JP6585536B2 - Transparent alumina sintered body with holes and manufacturing method thereof - Google Patents

Description

  The present invention relates to a transparent alumina sintered body with holes and a method for producing the same.

  High-density, high-purity polycrystalline alumina is known to have translucency, and can be used for arc tubes for high-pressure sodium lamps, high heat-resistant window materials, semiconductor device members, optical component substrates, and the like. Such polycrystalline alumina is known to exhibit translucency by enhancing orientation (see, for example, Patent Document 1 and Non-Patent Document 1).

JP 2002-293609 A

Ceramics International 38 (2012) 5557-5561

  However, when these transparent alumina sintered bodies were subjected to drilling using mechanical processing, laser processing, chemical processing, or the like, there was a problem that cracks were likely to occur around the hole in any processing method.

  The present invention has been made to solve such problems, and has as its main object to provide a transparent alumina sintered body with a hole in which cracks are unlikely to occur around the hole.

The transparent alumina sintered body with holes of the present invention is
The ratio Mg _H / Mg _{I of the} magnesium amount Mg _H contained in the opening edge of the hole and the magnesium amount Mg _I contained in the transparent alumina sintered body is 1.2 or more.

The method for producing a transparent alumina sintered body with holes of the present invention is as follows.
(A1) a step of producing a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more between the amount of magnesium Mg _S contained in the surface and the amount of magnesium Mg _I contained therein;
(B1) a step of obtaining the above-mentioned transparent alumina sintered body with holes by making a hole in the transparent alumina sintered body;
Or
(A2) A sintered compact with a hole that becomes a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more between the amount of magnesium Mg _S contained in the surface and the amount of magnesium Mg _I contained in the interior is produced. And a process of
(B2) a step of obtaining the above-described transparent alumina sintered body with holes by firing the molded body with holes;
Is included.

The transparent alumina sintered body with a hole of the present invention has a ratio Mg _H / Mg _I of 1.2 between the magnesium amount Mg _H contained in the opening edge of the hole and the magnesium amount Mg _I contained in the transparent alumina sintered body. That's all. It was found that cracks hardly occur in the high magnesium concentration region (opening edge of the hole) of the transparent alumina sintered body, and the yield was improved during product processing. The reason for this is unclear, but it is thought that the strength of the hole opening edge increased due to the high concentration of magnesium.

As described above, the method for producing a transparent alumina sintered body with a hole according to the present invention includes a method of making a hole in the transparent alumina sintered body and a method of firing the molded body with a hole. In the former method, as the transparent alumina sintered body before drilling a hole, the ratio Mg _H / Mg _I between the magnesium amount Mg _H contained in the surface and the magnesium amount Mg _I contained therein is 1.2 or more. Use. In this case, cracks are unlikely to occur around the hole even if drilling is performed. In the latter method, when baking the apertured molded body, the ratio Mg _H / Mg _I is 1.2 or more transparent alumina sintered body of magnesium content Mg _I contained within the amount of magnesium Mg _H contained in the surface Use what Also in this case, cracks hardly occur around the hole of the transparent alumina sintered body with holes. Whichever manufacturing method is adopted, the yield of the transparent alumina sintered body with holes is improved.

Sectional drawing of one Embodiment of the transparent alumina sintered compact 10 with a hole. Sectional drawing of one Embodiment of the transparent alumina sintered compact 20 with a hole. Explanatory drawing of an example of the manufacturing method of the transparent alumina sintered compact 10 with a hole. Explanatory drawing of an example of the manufacturing method of the transparent alumina sintered compact 10 with a hole. Explanatory drawing of the visual field which implemented surface analysis.

