JP6881390B2 - Paramagnetic garnet type transparent ceramics, magneto-optical materials and magneto-optical devices - Google Patents

Description

The present invention relates to a paramagnetic garnet-type transparent ceramic, and more specifically, a magneto-optical material made of a garnet-type transparent ceramic containing terbium suitable for forming a magneto-optical device such as an optical isolator, and the magneto-optical material. Regarding the magneto-optical device used.

In recent years, it has become possible to increase the output, and the spread of laser processing machines using fiber lasers is remarkable. By the way, when a laser light source incorporated in a laser processing machine is incident with light from the outside, the resonance state becomes unstable and the oscillation state is disturbed. In particular, when the oscillated light is reflected by the optical system in the middle and returns to the light source, the oscillating state is greatly disturbed. In order to prevent this, an optical isolator is usually provided in front of the light source or the like.

The optical isolator includes a Faraday rotator, a polarizer arranged on the light incident side of the Faraday rotator, and an analyzer arranged on the light emitting side of the Faraday rotator. Further, the Faraday rotator is used by applying a magnetic field parallel to the traveling direction of light. At this time, the polarization line component of light rotates only in a certain direction regardless of whether the Faraday rotator moves forward or backward. Further, the Faraday rotator is adjusted to a length in which the polarization line segment of light is rotated by exactly 45 degrees. Here, if the planes of polarization of the polarizer and the analyzer are shifted by 45 degrees in the direction of rotation of the advancing light, the polarized light of the advancing light is transmitted because it coincides with the polarizer position and the analyzer position. On the other hand, the polarization of the backward light is rotated by 45 degrees in the opposite direction to the deviation angle direction of the polarization plane of the polarizer, which is deviated by 45 degrees from the analyzer position.
Then, the plane of polarization of the return light at the position of the polarizer has a deviation of 45 degrees − (−45 degrees) = 90 degrees with respect to the plane of polarization of the polarizer, and the polarizer cannot be transmitted. The light that advances in this way is transmitted and emitted, and the return light that travels backward functions as an optical isolator that blocks it.

_{TGG crystals (Tb 3} Ga ₅ O ₁₂ ) and TSAG crystals ((Tb _(3-x) Sc _x ) Sc ₂ Al ₃ O ₁₂ ) have been conventionally known as materials used as Faraday rotators constituting the above optical isolators. (Japanese Patent Laid-Open No. 2011-213552 (Patent Document 1), Japanese Patent Application Laid-Open No. 2002-293693 (Patent Document 2)). TGG crystals are now widely installed for standard fiber laser devices. On the other hand, the Verdet constant of the TSAG crystal is said to be about 1.3 times that of the TGG crystal, which is also a material that can be mounted on a fiber laser device, but since Sc is an extremely expensive raw material, the manufacturing cost is high. Adoption has not progressed in terms of.

Since then, the development of TSAG crystals has been continued as in Japanese Patent No. 5611329 (Patent Document 3) and Japanese Patent No. 5935764 (Patent Document 4), but the reduction in Sc usage cannot be achieved in any of them. It has not become widespread.

_{Other than the above, a TAG crystal (Tb 3} Al ₅ O ₁₂ ) has long been known as a Faraday rotator having a Verdet constant larger than that of TSAG. However, since the TAG crystal is a decomposition-melt type crystal, there is a restriction that the perovskite phase is first formed at the solid-liquid interface, and then the TAG phase is formed. That is, the garnet phase and the perovskite phase of the TAG crystal can be grown only in a state where they are always mixed, and high-quality, large-sized TAG crystal growth has not been realized.

In Japanese Patent No. 364203 (Patent Document 5) and Japanese Patent No. 41079292 (Patent Document 6), as a means for suppressing this mixed crystal, a polycrystalline raw material rod for growing FZ or a seed crystal is made porous. Therefore, a method has been proposed in which the perovskite phase, which is the initial phase, is preferentially precipitated in the porous medium. However, in reality, as the melting position moves, the position where the perovskite phase tends to precipitate also moves. Therefore, even if only the interface between the seed crystal and the polycrystalline raw material rod is made porous, the precipitation of the perovskite phase is caused. Complete suppression was essentially impossible.

Under such restrictions, Japanese Patent Application Laid-Open No. 2008-7385 (Patent Document 7) has proposed a material in which an oxide having a TAG composition is made of ceramics and has translucency. Since ceramics can be sintered and manufactured at a temperature lower than the melting point by 100 ° C. or higher, the problem of decomposition and melting, which has been a problem in single crystal growth, can be solved. Since the decomposition of TAG actually starts at 1840 ° C. or higher, it is possible to obtain a TAG single-phase transparent sintered body if the TAG can be sintered and densified to the limit of the theoretical density at this temperature or lower.

Patent Document 7 is a method for producing ceramics having a garnet structure and made of terbium / aluminum oxide, which comprises a step of blending raw materials, a step of calcining, and a step of crushing calcined powder. In the step of crushing the calcined powder, which comprises a step and a firing step, the average particle size of the calcined powder after crushing is 0.2 μm to 1.6 μm, and in the molding step, the density after molding is high. It is said that TAG ceramics having a large translucency can be produced when the amount is 3.26 g / cm ^{3 or more.}

However, according to Patent Document 7, the translucency is extremely insufficient, and even the linear transmittance at a thickness of 1.5 mm is only 35% at the maximum. By the way, when TAG is used as a Faraday element such as an optical isolator, for example, for a 1.06 μm band laser, the element length required to rotate the light by 45 degrees is required to be about 15 mm, which is about 10 times that of the document. Corresponds to the length of. In a material having a thickness of 1.5 mm and transmitting only 35% of light, if the element length is extended 10 times, the transmittance becomes less than 0.01%, that is, almost zero, and the material does not function at all.

That is, even if it is a ceramics manufacturing method capable of suppressing the generation of different phases, a practical level TAG has not existed so far. In addition, Patent Document 6 shows that when a part of Tb in the TAG crystal is replaced with Ce, the Verdet constant becomes larger than that of TAG. If the Verdet constant is large, the element length required to rotate the incident light by 45 degrees can be shortened, so that the total absorption amount is reduced. However, when the linear transmittance at a thickness of 1.5 mm is 35%, the 45-degree rotation thickness transmittance is less than 1% even if the element length is halved, which is far from practical use.

