JPH1029880A - High purity refractory and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high purity refractory capable of displaying a desired electrical characteristic without being damaged when used as a tool material for mounting at the time of burning an electronic component by reducing impurity such as SiO2 in an oxide based refractory such as Al2 O3 and ZrO2 . SOLUTION: In the high purity refractory, a refractory compact or sintered body containing mainly SiO2 , Fe2 O3 and alkali or alkaline earth metal oxide as impurities is subjected to a heat treatment under a reducing atmosphere to highly purify at least a surface substantially. The heat treatment is executed preferably at 1,200-1,600 deg.C. Further, at least hydrogen is preferably incorporated as the reductive atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-purity refractory and a method for producing the same, and more particularly, to a high-purity refractory molded or sintered body which is subjected to a heat treatment in a reducing atmosphere to remove impurities and to purify the product. The present invention relates to a high-purity refractory and a method for producing the same.

[0002]

2. Description of the Related Art Ceramic electronic components such as ferrites and capacitors exhibit necessary electrical characteristics by being heated and fired at about 1200 to 1500 ° C., or 1650 ° C. or higher depending on the product. The firing of these ceramic electronic components is generally carried out by placing them on a firing tool of a refractory sintered body such as alumina or zirconia. Silica (SiO ₂ ),
Sodium oxide (Na ₂ O) and potassium oxide (K ₂ O)
If impurities such as an alkali metal oxide such as an alkali earth metal oxide such as calcia (CaO) and iron oxide (Fe ₂ O ₃ ) are contained, the electronic component mounted on the tool material and the above There is a possibility that impurities and react during firing. When the impurities react with the electronic component, the quality of the electronic component is reduced and the production yield is reduced because the fired electronic component does not have desired electrical characteristics. In particular, in recent years, electronic components have been required to have higher performance with the expansion of various uses. Therefore, the quality reduction by the firing tool material as described above is not preferable, and the refractory sintered body of the firing tool material is required to be highly purified.

[0003] As described above, it is necessary to minimize impurities in the firing tool material for electronic components. As a method of removing impurities contained in the refractory, for example,
This method uses a high-purity raw material, such as obtaining a highly purified commercial raw material powder, or treating the raw material powder with an acid to obtain Fe ₂
A method for removing O ₃ impurities has been proposed.
Japanese Patent Application Laid-Open No. 2-27005 proposes a method of treating silicon carbide powder with hydrogen fluoride gas to remove silica contained therein. Further, it is a method of forming a refractory molded body of a predetermined shape from the raw material powder, heat-treating the refractory molded body to scatter and remove impurities, for example, after forming a refractory molded body of a predetermined shape from the raw material powder, A method of repeatedly heat-treating a refractory molded body in the atmosphere at a high temperature of 1750 ° C. or higher to volatilize and remove impurities such as silica, alkali metal oxides, alkaline earth metal oxides, and iron oxides described above to achieve high purity. Proposed.

[0004]

However, in the method using the above-mentioned highly purified raw material powder, the commercially available high-purity raw material powder is extremely expensive and poor in industrial practicality. When the device is used and used by itself, a predetermined processing device for the process is required, and the operation may be complicated, which is not practical. In addition, highly purified raw material powder is not preferable because it has a small amount of impurities that can serve as an auxiliary agent, so that sintering at low and medium temperatures is difficult and the strength of the obtained refractory tends to be low. Further, the refractory molded body is placed in the atmosphere 17
The method of reducing impurities by heat treatment at a high temperature of 50 ° C. or more is more practical than the method using high-purity raw material powder, but the sintering of refractory proceeds during heat treatment, resulting in abnormal deformation and spalling resistance. May be reduced. In addition, impurities are removed only on the surface of the refractory, and it is difficult to purify the inside of the refractory so that it can be used plural times.

