Yttrium aluminum garnet sintered body and method for producing same

Abstract

The present invention provides a YAG sintered body that exhibits high transparency and that can be produced in a short oxygen annealing treatment time.　The present invention provides an yttrium aluminum garnet sintered body that is characterized by comprising silicon and a second group element and by exhibiting an optical loss coefficient of 0.002 cm-1 or less when light having a wavelength of 300-2500 nm (excluding a wavelength in which absorption by an additive element is present) is passed therethrough.

Description

Yttrium aluminum garnet sintered body and method for manufacturing the same.

[0001] The present invention relates to a yttrium aluminum garnet sintered body and a method for producing the same.

[0002] Conventionally, yttrium aluminum garnet (hereinafter also referred to as "YAG") sintered bodies have been used as laser oscillators. Laser beams are used in various applications such as medical scalpels and processing of materials such as metals, and YAG sintered bodies are required to function as high-power laser media. Such YAG sintered bodies are required to have high transparency.

[0003] As a transparent YAG sintered body, the optical loss coefficient when transmitting light with wavelengths of 300 to 1500 nm is 0.002 cm². －１ The following polycrystalline YAG sintered body has been proposed (see Patent Document 1).

[0004] Patent No. 6502595

[0005] Generally, to obtain a transparent YAG sintered body, it is necessary to add silicon as a sintering aid and perform high-temperature, high-pressure treatment under an inert atmosphere (hereinafter also referred to as "HIP treatment"). However, in the case of a YAG sintered body to which only silicon is added, the Al, which was originally trivalent, ３＋ A portion of it is tetravalent silicon (Si ４＋ ) is replaced by Y in the YAG sintered body, so when HIP treatment is performed, ３＋ It is reduced to Y ２＋ As a result, the YAG sintered body becomes discolored, leading to a decrease in light transmittance. Such YAG sintered bodies cannot be used as a medium for high-power lasers. Therefore, it is necessary to perform heat treatment in an oxygen-containing atmosphere (hereinafter also referred to as "oxygen annealing") on the YAG sintered body after HIP treatment to eliminate the discoloration. However, a problem arises in that oxygen annealing takes a long time for thick YAG sintered bodies.

[0006] In view of the above circumstances, the present invention aims to provide a YAG sintered body that exhibits high transparency and can be manufactured with a short oxygen annealing treatment time. Furthermore, the present invention aims to provide a manufacturing method that can produce a YAG sintered body that exhibits high transparency and has a short oxygen annealing treatment time.

[0007] As a result of diligent research, the inventors have found that by simultaneously adding silicon and a group 2 element as sintering aids to a YAG sintered body, the oxygen annealing time required for the coloration of the sintered body after HIP treatment to disappear can be significantly reduced, and a YAG sintered body with high transparency can be obtained.

[0008] In other words, the present invention relates to the following YAG sintered body and method for producing the same: 1. A material containing silicon and a group II element, with a light loss coefficient of 0.002 cm when light with a wavelength of 300 to 2500 nm (excluding wavelengths where absorption occurs due to added elements) is transmitted through it. －１ A yttrium aluminum garnet sintered body characterized by the following: 2. The yttrium aluminum garnet sintered body according to item 1, wherein the group 2 element comprises magnesium and / or calcium. 3. The yttrium aluminum garnet sintered body according to item 2, wherein the molar ratio ((Mg + Ca) / Si) of the total number of moles of magnesium and calcium to the number of moles of silicon is 15 or less. 4. The yttrium aluminum garnet sintered body according to any one of items 1 to 3, wherein the average crystal grain size is less than 5 μm. 5. The optical loss coefficient for light with a wavelength of 633 nm is 0.002 cm². －１ The yttrium aluminum garnet sintered body described in any of items 1 to 4 below: 6. The optical loss coefficient for light with a wavelength of 1064 nm is 0.002 cm². －１The yttrium aluminum garnet sintered body according to any one of Items 1 to 5 below. 7. A method for manufacturing a yttrium aluminum garnet sintered body, comprising: (1) Step 1 of preparing a slurry containing yttrium aluminum garnet powder and a sintering aid, and curing it to produce a formed body; (2) Step 2 of firing the formed body; (3) Step 3 of subjecting the fired formed body to high-temperature and high-pressure treatment in an inert atmosphere; and (4) Step 4 of producing a sintered body by subjecting the formed body subjected to high-temperature and high-pressure treatment to oxygen annealing treatment. The sintering aid includes a silicon-containing compound and a Group II element-containing compound. The sintered body has a light loss coefficient of 0.002 cm when transmitting light with a wavelength of 300 to 2500 nm (excluding wavelengths with absorption due to added elements). －１ The following, characterized by the manufacturing method. 8. The silicon-containing compound contains SiO ２ The manufacturing method according to Item 7, including. 9. The manufacturing method according to Item 7 or 8, wherein the Group II element-containing compound includes a magnesium-containing compound and / or a calcium-containing compound. 10. The manufacturing method according to Item 9, wherein the molar ratio ((Mg + Ca) / Si) of the total number of moles of magnesium and calcium in the sintering aid to the number of moles of silicon is 15 or less.