The transparent alumina sintered body with a hole of the present invention has a ratio Mg _H / Mg _I of 1.2 between the magnesium amount Mg _H contained in the opening edge of the hole and the magnesium amount Mg _I contained in the transparent alumina sintered body. That's all. FIG.1 and FIG.2 is sectional drawing which shows one Embodiment of the transparent alumina sintered body with a hole of this invention, respectively. The transparent alumina sintered body 10 in FIG. 1 is an example having holes 12 penetrating in the thickness direction, and the transparent alumina sintered body 20 in FIG. 2 is an example having holes 22 recessed in the thickness direction. Opening edges 14 and 24 of the holes 12 and 22 are portions surrounded by a dotted circle in the figure on the surface of the transparent alumina sintered body 10 and 20. The insides 16 and 26 of the transparent alumina sintered bodies 10 and 20 are, for example, portions surrounded by a one-dot chain line circle in the figure.

  In the transparent alumina sintered body with holes of the present invention, the holes may penetrate in the thickness direction of the transparent alumina sintered body with holes (see FIG. 1) or may be recessed without penetrating (see FIG. 2). reference). The use of such a hole is not particularly limited, but in the case of a through hole, for example, it may be used for exposing a button or a switch, or may be used for inserting a screw or a screw. The shape of the hole is not particularly limited, and may be, for example, a round hole or a square hole. Moreover, the transparent alumina sintered body of the present invention is not easily cracked not only during drilling but also during grinding and cutting.

In the transparent alumina sintered body with a hole of the present invention, the ratio Mg _H / Mg _I between the magnesium amount Mg _H contained in the opening edge of the hole and the magnesium amount Mg _I contained in the transparent alumina sintered body is 1.2. The above is preferable, and 1.5 or more is more preferable. If the ratio Mg _H / Mg _I is 1.2 or more, the particle size of alumina in the vicinity of the opening edge of the hole becomes sufficiently small to increase the strength, and cracks are unlikely to occur around the hole. The magnesium amounts Mg _H and Mg _I may be, for example, the amount of magnesium per unit area or the amount of magnesium per unit volume. Further, when the surface analysis of the polished surface after polishing the cross section of the alumina sintered body with holes is performed with an electron beam microanalyzer (EPMA), the Mg-Kα1 spectrum intensity of the opening edge of the holes is Mg _H , The Mg—Kα1 spectral intensity inside the alumina sintered body may be Mg _I. The upper limit of the ratio Mg _H / Mg _I is not particularly limited, but is preferably 3.0 or less, and more preferably 2.0 or less.

In slotted transparent alumina sintered body of the present invention, the ratio N _H / N _I the nitrogen content N _I contained within the nitrogen content N _H and transparent alumina sintered body included in the opening edge of the hole 1.1 The above is preferable, and 1.2 or more is more preferable. If the ratio N _H / N _II is 1.1 or more, cracks are less likely to occur around the hole. The nitrogen amounts N _H and N _I may be, for example, the nitrogen amount per unit area or the nitrogen amount per unit volume. Further, when the surface analysis of the polished surface after polishing the cross section of the alumina sintered body with a hole is performed with an electron beam microanalyzer (EPMA), the N-Kα1 spectrum intensity of the opening edge of the hole is N _H , with the hole. The N-Kα1 spectral intensity inside the alumina sintered body may be N _I. The upper limit of the ratio N _H / N _I is not particularly limited, but is preferably 2.0 or less, and more preferably 1.5 or less. Nitrogen contained in the transparent alumina sintered body with holes is derived from, for example, a nitrogen atmosphere at the time of firing.

The transparent alumina sintered body with a hole of the present invention preferably has a linear transmittance of 50% or more at a wavelength of 300 to 1000 nm when a transparent alumina sintered body with a thickness of 0.5 mm is used. More preferred. The linear transmittance can be measured using a spectrophotometer (for example, Lambda900, manufactured by Perkin Elmer). In addition, what is necessary is just to utilize the following conversion formulas, when converting the thickness of a sample into other thickness. This formula is quoted from Scripta Materialia vol.69, pp362-365 (2013). In the formula, T1 is an actually measured value of linear transmittance, T2 is a linear transmittance after conversion, t1 is an actually measured value of thickness, t2 is a thickness after conversion, and R is a surface reflection derived from a material (0.14 in the case of alumina). It is.
T2 = (1-R) (T1 / (1-R)) ^ (t2 / t1)

