Chromium-containing yttrium aluminum garnet sintered body and method for manufacturing the same

Abstract

The present invention provides a Cr:YAG sintered body in which variations in light transmittance are suppressed. [Solution] A chromium-containing yttrium aluminum garnet sintered body characterized in that the variation value of the light transmittance measured by the measurement method described below is 5% or less. (Method for measuring the variation in light transmittance) (1) Select two or more locations on the same surface of the chromium-containing yttrium aluminum garnet sintered body. (2) For the selected area, the light transmittance is measured using a spectrophotometer with a yttrium aluminum garnet substrate as the base, under the conditions of measurement wavelengths of 1030 nm and 1064 nm. (3) Calculate the difference between the maximum and minimum values ​​of the measured light transmittance at the measurement site, and use this as the variation value of light transmittance.

Description

[Technical Field]

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

[0002] Conventionally, chromium-containing yttrium aluminum garnet (hereinafter also referred to as "Cr:YAG") sintered bodies have been used as laser oscillators. In particular, Cr 4+ Contains Cr 4+ YAG sintered bodies absorb laser light in the wavelength range around 1000 nm, and can absorb parasitic oscillations in directions other than the desired direction of laser oscillation. This results in high oscillation efficiency, enabling high-power, high-quality laser oscillation.

[0003] Cr 4+ YAG sintered bodies have the characteristic of accumulating a certain amount of absorbed light before emitting it, and by joining different dopants, pulsed laser oscillation becomes possible with small devices, so they are used in the fields of engine ignition and laser processing, such as Cr 4+ YAG sintered bodies are required to have uniform light transmission.

[0004] As a Cr:YAG sintered body, a Cr:YAG sintered body has been proposed in which the component content of each element satisfies a specific formula (see Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6823224 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, Patent Document 1 does not consider whether the light transmittance of the Cr:YAG sintered body is uniform, and the Cr:YAG sintered body described in Patent Document 1 has the problem that when the light transmittance is measured, there is variation depending on the measurement location. Such a Cr:YAG sintered body cannot emit uniform laser light and has the problem of not being able to exhibit stable performance when used in fields such as engine ignition and laser processing.

[0007] In view of the above circumstances, the present invention aims to provide a Cr:YAG sintered body in which variations in light transmittance are suppressed. Furthermore, the present invention aims to provide a manufacturing method that can produce a Cr:YAG sintered body in which variations in light transmittance are suppressed. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have discovered that the above objective can be achieved by a Cr:YAG sintered body characterized by a variation value of 5% or less in light transmittance measured by a specific measurement method, and have completed the present invention.