[0009] The YAG sintered body of the present invention exhibits high transparency and can be manufactured with a short oxygen annealing treatment time. Also, the manufacturing method of the YAG sintered body of the present invention has a short oxygen annealing treatment time and can manufacture a YAG sintered body exhibiting high transparency.

[0010] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

[0011] In the numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step can be arbitrarily combined with the upper or lower limit of a numerical range in another step. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of a numerical range may be replaced with values ​​shown in the examples or values ​​that can be uniquely derived from the examples. Moreover, in this specification, numbers connected by "~" mean a numerical range that includes the numbers before and after "~" as the lower and upper limits, respectively.

[0012] In this specification, the expressions “contains” and “includes” include the concepts of “contains,” “includes,” “substantially consists of,” and “consistes of only.”

[0013] 1. YAG Sintered Body The YAG sintered body of the present invention contains silicon and a group 2 element, and has an optical loss coefficient of 0.002 cm when light with a wavelength of 300 to 2500 nm (excluding wavelengths where absorption occurs due to added elements) is transmitted through it. －１ The following is the YAG sintered body. The YAG sintered body of the present invention having the above characteristics contains silicon and a group 2 element simultaneously, thereby achieving a charge balance throughout the sintered body, and the Y in the YAG sintered body that causes discoloration after HIP treatment. ２＋ This suppresses the generation of [unclear] and shortens the oxygen annealing time.

[0014] The YAG sintered body of the present invention (hereinafter also simply referred to as "sintered body") will be described in detail below.

[0015] The sintered body of the present invention contains silicon and a group 2 element as sintering aids. In the sintered body of the present invention, silicon and the group 2 element are silicon derived from a silicon-containing compound and a group 2 element derived from a group 2 element compound, respectively, in the method for producing the sintered body of the present invention described later.

[0016] The Group II elements are not particularly limited, and known Group II elements can be used. Specifically, examples of Group II elements include Be, Mg, Ca, Sr, Ba, and Ra. Among these, Mg and Ca are preferred, and Ca is more preferred, from the viewpoint of further improving the transparency of the sintered body.

[0017] The above Group II elements can be used singly or in combination of two or more.

[0018] In the YAG sintered body of the present invention, the Y element constituting the YAG sintered body may be added with an element from Ce with an atomic number of 57 to Yb with an atomic number of 70 among the rare earth elements and substitutionally solid-solved, or the Al element constituting the YAG sintered body may be added with an element from Ti with an atomic number of 22 to Ni with an atomic number of 28 among the transition metals and substitutionally solid-solved. In this specification, these elements are referred to as "added elements". Of course, the YAG sintered body of the present invention may be YAG itself without adding anything.

[0019] The molar ratio ((Mg + Ca) / Si) of the total number of moles of magnesium and calcium in the sintered body to the number of moles of silicon is preferably 15 or less, more preferably 10 or less, still more preferably 7.5 or less, particularly preferably 5 or less, and most preferably 3 or less. When the upper limit of the above molar ratio is within the above range, compared with a sintered body containing only silicon, the oxygen annealing treatment time can be made shorter without impairing transparency. Also, the lower limit of the above molar ratio is not particularly limited and may be 0, 0.1, 0.2, 0.3, 0.5, etc.