The method for producing the transparent alumina sintered body of the present invention is as follows.
(A1) a step of producing a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more between the amount of magnesium Mg _S contained in the surface and the amount of magnesium Mg _I contained therein;
(B1) a step of obtaining the above-mentioned transparent alumina sintered body with holes by making a hole in the transparent alumina sintered body;
Contains or
(A2) A sintered compact with a hole that becomes a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more between the amount of magnesium Mg _S contained in the surface and the amount of magnesium Mg _I contained in the interior is produced. And a process of
(B2) a step of obtaining the above-described transparent alumina sintered body with holes by firing the molded body with holes;
Is included.

  FIG. 3 is an explanatory diagram of an example including the steps (a1) and (b1) in the method for producing a transparent alumina sintered body with holes of the present invention, and FIG. 4 shows the transparent alumina sintered body with holes of the present invention. It is explanatory drawing of an example including process (a2) and (b2) among manufacturing methods.

In the step (a1), for example, 0.005 to 0.5 parts by mass of MgO is added to 100 parts by mass of an alumina raw material powder including a plate-like alumina powder and a fine alumina powder having an average particle size smaller than that of the plate-like alumina powder. A transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more may be produced by molding the molded raw material into a molded body and firing the molded body. FIG. 3A to FIG. 3B are explanatory views of an example of the step (a1). Here, the plain molded body 30 is fired to produce the plain transparent alumina sintered body 40. The surface 44 of the transparent alumina sintered body 40 in FIG. 3B, that is, the fine hatched portion is a region having a high magnesium concentration (region of magnesium amount Mg _S ). The surface 44 is an upper surface, a lower surface, and a side surface of the transparent alumina sintered body 40. Interior 46 That rough areas hatching of the transparent alumina sintered body 40 is a low magnesium concentration region (region of magnesium content Mg _I).

The plate-like alumina powder preferably has an aspect ratio of 3 or more. This is because the degree of orientation of the finally obtained alumina sintered body is increased. The aspect ratio is the average particle diameter / average thickness, the average particle diameter is the average value of the major axis length of the particle plate surface, and the average thickness is the average value of the minor axis length of the particles. These values can be determined by observing 100 arbitrary particles in the plate-like alumina powder with a scanning electron microscope (SEM). The plate-like alumina particles have a substantially hexagonal shape when viewed in plan. As the alumina raw material powder, a mixed alumina powder obtained by mixing a plate-like alumina powder and a fine alumina powder is used. By using such a raw material powder, during firing, the plate-like alumina powder becomes a seed crystal (template), the fine alumina powder becomes a matrix, and the template is homoepitaxially grown while taking in the matrix. Such a manufacturing method is called a TGG method. In the TGG method, the mixing ratio of the plate-like alumina powder and the fine alumina powder is preferably, for example, T: (100-T) (T is 0.001 or more and less than 1) in mass ratio. MgO is known as an additive having an effect of exhausting pores during sintering of alumina. In addition, when MgO is added, the refractive index of MgAl ₂ O ₄ that may be precipitated is close to that of alumina, so the effect on transparency is small.