According to the present invention, a refractory requiring high purity, which is used for a firing tool or the like which has a great effect on the characteristics of a fired object such as a ceramic electronic component as described above, is produced at a lower temperature than before. It is an object of the present invention to simply and efficiently provide a highly purified product. For this purpose, the present inventors, in particular, a refractory molded body of a predetermined shape manufactured using the impurity-containing refractory raw material powder or a sintered body containing an impurity, at a relatively low temperature in a reducing atmosphere. By heat treatment, without affecting the refractory itself mainly composed of zirconia or alumina, only the impurities such as SiO ₂ , the object to be fired, especially the ceramic electronic component is placed on the surface thereof and fired. However, it has been found that the desired electrical characteristics can be sufficiently expressed without deteriorating the electrical characteristics, and the electrical characteristics can be removed to such an extent that it has the durability that can be used repeatedly.

[0006]

According to the present invention, mainly S
A refractory molded body or sintered body containing iO ₂ , Fe ₂ O ₃ , alkali or alkaline earth metal oxide as impurities is subjected to heat treatment in a reducing atmosphere to at least substantially purify the surface. A high-purity refractory characterized by comprising: In the high-purity refractory of the present invention,
The heat treatment is preferably performed while maintaining the temperature at 1200 to 1600 ° C., and it is preferable that at least hydrogen is contained as a reducing atmosphere. Further, the compact or sintered body can be highly purified to be made of partially stabilized zirconia having a content of 99.5% by weight or more of ZrO ₂ and Y ₂ O ₃ . Alternatively, the compact or sintered body is highly purified and the content of the Al ₂ O ₃ component is 9
It can be at least 9.5% by weight.

According to the present invention, SiO ₂ , F
e ₂ O ₃ , an alkali or alkaline earth metal oxide as an impurity,
Temperature 12 under a reducing atmosphere containing at least hydrogen
A method for producing a high-purity refractory is provided, wherein the method comprises a heat treatment at 00 to 1600 ° C. to substantially purify at least the surface of the refractory molded body or sintered body.

According to the present invention, a compact formed from a refractory raw material powder containing impurities of an oxide such as silica or a sintered body containing impurities is relatively reduced under a reducing atmosphere. Since the heat treatment is performed at a low temperature of 1200 to 1600 ° C., impurities such as silica can be gasified and removed, and oxides which are main components of refractories such as zirconia and alumina are not scattered. Therefore,
The refractory obtained is a good and highly purified high-purity refractory which is not deformed during the heat treatment and has no decrease in spalling resistance. Even if it is repeatedly used as a firing tool material, the characteristics can be satisfactorily exhibited without impairing the electric characteristics. In the present invention, the compact containing the predetermined impurity is formed by using the impurity-containing raw material powder. It means that the inside heat treatment is performed. The molded body is sufficiently sintered and densified at the time of firing, and becomes a highly durable high-purity refractory that can be repeatedly used as a firing tool for electronic components by a subsequent heat treatment.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the refractory molded body or sintered body subjected to the high-purification treatment is made of SiO ₂ , alkali metal, alkaline earth metal, Fe ₂ O ₃ which has been conventionally used as a raw material for forming a predetermined refractory. Or a sintered body containing an oxide impurity such as SiO ₂ which remains after sintering such a molded body as it is. In the present invention, the molded body to be subjected to the high-purification treatment is fired and sintered in advance before the high-purification treatment. Molding and baking can be performed by a conventionally known general method. Since impurities contained in the raw material powder act as a sintering aid during firing, sintering is easy and a high-strength refractory sintered body can be obtained, which is preferable. That is, the high-purity refractory of the present invention is preferably, by positively using those containing the above impurities in the raw material powder,
Finally, the impurity content is reduced. The main components constituting the high-purity refractory of the present invention include oxides such as partially stabilized or stabilized zirconia (ZrO ₂ ) and alumina (Al ₂ O ₃ ), and non-oxides such as silicon carbide. . In particular, the content of the main components of yttria (Y ₂ O ₃ ) and ZrO ₂ , which are conventionally used as electronic component firing tools, is less than about 99.5% by weight, and SiO ₂ , F ₂
impurities such as e ₂ O ₃ , CaO, K ₂ O, and Na ₂ O.
Stabilized zirconia containing 5% by weight or more, or alumina containing mainly SiO ₂ or iron oxide as an impurity in an amount of about 0.5% by weight or more and Al ₂ O ₃ of less than 99.5% by weight as a main component Is preferred.