[0020] The total content of silicon and the Group II element in the sintered body is not particularly limited as long as the sintered body can exhibit high transparency and can be adjusted as appropriate.

[0021] In this specification, the measurement of the content of silicon and the Group II element in the sintered body can be carried out by pulverizing the sintered body, dissolving it in a strong acid aqueous solution, and measuring it by ICP emission spectrometry (ICP-AES).

[0022] The light loss coefficient of the sintered body of the present invention when transmitting light with a wavelength of 300 to 2500 nm is 0.002 cm －１ or less. When the light loss coefficient exceeds 0.002 cm －１ , the transparency of the sintered body becomes insufficient. The above light loss coefficient is preferably 0.0015 cm －１ or less, and more preferably 0.001 cm －１ or less. Also, the lower limit of the above light loss coefficient is not particularly limited and may be 0 cm －１ , 0.0001 cm－１ , 0.0002 cm －１ , 0.0003 cm －１ , 0.0005 cm －１ may be, for example, etc.

[0023] In the present invention, the optical loss coefficient is measured for the sintered body of the present invention, excluding wavelengths with absorption by the additive element. For example, when no additive element is introduced, the optical loss coefficient in the wavelength range of 300 to 2500 nm is measured. Also, for example, when Nd is added, since there is light absorption by the additive element at wavelengths of 300 to 1000 nm, the optical loss coefficient at a wavelength excluding that, for example, at a wavelength of 1064 nm, is measured. The optical loss coefficient measured at these wavelengths may be 0.002 cm －１ or less.

[0024] When the sintered body becomes opaque due to sintering unevenness or the like, the optical loss coefficient decreases over the entire measurement wavelength region (300 to 2500 nm). Therefore, even if the optical loss coefficient of the wavelength region with light absorption by the additive element is excluded as described above, no particular problem occurs. The light absorption wavelength due to the additive element can be grasped in advance, for example, by producing or procuring a YAG single crystal into which the additive element has been introduced and performing absorption spectrum measurement on it.

[0025] The optical loss coefficient in the present invention is calculated using the following formula using the light transmittance at each wavelength measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.). [Optical loss coefficient (% / cm)] = (-1 / L) × ln(T / T ０ ) Here, L is the distance (cm) of light passing through the measurement sample, T is the light transmittance of the measurement sample, and T ０ is the light transmittance of a YAG sintered body substrate containing no additive element with a thickness of 0.2 mm. Both end faces of each sample have a parallelism (error from a completely parallel state) of 30 seconds or less, a flatness of λ / 10 or less (λ is the measurement wavelength), and a surface roughness (Ra) of 0.5 nm or less by polishing. However, in the measurement of the optical loss coefficient, wavelengths with absorption by the additive element are excluded.

[0026] In the sintered body of the present invention, the average crystal grain size is preferably less than 5 μm, and more preferably 3 μm or less. Furthermore, the average crystal grain size is preferably 1.0 μm or more, and more preferably 1.5 μm or more. By having the upper limit of the average crystal grain size within the above range, the annealing treatment time of the sintered body can be further shortened. Furthermore, by having the lower limit of the average crystal grain size within the above range, the transparency of the sintered body is further improved.

[0027] The average grain size (μm) can be determined using the following formula by the measurement method described below: Average grain size (μm) = 1.56 × L / (N-1) The surface of the obtained sintered body is flattened using a surface grinder and then mirror-polished. The mirror-polished sample is heat-treated at 1400-1500°C for 1 hour, for example in air, to induce intergranular corrosion. A surface photograph of this sample is taken using an SEM or optical microscope, and five straight lines are drawn randomly on the photograph. Let N be the number of grain boundaries on each straight line, and L (μm) be the distance between the lines, determined from the magnification and scale of the surface photograph. The average of the five calculated values ​​is taken as the measured average grain size.

