JP2705019B2 - Porcelain semiconductor composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a porcelain semiconductor composition having particles and grain boundaries, wherein crystal grain finer than the above-mentioned particles having the same composition as the above-mentioned particles is present in the grain boundary portion. The present invention relates to a porcelain semiconductor composition and a method for producing the same. More specifically, in a semiconductor formed by valence control, for example, in a barium titanate-based porcelain semiconductor composition having particles and grain boundaries, the grain boundary and the grain boundary centered on the junction of a plurality of particles are described above. Those having finer particles than the above particles having the same composition as the particles have a positive temperature coefficient of resistance near the Curie point (PTC characteristics) and have excellent characteristics of low resistivity at room temperature. The present invention relates to a product and a method for producing the same.

[Conventional technology]

BACKGROUND ART Conventionally, porcelain compositions are classified into the following three types based on their electrical properties.

(1) Insulator (2) Semiconductor (3) Conductor. Among them, in the porcelain composition having the electrical properties of the semiconductor of (2), from the surface observation of the porcelain semiconductor composition, the electric resistance and the grain / grain boundary structure are closely related under a specific relationship. Is known to be. In other words, for example, in a barium titanate-based porcelain semiconductor, it is already reported in literatures that the particles having a large particle size and a small proportion of the whole grain boundary portion have a small electric resistance value of the porcelain semiconductor. I have.

It is widely known that adding an oxide such as lanthanum, tantalum, yttrium, bismuth, silver, or dysprosium to a barium titanate-based porcelain composition results in a porcelain semiconductor having a positive temperature coefficient of resistance. On the other hand, it is also proposed that silicon dioxide is added to a barium titanate-based porcelain semiconductor composition containing a rare earth element, tantalum, niobium or antimony, and firing in the presence of oxygen improves the electrical properties of the porcelain semiconductor composition. (See JP-A-53-59888).

[Problems to be solved by the invention]

However, in a porcelain semiconductor composition, a composition having a positive temperature coefficient of resistance and having a lower resistivity at room temperature is desired.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present inventors have conducted various studies on semiconductor conversion by valence control in order to further improve the characteristics, and as a result of observing the surface structure of each of the obtained porcelain semiconductor compositions, the results show that the results are extremely low. The present inventors have found that the surface structure of the resistance-modified ceramic semiconductor composition has a structure unique to particles and grain boundaries, and have completed the present invention.

The porcelain semiconductor composition according to the present invention, in a porcelain semiconductor composition comprising particles and grain boundaries, small particles finer than the above particles having the same composition as the composition of the above particles, at the grain boundary centered on the association point It is characterized by having.

That is, in a barium titanate-based porcelain semiconductor composition having particles and grain boundaries, for example, the majority of the particles are converted into semiconductors, and grain boundaries occupying gaps between the particles, particularly a plurality of particles. The semiconductor is characterized in that it is made into a semiconductor with the same composition as the above-mentioned particles and the presence of small particles finer than the above-mentioned particles, centering on the meeting point which is the grain boundary where the above-mentioned particles are associated. The composition has a positive temperature coefficient of resistance and extremely low resistivity at room temperature due to its particle / grain boundary structure.

This is conventionally considered that, in a porcelain semiconductor composition having particles and grain boundaries that have been converted into a semiconductor by valence control or the like, the property of a positive temperature coefficient of resistance is attributed to a phenomenon at the grain boundaries. It is believed that the resistivity at room temperature of such a composition is determined as the resistance in which the particles and the grain boundaries are respectively connected in series.

Therefore, conventionally, even if the resistivity in the semiconductor-formed particles can be reduced, the resistivity at the grain boundaries where segregation of a small amount of additives and impurities during firing is high, and the resistivity as the composition is low. However, in the above-described composition, the influence of grain boundaries is small because there are fine semiconductor-like small particles having the same composition between the particles, particularly between the particles around the association point. It is determined that it is.

On the other hand, the above-mentioned method for producing a porcelain semiconductor composition involves blending antimony pentoxide (Sb ₂ O ₅ ) or the like as a semiconducting agent based on valence control with, for example, a barium titanate base composition containing a Curie point transfer substance. By firing at 1300 to 1400 ° C., a ceramic semiconductor composition having a positive temperature coefficient of resistance and having a very small resistivity at room temperature is obtained.

