinc chloride (Zn CR2)'N zinc oxalate (Zn (C204)) or zinc fluoride (ZnF
t), etc., or a mixture thereof. Most of these raw materials are converted into zinc oxide during manufacturing processes such as calcination or firing, but depending on the type of raw material, firing conditions, etc., it may be something that does not turn into ZnO (for example, ZnFz, etc.), or some of it may not turn into ZnO. It can be anything.

As the raw material, ZnO or ZnCO3 is usually used.

AJ2203, TiO2 or 5 of the above flux components
In iOz, the components contained in the positive characteristic semiconductor porcelain after firing are ARzO3, TiO2 or SiO2, respectively.
2 (but the raw material is not limited to oxides. Therefore, the raw material may be hydroxides of various metals such as A1).

The above flux component is B, which is the main ingredient of barium titanate.
It is mixed with aCo3, TiOz, etc., and fired.

By adding the above-mentioned four components within the above-mentioned ranges, the above-mentioned flux components can produce 1 q of positive characteristic semiconductor porcelain having extremely good reduction resistance. In addition, by changing the ratio of each of the above components or the total addition amount of the flux within the above range, it is possible to adjust the growth degree of crystal grains of positive characteristic semiconductor porcelain, thereby producing positive characteristic semiconductors with various performances. It becomes possible to obtain porcelain.

In addition to the above-mentioned components, the positive characteristic semiconductor porcelain of the present invention may also contain titanates such as strontium titanate or lead titanate, zirconates such as barium zirconate, and stannates such as barium stannate. good.

Regarding the lead component, adding it before calcination and making it a solid solution during calcination is more effective for reduction resistance than adding it after calcination and making it a solid solution with Ba Ti 03 during calcination. .

In addition, Pb, Sr, z as curri single point control agents
It is also preferable to add elements such as rS3n, and M n % Fe -C as an additive to improve PTC properties.
It is also preferable to add a trace amount of elements such as O.

The positive characteristic semiconductor porcelain of the present invention is mixed in the same manner as before.
It is obtained by molding and firing.゛The process of making it into a semiconductor is as follows.

First, barium titanate is generated at a temperature of 800 to 1100°C, but in this state the crystal lattice is still disordered.

When the temperature reaches 1,200 to 1,280°C, a part of the flux component begins to melt, and barium titanate rapidly grows and becomes a semiconductor. Then, the flux component is completely melted, and the barium titanate particles are converted into a semiconductor in the liquid phase of the flux component. After being fired in this way, when a cooling process is started, the liquid phase of the flux component solidifies while covering the barium titanate semiconductor particles and becomes integrated.

Although the mechanism by which the positive characteristic semiconductor TA device of the present invention has reduction resistance is not clear, it is presumed that it is because the flux component coats the barium titanate semiconductor grain boundaries and protects them from the reducing atmosphere. .

In addition, conventional positive characteristic semiconductor porcelain has a water absorption rate of approximately 0°5m.
m%, whereas the water absorption rate of the positive characteristic semiconductor porcelain of the present invention is approximately 0.01% by weight or less, which is almost 0%, which is a significant decrease in water absorption rate. For this reason, the fact that the intrusion of reducing substances is reduced is considered to be one of the reasons for the reduction resistance.

[Effects of the Invention] The positive characteristic semiconductor porcelain of the present invention exhibits almost no RT deterioration even when used in a reducing atmosphere, and has excellent PTC characteristics. Therefore, it does not need to be sealed with resin or metal, and can be used in an exposed structure, improving performance not only in neutral atmospheres such as nitrogen or carbon dioxide gas, but also in reducing atmospheres such as hydrogen gas or gasoline. In addition to increasing the degree of freedom in product design, it is particularly effective in reducing costs by 1 or more.

In addition, the positive characteristic semiconductor porcelain of the present invention is less affected by impurities, firing conditions, and the amount of semiconducting agent added, so it is much easier to manufacture than conventional materials, such as using inexpensive industrial raw materials. Become.

As described above, the reduction-resistant positive characteristic semiconductor porcelain of the present invention can be applied to various products such as intake air heaters, fuel heaters, and temperature sensors as automobile parts, for example.

[Test Example] The performance of the positive characteristic semiconductor porcelain of the present invention will be explained below using a test example.