[0028] 2. Method for Manufacturing a YAG Sintered Body The method for manufacturing a YAG sintered body of the present invention comprises: (1) Step 1 of preparing a slurry containing YAG powder and a sintering aid, and curing it to prepare a molded body; (2) Step 2 of firing the molded body; (3) Step 3 of subjecting the fired molded body to high temperature and high pressure in an inert atmosphere; and (4) Step 4 of oxygen annealing the molded body that has been subjected to high temperature and high pressure to produce a sintered body, wherein the sintering aid contains a silicon-containing compound and a group 2 element-containing compound, and the sintered body has a light loss coefficient of 0.002 cm when light with a wavelength of 300 to 2500 nm (excluding wavelengths where absorption occurs due to added elements) is transmitted through it. －１ The present invention is characterized by the following. The manufacturing method of this invention will be described in detail below for each step.

[0029] (Step 1) Step 1 is a process of preparing a slurry containing YAG powder and a sintering aid, and curing it to produce a molded body.

[0030] The YAG powder is not particularly limited, and YAG powder obtained by adding a mixed solution containing a yttrium-containing compound and an aluminum-containing compound dropwise to an aqueous solution containing an ammonium salt, reacting the resulting amorphous precipitate, and calcining it can be used. Commercially available YAG powder may also be used. Alternatively, a mixed powder of aluminum oxide and yttrium oxide powder weighed to achieve a YAG composition may be used.

[0031] The sintering aid used in step 1 includes a silicon-containing compound and a group 2 element-containing compound. The silicon and group 2 elements added as sintering aids exist as tetravalent and divalent cations, respectively, in the YAG sintered body. In the case of a YAG sintered body containing only silicon as a sintering aid, the HIP treatment is performed in step 3, described later, which reduces the Y ions in the YAG. ３＋ A portion of it is reduced to make the total charge of YAG zero, Y ２＋ This is the result. Y ２＋ Although this is the cause of discoloration of the YAG sintered body, in the manufacturing method of the present invention, for example, Si ４＋ and Ca ２＋ By containing a divalent cation derived from a group 2 element compound such as Y, ２＋ This suppresses the occurrence of [unclear] and reduces the discoloration of the manufactured YAG sintered body. As a result, the oxygen annealing time required to eliminate discoloration of the YAG sintered body after HIP treatment can be shortened.

[0032] The silicon-containing compound is not particularly limited as long as it contains silicon, and any known silicon-containing compound can be used. Such silicon-containing compounds include SiO ２ TEOS (tetraethoxysilane, Si (OC) ２ H ５ ) ４ ) are some examples, and among these, SiO ２ This can be suitably used.

[0033] The group second element-containing compound is not particularly limited as long as it contains a group second element. Specifically, group second elements include Be, Mg, Ca, Sr, Ba, and Ra. Among these, Mg and Ca are preferred from the viewpoint of shortening the annealing time of the sintered body and further improving the transparency of the sintered body.

[0034] As Group II element-containing compounds, magnesium-containing compounds and calcium-containing compounds are preferred, and calcium-containing compounds are more preferred. Furthermore, as Group II element-containing compounds, examples include oxides, chlorides, fluorides, and carbonates of the above-mentioned Group II elements, and among these, oxides and carbonates can be suitably used. Specifically, as Group II element-containing compounds, examples include magnesium oxide, calcium oxide, magnesium chloride, calcium chloride, magnesium carbonate, and calcium carbonate. Among these, magnesium oxide and calcium carbonate are preferred, and calcium carbonate is more preferred, from the viewpoint of further shortening the annealing treatment time of the sintered body and further improving the transparency of the sintered body.

[0035] In step 1, the molar ratio ((Mg + Ca) / Si) of the total number of moles of magnesium and calcium in the sintered body to the number of moles of silicon is preferably 15 or less, more preferably 10 or less, even more preferably 7.5 or less, particularly preferably 5 or less, and most preferably 3 or less. By having the upper limit of the above molar ratio be within the above range, the annealing treatment time of the sintered body can be shortened and the transparency of the sintered body can be further improved. Furthermore, the lower limit of the above molar ratio is not particularly limited and may be 0, 0.1, 0.2, 0.3, 0.5, etc.

[0036] The slurry used in step 1 may contain a surfactant. The surfactant is not particularly limited, and any known polymer compound used as a surfactant can be used.

