JPH04238860A - Production of barium titanate-based porcelain semiconductor - Google Patents

Abstract

PURPOSE:To increase breakdown strength and to reduce resistivity at room temperature by blending a barium titanate-based base composition containing a Curie point transfer substance with a specific semiconductor forming agent and burning. CONSTITUTION:A barium titanate-based base composition containing 0.1-30 wt. mol% Curie point transfer substance is blended with 10-70wt.% Sb2O5 sol adjusted to pH6-2, having 0.02-0.05mum particle diameter, as a semiconductor forming agent and optionally a mineralizer and a voltage-dependent stabilizer in the presence of water in a wet state for 1-25 hours. The blend is dried, calcined at 1,000-1,400 deg.C for 1-3 hours and ground to give a mixture. The mixture is molded and burnt at 1,300-1,400 deg.C for 0-10 hours.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to PTC (Positive T
The present invention relates to a method for manufacturing a barium titanate-based ceramic semiconductor having excellent properties.

0002

[Prior Art] Barium titanate-based porcelain compositions include lanthanum, tantalum, cerium, yttrium, bismuth,
By adding a trace amount (0.5 mol% or less) of oxides such as tungsten, silver, samarium, dysprosium, etc. as a semiconducting agent and firing, a positive temperature coefficient of resistance (P
It has been widely known to obtain a ceramic semiconductor having TC characteristics. Additionally, the electrical properties of the ceramic semiconductor composition can be improved by adding silicon dioxide to a barium titanate ceramic semiconductor composition containing a rare earth element, tantalum, niobium, or antimony and firing it in the presence of oxygen. It has been proposed (Japanese Unexamined Patent Publication No. 53-5
(See Publication No. 9888).

0003

[Problems to be Solved by the Invention] However, in the above conventional method, the content of the semiconducting agent during firing is very low compared to other components, specifically 1/1000 of the total weight. That's about it. For this reason, the semiconductor forming agent must be weighed with high precision. Furthermore, since the content (mixing ratio) of the semiconducting agent is low, it is very difficult to obtain sufficient uniformity during mixing and reaction. For this reason, it is difficult to stably obtain PTC with low resistivity at room temperature, and its physical properties are not uniform, resulting in variations in quality.

0004

[Means for Solving the Problems] In order to solve the above problems and further improve the characteristics, the present inventors have conducted various studies on semiconductor formation through valence control, and various physical properties of the obtained ceramic semiconductor compositions. As a result of measurements, it was found that by using antimony pentoxide (Sb2O5) sol as a semiconducting agent and adding it after adjusting the pH of this sol, the resistivity at room temperature is low and the breakdown voltage is high. The present inventors have discovered a manufacturing method by which a barium titanate-based ceramic semiconductor can be stably obtained, and have completed the present invention.

That is, the method for manufacturing a barium titanate-based ceramic semiconductor according to the present invention is to produce a barium titanate-based ceramic semiconductor obtained by adding a semiconducting agent to a barium titanate-based base composition containing a Curie point transfer substance and firing the mixture. The manufacturing method is characterized in that antimony pentoxide (Sb2O5) sol adjusted to a pH between PH6 and PH2 for the barium titanate base composition is used as the semiconductor agent.

[0006] The above Sb2O5 sol is Sb2O5
This means that ultrafine particles are dispersed in water. In such Sb2O5 sol, the powder diameter of Sb2O5 that is used after being crushed in the conventional manner is approximately 1 μm to 3 μm.
Compared to that, the particle size of the sol is 0.02 μm ~
It is extremely small at 0.05μm, and its component concentration is 1
It can be varied within the range of 0wt% to 70wt%. Also, S
b2O5 sol can be used as a semiconducting agent as well.
It is a semiconducting agent that has lower toxicity than Sb2O3, and since there is no need to handle the powder, there is no harm caused by dust, and it is extremely easy to handle and can significantly improve the working environment.
The pH of the Sb2O5 sol is adjusted to between PH6 and PH2 by adding an acid solution of an inorganic acid such as sulfuric acid or hydrochloric acid whose acid concentration has been adjusted.