The heat treatment of the present invention is carried out under a reducing atmosphere.
It can be performed by holding at 00 to 1600 ° C. for a predetermined time. As the reducing atmosphere, a mixed gas of hydrogen gas and nitrogen gas is usually used. Nitrogen gas is inexpensive compared to hydrogen gas, and industrially, it is preferable that the nitrogen gas mixture ratio is large. Usually, a mixed gas of hydrogen and nitrogen having a hydrogen concentration of 25 to 75% by volume is used. If the hydrogen gas content is less than 25% by volume, the reducing effect is small, which is not preferable. Further, an argon gas may be used instead of the nitrogen gas. Further, as the reducing atmosphere, a gas that generates hydrogen gas under predetermined firing conditions such as ammonia (NH ₃ ) gas without mixing hydrogen gas from the beginning can be used. NH ₃ is N ₂ and H ₂ at 1000 ° C. or higher.
Decompose into Further, a gas such as hydrocarbon or carbon monoxide which is easily oxidized may be used. Further, a reducing gas such as H ₂ gas, NH ₃ gas, hydrocarbon, chlorine (Cl ₂ ) gas or the like may be used in combination, such as mixing NH ₃ gas and hydrocarbon simultaneously, or N ₂ gas. , Ar gas may be used in combination. In the present invention, it is necessary to select a time when the refractory molded body and the sintered body to be subjected to the high-purity heat treatment are brought into the above-mentioned reducing atmosphere in the heat treatment. In the case of a refractory molded body, since it is preliminarily baked as described above and then subjected to high purification treatment, the same debinding step and sintering as in the conventional refractory manufacturing method are performed in the same furnace where high purification heat treatment is performed. After the step, the atmosphere in the furnace is treated as a reducing atmosphere at a predetermined heat treatment temperature. This is because, if the furnace atmosphere is heated under a reducing atmosphere from the beginning, impurities serving as sintering agents volatilize, and a high-purity refractory having a predetermined density cannot be obtained. On the other hand, in the refractory sintered body, the atmosphere in the heat treatment furnace can be treated as the above-described reducing atmosphere from the beginning.

The high-purity heat treatment of the present invention is carried out in the reducing atmosphere at a temperature of about 1100 ° C. or more and less than 1750 ° C., preferably about 1200 to 1600 ° C. If the heating temperature is lower than 1100 ° C., impurities cannot be sufficiently removed. On the other hand, if the temperature is 1750 ° C. or higher, as described above, the sintering of the fired refractory molded body or the sintered body proceeds excessively, and is deformed or the spalling resistance is unfavorably reduced. The heat treatment of the present invention can be performed by holding at the above-mentioned heating temperature in the above-mentioned reducing atmosphere for about 3 to 10 hours. The holding time can be appropriately selected from the above range according to the processing temperature and the strength of the reducing property in the atmosphere gas. As described above, by performing a predetermined heat treatment under the reducing atmosphere of the present invention, impurities present in the object to be heated, for example,
SiO ₂ is SiO ₂ + H ₂ → SiO (gas) + H ₂ O
The gas is scattered and removed as a gas by the reaction of the above.
_{2 The} content can be reduced from 0.2% to 0.04% by weight.