[0037] Examples of the above-mentioned surfactants include cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants. These surfactants can be used individually or in combination of two or more.

[0038] The slurry used in step 1 may contain water and / or alcohol as a dispersion medium. The alcohol is not particularly limited as long as it can disperse the YAG powder and the sintering aid, and any known alcohol can be used.

[0039] Examples of alcohols include those having 1 to 10 carbon atoms. The number of carbon atoms in the alcohol is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 to 2. Specifically, methanol and ethanol are suitably used as such alcohols.

[0040] In step 1, a slurry containing the above-mentioned YAG powder and sintering aid is prepared and cured to produce a molded body. The method for curing the slurry is not particularly limited; for example, the slurry may be poured into a plaster mold and cured at approximately 490 kPa (approximately 5 kgf / cm²). ２ One method involves press-fitting the material under pressure and then molding it.

[0041] In step 1, the molded body formed as described above may be degreased. The method of degreasing is not particularly limited, and for example, heating at a temperature of 400 to 800°C is one method.

[0042] In the process described above, step 1 causes the slurry containing YAG powder and sintering aid to harden, and a molded body is prepared.

[0043] (Step 2) Step 2 is the process of firing the molded body. The firing method is not particularly limited and can be done by known methods such as leaving it in a high-temperature electric furnace for a certain period of time.

[0044] The firing temperature can be adjusted as appropriate; for example, 1000 to 1800°C is preferred, 1300 to 1750°C is more preferred, and 1500 to 1700°C is even more preferred.

[0045] The firing time can be set appropriately according to the firing temperature, etc., for example, 1 to 10 hours is preferred, 1.5 to 7 hours is more preferred, and 2 to 5 hours is even more preferred.

[0046] In step 2, it is preferable to perform the firing under vacuum conditions. Vacuum firing further improves transparency.

[0047] In step 2, as described above, the molded body prepared in step 1 is fired.

[0048] (Step 3) Step 3 is a process in which the fired molded body is subjected to high temperature and high pressure in an inert atmosphere. Step 3 is a so-called HIP (Hot Isostatic Pressing) process. Step 3 further improves the transparency, mechanical impact resistance, and thermal impact resistance of the manufactured YAG sintered body.

[0049] In step 3, HIP treatment is performed under an inert atmosphere, which results in YAG containing only silicon derived from the sintering aid. ３＋ A portion of it is reduced to make the total charge of YAG zero, Y ２＋ This is the result. Y ２＋ This is the cause of discoloration of the YAG sintered body, but in the manufacturing method of the present invention, by performing oxygen annealing treatment in step 4 described later, Y ２＋ Because oxygen ions that cancel out the charge are supplied to the YAG sintered body, Y ２＋ Since the charge becomes zero and the coloration disappears, the manufactured YAG sintered body can exhibit high transparency.

[0050] In step 3, the firing is carried out under an inert atmosphere. The inert atmosphere is not particularly limited and can be selected as appropriate, for example, a nitrogen atmosphere or an argon atmosphere. Among these, an argon atmosphere is more preferred.

[0051] The processing temperature can be adjusted as appropriate; for example, 1350 to 1850°C is preferred.

[0052] The processing pressure can be adjusted as appropriate; for example, 50 to 200 MPa is preferred.

[0053] The processing time can be set appropriately according to the firing temperature, etc., and for example, 1 to 30 hours is preferred.

[0054] In step 3 described above, the fired molded body is subjected to high-temperature and high-pressure treatment in an inert atmosphere.

[0055] (Step 4) Step 4 is a process in which a molded body that has been treated at high temperature and high pressure is subjected to oxygen annealing to produce a sintered body. Oxygen annealing is a process in which heat treatment is performed in an oxygen-containing atmosphere under air or under a constant pressure. By applying oxygen annealing to the molded body, the discoloration of the produced sintered body is eliminated.

[0056] By performing oxygen annealing in step 4, the YAG sintered body that was colored in the HIP treatment of step 3 described above can be made transparent. That is, the YAG produced by the HIP treatment in step 3 ２＋ However, by performing oxygen annealing in step 4, Y ２＋ Oxygen ions that neutralize the charge are supplied to the YAG sintered body, and the discoloration of the YAG sintered body is eliminated.