[0007] As a more specific manufacturing method, a Sb2O5 sol whose pH has been adjusted is blended into a barium titanate base composition containing a Curie point transfer substance, and at this time, a mineralizing agent is added to this blend. Manganese carbonate (MnCO)
3) Also, silicon dioxide (
SiO2) etc. may be added. In addition, as the Curie point transfer substance, strontium titanate (SrTi
O3), etc. Strontium titanate (S
rTiO3) shifts the Curie point to the lower temperature side, so the addition of SrTiO3 from 0.1 wt mol% to 30 w
By incorporating t mol % into the barium titanate base composition, the Curie point of the obtained barium titanate ceramic semiconductor can be set within a predetermined temperature range. Such formulations are wet mixed in the presence of water in a ball mill for 1 hour to 24 hours, dried and then heated to 1000°C to 1400°C.
The calcined mixture is then calcined for 1 to 3 hours and pulverized. After molding the powder thus obtained in a molding machine of a predetermined shape, the molded product is heated to 1300°C to 14°C.
The barium titanate ceramic semiconductor is obtained by holding at 00° C. for 0 to 10 hours and firing.

[0008]

[Operation] According to the above method, since the Sb2O5 particles added as a semiconductor agent in the sol have a very small particle size, uniform mixing and reaction is possible, and semiconductor formation can be performed more easily. Since the resistivity can be set smaller and variations in quality can be suppressed, it is possible to manufacture a highly versatile low-resistance PTC element that can be used in circuits with small current capacity. In addition, Sb2O5 particles are dispersed in water (
(10 wt% to 70 wt%), it is possible to weigh a large amount of the semiconducting agent, and therefore the error in weighing the semiconductor forming agent can be significantly reduced. For example, when the wt% of Sb2O5 particles in water is 10 wt%, it is possible to weigh 10 times the amount conventionally.

[0009]

[Example] The present invention will be explained in more detail below based on (first example) and (second example), and on the other hand,
As a conventional example for comparison, an example in which antimony pentoxide as a semiconducting agent is used in powder form as in the past (first comparative example)
and P of the antimony pentoxide sol to be added.
An example in which H was adjusted to about 8 was used (second comparative example).

(First Example) Anhydrous barium carbonate (Ba
CO3, Sakai Chemical Co., Ltd. BW-KL) 680.49g
, high purity titanium dioxide (TiO2, manufactured by Toho Titanium Co., Ltd.) 290.01g, anhydrous strontium carbonate (S
rCO3, manufactured by Honjo Chemical Co., Ltd.) 26.79g, manganese carbonate (MnCO3, manufactured by Wako Pure Chemical Industries, Ltd., 99.9g)
% reagent) 0.2086g, silicon dioxide (SiO2
, Rare Metallic Co., Ltd., 99.9% reagent) 1.090
4g of antimony pentoxide sol (Sb2O5, manufactured by Nissan Chemical Industries, Ltd., A-1530ZB, 30.5wt% type PH2.12) 4.6197g were placed in a ball mill with a capacity of 5 liters, and 3.5 liters of water and a diameter of 25
After wet grinding and mixing for 24 hours, the slurry was transferred to a shallow vat and dried at 130°C. After crushing the dry mixture in a mortar, grind it in an alumina crucible (diameter 100 mm).
mm, height 100 mm), heated at a heating rate of 180° C./hour, and calcined at 1150° C. for 2 hours. The calcined product was placed in a vibrating ball mill, and 0.7 liters of water and 20 nylon-coated iron balls with a diameter of 25 mm and 15 nylon-coated iron balls with a diameter of 25 mm were added for 16 hours. ,
Mix by wet grinding, add 150g of 15% (w/w) polyvinyl alcohol (PVA) aqueous solution,
After stirring for 2 hours, the slurry was spray dried with a spray dryer to form granules with a diameter of about 50 μm. The granules were molded into a mold [12.5 mm (diameter) x 35 mm]
(height)] and molded under a pressure of 1 ton/cm2, and the molded product was fired under the following conditions.

Temperature range: Conditions for temperature rise or fall: room temperature to 800°C 14
Temperature increase of 800 °C at 5 °C/hour
Hold for 2 hours 800℃~1360℃
Temperature rise 1360℃ at 150℃/hour
Hold for 15 minutes 1360℃~1000
℃ 360℃/hour temperature drop 1000℃~
550 ℃ 245 ℃/hour temperature drop 55
0°C End of temperature control After cooling to room temperature, an ohmic silver electrode (manufactured by Degussa) was applied to the disk surface of the tablet-shaped molded product.
An electrode was formed by baking at 0°C for 5 minutes, and a cover electrode (manufactured by Degussa) was applied on the electrode.
Baking was further performed at ℃ for 5 minutes to obtain a barium titanate ceramic semiconductor sample.

The composition of the raw materials for this barium titanate ceramic semiconductor is as follows. (Ba0.95Sr0.05)TiO3+0.00
05MnO2+ 0.005SiO2+0.0012S
b2O5 As a result of measuring the temperature change in the resistance of this sample, the temperature at which a region exhibiting a positive temperature coefficient of resistance occurs (Curie point)
was 110°C, and the rise width of the resistance was three digits.