Japanese Unexamined Patent Publication No. 2011-21352 Japanese Unexamined Patent Publication No. 2002-293693 Japanese Patent No. 5611329 Japanese Patent No. 5935764 Japanese Patent No. 364203 Japanese Patent No. 4107292 Japanese Unexamined Patent Publication No. 2008-7385

Yan Lin Aung, Akio Ikesu, Devopment of optical grade (TbxY1-x) 3Al5O12 ceramics as Faraday rotator material, J.Am.Ceram

The present invention has been made in view of the above circumstances, and is a sintered body of a paramagnetic garnet-type oxide containing terbium and lutetium, and has a linear transmittance of 83.5% or more at a wavelength of 1064 nm at a length of 25 mm. It is an object of the present invention to provide a paramagnetic garnet type transparent ceramic, a magneto-optical material, and a magneto-optical device using the magneto-optical material.

By the way, under the above circumstances, recently, _{a dense ceramic sintered body having a composition of (Tb x} Y _1-x ) ₃ Al ₅ O ₁₂ (x = 0.5 to 1.0) has already existed. It was disclosed that the extinction ratio is higher than that of TGG crystals (existing 35 dB is improved to 39.5 dB or more), and insertion loss can be reduced (existing 0.05 dB is improved to 0.01 to 0.05 dB). Non-Patent Document 1). Since the material disclosed in Non-Patent Document 1 is first of all ceramics, there is no precipitation of the perovskite heterogeneous phase, which has been a problem in TGG crystals, and further by substituting a part of Tb ions with Y ions. It is a material that enables low loss and can obtain extremely high quality garnet type Faraday rotators. However, when the present inventor actually conducted a follow-up test, it was confirmed that the reproducibility was considerably poor and it was difficult to obtain a high-quality ceramic sintered body having a smaller insertion loss than the TGG crystal.
It was also found that a sintered body of a paramagnetic garnet-type oxide containing terbium and lutetium exhibits excellent properties as a magneto-optical material.
The present inventor has made diligent studies based on these findings, and has come up with the present invention.

That is, the present invention provides the following paramagnetic garnet type transparent ceramics, magneto-optical materials and magneto-optical devices.
1. 1.
It is a sintered body of a composite oxide represented by the following formula (1), contains SiO ₂ as a sintering aid in an amount of more than 0% by mass and 0.1% by mass or less, and linearly transmits at a wavelength of 1064 nm at an optical path length of 25 mm. Normal magnetic garnet type transparent ceramics characterized by a rate of 83.5% or more.
(Tb _1-xy Lu _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1)
(In the formula, 0.05 ≦ x <0.45, 0 <y <0.1, 0.5 <1-x-y <0.95, 0.004 <z <0.2.)
2.
1. The paramagnetic garnet-type transparent ceramic according to 1, wherein the Verdet constant at a wavelength of 1064 nm is 30 rad / (Tm) or more.
3. 3.
The paramagnetic garnet type transparent according to 1 or 2, wherein the maximum amount of change in the focal position by the thermal lens when a laser beam having a wavelength of 1064 nm at an optical path length of 25 mm is incident with a beam diameter of 1.6 mm and an incident power of 100 W is 0.25 m or less. Ceramics.
4.
The paramagnetic garnet-type transparent ceramic according to any one of 1 to 3, wherein the Faraday rotator has an optical path length of 25 mm and an extinction ratio of 40 dB or more at a wavelength of 1064 nm.
5.
The paramagnetic garnet type transparent ceramic according to any one of 1 to 4, wherein the scattering source volume concentration is 3 ppm or less.
6.
A magneto-optical material made of the paramagnetic garnet-type transparent ceramics according to any one of 1 to 5.
7.
A magneto-optical device configured by using the magneto-optical material according to 6.
8.
7. An optical isolator in which the paramagnetic garnet-type transparent ceramics are provided as a Faraday rotator, and polarizing materials are provided in front of and behind the optical axis of the Faraday rotator, and can be used in a wavelength band of 0.9 μm or more and 1.1 μm or less. Magneto-optic device.

According to the present invention, it is a paramagnetic garnet-type oxide containing terbium and lutetium, has truly practical transparency applicable to high-power laser devices, and can be scaled up because it is a ceramic sintered body. An easy, truly practical paramagnetic garnet-type transparent oxide ceramic material can be provided.

It is sectional drawing which shows the structural example of the optical isolator which used the magneto-optical material which concerns on this invention as a Faraday rotator. It is a photograph which shows the optical appearance check result of the sample of Examples 1 and 2, (a) is the appearance of the side surface of a sample, (b) is the appearance of the optical polishing surface of a sample.

<Paramagnetic garnet type transparent ceramics>
Hereinafter, the paramagnetic garnet type transparent ceramics according to the present invention will be described.
The transparent ceramic material according to the present invention is a sintered body of a composite oxide represented by the following formula (1), contains SiO ₂ as a sintering aid in an amount of more than 0% by mass and 0.1% by mass or less, and has an optical path. It is a normal magnetic garnet type transparent ceramic characterized by having a linear transmittance of 83.5% or more at a wavelength of 1064 nm at a length of 25 mm.
(Tb _1-xy Lu _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1)
(In the formula, 0.05 ≦ x <0.45, 0 <y <0.1, 0.5 <1-x-y <0.95, 0.004 <z <0.2.)

In the formula (1), terbium (Tb) is a material having the largest Verdet constant among paramagnetic elements other than iron (Fe), and particularly when contained in an oxide having a garnet structure, at a wavelength of 1064 nm. Due to its complete transparency, it is the most suitable element for use in optical isolators in this wavelength range.

Lutetium (Lu) has an ionic radius about 7% smaller than that of terbium, and when combined with aluminum to form a composite oxide, it forms a garnet phase more stably than the perovskite phase, and the residual strain in the crystallites. It is an important constituent element in the present invention because it is a material capable of reducing the amount of terbium ions, which can prevent scattering due to different phases, deterioration of the extinction ratio due to internal stress, and absorption of terbium ions in the fp transition. Furthermore, by substituting a part of terbium ion with lutetium ion, it becomes a form suppressed by lutetium, which is a high melting point material that does not cause sintering runaway due to valence change peculiar to terbium and grain growth runaway that causes sintering unevenness. Therefore, there is no unevenness in the sinterability of the entire material (combination reaction during temperature rise, sudden phase change, and sudden change in specific gravity due to these), and the residual amount of pores in the ceramic sintered body is limited to 1 ppm or less. It becomes possible to do. Therefore, lutetium is a suitable constituent element in the present invention.