That is, first, antimony pentoxide (Sb ₂ O ₅ ) or the like is blended as a semiconducting agent into a barium titanate base composition containing a Curie point transfer material such as strontium carbonate (SrCO ₃ ). At this time, manganese carbonate (MnC
O ₃ ) and silicon dioxide (SiO ₂ ) as a voltage-dependent stabilizer.

Next, the above composition is wet-mixed in an automatic mortar for 1 to 24 hours in the presence of ethanol (reagent grade), dried, and calcined at 1000 to 1400 ° C for 1 to 3 hours. The calcined compound is pulverized, added with an aqueous solution of 2 to 8 wt% of PVA (polyvinyl alcohol) in an automatic mortar, mixed for 1 to 6 hours, dried, and pulverized sufficiently. After molding this powder in a disk-shaped molding machine, the molded product is 1300 ~ 1400 ℃
At 0 to 10 hours, followed by firing to obtain a barium titanate-based ceramic semiconductor composition.

Hereinafter, the ceramic semiconductor composition of the present invention and the method for producing the same will be described in more detail with reference to Examples and Comparative Examples.

Example 1 68.09 g of anhydrous barium carbonate (BaCO ₃ , a high-purity product manufactured by Nippon Chemical Industry Co., Ltd.) and high-purity titanium dioxide (Ti
O ₂ , 29.02 g, manufactured by Toho Titanium Co., Ltd., 2.68 g of anhydrous strontium carbonate (SrCO ₃ , manufactured by Honjo Chemical Co., Ltd.), 0.0209 g of manganese carbonate (MnCO ₃ , 99.9% reagent manufactured by Wako Pure Chemical Industries, Ltd.), silicon dioxide (SiO ₂ , Toshiba Ceramics Co., Ltd., US-85) 0.1091
g, and 0.1644 g of antimony pentoxide (Sb ₂ O ₅ , manufactured by Rare Metallic, 99.99% reagent) was placed in an alumina mortar having an inner diameter of 200 mm, and wet-mixed in an automatic mortar for 3 hours in the presence of ethanol (special grade). The mixture was dried at 130 ° C. The dried mixture was placed in a 90 mm × 90 mm alumina crucible (manufactured by Mitsubishi Mining Cement Co., DFA-PS99), and this was placed in an electric furnace and heated at a heating rate of 180 ° C./h.
Calcination was performed at 150 ° C. for 2 hours.

The calcined product was ground in a mortar, mixed with about 100 ml of a 2 wt% aqueous solution of polyvinyl alcohol (PVA) in an automatic mortar for 3 hours, and dried at 130 ° C. The obtained dried product is pulverized well in a mortar, and the powder containing the PVA is put into a molding die [12.5 mm (diameter) × 35 mm (height)] and molded under a pressure of 1 ton / cm ^2. The article was fired under the following conditions to obtain a molded article made of the porcelain semiconductor composition.

Temperature range Conditions for raising or lowering the temperature Room temperature to 800 ° C 145 ° C / h Heating 800 ° C Hold for 2 hours 800 ° C to 1360 ° C Heating up to 150 ° C / h 1360 ° C Hold for 15 minutes 1360 ° C to 1000 ° C 360 ° C / h Temperature drop 1000 ℃ ~ 550 ℃ 245 ℃ / h Temperature drop 550 ℃ End of temperature control After cooling to room temperature, apply an ohmic silver electrode (manufactured by Degussa) to the disk surface of the tablet-shaped molded product, For 5 minutes to form an electrode, a cover electrode (manufactured by Degussa) was applied on the electrode, and baked at 560 ° C. for another 5 minutes to obtain a sample made of a barium titanate-based porcelain semiconductor composition. .

The composition of the raw materials of the barium titanate-based ceramic semiconductor composition is as follows. (Ba _0.95 Sr _0.05 ) TiO ₃ +0.
0005MnO ₂ + 0.005SiO ₂ + 0.0014Sb ₂ O ₅ As a result of measuring the temperature change of the resistance of this sample, the temperature (Curie point) at which a region showing a positive temperature coefficient of resistance appears is 105.
° C, and the rise width of the resistance was 2.0 digits. At this time, the resistivity at room temperature was a very low resistivity of 3.89 Ω · cm. On the other hand, as shown in FIG. 1 and FIG. 2 which is an enlarged view of FIG. 1, the average particle size on the surface of the obtained porcelain semiconductor composition is 61 μm, which is a fine particle having the same composition as the particle composition. It was confirmed that the crystal grains were present at the grain boundaries, particularly at the grain boundaries where a plurality of grains were associated.