[0013] At this time, the resistivity at room temperature is 4.26Ω.
・cm, and the temperature coefficient of resistance α in the region showing a positive temperature coefficient of resistance is 9.03°C/Ω・cm. Also, as a result of the VI characteristic measurement, the above barium titanate-based material has a disc shape with a diameter of 10 mm and a thickness of 1 mm. The breakdown voltage in a ceramic semiconductor is 2
It was 0V.

(Second Example) Antimony pentoxide sol (
Sb2O5, manufactured by Nissan Chemical Industries, Ltd., A-1550, 48.
A barium titanate-based ceramic semiconductor sample was obtained in the same manner as in Example 1 above, except that 2.9354 g of 7wt% type, PH 5.81) was used.

The composition of the raw materials for this barium titanate ceramic semiconductor is as follows. (Ba0.95Sr0.05)TiO3+0.00
05MnO2+0.005SiO2 +0.0012S
b2O5 As a result of measuring the temperature change in the resistance of this sample, the temperature at which a region exhibiting a positive temperature coefficient of resistance occurs (Curie point)
was 107°C, and the rise width of the resistance was three digits.

[0016] At this time, the resistivity at room temperature is 8.22Ω·c
m, the positive temperature coefficient of resistance α was 8.3° C./Ω·cm, and the breakdown voltage was 16 V, similar to the first example.

(First Comparative Example) Powdered antimony pentoxide (
A barium titanate ceramic semiconductor sample was obtained in the same manner as in Example 1 except that 1.7605 g of Sb2O5 (manufactured by Rare Metallic Co., Ltd., 99.99% reagent) was used.

The composition of the raw materials for this barium titanate ceramic semiconductor is as follows. (Ba0.95Sr0.05)TiO3+0.00
05MnO2+ 0.005SiO2+0.0015S
b2O5 As a result of measuring the temperature change in the resistance of this sample, the temperature at which a region exhibiting a positive temperature coefficient of resistance occurs (Curie point)
is 105℃, and the resistance rise width is approximately 2.3
It was a digit. At this time, the resistivity at room temperature is 4.8Ω
・cm, and the positive temperature coefficient of resistance α is 11℃/Ω・c
m, and the breakdown voltage was 10V.

(Second Comparative Example) Antimony pentoxide sol (Sb2O5, manufactured by Nissan Chemical Industries, Ltd., A-151) was used in place of the antimony pentoxide sol having a pH of about 2 in the first embodiment.
0, 11.3wt% type, PH7.98) 1.24
A barium titanate ceramic semiconductor sample was obtained in the same manner as in Example 1 except that 69 g was used.

The composition of the raw materials for this barium titanate ceramic semiconductor is as follows. (Ba0.95Sr0.05)TiO3+0.00
05MnO2+ 0.005SiO2+0.0012S
b2O5 As a result of measuring the temperature change in the resistance of this sample, the temperature at which a region exhibiting a positive temperature coefficient of resistance occurs (Curie point)
was 110°C, and the rise width of the resistance was three digits.

[0021] At this time, the resistivity at room temperature is 11.8Ω・c
m, and the breakdown voltage was 30V.

[0022] As described above, the first and second embodiments and the first
The results of the second comparative example are summarized as shown in Table 1 below.

[0023]

[Table 1]

As is clear from Table 1, Sb2O5 was used as a semiconductor agent for the barium titanate base composition.
By using the sol, it was possible to increase the breakdown voltage, which is the withstand voltage, compared to the case where Sb2O5 powder was used (see the first comparative example). Also, S to be added
The resistivities at room temperature of barium titanate-based ceramic semiconductors obtained by using various b2O5 sol pHs are shown in Figure 1.
As shown in Figure 2, as the pH decreases, the resistivity also decreases, and in particular, when a Sb2O5 sol of about PH2 was used, the resistivity was lower than that of barium titanate ceramic semiconductor obtained by the conventional method at room temperature. Furthermore, as shown in Figure 1, even when using Sb2O5 sol with a pH of about 6, the resistivity at room temperature shows a low resistance value that poses no practical problem, and as is clear from Table 1, the The voltage was also clearly larger and had better characteristics than before. Based on these facts, Sb with a low pH of 2 to 6
When a barium titanate-based ceramic semiconductor is manufactured using 2O5 sol, a barium titanate-based ceramic semiconductor having a high breakdown voltage and an extremely low resistivity at room temperature can be obtained. It should be noted that it is difficult to prepare an Sb2O5 sol with a pH of 1.5 or less, as shown in a publication (see Japanese Patent Application Laid-open No. 41536/1983).