[0057] The oxygen annealing temperature can be adjusted as appropriate, for example, 1000 to 1500°C is preferred.

[0058] The pressure during oxygen annealing can be adjusted as appropriate; for example, atmospheric pressure to 200 MPa is preferred.

[0059] The oxygen annealing time can be adjusted as needed, allowing the YAG sintered body to be treated for any desired time until the coloring disappears.

[0060] Through the process described above (step 4), the molded body that has undergone high-temperature and high-pressure treatment is subjected to oxygen annealing to produce a sintered body.

[0061] The YAG sintered body produced by the manufacturing method of the present invention has an optical loss coefficient of 0.002 cm² when light with a wavelength of 300 to 2500 nm (excluding wavelengths where absorption occurs due to added elements) is transmitted through it. －１ The following can be achieved, and even if the thickness of the sintered body is thick, the time required for the discoloration to be eliminated by oxygen annealing (oxygen annealing time) is shortened. Such a YAG sintered body of the present invention can be usefully used as a laser oscillation element. The YAG sintered body of the present invention can be usefully used as a high-power laser oscillation element for various applications such as medical scalpels and processing of materials such as metals.

[0062] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples.

[0063] (Example 1) A 0.5 mol / L aqueous solution of yttrium nitrate and a 0.5 mol / L aqueous solution of aluminum nitrate were weighed to have a molar ratio of yttrium to aluminum of 3:5, and then mixed in a reaction vessel to obtain a mixed solution of YAG composition. This solution was added dropwise at a rate of 28 ml / min to a 2 mol / L aqueous solution of ammonium bicarbonate, to which ammonia water was added to bring the pH to 8.0. During this time, both the mixed solution of YAG composition and the aqueous solution of ammonium bicarbonate were maintained at 25°C in a constant temperature bath. The minimum pH value during the dropwise addition was 7.0, and the pH reached a constant value of 8.0 about 3 hours after the completion of the dropwise addition. After the completion of the dropwise addition, the solution was aged at 25°C for 24 hours, and then filtered and washed with water four times. Repeated filtering and washing reduced the anions, nitrate ions and free carbonate ions, which are impurities in the precipitate, to 2000 wt ppm or less. The precipitate after washing was amorphous, but granular in form, making it easy to filter and wash, and its composition was carbonate or basic carbonate.

[0064] This amorphous precipitate was dried in air at 120°C, and then calcined in air at 1300°C for 3 hours to prepare a YAG powder with excellent dispersibility, having an average particle size of 0.1 μm for primary particles and 0.18 μm for secondary particles.

[0065] 75 g of prepared YAG raw material powder, 50 g of ethanol, 1 g of Floren G-7000 (manufactured by Kyoeisha Chemical) as a dispersant, and nylon balls are added to a nylon pot for ball mill grinding, and a silicon-containing compound SiO is used as a sintering aid. ２ The following was added: The amount of sintering aid added was 80 wt ppm in terms of metal equivalent relative to the YAG powder. Then, it was mixed for about 20 hours. The resulting slurry was degassed in a vacuum degasser for about 30 minutes and placed in a plaster mold with approximately 490 kPa (approximately 5 kgf / cm²). ２ The molded body was obtained by press-fitting with the following pressure. The obtained molded body was thoroughly dried at room temperature and degreased at 750°C for 100 hours under air (Step 1).

[0066] Next, the molded body was vacuum-fired at 1650°C for 3 hours (Step 2).

[0067] The fired molded body was subjected to high-temperature and high-pressure treatment under conditions of 1720°C and 147 MPa in an inert atmosphere (argon) (step 3).

[0068] A molded body that had undergone high-temperature and high-pressure treatment was subjected to oxygen annealing at 1200°C for 100 hours under atmospheric conditions to produce a sintered body (Step 4). The molar ratio (Ca / Si) of calcium atoms to silicon atoms in the produced sintered body was 0 because calcium was not used as a sintering aid.