(Test Example 1) - Examination of reduction resistance in hydrogen gas In this test example, BaCO3, Tloz, A, i! 20
3, Si 02, yttrium oxide (Y2O2>, zn
The raw materials were O or Zn CO3 and PbO or LtPbTiO3. Note that all of these used industrial raw materials. These raw materials were blended into 55 different compositions shown in Tables 1 to 3, and pulverized and mixed together with agate boulders in a wet manner for 20 hours in a ball mill. After drying these mixtures, they were calcined at about 1100° C. for 4 hours. Thus j! A slight amount of manganese dioxide (MnO2) was added to the calcined product to improve the withstand voltage (R, T1 characteristics), and it was wet-processed again using agate boulders and a ball mill for 20 minutes.
Time pulverization mixing was performed. After drying, add 10% polyvinyl alcohol aqueous solution as a binder to each mixed powder.
The mixture was press-molded at a pressure of 800k (1/cm').
Baked at ℃ for about 1 hour, diameter 25mm, thickness 2.5mm
A disk-shaped positive characteristic semiconductor porcelain was manufactured.

The specific resistance of the positive characteristic semiconductor porcelain related to Test Example No. 24 is 42Ω・cm1 Curie at 200℃, and the withstand voltage is 1
50V, and the water absorption rate was 0.01W%, which was almost zero (very low compared to the conventional element (0.5wt%)).

In order to investigate the characteristics of the 55 types of positive characteristic semiconductor porcelain obtained, N+ -AO double electrodes N were placed on both sides of each positive characteristic semiconductor porcelain.
t electroless plating, Δg paste) and 20 min in air.
The electrical resistance value (specific resistance RO) at ℃ was measured, and the results are shown in Tables 1, 2, and 3. In addition, each positive characteristic semiconductor porcelain was placed in a hydrogen gas atmosphere, and at 300°C, the electric resistance value (R+) and 3
The electrical resistance value (R2) after 0 minutes was measured, and the rate of change in resistance (ΔR) was measured using the following equation (3).

ΔR=100X(Rz-R+)/R+...(3)
Here, the closer R2 is to R1, that is, the closer ΔR is to 0, the better the reduction resistance is.

The evaluation of each positive characteristic semiconductor porcelain is that △R is O ~ -10% (0
), −10 to −50% is shown as (Δ), and −50% to −50% is shown as (X) in Tables 1, 2, and 3.

In Table 1, barium titanate-based composition 100['
AltO3 is 0.2 to 1 part as a flux component
1.6 parts by weight (hereinafter referred to as weight %) TiOz is 0.
14-2.881ffi%, SiOz is 0.1-1.
Positive characteristic semiconductor porcelain (N019-2
2.24-27.29.30, 34-55) are other positive characteristic semiconductor porcelains (No.
, 12.17.18.28.31-33 (corresponding No. of the above is No, 19-22.29.30.34-
55), No. 16 (Same No.: 26.27)), △R is small at -0.3 to -9.5 (-
11 to -31), clearly excellent in reducing properties of ll14. In addition, Ag2O3, which is a particularly desirable range, is 0.2
~0.411%, r+ot is o.

Positive characteristic semiconductor porcelain (No. 19 to 21.24) containing 14 to 1.15% by weight, 0.2 to 0.8% by weight of 5iOz, and 0.05 to 0.2 mol % of a Zn compound.
~27.29.35.36.39.40.43~45.
49 to 51) have a specific resistance (RO) of 100Ω・cm or less, and ΔR is even smaller (-0, 3 to -8,
8, most of which have an absolute value of 6 or less) and have excellent reduction resistance, making them ideal for application to automobile parts.

(Test Example 2) - Examination of reduction resistance in sour gasoline Next, raw materials with the same composition as those used in Test Example 1 were used, mixed, molded, and fired in the same manner as in Test Example 1. A disk-shaped positive characteristic semiconductor porcelain having a size of 25 mm and a thickness of 2.5 ffiI was manufactured. The obtained positive characteristic semiconductor porcelain was provided with an NI-A (l electrode) on its surface in the same manner as in Test Example 1, and the electrical resistance value of each positive characteristic semiconductor porcelain was approximately continuous from room temperature to 300°C in the atmosphere. A curve representing the PTC characteristics as a solid line (A) shown in the conceptual diagram of FIG. 2 was obtained. Next, each of the positive characteristic semiconductor ceramics was immersed in sour gasoline, and an immersion current durability test was conducted in which a voltage of 30 V was applied for over 200 hours. Ware gasoline is gasoline that has been oxidized to produce peroxides and acids.
This is used for accelerated testing. After the immersion current durability test, the electrical resistance of the positive characteristic semiconductor porcelain was measured almost continuously in the atmosphere from room temperature to 300°C.
A curve representing the PTC characteristics indicated by the broken line (b) in FIG. 2 was obtained.