Comparative Example 1 As raw materials, 68.09 g of anhydrous barium carbonate (BaCO ₃ ), 29.02 g of high-purity titanium dioxide (TiO ₂ ), 2.68 g of anhydrous strontium carbonate (SrCO ₃ ), 0.0209 g of manganese carbonate (MnCO ₃ ), and silicon dioxide ( A sample made of a barium titanate-based ceramic semiconductor was obtained in the same manner as in Example 1, except that 0.1091 g of SiO ₂ ) and 0.0881 g of antimony pentoxide (Sb ₂ O ₅ ) were used.

The composition of the raw materials of the barium titanate-based ceramic semiconductor composition is as follows. (Ba _0.95 Sr _0.05 ) TiO ₃ +0.
0005MnO ₂ + 0.005SiO ₂ + 0.00075Sb ₂ O ₅ As a result of measuring the temperature change of the resistance of this sample, the temperature (Curie point) at which a region showing a positive temperature coefficient of resistance appears is 110.
° C, and the rise width of the resistance was 3.3 digits. At this time, the resistivity at room temperature was 27.36 Ω · cm. Further, as shown in FIG. 3, the average particle size on the surface of the obtained porcelain semiconductor composition was 44 μm.

Comparative Example 2 As raw materials, 68.07 g of anhydrous barium carbonate (BaCO ₃ ), 29.01 g of high-purity titanium dioxide (TiO ₂ ), 2.68 g of anhydrous strontium carbonate (SrCO ₃ ), 0.0209 g of manganese carbonate (MnCO ₃ ), and silicon dioxide ( A sample comprising a barium titanate-based porcelain semiconductor composition was obtained in the same manner as in Example 1, except that 0.1091 g of SiO ₂ ) and 0.1175 g of antimony pentoxide (Sb ₂ O ₅ ) were used.

The composition of the raw materials of the barium titanate-based ceramic semiconductor composition is as follows. (Ba _0.95 Sr _0.05 ) TiO ₃ +0.
0005MnO ₂ + 0.005SiO ₂ + 0.0010Sb ₂ O ₅ As a result of measuring the temperature change of the resistance of this sample, the temperature (Curie point) at which a region showing a positive temperature coefficient of resistance appears is 106.
° C, and the resistance rise width was 2.9 digits.
At this time, the resistivity at room temperature was 7.21 Ω · cm. Further, as shown in FIG. 4, the average particle size on the surface of the obtained ceramic semiconductor composition was 46 μm.

Comparative Example 3 As a raw material, 68.03 g of anhydrous barium carbonate (BaCO ₃ ), 28.99 g of high-purity titanium dioxide (TiO ₂ ), 2.68 g of anhydrous strontium carbonate (SrCO ₃ ), 0.0209 g of manganese carbonate (MnCO ₃ ), and silicon dioxide ( A sample made of a barium titanate-based porcelain semiconductor composition was obtained in the same manner as in Example 1 except that 0.1091 g of SiO ₂ ) and 0.1761 g of antimony pentoxide (Sb ₂ O ₅ ) were used.

The composition of the raw materials of the barium titanate-based ceramic semiconductor composition is as follows. (Ba _0.95 Sr _0.05 ) TiO ₃ +0.
0005MnO ₂ + 0.005SiO ₂ + 0.0015Sb ₂ O ₅ As a result of measuring the temperature change of the resistance of this sample, the temperature (Curie point) at which a region showing a positive temperature coefficient of resistance appears is 105.
° C, and the rise width of the resistance was 2.3 digits. At this time, the resistivity at room temperature was 4.84 Ω · cm. On the other hand, as shown in FIG. 5, the average particle size on the surface of the obtained porcelain semiconductor composition was 90 μm.

