JPH0811709B2 - Positive characteristic semiconductor porcelain with reduction resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a positive temperature coefficient semiconductor porcelain having a PTC characteristic in which the electric resistance value remarkably increases when the Curie temperature is exceeded, and is mainly used in a reducing gas atmosphere. The present invention relates to a reduction-resistant positive-characteristic semiconductor porcelain used for a self-temperature control type heater, a temperature sensor, etc. used.

[Prior Art] Conventionally, in barium titanate, rare earth elements such as Y, La, Sm, Ce, and Ga, or transition elements such as Nb and Ta are added, and burned in the atmosphere at 1200 to 1400 ° C. It is known that the point shows a so-called positive characteristic (PTC characteristic) in which the electric resistance value suddenly increases. Utilizing this characteristic, it is used for heaters, temperature sensors and the like.

A conventional semiconductor device using a positive-characteristic semiconductor porcelain mainly composed of barium titanate semiconductor has a characteristic PTC characteristic when used in a reducing atmosphere such as hydrogen gas or gasoline. There was a problem of deterioration. For example, when it is used as a self-temperature control type heater, the resistance value does not rise even when the temperature reaches a temperature to be controlled due to deterioration of PTC characteristics (hereinafter referred to as RT deterioration),
In the worst case, there was a problem that the PTC element was melted and damaged by energization. It is also known that RT deterioration does not occur only in a reducing atmosphere, but RT deterioration also occurs to some extent in a neutral atmosphere such as nitrogen or argon gas.

From the above, the use environment of the semiconductor element using the positive-characteristic semiconductor porcelain containing the barium titanate semiconductor as the main component had to be limited. When used in an environment of the above reducing atmosphere, as shown in FIG. 5, the element 11 must be enclosed in a case 4 made of resin or metal and shielded from the environment before use. There wasn't. As a result, there have been problems such as a decrease in performance due to deterioration of heat dissipation, and an increase in cost due to an increase in the number of parts and assembling steps.

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

Further, the present invention relates to a reduction-resistant positive-characteristic semiconductor porcelain (patent application No. 59-281418) relating to an unknown prior application filed by the same applicant as the present application in order to overcome the above-mentioned conventional technique.
Regarding the improvement of. In the positive characteristic semiconductor porcelain according to the previously unknown prior application, the flux component is 0.14 to 2.88 parts by weight.
TiO ₂ , 0.1-1.6 parts by weight Al ₂ O ₃ , 0.1-1.6 parts by weight S
iO ₂ and. In the present invention, a potassium 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 and the present invention is a positive-characteristic semiconductor porcelain used by being exposed to the reducing atmosphere without being sealed in the reducing atmosphere. A barium titanate-based composition and, based on 100 parts by weight of the barium titanate-based composition, 0.2 parts by weight or more and less than 1.6 parts by weight of alumina (Al ₂ O 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 barium titanate-based composition, the potassium content is 0.01 to And a flux component composed of a potassium compound of 0.6 mol. Here, the flux component means an auxiliary agent having a compositional component contained in the porcelain after firing, and when the raw material of the auxiliary agent is referred to as a flux raw material, the two are distinguished.

Barium carbonate (BaCO), which is the main component of barium titanate used in the positive-characteristic semiconductor porcelain having reduction resistance of the present invention, is used.
₃ ) and titanium oxide (TiO ₂ ) are usually mixed in equimolar amounts. However, it is not necessary to be equimolar depending on the purpose of use, and a barium titanate-based composition represented by the general formula (1) or (2) can be used.

Ba _1x M ³ _x TiO ₃ (1) BaTi _1y M ⁵ _y O ₃ (2) where M ³ and M ⁵ are semiconducting agents selected from commonly used rare earth elements and transition elements. , M ³ is Y,
Any rare earth element such as La, Sm, Ce or Ga may be used, and M ⁵ may be any transition element such as Nb or Ta. The values of x and y are preferably 0.001 to 0.005 and 0.0005 to 0.005, respectively.