(RT deterioration (A) shown in Figure 2 is calculated from the difference between the two curves obtained by q), and the results are shown in Tables 1 to 3.
Deterioration (A) is determined by the following formula.

log (R-wax/R'sin)
-1oo (Riax /R1n) -R-T
Deterioration (A) (R...resistance value before durability test, R'...resistance value after durability test, laX...maximum value, 1n...minimum value) Measured in Tables 1 to 3. There are some places where the results are not listed, but this is because positive characteristic semiconductor porcelain with a specific resistance of 1000.01 or more does not generate enough heat in the immersion current durability test and does not provide reliable data. It's something that didn't exist. In addition, the results were judged as (◯) if the degree of (A) was 1 or less, (Δ) if it was 1 to 2, and (X) if the degree was 2 or more.

In Tables 1 to 3, positive characteristic semiconductor porcelain of the present invention (No.
, 19-21.24-27.29.35-37.39.
40, 49 to 51) have a small RT deterioration of +0.2 to -0.7 in logarithm compared to other positive characteristic semiconductor porcelains (e.g. NO, 12, 16, 32, 33) (in the comparative example, −
0.9 to -3°2) Obviously excellent reduction resistance. In addition, AX t 03, which is a particularly desirable range, is 0.2 to 0.
．． 41ffi%, Ti0z is 0.14-1.15%
, 0.2 to 0.8 wt% of 5iQz and 0.05 to 0.2 mol% of a zn compound (N
o, 19-21.24-27.29.35.36.39
．． 40.49-51), RT deterioration is +0.2--0
．． 6, especially excluding No. 49, it is 10.2 to -10.4, and it can be seen that the reduction resistance is particularly excellent.

(Study of the results of Test Examples 1 and 2) (1) Study of raw material zinc compounds The raw material zinc compounds showed almost the same performance for both ZnO and ZnCO3 (No. 24 and 25, No. 626 and 27).
).

<2) Examination of the composition ratio of each flux component Zinc compound (
ZnO) is 6 and 0.05, 0.1, 0.2, 0.3, and 0.5 mol% (respectively No.

19-23)' have excellent reduction resistance. However, when it is 0.01 and 0.02 mol% (No, 17.18, respectively), the performance judgment against both hydrogen and sour gasoline is Δ, and the reduction resistance against both is insufficient.

The composition ratio of AitO3 is 0.1% by weight (No,
31-33), the reduction resistance to hydrogen is Δ, and the reduction resistance to sour gasoline is Δ or X, and the reduction resistance is not good.

In the test examples in Tables 1 to 3, the flux component is Af
In the case of fit3, TiOt, SiOz and J:U zinc compounds, the proportions of each of the 7 lux components in the positive characteristic semiconductor porcelain of the present invention are 0.2 to 1.6% for Affi203 and 0.14 to 0.14% for TiOt. 2.88 fft%5io
x is 0.1~1.6f! 1% OyohiznO etc. is 0.05
When it is 0.5 mol %, the reduction resistance to hydrogen and sour gasoline is excellent.

(3) How to add lead For semiconductor porcelain with positive characteristics with a high Curie point, add pb7i03 after calcination (No. 10 to 12.24
．． 25), PbO was added before calcination, and 3
The one in solid solution with aTi○3 (No, 13 to 15.26.
27) has less scattering of PB and a lower water absorption rate, which is effective for reducing resistance.