In addition, since the high-purity refractory of the present invention is used as a tool for firing ceramic electronic parts,
If there is no inconvenience in the object to be fired at a firing temperature of 1200 to 1500 ° C. for the ceramic electronic component, impurities may remain inside. Therefore, in the heat treatment of the present invention, even if the object to be fired such as a ceramic electronic component is placed on the obtained high-purity refractory and treated at a predetermined firing temperature, the properties of the object to be fired are not adversely affected. In addition, at least impurities on the surface should be removed to such an extent that they can be used repeatedly, so that they have substantially high purity. Usually about 2 mm from the surface
It is only necessary that the above-described impurities have been removed at a depth of up to. In addition, if Y ₂ O ₃ stabilized zirconia or alumina is used as a firing tool material for the ceramic electronic component,
What is necessary is just to remove impurities to less than 0.5% by weight.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. However, the present invention is not limited by the following examples. Example 1 Commercially available A having a purity of 99.2% by weight was used as a refractory raw material powder.
Using l ₂ O ₃ powder (containing mainly 0.25% by weight of SiO ₂ and 0.15% by weight of Fe ₂ O ₃ as impurities), a thickness of 310 × 310 (mm) with a thickness of 8 mm was obtained by a uniaxial molding method. A flat plate was produced. Then, under air atmosphere, 168
The resultant was heated at 0 ° C. for 3 hours and fired to obtain an Al ₂ O ₃ refractory sintered body. A sample was cut out from the obtained sintered body, and the content of impurities such as SiO ₂ was measured by wet analysis. As a result, the content of SiO ₂ was 0.25% by weight. Also,
Each of the produced sintered bodies was subjected to hydrogen (H
Heat treatment was performed at 1500 ° C. for 5 hours in a reducing gas atmosphere having a mixture ratio of ₂ ) and nitrogen (N ₂ ). A sample was similarly cut out from the heat-treated sintered body, and the SiO ₂ content was measured in the same manner. Experiment No. About 3 and refractories of 4 of the present invention, SiO ₂ amount and the amount of impurities other than SiO ₂ were measured respectively as an impurity. The results are shown in Table 1.

As is evident from the above-mentioned Example 1, the Al powder formed from the alumina raw material powder containing the predetermined impurities was formed.
And calcined for ₂ O ₃ formed body by sintering, that a high-purity alumina refractory sintered body which impurities are reduced by the resulting sintered body to heat treatment under a reducing gas atmosphere to obtain I understand. In addition, H ₂ gas and N
_As the H ₂ gas ratio of the mixed gas of the _two gases increases, S
The content of impurities such as iO ₂ is reduced. However, if the H ₂ gas exceeds 75% by volume in Experiment Nos. 5 and 6, the cost increases and it becomes impractical. When the H ₂ gas content is 25 to 75% by volume, there is no problem in terms of cost and the content of impurities such as SiO ₂ is reduced, which is preferable.

[0015]

[Table 1]

[0016] Each sintered body of Example 1 Similarly Al ₂ O ₃ produced by main component, H ₂ gas 25 volume% H ₂ -N ₂ in a mixed gas atmosphere, the table heating temperature Heat treatment was carried out for 5 hours while changing as shown in FIG. The content of impurities such as SiO ₂ in the heat-treated sintered body was measured in the same manner as in Example 1. The refractory of the present invention (Experiment Nos. 10 to 12) was made of Si.
The amounts of O ₂ and impurities other than SiO ₂ were measured.
Table 2 shows the results. Note that the experiment No. 14 was performed in an air atmosphere.

As is clear from the above-mentioned Example 2, the experiment N
o. 1200 to 1600 under a reducing gas atmosphere of 10 to 12
It can be understood that the content of impurities such as SiO ₂ is sufficiently reduced by performing the heat treatment at ° C. S below 1100 ° C
It can be seen that the reduction of iO ₂ is not sufficient, and deformation and spalling resistance at 1750 ° C. are unfavorable. Experiment No. No. 14 is the same as the conventional method of dispersing impurities due to high temperature, and it can be seen that the content of SiO ₂ is not sufficiently reduced and disadvantages such as deformation occur.