The molding method is not particularly limited, and examples thereof include tape molding, extrusion molding, casting molding, injection molding, uniaxial press molding, gel casting, and the like. The firing may be atmospheric firing or pressure firing, but pressure firing is preferred. Examples of pressure firing include hot press firing, HIP firing, plasma discharge firing (SPS), and the like. In addition, you may perform a normal pressure preliminary baking before pressure baking. When performing HIP baking, a capsule method can also be used. Pressure when the hot-press firing is preferably 50 kgf / cm ² or more, 200 kgf / cm ² or more is more preferable. Pressure when the HIP sintering is preferably 1000 kgf / cm ² or more, 2,000 kgf / cm ² or more is more preferable. The firing atmosphere is not particularly limited, but is preferably any one of air, an inert gas such as nitrogen and Ar, and a vacuum atmosphere, particularly preferably a nitrogen and Ar atmosphere, and most preferably a nitrogen atmosphere. As conditions for pressure firing, it is preferable to set the firing temperature (maximum temperature) to 1850 to 2050 ° C. and keep at that temperature for 1 to 10 hours. Even if the plate-like alumina powder, fine alumina powder, and MgO powder are almost uniformly dispersed in the above-described molded body, the Mg concentration on the surface becomes higher than the internal Mg concentration by firing. Other Mg components (for example, MgF ₂ or MgNO ₃ ) may be added instead of MgO. In that case, it is preferable to add so that the mass part of Mg component may become the numerical range mentioned above when converted into MgO. When the molded body is fired, a press of 50 kgf / cm ² or more up to a predetermined temperature (temperature set in the range of 1000 to 1400 ° C. (preferably 1100 to 1300 ° C.)) when the temperature is lowered from the highest temperature during firing. It is preferable to apply pressure. By doing in this way, transparency of the obtained sintered compact can be improved. Further, it is preferable that the pressure is reduced to a pressure of less than 50 kgf / cm ² (for example, zero) in a temperature range below the predetermined temperature.

  In the step (a1), a molded body having a surface Mg concentration higher than the internal Mg concentration may be used. For example, the Mg component may be coated on the surface of the molded body by coating or the like. Examples of the coating method include spray coating, dip coating, inkjet coating, spin coating, screen printing, vacuum deposition, sputtering, and CVD. Moreover, when adopting tape molding, the Mg concentration of the lowermost layer or the uppermost layer tape may be higher than that of other tapes.

In the step (b1), it is preferable to make a hole by cutting or the like in the transparent alumina sintered body obtained in the step (a1). Usually, when a hole is made in an alumina sintered body by cutting, cracks often occur around the hole. However, here, a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more is used. In this transparent alumina sintered body, the region (surface) with a high Mg concentration has a higher alumina particle size and a higher strength than the region (inside) with a low Mg concentration. Therefore, even if a hole is made by cutting or the like, cracks are hardly generated at the opening edge of the hole in the surface of the transparent alumina sintered body. FIG. 3B to FIG. 3C are explanatory views of an example of the step (b1). Here, the transparent alumina sintered body 10 with holes is produced by making holes 12 in the plain transparent alumina sintered body 40. is doing. Of the obtained transparent alumina sintered body 10 with a hole, the opening edge 14 of the hole 12 is a region having a high magnesium concentration (region of magnesium amount Mg _S ), and the inside 16 is a region having a low magnesium concentration (region of magnesium amount Mg _I ). It is.

In the step (a2), when the sintered body is formed into a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more between the magnesium amount Mg _S contained in the surface and the magnesium amount Mg _I contained in the interior when sintered. For example, the molded body described in the step (a1) may be manufactured. In this step (a2), a molded body with holes is produced. For example, after forming a molded body, holes may be formed by cutting or the like to form a molded body with a hole, or a molded body with a hole may be manufactured using a mold that becomes a molded body with a hole. FIG. 4A to FIG. 4B are explanatory views of an example of the step (a2). After the above-described molded body 30 is manufactured, a hole 32 is formed by cutting or the like to form a molded body 34 with a hole. is doing.

At a process (b2), the transparent alumina sintered compact with a hole mentioned above is obtained by baking a molded object with a hole. As the firing conditions at this time, for example, the firing conditions described in the step (a1) may be employed. Usually, when an alumina molded body with holes is fired, cracks often occur on the opening edges and inner walls of the holes. However, in this case, the molded body becomes a transparent alumina sintered body having a ratio Mg _H / Mg _I of 1.2 or more between the magnesium amount Mg _H contained in the surface and the magnesium amount Mg _I contained in the interior when fired. Is used. In that case, since the strength of the opening edge of the hole increases as the sintering proceeds, cracks hardly occur around the hole of the transparent alumina sintered body with a hole. FIG. 4B to FIG. 4C are explanatory diagrams of an example of the step (b2), in which the holed compact 34 is fired to produce the holed alumina sintered body 10. In the transparent alumina sintered body 10 with a hole in FIG. 4C, the upper surface, the lower surface, the side surface, and the inner wall surface of the hole 12 (including the hatched portion and the opening edge 14) are regions having a high magnesium concentration, that is, the amount of magnesium Mg. a region of the _S, the internal 16 is a region of low magnesium concentration region or magnesium content Mg _I.

