TW202222736A - Paramagnetic garnet-type transparent ceramic, magneto-optical device, and production method for paramagnetic garnet-type transparent ceramic - Google Patents

Abstract

A paramagnetic garnet-type transparent ceramic that exhibits little scattering and produces transmitted light that has a high laser beam quality, said ceramic being a sintered body of a Tb-containing rare earth-aluminum garnet represented by formula (1): (Tb1-x-yYxScy)3(Al1-zScz)5O12 (In the formula, 0 ≤ x < 0.45, 0 ≤ y < 0.08, 0 ≤ z < 0.2, and 0.001 < y+z < 0.20), and being characterized in that the value of the coefficient b obtained by fitting the diffused transmission factor Td in the wavelength range of 550 nm ≤ [lambda] ≤ 1,350 nm as measured using a sample having a length of 20 mm to formula (2) by means of a least squares method is 5.0 * 105 or less. Formula (2): TFit=a[lambda]-4+b[lambda]-2+c (in the formula, a, b, and c are real numbers.).

Description

Paramagnetic garnet-type transparent ceramics, magnetic optical device, and manufacturing method of paramagnetic garnet-type transparent ceramics

The present invention relates to paramagnetic garnet-type transparent ceramics having translucency in visible light and/or near-infrared regions, and more specifically, to a tungsten-containing ( The paramagnetic garnet-type transparent ceramic of Tb) uses the magnetic optical device of the paramagnetic garnet-type transparent ceramic and the manufacturing method of the paramagnetic garnet-type transparent ceramic.

For the purpose of preventing the reverse return of light such as reflected light, industrial laser processing machines are provided with optical unidirectional devices, and inside the optical unidirectional device is mounted a glass or tungsten gallium garnet (TGG) crystal added with titanium (Tb) as a Faraday rotator ( For example, Japanese Patent Laid-Open No. 2011-213552 (Patent Document 1)). The magnitude of the Faraday effect is quantified by the Verdet constant. The Verdet constant of TGG crystal is 40rad/(T･m)(=0.13min/(Oe･cm)), and that of glass added with T is 0.098min/(Oe ･cm), the Verde constant of TGG crystal is relatively large, so it is widely used as a standard Faraday rotor. In addition, there is also titanium aluminum garnet (TAG) crystal. The Verde constant of TAG crystal is about 1.3 times that of TGG crystal, so the length of Faraday rotator can be shortened, and it can be used for fiber laser and is a good crystal (for example , Japanese Patent Laid-Open No. 2002-293693 (Patent Document 2), Japanese Patent No. 4107292 (Patent Document 3)).

In recent years, a method of producing TAG from transparent ceramics has been disclosed (for example, International Publication No. 2017/033618 (Patent Document 4), “High Verdet constant of Ti-doped terbium aluminum garnet (TAG) ceramics” (Non-Patent Document 1) )). In addition, the production method of the transparent ceramic of YTAG(Tb _x Y _1-x ) ₃ Al ₅ O ₁₂ (0.2≦x≦0.8, or 0.5≦x≦1.0 or x=0.6) in which a part of the tungsten was replaced with yttrium was also discussed. Reports (for example, "Fabrication and properties of (Tb _x Y _1-x ) ₃ Al ₅ O ₁₂ transparent ceramics by hot isostatic pressing" (Non-Patent Document 2), "Development of optical grade (Tb _x Y _1-x ) ₃ Al ₅ O ₁₂ ceramics as Faraday rotator material” (Non-Patent Document 3), “Effect of (Tb+Y)/Al ratio on Microstructure Evolution and Densification Process of (Tb _0.6 Y _0.4 ) ₃ Al ₅ O ₁₂ Transparent Ceramics” ( Non-patent document 4)). The rare earth aluminum garnet containing Tb exhibits higher thermal conductivity than TGG, and is expected to be a Faraday element with a small thermal lens effect.

In addition, the so-called thermal lens effect is a phenomenon in which the Faraday element absorbs the transmitted light, generates heat, and changes the refractive index and becomes a lens shape. When the focal position of the laser processing machine is moved due to the thermal lens effect, it is not preferable because it becomes an out-of-focus light beam at the processing point and reduces the processing accuracy.

As mentioned above, there have been many reports of rare earth aluminum garnet containing Tb by ceramic manufacturers in recent years. This is because TAG has an incongruent (incongruent, incongruent melting) composition, making it difficult to produce a single crystal. However, general ceramics contain many scattering sources such as air bubbles, different phases, foreign matter, and microcracks in the system. Therefore, in order to obtain the highly transparent ceramics envisaged by the Faraday rotator, it is necessary to try to completely eliminate scattering sources such as air bubbles and foreign matter.

The scattering caused by bubbles inside the ceramic can be well explained by Mie scattering theory. For example, for a certain wavelength λ, there are bubbles of radius r inside the ceramic. In the case of r<<λ, Rayleigh scattering is exhibited, and the scattering intensity ratio becomes stronger than λ ^-4 . In addition, in the case of r>>λ, Mie scattering is exhibited, and the scattering intensity thereof has a constant value with respect to the wavelength.

In addition, Apetz et al. report a scattering model for hexagonal transparent alumina ceramics. Transparent ceramics having birefringence exhibit Rayleigh-Gans-Debye scattering, and the scattering intensity becomes stronger in proportion to λ ^-2 ("Transparent Alumina: A Light-Scattering Model" (Non-Patent Document 5)).

As a method of reducing the bubbles and heterophases in the ceramic, there is a method of discharging out of the system by re-sintering after hot isotropic pressing (HIP) treatment by grain growth. "Microstructure and Optical Properties of Hot Isostatic Pressed Nd:YAG Ceramics" (Non-Patent Document 6) discloses transparent ceramics in which YAG ceramics were pre-fired at 1,600°C for 3 hours under vacuum, and then HIPed at 1,500 to 1,700°C for 3 hours , a method of re-sintering for 20 hours at 1,750°C higher than the HIP treatment temperature. In addition, in Japanese Patent No. 2638669 (Patent Document 5), it is disclosed to form a green compact having an appropriate shape and composition, to perform the preliminary sintering step at a temperature range of 1,350 to 1,650°C, and to make the HIP treatment step in the A method of producing a ceramic body by performing a temperature of 1,350~1,700°C, and then performing a re-sintering step at a temperature exceeding 1,650°C, thereby removing pores.

However, industrial laser processing machines require high beam quality in order to improve the processing accuracy. An example of an index of the laser beam quality is the M ² value. The value of M ² is a value representing the condensing property of the beam. The theoretical Gaussian beam is M ² =1, but the actual laser beam is M ² >1. When M ² =1, the beam can get the smallest spot at the focal point, and as the value of M ² increases, the beam cannot be focused at the focal point. Therefore, in the optical unidirectional device, it is preferable that the value of the beam quality M ² of the transmitted light is not increased as much as possible relative to the value of the beam quality M ² of the incident light. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-213552 [Patent Document 2] Japanese Patent Laid-Open No. 2002-293693 [Patent Document 3] Japanese Patent No. 4107292 [Patent Document 4] International Publication No. 2017/033618 [Patent Document 5] Japanese Patent No. 2638669 [Non-patent literature]

[Non-Patent Document 1] "High Verdet constant of Ti-doped terbium aluminum garnet (TAG) ceramics", Optical Materials Express, Vol.6, No. 1, pp.191-196 (2016) [Non-Patent Document 2] " Fabrication and properties of (Tb _x Y _1-x ) ₃ Al ₅ O ₁₂ transparent ceramics by hot isostatic pressing”, Optical Materials, 72, 58-62 (2017) [Non-Patent Document 3] “Development of optical grade (Tb _x Y _1-x ) ₃ Al ₅ O ₁₂ ceramics as Faraday rotator material”, Journal of American Ceramics Society, 100, 4081-4087 (2017) [Non-Patent Document 4] “Effect of (Tb+Y)/Al ratio on Microstructure Evolution and Densification Process of (Tb _0.6 Y _0.4 ) ₃ Al ₅ O ₁₂ Transparent Ceramics”, Materials, 12, 300 (2019) [Non-Patent Document 5] “Transparent Alumina: A Light-Scattering Model”, Journal of American Ceramics Society , 86, 480-486 (2003) [Non-Patent Document 6] "Microstructure and Optical Properties of Hot Isostatic Pressed Nd:YAG Ceramics", Journal of American Ceramics Society, 79, 1927-1933 (1996) [Non-Patent Document 7] “Lineal Intercept Technique for Measuring Grain Size in Two-Phase Polycrystalline Ceramics”, Journ al of the American Ceramic Society, 55, 109 (1972)

