JP2007254191A - Translucent magnesium oxide sintered compact and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a magnesium oxide sintered compact exhibiting good translucency over an infrared range from visible ray. <P>SOLUTION: Magnesium oxide powder having ≥99.9% purity and 3-15 m<SP>2</SP>/g specific surface area is formed into a formed body in which the density is ≥58% theoretical density, the content of Sc is ≥30 wt.ppm and ≤2,000 wt.ppm and the content of Al is ≥5 wt.ppm and ≤100 wt.ppm. The formed body is heat-treated and is subjected to primary firing at ≥1,250°C and ≤1,600°C under the atmosphere to have ≥94% theoretical density. The translucent magnesium oxide sintered compact is obtained by applying hot isostatic pressure treatment to the primarily fired body at ≥1,200°C and ≤1,600°C under 40-196 MPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a translucent magnesium oxide sintered body represented by the general formula MgO and a method for producing the same. The sintered body of the present invention is suitably used as an optical component such as a high-temperature material, an infrared window material, a translucent substrate, or a light emitting tube.

  Magnesium oxide represented by MgO (hereinafter referred to as magnesia) has a cubic crystal structure and no birefringence. Therefore, it is possible to obtain a sintered body having excellent translucency by removing pores and segregation of impurities. Magnesia has a very high melting point of 2800 ° C. (Chemical Handbook, edited by the Chemical Society of Japan) and is known to be an excellent material having heat resistance, alkali resistance and high thermal conductivity. However, since magnesia has an extremely high melting point, it is difficult to synthesize large crystals that are optically superior with existing single crystal synthesis techniques.

  On the other hand, ceramics (polycrystals) can be synthesized at a relatively low temperature below the melting point, so high temperature melting point yttrium oxide (yttria) and other rare earth oxides as well as magnesia have been used. Studies have been actively conducted to apply to envelopes for discharge lamps, corrosion-resistant members, and the like.

Examples of reports on polycrystalline translucent magnesia sintered bodies include:
(1) A method of hot pressing by adding a fluoride such as LiF or NaF (for example, Non-Patent Document 1: GDMiles et al, Trans. Brit. Ceram. Soc. 66 319 (1967)),
(2) A method of improving the sinterability by dispersing MgO powder in an organic solvent and re-calcining (for example, Patent Document 1: Japanese Patent Laid-Open No. 51-80313). As a method of adding a sintering aid,
(3) A method of adding a solution-like aluminum compound (Patent Document 2: JP-A-59-50068),
(4) A method of adding SiO ₂ and a small amount of B ₂ O ₃ (Patent Document 3: JP-A 2000-281428),
(5) A method of adding 0.01 to 0.5 wt% of scandium oxide, ytterbium oxide, or germanium oxide and baking in an inert atmosphere (Patent Document 4: Japanese Patent Laid-Open No. 48-2883) is disclosed.

In the method (1), a sintered body having a relatively high translucency can be obtained, but it is difficult to produce a sintered body having a large or complicated shape, and an annealing process after hot pressing is required. And mass productivity is poor. In addition, LiF and NaF are low melting point compounds that evaporate during the firing process, resulting in a difference in the grain growth rate between the outer periphery and the inside of the sample. Have difficulty.
With the method (2), it is very difficult to obtain a sufficiently light-transmitting sintered body, and the role of the organic solvent that promotes the densification of MgO is unclear. Depending on the history of powder production, The effect of adding an organic solvent may not appear.