[0009] In other words, the present invention relates to the following Cr:YAG sintered body and method for producing the same. 1. A chromium-containing yttrium aluminum garnet sintered body characterized by having a variation value of 5% or less in light transmittance measured by the following measurement method. (Method for measuring the variation in light transmittance) (1) Select two or more locations on the same surface of the chromium-containing yttrium aluminum garnet sintered body. (2) For the selected area, the light transmittance is measured using a spectrophotometer with a yttrium aluminum garnet substrate as the base, under the conditions of measurement wavelengths of 1030 nm and 1064 nm. (3) Calculate the difference between the maximum and minimum values ​​of the measured light transmittance at the measurement site, and use this as the variation value of light transmittance. 2. The chromium-containing yttrium aluminum garnet sintered body according to item 1, wherein the variation value of the light transmittance is 3% or less. 3. The chromium-containing yttrium aluminum garnet sintered body according to item 1, wherein the variation value of the light transmittance is 2% or less. 4. The chromium-containing yttrium aluminum garnet sintered body according to item 1, wherein the variation value of the light transmittance is 1.5% or less. 5. A chromium-containing yttrium aluminum garnet sintered body according to item 1 or 2, wherein the chromium content is 1.5 at% or less. 6. A chromium-containing yttrium aluminum garnet sintered body according to any one of items 1 to 5, wherein the sintering aid contains an alkaline earth metal element derived from a sintering aid, the sintering aid comprising an oxide or carbonate of Ca or Mg. 7. The chromium-containing yttrium aluminum garnet sintered body according to item 6, wherein the average particle size of the sintering aid is less than 300 nm. 8. A method for producing a chromium-containing yttrium aluminum garnet sintered body, (I) Step 1: Prepare a molded body by curing a slurry containing chromium-containing yttrium aluminum garnet powder and a sintering aid in a mold and casting it. (II) Step 2 of firing the molded body, (III) Step 3 of subjecting the fired molded body to high temperature and high pressure in an inert atmosphere, (IV) The process includes step 4 of oxygen annealing the molded body that has been subjected to high temperature and high pressure treatment to produce a sintered body, The sintering aid comprises a compound containing a group II element, The manufacturing method is characterized in that the sintered body has a variation value of 5% or less of the light transmittance measured by the following measurement method. (Method for measuring the variation in light transmittance) (1) Select two or more locations on the same surface of the chromium-containing yttrium aluminum garnet sintered body. (2) For the selected area, the light transmittance is measured using a spectrophotometer with a yttrium aluminum garnet substrate as the base, under the conditions of measurement wavelengths of 1030 nm and 1064 nm. (3) Calculate the difference between the maximum value and the minimum value among the measured values of light transmittance at the measurement sites, and define this difference as the variation value of light transmittance. 9. The production method according to Item 8, wherein the variation value of the light transmittance is 3% or less. 10. The production method according to Item 8 or 9, wherein the variation value of the light transmittance is 2% or less. 11. The production method according to any one of Items 8 to 10, wherein the variation value of the light transmittance is 1.5% or less. 12. The production method according to any one of Items 8 to 11, wherein the sintering aid contains an oxide or a carbonate of Ca or Mg. 13. The production method according to any one of Items 8 to 12, wherein the average particle diameter of the sintering aid is less than 300 nm. Advantageous Effects of the Invention

[0010] In the Cr:YAG sintered body of the present invention, variation in light transmittance is suppressed. Further, the method for producing a Cr:YAG sintered body of the present invention can produce a Cr:YAG sintered body in which variation in light transmittance is suppressed. Mode for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. The description of constituent requirements set forth below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

[0012] In the numerical ranges described stepwise in the present specification, the upper limit or lower limit of a numerical range in one step can be arbitrarily combined with the upper limit or lower limit of a numerical range in another step. In addition, in the numerical ranges described in the present specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples or a value that can be uniquely derived from the examples. Furthermore, in the present specification, a numerical value connected by "~" means a numerical range that includes the numerical values before and after "~" as the lower limit and the upper limit.

[0013] In this specification, the expressions “contains” and “includes” include the concepts of “contains,” “includes,” “substantially consists of,” and “consistes of only.”

[0014] 1. Cr:YAG sintered body The Cr:YAG sintered body of the present invention has a variation value of 5% or less in light transmittance measured by the measurement method described later. The Cr:YAG sintered body of the present invention having the above characteristics has a variation value of 5% or less in light transmittance measured by the above specific measurement method, thus suppressing variations in light transmittance and enabling the emission of uniform laser light.

[0015] The Cr:YAG sintered body of the present invention will be described in detail below.

[0016] The variation in light transmittance of the Cr:YAG sintered body of the present invention is 5% or less. If the variation exceeds 5%, the variation in light transmittance is not suppressed, it is not possible to oscillate uniform laser light, and the oscillator cannot exhibit stable performance. The above variation is preferably 3% or less, more preferably 2% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. Furthermore, the lower limit of the above variation is better the lower it is, and may be 0%, 0.01%, or 0.03%.

[0017] In this invention, the variation value of the light transmittance of the Cr:YAG sintered body is measured by the following method.

