JPS63215545A - Manufacture of high temperature ptc material - 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 [Field of Industrial Application] The present invention relates to a method for producing a high-temperature PTC material.More specifically, the present invention relates to a method for producing a high-temperature PTC material. , these are collectively referred to as "BaPbO5-based compositions"), and have positive resistance temperature characteristics (PT
C characteristics).

[Conventional technology]

Recently, as is well known, PT made of BaPbO5-based composition
Many C materials have been proposed. - For example, in JP-A-60-118662, the composition is BaPb+, x
Ot+yPbo (0<xfo,2, (1,yi
A high temperature PTC material consisting of: o, 2) is disclosed. This high-temperature PTC material can be manufactured by calcining BaC0, and pb,o powder as raw materials to obtain BaPbO powder, then mixing this powder with pbo powder, and firing in an oxygen atmosphere. can. This high-temperature PTC material has a specific resistance (ρ) value of 10-4 to 10-3 Ω·value and excellent conductivity, making it possible to use large amounts of power and
The temperature change point (resistance change point; it is the so-called Curie point, henceforth referred to as CP) is approximately 750°C, so it can be used in a high temperature range (750 to 850°C) that is impossible with conventional BaTi01-based PTC materials. It can be used in In addition, as another method to obtain BaPbO3 powder, BaC01
A method is known in which PbzO4 and PbzO4 are wet-mixed, and the resulting mixture is dried and then calcined.

The production of these BaPbO1 powders is generally called a dry method or a solid phase method.

[Problem that the invention seeks to solve]

There are various problems in producing BaPbO* powder using a dry process. First, in the drying process after wet mixing, separation occurs due to the difference in specific gravity, so the aPbO
: It is virtually impossible to obtain +, and compositional fluctuations occur.

Although this problem can be solved by using a flash freezing method during drying, this method is complicated in operation and is not practical in terms of cost. Second, in the dry method, it is easily affected by the mixing state of raw materials, particle size, etc. during calcination, and therefore it is impossible to obtain a complete amount of aPbO in one calcination, and usually twice or more. or more calcination is required. For these reasons, the dry method not only requires a complicated process but also
The scattering causes compositional fluctuations, which affects the characteristics of the product.In addition, due to the difficulty of sintering of the material itself, when manufacturing electrode-2 thick film PTC materials by making it into a paste,
It is necessary to perform firing at a temperature of ℃ or higher, and the above-mentioned PbO
This will further accelerate problems such as compositional fluctuations due to scattering.

[Means for solving problems]

In producing BaPbO+ powder, the present inventors
It has been found that the above-mentioned problems can be solved if an alkoxide method is used instead of a dry method, that is, if a metal alkoxide is used as a starting material and a mixed solution thereof is hydrolyzed.

In other words, the present invention is a method for producing a high-temperature PTC material consisting of a BaPbO-based composition using an alkoxide containing Ba as a main component and an alkoxide containing Pb as a main component as starting materials.

The method of the present invention can be applied, for example, to the formula: Ba (OR) z (
(R in the formula represents a methoxy group, ethoxy group, propoxy group, etc.) and a Ba alkoxide represented by the formula:
Pb alkoxide represented by Pb (OR) t (R in the formula is the same as defined above) is mixed in a suitable organic solvent solution, and at that time, Ba and Pb are adjusted to have a predetermined composition ratio. This can be advantageously carried out by then hydrolyzing the obtained mixed solution and calcining the produced powder. After calcination, a series of treatments such as crushing, granulation, and molding can be performed using commonly used techniques.

In the method of the invention, various additives can be included in the BaPbO3-based composition in order to control the properties of the resulting PTC material. For example, BaPbO, TiO□ to control the resistance change point (CP).

It can contain Zr0z and/or mixtures thereof.

The introduction of TiO2 and/or Zr0t
bO, this can be done by adding them during the pulverization of the calcined product (or by adding Ti and/or when mixing the starting materials).
Alternatively, it may be carried out by mixing together in the form of Zr alkoxide. In addition, in order to improve the density of the obtained sintered body, for example, S
A flux (sintering aid) such as iO2, 5i3Nn, SiC, etc. can be added. Furthermore, in order to control the specific resistance (ρ2°) at room temperature without changing the CP, a compound containing an element of Group 1A of the periodic table as a main component, such as LizCOs, NazCO3°K, GO3, etc.
Or a compound whose main component is an element in group 5A of the periodic table,
For example, VzOs, NbzOs + Ta2es, etc. can be added.

〔Example〕

The present invention will be explained in more detail by way of examples.

Barium ethoxide Ba (OC2H8) z was obtained by directly reacting the metal barium with ethanol (anhydrous).

In addition, lead ethoxide Pb (OCf
fiHs)t was obtained. Ba (OCJs) and Pb
(OCzfls) After dissolving each of z in ethanol and leaving the solution, the Ba/Pb ratio was 40/60 (Example 1
), 45155 (Example 2), 50150 (Example 3)
, 55/45 (Example 4) and 60/40 (Example 5), and mixed thoroughly under reflux.