[0018]

[Table 2]

Example 3 Each sintered body of the main component of Al ₂ O ₃ produced in the same manner as in Example 1 was mixed as shown in Table 3 with the heat treatment atmosphere being a mixed gas of NH ₃ and N _2. Change the ratio to 150
Heat treatment was performed at 0 ° C. for 5 hours. Heat-treated sintered body Si
The content of impurities such as O ₂ was measured in the same manner as in Example 1. Experiment No. For 19, 21 and refractory of the present invention 23 were measured amount of SiO ₂ and SiO ₂ than impurity amounts, respectively. Table 3 shows the results.

[0020]

[Table 3]

As apparent from Example 3, the heating temperature was 1
It can be seen that when the mixed gas of NH ₃ and N _{2 is at} a temperature of 500 ° C. and the NH ₃ is 32% by volume or more, the content of impurities such as SiO ₂ is sufficiently reduced and the reduction effect can be obtained. In this case, 1
At 500 ° C., for example, a mixed gas having an NH ₃ concentration of 32% by volume is obtained by decomposing ammonia to a H ₂ concentration of about 24% by volume
It is estimated that the mixed gas will have a N ₂ concentration of about 76% by volume. The N ₂ gas alone has no effect, and when the concentration of NH ₃ is high, the concentration of H ₂ gas in the decomposition gas atmosphere increases and the reducibility increases. For example, NH ₃ concentration 1
If 00% decomposition gas H ₂ is 75 volume% N ₂ 2
5% by volume. Furthermore, if you want to increase the ratio of H ₂ ,
Although the cost increases, H ₂ gas may be added and mixed. As is clear from Examples 1 and 3, there is no particular difference in the effect between the case where the mixed gas of the H ₂ gas and the N ₂ gas is used and the case where the mixed gas is converted into the decomposed gas using NH _3. . N
When the H ₃ concentration is 30% or less by volume, there is no effect.

[0022]

[Table 4]

Example 4 As a refractory raw material powder, a commercially available Y ₂ O ₃ containing 8% by weight of Zr was used.
Uniaxial metal was manufactured in the same manner as in Example 1 except that 91.0% by weight of O ₂ and partially stabilized ZrO ₂ powder (containing 1.0% by weight of impurities and 0.35% by weight of SiO ₂ thereof) were used. A flat molded body having a thickness of 3 mm and a size of 110 × 110 (mm) was produced by a molding method. Then, under air atmosphere, 165
The mixture was heated at 0 ° C. for 3 hours and fired to obtain a ZrO ₂ refractory sintered body. A sample was cut out from the obtained sintered body, and the SiO ₂ content of impurities such as SiO ₂ measured in the same manner as in Example 1 was 0.35% by weight. Each of the produced sintered bodies was subjected to a heat treatment at 1500 ° C. for 5 hours in a reducing gas atmosphere having a mixture ratio of H ₂ and N ₂ shown in Table 4. A sample was similarly cut out from the heat-treated sintered body, and the content of impurities such as SiO ₂ was measured in the same manner. Experiment No. 26 and 2
Measured amount of SiO ₂ and SiO ₂ than impurity amounts respectively for 7 refractory of the present invention. Table 4 shows the results.
It was shown to.

As is apparent from Example 4, the partially stabilized zirconia compact formed from the raw material powder having predetermined impurities is sintered and sintered to obtain a zirconia sintered body. It can be seen that, similarly to the Al ₂ O ₃ sintered body of Example 1, the heat treatment in a reducing gas atmosphere reduced impurities and provided a high-purity zirconia refractory. Similarly, as the H ₂ gas ratio increases, the Si
It can also be seen that the content of impurities such as O ₂ is reduced.