In the method of (3), details are unknown because there is no description about the transmittance, but in order to produce a sintered body with high translucency with Al ₂ O ₃ alone, it is very sinterable. It is necessary to use excellent raw material powder.
In the method (4), even if the amount of B ₂ O ₃ is very small, the mechanical strength of magnesia at a high temperature is lowered and the firing furnace is severely contaminated by a boron compound which is a low melting point material.
In the method of (5), despite the firing at a relatively high temperature of 1700 ° C or higher, the translucency is about 80% in total transmittance, which is far from the theoretical transmittance (≈88%). There is a disadvantage that it does not reach. In addition, in the method of adding these sintering aids, the specific surface area is not described and the details are unknown, but very fine magnesia powder is used. As the particle size of the powder decreases, the sintering activity increases, but the frictional force between the particles increases and it becomes difficult to produce a compact with a uniform structure. Further, there are drawbacks such as large shrinkage and easy cracking.
GDMiles et al, Trans.Brit.Ceram.Soc. 66 319 (1967) JP 51-80313 JP 59-50068 JP2000-281428 JP 48-2883

  An object of the present invention is to provide a magnesium oxide sintered body that is transparent from the visible region to the infrared region and a method for producing the same by a technique that can be industrially put into practical use.

In translucent magnesium oxide sintered body of the present invention, Sc content than 30wtppm 2000wtppm or less, Al content is more than 5 wtppm 100 wtppm or less, Sc ₂ O ₃ and Al ₂ O ₃ and purity excluding 99.9% or more, The average particle diameter of the sintered body is 1 μm or more and 20 μm or less, and the linear transmittance over a wavelength region of 500 nm to 6.5 μm is 85% or more at 1 mm thickness.

The method for producing a light-transmitting magnesium oxide sintered body according to the present invention comprises a magnesium oxide powder and a binder having a purity of 99.9% or more excluding Sc ₂ O ₃ and Al ₂ O ₃ and having a specific surface area of 3 to 15 m ² / g. Using a molded body with a molding density of 58% or more of theoretical density ratio, Sc content of 30wtppm or more and 2000wtppm or less, Al content of 5wtppm or more and 100wtppm or less, and heat-treating this to remove the binder, reducing atmosphere In the middle, in vacuum or in the atmosphere, the primary firing is carried out at 1250 ° C or higher and 1600 ° C or lower and the theoretical density ratio is 94% or higher, and then at a temperature of 1200 ° C or higher and 1600 ° C or lower and a pressure of 49MPa to 196MPa. By applying hot isostatic pressing (HIP), the Sc content is 30 wtppm or more and 2000 wtppm or less, the Al content is 5 wtppm or more and 100 wtppm or less, the average particle size of the sintered body is 1 μm or more and 20 μm or less, and the wavelength is 500 nm To make a sintered body with a linear transmittance over the 6.5μm area of 1mm thickness and 85% or more. And butterflies.

As a result of various studies to solve the above problems, the present inventors have found that a magnesium oxide sintered body having a linear transmittance of 1 mm thickness and a thickness of 85% or more over a wavelength range of 500 nm to 6.5 μm can be produced. I found it. For this purpose, magnesium oxide powder or high-purity magnesium oxide powder having a purity of 99.9% or more and a specific surface area of 3 to 15 m ² / g excluding Sc ₂ O ₃ and Al ₂ O ₃ is used. Using this powder and binder, a high-density molded body having a theoretical density ratio of 58% or more, in which the Sc content is controlled to 30 wtppm to 2000 wtppm and the Al content is controlled to 5 wtppm to 100 wtppm. Next, primary firing is performed at 1250 ° C or higher and 1600 ° C or lower in a reducing atmosphere, vacuum or air so that the theoretical density of the sintered body becomes 94% or higher, and then at a temperature of 1200 ° C or higher and 1600 ° C or lower. By performing HIP treatment at a pressure of 49 MPa to 196 MPa, pores of sub-micron or less can be discharged, and a sintered body having good transmittance from the visible to the infrared region can be obtained.
If the manufacturing process is managed, the Sc content and Al content can be kept unchanged from the stage of the compact to the sintered body, and the content of other impurities does not increase in the process from the compact to the sintered body. You can

  In the sintering of magnesia according to the present invention, Sc of 30 wtppm or more and 2000 wtppm or less and Al of 5 wtppm or more and 100 wtppm or less exhibit a great effect as a sintering aid. The details of the densification mechanism in sintering are unclear, but it only works as a densification promoter when primary firing is performed in the range of 1250 ° C to 1600 ° C, and at higher temperatures it promotes abnormal grain growth. And produces a heterogeneous phase.