[0018] (Method for measuring the variation in light transmittance) (1) Select two or more locations on the same surface of the Cr:YAG sintered body. (2) For the selected area, the light transmittance is measured using a spectrophotometer with the YAG substrate as the base, under the conditions of measurement wavelengths of 1030 nm and 1064 nm. The thickness of the YAG sintered body during measurement can be any thickness as described in the examples. (3) Calculate the difference between the maximum and minimum values ​​of the measured light transmittance at the measurement site, and use this as the variation value of light transmittance.

[0019] The thickness of the YAG substrate used as the base for the above light transmittance measurement is not limited as long as it does not interfere with the measurement, and may be 0.5 mm thick, 1 mm thick, 5 mm thick, or 10 mm thick. Typically, a 1 mm thick yttrium aluminum garnet substrate is sufficient.

[0020] In this invention, the variation value of light transmittance refers to the variation value for two wavelengths, 1030 nm and 1064 nm. However, in this invention, a variation value of 5% or less for light transmittance means that the variation value for both wavelengths is 5% or less.

[0021] In the Cr:YAG sintered body of the present invention, the lower limit of the light transmittance at a measurement wavelength of 1030 nm may be 0.1%, 1%, 2%, 3%, 5%, 10%, 20%, 30%, 40%, 50%, etc. Furthermore, the upper limit of the light transmittance at a measurement wavelength of 1030 nm is preferably higher, and may be 100%, 99.9%, 99.0%, 98%, 95%, 90%, etc.

[0022] In the Cr:YAG sintered body of the present invention, the lower limit of the light transmittance at a measurement wavelength of 1064 nm may be 0.1%, 1%, 2%, 3%, 5%, 10%, 20%, 30%, 40%, 50%, etc. Furthermore, the upper limit of the light transmittance at a measurement wavelength of 1064 nm is preferably higher, and may be 100%, 99.9%, 99.0%, 98%, 95%, 93%, etc.

[0023] The chromium content of the Cr:YAG sintered body of the present invention is preferably 1.5 at% or less, more preferably 0.5 at% or less, and even more preferably 0.25 at% or less. Furthermore, the chromium content of the Cr:YAG sintered body is preferably 0.005 at% or more, more preferably 0.01 at% or more, and even more preferably 0.03 at% or more. By setting the upper limit of the chromium content within the above range, the variation in light transmittance can be reduced. In addition, by setting the upper limit of the chromium content within the above range, the oscillation efficiency of the laser oscillator can be further improved.

[0024] The sintering aid containing alkaline earth metal elements is not particularly limited and includes oxides, hydroxides, carbonates, etc. Among these, carbonates are preferred from the viewpoint of reducing the variation in light transmittance.

[0025] The above-mentioned sintering aids can be used individually or in mixtures of two or more. In the Cr:YAG sintered body of the present invention, it is preferable that the above-mentioned sintering aids include oxides and / or carbonates of Ca and / or Mg.

[0026] The average particle size of the sintering aid is preferably less than 300 nm, and more preferably 150 nm or less. Furthermore, the average particle size of the sintering aid is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. By having the upper limit of the average particle size within the above range, the oscillation efficiency of the laser oscillator is further improved. Furthermore, by having the lower limit of the average particle size within the above range, the variation in light transmittance can be further reduced.

[0027] In this specification, the average particle size of the sintering aid is the average particle size measured by observation using a scanning electron microscope.

[0028] 2. Method for manufacturing a Cr:YAG sintered body The present invention provides a method for producing a Cr:YAG sintered body (chromium-containing yttrium aluminum garnet sintered body), (I) A slurry containing Cr:YAG powder and a sintering aid is cured in a mold and cast to prepare a molded body in step 1. (II) Step 2 of firing the molded body, (III) Step 3 of subjecting the fired molded body to high temperature and high pressure in an inert atmosphere, (IV) The process includes step 4 of oxygen annealing the molded body that has been subjected to high temperature and high pressure treatment to produce a sintered body, The sintering aid comprises a compound containing a group II element, The sintered body is characterized in that the variation value of the light transmittance measured by the above-described measurement method is 5% or less.

[0029] The manufacturing method of the present invention will be described in detail below, step by step.