[The problem to be solved by the invention]

The present invention has been made in view of the foregoing circumstances, and an object of the present invention is to provide a transparent sintered body of a paramagnetic garnet-type oxide containing Tb and Al, and a paramagnetic paramagnetic material capable of obtaining transmitted light with less scattering and high laser beam quality Garnet-type transparent ceramics, a magnetic optical device using the paramagnetic garnet-type transparent ceramics, and a manufacturing method of the paramagnetic garnet-type transparent ceramics. [Means for solving problems]

As described above, along with the miniaturization of processing by pulse laser processing machines, higher beam quality of laser light is required. However, when the inventors of the present application evaluated the beam quality of an optical unidirectional device as a Faraday rotator mounted on a Tb-containing aluminum garnet that had been preliminarily sintered and subjected to only HIP treatment, as described in the prior art document, the incident occurred in the transmitted beam relative to the incident beam. The beam quality of the beam is significantly degraded. As a result of examining the aforementioned problems, the inventors of the present application have come to the conclusion that the scattering of ceramics degrades the beam quality. That is, the inventors of the present application measured the wavelength dependence of the diffuse transmittance of transparent ceramics, analyzed it with a unique formula, and found that a scattering intensity below a certain value can obtain transmitted light maintaining high beam quality. In particular, among the wavelength dependence of diffuse transmittance, it is effective for beam quality to reduce a component that is inversely proportional to the square of the wavelength. The inventors of the present application and others have completed the present invention by earnestly examining based on this knowledge.

That is, the present invention provides the following paramagnetic garnet-type transparent ceramics, magnetic optical devices, and methods of manufacturing the paramagnetic garnet-type transparent ceramics. 1. A paramagnetic garnet-type transparent ceramic, which is a sintered body of Tb-containing rare earth aluminum garnet represented by the following formula (1), and has a diffuse transmittance in the wavelength range of 550nm≦λ≦1,350nm measured for a sample with a length of 20mm T _d The value of the coefficient b obtained by fitting the following formula (2) by the least squares method is 5.0×10 ⁵ or less; (Tb _1-xy Y _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1) (where, 0≦x＜0.45, 0≦y＜0.08, 0≦z＜0.2, 0.001＜y+z＜0.20); T _Fit =aλ ^-4 +bλ ^-2 +c (2 ) (where a, b, and c are real numbers). 2. The paramagnetic garnet-type transparent ceramic according to 1, the diffuse transmittance T _d in the wavelength range of 550nm≦λ≦1,350nm measured for the sample with a length of 20mm is fitted by the least square method according to the above formula (2). The value of the coefficient c obtained by (fitting) is 1.0 or less. 3. The paramagnetic garnet-type transparent ceramic according to 1 or 2, wherein the average sintered particle size D is 7 μm or more and 50 μm or less. 4. For paramagnetic garnet-type transparent ceramics in any one of 1~3, when the sample is 20mm in length, the laser intensity is 100W, and the beam quality ^M2 value is m (1<m≦1.2) and the wavelength is 1,070 When the laser light of nm is incident and the beam quality M ² value of the transmitted light is n, n/m is 1.05 or less. 5. Paramagnetic garnet-type transparent ceramics according to any one of 1 to 4, further containing a sintering aid. 6. A magnetic optical device, which is composed of paramagnetic garnet-type transparent ceramics according to any one of 1 to 5. 7. The magneto-optical device according to 6, comprising using the paramagnetic garnet-type transparent ceramic as a Faraday rotator, and having a polarizing material before and after the optical axis of the Faraday rotator, which can be used in a wavelength band of 0.9 μm or more and 1.1 μm or less. light unidirectional. 8. A method for producing paramagnetic garnet-type transparent ceramics, which is a method for producing paramagnetic garnet-type transparent ceramics of any one of 1 to 5, for the sintering of the Tb-containing rare earth aluminum garnet represented by the following formula (1). The pressure sintered body is subjected to pressure sintering, and the pressure sintered body is further heated to a temperature exceeding the aforementioned pressure sintering temperature for re-sintering, and the re-sintered body is further subjected to an oxidation annealing treatment in an oxidizing atmosphere of 1,200°C or higher, (Tb _1-xy Y _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1) (wherein, 0≦x<0.45, 0≦y<0.08, 0≦z<0.2, and 0.001<y+z<0.20). 9. The method for producing a paramagnetic garnet-type transparent ceramic according to 8, wherein the sintered body before pressure sintering is densified to a relative density of 94% or more by preliminary sintering. 10. The method for producing a paramagnetic garnet-type transparent ceramic according to 9, wherein the preliminary sintering is performed under a reduced pressure of less than 1.0×10 ⁻³ Pa. [Effect of invention]

According to the present invention, a paramagnetic garnet-type transparent ceramic capable of maintaining high transmitted beam quality with low scattering can be provided, which is suitable as a material for forming magnetic optical devices such as optical unidirectional devices.

[Paramagnetic garnet type transparent ceramic]

Hereinafter, the paramagnetic garnet-type transparent ceramic of the present invention will be described. The paramagnetic garnet-type transparent ceramic according to the present invention is a sintered body of Tb-containing rare earth aluminum garnet represented by the following formula (1), and the diffusion in the wavelength range of 550nm≦λ≦1,350nm measured on a sample with a length of 20mm Transmittance T _d The value of coefficient b obtained by fitting the following formula (2) by the least square method is 5.0×10 ⁵ or less; (Tb _{1-xy Y x} Scy ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1) (where, 0≦x＜0.45, 0≦y＜0.08, 0≦z＜0.2, 0.001＜y+z＜0.20); T _Fit =aλ ^-4 +bλ ^-2 + c (2) (where a, b, and c are real numbers).

In addition, in the garnet crystal structure represented by the formula (1), the position mainly occupied by Tb, that is, the parenthesis in the first half of formula (1), is called the A position, and the position mainly occupied by Al, that is, the formula ( 1) The parentheses in the latter half are called B positions.

In the A position of the formula (1), Tb (Tb) is an element with the largest Verde constant among trivalent rare earth ions, and its absorption is extremely small in the 1,070 nm region (wavelength band of 0.9 μm to 1.1 μm) used for fiber lasers. , so the material for the optical unidirectional device used in this wavelength region is the most suitable element. However, Tb(III) ions are easily oxidized to generate Tb(IV) ions. If Tb(IV) ions are generated in metal oxides, light is absorbed in a wide range of wavelengths in the ultraviolet to near-infrared region, and the transmittance is reduced, so it is best to exclude it as much as possible. As one strategy for not generating Tb(IV) ions, it is effective to employ a crystal structure in which Tb(IV) ions are unstable, that is, to employ a garnet structure.

The ion radius of yttrium (Y) is about 2% smaller than that of yttrium, and when combined with aluminum to form a composite oxide, it is more stable to form a garnet phase than a perovskite phase, so it is an element that can be preferably used in the present invention.

In the B position of the formula (1), aluminum (Al) is a material with the smallest ionic radius among trivalent ions that can stably exist in oxides having a garnet structure, and can oxidize Tb-containing paramagnetic garnet types. The lattice constant of the substance becomes the smallest element. If the lattice constant of the garnet structure can be reduced without changing the Tb content, the Verde per unit length can be increased, so it is preferable. Furthermore, since aluminum is a light metal, its diamagnetism is weaker than that of gallium, and the effect of relatively increasing the magnetic flux density generated inside the Faraday rotator is expected. This can also increase the Verdet constant per unit length, so it is preferable. In fact, the Verde constant of TAG ceramics is increased to 1.25~1.5 times that of TGG. Therefore, even when the relative concentration of antium is reduced by converting a part of the ionium ions to yttrium ions, the Verdet constant per unit length can be made the same as or slightly lower than that of TGG, which is suitable for the present invention. constituent elements.