The flux component, which is the greatest feature of the present invention, is alumina (Al ₂ O ₃ ), titanium dioxide (TiO ₂ ), silicon dioxide (SiO ₂ ).
₂ ) and a potassium compound, and the composition ratio of each flux component is such that Al ₂ O ₃ is 0.2 parts by weight or more and less than 1.6 parts by weight, and TiO ₂ is 100 parts by weight of the barium titanate-based composition.
₂ is 0.14 to 2.88 parts by weight, SiO ₂ is 0.1 to 1.6 parts by weight and when the potassium compound is 100 mol of the barium titanate-based composition, the potassium content is 0.01 to 0.6 mol in terms of potassium atoms contained. is there. It is necessary that each of the flux components be added within the above range, and it is not preferable if the added amount is less than the above range or too much. Furthermore, as the amount of the flux component added increases, the specific resistance of the PTC semiconductor ceramic tends to increase. In order to solve this problem, the flux component is Al ₂ O ₃ 0.2 parts to 100 parts by weight of the barium titanate-based composition.
~ 0.4 parts by weight, TiO ₂ 0.14 to 1.15 parts by weight, SiO ₂ 0.2 to 0.
When the barium titanate-based composition is 8 parts by weight and the potassium compound is 100 mol, it is desirable that the potassium content is 0.01 to 0.2 mol in terms of potassium contained. If each component is in this range, the specific resistance of the positive-characteristic semiconductor porcelain obtained is about 200 Ω · cm or less, and most of them are 100 Ω · cm or less, which is suitable for application to automobile parts.

The potassium compound, which is one of the above flux components,
Usually, it is potassium oxide (K ₂ O), but it is not limited thereto, and may be any one contained in the positive temperature coefficient semiconductor porcelain of the present invention as a potassium compound under a predetermined sintering condition. As a raw material of the potassium compound, K ₂
O may be used, or potassium carbonate (K ₂ Co ₃ ), potassium nitrate (KNO ₃ ), potassium chloride (KCl), potassium hydroxide (KO
H) or the like, or a mixture thereof. Raw material is much in calcination or firing in manufacturing processes often seems to be a K ₂ O, kinds of raw materials, may be one which does not become K ₂ O by firing conditions and the like, a part of K ₂ O It does not have to be

As the raw material, K ₂ CO ₃ or KNO ₃ is usually used.

Also in the above flux components Al ₂ O ₃ , TiO ₂ or SiO ₂ , the components contained in the positive temperature coefficient semiconductor porcelain after firing may be Al ₂ O ₃ , TiO ₂ or SiO ₂ , respectively, as a raw material thereof. Is not limited to oxides. Therefore, the raw material may be a hydroxide of each metal such as Al.

The above flux components become the main agent of barium titanate
It is mixed with BaCO _3, TiO _2, etc., and baked. By adding the above-mentioned four components within the above range, it is possible to obtain a positive temperature coefficient semiconductor ceramic having extremely good reduction resistance. Further, by changing the ratio of each component within the above range or the addition amount as the whole flux, it becomes possible to adjust the growth degree of the crystal particles of the positive characteristic semiconductor porcelain and the positive characteristic semiconductor having various performances. It becomes possible to obtain porcelain.

In addition to the above components, the positive temperature coefficient semiconductor porcelain of the present invention includes titanates such as strontium titanate or lead titanate,
A zirconate such as barium zirconate or a stannate such as barium stannate may be contained. The lead component was added before calcination with lead oxide (PbO) and dissolved during calcination, rather than added after calcination with PbTiO ₃ and solid solution with BaTiO ₃ during calcination. Is more effective in reducing resistance.

It is also preferable to add elements such as Pb, Sr, Zr and Sn as Curie point control agents, and it is also preferable to add a trace amount of elements such as Mn, Fe and Co as additives for improving PTC characteristics.

The positive temperature coefficient semiconductor porcelain of the present invention can be obtained by mixing, molding and firing in the same manner as in the past. The process of making the semiconductor is as follows.

First, barium titanate is produced at a temperature of 800 to 1100 ° C, but the crystal lattice is still disordered in this state. 1200
When it reaches ~ 1280 ° C, some of the flux components begin to melt,
Barium titanate becomes a semiconductor while rapidly growing.
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.
In the cooling process after firing in this way, the liquid phase of the flux component is solidified while covering the barium titanate semiconductor particles, and is integrated.

