JP2528356B2 - Conductive ceramics and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive ceramic used as an electrode material for a conductive ceramic porcelain or a ceramic electronic component, and a method for producing the same.

2. Description of the Related Art BaPbO ₃ (hereinafter abbreviated as BPO) having a perovskite structure known as a conductive ceramic material has a resistivity of 10 or less.
It is used as a conductive ceramic because it is as low as ^-4 to 10 ^-3 Ωcm, is resistant to acidified atmosphere, and is inexpensive as a material. In addition, this BPO is used as an electrode material for ceramic electronic components because it has good bondability with other ceramics (dielectrics, semiconductors).

BPO used as a conductive ceramic or a conductive oxide for a conductive paste is generally produced by the following steps.

1. Raw material blending 2. Pre-baking in an oxygen atmosphere (850 ° C, 3 hours) 3. Crushing 4. Pre-baking in an enzyme atmosphere (850 ° C, 3 hours) 5. Crushing 6. Press molding 7. Main firing in an oxygen atmosphere (1,050 to 1,110 ℃, 3 hours) Through the above steps, a conductive ceramic porcelain with a resistivity of 10 ^-4 Ωcm can be made. On the other hand, a raw material for conductive paste The BPO powder to be obtained can be prepared by finely pulverizing the bulk ceramics after the main firing step.

Problems to be Solved by the Invention According to the prior art, as described above, BP having a resistivity of 10 ⁻⁴ Ωcm
In order to obtain O ceramics, it is indispensable to repeat calcination and pulverization in an oxygen atmosphere and to sinter at a calcination temperature of 1,050 ° C or higher in order to obtain a satisfactory sintered body in the main calcination step.

Therefore, the object of the present invention does not require the calcination step in the prior art BPO manufacturing method,
To 950 ° C., preferably 800 to 920 ° C., a manufacturing method and a ceramic structure capable of obtaining a dense sintered body having characteristics similar to those of the prior art, for example, a resistivity of about 10 ⁻⁴ Ωcm at a low firing temperature. It is to provide a sintered body characterized by the above. The purpose is to use a PbO ₂ —BaCO ₃ —CuO-based raw material with an appropriate compounding ratio, that is, a composition formula (Pb _1-x Ba _x ) _1-y Cu _y O
_A binder is mixed with a mixed powder compounded as represented by _z (however, 0.1 ≦ x ≦ 0.6, 0 <y ≦ 0.9, 0.3 ≦ z ≦ 2.0) and pressure-molded. And preferably by firing in the range of 800 to 920 ° C. The ranges of x and y in the above composition formula are determined based on experimental results, and z is a value automatically determined as a result of firing. The sintered body obtained by the production method of the present invention is characterized in that its structural structure is composed of PbBaO ₃ and CuO precipitated in the form of particles therein.

Means and Actions for Solving the Problems According to the production method of the present invention, a molded article obtained by mixing and treating a PbO ₂ —BaCO ₃ —CuO-based raw material at an appropriate mixing ratio as described above is 80
0 to 950 ° C. Since preferably it is calcined in the atmosphere at a temperature in the range of eight hundred to nine hundred and twenty ° C., essential in a manufacturing process for according to the prior art PbO ₂ -BaCO ₃ based material by the conductive ceramic BaPbO ₃ (referred to as BPO) A calcination step is not required, and the firing temperature in the firing step can be as low as 100 to 300 ° C., most commonly 180 to 200 ° C. lower than the latter. Therefore, according to the present invention, for example, production of a conductive ceramic comparable to BPO having characteristics of a resistance value of 10 ⁻⁴ Ωcm can be performed with an appropriate mixing ratio, for example, Pb: Ba: Cu.
By choosing = 3: 3: 4, it was possible to achieve this simply by firing the raw material at 920 ° C in the atmosphere.

Since the method of the present invention using the Ba-Pb-Cu based material and copper or copper oxide in these raw materials BaPbO ₃ sintered is deposited to form a liquid phase, the atoms during the solid-phase reaction It is presumed that the sintering proceeds promptly at a lower temperature than in the prior art in order to facilitate the transfer. That is, in the PbO ₂ —BaCO ₃ —CuO system of the present invention, mainly CuO serves as a solvent to form a liquid phase, and the solid phase reaction proceeds by wetting the surface of the BaCO ₃ crystal grains, while BaPbO ₃ precipitates. , CuO is extruded and precipitates in the form of grains with the crystal growth of BaPbO ₃ .