Furthermore, in the above method, since the particle size of the Sb2O5 particles in the Sb2O5 sol added as a semiconducting agent is very small, uniform mixing and reaction is possible, and semiconducting can be carried out more easily and uniformly. Moreover, the resistivity at room temperature can be set smaller, and physical properties such as withstand voltage are made uniform due to uniform semiconductor formation, and variations in quality are suppressed. Therefore, a barium titanate-based ceramic semiconductor having the above-mentioned excellent properties can be stably produced. As a result, a highly versatile low-resistance PTC element (positive temperature coefficient thermistor) that can be used in a circuit with a small current capacity can be stably manufactured. Also, Sb
Since the 2O5 particles are uniformly dispersed and diluted in water, they can be weighed out in large amounts as Sb2O5 sol, so that the error in weighing the semiconductor forming agent is significantly reduced. In addition, the amount of added Sb2O5 sol particles can be controlled to five decimal places (conventionally, the limit was up to three decimal places). Furthermore, Sb2O5 sol can be made from Sb2O3 powder or Sb2O
The raw material cost is much lower than 5 powder (2 digits to 3 digits).
This makes it possible to reduce the overall cost, as well as being less toxic than Sb2O3 powder, and since there is no need to handle the powder, there is no harm caused by dust, and it is extremely easy to handle, greatly improving the work environment. can be improved.

Here, methods for measuring the various physical properties of the various barium titanate-based ceramic semiconductor samples described above will be explained below. (1) Measurement of Curie point Attach a barium titanate ceramic semiconductor sample to a measurement sample holder, and place it in a measurement tank (MINI-SUBZERO).
MC-810P manufactured by Tabai Espec Co., Ltd.), and the change in electrical resistance of the sample with respect to temperature changes from -50°C to 190°C was measured using a DC resistance meter (Multimeter 3478A manufactured by YHP). From the electrical resistance-temperature plot 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 A barium titanate ceramic semiconductor sample was placed in a measurement tank at 25°C using a DC resistance meter (Multimeter 3478A Y).
The electrical resistance value was measured using a commercially available product (manufactured by HP).

In preparing a barium titanate ceramic semiconductor sample, the size (diameter and thickness) of the sample was measured before electrode coating, and the specific resistance (ρ) was calculated using the following formula:
This was defined as the resistivity. ρ=R・S/t ρ: Specific resistance (resistivity) [Ω・cm] R: Measured value of electrical resistance [Ω] S: Area of electrode [cm2] t:
Thickness of sample [cm] (3) Measurement of rising width of resistivity Temperature change in measurement of Curie point (from -50℃ to 190℃
), the change in electrical resistance of the sample was measured for an additional 20
Continue until the temperature exceeds 0 °C, and in the resistivity-temperature plot, compare the resistivity at the sudden rise in electrical resistance at the Curie point with the resistivity at 200 °C, and calculate the logarithmic ratio of the number of digits. was defined as the rise width of resistivity.

Furthermore, since the barium titanate ceramic semiconductor according to the present invention has a low resistivity at room temperature, it can be used as a low resistance PTC element in a circuit with a small current capacity, for example, as a comparator for a thermal fuse switching power supply. In addition to the above, protection circuits for electrolytic capacitors, color TV automatic degaussing devices, motor starting devices for automobiles, overheating prevention devices for electronic equipment, delay elements, timers, liquid level gauges, non-contact points, etc. Can be used for switches, relay contact protection devices, etc.

[0029]

Effects of the Invention The method for manufacturing a barium titanate-based ceramic semiconductor of the present invention is to manufacture a barium titanate-based ceramic semiconductor by adding a semiconducting agent to a barium titanate base composition containing a Curie point transfer substance and firing the mixture. In this method, antimony pentoxide (Sb2O5) sol adjusted to a pH between PH6 and PH2 is used as the semiconductor agent. This has the effect that a barium titanate-based ceramic semiconductor having a high breakdown voltage and an extremely low resistivity at room temperature can be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in room temperature resistivity of a barium titanate-based ceramic semiconductor obtained with respect to changes in pH of added antimony pentoxide sol in the manufacturing method of the present invention.

Claims (1)

[Claims] [Claim 1] A method for producing a barium titanate-based ceramic semiconductor by adding a semiconducting agent to a barium titanate-based substrate composition containing a Curie point shifting substance and firing the mixture, wherein the semiconducting agent comprises a barium titanate-based ceramic semiconductor having a pH ranging from PH6 to PH2. A method for producing a barium titanate-based ceramic semiconductor, characterized by using an antimony pentoxide (Sb2O5) sol adjusted to a pH between 1.