[Experiment 1]
1. Production of alumina sintered body (1) Production of plate-like alumina powder 96 parts by mass of high-purity γ-alumina (TM-300D, manufactured by Daimei Chemical) and high-purity AlF ₃ (
4 parts by mass of Kanto Chemical Co., Ltd., deer special grade), 0.17 parts by mass of high-purity α-alumina (TM-DAR, manufactured by Daimei Chemical, D50 = 1 μm) as a seed crystal, and φ2 mm with IPA (isopropyl alcohol) as a solvent The mixture was mixed in a pot mill for 5 hours. The total mass ratio of impurity elements other than F, H, C, and S in the obtained mixed powder was 1000 ppm or less. 300 g of the obtained mixed raw material powder was placed in a sheath made of high-purity alumina having a purity of 99.5% by mass (volume: 750 cm ³ ), covered with a lid made of high-purity alumina having a purity of 99.5% by mass, and airflow in an electric furnace. Heat treatment was performed at 900 ° C. for 3 hours. The air flow rate was 25000 cc / min. The heat-treated powder was annealed at 1150 ° C. for 40 hours in the atmosphere, and then pulverized for 4 hours using φ2 mm alumina balls to obtain a plate-like alumina powder having an average particle diameter of 2 μm, an average thickness of 0.2 μm, and an aspect ratio of 10. Obtained. The average particle diameter and average thickness of the particles were determined by observing 100 arbitrary particles in the plate-like alumina powder with a scanning electron microscope (SEM). The average particle diameter is the average value of the major axis length of the particle, the average thickness is the average value of the minor axis length of the particle, and the aspect ratio is the average particle diameter / average thickness. The obtained plate-like alumina powder was α-alumina.

(2) Tape molding 2.0 parts by mass of the plate-like alumina powder prepared in the above (1) and 98.0 parts by mass of fine alumina powder (TM-DAR, average particle size 0.1 μm, manufactured by Daimei Chemical) Mixed to obtain mixed alumina powder. With respect to 100 parts by mass of this mixed alumina powder, 0.035 parts by mass of magnesium oxide (500A, manufactured by Ube Materials), 7.8 parts by mass of polyvinyl butyral (product number BM-2, manufactured by Sekisui Chemical Co., Ltd.) as a binder, and plastic 3.9 parts by mass of di (2-ethylhexyl) phthalate (manufactured by Kurokin Kasei) as an agent, 2 parts by mass of sorbitan trioleate (Leodol SP-O30, manufactured by Kao) as a dispersant, and 2-ethylhexanol as a dispersion medium And mixed. The amount of the dispersion medium was adjusted so that the slurry viscosity was 20000 cP. The slurry thus prepared was formed into a sheet shape on a PET film by a doctor blade method so that the thickness after drying was 20 μm. The obtained tape was cut into a circular shape with a diameter of 50.8 mm (2 inches) and then stacked 55 sheets, placed on an Al plate with a thickness of 10 mm, and then placed in a package to create a vacuum. Packed. This vacuum pack was hydrostatically pressed at a pressure of 100 kgf / cm ² in 85 ° C. warm water to obtain a disk-shaped molded body.

(3) Firing The obtained molded body was placed in a degreasing furnace and degreased at 600 ° C. for 10 hours. The obtained degreased body was fired in a nitrogen mold in a hot press at a firing temperature (maximum reached temperature) of 1975 ° C. for 4 hours under a surface pressure of 200 kgf / cm ^{2 to} obtain an alumina sintered body. Obtained. When the temperature was lowered from the firing temperature, the press pressure was maintained up to 1200 ° C., and the press pressure was released to zero in the temperature range below 1200 ° C.