[0069] (Examples 2-8, Comparative Examples 1 and 2) As a sintering aid, silicon-containing compound SiO ２ A sintered body was manufactured in the same manner as in Example 1, except that calcium carbonate, a group 2 element, was added to change the molar ratio of calcium atoms to silicon atoms (Ca / Si) of the sintered body as shown in Table 1, and the oxygen annealing time was adjusted as shown in Table 1.

[0070] (Evaluation Method) The following evaluations were performed on the examples and comparative examples.

[0071] The molar ratio (Ca / Si) of calcium atoms to silicon atoms in the sintered body was measured using the following method. Specifically, the YAG sintered body was finely pulverized, dissolved in a strong acid aqueous solution, and measured by ICP emission spectrometry (ICP-AES).

[0072] The optical loss coefficient of the sintered body was measured when light with wavelengths of 300 to 2500 nm was transmitted through it using the following measurement method. Specifically, the optical transmittance at each wavelength measured using a spectrophotometer (Hitachi U-4100) was used, and the coefficient was calculated using the following formula: [Optical loss coefficient (% / cm)] = (-1 / L) × ln(T / T) ０ ) Here, L is the distance (cm) of light passing through the sample, T is the light transmittance of the sample, T ０This represents the light transmittance of a 0.2 mm thick YAG sintered substrate that does not contain any added elements. The parallelism (error from a perfectly parallel state) of both end faces of each sample was set to 30 seconds or less, the flatness to λ / 10 or less (λ is the measurement wavelength) was polished to 0.5 nm or less, and the surface roughness (Ra) was set to 0.5 nm or less. However, in the measurement of the above light loss coefficient, wavelengths where absorption occurs due to added elements were excluded.

[0073] The transparent sintered body was visually observed, and its transparency was evaluated according to the following criteria: ○: No discolored areas are present in the sintered body. ×: Discolored areas are present in the sintered body.

[0074] The results are shown in Table 1.

[0075]

Claims

1. A material containing silicon and Group II elements, with a light loss coefficient of 0.002 cm² when transmitting light with a wavelength of 300 to 2500 nm (excluding wavelengths where absorption occurs due to added elements). －１ A yttrium aluminum garnet sintered body characterized by the following:

2. The yttrium aluminum garnet sintered body according to claim 1, wherein the group 2 element comprises magnesium and / or calcium.

3. The yttrium aluminum garnet sintered body according to claim 2, wherein the molar ratio ((Mg + Ca) / Si) of the total number of moles of magnesium and calcium to the number of moles of silicon is 15 or less.

4. The yttrium aluminum garnet sintered body according to claim 1, wherein the average crystal grain size is less than 5 μm.

5. The optical loss coefficient for light with a wavelength of 633 nm is 0.002 cm². －１ The yttrium aluminum garnet sintered body according to claim 1 is as follows:

6. The optical loss coefficient for light with a wavelength of 1064 nm is 0.002 cm². －１ The yttrium aluminum garnet sintered body according to claim 1 is as follows:

7. A method for producing a yttrium aluminum garnet sintered body, comprising: (1) a step 1 of preparing a slurry containing yttrium aluminum garnet powder and a sintering aid, and curing it to produce a molded body; (2) a step 2 of firing the molded body; (3) a step 3 of subjecting the fired molded body to high temperature and high pressure in an inert atmosphere; and (4) a step 4 of oxygen annealing the molded body that has been subjected to high temperature and high pressure to produce a sintered body, wherein the sintering aid contains a silicon-containing compound and a group II element-containing compound, and the sintered body has a light loss coefficient of 0.002 cm when light with a wavelength of 300 to 2500 nm (excluding wavelengths where absorption occurs due to added elements) is transmitted through it. －１ A manufacturing method characterized by the following:

8. The silicon-containing compound is SiO ２ The manufacturing method according to claim 7, including 9. The manufacturing method according to claim 7, wherein the group II element-containing compound includes a magnesium-containing compound and / or a calcium-containing compound.

10. The manufacturing method according to claim 9, wherein the molar ratio ((Mg + Ca) / Si) of the total number of moles of magnesium and calcium in the sintering aid to the number of moles of silicon is 15 or less.

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