JPH012301A - Method for producing positive temperature characteristic materials - 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 Application Field] The present invention is based on barium leadate (B), which is dense and has excellent durability.
The present invention relates to a method for manufacturing a positive temperature characteristic material based on a'PbOs).

[Prior art]

BaPbO, a positive temperature characteristic material, has a Curie point at a high temperature of around 700"C, and the electrical resistance value changes rapidly at the Curie point. So-called positive temperature characteristic (PT)
C characteristic) (Japanese Patent Application Laid-Open No. 6O-118662). And take advantage of its characteristics.

It is widely used in constant temperature/heating elements, temperature sensors, and overcurrent protection elements in electrical circuits.

Conventionally, BaPbO5-based positive temperature characteristic materials have been manufactured by pressureless sintering of raw material compositions, but since this material is difficult to sinter, bores remain in the sintered body, resulting in a dense sintered body. was difficult to obtain.

Obtaining a dense sintered body not only increases the strength, but also has the advantage that the PTC properties change less over time due to the influence of the atmosphere in which it is used.

Therefore, as a countermeasure to this problem, hot isostatic pressing (HIP)
Attempts have been made to use hot press. However, since the conventional treatment is carried out in Ar (argon) and N2 (nitrogen), BaPbO3 is reduced during this sintering process.
Since the perovskite structure is destroyed, there is a problem that PTC characteristics and durability deteriorate.

[Problems to be Solved] The present invention was created as a result of repeated studies, particularly regarding the sintering method, to address the above-mentioned conventional problems. Excellent. B
The present invention aims to provide a method for manufacturing an aPbO5-based positive temperature characteristic material.

[Means for solving the problem] The present invention is characterized in that a BaPbO5-based composition is subjected to hot isostatic pressing under conditions of an oxygen concentration of 1% or more, a pressure of 10 atm or more, and a temperature of 700 to 1100°C. A method for producing a positive temperature characteristic material is provided.

In the present invention, the BaPbO5 positive temperature characteristic material is
The main component is BaPb0z, to which excess PB (lead) is added to increase the resistance change rate, and Ti0□ (titanium oxide) or Zr is used to move the 1 resistance change point to the high temperature side.
There are also those to which 0z (siliconium oxide) is added.

In addition, as the B a P b Oz composition, B
aC03 (barium carbonate) and PbC0, (lead carbonate).

Furthermore, as the case may be, the calcined powder of the raw material mixture mixed with the above-mentioned additives can be used either in the form of a fired body that has been fired once at a high temperature or in the form of a molded body.

What is hot isostatic pressing (hereinafter referred to as HIP)?

The composition is placed in a high-pressure container, and the powder is compression-molded and sintered at high temperature and high pressure.

The conditions for this press are that the oxygen (0□) concentration in the atmosphere is 1
% (volume) or more, the pressure is 10 atmospheres or more.

The temperature is 700-1100'C. Here, if the 0□ concentration is lower than 1%, the above composition may be reduced during the HIP treatment and the PTC properties may deteriorate. Also,
If the pressure is lower than 1O atm, the HIP effect is small and pores remain, making it impossible to obtain a dense sintered body.
If it is lower than 0°C, there is no sufficient HIP effect, while if it exceeds 1100°C, superphosphoric acid will occur and the resistance will increase significantly.

Furthermore, even within the above range, the 0□ concentration is 5% or more.

When the pressure is 1000 degrees Celsius or higher and the temperature is 800-1000° C., a particularly dense positive temperature characteristic material can be obtained.

Further, the above-mentioned oxygen atmosphere can also be configured together with a gas such as Ar or N. Regarding the method of increasing temperature and pressure, as shown in the examples, temperature and pressure increases may be performed simultaneously, or firing may be performed after increasing the pressure (pre-pressurization), or pressure may be increased after firing (pre-calcination). Additionally, the 9 compositions may be encapsulated in glass, platinum, etc. capsules or without encapsulation.
Subject to HIP treatment.