Although the mechanism by which the positive-characteristic semiconductor porcelain of the present invention has resistance to reduction is not clear, it is presumed that the flux component covers the barium titanate semiconductor grain boundary and protects it from the reducing atmosphere. Further, the water absorption rate of the conventional positive temperature coefficient semiconductor porcelain was about 0.5% by weight, whereas the water absorption rate of the positive temperature coefficient semiconductor porcelain of the present invention was about 0.01% by weight, which was almost 0%, and the water absorption rate was remarkably reduced. are doing. For this reason, it is considered that the reduction substance invasion is reduced, which is one of the reasons for the reduction resistance.

[Effect of the Invention] The positive temperature coefficient semiconductor porcelain of the present invention has an excellent PTC characteristic because it hardly causes RT deterioration even when used in a reducing atmosphere and does not cause reduction deterioration even when the Curie temperature becomes high. are doing. Therefore, not only in a neutral atmosphere such as nitrogen and carbon dioxide, but also in a reducing atmosphere such as hydrogen gas or gasoline,
Since it does not need to be sealed with resin or metal and can be used in an exposed structure, it improves heater performance, expands the degree of freedom in product design, and is particularly effective in reducing costs. .

Further, since the positive temperature coefficient semiconductor porcelain of the present invention is not easily affected by impurities, firing conditions, and the amount of addition of the semiconducting agent,
It is much easier to manufacture than in the past, because cheap industrial raw materials can be used.

From the above, the positive-characteristic semiconductor porcelain having reduction resistance of the present invention, particularly those having a small specific resistance, for example, 100 Ω · cm or less, for example, as an automobile part intake air heater, fuel heater or temperature sensor and the like. It can be applied to various products.

[Test Example] The performance of the positive temperature coefficient semiconductor porcelain of the present invention will be described below with reference to a test example.

(Test Example _{1) - BaCO 3, TiO 2} , Al 2 O 3, SiO 2 in the study this test example of reduction resistance in the hydrogen gas, yttrium oxide _{(Y 2 O 3), K} 2 CO 3 or KNO ₃ and PbO or PbTi
O ₃ was used as a raw material. All of these were industrial raw materials. Each of these raw materials was blended into 55 types of compositions shown in Tables 1 to 3, and each was pulverized and mixed with agate stone by a ball mill for 20 hours in a wet manner. In addition, in Tables 1 to 3, the value showing the addition ratio of the flux raw material such as K ₂ CO ₃ represents the mol% of this raw material with respect to Ba and Pb, as indicated by * 2. Then, these mixtures were dried and then calcined at a temperature of about 1100 ° C. for 4 hours. In order to improve the withstand voltage (R, T, characteristics) of the thus obtained calcined product, manganese dioxide (MnO ₂ ) was added in a small amount, and the mixture was again pulverized and mixed with agate boulders in a ball mill for 20 hours. After drying, 1% by weight of a 10% polyvinyl alcohol aqueous solution as a binder was added to each mixed powder and mixed, and the mixture was press-molded at a pressure of 800 kg / cm ² . These molded products were fired in air at about 1320 ° C. for about 1 hour to produce a disk-shaped positive-characteristic semiconductor porcelain having a diameter of 25 mm and a thickness of 2.5 mm.

The positive resistance semiconductor porcelain of Test Example No. 24 has a specific resistance of 92 Ω · cm, a Curie point of 200 c, and a withstand voltage of 150 V.
In addition, the water absorption rate is 0.01 wt%, which is almost zero and the conventional element (0.
5 wt%) was extremely low.

In order to investigate the characteristics of the 55 types of positive-characteristic semiconductor porcelain thus obtained, Ni-Ag electrodes (Ni electroless plating, Ag paste) were applied to both sides of each positive-characteristic semiconductor porcelain, and the electrical resistance value at 25 ° C in the atmosphere ( The specific resistance R ₀ ) was measured, and the results are shown in Table 1 and Table 2.
The results are shown in Tables and Table 3. Also, put each PTC semiconductor porcelain in a hydrogen gas atmosphere and measure the electrical resistance (R ₁ ) immediately after putting each PTC semiconductor porcelain and the electrical resistance value (R ₂ ) after 30 minutes at 300 ° C. The rate of change in resistance (ΔR) was measured by the following equation (3).