[0030] (Process 1) Step 1 is a process of preparing a molded body by curing a slurry containing chromium-containing yttrium aluminum garnet (hereinafter also referred to as "Cr:YAG") powder and a sintering aid in a mold and then casting it.

[0031] 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.

[0032] The sintering aid used in step 1 contains a compound containing a group 2 element. The group 2 element exists as a divalent cation in the Cr:YAG sintered body. In Cr:YAG, Cr 4+ A high ratio of is desirable for the oscillation efficiency of the laser oscillator. Because the sintering aid used in step 1 contains a group 2 element-containing compound, in the Cr:YAG sintered body, 3+ From Cr 4+ Controlling the valence of Cr 4+ The ratio can be increased.

[0033] The average particle size of the sintering aid is preferably less than 300 nm, more preferably 250 nm or less, and even more preferably 150 nm or less. Furthermore, the average particle size of the sintering aid is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. By having the upper limit of the average particle size within the above range, the oscillation efficiency of the laser oscillator is further improved. Furthermore, by having the lower limit of the average particle size within the above range, the variation in light transmittance can be further reduced.

[0034] 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.

[0035] As Group II element-containing compounds, calcium-containing compounds and magnesium-containing compounds are preferred, with calcium-containing compounds being more preferred. Furthermore, Group II element-containing compounds include oxides, hydroxides, and carbonates of the above-mentioned Group II elements, and among these, oxides and carbonates can be suitably used. Specifically, Group II element-containing compounds include calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, and magnesium carbonate. Among these, calcium oxide, calcium carbonate, magnesium oxide, and magnesium carbonate are preferred, and from the viewpoint of reducing the variation in light transmittance, magnesium carbonate and calcium carbonate are more preferred.

[0036] The above-mentioned sintering aid can be used alone or in a mixture of two or more types. In the manufacturing method of the present invention, it is preferable that the above-mentioned sintering aid contains an oxide and / or carbonate of Ca and / or Mg. It is more preferable that the above-mentioned sintering aid contains an oxide and / or carbonate of either Ca or Mg. By having the above-mentioned configuration of the sintering aid, the variation in light transmittance can be reduced.

[0037] 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.

[0038] 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.

[0039] 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 Cr:YAG powder and the sintering aid, and any known alcohol can be used.

[0040] 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.

[0041] In step 1, a slurry containing the above-mentioned Cr:YAG powder and sintering aid is prepared, and the slurry is hardened in a mold and cast to produce a molded body. One method for hardening the slurry is to pour the slurry into a plaster mold and press it in under pressure of 400 to 600 kPa to form the molded body.

[0042] In step 1, the molded body formed as described above may be degreased. The method of degreasing is not particularly limited, and one example is heating at a temperature of 400 to 800°C.

[0043] In the process described above, step 1 involves curing a slurry containing Cr:YAG powder and a sintering aid in a mold, which is then cast and molded to prepare a molded body.

[0044] (Process 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.

[0045] 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.

[0046] 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.

[0047] In step 2, firing is preferably carried out under vacuum conditions. Vacuum firing further improves the transparency of the manufactured Cr:YAG sintered body, reduces the variation in light transmittance, and further improves the oscillation efficiency of the laser oscillator.

[0048] In step 2, firing may be carried out under a reducing atmosphere. When firing is performed under a reducing atmosphere, the Cr in the manufactured Cr:YAG sintered body becomes trivalent, and the sintered body is colored green.

[0049] In step 2, as described above, the molded body prepared in step 1 is fired.

[0050] (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. By performing Step 3, the variation in the light transmittance of the manufactured Cr:YAG sintered body can be reduced, thereby improving the oscillation efficiency of the laser oscillator element.

[0051] 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 are acceptable. Among these, an argon atmosphere is more preferable.

[0052] The processing temperature can be adjusted as appropriate; for example, 1350 to 1850°C is preferred.

[0053] The processing pressure can be adjusted as appropriate; for example, 50 to 200 MPa is preferred.