Here, when the composite oxide whose constituent elements are only Tb, Y, and Al may not have a garnet structure due to a subtle weighing error, it is difficult to stably manufacture a transparent ceramic that can be used in optical applications. Here, in the present invention, by adding scandium (Sc) as a constituent element, the composition deviation caused by the subtle weighing error is eliminated. In oxides with garnet structure, scandium is a material with an intermediate ionic radius that can be solid-dissolved at both the A position and the B position. The mixing ratio of rare earth elements composed of Tb and Y to Al is weighed. When the weight is discrete and deviates from the stoichiometric ratio, it is possible to adjust the distribution to the A position (where Tb and Y) in a way that just matches the stoichiometric ratio, and thereby minimizes the generation energy of sub-grains. A buffer material that is solid-dissolved according to the distribution ratio of the rare earth site) to the B site (aluminum site). In addition, the existence ratio of the alumina heterophase garnet mother phase can be limited to 1 ppm or less, and the existence ratio of the perovskite type heterophase garnet mother phase can be limited to 1 ppm or less, in order to improve the productivity of products. and elements that can be added.

In formula (1), the range of x is 0≦x<0.45, more preferably 0.05≦x<0.45, more preferably 0.10≦x≦0.40, and even more preferably 0.20≦x≦0.40. When x is within this range, the Verde constant at a wavelength of 1,064 nm at room temperature (23±15°C) becomes 30 rad/(T･m) or more, and it can be used as a Faraday rotator. In addition, this range is preferable because the thermal lens effect tends to become smaller as x becomes larger. Furthermore, within this range, the diffusion transmittance tends to decrease as x becomes larger, so it is preferable. The same applies to laser light having a wavelength of 1,070 nm. On the other hand, when x is 0.45, the Verde constant at a wavelength of 1,064 nm is less than 30 rad/(T･m), which is not good. That is, if the relative concentration of Tb is too thin, the total length of the Faraday rotator required to rotate the laser light with a wavelength of 1,064 nm (or a wavelength of 1,070 nm) by 45 degrees exceeds 30 mm when a general magnet is used, making it difficult to manufacture. good.

In formula (1), the range of y is 0≦y<0.08, preferably 0<y<0.08, more preferably 0.002≦y≦0.07, and even more preferably 0.003≦y≦0.06. When y is within this range, it can be reduced to such an extent that a perovskite-type heterophase cannot be detected by X-ray diffraction (XRD) analysis. Furthermore, the presence of a perovskite-type heterophase (typically 1 μm to 1.5 μm in diameter, colored and visible in a light brown color) in a field of view of 150 μm×150 μm with an optical microscope was found to be one. The following is preferable. At this time, the presence ratio of the perovskite-type heterophase to the garnet parent phase is 1 ppm or less.

When y is 0.08 or more, in addition to substituting a part of Tb with Y, a part of Tb is also substituted by Sc. As a result, the solid solution concentration of Tb is unnecessarily lowered, and therefore the Verde constant becomes small, which is not preferable. In addition, since the raw material of Sc is expensive, doping Sc unnecessarily excessively increases the manufacturing cost, which is not preferable. In addition, when y is 0.08 or more, Tb and Y enter the B site, and the risk of anti-site defect absorption in which Al enters the A site increases, which is not preferable.

In formula (1), the range of z is 0≦z<0.2, more preferably 0<z<0.16, more preferably 0.01≦z≦0.15, and even more preferably 0.03≦z≦0.15. When z is in this range, no perovskite heterophase is detected by XRD analysis. Furthermore, the presence of a perovskite-type heterophase (typically 1 to 1.5 μm in diameter, colored and visible in a light brown color) in a field of view of 150 μm×150 μm with an optical microscope was found to be one. The following is preferable. At this time, the presence ratio of the perovskite-type heterophase to the garnet parent phase is 1 ppm or less.

When z is 0.2 or more, the effect of suppressing the precipitation of the perovskite-type heterophase is saturated and does not change, and the value of y, that is, the substitution ratio of Tb by Sc, increases in conjunction with the increase in the value of z, and as a result, the value of Tb increases. The solid solution concentration of is unnecessarily reduced, so the Verdet constant becomes small and unfavorable. Furthermore, since the raw material of Sc is expensive, doping Sc excessively unnecessarily increases the manufacturing cost, which is not preferable. In addition, when z is 0.16 or more, Tb and Y enter the B site, and there is a high risk of occurrence of anti-defect absorption in which Al enters the A site, which is not preferable.

In the formula (1), the range of y+z is 0.001<y+z<0.20. If y+z is in this range, no perovskite heterophase can be detected by XRD analysis. Furthermore, the presence of a perovskite-type heterophase (typically 1 to 1.5 μm in diameter, colored and visible in a light brown color) in a field of view of 150 μm×150 μm with an optical microscope was found to be one. The following is preferable. At this time, the presence ratio of the perovskite-type heterophase to the garnet parent phase is 1 ppm or less. In addition, even if the range of y+z is in the range of 0≦y+z≦0.001, the effect of the present invention can be obtained, but due to the weighing error of the raw material, different phases are likely to occur, resulting in a decrease in productivity, which is not good.

In addition, in the paramagnetic garnet-type transparent ceramic of the present invention, it is more preferable that the sintered body further contains a sintering aid. Specifically, it is preferable that the sintering aid contains more than 0 mass % and 0.1 mass % or less (more than 0 ppm and 1,000 ppm or less) of SiO ₂ . If the content exceeds 0.1 mass % (1,000 ppm), there is a possibility that a small amount of light absorption may occur due to crystal defects caused by excessive Si content. The produced paramagnetic garnet-type transparent ceramic with a length (optical path length) of 20 mm is irradiated with a wavelength of 1,070 nm. When the 100W laser light is used, the thermal lens effect occurs. When the value of the beam quality ^M2 of the incident light is m, and the value of the beam quality ^M2 of the laser light passing through the transparent ceramic is n, n/m becomes higher than 1.05. Big so not good.

In addition, an oxide of magnesium (Mg) or calcium (Ca) may be further added as a sintering aid. Both Mg and Ca are divalent ions, and since they are elements that can compensate for deviations in the charge balance inside the garnet structure accompanying the addition of tetravalent SiO ₂ , they can be appropriately added. The addition amount is preferably adjusted according to the addition amount of SiO ₂ .

In addition, the paramagnetic garnet-type transparent ceramic of the present invention has little light scattering of transmitted light, and the diffuse transmittance T _d in the wavelength range of 550nm≦λ≦1,350nm measured for a sample with a length of 20mm is defined as follows. That is, the diffuse transmittance T _d in the wavelength range of 550 nm≦λ≦1,350 nm measured for a sample with a length of 20 mm is obtained by comparing the following formula (2) T _Fit =aλ ⁻⁴ +bλ ⁻² +c (2) (formula where a, b, and c are real numbers). The value of the coefficient b(%･nm ² ) obtained by fitting by the least squares method is 5.0×10 ⁵ or less, preferably 3.0×10 ⁵ or less, and more preferably 1.0×10 ⁵ or less. If the coefficient b is larger than 5.0×10 ⁵ , the Rayleigh-Gans-Debye scattering loss component of ceramics with a wavelength of 1,064 nm is larger than 0.02 dB, and when it is mounted on a laser processing machine as a Faraday rotator, the beam cannot be focused at the focal point without Suitable.

In addition, the diffuse transmittance T _d in the wavelength range of 550 nm≦λ≦1,350 nm measured for the sample with a length of 20 mm is obtained by fitting the coefficient c (%) obtained by the least square method according to the above formula (2). The value is preferably 1.0 or less, more preferably 0.8 or less, and still more preferably 0.5 or less. If the coefficient c is larger than 1.0, the Mie scattering loss component of ceramics with a wavelength of 1,064 nm is larger than 0.04 dB, and when it is mounted on a laser processing machine as a Faraday rotator, the beam may not be focused at the focal point.

In this case, the smaller the coefficient a, the better, but in the near-infrared region (eg, from 0.9 μm to 1.1 μm), the coefficient a is not limited in the present invention because aλ ^-4 <<bλ ^-2 +c. In addition, the aforementioned a, b, and c are numerical values determined by calculation, and may be negative values.