After mixing, the resulting mixed solution was hydrolyzed and the resulting powder was dried. The dry powder was then calcined at 800° C. for 2 hours in an oxygen atmosphere. Subsequently, the mixture was ground in a ball mill for about 12 hours and dried to obtain a BaPbO composition.

An appropriate amount of polyvinyl alcohol (PVA) was added to the BaPbO5-based composition obtained as described above and granulated, and the size: 5.5 X2. Molded into OX 55 (Ilm). The obtained molded sample was placed on a fired ZrO2 coating and fired in an oxygen atmosphere at 800-1000°C. Next, the fired sample was polished to a size of about 4. OXl, 5
x40 (mm), PT paste was baked on this sample as an electrode, and the change in resistivity from room temperature to about 1000°C was measured by the DC four-terminal method. The results shown in Table 1 below were obtained.

Samples were prepared using the same method as described in Examples 1 to 5 above. However, in this example, in order to shift the resistance change point CP to the high temperature side, BaPbO3 with a different Ba/Pb ratio is used.
TiO□ or ZrO was added to the sample in the amount shown in Table 1 below. TiOz or ZrO was added while the calcined powder was being ground in a ball mill.

The results shown in Table 1 below were obtained.

U2 medicine (comparative example) Three types of Ba/Pb ratio: 40/60 (Example 12),
Samples were prepared using the same procedure as described in Examples 1-5 above using 50150 (Example 13) and 60/40 (Example 14). However, for comparison, the BaPbO calcined product used in this example was prepared not by the alkoxide method but by the following conventional dry method.

BaC0 and Pb30. as raw materials. was used. After quantifying these raw materials in a predetermined composition ratio, they were wet mixed in a ball mill at °C. After drying the resulting mixture, it was calcined at 900° C. for 2 hours in an oxygen atmosphere. The obtained BaPbO
3 was further wet-pulverized in a ball mill, dried, and then calcined under the same conditions as above. After pulverizing these BaPbO, they were granulated, molded, and sintered.

When the resistivity change of the obtained sample was measured by the DC 4-terminal method in the same manner as in Examples 1 to 5, the results shown in Table 1 below were obtained.

(2) Long open plate (comparative example) Samples were prepared using the same method as described in Examples 12 to 14 above. However, in this example, in order to compare with Examples 6 to 11, Ti0z or Zr0t was added in the amounts listed in Table 1 below. The results obtained are shown in Table 1 below.

Comparative Example Samples were prepared using the same method as described in Examples 12 to 14 above. However, in this example, the BaPb0 explained so far
To contrast with z, BaTi0z (Example 21) and Ba
o, 3sPbo, hsTiOs (Example 22) was used. The results obtained are shown in Table 1 below. In the following table, the numbers listed in the Ti0t and Zr0z columns of composition 1) are the amounts used per 1 mole of BaPb0z (expressed in moles in terms of titanium atoms or zirconium atoms). . Judgment ゜) is ≧9 regarding relative specific gravity.
0% was marked as ○, and <90% was marked as ×.

From the results listed in Table 1 above, the following effects of the present invention are clear: 1) By using the alkoxide method in preparing and mixing the starting materials, excellent BaP can be produced that is uniform and free from compositional fluctuations.
A bO, based composition is obtained. This makes it possible to easily prepare a desired BaPbO3-based composition with good reproducibility compared to the conventional method (dry method). In particular, the calcination temperature was 900°C in the conventional method, but it can be lowered to 800°C by the method of the present invention, eliminating the scattering of PB during calcination, and therefore making it possible to obtain a composition without compositional fluctuations. It becomes possible.

2) BaP obtained by the alkoxide method according to the method of the present invention
The b0z calcined product has fine particles and superior crystallinity compared to the conventional method, and the firing temperature is 1050℃ in the conventional method.
Although the temperature is high at ~1200°C (Examples 12 to 20), the method of the present invention makes it possible to significantly lower the temperature to 800~1000°C as shown in Table 1. This also improves properties such as specific gravity, making it possible to reduce costs.

That is, it is thought that the BaPbO powder obtained by the method of the present invention has fine particles and excellent crystallinity, and thus has greatly improved properties compared to the conventional method.

〔Effect of the invention〕

According to the present invention, as is clear from the above description, a high quality aPbO,l-based composition that is uniform and free from compositional fluctuations can be obtained. Further, in the method of the present invention, since a uniform and fine mixture is obtained, the reactivity is improved, and therefore the calcination temperature can be lowered by 100° C. or more compared to the conventional method. Furthermore, in the method of the present invention, highly reactive Ba
Since a PbO-based calcined product is obtained, the sintering temperature can be lowered by 100° C. or more compared to conventional methods, and properties such as specific gravity are improved.

Claims (1)

[Claims] 1. BaP using an alkoxide containing Ba as a main component and an alkoxide containing Pb as a main component as a starting material.
A method for producing a high-temperature PTC material comprising a bO_3-based composition. 2. Mix an alkoxide containing Ba as a main component and an alkoxide containing Pb as a main component so that Ba and Pb have a predetermined composition ratio, hydrolyze the resulting mixed solution, and calcinate the resulting powder. The manufacturing method according to claim 1.