Comparative Example 4 68.04 g of anhydrous barium carbonate (BaCO ₃ ), 29.00 g of high-purity titanium dioxide (TiO ₂ ), 2.68 g of anhydrous strontium carbonate (SrCO ₃ ), 0.0209 g of manganese carbonate (MnCO ₃ ), silicon dioxide ( A sample comprising a barium titanate-based porcelain semiconductor composition was obtained in the same manner as in Example 1 except that 0.1090 g of SiO ₂ ) and 0.1526 g of antimony pentoxide (Sb ₂ O ₅ ) were used.

The composition of the raw materials of the barium titanate-based ceramic semiconductor composition is as follows. (Ba _0.95 Sr _0.05 ) TiO ₃ +0.
0005MnO ₂ + 0.005SiO ₂ + 0.0013Sb ₂ O ₅ As a result of measuring the temperature change of the resistance of this sample, the temperature (Curie point) at which a region showing a positive temperature coefficient of resistance appears is 102.
° C, and the rise width of the resistance was 2.3 digits. At this time, the resistivity at room temperature was 5.83 Ω · cm. On the other hand, as shown in FIG. 6, the average particle size on the surface of the obtained ceramic semiconductor composition was 56 μm.

Comparative Example 5 As a raw material, 68.01 g of anhydrous barium carbonate (BaCO ₃ ), 28.98 g of high-purity titanium dioxide (TiO ₂ ), 2.68 g of anhydrous strontium carbonate (SrCO ₃ ), 0.0209 g of manganese carbonate (MnCO ₃ ), and silicon dioxide ( A sample composed of a barium titanate-based porcelain semiconductor composition was obtained in the same manner as in Example 1 except that 0.1090 g of SiO ₂ ) and 0.2053 g of antimony pentoxide (Sb ₂ O ₅ ) were used.

The composition of the raw materials of the barium titanate-based ceramic semiconductor composition is as follows. (Ba _0.95 Sr _0.05 ) TiO ₃ +0.
0005MnO ₂ + 0.005SiO ₂ + 0.00175Sb ₂ O ₅ As a result of measuring the temperature change of the resistance of this sample, the temperature (Curie point) at which a region exhibiting a positive temperature coefficient of resistance appears is 106.
° C, and the rise width of the resistance was 1.2 digits. At this time, the resistivity at room temperature was 2.50 × 10 ⁴ Ω · cm. On the other hand, as shown in FIG. 7, the average particle size on the surface of the obtained ceramic semiconductor composition was 1.8 μm.

When the average particle diameter is smaller than that of each of Examples 1 to 5, the influence of the grain boundaries increases,
The resistivity at room temperature is large, and cannot be said to be low resistance.

From the above, the results of [Example 1], [Comparative Example 1] to [Comparative Example 5] are summarized in Table 1 below.

As is clear from Table 1, the use of antimony pentoxide (Sb ₂ O ₅ ) as a semiconducting agent for barium titanate-based elements makes it possible to significantly reduce the resistivity at room temperature. Can be.

FIG. 8 shows the dependence of the resistivity and the average particle size of each of the barium titanate-based ceramic semiconductor compositions on the amount of Sb ₂ O ₅ added. That is, as shown in FIG. 8, the amount of Sb ₂ O ₅ added to the barium titanate-based ceramic semiconductor composition was 0.1%.
In the case of 4 mol%, the resistivity (specific resistance) at room temperature becomes the smallest.

This is, as shown in FIGS. 1 and 2,
Since fine crystal grains having the same composition as the grain composition and not observed in FIGS. 3 to 7 are present at the grain boundaries and at the meeting points where a plurality of grains are meeting, the resistivity is increased. This is because the influence of the grain boundary, which is a factor, has been reduced, and a further lower resistivity has been provided.

Next, a method for measuring various physical properties of samples made of the above various barium titanate-based porcelain semiconductor compositions having different compounding compositions of the raw materials will be described below.

(1) Measurement of Curie point A sample composed of a barium titanate-based porcelain semiconductor composition was attached to a sample holder for measurement, and a measurement tank (MINI-SUBZ
Mounted in ERO MC-810P Tabai Espec Co., Ltd. to measure the change in electrical resistance of the sample with respect to temperature change from -50 ° C to 190 ° C using a DC resistance meter (Multimeter 3478A YHP)
Was used for the measurement.

From the plot of electrical resistance-temperature obtained by measurement,
The temperature at which the resistance value becomes twice the resistance value at room temperature was defined as the Curie point.