Therefore, the ceramic sintered body according to the method of the present invention is characterized by the presence of BaPbO ₃ and CuO precipitated in the form of particles in its structure. The peak at the position marked with "●" in Fig. 2 is due to the presence of CuO and is not shown in Fig. 1.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 (1) PbO ₂ (manufactured by Hanai Chemical Co., purity 9
9.5%), BaCO ₃ (Kanto Chemical, purity 99.5%) and CuO
(Manufactured by Kishida Chemical Co., Ltd., purity 99.5%) with a Pb: Ba: Cu molar ratio of l:
m: n (l = 1,2, ... 8; m = 1,2, ... 8; l + m + n = 10), and the composition formula (Pb _1-x Ba _x ) _1-y Cu _y O _z (0.1 ≦ x ≦ 0.6, 0 <y ≦ 0.
9, 0.3 ≦ z ≦ 2.0) was prepared and mixed in ethanol by a ball mill for 24 hours.

(2) A binder (AS-5904: manufactured by Toagosei) is mixed in the obtained mixed powder in an amount of 5 to 6% by weight, and after granulation, 2000 kg
Pressure molding was performed at a pressure of / cm ² .

(3) This molded product was placed on an alumina plate and fired in a pipe furnace at 800 ° C. for 6 hours to produce a sintered body.

(4) The obtained sintered body was cut into a timepiece pattern of about 2 × 2 × 10 (mm), and a silver electrode was baked on this, and the resistivity was measured by the four-terminal method. The measurement results are shown in Table 1.

In addition, in the following table, the indications such as m and ∞ are as follows.

m… Melting ∞… Measurement is impossible because the resistance value is too high As is clear from the results in Table 1, the composition formula (Pb
_1-x Ba _x ) _1-y Cu _y O _z ………… If the value of x in (1) exceeds 0.6, no matter how the Pb: Ba: Cu composition is adjusted, it will be 10 ^-4 to 10 ^-3. It was not possible to obtain a conductive ceramic having a resistivity of about Ωcm. on the other hand,
It was found that the value of y can be varied over a wide range of 0 <y0.9. The value of z is a value automatically determined by the firing conditions, but since the theoretical estimated value is as shown in the relevant column of the table, it can be written as 0.3 ≦ z ≦ 2.0,
This is a supplementary note.

Example 2 The composition ratio of Pb: Ba: Cu was variously determined and the firing temperature was set to 90.
A sintered body was prepared in the same manner as in Example 1 except that the temperature was 0 ° C., and the resistivity was measured. The results are shown in Table 2.

Also from the results in Table 2, x in the above composition formula (1)
It is understood that a conductive ceramic having a resistivity of about 10 ^-4 to 10 ^-3 Ωcm cannot be obtained unless the value of is less than 0.6.

Example 3 The composition ratio of Pb: Ba: Cu was variously determined and the firing temperature was set to 92.
A sintered body was prepared in the same manner as in Example 1 except that the temperature was 0 ° C., and the resistivity was measured. The results are shown in Table 3.

Also from the results of Table 3, x in the above composition formula (1)
It is understood that unless the value of is less than 0.6, a conductive ceramic having a resistivity of about 10 ⁻⁴ to 10 ⁻³ Ωcm cannot be obtained.

Example 4 The same as Example 1 except that the mixing ratio of Pb: Ba: Cu was set to 4: 4: 2 (corresponding to x = 0.5, y = 0.2) and the firing temperature was 940 ° C. Then, a sintered body was produced and the resistivity was measured. It was found that a sintered body having a resistivity of ρ = 9.92 mΩcm was obtained. However, it was confirmed that during firing, it reacted violently with the substrate (alumina).

From the above, it can be said that the temperature that can be adopted for producing the conductive ceramics by the method of the present invention is 800 to 950 ° C. as the widest range, but at 940 ° C., there is already a little too high, 800 It can be concluded that ~ 920 ° C is the optimum temperature range.

Comparative Example 1 (1) Raw material powders PbO ₂ and BaCO ₃ were blended so as to be Pb: Ba = 1: 1 and mixed in ethanol in a ball mill for 24 hours.

(2) The obtained mixed powder was put into an alumina boat, calcined in an oxygen gas-passing pipe furnace at 850 ° C. for 3 hours, taken out of the furnace and pulverized. Furthermore, this calcination and crushing process was repeated again.

(3) The obtained calcined powder was pressure-molded at a pressure of 2,000 kg / cm ² .

(4) This molded product was placed on an alumina plate and fired in a pipe furnace at 1,100 ° C. for 1 hour in the air to obtain a sintered body.