ΔR = 100 × (R ₂ −R ₁ ) / R ₁ (3) Here, the closer R ₂ is to R ₁ , that is, the closer ΔR is to 0,
Excellent reduction resistance.

The evaluation of each positive characteristic semiconductor porcelain is as follows: Table 1 Table 2 Table 2 It is shown in Table 3.

In Table 1, 0.2 to 1.6 parts by weight of AlO ₃ (hereinafter referred to as% by weight) as a flux component, 0.14 to 2.88% by weight of TiO ₂ , and Si of 100 parts by weight of the barium titanate-based composition.
O ₂ is 0.1 to 1.6% by weight, and the potassium compound is 0.01 to 0.6 mol (hereinafter referred to as mol%) in terms of potassium atom based on 100 mol of the barium titanate-based composition.
When the addition amount of the raw material compound such as K ₂ CO ₃ is shown as shown in Table 1, it is referred to as raw material mol%. ) The positive characteristic semiconductor porcelain (No. 18 to 27, 29, 30, 34 to 55) included is a positive component semiconductor porcelain (No.
ΔR is as small as −0.5 to −9.5 (-8 to 31 to 33) (−21 to −62 in the comparative example), and is clearly excellent in reduction resistance. Further, particularly desirable ranges of Al ₂ O ₃ are 0.2 to 0.4% by weight, TiO ₂ is 0.14 to 1.15% by weight, and SiO ₂ is 0.2 to 0.8% by weight.
And positive content semiconductor porcelain containing 0.01 to 0.2 mol% of potassium (No.18 to 20, 24 to 27, 29, 35, 36, 39, 4
₀ , 49-51) has a small specific resistance (R ₀ ) of about 200 Ω · cm or less (mostly 100 Ω · cm or less), has a small ΔR, and is more excellent in reduction resistance. Is most suitable for application.

(Test Example 2) -Study of reduction resistance in sour gasoline Next, using a raw material having the same composition as that used in Test Example 1, mixing, molding and firing were performed in the same manner as in Test Example 1 to obtain a diameter. A disc-shaped positive-characteristic semiconductor porcelain having a thickness of 25 mm and a thickness of 2.5 mm was manufactured. The obtained positive-characteristic semiconductor porcelain was provided with a Ni-Ag electrode on the surface in the same manner as in Test Example 1, and the electric resistance value of each positive-characteristic semiconductor porcelain was measured substantially continuously in the air from room temperature to 300 ° C. Then, the PT of the solid line (a) shown in the conceptual diagram of FIG.
A curve representing the C characteristic was obtained. Next, each positive-characteristic semiconductor porcelain was immersed in sour gasoline, and an immersion current durability test was performed in which a voltage of 30 V was applied for 200 hours or more. Here, sour gasoline is gasoline that has been oxidized to generate peroxides and acids, and is used for accelerated tests. After the immersion current durability test, the positive resistance semiconductor porcelain was measured for electrical resistance in the atmosphere from room temperature to 300 ° C almost continuously, and a curve showing the PTC characteristic of the broken line (b) in Fig. 2 was obtained. . The RT deterioration (A) shown in FIG. 2 was obtained from the difference between the two obtained curves, and the results are shown in Tables 1-3.
The RT deterioration (A) is obtained by the following equation.

log (R'max / R'min) -log (Rmax / Rmin) = RT deterioration (A) (R ... resistance value before endurance test, R '... resistance value after endurance test, max ... maximum value, min… Minimum value) In Tables 1 to 3, there is a part where the measurement result is not described, but this is because the positive resistance semiconductor porcelain with a specific resistance of 100 Ω · cm or more shows sufficient heat generation in the immersion current durability test. It was not measured because it was not possible to obtain reliable data. In addition, in the determination of the result, the degree of (A) is within 1 (o), 1-2 is (Δ), and 2 or more is (x).