Aluminum (Al) is a material having the smallest ionic radius among trivalent ions that can stably exist in an oxide having a garnet structure, and minimizes the lattice constant of a terbium-containing paramagnetic garnet-type oxide. It is an element that can be used. It is preferable that the lattice constant of the garnet structure can be reduced without changing the terbium content because the Verdet constant per unit length can be increased. In fact, the Verdet constant of TAG is improved to 1.25 to 1.5 times that of TGG. Therefore, even if the relative concentration of terbium is reduced by substituting a part of terbium ions with lutetium ions, the Verdet constant per unit length can be kept at the same level as or slightly lower than TGG. It is a suitable constituent element in the invention.

Scandium (Sc) is a rare earth element consisting of terbium and lutetium, which is an oxide having a garnet structure and has an intermediate ionic radius that can be dissolved in terbium sites and some sites of aluminum. When the compounding ratio of and aluminum deviates from the chemical quantity theory ratio due to variations during weighing, the terbium and itself are adjusted so as to exactly match the chemical quantity theory ratio and thereby minimize the energy of crystallite formation. It is a buffer material that can be solid-dissolved by adjusting the distribution ratio to rare earth sites and aluminum sites consisting of lutetium. Further, it is an element capable of limiting the abundance ratio of the alumina heterophase to the garnet matrix to 1 ppm or less and limiting the abundance ratio of the perovskite type heterophase to the garnet matrix to 1 ppm or less, which is indispensable in the present invention. It is an element.

In the formula (1), the range of x is 0.05 ≦ x <0.45, preferably 0.1 ≦ x ≦ 0.4, and more preferably 0.2 ≦ x ≦ 0.35. When x is in this range, the perovskite-type heterogeneous phase can be reduced to levels not detected by X-ray diffraction (XRD) analysis. Furthermore, the abundance of perovskite-type heterogeneous phases (typically 1 μm to 1.5 μm in diameter and appearing to be colored light brown) in a field of view of 150 μm × 150 μm is reduced to one or less by optical microscope observation. preferable. At this time, the abundance ratio of the perovskite-type heterogeneous phase to the garnet matrix is 1 ppm or less. Similarly, when x is in the above range, the amount of pores remaining in the ceramic sintered body (typical size is 0.5 μm to 2.0 μm in diameter and becomes spherical voids when HIP-treated) is increased. It is preferable because the abundance in a field of view of 150 μm × 150 μm is 1 or less when observed with an optical microscope. At this time, the abundance ratio of the pores to the garnet matrix is 1 ppm or less.

When x is less than 0.05, the effect of substituting a part of terbium with lutetium cannot be obtained and the conditions for producing a substantial TAG are the same. Therefore, a high-quality ceramic sintered body having low scattering and low absorption can be stably produced. It is not preferable because it is difficult to do. Further, when x is 0.45 or more, the Verdet constant at a wavelength of 1064 nm is less than 30 rad / (Tm), which is not preferable. Further, if the relative concentration of terbium is excessively diluted, the total length required to rotate the laser beam having a wavelength of 1064 nm by 45 degrees becomes longer than 25 mm, which is not preferable because the production becomes difficult.

In the formula (1), the range of y is 0 <y <0.1, preferably 0 <y <0.08, more preferably 0.002 ≦ y ≦ 0.07, and more preferably 0.003 ≦ y ≦ 0. .06 is even more preferred. When y is in this range, the perovskite-type heterogeneous phase can be reduced to a level not detected by X-ray diffraction (XRD) analysis. Furthermore, the abundance of perovskite-type heterogeneous phases (typically 1 μm to 1.5 μm in diameter and appearing to be colored light brown) in a field of view of 150 μm × 150 μm is reduced to one or less by optical microscope observation. preferable. At this time, the abundance ratio of the perovskite-type heterogeneous phase to the garnet matrix is 1 ppm or less.

When y = 0, the risk of perovskite-type heterogeneous phase precipitation increases, which is not preferable. Further, when y is 0.1 or more, the effect of suppressing the precipitation of the perovskite-type heterogeneous phase is saturated and does not change, and in addition to substituting a part of terbium with lutetium, a part of terbium is also replaced with scandium. As a result, the solid solution concentration of terbium is unnecessarily lowered, and the Verdet constant becomes small, which is not preferable. Further, since scandium is expensive as a raw material, it is not preferable to overdope scandium unnecessarily from the viewpoint of manufacturing cost.

In the formula (1), the range of 1-xy is 0.5 <1-xy <0.95, preferably 0.55 ≦ 1-xy <0.95, and 0.6 ≦ 1-xy <0.95 is more preferable. When 1-xy is in this range, a large Verdet constant can be secured and high transparency can be obtained at a wavelength of 1064 nm.

In the formula (1), the range of z is 0.004 <z <0.2, preferably 0.004 <z <0.16, more preferably 0.01 ≦ z ≦ 0.15, and 0.03. ≦ z ≦ 0.15 is more preferable. When z is in this range, perovskite-type heterogeneous phases are not detected by XRD analysis. Furthermore, the abundance of perovskite-type heterogeneous phases (typically 1 μm to 1.5 μm in diameter and appearing to be colored light brown) in a field of view of 150 μm × 150 μm is reduced to one or less by optical microscope observation. preferable. At this time, the abundance ratio of the perovskite-type heterogeneous phase to the garnet matrix is 1 ppm or less.

When z is 0.004 or less, the risk of precipitation of a perovskite-type heterogeneous phase increases, which is not preferable. Further, when z is 0.2 or more, the effect of suppressing the precipitation of perovskite-type heterogeneous phase is saturated and does not change, but the value of y, that is, the replacement ratio of terbium by scandium increases in conjunction with the increase in the value of z. As a result, the solid solution concentration of terbium is unnecessarily reduced, which is not preferable because the Verdet constant becomes small. Furthermore, since scandium is expensive as a raw material, it is not preferable to overdope scandium unnecessarily from the viewpoint of manufacturing cost.

The paramagnetic garnet-type transparent ceramic of the present invention contains a composite oxide represented by the above formula (1) as a main component. Further, as a sub-component, SiO ₂ which plays a role as a sintering aid is contained in a range of 0.1% by mass or less, up to 0.1% by mass. _{When a small amount of SiO 2} is added as a sintering aid, the perovskite-type heterogeneous precipitation is suppressed, so that the transparency of the paramagnetic garnet-type transparent ceramics is further improved. _{Further, SiO 2} added in a small amount can be vitrified during sintering at 1400 ° C. or higher to bring about a liquid phase sintering effect, and can promote densification of the garnet-type ceramics sintered body. However, when SiO ₂ is added in an amount of more than 0.1% by mass, the maximum amount of change in the focal position due to the thermal lens when the paramagnetic garnet type transparent ceramic having a length (optical path length) of 25 mm is irradiated with a 100 W laser beam having a wavelength of 1064 nm is 0. It exceeds .25m.