The diffuse transmittance T _d is the transmittance of diffused light excluding parallel components in the transmitted light (total light) when the test piece is irradiated with light, and is measured with reference to Japanese Industrial Standard JIS K 7136 (ISO 14782:1999). In addition, the aforementioned formula (2) is about the diffuse transmittance of Rayleigh scattering (scattering intensity depends on λ ^-4 ), Rayleigh-Gans-Debye scattering (scattering intensity depends on λ ^-2 ) and Mie scattering (scattering intensity does not depend on λ -2 ) Scattering model with linear combination of wavelength).

In addition, in the paramagnetic garnet-type transparent ceramic of the present invention, the average sintered particle size is preferably 7 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less, and even more preferably 20 μm or more and 40 μm or less. When the average sintered particle size is less than 7 μm, the amount of scattering inside the ceramic increases, and as a result, when a cylindrical shape with a length of 20 mm is used as a Faraday rotator mounted in a laser processing machine, the laser intensity is 100 W, and the beam quality M ² value is used for this. When a laser beam with a wavelength of 1,070 nm with m (1<m≦1.2) is incident, and the value of the beam quality M ² of the transmitted light is n, n/m exceeds 1.05.

In addition, the average particle size (average sintered particle size) of the sintered particles of the paramagnetic garnet-type transparent ceramic (re-sintered body) is obtained by measuring the particle size of the sintered particles of the target sintered body with a metal microscope, and the details are as follows way to obtain. That is, in the transmission mode using a metal microscope for the re-sintered body, a 50-times objective lens is used to image the transmitted open polarizing plate image of the sintered body sample whose both end surfaces are polished. In detail, photograph the optically effective area of a specific depth of the sintered body of the object, draw a diagonal line on the photographed image, calculate the total number of sintered particles crossed by the diagonal line, and divide the total number calculated by the length of the diagonal line The value of is defined as the average sintered particle size of the sintered particles in the image. Furthermore, the average particle diameter of each photographed image read by the analysis process was totaled, and the value divided by the number of photographed images was used as the average sintered particle diameter of the target sintered body (hereinafter, in the manufacturing method and examples of paramagnetic garnet-type transparent ceramics: same).

In addition, when the paramagnetic garnet-type transparent ceramic of the present invention is a sample with a length of 20 mm, a laser beam with a laser intensity of 100 W and a beam quality M ² value of m (1<m≦1.2) with a wavelength of 1,070 nm is used for this. Incidentally, when the value of the beam quality M ² of the transmitted light is n, n/m is preferably 1.05 or less, more preferably 1.04 or less, and even more preferably 1.03 or less. Thereby, when the laser light is transmitted, a high beam quality M ² can be obtained.

[Manufacturing method of paramagnetic garnet-type transparent ceramics] The manufacturing method of paramagnetic garnet-type transparent ceramics related to the present invention is the above-mentioned manufacturing method of paramagnetic garnet-type transparent ceramics described in the present invention, and the following formula (1 ) (Tb _1-xy Y _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1) (where, 0≦x＜0.45, 0≦y＜0.08, 0≦z＜0.2, 0.001＜ The sintered body containing Tb rare earth aluminum garnet represented by y+z<0.20) was subjected to pressure sintering, and the pressure sintered body was further heated to a temperature exceeding the aforementioned pressure sintering temperature to be re-sintered, and the re-sintered body was further heated at 1,200 The oxidation annealing treatment is carried out in an oxidizing atmosphere above ℃.

Here, paramagnetic garnet-type transparent ceramics were produced in the following procedure. (raw material powder for sintering) First, a raw material powder for sintering having a composition corresponding to the garnet-type composite oxide of the aforementioned formula (1) is produced.

The method for producing the raw material powder for sintering the garnet-type composite oxide used in the present invention is not particularly limited, and the metal oxide powder corresponding to each component element of the garnet-type composite oxide may be used as a starting material. A specific amount is weighed so as to have a composition corresponding to the formula (1), respectively, and mixed to obtain a raw material powder for sintering. The starting material in this case is not particularly limited as long as it can be made transparent, but from the viewpoint of suppressing absorption from impurities, the purity is preferably 99.9 mass % or more, more preferably 99.99 mass % or more, and most preferably 99.999 mass % or more. In addition, the particle diameter of the primary particles of the raw material powder is not particularly limited as long as it can be made transparent, but it is preferably 50 nm or more and 1,000 nm or less from the viewpoint of sinterability. The shape of the primary particle is selected from a card-house shape, a spherical shape, and a rod shape, and is not particularly limited as long as it can be made transparent.

Alternatively, as the method for producing the raw material powder for sintering the garnet-type composite oxide used in the present invention, a co-precipitation method, a pulverization method, a spray thermal decomposition method, a sol-gel method, or an alkoxide method may be used. Hydrolysis method, complex polymerization method, uniform precipitation method, and various other synthesis methods. Depending on the situation, the obtained ceramic raw material of the rare earth composite oxide may be appropriately processed into a desired particle size by a wet ball mill, bead mill, jet mill, dry jet mill, hammer mill, or the like. For example, a solid-phase reaction method in which a plurality of oxide particles are mixed and fired, and uniformity is generated by thermal diffusion of ions, or hydroxides, carbonates, etc. are precipitated from an ion-containing solution in which oxide particles are dissolved. A co-precipitation method in which uniformity is produced by firing into oxides may be used as raw material powders for sintering.

In the case of a solid-phase reaction method in which a plurality of metal oxide particles are mixed and fired to generate uniformity by thermal diffusion of ions, metal powders composed of tantalum, yttrium, scandium, and aluminum can be suitably used as starting materials. There are also those prepared by dissolving the aforementioned metal powder in an aqueous solution of nitric acid, sulfuric acid, uric acid, or the like, or an oxide powder of the aforementioned element. In addition, the purity of the aforementioned raw material is preferably 99.9% by mass or more, particularly preferably 99.99 or more. These starting materials may be loaded with a specific amount so as to have a composition corresponding to the formula (1), mixed and then fired to obtain a sintered raw material of the desired metal oxide, which may be pulverized and used as a raw material powder for sintering. However, the firing temperature at this time is preferably 1,100°C or lower, more preferably 1,050°C or lower, and even more preferably 1,000°C or lower. If it exceeds 1,100 degreeC, densification of a raw material powder will generate|occur|produce, and it may not fully grind|pulverize in the next pulverization step. The firing time may be 1 hour or longer, and the temperature increase rate at this time is preferably 100°C/h or more and 500°C/h or less. The firing atmosphere is preferably the atmosphere, an oxygen-containing atmosphere such as oxygen, and is not suitable for a nitrogen atmosphere, an argon atmosphere, or a hydrogen atmosphere. In addition, as a calcination apparatus, a vertical muffle furnace, a horizontal tubular furnace, a rotary furnace, etc. are illustrated, and it will not be specifically limited if it can reach a target temperature and oxygen supply.

In addition, the raw material powder for sintering preferably contains a sintering aid. For example, as a sintering aid, tetraethoxysilane (TEOS) is added to the entire raw material powder (garnet-type composite oxide powder + sintering aid) in terms of SiO ₂ in excess of 0 ppm and 1,000 ppm or less (more than 1,000 ppm). 0 mass % and 0.1 mass % or less), or adding SiO ₂ powder to the whole raw material powder (garnet-type composite oxide powder + sintering aid) over 0 ppm and 1,000 ppm or less (over 0 mass % and 0.1 mass % or less) , mixed and fired as needed as a raw material powder for sintering. When the addition amount exceeds 1,000 ppm, excessively contained Si may cause a slight amount of light absorption due to crystal defects. Moreover, it is preferable that the purity is 99.9 mass % or more. The sintering aid may be added during the preparation of the raw material powder slurry. In addition, the Si element is mixed in the environment such as glassware used in the manufacturing process, or a part of the Si element is volatilized when sintered under reduced pressure, and the content of Si contained in the final ceramic is analyzed, and there is an unintentional increase. Or reduce the situation, it is necessary to pay attention. In addition, when no sintering aid is added, the raw material powder for sintering (that is, the aforementioned starting material mixed powder or composite oxide powder) is preferably selected to have a primary particle diameter of nanometer size and extremely high sintering activity. Such a choice may be appropriately made.