2. The BaPbO-based positive temperature characteristic material (hereinafter referred to as PTC material) obtained by the method of the present invention is A3j(iI)-P
Form an electrode of d (palladium) or the like.

Provided for use as a PTC material.

Effects and Effects] In the present invention, since the HIP treatment is performed in an oxygen-containing atmosphere at high temperature and high pressure as described above, the perovskite structure is not destroyed and a dense aPbos-based PTC material can be obtained. Therefore, 5 P
TC material is an excellent PTC material that has excellent high-temperature durability and high strength, and has low specific resistance at room temperature and a large rate of change in resistance.
Demonstrate characteristics.

〔Example〕

First example A fired body was created as a BaPbO5-based composition.

Next, this is processed into 9oo' by HIP processing according to the present invention.
A BaPbO-based PTC material was produced by sintering at c.

First, the above composition was created as follows.

That is, Ba (NOx)z (barium nitrate)
The aqueous solution and Pb (NO3)z (lead nitrate) aqueous solution were mixed so that the Ba/Pb molar ratio was 45155,
The mixed solution was added dropwise to an (NH4)z COs (ammonium carbonate) aqueous solution while stirring with a stirrer.

A coprecipitate of BaC0, Pb, and COs was obtained. After drying the obtained coprecipitate, it was calcined at 800°C for 3 hours in an oxygen atmosphere. This calcined product was pulverized, calcined again at 800'C in an oxygen atmosphere for 3 hours, and pulverized to obtain a BaPbO5 powder.

Next, a binder was added to this BaPbO-based composition powder, and it was formed into a 55 x 5 x 1 ms long plate shape and heated at 900°.
C, fired in an oxygen atmosphere for 3 hours.

This fired body corresponds to a BaPbO3-based composition in the present invention.

Next, the fired body as the above composition was treated with 1 to 20% of Ol
Table 2-(
Under the conditions shown in 1), holding for 3 hours, increasing the pressure and temperature simultaneously, 1 (JP treatment was carried out to produce a BaPbO1-based PTC material).Next, Ag-Pd' was applied to this plate-shaped PTC material.
N, paste print the pole.

It was formed by baking to produce a PTC material element.

Properties of the obtained PTC materials Na 1 to 7, namely relative specific gravity (%), bending strength (kg r /m”), specific resistance (
Ω-cm), resistance change point (° C.), resistance change rate, high temperature weight change rate (%), and the determination results described below are shown in Table 2-(1) and (2).

In the same table, relative specific gravity is the ratio (%) based on the theoretical specific gravity, and specific resistance (Ω-cm) is at 20°C in the atmosphere.
The resistance change rate is 85% from room temperature.
A relationship diagram (see drawing) between temperature and specific resistance when heated to 0°C was obtained, and the ratio of the maximum resistance value to the minimum resistance value G at that time was calculated.

Further, the high temperature weight change rate is used to check high temperature durability, and is calculated as the weight change rate (%) of around 1 when the PTC material is left at 700°C for 1000 hours.

Therefore, in order to evaluate the above-mentioned BaPbO3-based PTC material, we established the criteria shown in Table 1, which also takes practicality into account, and judged the quality of the evaluation based on Q and x shown in the same table.
2).

In addition, as a comparative example, the same composition (fired body) as above was prepared under the HIP conditions shown in Table 2-(1) in an atmosphere of Ar, N, or Ar and a small amount of 0□. Pressure sintered,
BaPbO, based PTC materials C1-C4 were manufactured. These were also measured and evaluated in the same manner as above.

or. 1. Seri,. □9,7□25=(+1. (21&,
:picture.

Ta.

As is known from Table 2-(]) and (2), BaPbO5-based PTC materials Nos. 1 to 7 produced by the method of the present invention all exhibit performance on the basis of the criteria shown in Table 1, and are dense and dense. It can be seen that it has excellent strength, high temperature durability, and excellent PTC properties.