By the way, "containing as a main component" means that the composite oxide represented by the above formula (1) is contained in an amount of 90% by mass or more. The content of the composite oxide represented by the formula (1) is preferably 99% by mass or more, more preferably 99.9% by mass or more, and further preferably 99.99% by mass or more. , 99.999% by mass or more is particularly preferable.

The paramagnetic garnet-type transparent ceramic of the present invention is composed of the above-mentioned main component and sub-component, but may further contain other elements. Other elements include rare earth elements such as yttrium (Y) and cerium (Ce), or various impurity groups such as sodium (Na), calcium (Ca), magnesium (Mg), phosphorus (P), and tungsten (Ta). ), Molybdenum (Mo) and the like can be typically exemplified.

The content of other elements is preferably 10 parts by mass or less, more preferably 0.1 parts by mass or less, and 0.001 parts by mass or less, when the total amount of Tb and Lu is 100 parts by mass. It is particularly preferable that it is (substantially zero).

The paramagnetic garnet-type transparent ceramic of the present invention has a colorless and transparent appearance, and has a linear transmittance of 83.5% or more at a wavelength of 1064 nm at an optical path length of 25 mm. In the present invention, the "linear transmittance" is a transparent ceramic sample when the transmission spectrum (light intensity) of the target wavelength measured in a blank (space) state without placing the sample in the measurement optical path is 100%. It means the ratio of the intensity of light of the target wavelength (linear transmittance) after passing through. That is, when the intensity of light of the target wavelength (incident light intensity) measured in the blank state is I ₀ and the intensity of light after passing through the transparent ceramic sample is I, I / I ₀ × 100 (%). Can be represented.

The paramagnetic garnet-type transparent ceramic of the present invention preferably has a Verdet constant of 30 rad / (Tm) or more at a wavelength of 1064 nm, and more preferably 36 rad / (Tm) or more. When the Verdet constant is 36 rad / (Tm) or more, it is convenient and preferable because the replacement with the existing material TGG single crystal can be performed without changing the design of the parts.

Further, the paramagnetic garnet type transparent ceramic of the present invention has a maximum change amount of the focal position by the thermal lens of 0.25 m when a laser beam having a wavelength of 1064 nm at an optical path length of 25 mm is incident with a beam diameter of 1.6 mm and an incident power of 100 W. The following is preferable. If the maximum amount of change in the focal position by the thermal lens is less than 0.3 m under a certain incident power, the system can be mounted at the incident power, that is, the thermal lens characteristics pass. Since the paramagnetic garnet type transparent ceramic of the present invention can control the maximum amount of change in the focal position by the thermal lens to less than 0.3 m at high power incident of 100 W, the material is substantially adopted in the high power laser system for 100 W. it can.

The paramagnetic garnet-type transparent ceramics of the present invention preferably have an extinction ratio of 40 dB or more at a wavelength of 1064 nm at an optical path length of 25 mm as a Faraday rotator (ceramic element alone). Within the garnet composition range of the present invention, material defects such as strain and point defects are dramatically reduced. Therefore, as a Faraday rotator (ceramic element alone), the extinction ratio at a wavelength of 1064 nm at an optical path length of 25 mm is stable. It is possible to manage to 40 dB or more. Further, the paramagnetic garnet type transparent ceramic of the present invention preferably has a scattering source volume concentration of 3 ppm or less, more preferably 2 ppm or less, and further preferably 1 ppm or less. The scattering source volume concentration is the abundance ratio (volume ratio) of the perovskite type and alumina type (described above) perovskite type and alumina type having a diameter of 0.5 to 3 μm, which can be a scattering source of incident light, and the pores to the garnet matrix volume. is there.

<Manufacturing method of paramagnetic garnet type transparent ceramics>
[material]
As the raw material used in the present invention, a metal powder composed of terbium, lutetium, scandium, aluminum, an aqueous solution of nitric acid, sulfuric acid, uric acid, etc., an oxide powder of the above element, or the like can be preferably used. The purity of the raw material is preferably 99.9% by mass or more, and particularly preferably 99.99% by mass or more.

These elements are weighed in a predetermined amount so as to have a composition corresponding to the formula (1), and further mixed with tetraethyl orthosilicate (TEOS), which becomes _{SiO 2 of the sintering aid by subsequent firing, and then fired.} A calcining raw material containing a cubic garnet-type oxide having a desired constitution as a main component is obtained. At this time, _{TEOS is added so that the content of the sintering aid SiO 2} is more than 0% by mass and 0.1% by mass or less. Further, the firing temperature at this time is preferably 950 ° C. or higher and lower than the sintering temperature performed after that, and more preferably 1100 ° C. or higher and lower than the sintering temperature performed after this. The term "main component" as used herein means that the main peak obtained from the powder X-ray diffraction result of the firing raw material is composed of the diffraction peak derived from the garnet structure. When the abundance ratio of the perovskite type heterogeneous phase to the garnet matrix is 1 ppm or less, substantially only the garnet single-phase pattern is detected as the powder X-ray diffraction pattern.

Next, the obtained firing raw material is crushed into a raw material powder.
In the end, ceramics will be manufactured using garnet-type oxide powder having a desired configuration, but the powder shape at that time is not particularly limited, and for example, square, spherical, and plate-shaped powders are used. It can be preferably used. Further, even a powder that is secondarily agglutinated can be suitably used, and even a granular powder that has been granulated by a granulation treatment such as a spray dry treatment can be preferably used. Further, the process of preparing these raw material powders is not particularly limited. Raw material powders prepared by a coprecipitation method, a pulverization method, a spray pyrolysis method, a sol-gel method, an alkoxide hydrolysis method, or any other synthetic method can be preferably used. Further, the obtained raw material powder may be appropriately treated by a wet ball mill, a bead mill, a jet mill, a dry jet mill, a hammer mill or the like.

Various organic additives may be added to the garnet-type oxide powder raw material used in the present invention for the purpose of quality stability and yield improvement in the subsequent ceramic manufacturing process. In the present invention, these are also not particularly limited. That is, various dispersants, binders, lubricants, plasticizers and the like can be preferably used. However, as these organic additives, it is preferable to select a high-purity type that does not contain unnecessary metal ions.