  Although depending on the sinterability etc. of the raw materials used, if the primary firing temperature is less than 1250 ° C, the density of grain growth does not proceed sufficiently regardless of the presence and content of Sc and Al. The density is less than 94%. In such a state, there are large voids that cannot be eliminated even when the HIP treatment is performed, so that only an opaque or translucent sintered body can be obtained.

  When a sample with an Sc content of less than 30 wtppm is primarily fired in the range of 1250 ° C to 1600 ° C, the sintered density is 94% or more, but even with HIP treatment, sufficient densification cannot be achieved. The resulting sintered body is a translucent body or an opaque body. On the other hand, when the Sc content exceeds 2000 wtppm, the grain growth is remarkably faster than when the Sc content is less than that, and the crystal grains become large before the pores are exhausted sufficiently even in the primary firing or HIP treatment. It becomes a sintered body with a large average particle size contained in the. As a result, the obtained sintered body is a translucent body or an opaque body as in the case where the Sc content is less than 30 wtppm.

  In the present invention, both Sc and a very small amount of Al are added. That is, even if the Sc content is in the range of 30 wtppm or more and 2000 wtppm or less, if the Al content is 5 wtppm or less, a sufficient densification promoting effect can not be obtained even if HIP treatment is performed, and sintering with excellent translucency Getting a body is not easy. On the other hand, when the Al content exceeds 100 wtppm, it acts mainly as a grain growth accelerator, and rapid grain growth occurs with pores contained in the sintered body, and the translucency is significantly reduced.

  Further, when primary firing is performed at a temperature exceeding 1600 ° C., it is difficult to produce a sintered body having sufficient translucency by sintering without sufficiently discharging pores. In this case, the average particle diameter of the sintered body is 20 μm or more. Further, depending on the firing conditions, Sc added as an auxiliary agent segregates at the grain boundary and a heterogeneous phase is generated. Therefore, the primary firing temperature must be 1250 ° C or higher and 1600 ° C or lower.

  The primary firing atmosphere of the molded body may be any of a reducing atmosphere, a vacuum, or air, but is preferably a hydrogen atmosphere or a vacuum. The firing time is represented by the holding time at the maximum temperature, for example, 10 minutes or more and 10 hours or less, preferably 30 minutes or more and 2 hours or less.

  Furthermore, a sintered body having excellent translucency can be obtained by performing a HIP treatment after the primary firing. The pressure medium is not particularly limited, but an industrially available inert gas may be used, and the treatment temperature is preferably 1200 ° C. or higher and 1600 ° C. or lower. When the temperature is lower than 1200 ° C., the pores cannot be completely removed. When the temperature is higher than 1600 ° C., grain growth proceeds and residual pores are generated. The treatment pressure is preferably 49 MPa or more and 196 MPa or less. At 49MPa or less, sufficient effects cannot be obtained, and at 196MPa or more, only the apparatus is unnecessarily large, and the translucency is not improved. The treatment time is sufficient if it is 0.5 hours or longer, for example, 0.5 hours or more and 2 hours or less, and various times may be changed depending on the thickness of the processed product. The processing time for HIP is also determined by the holding time to the maximum temperature.

  In order to produce a sintered body excellent in translucency, it is necessary to produce and sinter a homogeneous and high-density molded body that does not contain large bubbles or voids inside. Inside the molded body having a molding density of less than 58% of the theoretical density ratio, there are many large pores due to insufficient packing. Therefore, even a molded body to which a proper amount of Sc and Al, which are densification accelerators, is added, is not easy to be sufficiently densified by firing at 1600 ° C. or less. On the other hand, a molded body having a molding density of 58% or more has relatively few internal pores and can be sufficiently densified even at a low temperature.