(2) Measurement of room temperature resistivity The electrical resistance value of a sample made of the barium titanate-based porcelain semiconductor composition was measured in a 25 ° C. measurement tank using a DC resistance meter (manufactured by Multimeter 3478A YHP).

In the preparation of a sample composed of a barium titanate-based device semiconductor composition, the size (diameter and thickness) of the sample is measured before electrode application, and the specific resistance (ρ) is calculated by the following equation. Rate.

ρ = R · S / t ρ: Specific resistance (resistivity) [Ω · cm] R: Measured value of electric resistance [Ω] S: Area of electrode [cm ² ] t: Thickness of sample [cm] (3 ) Measurement of resistivity rise width Measurement of the change in the electrical resistance of the sample with respect to the temperature change (-50 ° C to 190 ° C) in the measurement of the Curie point is continued until the temperature exceeds 200 ° C, and the resistivity-temperature plot is made. , The resistivity at the time of a sharp rise in electrical resistance at the Curie point was compared with the resistivity at 200 ° C., and the logarithm of the number of digits was defined as the rise width of the resistivity.

In addition, the ceramic semiconductor composition according to the present invention has a low resistivity at room temperature, so that it can be used as a low-resistance PTC element in a circuit having a small current capacity. In addition, electrolytic capacitor protection circuit, color
It can be used for TV automatic degaussing devices, motor starting devices for automobiles, etc., overheating prevention devices for electronic equipment, delay elements, timers, liquid level gauges, contactless switches, relay contact protection devices, etc.

〔The invention's effect〕

As described above, the porcelain semiconductor composition according to the present invention, in the porcelain semiconductor composition having particles and grain boundaries, has the same composition as the composition of the particles, and small particles finer than the particles, This is a configuration provided at the grain boundary centered on.

Therefore, there is an effect that a material having a positive temperature coefficient of resistance at a temperature equal to or higher than the Curie point and having a low resistivity at room temperature can be obtained.

Further, as described above, the method for producing a porcelain semiconductor composition has an effect that a porcelain semiconductor composition having excellent characteristics can be stably obtained.

[Brief description of the drawings]

FIG. 1 to FIG. 8 show examples and comparative examples of the present invention. FIG. 1 is a drawing substitute photograph showing the particle structure of the obtained barium titanate-based porcelain semiconductor composition in Example 1 by a scanning electron microscope. FIG. 2 is a photograph substituted for a drawing, showing an enlarged main part of FIG. 1 by a scanning electron microscope. FIG. 3 is a drawing substitute photograph showing the particle structure of the obtained barium titanate-based ceramic semiconductor composition in Comparative Example 1 by a scanning electron microscope. FIG. 4 is a drawing substitute photograph showing the particle structure of the obtained barium titanate-based ceramic semiconductor composition in Comparative Example 2 by a scanning electron microscope. FIG. 5 is a drawing substitute photograph showing the particle structure of the obtained barium titanate-based porcelain semiconductor composition in Comparative Example 3 by a scanning electron microscope. FIG. 6 is a drawing substitute photograph showing the particle structure of the obtained barium titanate-based porcelain semiconductor composition in Comparative Example 4 by a scanning electron microscope. FIG. 7 is a drawing substitute photograph showing the particle structure of the obtained barium titanate-based porcelain semiconductor composition in Comparative Example 5 by a scanning electron microscope. FIG. 8 is an explanatory diagram showing the dependence of the resistivity and the average particle size of the barium titanate-based porcelain semiconductor compositions obtained in the examples and comparative examples on the amount of antimony pentoxide added.

Claims (3)

(57) [Claims] 1. A porcelain semiconductor composition having particles and a grain boundary, wherein the porcelain semiconductor composition has the same composition as that of the above-mentioned particles, and small particles finer than the above-mentioned particles are provided at a grain boundary centered on an association point. A porcelain semiconductor composition, characterized in that: 2. The porcelain semiconductor composition according to claim 1, wherein the porcelain semiconductor composition is a barium titanate-based porcelain semiconductor composition. 3. A composition comprising a Curie point transfer substance,
1300 ℃ ~ 1400 ℃
A method for producing a porcelain semiconductor composition, characterized by obtaining the porcelain semiconductor composition according to claim 1 or 2 by firing.