[Manufacturing process]
In the present invention, the raw material powder is press-molded into a predetermined shape, degreased, and then sintered to prepare a sintered body having a relative density of at least 95% or more. After that, it is preferable to perform hot isostatic pressing (HIP (Hot Isostatic Pressing)) treatment as a step. If the hot isotropic press (HIP) treatment is applied as it is, the paramagnetic garnet type transparent ceramics are reduced and a slight oxygen deficiency occurs. Therefore, it is preferable to recover the oxygen deficiency by performing a slightly oxidized HIP treatment or an annealing treatment in an oxidized atmosphere after the HIP treatment. As a result, transparent garnet-type oxide ceramics without defect absorption can be obtained.

(Molding)
In the production method of the present invention, a normal press molding process can be preferably used. That is, a very general uniaxial pressing process in which a mold is filled and pressure is applied from a certain direction, or cold hydrostatic pressure pressurization (CIP (Cold Isostatic Pressing)) in which the product is hermetically stored in a deformable waterproof container and pressurized with hydrostatic pressure. A process or a warm hydrostatic pressure (WIP (Warm Static Pressing)) process can be preferably used. The applied pressure may be appropriately adjusted while checking the relative density of the obtained molded product, and is not particularly limited. However, for example, if the pressure range is managed within a pressure range of about 300 MPa or less that can be handled by a commercially available CIP device or WIP device, the manufacturing cost May be suppressed. Alternatively, a hot pressing step, a discharge plasma sintering step, a microwave heating step, and the like in which not only the molding step but also the sintering is performed at once at the time of molding can be suitably used. Further, it is possible to manufacture a molded product by a casting molding method instead of the press molding method. Molding methods such as pressure casting, centrifugal casting, and extrusion can also be adopted by optimizing the combination of the shape and size of the oxide powder, which is the starting material, and various organic additives.

(Solvent degreasing)
In the production method of the present invention, a normal degreasing step can be preferably used. That is, it is possible to go through a heating and degreasing step using a heating furnace. Further, the type of atmospheric gas at this time is not particularly limited, and air, oxygen, hydrogen and the like can be preferably used. The degreasing temperature is also not particularly limited, but if a raw material containing an organic additive is used, it is preferable to raise the temperature to a temperature at which the organic component can be decomposed and eliminated.

(Sintered)
In the production method of the present invention, a general sintering step can be preferably used. That is, a heat sintering step such as a resistance heating method or an induction heating method can be suitably used. The atmosphere at this time is not particularly limited, and various atmospheres such as inert gas, oxygen gas, hydrogen gas, and helium gas, or sintering under reduced pressure (in vacuum) is also possible. However, since it is preferable to finally prevent the occurrence of oxygen deficiency, oxygen gas and reduced pressure oxygen gas atmosphere are exemplified as more preferable atmospheres.

The sintering temperature in the sintering step of the present invention is preferably 1500 to 1780 ° C, particularly preferably 1550 to 1750 ° C. When the sintering temperature is in this range, densification is promoted while suppressing heterophase precipitation, which is preferable.

The sintering holding time in the sintering step of the present invention is sufficient to be about several hours, but the relative density of the sintered body must be densified to at least 95% or more. Further, it is more preferable to keep the sintered body for 10 hours or more to make the relative density of the sintered body densified to 99% or more because the final transparency is improved.

(Hot isotropic press (HIP))
In the production method of the present invention, it is possible to provide an additional step of performing a hot isotropic press (HIP) treatment after the sintering step.

As the type of pressurized gas medium at this time, an inert gas such as argon or nitrogen, or Ar—O ₂ can be preferably used. The pressure to be pressurized by 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 it exceeds 300 MPa, further transparency improvement cannot be obtained even if the pressure is increased, and the load on the device may become excessive and the device may be damaged. .. It is convenient and preferable that the applied pressure is 196 MPa or less that can be processed by a commercially available HIP apparatus.

The processing temperature (predetermined holding temperature) at that time is set in the range of 1000 to 1780 ° C., preferably 1100 to 1730 ° C. If the heat treatment temperature exceeds 1780 ° C., the risk of oxygen deficiency increases, which is not preferable. Further, if the heat treatment temperature is less than 1000 ° C., the effect of improving the transparency of the sintered body is hardly obtained. The holding time of the heat treatment temperature is not particularly limited, but holding it for too long is not preferable because the risk of oxygen deficiency increases. Typically, it is preferably set in the range of 1 to 3 hours.

The heater material, heat insulating material, and processing container to be HIP-treated are not particularly limited, but graphite or molybdenum (Mo), tungsten (W), and platinum (Pt) can be preferably used, and yttrium oxide and oxidation are further used as the processing container. Gadolinium can also be suitably used. In particular, when the treatment temperature is 1500 ° C. or lower, platinum (Pt) can be used as the heater material, heat insulating material, and treatment container, and the pressurized gas medium can be Ar-O ₂ , so oxygen during the HIP treatment can be used. This is preferable because it can prevent the occurrence of defects. When the treatment temperature exceeds 1500 ° C, graphite is preferable as the heater material and the heat insulating material. In this case, either graphite, molybdenum (Mo) or tungsten (W) is selected as the treatment container, and two inside the heat insulating material. It is preferable to select either yttrium oxide or gadolinium oxide as the heavy container and then fill the container with an oxygen-releasing material because the amount of oxygen deficiency generated during the HIP treatment can be suppressed as much as possible.

(Annealed)
In the production method of the present invention, after the HIP treatment is completed, oxygen deficiency may occur in the obtained transparent ceramic sintered body, resulting in a faint light gray appearance. In that case, it is preferable to perform oxygen annealing treatment (oxygen deficiency recovery treatment) in an oxygen atmosphere at the HIP treatment temperature or lower, typically 1000 to 1500 ° C. The holding time in this case is not particularly limited, but it is preferably selected within a time sufficient for recovering the oxygen deficiency and within a time during which the treatment is unnecessarily long and the electricity bill is not consumed. By the oxygen annealing treatment, even if the transparent ceramics sintered body has a faint gray appearance in the HIP treatment step, it should be a paramagnetic garnet type transparent ceramic body that is colorless and transparent and does not absorb defects. Can be done.

(Optical polishing)
In the manufacturing method of the present invention, it is preferable to optically polish both end faces of the paramagnetic garnet-type transparent ceramics that have undergone the above series of manufacturing steps on the axis to be optically used. The optical surface accuracy at this time is preferably λ / 2 or less, and particularly preferably λ / 8 or less when the measurement wavelength is λ = 633 nm. It is also possible to further reduce the optical loss by appropriately forming an antireflection film on the optically polished surface.