<Test Example 3) Among the positive characteristic semiconductor porcelains used in Test Example 1, No. 12 was selected as the conventional composition, and No. 24 was selected as the composition of the present invention, and mixed, molded, and fired in the same manner as in Test Example 1. hand,
A disk-shaped positive characteristic semiconductor porcelain having a diameter of 25 ml and a thickness of 2.5 mi was manufactured. Ni-Ag electrodes were applied to both sides of the obtained two types of positive characteristic semiconductor ceramics, and they were heated at 300°C for 30 minutes in a reducing atmosphere of hydrogen gas! '−,
The electrical resistance value of each positive characteristic semiconductor porcelain was measured almost continuously during that 30 minutes, and the rate of change in resistance was determined based on the electrical resistance value immediately after being placed in the reducing atmosphere. The results are shown in Fig. 1. Fig. 1 J: Clearly, positive characteristic semiconductor porcelain No. 12 with the conventional composition shows a 68% decrease in resistance change rate (ΔR) in hydrogen gas. However, in the positive characteristic semiconductor 6fi device No. 24 of the present invention, the resistance change rate (ΔR) decreased by only 4.4% in hydrogen gas, and there was almost no change.

In particular, the positive characteristic semiconductor porcelain of the present invention has excellent resistance to reduction, with almost no change in electrical resistance even in a reducing atmosphere of hydrogen gas.

Although the mechanism by which the reduction resistance improved is not clear, the addition of fluxes of A, 1i203, TiO2, StOz and UZn compounds significantly reduced the water absorption rate.
It is thought that one of the reasons is that the intrusion of reducing substances has decreased.

(Test Example 4) The present invention has made it possible to use positive characteristic semiconductor porcelain in an exposed structure in gasoline. Figure 5 shows the results of a comparison of engine torque performance for heaters with an exposed structure (Figure 3) and heaters with an exposed structure (Figure 3).The engine conditions in this case were 1600 rpm (150 rpm).
0cc), 4゜5ko・11 SW/Choke, A/
F: 11 to 12, and 11 characteristics 'I' lK
Porcelain with a composition of No. 24 was used in both cases.

According to the results, by using the positive characteristic semiconductor porcelain according to the present invention, an exposed structure is possible, and the engine torque performance is better than that of a conventional sealed structure.

[Brief explanation of the drawing]

Figure 1 is a diagram showing changes in electrical resistance in hydrogen gas. Figure 2 is a diagram showing RT deterioration in sour gasoline. Figure 3 is a diagram showing the resistance to reduction of the present invention. Fig. 4 is an explanatory diagram in which the positive characteristic semiconductor porcelain having a resistance to reduction of the present invention is applied to an intake air heating heater in an exposed structure. It is an explanatory diagram. Figure 5 is a diagram showing the engine torque performance when the intake air heating heater shown in Figures 3 and 4 is used. 1.11...Positive characteristic semiconductor porcelain 2.21 ... Gasoline engine heat insulator 3.31 ... Spring 4 ... Case (A) ... R-T deterioration (a) ... Initial state (b) ... Patent applicant after durability test Nippondenso Co., Ltd. Agent Patent Attorney Hiroma Okawa Patent Attorney Akio Maruyama Figure 1 Figure 2 Temperature (0C) Figure 3 Figure 4 A

Claims (4)

[Claims] (1) A barium titanate composition, and 0.00 parts by weight per 100 parts by weight of the barium titanate composition.
2 to 1.6 parts by weight of alumina (Al_2O_3), 0.
14 to 2.88 parts by weight of titanium dioxide (TiO_2),
0.1 to 1.6 parts by weight of silicon dioxide (SiO_2) and 100 mol of the above barium titanate composition,
The zinc content is 0.05 to 0.5 in terms of zinc contained.
1. A positive characteristic semiconductor porcelain having reduction resistance, characterized in that it consists of a flux component composed of a zinc compound that is mol. (2) The flux component is barium titanate composition 1
0.2 to 0.4 parts by weight of alumina (
Al_2O_3), 0.14 to 1.15 parts by weight of titanium dioxide (TiO_2), 0.2 to 0.8 parts by weight of silicon dioxide (SiO_2), and 100 moles of the above barium titanate composition. 2. The positive characteristic semiconductor porcelain having reduction resistance according to claim 1, comprising a zinc compound having a zinc content of 0.05 to 0.2 mol in terms of zinc. (3) The positive characteristic semiconductor porcelain having reduction resistance according to claim 1, wherein the zinc compound is zinc oxide (ZnO). (4) The barium titanate composition has the general formula Ba_1_-
＿xM^3×TiO_3 or BaTi_1_-_y
M^5_yO_3 (However, M^3 is Y, La, Sm, C
e, rare earth elements such as Ga, M^5 are transition elements such as Nb and Ta, x is 0.001 to 0.005, y is 0.0005
The positive characteristic semiconductor porcelain having reduction resistance as claimed in claim 1, having a composition of