When pulverizing the raw material for firing into powder for firing, the pulverization method can be selected from either a dry method or a wet method, but it is necessary to pulverize the target ceramic so that it becomes highly transparent. For example, in the case of wet pulverization, the fired raw material is slurried and pulverized (dispersed) into primary particles by various pulverization (dispersion) methods such as a ball mill, a bead mill, a homogenizer, a jet mill, and ultrasonic irradiation. The dispersion medium of this wet slurry is not particularly limited as long as it can achieve high transparency of the finally obtained ceramic, and examples thereof include alcohols such as lower alcohols having 1 to 4 carbon atoms, and pure water. In addition, various organic additives may be added to this wet slurry for the purpose of improving the quality stability or productivity in the subsequent ceramic production steps. In the present invention, these are not particularly limited. That is, various dispersants, binders, lubricants, plasticizers and the like can be suitably used. However, as these organic additives, it is preferable to select a high-purity type that does not contain unnecessary metal ions. In the case of wet grinding, the raw material powder for sintering is finally obtained by removing the dispersing medium of the slurry.

[Manufacturing steps] In the present invention, a slurry containing the above-mentioned raw material powder for sintering is used, molded into a specific shape, degreasing, followed by preliminary sintering and densified into a sintered body (preliminary sintered body) composed of a complex oxide having a relative density of 94% or more, and then The sintered body is subjected to pressure sintering, and the pressure sintered body is further heated to a temperature exceeding the aforementioned pressure sintering temperature to be re-sintered, and further, a specific oxidation annealing treatment is performed to the re-sintered body.

(forming) As described above, solid-liquid separation is applied to the slurry, and it is molded into a specific shape. The molding method is roughly classified into dry molding and wet molding, and it is not particularly limited as long as a specific shape can be stably obtained. In the case of dry molding, there is exemplified a method of forming particles from a slurry using spray drying, filling a jig with the particles, and then press molding. In addition, as for wet molding, a casting molding method in which a slurry is poured into a gypsum mold to volatilize a solvent is exemplified. In the gaseous state, extrusion molding, sheet molding, centrifugal casting, and cold pressure equalization can also be exemplified, but any specific shape can be obtained, so it is not limited.

A binder may be added to the slurry before molding. The binder can improve the holding force of the molded body, and has the effect of making it difficult for cracks or cracks to occur. The type of the binder is not particularly limited, but it is preferably one that is compatible with the solvent and does not leave residues after heat treatment. Examples of the binder include polyvinyl alcohol (PVA), polyvinyl butyral, polyvinyl acetate, and polyacrylic acid. A polymer obtained by copolymerizing two or more of these. The amount of the binder varies depending on the molding method and the type of the binder, but it is the minimum necessary for the raw material powder for sintering to be 0.5% by mass, and the upper limit is 8% by mass. In addition, the addition of the binder is the best in wet pulverization.

In addition, as said press-molding, a normal press-molding process is suitably utilized. That is, a uniaxial pressing step of pressurizing in a certain direction by a very general filling mold or a cold hydrostatic press (CIP (Cold) which is sealed and stored in a deformable waterproof container and pressurized by hydrostatic pressure can be suitably used. Isostatic Pressing)) step or warm hydrostatic pressure (WIP (Warm Isostatic Pressing)) step. The pressure applied is not particularly limited as long as the relative density of the obtained molded body is confirmed and the relative density is appropriately adjusted. For example, if a commercially available CIP device or WIP device can be managed in a pressure range of about 300 MPa or less, it can be Manufacturing costs are suppressed.

Among them, in the present invention, in order to manage the size or number of scattering sources such as different phases, foreign matter, contamination, and micro-cracks within a predetermined range, the molding die and the molding machine are used exclusively for cleaning and drying that is sufficiently cleaned and dried. The environment in which the molding work is performed is preferably a clean space with a class of 1000 or lower.

(degreased) In the production method of the present invention, a normal degreasing step is suitably used. That is, it is possible to go through a degreasing step at a temperature rise according to a heating furnace. In addition, the kind of atmosphere gas at this time is not specifically limited, Air, oxygen, hydrogen, etc. can be utilized suitably. The degreasing temperature is not particularly limited, but when a raw material to which an organic additive is mixed is used, it is preferable to raise the temperature to a temperature at which the organic component can be decomposed and removed.

(Preliminary sintering) In this step, as a sintered body before heating and sintering, it is preferable to prepare a preliminary sintered body with a relative density of 94% or more and an average sintered particle size of 3 μm or less. At this time, it is necessary to set the conditions of the temperature and the holding time so that the sintered particle size falls within a desired range.

Here, a general sintering step can be suitably used. That is, a resistance heating method, an induction heating method, or the like can be suitably used for the heating and sintering step. The atmosphere at this time is not particularly limited, and various atmospheres such as air, inert gas, oxygen, hydrogen, and helium can be suitably used, but sintering under reduced pressure (in a vacuum) can be more preferably used. The vacuum degree of the preliminary sintering is preferably less than 1×10 ^-1 Pa, more preferably less than 1×10 ^-2 Pa, and particularly preferably less than 1×10 ^-3 Pa.

The sintering temperature of the preliminary sintering step of the present invention is preferably 1,450-1,650°C, and particularly preferably 1,500-1,600°C. When the sintering temperature is within this range, it is preferable to suppress the precipitation of different phases and the growth of grains and to promote densification. The sintering holding time in the preliminary sintering step of the present invention is only a few hours, but it is preferable to densify the relative density of the preliminary sintered body to 94% or more. In addition, when the relative density of the preliminary sintered body is higher than 99%, plastic deformation of the particles in the sintered body becomes less likely to occur in the subsequent press sintering (HIP), and it becomes difficult to remove the air bubbles remaining in the sintered body. Therefore, the relative density of the preliminary sintered body is preferably 99% or less, more preferably 98% or less.

The average sintered grain size of the crystal grains of the preliminary sintered body of the present invention is preferably 3 μm or less, more preferably 2.5 μm or less, and particularly preferably 1 μm or less. The average sintered particle size of the sintered grains can be adjusted by taking into account the raw material species, atmosphere, sintering temperature, and holding time. When the sintered particle size is larger than 3 μm, plastic deformation does not easily occur in the subsequent pressurized sintering (HIP), and there is a possibility that it becomes difficult to remove the air bubbles remaining in the preliminary sintered body. In addition, the average sintered grain size of the crystal grains of the preliminary sintered body can be determined by observing the sintered grain size of the crystal grains on the surface of the transparent press sintered (HIP) body obtained in the next step with an optical microscope.

(Pressure Sintering (Hot Isopressing (HIP))) In the production method of the present invention, after the preliminary sintering step, the preliminary sintered body is preferably heated at a pressure of 50 MPa or more and 300 MPa or less and a temperature of 1,000° C. or more and 1,780° C. or less. The step of pressure sintering (hot equalization treatment). In addition, as the type of pressurized gas medium at this time, inert gas such as argon and nitrogen, or Ar—O ₂ can be suitably used. The pressure of the pressurized gas medium is preferably 50 to 300 MPa, more preferably 100 to 300 MPa. If the pressure is less than 50 MPa, the transparency improvement effect may not be obtained, and if the pressure exceeds 300 MPa, even if the pressure is increased, the transparency improvement cannot be further improved, and the burden on the device may be too large, and the device may be damaged. It is preferable that the applied pressure is 196 MPa or less, which can be handled by a commercially available HIP apparatus. Moreover, it is preferable to set the processing temperature (specific holding temperature) at this time in the range of 1,000-1,780 degreeC, More preferably, it is 1,100-1,700 degreeC. When the heat treatment temperature is higher than 1,780° C., grain growth occurs in the HIP treatment, and it is difficult to remove the bubbles, so it is not preferable. In addition, when the heat treatment temperature is less than 1,000°C, there is a possibility that the effect of improving the transparency of the sintered body is hardly obtained. In addition, the holding time of the heat treatment temperature is not particularly limited, but if the holding time is too long, the risk of occurrence of oxygen defects increases, which is not preferable. Typically, it is preferable to set it in the range of 1 to 3 hours. Further, the heating material, heat insulating material, and processing vessel for performing HIP treatment are not particularly limited, and graphite, molybdenum, tungsten, and platinum (Pt) can be suitably used, and yttrium oxide and yttrium oxide can also be suitably used as the processing vessel. When the processing temperature is 1,500°C or higher, the heating material and heat insulating material are preferably graphite, but in this case, one of graphite, molybdenum, and tungsten is selected as the processing container, and gadolinium oxide and tungsten oxide are selected as the double container inside. Either way, it is preferable to fill the container with an oxygen-releasing material first, since the amount of oxygen deficiency in the HIP treatment can be suppressed as much as possible.