As described above, a paramagnetic garnet-type oxide containing terbium and lutetium, which is a transparent sintered material having a linear transmittance of 83.5% or more at a wavelength of 1064 nm at a length (optical path length) of 25 mm. Can provide the body. Further, preferably, the Verdet constant at a wavelength of 1064 nm is 30 rad / (Tm) or more, and preferably a laser beam having a wavelength of 1064 nm at an optical path length of 25 mm is incident with a beam diameter of 1.6 mm and an incident power of 100 W. Provided is a magnetic optical material having a maximum change amount of the focal position by 0.25 m or less, and more preferably a Faraday rotator (single ceramic element) having an extinction ratio of 40 dB or more at a wavelength of 1064 nm at an optical path length of 25 mm. Can be done.

[Magnetic optical device]
Further, since the paramagnetic garnet-type transparent ceramics of the present invention are assumed to be used as a magneto-optical material, a magnetic field is applied to the paramagnetic garnet-type transparent ceramics in parallel with the optical axis, and then the polarizer is used. It is preferable to configure and utilize the magneto-optical device by setting the detectors so that their optical axes deviate from each other by 45 degrees. That is, the magneto-optical material of the present invention is suitable for use in magneto-optical devices, and is particularly preferably used as a Faraday rotator for an optical isolator having a wavelength of 0.9 to 1.1 μm.

FIG. 1 is a schematic cross-sectional view showing an example of an optical isolator which is an optical device having a Faraday rotator made of the magneto-optical material of the present invention as an optical element. In FIG. 1, the optical isolator 100 includes a Faraday rotator 110 made of the magneto-optical material of the present invention, and a polarizing element 120 and an analyzer 130, which are polarizing materials, are provided before and after the Faraday rotator 110. .. Further, it is preferable that the optical isolator 100 is arranged in the order of the polarizer 120, the Faraday rotator 110, and the analyzer 130, and the magnet 140 is placed on at least one of the side surfaces thereof.

Further, the optical isolator 100 can be suitably used for an industrial fiber laser apparatus. That is, it is suitable for preventing the reflected light of the laser light emitted from the laser light source from returning to the light source and making the oscillation unstable.

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

[Examples 1 to 11, Comparative Examples 1 to 9]
Terbium oxide powder, lutetium oxide powder, scandium oxide powder manufactured by Shin-Etsu Chemical Co., Ltd., and aluminum oxide powder manufactured by Daimei Chemical Co., Ltd. were obtained. Further, a liquid of tetraethyl orthosilicate (TEOS) manufactured by Kishida Chemical Co., Ltd. was obtained. The purity of the powder raw material was 99.95% by mass or more, and that of the liquid raw material was 99.999% by mass or more.
Using the above raw materials, a total of 20 kinds of oxide raw materials having the final composition shown in Table 1 were prepared by adjusting the mixing ratio.
That is, a mixed powder was prepared by weighing so that the number of moles of terbium, lutetium, aluminum, and scandium was the molar ratio of each composition in Table 1. Subsequently, TEOS was added to each raw material by weighing it so that the amount of TEOS added was the mass% of Table 1 in terms of _{SiO 2.}
Then, they were dispersed and mixed in ethanol with an alumina ball mill device, taking care to prevent them from being mixed with each other. The processing time was 15 hours. After that, a spray-drying treatment was carried out to prepare granular raw materials having an average particle size of 20 μm.
Subsequently, these powders were placed in an yttria crucible and calcined in a high temperature muffle furnace at 1100 ° C. for a holding time of 3 hours to obtain calcining raw materials having the respective compositions. Each of the obtained firing raw materials was diffracted by a powder X-ray diffractometer manufactured by PANalytical Co., Ltd. (XRD analysis). The crystal system of the sample was identified by comparing the reference data of the X-ray diffraction pattern with the measurement pattern. In most cases (in the case of oxide raw materials Nos. 1 to 11, 14 to 18 and 20), only the peak of the garnet single phase (cubic crystal) is detected, and the oxide raw material No. In the cases of 12, 13 and 19, weak peaks of perovskite heterogeneous phase were detected in addition to the peak pattern of garnet phase.
The above results are summarized in Table 1.

The oxide raw materials thus obtained were dispersed and mixed again in ethanol with a nylon ball mill device, taking care to prevent mixing with each other. The processing time was 24 hours in each case. Then, a spray-drying treatment was carried out to prepare a granular raw material having an average particle size of 20 μm. Each of the obtained 20 kinds of powder raw materials was subjected to uniaxial press molding and hydrostatic pressure pressing at a pressure of 198 MPa to obtain a CIP molded product. The obtained molded product was degreased in a muffle furnace at 1000 ° C. for 2 hours. Subsequently, the degreased molded product was charged into an oxygen atmosphere furnace and treated at 1730 ° C. for 3 hours to obtain a total of 18 types of sintered products. At this time, the relative density of sintering of the sample was in the range of 95% to 99.1%.
Each of the obtained sintered bodies was charged into a carbon heater HIP furnace and subjected to HIP treatment under the conditions of 200 MPa, 1650 ° C. and 2 hours in Ar. Almost no graying (oxygen deficiency absorption) was confirmed in any of the obtained sintered bodies. However, just in case, each of the obtained ceramic sintered bodies was annealed at 1300 ° C. for 4 hours in an oxygen atmosphere furnace while controlling each lot to recover the oxygen deficiency. In this way, a total of 20 types of sintered bodies of Examples and Comparative Examples were prepared.
Subsequently, each of the obtained ceramic sintered bodies was ground and polished so as to have a diameter of 5 mm and a length of 25 mm, and further, the optical surface accuracy λ / 8 (measurement wavelength λ = 633 nm) of each optical end surface of each sample was obtained. In the case of), the final optical polishing was performed.

The linear transmittance, extinction ratio, and scattering source volume concentration were measured for each sample obtained as described above as follows.

(Measurement method of linear transmittance)
The linear transmittance is when light with a wavelength of 1064 nm is transmitted with a beam diameter of 1 to 3 mmφ using an optical system manufactured in-house using a light source manufactured by NKT Photonics, a power meter manufactured by Gentec, and a Ge photodetector. It was measured by the light intensity of the above, and was determined according to JIS K7361 and JIS K7136 based on the following formula.
Linear transmittance (% / 25 mm) = I / I ₀ x 100
(In the formula, I indicates the transmitted light intensity (intensity of light linearly transmitted through a sample having a length of 25 mm), and I ₀ indicates the incident light intensity.)