On the other hand, in the comparative example, an atmosphere containing only Ar (C
1) was a defective product with a large specific resistance and an extremely small rate of change in resistance. The reason for the high specific resistance is that the above composition was reduced during the HIP treatment.

Also, Ar+0. The atmosphere ones (C2-C4) are also Ol
Because of the small amount or low pressure, the product was defective, such as lacking high-temperature durability.

Second example 20%02 + A r (or N,) atmosphere, pressure 1
000 atm, and by changing the temperature, H as shown in Table 3-(1)
Depending on the IP conditions, BaPbO5-based PTC material N[lB ~ 1
2 was manufactured. ! As the product No. 11, the same fired body as in the first example was used. The results are shown in Table 3 (]) and (2) in the same way as Table 2 - (+) and (2).

Also, for comparison, the same table shows the 02 atmosphere as above, but the HIP temperature is as low as 600°C or 12
The results for cases as high as 00°C (C5, C6) are
It was shown in the same way.

As is known from the same table, two Rapbos produced by the method of the present invention,
It can be seen that all the PTC materials exhibit excellent properties.

Third Example A molded body was used as a BaPbO5-based composition, and the pressure was varied in various 02 atmospheres at 900°C.

According to the HIP conditions shown in Table 4-(1), BaPbO: +
PTC materials Nos. 13 to 17 were manufactured. The composition was shown in the first example. A molded body in the form of a long and narrow plate was used. Table 4-(1) and (2) show the results in the same manner as above.

In addition, for comparison, the above-mentioned molded body is used in the same table, and Ar
only or low o, fA degree, or low pressure (C7~
The results for 10) were similarly shown.

As can be seen from the same table, the BaPb0z-based PTC material obtained by the method of the present invention also has the following properties even when a molded body is used.

It can be seen that both exhibit excellent properties.

Fourth Example A molded body was used as the BaPbO3 composition, and 02tAr
(or Nz) atmosphere, changing the temperature at too atmospheric pressure, BaPb
O1-based PTC materials Nos. 18 to 22 were manufactured. The composition was shown in the first example.

A molded body in the form of a long and narrow plate was used. Table 5-F+), (2)
To.

The results are shown in the same manner as in 1fI.

For comparison, the same table also shows the results obtained when the above-mentioned molded body was used and the temperature was too low or too high (C1l, Cl2).

As can be seen from the same table, even when a molded body is used, the BaPbO1-based PTC material produced by the method of the present invention has the following properties.

It can be seen that all of them exhibit excellent properties.

Next, the N11l according to the present invention and the comparative example] A
Ar atmosphere HIP N (LCI, and pressureless sintering N
[Resistance-temperature characteristics for each PTC material of IC9 are shown in the figure. In this figure, the horizontal axis is temperature (°c), the HM axis is specific resistance (Ω-c+n), and the resistance-temperature N characteristic is shown by a curve with the same symbol as the above-mentioned material.

As can be seen from the figure, both N11l and N(lc9) exhibit PTC characteristics at about 700°C.

However, the Na 1 of the present invention exhibits a large rate of change when it rises sharply, whereas the Na 1 of the comparative example 81'i
C9 also has a low specific resistance and the above 1) T C characteristics [1
Sai. In addition, the comparative example Nn C1 has a PTC characteristic of 5 h.
Not indicated.

[Brief explanation of the drawing]

The figure shows the B a P b O:+ system P”F according to the example.
It is a figure which shows the PTC characteristic of C material t4.

Claims (3)

[Claims] (1) BaPbO_3-based composition with an oxygen concentration of 1% or more,
1. A method for producing a positive temperature characteristic material, comprising performing hot isostatic pressing under conditions of a pressure of 10 atm or more and a temperature of 700 to 1100°C. (2) The method for producing a positive temperature characteristic material according to claim 1, wherein the oxygen concentration is 5% or more, the pressure is 100 atm or more, and the temperature is 800 to 1000°C. (3) The method for producing a positive temperature characteristic material according to claim 1, wherein the BaPbO_3-based composition is a fired body or a molded body.