(Resintering) In the production method of the present invention, after the HIP treatment is completed, the pressurized sintered body is heated to a temperature exceeding the aforementioned pressure-sintered body, and then re-sintered to grow grains to obtain a re-sintered body. In this case, it is necessary to set the conditions of the temperature and the holding time so that the finally obtained sintered particle size falls within a desired range.

The type of the atmosphere at this time is not particularly limited, and air, oxygen, hydrogen, etc. can be suitably used, but it is more preferable to perform the treatment under reduced pressure (under a vacuum of less than 1×10 ⁻² Pa). The re-sintering temperature is preferably 1,650°C or higher and 1,800°C or lower, and more preferably 1,700°C or higher and 1,800°C or lower. It is not good if grain growth does not occur below 1,650°C. The average sintered grain size of the crystal grains obtained by re-sintering is preferably 5 μm or more, more preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 20 μm or more. In addition, it is preferably 40 μm or less. The holding time of the re-sintering step is not particularly limited, but is preferably at least 5 hours, more preferably at least 10 hours, and particularly preferably at least 20 hours. Generally speaking, the grain growth of the sintered body progresses as the holding time increases. The temperature and holding time of the re-sintering step can be appropriately adjusted by confirming the average sintered particle size. However, in general, when the sintering temperature is too high, unexpected abnormal grain growth occurs, and it becomes difficult to obtain a homogeneous sintered body. Here, the temperature at which the re-sintering is performed has a certain margin, and the size adjustment of the average sintered particle size of the re-sintered body is preferably adjusted by prolonging the holding time.

(Oxidation Annealing) The re-sintered body that has undergone the above series of treatments is reduced especially in the HIP treatment step, so that some oxygen defects are generated, and the appearance of gray to dark blue may appear. Therefore, an oxidation annealing treatment (oxygen defect recovery treatment) is performed in an oxidizing atmosphere (oxygen-containing atmosphere) in the atmosphere. The annealing treatment temperature is 1,200°C or higher, preferably 1,300°C or higher. Moreover, it is preferable that it is 1,500 degrees C or less. In this case, the holding time is not particularly limited, but it is preferable to select a time longer than a time sufficient for recovering oxygen vacancies, and a time that does not waste electricity bills due to unnecessary long-term processing. In addition, a micro-oxidative HIP treatment may be applied. By these treatments, for example, even in a colored re-sintered body, oxygen vacancies can be recovered, so that the size and number of scattering sources (scattering contrast sources) can be controlled within a predetermined range, and oxygen vacancies can be generated. Paramagnetic garnet-type transparent ceramic with little absorption. Of course, the intrinsic coloring (absorption) of the material cannot be removed due to doping or the addition of colored elements such as impurities for the purpose of imparting functions.

In addition, when the oxidation annealing step is performed at a high temperature for a long time, the size or number of bubbles remaining in the sintered body may increase. In this way, the size and number of air bubbles, microcracks, etc. remaining in the final sintered body cannot be controlled within a predetermined range, which is not preferable. In this case, if the sintered body is subjected to HIP treatment again, and an oxygen atmosphere annealing treatment is additionally applied, the size and number of air bubbles, microcracks, etc. remaining in the sintered body can be controlled within a predetermined range, so it is relatively good.

In the manufacturing method of the paramagnetic garnet-type transparent ceramic of the present invention, after the aforementioned oxidation annealing treatment, the two end faces of the optical mirror are trimmed, and then anti-reflection films are formed on the two end faces respectively.

(optical polishing) In the manufacturing method of the present invention, the paramagnetic garnet-type transparent ceramic that has undergone the aforementioned series of manufacturing steps is preferably in the shape of a cylinder or a square column, and is optically ground and trimmed (optical mirror trimming) on the axis used optically. The two end faces (optical end faces) of . The optical surface accuracy at this time is preferably λ/2 or less, and particularly preferably λ/8 or less, when the measurement wavelength λ=633 nm.

In addition, it is also possible to reduce optical loss by appropriately forming an antireflection film (AR coating) on the optically polished surface. In this case, the optical surfaces should be carefully cleaned with a chemical solution before applying the anti-reflection coating so that no dirt remains on the optical end surfaces, and it is better to check the cleanliness with a solid mirror or a microscope. It can also be wiped and washed when it is judged that the cleanliness is low by the inspection of the cleanliness. In order not to cause scars on the optical surface during the wiping and cleaning step, and not to rub the dirt, select the operating jig of soft material, and the wiping tool should be selected to be low-dust.

As described above, a sintered body of a paramagnetic garnet-type composite oxide containing at least arsenic and aluminum can be obtained, and the diffuse transmittance T _d in the wavelength range of 550 nm≦λ≦1,350 nm measured for a sample with a length of 20 mm is as described above. The value of the coefficient b obtained by fitting the formula (2) by the least squares method is 5.0×10 ⁵ or less. In addition, it is preferable that the value of the coefficient c is 1.0 or less, and the average sintered particle size D is 7 μm or more and 50 μm or less. When the sample is 20 mm in length, it can provide a laser intensity of 100 W and a beam quality of M. When the ² value is m (1<m≦1.2), the laser light with the wavelength of 1,070 nm is incident, and the beam quality ^M2 of the transmitted light is n/m when n/m is 1.05 or less.

[Magnetic Optical Device] Furthermore, since the paramagnetic garnet-type transparent ceramic of the present invention is supposed to be used as a magnetic optical material, a magnetic field parallel to its optical axis is applied to the paramagnetic garnet-type transparent ceramic, and the optical axes of the polarizer and the analyzer are arranged relative to each other. It is preferable to set it so as to be offset by 45 degrees and to use a magnetic optical device. That is, the paramagnetic garnet-type transparent ceramics of the present invention are suitable for use in magnetic optical devices, especially as Faraday rotators for optical unidirectional devices with wavelengths of 0.9 to 1.1 μm.

FIG. 1 is a schematic cross-sectional view showing an example of an optical device using a Faraday rotator made of the magnetic optical material of the present invention as an optical element, that is, an optical unidirectional device. In FIG. 1 , the optical unidirectional device 100 is provided with a Faraday rotator 110 made of paramagnetic garnet-type transparent ceramics of the present invention, and a polarizer 120 and an analyzer 130 of polarizing materials are provided before and after the Faraday rotator 110 . In addition, in the optical unidirectional device 100, the polarizer 120, the Faraday rotator 110, and the analyzer 130 are arranged in this order, and it is preferable that the magnet 140 is placed on at least one of these side surfaces.

In addition, the aforementioned optical unidirectional device 100 can be suitably used in an industrial fiber laser device. That is, it is suitable for preventing the reflected light of the laser light emitted by the laser light source from returning to the light source, and making the oscillation unstable. [Example]

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Reference Examples, but the present invention is not limited to these Examples.

[Example 1] Example 1 shows the case where y=0.004, z=0.03, and y+z=0.034 are fixed in formula (1), and the value of x is set to 0≦x≦0.396. Acquired tantalum oxide powder, yttrium oxide powder, scandium oxide powder manufactured by Shin-Etsu Chemical Industry Co., Ltd., and alumina powder manufactured by Daming Chemical Co., Ltd. Furthermore, liquids of tetraethoxysilane (TEOS) manufactured by Kishida Chemical Co., Ltd. and polyethylene glycol 200 manufactured by Kanto Chemical Co., Ltd. were obtained. In terms of purity, the powder raw materials are all 99.9 mass % or more, and the liquid raw materials are 99.999 mass % or more. Using the above-mentioned raw materials, and adjusting the mixing ratio, the following oxide raw materials having a crystal structure were produced in total of four types of the final compositions shown in Table 1.