(Measurement method of extinction ratio)
The extinction ratio as a Faraday rotator was measured as follows.
The extinction ratio is a beam of light with a wavelength of 1064 nm using a light source manufactured by NKT Photonics, a collimator lens, a polarizer, a work stage, an analyzer, a power meter manufactured by Gentec, and an optical system manufactured in-house using a Ge photodetector. _{Pass through the sample with a large diameter of 3 mmφ, and measure the light intensity I 0} '(maximum value as the laser light intensity) when the polarizing surface of the analyzer is matched with the polarizing surface of the polarizer in this state. Then, the light receiving intensity I'(minimum value as the laser light intensity) was measured again in a state where the polarizing plane of the analyzer was rotated 90 degrees and orthogonal to the polarizing plane of the polarizer, and then based on the following formula. It was calculated by calculation.
Extinction ratio (dB) = -10 x log ₁₀ (I'/ I ₀ ')
If the beam diameter is made thicker than 3 mmφ, the hem of the beam starts to be kicked at the outer circumference of the sample having a diameter of 5 mmφ.

(Measuring method of scattering source volume concentration)
The volume concentration (scattering source volume concentration) of bubbles and / or different phases in the sintered body was measured as follows.
Using the transmission mode of a Zeiss metallurgical microscope, a transmission open Nicol image of each sintered sample with both end faces polished as described above was taken using a 50x objective lens. The frame size at that time was about 153 μm × 117 μm. From here, a total of five transmitted open Nicol images were taken while lowering the depth of focus by 2 μm. The size of a typical scattering source is about 1 μm, and if 5 shots are taken while shifting the focus at a pitch of 2 μm, almost all scattering sources distributed in the height direction (range of depth 10 μm) if some defocus is ignored. It becomes possible to shoot.
The size of the scattering source reflected in the captured image is, first of all, the size (diameter) of several tens of μm if there are special substances such as bubbles (pores) and foreign substances other than different phases. In this case, if even one is present in the image, the volume concentration of the scattering source exceeds 200 ppm, and when the laser beam hits the scattering source, significant scattering occurs, so that the linear transmittance is significantly lowered. However, such a large scattering source was not mixed.
After that, the scattering source was observed in more detail. As a result, it was found that all the remaining scattering source sizes were reflected as substantially spherical contrast with a diameter of 3 μm or less. Furthermore, most of them had a diameter of 1.6 μmφ or less.
It was also confirmed separately that if the size of the scattering source is smaller than 150 nm in diameter, it will not be reflected in the microscope. For example, even if 1100 scattering sources with a diameter of 200 nm are reflected in the five photographs. By calculation, the total volume concentration of these scattering sources is less than 200 ppm. In reality, when there are so many scattering sources, the value of the linear transmittance measured separately is greatly reduced. Therefore, the result of observing the volume concentration of the scattering source with a microscope is described as "innumerable less than 200 nm".
Next, for the remaining typical size scattering sources, the scattering source size (diameter) was stratified and counted at a pitch of 0.5 μm. That is, the number of each of φ0.5 μm, φ1 μm, φ1.5 μm, φ2 μm, φ2.5 μm, and φ3 μm was counted. Specifically, those having a diameter of 0.25 μm or more and less than 0.75 μm are counted as a scattering source having a diameter of 0.5 μm, and those having a diameter of 0.75 μm or more and less than 1.25 μm are counted as a scattering source having a diameter of 1 μm. Those with a diameter of 1.25 μm or more and less than 1.75 μm are counted as a scattering source with a diameter of 1.5 μm, and those with a diameter of 1.75 μm or more and less than 2.25 μm are counted as a scattering source with a diameter of 2.25 μm or more. Those having a diameter of less than 2.75 μm were counted as scattering sources having a diameter of 2.5 μm, and those having a diameter of 2.75 μm or more and less than 3.25 μm were counted as scattering sources having a diameter of 3 μm. Next, the scattering source counted in each layer of the scattering source size (diameter) is regarded as a spherical scattering source of the deemed diameter, and the sphere volume based on the deemed diameter is multiplied by the count number for each layer to obtain the number of counts. The total volume was calculated, and the total volume of all layers was added up to obtain the scattering source volume. Next, the volume concentration of the scattering source was determined by dividing the volume of the scattering source by the observed volume of 179010 ^{μm 3 (= 153 μm × 117 μm × 10 μm).}

Subsequently, the optically polished sample was coated with an antireflection film (AR coat) designed so that the center wavelength was 1064 nm. The optical appearance of the sample obtained here was also checked. FIG. 2 shows the optical appearance check results of the samples of Examples 1 and 2 as an example. Note that FIG. 2A shows the appearance of the side surface of the sample, the upper side in the figure is the sample of Example 1, and the lower side in the figure is the sample of Example 2. Further, FIG. 2B shows the appearance of the sample optically polished surface, in which the left side in the figure is the sample of Example 1 and the right side in the figure is the sample of Example 2.
As can be seen in FIG. 2 (b), all the samples were transparent when viewed through the optically polished surface. Due to the interference color of the AR coat, the appearance looks purple. At this time, since the camera was focused on the upper surface of the sample, the characters on the background were blurred.

For each sample thus obtained, the Verdet constant and the maximum amount of change in the focal position due to the thermal lens were measured as follows. That is, as shown in FIG. 1, polarizing elements (polarizer 120, analyzer 130) are set before and after each obtained ceramic sample (corresponding to Faraday rotator 110), and this sample has an outer diameter of 32 mm and an inner diameter of 32 mm. After inserting into the center of a 6 mm, 40 mm long neodymium-iron-boron magnet (magnet 140), a high power laser (beam diameter 1.6 mm) manufactured by IPG Photonics Japan Co., Ltd. was used to make a wavelength of 1064 nm from both ends. The Verdet constant was measured by injecting a high-power laser beam from the above. Further, after removing the neodymium-iron-boron magnet, a high-power laser beam having a wavelength of 1064 nm was incident on each ceramic sample under the same conditions as described above. The generation of the thermal lens at that time was measured and evaluated as the maximum amount of change in the focal position.

(Measurement method of Verdet constant)
The Verdet constant V was obtained based on the following equation. The magnitude (H) of the magnetic field applied to the sample used was a value calculated by simulation from the dimensions of the measurement system, the residual magnetic flux density (Br), and the holding force (Hc).
θ = V × H × L
(In the equation, θ is the Faraday rotator (rad), V is the Verdet constant (rad / (TM)), H is the magnitude of the magnetic field (T), and L is the length of the Faraday rotator (in this case, 0). .025m).)