[0054] The processing time can be set appropriately according to the firing temperature, etc., and for example, 1 to 5 hours is preferred.

[0055] Through step 3 described above, the fired compact is subjected to high-temperature and high-pressure treatment in an inert atmosphere.

[0056] (Step 4) Step 4 is a step of producing a sintered body by subjecting the high-temperature and high-pressure treated compact to oxygen annealing treatment. The oxygen annealing treatment is a heat treatment performed in an oxygen-containing atmosphere, either under atmospheric air or under a constant pressure. By subjecting the compact to the oxygen annealing treatment, the valence of Cr in the produced sintered body can be adjusted to tetravalent, the variation value of light transmittance can be further reduced, and the oscillation efficiency of the laser oscillation element is further improved.

[0057] By performing the oxygen annealing treatment in step 4, the Cr:YAG sintered body can be made transparent in the HIP treatment of step 3 described above. That is, Y generated by performing HIP through step 3 above 2+ , by performing oxygen annealing treatment in step 4, Y 2+ oxygen ions that neutralize the charge are supplied to the Cr:YAG sintered body, allowing the Cr:YAG sintered body to exhibit high transparency, reducing the variation value of light transmittance, and improving the oscillation efficiency of the laser oscillation element. Furthermore, by performing the oxygen annealing treatment in step 4, Cr that became trivalent in the firing under reducing atmosphere of step 2 described above can be valence-controlled to tetravalent. That is, Cr generated by firing in a reducing atmosphere through step 2 above 3+ , by performing oxygen annealing treatment in step 4, the valence of Cr can be stably set to tetravalent, and the oscillation efficiency of the laser oscillation element is improved.

[0058] The oxygen annealing temperature may be adjusted as appropriate, and for example, 1000 to 1500°C is preferable.

[0059] The pressure during oxygen annealing may be adjusted as appropriate, and for example, atmospheric pressure to 200 MPa is preferable.

[0060] The oxygen annealing time can be adjusted as needed, allowing the Cr:YAG sintered body to be treated for any duration until the green color disappears.

[0061] As described above in step 4, the molded body that has been subjected to high temperature and high pressure treatment is subjected to oxygen annealing to produce a sintered body.

[0062] The Cr:YAG sintered body produced by the manufacturing method of the present invention has a light transmittance variation value of 5% or less, as measured by the measurement method described above for the Cr:YAG sintered body of the present invention. The details of the measurement method for the variation value of the Cr:YAG sintered body produced by the manufacturing method of the present invention, the range of the variation value, and other characteristics are the same as those of the Cr:YAG sintered body of the present invention described above. Such a Cr:YAG sintered body of the present invention can be usefully used as a laser oscillation element. The Cr: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. [Examples]

[0063] 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.

[0064] (Example 1) Preparation of raw material powder To adjust the Cr concentration of the YAG sintered body to the Cr concentrations listed in Tables 1 and 2 (0.005~0.25 at%), 15 L of 0.5 mol / L yttrium nitrate aqueous solution was mixed with 25 L of 0.5 mol / L aluminum nitrate aqueous solution to prepare a Cr:YAG mixed solution. Separately, 40 L of 2 mol / L ammonium bicarbonate aqueous solution, whose pH was adjusted to 8.2 with ammonia water, was prepared. The Cr:YAG mixed solution was added dropwise to the ammonium bicarbonate aqueous solution at a rate of 1.5 L / min to prepare a Cr:YAG dispersion. During this process, the temperature of both the Cr:YAG mixed solution and the ammonium bicarbonate aqueous solution was maintained at 32°C. The minimum pH during the dropwise addition was 7.0, and the pH reached a steady value of 7.95 approximately 3 hours after the completion of the addition. After the dropwise addition was complete, the Cr:YAG dispersion was cured at 32°C for 48 hours, and filtration and washing with water were repeated six times to reduce the anions, nitrate ions and free carbonate ions, which are impurities in the precipitate, to 2000 wt ppm or less. Next, the precipitate was washed with water to obtain the Cr:YAG precursor, which was dried in air at 120°C, then calcined in air at 1200°C for 5 hours, and pulverized to prepare a Cr:YAG powder with excellent dispersibility and a secondary particle size of 0.22 μm.