(Raw materials for Example 1-1 and Comparative Example 1-1) Prepared so that the molar numbers of titanium, yttrium, scandium, and aluminum are Tb:Y:Sc:Al=1.794:1.194:0.162:4.850, respectively (Tb _0.598 Y _0.398 Sc _0.004 ) ₃ (Al _0.97 Sc _0.03 ) ₅ O ₁₂ mixed powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

(Raw material for Example 1-2 and Comparative Example 1-2) Prepared so that the molar numbers of titanium, yttrium, scandium, and aluminum are Tb:Y:Sc:Al=2.091:0.897:0.162:4.850, respectively (Tb _0.697 Y _0.299 Sc _0.004 ) ₃ (Al _0.97 Sc _0.03 ) ₅ O ₁₂ mixed powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

(Raw materials for Example 1-3 and Comparative Example 1-3) Prepared so that the molar numbers of titanium, yttrium, scandium, and aluminum are Tb:Y:Sc:Al=2.391:0.597:0.162:4.850, respectively (Tb _0.797 Y _0.199 Sc _0.004 ) ₃ (Al _0.97 Sc _0.03 ) ₅ O ₁₂ mixed powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

(Raw materials for Example 1-4 and Comparative Example 1-4) Prepared (Tb _0.996 Sc _0.004 ) weighed so that the molar numbers of arbium, scandium, and aluminum were Tb:Sc:Al=2.988:0.162:4.850, respectively Mixed powder for ₃ (Al _0.97 Sc _0.03 ) ₅ O ₁₂ . Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

Next, it was put into a polyethylene bowl with particular attention to prevent the mixture from being mixed with each other, and polyethylene glycol 200 was added as a dispersant so that it might be 0.5 mass % with respect to the oxide powder. The dispersion/mixing treatment was carried out in ethanol with a ball mill apparatus, respectively. Processing time is 24 hours. After that, spray-drying was performed, and any granular raw material having an average particle diameter of 20 μm was produced.

Next, the obtained four kinds of powder raw materials were subjected to uniaxial press molding, respectively, and subjected to equalization treatment at a pressure of 198 MPa to obtain a CIP molded body. The obtained molded body was degreased in a furnace at 1,000°C for 2 hours.

The degreased molded body was charged into a vacuum furnace and subjected to a preliminary sintering treatment at 1,600° C. for 2 hours under a reduced pressure of less than 1.0×10 ⁻³ Pa to obtain a total of four types of preliminary sintered bodies. At this time, the relative sintered densities of the samples were all 94% or more and 99% or less. Each of the obtained preliminary sintered bodies was charged into a HIP furnace made of a carbon fiber heater, and subjected to a pressure sintering (HIP) treatment in Ar under the conditions of 196 MPa, 1,600° C., and 3 hours to obtain a pressure sintered body. The appearance of the pressurized sintered body was all transparent. As a comparative example, a part of the four types of pressurized sintered bodies was stored without being subsequently put into the re-sintering step.

Next, as an example, the remaining four types of pressurized sintered bodies were charged into a vacuum furnace again, and were re-sintered at 1,700° C. for 20 hours under a reduced pressure of less than 1.0×10 ⁻³ Pa to obtain a total of four types of pressurized sintered bodies. Re-sintered body. The external appearance of the re-sintered body was all transparent.

The pressurized sintered body (for the comparative example) and the re-sintered body (for the example) obtained in this way were cylindrically ground to a diameter of 5 mm, respectively, and subjected to an oxidation annealing treatment at 1,300° C. for 24 hours in the atmosphere. Then, these were grind|polished so that it might become a length of 20 mm, and both end surfaces might become mirror surfaces. The following measurements were performed on the samples obtained as described above.

(average sintered particle size D) The average sintered particle size of the crystal grains of the sample is determined with reference to "Lineal Intercept Technique for Measuring Grain Size in Two-Phase Polycrystalline Ceramics", Journal of the American Ceramic Society, 55, 109(109) 1972 (Non-Patent Document 7) . Specifically, it was determined by subjecting the mirror-polished transparent ceramic sample to 1,300° C. for 6 hours in the atmosphere, and observing the grain boundaries of the thermally etched end face with an optical microscope. At this time, the length of the arbitrary drawn line on the end face of the sample is C (μm), the number of particles on this line is N, the magnification of the image is M, and the value of the two significant digits of the numerical value obtained by the following formula is taken as the average. Sintered particle size D (μm). D=1.56C/(MN)

(Measurement of diffuse transmittance) The diffuse transmittance T _d of each sample having a length (optical path length) of 20 mm was measured with reference to JIS K7136 (ISO 14782:1999). The measurement used a spectrophotometer (V-670 by JASCO Corporation). The light source was a halogen lamp, the detector used a photomultiplier tube (wavelength less than 750 nm) and a PbS photocell (wavelength 750 nm or more), and the measurement was carried out by a double beam method. The measurement range is from 550 nm to 1,350 nm in increments of 1 nm, and the measured value is expressed as a percentage. The diffuse transmittance T _d of each wavelength is obtained by fitting T _Fit =aλ ^-4 +bλ ^-2 +c (a, b, and c are real numbers) by the least squares method to obtain the coefficient b (%･nm ² ) and c(%).

Finally, an antireflection film designed so that the center wavelength may be 1,070 nm was applied to both end surfaces of the optically polished sample.

(Evaluation of Beam Quality (M ² ) Variation (n/m)) The beam quality was measured using a CW laser beam collimated to a diameter of 1.6 mm with a wavelength of 1,070 nm and an output power of 100 W. The beam quality M ² value of this laser light was measured using a ModeMaster PC M ² beam transmission analyzer manufactured by Coherent Corporation. First, the M2 value of the original beam (incident light) is measured, and the value at this time is m. Next, each sample with a length of 20 mm was placed in the optical path, and the M ² value of the transmitted light was measured, and this value was n. When calculating n/m as the amount of change in beam quality of the present invention, 1.05 or less is considered acceptable, and when it exceeds 1.05, it is considered unacceptable. In addition, in order to prevent the destruction of the beam profiler, the intensity of the incident light and the transmitted light of the sample is attenuated to about 1/1000 using a beam splitter and then introduced into the analyzer. In addition, in this optical system, m=1.12. The above results are collectively shown in Table 1.

From the above results, the paramagnetic garnet-type transparent ceramic samples (Examples 1-1 to 1-4) with coefficient b of 0.6×10 ⁵ to 1.7×10 ⁵ all have a change in beam quality (n/m) of 1.05 the following. In addition, all the samples (Comparative Examples 1-1 to 1-4) whose coefficient b was 5.8×10 ⁵ to 7.1×10 ⁵ had a beam quality change amount (n/m) larger than 1.05. That is, it was confirmed that paramagnetic garnet-type transparent ceramics with high beam quality can be obtained when the coefficient b is 3.5×10 ⁵ or less.

[Example 2] As Example 2, the formula (1) is fixed at x=0.40, and y=0.001, z=0.001, y+z=0.002, and y=0.04, z=0.08, y+z=0.12, When y=0.05, z=0.13, and y+z=0.18. In addition, the case of y=z=y+z=0 is shown as reference example 2-1. In the same manner as in Example 1, antium oxide powder, yttrium oxide powder, scandium oxide powder manufactured by Shin-Etsu Chemical Co., Ltd., and alumina powder manufactured by Daming Chemical Co., Ltd. were prepared. Furthermore, liquids of tetraethoxysilane (TEOS) manufactured by Kishida Chemical Co., Ltd. and polyethylene glycol 200 manufactured by Kanto Chemical Co., Ltd. were prepared. In terms of purity, the powder raw materials are all 99.9 mass % or more, and the liquid raw materials are 99.999 mass % or more. Using the above-mentioned raw materials, and adjusting the mixing ratio, the following oxide raw materials having a crystal structure were produced in total of four types of the final compositions shown in Table 2.

(Raw material for Example 2-1) (Tb _0.599 Y _0.4 Sc weighed so that the molar numbers of titanium, yttrium, scandium, and aluminum were Tb:Y:Sc:Al=1.797:1.200:0.008:4.995, respectively) _0.001 ) ₃ (Al _0.999 Sc _0.001 ) ₅ O ₁₂ mixed powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

(Raw material for Example 2-2) (Tb _0.56 Y _0.4 Sc weighed so that the molar numbers of titanium, yttrium, scandium, and aluminum were Tb:Y:Sc:Al=1.68:1.20:0.52:4.60, respectively) _0.04 ) ₃ (Al _0.92 Sc _0.08 ) ₅ O ₁₂ mixed powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

(Raw material for Example 2-3) (Tb _0.55 Y _0.4 Sc weighed so that the molar numbers of titanium, yttrium, scandium, and aluminum were Tb:Y:Sc:Al=1.65:1.20:0.80:4.35, respectively) were prepared. _0.05 ) ₃ (Al _0.87 Sc _0.13 ) ₅ O ₁₂ mixed powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so that it might be 100 ppm.