(4) Drilling process The surface of the obtained alumina sintered body (φ50.8 mm, thickness 0.5 mm) was pressed vertically while rotating a disk-shaped diamond grindstone having a diameter of 10 mm and a thickness of 1 mmt, and the alumina sintered body 10 holes were made by grinding until passing through. Ten such alumina sintered bodies with holes were produced (a total of 100 holes).

2. Characteristics of Alumina Sintered Body (1) Linear Transmittance The 0.5 mm thick alumina sintered body obtained in (3) is cut into a size of 10 mm × 10 mm, and fixed to the outermost peripheral part of a φ68 mm metal surface plate at 90 ° intervals, on a SiC abrasive paper Then, lapping was performed (preliminary polishing) for 10 minutes at # 800 and 5 minutes at # 1200 in a state where only the load of the metal surface plate and the polishing jig (1314 g in total) was applied. Thereafter, lapping using diamond abrasive grains was performed on a ceramic surface plate. The lapping was performed at an abrasive grain size of 1 μm for 30 minutes and then at an abrasive grain size of 0.5 μm for 2 hours. The polished 10 mm × 10 mm × 0.5 mm thick sample was washed for 3 minutes each in the order of acetone, ethanol, and ion-exchanged water, and then a straight line at a wavelength of 300 to 1000 nm using a spectrophotometer (Perkin Elmer, Lambda 900). The transmittance was measured. The linear transmittance of the alumina sintered body of Experimental Example 1 at a wavelength of 300 to 1000 nm was 80.1% or more.

(2) Mg _S / Mg _I and N _S / N _I
1 above. After the alumina sintered body obtained in (3) was cut out to a size of 10 mm × 10 mm, an arbitrary cross section was polished with a cross section polisher (CP) (IB-09010CP, manufactured by JEOL Ltd.). CP belongs to the category of ion milling. The reason for using CP is that no degranulation occurs on the polished surface and no work-affected layer remains on the surface. The polished surface was subjected to surface analysis with an electron beam microanalyzer (EPMA) in the field of view A and field of view B shown in FIG. 5 (both 1.5 μm long and 2.0 μm wide). The field of view A is the field of view on the surface of the alumina sintered body, and the field of view B is the field of view inside the alumina sintered body.
Field of view A: Field of view 1 μm below the surface of the fired body Field of view B: Field of view 10 μm below the surface of the fired body

Mg _S / Mg _I = 1.7 when the Mg—Kα1 spectral intensity obtained by the surface analysis of the visual field A is Mg _S , and the Mg—Kα1 spectral intensity obtained by the surface analysis of the visual field B is Mg _I. . Similarly, N _S / N _I = 1.3, where N _S is the N-Kα1 spectral intensity obtained by the surface analysis of the visual field A, and N _I is the N-Kα1 spectral intensity obtained by the surface analysis of the visual field B. Met.

(3) Presence or absence of occurrence of cracks For each hole of the alumina sintered body with holes obtained in (4), it was observed whether or not cracks occurred around the holes with a 50 × optical microscope, and one or more cracks were observed. Counted the number of. As a result, the number of cracked holes was zero (0/100) out of 100.

Note that 2. In (1) and (2), the linear transmittance, Mg _S / Mg _I and N _S / N _I of the alumina sintered body before drilling were measured, but these values are still present after drilling. does not change. Moreover, the opening edge of the hole of the alumina sintered body with a hole can be regarded as a part of the surface. Therefore, if the Mg-Kα1 spectrum intensity at the opening edge of the hole is Mg _H and the N-Kα1 spectrum intensity is N _H , it can be regarded as Mg _H = Mg _S and N _H = N _S.

[Experiment 2]
Experimental Example 1 Ten compacts obtained in (2) were prepared and In the same manner as in (4), 10 holes each having a diameter of 10 mm were formed (a total of 100 holes). The molded body after the drilling process was subjected to 1. Hot press firing was performed under the firing conditions of (3) to obtain an alumina sintered body with holes. The characteristics of the alumina sintered body with holes were measured in the same manner as in Experimental Example 1. As a result, the linear transmittance was 80.6% when the thickness was 0.5 mm, Mg _S / Mg _I was 1.7, and N _S / N. _I was 1.3, and the number of cracked holes was zero out of 100.