The primary particle size of the raw material powder to be used is not particularly limited, and a material having a specific surface area of 3 to 15 m ² / g within the scope of the claims and suitable for the molding and firing process may be selected. That is, the ultrafine powder has high sintering activity and excellent sinterability, but it is not easy to handle, but it is not easy to increase the molding density because there are many aggregated particles. In the case of coarse particles, packing is easy, but the sintering activity is low, and it is not easy to densify at low temperature. Therefore, sinterability, in view of the packing property and handling property, the specific surface area of the raw materials used is preferably 3~15m ² / g, it is more preferred 5~12m ² / g. Furthermore, it is most preferable to use a material with little aggregation and a uniform particle size distribution.

  Although the optimal example for implementing this invention is shown below, this invention is not limited to this.

Hereinafter, a manufacturing method is demonstrated concretely. For the production of the sintered body, an easily sinterable high purity magnesium oxide raw material powder having a purity of 99.9% or more and a specific surface area of 3 to 15 m ² / g is used. The purity is considered by removing Sc ₂ O ₃ , Al ₂ O ₃ and components from impurities. Examples of impurities contained in the high-purity raw material powder include Ca and Si. When the amount of these impurities is large, not only the densification promoting effect by Sc and Al is inhibited, but also in some cases, it may segregate at the grain boundary to generate a liquid phase, which is not preferable. Further, transition elements such as Fe and Cr are not preferable because they become a coloring source of the sintered body. Therefore, it is necessary to select a highly purified high-purity raw material to be used. However, this is not the case when it is intentionally added like a color filter.

  In general, magnesium oxide powder is obtained by thermally decomposing magnesium salts such as magnesium hydroxide, basic magnesium carbonate, magnesium acetate, magnesium oxalate, magnesium chloride, magnesium nitrate, and magnesium sulfate. Sex is greatly affected. The starting mother salt used in the present invention is most preferably basic magnesium carbonate having good sinterability, but is not particularly limited.

  Next, a molded body having a desired shape is produced. Examples of the ceramic molding method include extrusion molding, injection molding, press molding, and casting. Molding is not limited to any method, and may be performed by a method in which the molding density is 58% or more and impurities are not mixed. At this time, if necessary, the sintering aids Sc and Al are added so as to be uniformly dispersed according to various molding methods. The addition method is not particularly limited. For example, in the case of press molding, an appropriate amount of Sc and Al compound is added to the slurry for granule preparation, and after sufficient mixing by a ball mill or the like, it is dried by a spray dryer or the like, A granule for molding may be used.

  Regarding the addition timing of Sc and Al, for example, there is no problem even if they are added in the raw material synthesis stage or the calcining stage. In order to exhibit the effect sufficiently with a small amount of content, it is most preferable to mix it in the raw material. As for the form of addition, for example, if it is added at the molding stage, an appropriate amount of fine oxide powder may be added and mixed. In order to uniformly disperse the additive, it is preferable to use a material having the same size or less than the primary particle diameter of the raw material powder. In addition, when added to the raw material synthesis stage, it may be appropriately added as a chloride, hydroxide, nitrate or the like. Regarding the purity of the additive, it is preferable to use a high-purity one as in the case of the raw material powder.

  The obtained molded body is subjected to binder removal treatment by thermal decomposition. The treatment temperature, time, and atmosphere at this time vary depending on the type of the molding aid added, etc., but it takes a sufficient amount of time below the temperature at which the sample surface does not become closed pores. This temperature is preferably about 800 ° C. to 1200 ° C., although it depends on the calcining temperature and sintering property of the raw material powder used and the packing of the molded body. The atmosphere is most commonly an oxygen atmosphere, but there is no problem even if it is performed under Ar or reduced pressure if necessary.

  After completion of the binder removal treatment, the sample is primarily fired at a temperature of 1250 ° C. or higher and 1600 ° C. or lower for 0.5 hour or longer in a reducing atmosphere, vacuum, or air. The firing time is 0.5 hours or more in order to uniformly sinter the whole, and is not particularly limited as long as it is longer. Although it depends on the firing atmosphere and the thickness of the sample, firing for about 1 to 10 hours is usually sufficient for a sample thickness of about 1 to 5 mm.