In Tables 1 to 3, the positive-characteristic semiconductor porcelain (N
o.18 to 20, 24 to 27, 29, 34, 35, 39, 52) has RT deterioration of +0.1 to -0.9 in logarithmic value compared to other positive characteristic semiconductor porcelains (for example, No. 17). (-2.6 in No. 17), it is clearly excellent in reduction resistance. The test examples of the present invention (No. 18 to 20, 24 to 27, 29, 34, 35, 39, 52) are 0.2 to 0.4% by weight of Al ₂ O ₃ , which is a particularly desirable range of 0.14 to TiO ₂ .
1.15 wt%, SiO ₂ 0.2-0.8 wt% and potassium content 0.01-0.2 mol%.

(Study of Results of Test Examples 1 and 2) (1) Investigation of Raw Material Potassium Compound The raw material potassium compound exhibited almost the same performance in both K ₂ CO ₃ and KNO ₃ (No. 24 and 25, No. 26). 27).

(2) Examination of composition ratio of each flux component Potassium compound (raw material) (K ₂ CO ₃ ) was 0.005, 0.01,
0.05, 0.1, 0.2, 0.3 Raw material mol% (No. 18 to 2 for each)
3) has excellent reduction resistance. Especially 0.005, 0.01, 0.
05, 0.1 For raw material mol% (No.18-21), the specific resistance is
It is 100 Ω · cm or less, and more preferable. But that is 0.0
In the case of 01 and the raw material mol% (No. 17), the performance judgment for both hydrogen and sour gasoline was Δ, and the reducibility for both was insufficient.

When the composition ratio of Al ₂ O ₃ is 0.1% by weight (No. 28, 31 to 3
3), Reduction resistance to hydrogen is Δ or ×, and reduction resistance is not good. The reducibility for sour gasoline is N
o.32 was good.

In the test examples of Tables 1 to 3, the flux component was Al ₂ O.
_In case of 4 components of ₃ , TiO ₂ , SiO ₂ and potassium compound,
The proportion of each flux component in the positive temperature coefficient semiconductor porcelain of the present invention is 0.2 to 1.6% by weight of Al ₂ O ₃ , 0.14 to 2.88% by weight of TiO ₂ , 0.1 to 1.6% by weight of SiO ₂ and potassium compound as a potassium atom. When converted to 0.01-0.6 mol% (No.17-
Out of 55, all test examples except No. 17, 28, 31 to 33), and reduction resistance to hydrogen or sour gasoline is excellent.

A three-component system of Al ₂ O ₃ , TiO ₂ and SiO ₂ (for example, No.
11 and 12) have a Curie temperature of 150 ℃ or higher (160 ℃ and 180 respectively)
In contrast to the present invention (for example, Nos. 24 and 25), there is no problem even when the Curie temperature is 200 ° C., and by adding a potassium compound, the PTC semiconductor magnetic material having a high Curie temperature can be obtained. Also, the reduction resistance becomes good.

(3) Lead addition method For positive-characteristic semiconductor porcelain with a high Curie point, PbO should be added before calcination rather than PbTiO ₃ after calcination (No.10-12, 24, 25). The solid solution with BaTiO ₃ during baking (No. 13 to 15, 26, 27) is effective for reduction resistance because Pb is less scattered and the water absorption rate is also smaller.

(Test Example 3) Of the positive temperature coefficient semiconductor porcelain 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 mixing, molding and firing were performed in the same manner as in Test Example 1. 25m in diameter
A disc-shaped positive-characteristic semiconductor porcelain having a thickness of 2.5 mm and a thickness of 2.5 mm was manufactured. Ni-Ag electrodes were applied on both sides of the obtained two types of positive-characteristic semiconductor porcelain, and 300% was set in hydrogen gas in a reducing atmosphere.
It was left at ℃ for 30 minutes. The electric resistance value of each positive-characteristic semiconductor porcelain during the 30 minutes was measured almost continuously, and the resistance change rate was calculated based on the electric resistance value immediately after being put into the reducing atmosphere. The results are shown in Fig. 1. Show. It is clear from Fig. 1 that the positive characteristic semiconductor porcelain (having higher performance than the conventionally known positive characteristic semiconductor magnet) of which the flux component is a ternary composition has a resistance change rate of 68% in hydrogen gas. Although there is a decrease in (ΔR), the positive temperature coefficient semiconductor porcelain No. 24 of the present invention has only a 6.4% decrease in the rate of change in resistance (ΔR) in hydrogen gas, and there is almost no change. It was That is, the positive temperature coefficient semiconductor porcelain of the present invention has very little change in electric resistance even in a reducing atmosphere of hydrogen gas, and is extremely excellent in reduction resistance.