Example 5 Each sintered body of ZrO ₂ produced in the same manner as in Example 4
In the same manner as in Example 2, heat treatment was performed for 5 hours in an H ₂ -N ₂ mixed gas atmosphere of 25% by volume of H ₂ gas while changing the heating temperature as shown in Table 5. The content of impurities such as SiO ₂ in the heat-treated ZrO ₂ sintered body was measured in the same manner as in Example 1. Experiment No. The refractory of the present invention 33 to 35 were measured amount of SiO ₂ and SiO ₂ than impurity amounts, respectively. Table 5 shows the results. Note that the experiment No. 37 was performed in an air atmosphere. As is clear from Example 5, in the partially stabilized zirconia sintered body, as in Example 2, 1200-200
It can be seen that by performing the heat treatment at 1600 ° C., impurities are better reduced than in the zirconia sintered body.

[0026]

[Table 5]

Example 6 The high-purity refractory of the present invention obtained by heat treatment in Examples 1 to 5 (Experiments No. 3, 10, 12, 19, 23,
26, 27, 33, and 35) and refractories that were not sufficiently purified (Experiment Nos. 7, 9, 30, and 32)
Each was used as a firing tool for Mn-Zn soft ferrite having a magnetic permeability of 10,000 classes. Firing temperature is 135
It was 0 ° C. It was inspected whether or not the soft ferrite characteristics were normally developed by firing. Table 6 shows the number of uses until the soft ferrite characteristics were not developed. As is clear from the results shown in Table 6, when the high-purity refractory of the present invention is used, the soft ferrite characteristics can be exhibited by repeatedly using at least 5 times or more and at most 26 times. On the other hand, when a refractory which is not sufficiently purified is used, it can be seen that soft ferrite characteristics are not exhibited at all or cannot be used several times.

[0028]

[Table 6]

[0029]

According to the present invention, a compact formed using a raw material powder containing impurities or a sintered body containing impurities is heat-treated in a reducing gas atmosphere at low cost.
In addition, a high-purity refractory can be easily obtained. Since the high-purity refractory of the present invention is sufficiently purified by removing impurities, it is suitable as a tool material for firing electronic components sensitive to impurities such as soft ferrite or a product in which impurities cause inconvenience. Can be used for In addition, the compact obtained from the raw material powder containing impurities becomes a sufficiently dense sintered body with excellent sinterability at the time of firing performed before the heat treatment in a reducing gas atmosphere, and at the same time, the impurity is reduced by the subsequent heat treatment. Is removed to obtain a high-purity refractory.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Suzuki 1 Minami Fuji, Ogakie-cho, Kariya-shi, Aichi Prefecture Toshiba Ceramics Co., Ltd. Kariya Works

Claims (6)

[Claims] 1. A refractory molded body or sintered body mainly containing SiO ₂ , Fe ₂ O ₃ , alkali or alkaline earth metal oxide as an impurity is subjected to heat treatment in a reducing atmosphere, and at least the surface thereof is heated. A high-purity refractory characterized by being substantially highly purified. 2. The method according to claim 1, wherein the heat treatment is performed at a temperature of 1200 to 1600.
The high-purity refractory according to claim 1, which is maintained at a temperature of ℃. 3. The high-purity refractory according to claim 1, wherein the reducing atmosphere contains at least hydrogen. 4. The molded body or sintered body is highly purified, and the content of a component composed of ZrO ₂ and Y ₂ O ₃ is 99.5.
3. A partially stabilized zirconia of not less than% by weight.
Or a high-purity refractory according to 3. 5. The high-purity refractory according to claim 1, 2 or 3, wherein the compact or sintered body is highly purified so that the content of Al ₂ O ₃ component becomes 99.5% by weight or more. 6. A refractory molded body or sintered body mainly containing SiO ₂ , Fe ₂ O ₃ , alkali or alkaline earth metal oxide as an impurity in a reducing atmosphere containing at least hydrogen. A method of producing a high-purity refractory by heat-treating at a temperature of 1200 to 1600 ° C. to substantially purify at least the surface of the refractory molded body or sintered body.