In this case as well, if the Mg-Kα1 spectral intensity at the opening edge of the hole of the alumina sintered body with holes is Mg _H and the N-Kα1 spectral intensity is N _H , then Mg _H = Mg _S and N _H = N _S Can be considered.

[Experiment 3]
Experimental Example 1 In the tape molding of (2), 2.5 parts by mass of plate-like alumina powder and 97.5 parts by mass of fine alumina powder were mixed to add 0.05 parts by mass of magnesium oxide. A sintered alumina body with a hole was produced in the same manner as in Experimental Example 1 except that the firing temperature (maximum temperature reached) was 1850 ° C. in the firing of (3). The linear transmittance of the alumina sintered body of this experimental example was 81.1% at a thickness of 0.5 mm, Mg _S / Mg _I was 1.5, and N _S / N _I was 1.2. Moreover, the number of the holes which the crack of the alumina sintered body with a hole generate | occur | produced was zero (0/100).

[Experimental Example 4]
Ten molded articles obtained after the tape molding in Experimental Example 3 were prepared. In the same manner as in (4), 10 holes each having a diameter of 10 mm were formed (a total of 100 holes). The formed body after drilling was hot-press fired under the firing conditions of Experimental Example 3 to obtain an alumina sintered body with holes. The characteristics of the alumina sintered body with holes were measured in the same manner as in Experimental Example 1. As a result, the linear transmittance was 81.3% when the thickness was 0.5 mm, Mg _S / Mg _I was 1.5, and N _S / N. _I was 1.2, and the number of cracked holes was zero (0/100) out of 100.

[Experimental Example 5]
Experimental Example 1 A sintered alumina body with a hole was produced in the same manner as in Experimental Example 1, except that the firing temperature (maximum temperature reached) was 1900 ° C. in the firing of (3). The linear transmittance of the alumina sintered body of this experimental example was 76.6% at a thickness of 0.5 mm, Mg _S / Mg _I = 1.3, and N _S / N _I = 1.1. Moreover, the number of the holes which the crack of the alumina sintered body with a hole generate | occur | produced was 13 out of 100 (13/100).

[Experimental Example 6]
Ten molded articles obtained after the tape molding of Experimental Example 5 were prepared. In the same manner as in (4), 10 holes each having a diameter of 10 mm were formed (a total of 100 holes). The formed body after drilling was hot-press fired under the firing conditions of Experimental Example 5 to obtain a holed alumina sintered body. The characteristics of the alumina sintered body with holes were measured in the same manner as in Experimental Example 1. As a result, the linear transmittance was 75.3% at a thickness of 0.5 mm, Mg _S / Mg _I was 1.3, and N _S / N. _I was 1.1 and the number of cracked holes was 7 out of 100 (7/100).

[Experimental Example 7]
Experimental Example 1 An alumina sintered body with a hole was produced in the same manner as in Experimental Example 1 except that magnesium oxide was not added in the tape molding of (2). The linear transmittance of the alumina sintered body of this experimental example was 75.2% at a thickness of 0.5 mm. Example 1-2. In the electron beam microanalyzer measurement of (2), Mg _S and Mg _I were detected only at the background level, and N _S / N _I was 1.1. Moreover, the number of the holes which the crack generate | occur | produced the alumina sintered compact with a hole was 43 out of 100 (43/100).

[Experimental Example 8]
Ten molded articles obtained after the tape molding of Experimental Example 7 were prepared. In the same manner as in (4), 10 holes each having a diameter of 10 mm were formed (a total of 100 holes). The formed body after drilling was hot-press fired under the firing conditions of Experimental Example 7 to obtain an alumina sintered body with holes. When the characteristics of the alumina sintered body with holes were measured in the same manner as in Experimental Example 1, the linear transmittance was 73.6% at a thickness of 0.5 mm, and Mg _S and Mg _I were detected only at the background level. , N _S / N _I 1.0, the number of generated holes cracks was 29 in 100 (29/100).