(5) The resistivity of the obtained sintered body was measured in the same manner as in Example 1. The results are shown in Table 4.

Comparative Example 2 (1) Raw material powders PbO ₂ and BaCO ₃ were blended so as to be Pb: Ba = 1: 1 and mixed in ethanol in a ball mill for 24 hours.

(2) 5-6% by weight of binder in the obtained mixed powder
After mixing and granulating, pressure molding was performed at a pressure of 2,000 kg / cm ² .

(3) This molded product was placed on an alumina plate and fired in a pipe furnace at 1,000 ° C. for 6 hours to produce a sintered body.

(4) The resistivity of the obtained sintered body was measured in the same manner as in Example 1. The results are also shown in Table 4.

Comparative Example 3 A sintered body was prepared in the same manner as in Comparative Example 2 except that the firing temperature was 1,100, and the resistivity was measured. The results are also shown in Table 4.

From the resistivity measurement results in Tables 1 to 3, the preferred embodiments of the present invention can be summarized as follows.

(1) According to the present invention, the conductive ceramic having the characteristic of BPO of 10 ⁻⁴ Ωcm shown in Comparative Example 1 based on the conventional method has, for example, the molar ratio of metal elements in the compounding raw material of Pb: Ba: Cu. =
It is obtained by baking a 3: 3: 4 sample at 920 ° C. for 6 hours in the atmosphere.

(2) For example, the metal element molar ratio is Pb: Ba: Cu = 4: 4: 2,
Or 92: 3: 4: 3, or 2: 2: 6
Bake at 0 ° C or Pb: Ba: Cu = 5: 4: 1 or 4:
By firing a raw material having a composition of 4: 2 or 3: 3: 4 at 900 ° C. in the atmosphere, a conductive ceramic having substantially the same characteristics as BPO (calcined at 1,100 ° C.) shown in Comparative Example 3 is obtained. be able to.

(3) Further, for example, the molar ratio of the metal elements is Pb: Ba: Cu = 5:
A raw material having a composition of 3: 2, or 3: 4: 3, or 3: 2: 5, or 2: 2: 6 is calcined in air at 900 ° C., or Pb: Ba: C is used.
u = 5: 4: 1, or 4: 4: 2, or 4: 2: 4, or 3: 3: 4,
Or a raw material having a composition of 2: 3: 5 or 2: 2: 6 in the air 80
BPO shown in Comparative Example 2 was obtained by firing at 0 ° C. for 6 hours.
It is possible to obtain conductive ceramics having characteristics almost equivalent to those of the 10 ^-3 Ωcm generation (calcined at 1,000 ° C).

Effects of the Invention As described above, in the method for producing a conductive ceramics of the present invention, there is no need for a calcination step as compared with the case of producing BaPbO ₃ using a Ba-Pb-based oxide raw material, and only main firing is required. The desired conductive ceramics sintered body can be manufactured with, and it becomes possible to sinter at a firing temperature lower than 100 ° C, and if the proper raw material mixture ratio is selected, the firing rate (sintering to theoretical density Density ratio) is also for BaPbO ₃
For example, Pb: Ba: Cu = 3: for 85.9% (for example, Comparative Example 1).
A denser sintered body can be obtained such as 92.1% at 3: 4.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction pattern of BPO of Comparative Example 1,
FIG. 2 is a diagram showing an X-ray diffraction pattern in the case of firing at 920 ° C. with the compounding ratio Pb: Ba: Cu = 3: 3: 4 of the present invention. The symbol ● in the figure is a symbol added to indicate the presence of CuO.

Claims (2)

(57) [Claims] 1. A composition formula (Pb _1-x Ba _x ) _1-y Cu _y O _z (where 0.1 ≦ x ≦ 0.6,0 <y is used for a PbO ₂ —BaCO ₃ —CuO-based raw material.
≦ 0.9, 0.3 ≦ z ≦ 2.0), which is a sintered body compounded as expressed by PbBaO ₃ and CuO precipitated in the form of particles into the sintered body. Ba-Cu
Series conductive ceramics. _{2. A} composition formula (Pb _1-x Ba _x ) _1-y Cu _y O _z (where 0.1 ≦ x ≦ 0.6,0 <y is used for the PbO ₂ —BaCO ₃ —CuO-based raw material.
≦ 0.9, 0.3 ≦ z ≦ 2.0), mixed with a binder to the mixed powder, pressure-molded, and calcining the molded product in the range of 800 to 950 ° C. in the atmosphere. −Ba
-Method for producing Cu-based conductive ceramics.