  Further, after this atmosphere firing, HIP treatment is performed at a temperature of 1200 ° C. to 1600 ° C. and a pressure of 49 MPa to 196 MPa. Although this time also depends on the sample thickness, it is generally about 0.1 to 10 hours if the sample thickness is about 1 to 5 mm, but preferably about 0.5 to 2 hours. The HIP time is expressed as the holding time to the maximum temperature.

Examples will be described below, but the present invention is not limited thereto.
Example 1
Drop 5L of 0.4M (mol · dm ^-3 ) high purity magnesium chloride solution into 5L of sodium carbonate solution 0.4M (mol · dm ^-3 ) at a rate of 100ml / min and cure at 35 ° C for 1 day Went. After curing, filtration and washing with ultrapure water were repeated several times, and then placed in a dryer at 150 ° C. and dried for 1 day. The obtained basic magnesium carbonate was put in an alumina crucible and calcined at 1200 ° C. for 15 hours to prepare a high-purity magnesium oxide raw material powder having a specific surface area of 10 m ² / g.

50 g of this raw material powder, Sc ₂ O ₃ fine powder equivalent to 1000 wtppm in terms of Sc (Shin-Etsu Chemical, 99.99%), and 50 wtppm Al ₂ O ₃ fine powder (Daimei Chemical Co., Ltd. TM-DAR) ), 1 g of Kyoeisha Chemical's Floren G-700 as a peptizer, and 0.25 g of Sekisui Chemical's PVB-BL1 as a binder, 20 g of ethanol, and a nylon pot and nylon balls. The mixture was mixed for a time to obtain an alcohol slurry. This slurry was poured into a plaster mold to produce a disk-shaped molded body having a diameter of 20 mm and a thickness of 2 mm. This molded body was heated at 5 ° C./hr in an oxygen stream and degreased at 1000 ° C. for 5 hours. As a result of obtaining the amounts of Sc and Al contained in the molded article by ICP emission spectrometry, Sc was 970 wtppm and Al was 52 wtppm with respect to MgO. The molding density was 60.6%. Next, this compact was raised to 1500 ° C. at 100 ° C./hr in a vacuum furnace, held for 1 hour, and then cooled at 500 ° C./hr. The degree of vacuum during firing was set to 10 ⁻² Pa or less. As a result of obtaining the theoretical density of the primary sintered body by the Archimedes method, it was 97.9%. This primary sintered body was heated to 1300 ° C. at 800 ° C./hr in Ar gas, and held for 1 hour under a pressure of 98 MPa to perform HIP treatment. The obtained sintered body was mirror-polished using a diamond slurry, and the linear transmittance (t = 1.0 mm) was measured with a spectrophotometer. As a result, the linear transmittances at wavelengths of 500 nm and 6.5 μm were 85.4% and 86.7%, respectively. The linear transmittance of the sintered body of Example 1 is shown in FIG. From this figure, since the transmittance is lowest at 500 nm in the wavelength range of 500 nm to 6.5 μm, the linear transmittance at 500 nm was measured in the following examples and comparative examples.

  This sample was thermally etched in the atmosphere at 1300 ° C. for 2 hours, and the microstructure was observed. As a result, the average particle size was 12.9 μm. Here, the average particle size is C, where the length of the line drawn arbitrarily on a high-resolution image such as SEM is C, the number of particles on this line is N, and the magnification is M. Average particle size = 1.56C / (MN) As sought. The sintered density was determined to be 99.96%. The sintered body was dissolved in acid using an autoclave, and then the Sc content and Al content were determined by ICP emission analysis. As a result, Sc was 970 wtppm with respect to MgO, and Al was 52 wtppm.

