JP3323076B2 - Conductive ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support member for a magnetic disk substrate such as a spacer, a shim and a hub incorporated in a magnetic recording apparatus, a nozzle for electrodeposition coating, other components for removing static electricity, and a semiconductor / thin film process. And a conductive ceramic used for a resistance evaluation probe, a ceramic sensor, a ceramic heater, and the like.

[0002]

2. Description of the Related Art Conventionally, ceramics used as conductive ceramics include silicon carbide ceramics and perovskite ceramics such as lanthanum chromite, which are used for ceramic heaters and ceramic sensors.

In addition, conductive ceramics obtained by adding conductive metal oxides, metal nitrides, metal carbides and the like to ceramics for structural component materials have also been developed. For example, TiO ₂ , TiC, Ni
Conductive ceramics such as alumina and zirconia which are fired in a reducing atmosphere by adding O, CoO, etc. are known (JP-A-2-295509, JP-A-1-24333).
No. 88).

[0004]

However, since the above-mentioned silicon carbide-based ceramics are difficult to sinter, they must be fired in a non-oxidizing atmosphere and at a temperature of 2000 ° C. or higher. Isostatic Press (HIP)
Therefore, there is a problem that productivity is low and the cost is high because of the necessity of performing.

[0005] Perovskite-based ceramics and alumina- and zirconia-based conductive ceramics to which NiO, CoO, etc. are added as a conductivity-imparting agent are also hot pressed or hot isostatically pressed (HI) as well as silicon carbide-based ceramics.
P), or sintering in a reducing atmosphere must be performed, resulting in poor productivity. Moreover, perovskite ceramics generally have a bending strength of 10 kg / mm.
^It was lower than ² and was unsuitable as a structural component material.

On the other hand, when used as a conductive material, it is generally required to have a volume resistivity of less than 10 ¹¹ Ω · cm to remove static electricity. Alumina-based conductive ceramics to which ₂ or TiC is added can only obtain a resistance of about 10 ¹² Ω · cm, and it is difficult to obtain a conductive ceramic having a volume resistivity of less than 10 ¹¹ Ω · cm. Was.

Therefore, the present invention has mechanical properties that are easy to manufacture and can be used as a structural component material,
It is an object of the present invention to obtain a conductive ceramic having a volume resistivity of less than 10 ¹¹ Ω · cm.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention mainly comprises a composite oxide of MgO and SiO ₂ and contains chromium oxide and / or titanium oxide and has a volume resistivity of 10%. Less than ¹¹ Ω · cm and bending strength is 10
It is characterized by a conductive ceramic of not less than kg / mm ² .

[0009]

Embodiments of the present invention will be described below. The conductive ceramic according to the present invention comprises MgO and Si.
It is mainly composed of a composite oxide of O ₂ , contains chromium oxide and / or chromium oxide as a conductivity-imparting agent, has a volume resistivity of less than 10 ¹¹ Ω · cm, and has a flexural strength of 10 kg / mm. ^{It has two} or more mechanical properties.

Here, the main component of the composite oxide of MgO and SiO ₂ is mainly Mg ₂ SiO ₄ in the final sintered body.
(Forsterite), and MgSiO ₃
(Enstatite). Usually Mg ₂
Ceramics consisting of SiO ₄ alone is 15 kg / mm ²
Although it is an insulating material having a degree of bending strength, the present inventor has applied chromium oxide (Cr ₂ O ₃ ) and / or
Alternatively, it has been found that conductivity can be obtained by adding titanium oxide (TiO), and its volume resistivity is set to 10 ¹¹ Ω.
・ It is less than cm.

That is, chromium oxide (Cr ₂ O ₃ ) has a resistance of about 10 ⁷ Ω · cm at room temperature, and titanium oxide (TiO) has a resistance of about 10 ^-4 Ω · cm at room temperature. Therefore, a conductive ceramic having a volume resistivity of less than 10 ¹¹ Ω · cm can be obtained by appropriately adjusting the amounts of these additives. Therefore, since the charged static electricity can be quickly released and removed, a supporting member such as a spacer, a shim, a hub for positioning and holding a plurality of magnetic disk substrates incorporated in the magnetic recording apparatus at a predetermined interval, or a magnetic member. It can be suitably used as a guide member supporting the running of the tape, a component for removing static electricity such as a nozzle for electrodeposition coating used for painting of automobiles, etc., and a ceramic heater, a ceramic sensor, or a semiconductor / thin film process resistance. It can also be used as an evaluation probe.

However, when the content of chromium oxide (Cr ₂ O ₃ ) and / or titanium oxide (TiO) is increased to obtain conductivity, mechanical properties such as bending strength are greatly reduced, and the above-mentioned applications are not considered. If used, it may be damaged, making it difficult to use as a structural component material. Therefore, it is necessary for the conductive ceramic to have a bending strength of 10 kg / mm ² or more.