[0065] Preparation of molded bodies An organic additive containing a dispersant was dispersed in alcohol, and the raw material powder and sintering aid were added. The mixture was then mixed for approximately 20 hours using a nylon pot and nylon balls. The resulting slurry was degassed for approximately 30 minutes using a vacuum degasser, and then poured into a plaster mold using a pressure casting machine at approximately 490 kPa (approximately 5 kg / cm²). 2 Molded bodies measuring 78mm x 78mm x 5mm and 44mm x 44mm x 15.5mm were prepared by press-fitting with the specified pressure.

[0066] Firing of molded body (pre-sintering) The molded body prepared as described above was thoroughly dried at room temperature and degreased at 750°C for 100 hours at a heating rate of 30°C / hr in an oxygen stream. The density of the molded body after degreasing was 60.5% of the theoretical density. The molded body was then degreased at a heating rate of 400°C / hr and a vacuum of 10°C.-3 Under conditions below Torr, the Cr:YAG material was fired (pre-sintered) in a vacuum furnace at 1600°C for 2 hours to prepare a fired molded body (pre-sintered body). The density of the fired molded body (pre-sintered body), as measured by the Archimedes method as a ratio to the theoretical density, was 98.8%. When the cross-section of the fired molded body (pre-sintered body) was observed with a scanning electron microscope, the average particle size of the Cr:YAG molded body (pre-sintered) was found to be 0.7 mm.

[0067] HIP treatment The fired molded body (pre-sintered body) was subjected to HIP treatment. Specifically, a high-temperature and high-pressure treatment was performed in an Ar atmosphere under conditions of 147 MPa pressure, 1800°C temperature, and a treatment time of 5 hours to prepare a HIP-sintered body.

[0068] Annealing process A Cr:YAG sintered body was produced by annealing a HIP sintered body in a HIP furnace, after changing the atmosphere to an oxygen-containing atmosphere including Ar-O2. The annealing conditions were a pressure of 50 MPa, a temperature of 1200°C, and a processing time of 10 hours.

[0069] (Examples 2-26, Comparative Examples 1-3) The manufacturing conditions for Cr:YAG sintered bodies were adjusted to produce Cr:YAG sintered bodies with the properties shown in Tables 1 and 2.

[0070] (Evaluation method) The surfaces of the Cr:YAG sintered bodies of the examples and comparative examples were optically polished, and the variation in light transmittance was measured by the following method.

[0071] Light transmittance and variation values A U-4100 spectrophotometer (manufactured by Hitachi High-Tech Corporation) was used to measure light transmittance, and the light transmittance and variability values ​​were measured according to (1) to (5) below. (1) A baseline was drawn with nothing between the light source and the detector, and the light transmittance was adjusted to 100%. (2) When a 1 mm thick YAG substrate was placed between the light source and the detector and the light transmittance was measured, it was 84%. This is due to the attenuation of light transmittance by surface reflection of the YAG substrate. (3) In this state, the baseline was drawn again and the light transmittance was adjusted to 100%. (4) The YAG substrate was replaced with a Cr:YAG sintered body, and the light transmittance was measured for 60 seconds at five locations on the same surface of the Cr:YAG sintered body at measurement wavelengths of 1030 nm and 1064 nm. The thickness of the Cr:YAG sintered body was 1 mm or 10 mm. (5) The difference between the maximum and minimum measured values ​​of light transmittance was calculated for each of the measurement wavelengths of 1030 nm and 1064 nm, and this was used as the variation value of light transmittance.

[0072] Based on the variability values ​​measured using the above measurement method, the following evaluation criteria were used. A rating of A to D indicates that there are no problems in actual use. A: The variability is 1.5% or less. B: The variability value is greater than 1.5% and less than or equal to 2%. C: The variation value is greater than 2% but less than or equal to 3%. D: The variability value is greater than 3% and less than or equal to 5%. E: The variability value is greater than 5%.