(Measurement method of maximum change in focal position by thermal lens)
A high-power laser (beam diameter 1.6 mm) manufactured by IPG Photonics Japan Co., Ltd. emitted a spatially parallel ray with a 100 W output, and the focal position was measured with a beam profiler. Subsequently, a ceramic sample was set on the emitted light beam line, the focal position changed by the sample set was remeasured with a beam profiler, and the difference between the two was obtained as the maximum amount of change in the focal position by the thermal lens.
The above results are summarized in Table 2.

From the above results, in all the example groups (Examples 1 to 11) controlled by the composite oxide composition of the present invention, and Comparative Examples 6 and 9, the linear transmittance was 83.5% or more. Moreover, the extinction ratio was 40 dB or more and the scattering source volume concentration was 3 ppm or less, and it was confirmed that a highly transparent paramagnetic garnet type transparent ceramics sintered body could be produced. Furthermore, the maximum amount of change in the focal position (the amount generated by the thermal lens) due to the thermal lens when a laser beam with an output of 100 W is incident is also suppressed to 0.25 m or less, and it can be mounted on a high-power laser system. It was confirmed. However, in Example 9, since Sc was heavily doped (y = 0.09, z = 0.2 in the formula (1)), the raw material cost increased 1.2 times.
Further, in Comparative Example 6, as a result of the terbium concentration becoming too low (1-xy = 0.499 in the formula (1)), the Verdet constant was less than 30 rad / (Tm).
Further, when Sc is doped in a larger amount as in Comparative Example 9 (y = 0.2, z = 0.4 in the formula (1)), the total replacement ratio combined with Lu becomes too high, and the total substitution ratio becomes too high. As a result, the Verdet constant was less than 30 rad / (TM) because the terbium concentration was low.
Further, Comparative Examples 1, 3 and 4 in which no scandium was added at all (y = 0, z = 0 in the formula (1)) and Comparative Example 2 in which the amount of the scandium added was too small (y = 0 in the formula (1)). , Z = 0.004), the linear transmittance is less than 83.5%, the extinction ratio is less than 40 dB, the scattering source volume concentration is more than 3 ppm, and it depends on the thermal lens when a laser beam with an output of 100 W is incident. The maximum amount of change in the focal position (the amount generated by the thermal lens) was also over 0.25 m, and the optical quality was inferior.
In Comparative Example 5, quite good characteristics were obtained, but the amount of lutetium substitution was slightly insufficient (x = 0.001 in equation (1)), linear transmittance, extinction ratio, scattering source volume concentration, focus by thermal lens. The value of the maximum amount of change in position (the amount of heat lens generated) was inferior to that of the example group. In addition, although good characteristics were obtained to some extent in Comparative Example 7, probably _{because the amount of doping of SiO 2} was large, the linear transmittance, the extinction ratio, the scattering source volume concentration, and the maximum amount of change in the focal position by the thermal lens (thermal lens). The value of) was inferior to that of the example group.
When the compounding ratio of the rare earth site and the aluminum site deviates from the stoichiometric ratio as in Comparative Example 8, the linear transmittance, the extinction ratio, the scattering source volume concentration, and the maximum amount of change in the focal position by the thermal lens (heat). The value of (lens generation amount) was significantly worse than that of the example group.

As described above, based on the results of this embodiment, x, y, and z in the formula (1) are controlled within a predetermined range, and SiO ₂ is doped within a predetermined range as a sintering aid, so that the total length is 25 mm. A thermal lens at the time of laser light incident with a linear transmittance of 83.5% or more at a wavelength of 1064 nm, a Verdet constant of 30 rad / (TM) or more at a wavelength of 1064 nm, and an output of 100 W at a wavelength of 1064 nm at an optical path length of 25 mm. The maximum amount of change in the focal position (the amount generated by the thermal lens) is 0.25 m or less, the extinction ratio is 40 dB or more at a wavelength of 1064 nm as a Faraday rotor, the scattering source volume concentration is 3 ppm or less, and the altitude with little scattering. Can provide transparent normal magnetic garnet type transparent ceramics. Further, when this transparent ceramic is used as a magneto-optical material, it is possible to provide a high-performance magneto-optical device that can be used in high-power applications.

Although the present invention has been described above with the above-described embodiment, the present invention is not limited to this embodiment, and those skilled in the art may think of other embodiments, additions, changes, deletions, and the like. It can be changed within the range possible, and is included in the scope of the present invention as long as the action and effect of the present invention are exhibited in any of the embodiments.

100 Optical Isolator 110 Faraday Rotator 120 Polarizer 130 Detector 140 Magnet

Claims (8)

It is a sintered body of a composite oxide represented by the following formula (1), contains SiO ₂ as a sintering aid in an amount of more than 0% by mass and 0.1% by mass or less, and linearly transmits at a wavelength of 1064 nm at an optical path length of 25 mm. Normal magnetic garnet type transparent ceramics characterized by a rate of 83.5% or more.
(Tb _1-xy Lu _x Sc _y ) ₃ (Al _1-z Sc _z ) ₅ O ₁₂ (1)
(In the formula, 0.05 ≦ x <0.45, 0 <y <0.1, 0.5 <1-x-y <0.95, 0.004 <z <0.2.) The paramagnetic garnet-type transparent ceramic according to claim 1, wherein the Verdet constant at a wavelength of 1064 nm is 30 rad / (Tm) or more. The paramagnetic garnet according to claim 1 or 2, wherein the maximum amount of change in the focal position by the thermal lens when a laser beam having a wavelength of 1064 nm at an optical path length of 25 mm is incident with a beam diameter of 1.6 mm and an incident power of 100 W is 0.25 m or less. Mold transparent ceramics. The paramagnetic garnet-type transparent ceramic according to any one of claims 1 to 3, wherein the Faraday rotator has an extinction ratio of 40 dB or more at a wavelength of 1064 nm at an optical path length of 25 mm. The paramagnetic garnet-type transparent ceramic according to any one of claims 1 to 4, wherein the scattering source volume concentration is 3 ppm or less. A magneto-optical material made of paramagnetic garnet-type transparent ceramics according to any one of claims 1 to 5. A magneto-optical device configured by using the magneto-optical material according to claim 6. A claim that the above-mentioned paramagnetic garnet type transparent ceramics is provided as a Faraday rotator, and a polarizing material is provided before and after the optical axis of the Faraday rotator, which is an optical isolator that can be used in a wavelength band of 0.9 μm or more and 1.1 μm or less. 7. The magneto-optical device according to 7.

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