The presence of each component constituting the conductive ceramic can be determined by confirming the presence of the peak of each component when analyzed by X-ray diffraction. In the final sintered body, MgO and S
as a reaction product obtained by reaction of the composite oxide of iO ₂ and the conductive material, MgCr ₂ O when the MgTi ₂ O ₅ when the titanium oxide (TiO) is present, the presence of chromium oxide (Cr ₂ O _{3) 4} are produced as reactants, respectively, and these reactants may be present in the conductive ceramic without any problem.

Further, in the present invention, iron oxide (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ) is used as another conductivity-imparting agent in the above-mentioned chromium oxide (Cr ₂ O ₃ ) and / or titanium oxide (TiO).
Can be added in place of a part of.

In order to obtain such a conductive ceramic of the present invention, Mg ₂ SiO ₄ or MgSiO ₃ is prepared as a composite oxide of MgO and SiO ₂ , and chromium oxide (Cr ₂ O 4) is used as a conductivity-imparting agent. ₃ ) and / or
Alternatively, titanium oxide (TiO) is prepared. And the above M
g ₂ SiO ₄ or MgSiO ₃ complex oxide of 40
Chromium oxide (Cr ₂ O ₃ ) and / or
Alternatively, titanium oxide (TiO) is added in a range of 60 to 10% by weight.

Here, the reason why the amount of the conductivity-imparting agent is limited as described above is that if it is less than 10% by weight, chromium oxide (Cr ₂ O ₃ ) and / or titanium oxide (TiO) are added. Less effective, volume resistivity is 10 ¹¹ Ω
・ Because it cannot be less than cm,
If the content is more than 10% by weight, the mechanical strength is significantly reduced, so that it cannot be used as a structural component material.

Next, after the added and mixed raw materials are filled in a mold and formed into a predetermined shape, the raw materials are mixed in an air atmosphere at 1200 to 1200 m.
By sintering at a temperature of 1300 ° C. for about 1 to 2 hours, the conductive ceramic of the present invention can be obtained.

As described above, the conductive ceramics of the present invention can be fired in the air atmosphere, and the manufacturing process is simplified since hot pressing or hot isostatic pressing (HIP) is not necessarily required. , The cost can be reduced. In the present invention, the firing atmosphere is not limited to the air atmosphere, but may be a non-oxidizing atmosphere or a reducing atmosphere.

[0019]

Embodiments of the present invention will be described below. Example 1 Forsterite (Mg ₂ SiO ₄ ) was prepared as a composite oxide as a starting material, and chromium oxide (Cr ₂ O ₃ ) was prepared as a conductivity-imparting agent, and the addition amount was changed as shown in Table 1. I let it. Each raw material was charged into a container using water or an organic solvent as a solvent, paraffin wax was charged as a binder, mixed for about 1 hour, and the slurry was dried to prepare a secondary raw material. Next, the obtained secondary raw material is formed into a predetermined shape by a dry press at a forming pressure of 1.0 ton / cm ² , and then, in an air atmosphere, from 1200 to 1
The firing was performed at a temperature of 300 ° C. for about 1 to 2 hours.

Then, the obtained ceramics are made to have a diameter of 60.
After grinding to a size of 2 mm × 2 mm in thickness to measure the volume resistivity, the flexural strength was measured by a three-point bending test, and the volume resistivity was less than 10 ¹¹ Ω · cm and the flexural strength was 10 kg / Those having mm ² or more were regarded as excellent.

The results are as shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

As a result, the sample No. In No. 7, since the content of chromium oxide (Cr ₂ O ₃ ) was 65% by weight, the volume resistivity was 5 × 10 ⁸ Ω · cm, and the conductivity was obtained. However, the addition amount was 60% by weight. % Or more, the bending strength could not satisfy 3 kg / mm ² and the bending strength required as a structural component material of 10 kg / mm ² or more.

Sample No. Chromium oxide (Cr
_Since the content of ₂ O ₃ ) is 5% by weight, the bending strength is 1%.
Although it had a strength of 3 kg / mm ² and usable as a structural component material, the effect of adding chromium oxide (Cr ₂ O ₃ ) was thin because the addition amount was less than 10% by weight. The volume specific resistance could not be less than 10 ¹¹ Ω · cm.

On the other hand, the sample No. In Examples 2 to 6, since the content of chromium oxide (Cr ₂ O ₃ ) is in the range of 10 to 60% by weight, the volume resistivity can be less than 10 ¹¹ Ω · cm, and the bending strength can be reduced. 10 kg / mm ² or more could be satisfied.

Then, the sample No. The conductive ceramic of No. 5 was subjected to X-ray diffraction and crystal analysis was performed. FIG. 1 shows the chart.

As a result, in the conductive ceramic, not only Mg ₂ SiO ₄ but also MgSi
The presence of O ₃ could be confirmed. In addition, the presence of Cr ₂ O ₃ and MgCr ₂ O ₄ serving as conductivity imparting agents could be confirmed.

Example 2 Next, forsterite (Mg ₂ SiO ₄ ) was prepared as a composite oxide as a starting material, and titanium oxide (TiO) was prepared as a conductivity-imparting agent, and added as shown in Table 3. A conductive ceramic was produced in the same manner as in Example 1 except that the amount was changed.