Examples 2-7 and Comparative Examples 1-6
Various magnesia compacts (molding density of 59% or more) with different addition amounts of Sc and Al were prepared and sintered in the same manner as in Example 1. The additive content, average particle diameter, and 500 nm Table 1 shows the results obtained for the linear transmittance. From this result, it can be seen that when the Sc content is 30 wtppm or less, or 2000 wtppm or more, a sintered body having a transmittance of 85% or more cannot be obtained. Further, even if the Sc content is within the above range, it is understood that the same is true if the Al content is less than 5 wtppm or exceeds 100 wtppm.

table 1
Sc content Al content Average particle size Linear transmittance
/ wtppm / wtppm / μm /%
Example 2 32 8 7.0 85.0
Example 3 98 21 7.6 85.1
Example 4 490 52 10.2 85.4
Example 5 970 12 10.8 85.6
Example 6 970 98 13.1 86.2
Example 7 1950 21 16.0 85.3
Comparative Example 1 0 3 5.3 48.3
Comparative Example 2 16 94 8.1 65.4
Comparative Example 3 490 3 8.4 82.7
Comparative Example 4 970 110 13.5 78.7
Comparative Example 5 2080 52 16.8 77.9
Comparative Example 6 2080 110 18.3 64.5

Examples 8-12 and Comparative Examples 7-9
Put 5g of magnesia raw material powder with a purity of 99.9% or more in an alumina mortar, add Sc ₂ O ₃ fine powder equivalent to 1500 wtppm in terms of Sc and Al ₂ O ₃ fine powder equivalent to 40 wtppm in terms of Al, Mixing and grinding were performed. This powder was put into a φ15 mm mold, subjected to primary molding at a pressure of 10 MPa, and a molded body having a molding density of 58.8% was produced by CIP molding. This molded body was fired at various firing temperatures in a hydrogen atmosphere for 5 hours, and then subjected to HIP treatment under the same conditions as in Example 1. Table 2 shows the primary firing temperature, primary sintered density, average particle diameter and linear transmittance of the sintered body after the HIP treatment. As a result, a sintered body having a primary firing temperature of 1250 ° C. or higher and a sintered density of 94% or higher, an average particle diameter of 1 μm to 20 μm and a transmittance of 85% or higher after HIP treatment is obtained. However, when the primary firing temperature is less than 1250 ° C., the sintered density is 94% or less, and it becomes difficult to remove pores by HIP treatment, and a translucent sintered body cannot be obtained. On the other hand, when the primary firing temperature exceeds 1600 ° C., the sintered density is 94% or more, but it can be seen that grains grow with pores inside the crystal and the transmittance decreases.

Table 2
Primary firing temperature Primary sintered density Average particle size Linear transmittance
/ ℃ /% / μm /%
Example 8 1250 94.6 1.9 85.1
Example 9 1350 96.9 5.6 85.6
Example 10 1450 98.5 10.2 86.2
Example 11 1550 99.3 15.9 85.7
Example 12 1600 99.5 18.8 85.4
Comparative Example 7 1225 93.2 1.5 ―
Comparative Example 8 1625 99.6 21.0 82.1
Comparative Example 9 1700 99.7 28.2 52.3

Examples 13-16 and Comparative Examples 10-12
A high-purity magnesium oxide raw material powder was produced in the same manner as in Example 1. To this raw material powder, Sc ₂ O ₃ fine powder equivalent to 500 wtppm in terms of Sc and Al ₂ O ₃ fine powder equivalent to 70 wtppm in terms of Al are added to the raw material, mixed, pulverized, and then subjected to CIP at different pressures. By performing molding, molded bodies having different molding densities were produced (Comparative Examples 10 to 12, Example 13). Moreover, according to the same procedure as in Example 1, alcohol slurries with different mixing times were prepared to produce molded bodies with different molding densities (Examples 14 to 16). This molded body was fired at 1350 ° C. in the atmosphere for 3 hours, and then held in Ar gas at 1400 ° C. under a pressure of 196 MPa for 2 hours for HIP treatment. Table 3 shows the molding density and the linear transmittance of the sintered body. Comparative Example 10 has a structure in which a densely sintered portion and a portion where the sintering hardly progresses and where bubbles remain are arbitrarily connected, and the average structure and transmittance are measured. Was impossible. As the molding density increases, the structure gradually becomes uniform, and the transmittance also increases accordingly. From the results in Table 3, it can be seen that a molding density of 58% or more is necessary in order to obtain a sintered body having a transmittance of 85% or more and excellent translucency.