(Raw material for Reference Example 2-1) For (Tb _0.6 Y _0.4 ) ₃ Al ₅ O ₁₂ weighed so that the molar numbers of yttrium, yttrium, and aluminum were Tb:Y:Al=1.8:1.2:5.0, respectively Mix powder. Next, TEOS as a sintering aid was weighed and added to each raw material by converting its addition amount to SiO ₂ so as to be 100 ppm.

Next, it was put into a polyethylene bowl with particular attention to prevent the mixture from being mixed with each other, and polyethylene glycol 200 was added as a dispersant so that it might be 0.5 mass % with respect to the oxide powder. The dispersion/mixing treatment was carried out in ethanol with a ball mill apparatus, respectively. Processing time is 24 hours. After that, spray-drying was performed, and any granular raw material having an average particle diameter of 20 μm was produced.

Next, the obtained four kinds of powder raw materials were subjected to uniaxial press molding, respectively, and subjected to equalization treatment at a pressure of 198 MPa to obtain a CIP molded body. The obtained molded body was degreased in a furnace at 1,000°C for 2 hours.

The degreased molded body was charged into a vacuum furnace, and subjected to a preliminary sintering treatment at 1,600° C. for 2 hours under a reduced pressure of less than 1.0×10 ⁻³ Pa to obtain a total of four types of preliminary sintered bodies. At this time, the sintered relative densities of the samples were all above 94%. Each of the obtained preliminary sintered bodies was charged into a HIP furnace made of a carbon fiber heater, and subjected to a pressure sintering (HIP) treatment in Ar under the conditions of 196 MPa, 1,600° C., and 3 hours. Next, the pressurized sintered body was charged into a vacuum furnace again, and a re-sintered body was obtained by performing a re-sintering treatment at 1,700° C. for 20 hours under a reduced pressure of less than 1.0×10 ⁻³ Pa.

The re-sintered bodies thus obtained were each subjected to columnar grinding to a diameter of 5 mm, and polished so that both end surfaces were mirror surfaces. After that, an oxidation annealing treatment was performed at 1,300° C. for 24 hours in the atmosphere. The samples obtained as described above were evaluated for the measurement and determination of the average sintered particle diameter D, the coefficient b and the coefficient c of the diffusion transmittance adaptation, and the amount of change in beam quality in the same manner as in Example 1. The above results are collectively shown in Table 2.

From the above results, the coefficient b of Examples 2-1 to 2-3 was 0.6×10 ⁵ or less, and the beam quality variation (n/m) was all 1.05 or less. That is, it was confirmed that within the composition range of the present invention, a paramagnetic garnet-type transparent ceramic having a coefficient b of 5.0×10 ⁵ or less and a high beam quality can be obtained.

[Example 3] In Example 2-2, the re-sintering time was 2 hours (Comparative Example 3-1), 6 hours (Example 3-1), and 40 hours (Example 3-2), except that the same as Example 2 -2 A sample of paramagnetic garnet-type transparent ceramic was produced under the same conditions. The samples obtained as described above were evaluated for the measurement and determination of the average sintered particle diameter D, the coefficient b and the coefficient c of the diffusion transmittance adaptation, and the amount of change in beam quality in the same manner as in Example 1. The evaluation results thereof are shown in Table 3.

From the above results, the samples of Examples 3-1 and 3-2 have an average sintered particle size of 13 to 38 μm, a coefficient b of 0.6×10 ⁵ to 4.2×10 ⁵ , and all the changes in beam quality (n/m) is 1.05 or less. On the other hand, the average sintered particle size of the sample of Comparative Example 3-1 was 6.1 μm, the coefficient b was 18×10 ⁵ , and the amount of change in beam quality (n/m) was 1.15. That is, it was confirmed that paramagnetic garnet-type transparent ceramics with high beam quality with an average sintered particle size of 13 μm or more and 38 μm or less, a coefficient b of 4.2×10 ⁵ or less, and a beam quality change amount (n/m) of 1.05 or less can be obtained. .

In addition, the present invention has been described based on the aforementioned embodiments, but the present invention is not limited to these embodiments, and other embodiments, additions, changes, deletions, etc. are also possible. Those skilled in the art Changes can be made within the conceivable range, and any aspect is included in the scope of the present invention as long as the functions and effects of the present invention can be achieved.

100: Optical unidirectional device (isolator) 110: Faraday Rotor 120: polarizer 130: analyzer (analyzer) 140: Magnet

1 is a schematic cross-sectional view showing a configuration example of an optical unidirectional device using the paramagnetic garnet-type transparent ceramic according to the present invention as a Faraday rotator.

100: Optical unidirectional device (isolator)

110: Faraday Rotor

120: polarizer

130: analyzer (analyzer)

140: Magnet

Claims (10)

A paramagnetic garnet-type transparent ceramic, which is a sintered body of Tb-containing rare earth aluminum garnet represented by the following formula (1), and has a diffuse transmittance T _d in the wavelength range of 550nm≦λ≦1,350nm measured for a sample with a length of 20mm The value of the coefficient b obtained by fitting the following formula (2) by the least squares method is 5.0×10 ⁵ or less; (Tb _1-xy Y _x Scy ) ₃ (Al _{1-z Sc z ) 5} O ₁₂ (1) (where, 0≦x＜0.45, 0≦y＜0.08, 0≦z＜0.2, 0.001＜y+z＜0.20); T _Fit =aλ ^-4 +bλ ^-2 +c (2) (where a, b, and c are real numbers). According to the paramagnetic garnet-type transparent ceramic of claim 1, the diffuse transmittance T _d in the wavelength range of 550nm≦λ≦1,350nm measured for the sample with a length of 20mm is fitted by the least square method according to the above formula (2). The value of the coefficient c obtained by (fitting) is 1.0 or less. If the paramagnetic garnet-type transparent ceramics of claim 1 or 2, The average sintered particle size D is 7 μm or more and 50 μm or less. For paramagnetic garnet-type transparent ceramics in any of claims 1 to 3, when the sample is 20mm in length, the laser intensity is 100W, and the beam quality M ² value is m (1<m≦1.2) and the wavelength is 1,070 When the laser light of nm is incident and the beam quality M ² value of the transmitted light is n, n/m is 1.05 or less. The paramagnetic garnet-type transparent ceramic according to any one of claims 1 to 4 further contains a sintering aid. A magnetic optical device is composed of paramagnetic garnet-type transparent ceramics according to any one of claims 1 to 5. As in the magneto-optical device of claim 6, It is an optical unidirectional device that can be used in a wavelength band of 0.9 μm or more and 1.1 μm or less, using the paramagnetic garnet-type transparent ceramic as a Faraday rotator, and having a polarizing material before and after the optical axis of the Faraday rotator. A method for producing paramagnetic garnet-type transparent ceramics, which is a method for producing paramagnetic garnet-type transparent ceramics according to any one of 1 to 5, and is carried out on a sintered body of Tb-containing rare earth aluminum garnet represented by the following formula (1). Pressurized sintering, further heating the pressurized sintered body to a temperature exceeding the aforementioned pressure sintering temperature for re-sintering, and further performing oxidation annealing treatment for the re-sintered body in an oxidizing atmosphere of 1,200°C or higher, (Tb _1-xy Y _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1) (wherein, 0≦x<0.45, 0≦y<0.08, 0≦z<0.2, 0.001<y+z<0.20). Such as the manufacturing method of paramagnetic garnet-type transparent ceramics of claim 8, The sintered body before pressure sintering is densified to a relative density of 94% or more by preliminary sintering. The method for producing a paramagnetic garnet-type transparent ceramic according to claim 9, wherein the preliminary sintering is performed under a reduced pressure of less than 1.0×10 ^-3 Pa.

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