Although the mechanism of improvement in reduction resistance is not clear, the addition of the flux components of Al ₂ O ₃ , TiO ₂ , SiO ₂ and potassium compounds significantly reduced the water absorption rate and reduced the penetration of reducing substances. Is also considered to be a factor.

(Test Example 4) Torque performance of each engine when the positive temperature coefficient semiconductor porcelain (No. 24) according to the present invention has an exposed structure as shown in FIG. 3 or a sealed structure as shown in FIG. FIG. 5 shows the results of evaluating the above and comparing both. The engine conditions in this case were 1600 rpm (1500 cc), 4.5 kgm, W / choke, and A / F: 11-12.

According to this result, when the positive temperature coefficient semiconductor porcelain according to the present invention is used in the exposed structure, the engine torque performance becomes better than that in the case of the conventional sealed structure.

[Brief description of drawings]

FIG. 1 is a diagram showing changes in electric resistance value in hydrogen gas, and FIG. 2 is a diagram showing RT deterioration in sour gasoline. FIG. 3 is an explanatory diagram in which the positive-characteristic semiconductor porcelain having reduction resistance of the present invention is applied to an intake air heater with an exposed structure. FIG. 4 is an explanatory diagram in which the positive-characteristic semiconductor porcelain having reduction resistance of the present invention is applied to an intake air heater with a sealed structure. FIG. 5 is a diagram showing the engine torque performance when the intake air heaters shown in FIGS. 3 and 4 are used. 1, 11 …… Positive characteristic semiconductor porcelain 2, 21 …… Gas engine heat insulator 3, 31 …… Spring, 4 …… Case (A) …… RT deterioration (a) …… Initial state (b)… … After durability test

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Junji Niwa, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor, Naoto Miwa, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nidec Within the corporation (56) References Japanese Patent Publication Sho 49-21876 (JP, B1)

Claims (4)

[Claims] 1. A positive-characteristic semiconductor porcelain used by being exposed to a reducing atmosphere without being sealed in a reducing atmosphere, comprising: a barium titanate-based composition; and 100 parts by weight of the barium titanate-based composition. 0.2 parts by weight or more and less than 1.6 parts by weight of alumina (Al ₂ O 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 the above barium titanate-based composition
A positive-characteristic semiconductor porcelain having reduction resistance, which comprises: a flux component composed of a potassium compound having a potassium content of 0.01 to 0.6 mol in terms of potassium atoms contained with respect to 100 mol. . 2. The flux component is 0.2 to 0.4 parts by weight of alumina (Al ₂ per 100 parts by weight of the barium titanate-based composition).
O _3), 0.14~1.15 parts by weight of titanium dioxide (TiO _2), 0.2
To 0.8 parts by weight of silicon dioxide (SiO ₂ ), and a potassium compound having a potassium content of 0.01 to 0.2 mol in terms of potassium atoms contained with respect to 100 mol of the barium titanate-based composition. A positive-characteristic semiconductor porcelain having reduction resistance according to claim 1. 3. A potassium compound is potassium oxide (K ₂ O).
The positive-characteristic semiconductor porcelain having reduction resistance according to claim 1. 4. A barium titanate-based composition has the general formula Ba _1-x M
³ _x TiO ₃ or BaTi _1-y M ⁵ _y O ₃ (M ³ is Y, La, Sm,
Rare earth elements such as Ce and Ga, M ⁵ is a transition element such as Nb and Ta, x is
The positive-characteristic semiconductor porcelain having reduction resistance according to claim 1, which has a composition of 0.001 to 0.005 and y is 0.0005 to 0.005, respectively.