Then, the obtained ceramics were treated with a diameter of 60.
After grinding to a size of 2 mm × 2 mm in thickness to measure the volume resistivity, the flexural strength was measured by a three-point bending test, and the volume resistivity was less than 10 ¹¹ Ω · cm and the flexural strength was 10 kg / Those having mm ² or more were regarded as excellent.

The results are as shown in Table 4.

[0032]

[Table 3]

[0033]

[Table 4]

As a result, the sample No. In No. 14, since the titanium oxide (TiO) content was 65% by weight, the volume resistivity was 9 × 10 ⁹ Ω · cm, and the conductivity was obtained. To be
The flexural strength of 7 kg / mm ² and the flexural strength of 10 kg / mm ² or more required as a structural component material could not be satisfied.

The sample No. 8 shows titanium oxide (Ti
O) content is 5% by weight, flexural strength is 13k
g / mm ^{2, which} is a strength that can be used as a structural component material, but since the amount added is less than 10% by weight, the effect of adding titanium oxide (TiO) is thin and the volume resistivity is low. The value could not be less than 10 ¹¹ Ω · cm.

On the other hand, the sample No. In Nos. 9 to 13, the content of titanium oxide (TiO) is in the range of 10 to 60% by weight, so that the volume resistivity can be less than 10 ¹¹ Ω · cm and the bending strength is 10 kg / mm. ² or more could be satisfied. Then, the sample No. Twelve conductive ceramics were subjected to X-ray diffraction for crystal analysis. FIG. 2 shows the chart.

As a result, in the conductive ceramics, not only Mg ₂ SiO ₄ but also MgSi
The presence of O ₃ could be confirmed. In addition, the presence of TiO and MgTi ₂ O ₅ as conductivity imparting agents could be confirmed.

Example 3 Further, forsterite (Mg ₂ SiO ₄ ) was used as a composite oxide as a starting material,
Chromium oxide (Cr ₂ O ₃ ) and titanium oxide (TiO) were each prepared as a conductivity-imparting agent, and the amount of addition was changed as shown in Table 5 to produce a conductive ceramic in the same manner as in Example 1.

Then, the obtained ceramics were made to have a diameter of 60.
After grinding to a size of 2 mm × 2 mm in thickness and measuring the volume resistivity, the flexural strength is measured by a three-point bending test, and the volume resistivity is 10 ¹⁰ Ω · cm or more and the flexural strength is 10 kg / Those having mm ² or more were regarded as excellent.

The results are as shown in Table 6.

[0041]

[Table 5]

[0042]

[Table 6]

As a result, even when chromium oxide (Cr ₂ O ₃ ) and titanium oxide (TiO) are added as the conductivity-imparting agent, if the added amount is 10 to 60% by weight, the volume resistivity value is 10 ¹¹ Ω. · Less than cm and bending strength of 10 kg / mm
It was found that ^two or more conductive ceramics could be obtained.

As described above, the mechanical properties of the ceramics were maintained by adding chromium oxide (Cr ₂ O ₃ ) and / or titanium oxide (TiO) in the range of 10 to 60% by weight as in Examples 1 to ₃ . It turns out that conductivity can be provided in the state.

In each embodiment, chromium oxide (Cr ₂ O) was used.
₃ ), an example in which titanium oxide (TiO) is added alone and an example in which both are added are shown. In addition, iron oxide (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ) is used as a conductivity-imparting agent.
With the above chromium oxide (Cr ₂ O ₃ ) or titanium oxide (Ti
O), the volume resistivity is less than 10 ¹¹ Ω · cm and the bending strength is 10 kg / mm
² or more.

[0046]

As described above, according to the present invention, MgO
Chromium oxide and / or SiO ₂
Or titanium oxide, whose volume resistivity is 1
By using conductive ceramics having a resistance of less than 0 ¹¹ Ω · cm and a bending strength of 10 kg / mm ² or more, conductivity can be obtained while maintaining the strength as a structural component material. A probe for evaluating the resistance of a semiconductor / thin film process, a guide member such as a tape guide in a magnetic recording apparatus, a spacer for holding a magnetic disk substrate at a predetermined interval, a support member for a magnetic disk substrate such as a shim and a clamp, a guide roller for a VTR,
Alternatively, it can be suitably used as a structural component material such as an electrodeposition coating nozzle. In addition, since the firing can be performed in the air atmosphere, the manufacturing process can be simplified, the productivity can be increased, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a view showing a chart of an X-ray diffraction of a conductive ceramic according to the present invention.

FIG. 2 is a chart showing a chart of another conductive ceramic according to the present invention by X-ray diffraction.

Claims (1)

(57) [Claims] 1. A composite oxide comprising MgO and SiO ₂ as a main component, comprising chromium oxide and / or titanium oxide, having a volume resistivity of less than 10 ¹¹ Ω · cm and a bending strength of 10 kg / mm ^2. Conductive ceramics characterized by the above.