[0073] The results are shown in Tables 1 and 2. Table 1 shows the measurement results at a wavelength of 1030 nm, and Table 2 shows the measurement results at a wavelength of 1064 nm.

[0074] [Table 1]

[0075] [Table 2]

[0076] From the results in Tables 1 and 2, MgCO₃ is found to be an alkaline earth metal element. 3、It was found that using CaCO3 further suppresses variations in light transmittance within the Cr:YAG sintered body. Therefore, MgCO3 is used as an alkaline earth metal element. 3、 It was found that using CaCO3 further suppresses variations in the alkaline earth metal element content within the Cr:YAG sintered body.

Claims

1. A chromium-containing yttrium aluminum garnet (YAG) sintered body characterized by having a variation value of 5% or less in light transmittance measured by the measurement method described below. (Method for measuring variations in light transmittance) (1) Select two or more locations on the same surface of the chromium-containing yttrium aluminum garnet sintered body. (2) For the selected area, the light transmittance is measured using a spectrophotometer with a yttrium aluminum garnet substrate as the base, under the conditions of measurement wavelengths of 1030 nm and 1064 nm. (3) Calculate the difference between the maximum and minimum values ​​of the measured light transmittance at the measurement site, and use this as the variation value of light transmittance.

2. The chromium-containing yttrium aluminum garnet sintered body according to claim 1, wherein the variation value of the light transmittance is 3% or less.

3. The chromium-containing yttrium aluminum garnet sintered body according to claim 1, wherein the variation value of the light transmittance is 2% or less.

4. The chromium-containing yttrium aluminum garnet sintered body according to claim 1, wherein the variation value of the light transmittance is 1.5% or less.

5. The chromium-containing yttrium aluminum garnet sintered body according to claim 1, wherein the chromium content is 1.5 at% or less.

6. A chromium-containing yttrium aluminum garnet sintered body according to claim 1, comprising an alkaline earth metal element derived from a sintering aid, wherein the sintering aid comprises an oxide and / or carbonate of Ca and / or Mg.

7. The chromium-containing yttrium aluminum garnet sintered body according to claim 6, wherein the average particle size of the sintering aid is less than 300 nm.

8. A method for producing a chromium-containing yttrium aluminum garnet sintered body, (I) Step 1: Prepare a molded body by curing a slurry containing chromium-containing yttrium aluminum garnet powder and a sintering aid in a mold and casting it. (II) Step 2 of firing the molded body, (III) Step 3, in which the fired molded body is subjected to high temperature and high pressure in an inert atmosphere, (IV) The process includes step 4 of oxygen annealing the molded body that has been subjected to high temperature and high pressure treatment to produce a sintered body, The sintering aid comprises a compound containing a group II element, The manufacturing method is characterized in that the sintered body has a variation value of 5% or less of the light transmittance measured by the measurement method described below. (Method for measuring variations in light transmittance) (1) Select two or more locations on the same surface of the chromium-containing yttrium aluminum garnet sintered body. (2) For the selected area, the light transmittance is measured using a spectrophotometer with a yttrium aluminum garnet substrate as the base, under the conditions of measurement wavelengths of 1030 nm and 1064 nm. (3) Calculate the difference between the maximum and minimum values ​​of the measured light transmittance at the measurement site, and use this as the variation value of light transmittance.

9. The manufacturing method according to claim 8, wherein the variation value of the light transmittance is 3% or less.

10. The manufacturing method according to claim 8, wherein the variation value of the light transmittance is 2% or less.

11. The manufacturing method according to claim 8, wherein the variation value of the light transmittance is 1.5% or less.

12. The manufacturing method according to claim 8, wherein the sintering aid comprises an oxide and / or carbonate of Ca and / or Mg.

13. The manufacturing method according to claim 8, wherein the average particle size of the sintering aid is less than 300 nm.

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