Table 3
Molding density /% Average particle size / μm Linear transmittance /%
Example 13 58.5 9.3 85.4
Example 14 59.9 10.6 85.7
Example 15 61.3 11.2 86.2
Example 16 62.6 11.5 86.4
Comparative Example 10 49.0 ― ―
Comparative Example 11 52.6 5.6 40.8
Comparative Example 12 57.4 7.9 75.7

Examples 17 to 25 and Comparative Examples 13 to 17
A sintered body molded and primary-fired in the same manner as in Example 8 was subjected to HIP treatment at various temperatures, pressures, and times. Table 4 shows the average particle diameter and linear transmittance for each. From these results, it can be seen that even if the HIP treatment is performed at a treatment temperature of 1200 ° C. or more and 1600 ° C. or less and a treatment pressure of 49 MPa or more and 196 MPa or less, the effect is not exhibited. Furthermore, when the HIP temperature is too high, it is understood that, as in the case of atmospheric firing, precipitation of Sc and abnormal grain growth occur, and conversely, the transmittance decreases.

Table 4
Temperature / ° C x Time Pressure Average particle size Linear transmittance
/ hr / MPa / μm /%
Example 17 1200 × 1 196 1.7 85.0
Example 18 1250 × 1 196 2.1 85.1
Example 19 1250 × 2 49 2.5 85.3
Example 20 1300 × 0.5 196 4.1 85.5
Example 21 1450 × 0.5 196 10.8 85.6
Example 22 1450 × 2 98 11.9 86.0
Example 23 1600 × 0.5 196 18.6 86.4
Example 24 1600 × 0.5 98 18.1 86.2
Example 25 1600 × 2 49 19.2 86.4
Comparative Example 13 1150 × 1 196 1.4 69.2
Comparative Example 14 1300 × 1 40 3.7 81.8
Comparative Example 15 1600 × 1 40 18.7 82.5
Comparative Example 16 1650 × 1 196 23.8 75.1
Comparative Example 17 1700 × 0.5 196 30.5 64.6

The characteristic figure which shows the linear transmittance | permeability of the sintered compact of Example 1.

Claims (2)

Sc content is less 2000wtppm or 30Wtppm, Al content is more than 5 wtppm 100 wtppm or less, a purity excluding and Sc ₂ O ₃ and Al ₂ O ₃ 99.9% or more, an average particle size of the sintered body is 1μm or 20μm or less A translucent magnesium oxide sintered body characterized by having a linear transmittance of 85% or more at a thickness of 1 mm over a wavelength region of 500 nm to 6.5 μm. In Sc ₂ O ₃ and Al ₂ O ₃ having a purity of 99.9% or higher with the exception of using the magnesium oxide powder and a binder with a specific surface area 3~15m ² / g, the molding has a density ratio of 58% or more, Sc content Produced a molded body of 30 wtppm or more and 2000wtppm or less, Al content of 5wtppm or more and 100wtppm or less, and after removing the binder by heat treatment,
In a reducing atmosphere, in a vacuum or in the air, primary firing is performed so that the theoretical density ratio is 94% or more at 1250 ° C or more and 1600 ° C or less,
Furthermore, by applying a hot hydrostatic pressure treatment at a temperature of 1200 ° C. to 1600 ° C. and a pressure of 49 MPa to 196 MPa,
Sc content is 30wtppm or more and 2000wtppm or less, Al content is 5wtppm or more and 100wtppm or less, average particle diameter of sintered body is 1μm or more and 20μm or less, and linear transmittance is 1mm thickness over the wavelength region from 500nm to 6.5μm. A method for producing a translucent magnesium oxide sintered body, characterized by comprising a sintered body of 85% or more.

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