[Experimental Example 9]
Experimental Example 1 In the firing of (3), an alumina sintered body with holes was produced in the same manner as in Experimental Example 1 except that the temperature was immediately lowered without reaching after reaching the firing temperature (maximum temperature reached). The linear transmittance of the alumina sintered body of this experimental example was 78.9% at a thickness of 0.5 mm, Mg _S / Mg _I = 1.15, and N _S / N _I = 1.05. Moreover, the number of the holes which the crack of the alumina sintered body with a hole generate | occur | produced was 21 out of 100 (21/100).

[Experimental Example 10]
Ten molded articles obtained after the tape molding of Experimental Example 9 were prepared. In the same manner as in (4), 10 holes each having a diameter of 10 mm were formed (a total of 100 holes). The formed body after drilling was hot-press fired under the firing conditions of Experimental Example 9 to obtain an alumina sintered body with holes. When the characteristics of the alumina sintered body with holes were measured in the same manner as in Experimental Example 1, the linear transmittance was 79.5% at a thickness of 0.5 mm, Mg _S / Mg _I was 1.15, N _S / N _I was 1.05 and the number of cracked holes was 14 out of 100 (14/100).

  Experimental examples 1 to 6 correspond to examples of the present invention, and experimental examples 7 to 10 correspond to comparative examples. The present invention is not limited to the above-described embodiments and experimental examples, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

10 transparent alumina sintered body, 12 holes, 14 opening edge, 16 inside transparent alumina sintered body, 20 transparent alumina sintered body, 22 holes, 24 opening edge, 26 inside transparent alumina sintered body, 30 molded body, 32 holes, 34 molded body, 40 transparent alumina sintered body, 44 surface of transparent alumina sintered body, 46 inside transparent alumina sintered body.

Claims (5)

The ratio Mg _H / Mg _I and magnesium content Mg _I contained within the magnesium content Mg _H and transparency alumina sintered body included in the opening edge of the hole is 1.2 or more, it is included in the opening edge of the hole the ratio N _H / N _I the nitrogen content N _I contained inside the transparent alumina sintered body with the nitrogen content N _H is 1.1 or more,
Transparent alumina sintered body with holes. The Mg _H / Mg _I is a surface analysis of the polished surface after the cross section of the transparent alumina sintered body is polished with an electronic microanalyzer, and the Mg-Kα1 spectral intensity of the opening edge of the hole is Mg _H. It is a value calculated as the Mg-Kα1 spectral intensity inside the alumina sintered body as Mg _I.
The transparent alumina sintered body with holes according to claim 1. The N _H / N _I is a surface analysis of the polished surface after the cross section of the transparent alumina sintered body is polished with an electronic microanalyzer, and the N-Kα1 spectral intensity of the opening edge of the hole is N _H. the interior of the N-K.alpha.1 spectral intensity of the alumina sintered body is calculated values as N _I,
The transparent alumina sintered body with holes according to claim 1 or 2 . (A) the ratio Mg _S / Mg _I and magnesium content Mg _I contained within the amount of magnesium Mg _S contained in the surface is 1.2 or more, a nitrogen contained within the nitrogen content N _S contained in the surface weight a step of the ratio N _S / N _I with N _I to prepare a transparent alumina sintered body is 1.1 or more,
(B) obtaining the transparent alumina sintered body with holes according to claim 1 by making a hole in the transparent alumina sintered body;
Of transparent alumina sintered body with holes including (A) When sintered, a molded body with a hole that becomes a transparent alumina sintered body having a ratio Mg _S / Mg _I of 1.2 or more between the amount of magnesium Mg _S contained in the surface and the amount of magnesium Mg _I contained therein is made And a process of
(B) obtaining the transparent alumina sintered body with holes according to claim 1 by firing the molded body with holes in a nitrogen atmosphere ;
Of transparent alumina sintered body with holes including

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