JP2009269804A - Method for producing oxide ceramic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a dense ceramic by using a metal hydroxide which is inexpensive compared with a metal oxide, as a raw material. <P>SOLUTION: The method for producing metal oxide ceramics comprises a first process S1 to obtain a temporary molding by temporarily molding a raw material powder containing a metal hydroxide as a main component; a second process S2 to obtain a converted oxide by converting the metal hydroxide in the temporary molding into a metal oxide by heating the temporary molding; a third process S3 to obtain a molding by hot forging of the converted oxide at a higher pressure than that in the temporarily molding in the first process; and a fourth process S4 to obtain a sintered compact by sintering the molding. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing oxide ceramics suitably used for optical materials and the like.

Among oxide ceramics, spinel (MgAl ₂ O ₄ ) and magnesia (MgO) have cubic crystal structure and no birefringence. Therefore, by removing pores and segregation of impurities during sintering of ceramic powder, It is possible to obtain a sintered body excellent in translucency.

In particular, MgO has a thermal conductivity of 50 W · m ⁻¹ · K ^−1, which is higher than that of spinel, 18 W · m ⁻¹ · K ⁻¹ , and has excellent heat dissipation. Expected to be an optical element for projectors.

As a report example regarding such a translucent MgO sintered body, there is a method of improving the sinterability by dispersing MgO powder in an organic solvent and re-calcining (for example, see Patent Document 1). As a method for adding the sintering aid, a method of adding a solution-like aluminum compound (see, for example, Patent Document 2), a method of adding SiO ₂ and a small amount of B ₂ O ₃ (for example, see Patent Document 3). ), Scandium oxide, ytterbium oxide, and germanium oxide in an amount of 0.01 to 0.5 wt%, and firing in an inert atmosphere (see, for example, Patent Document 4).

However, since MgO has a very high melting point of 2800 ° C., it is extremely difficult to sinter, and the high cost of the raw material MgO powder is a major factor in increasing the cost. This is a problem common to many oxide ceramics containing Mg—O bonds such as spinel in addition to magnesia.
JP 51-80313 A JP 59-50068 JP 2000-281428 A JP-A-48-2883

As a method for producing oxide ceramics without using expensive oxide powder, there is a method using metal hydroxide powder that is cheaper than metal oxide as a raw material. For example, Mg (OH) ₂ is used as a raw material for producing MgO ceramics, and a mixture of Mg (OH) ₂ and Al (OH) ₃ is used as a raw material for producing spinel (MgAl ₂ O ₄ ) ceramics.

However, the use of metal hydroxide powder causes the following problems. For example, the case of MgO ceramic will be described. The true densities of Mg (OH) ₂ and MgO are 2.37 and 3.59, respectively. Therefore, when a molded body of Mg (OH) ₂ is prepared and sintered, when OH is desorbed from Mg (OH) ₂ at 300 ° C. or higher and converted to MgO, a large volume shrinkage occurs and empty. A hole is formed. Therefore, the porosity of the MgO conversion body is larger than the porosity of the Mg (OH) ₂ compact. That is, the relative density of the MgO conversion body is lower than the relative density of the Mg (OH) ₂ compact. Here, the porosity of the MgO conversion body and the Mg (OH) ₂ compact refers to the volume percentage of pores in the conversion body and the compact, respectively. Moreover, the relative density of the MgO conversion body means the percentage of the apparent density of the MgO conversion body with respect to the true density of MgO. Further, the Mg (OH) relative density of ₂ moldings, refers to the percentage of the apparent density of the Mg (OH) ₂ formed body relative to the true density of Mg (OH) _2.

  When the MgO converter having such a high porosity (that is, having a low relative density) is further heated to the sintering temperature, cracks and cracks are generated due to rapid sintering, and densification itself is unlikely to occur. As a result, vacancies remain.

  An object of the present invention is to solve the above-mentioned problems and to provide a method for producing a dense oxide ceramic using a metal hydroxide that is less expensive than a metal oxide as a raw material.

  The present invention includes a first step of temporarily forming a raw material powder containing a metal hydroxide as a main component to obtain a temporary molded body, and heating the temporary molded body to convert the metal hydroxide in the temporary molded body into a metal oxide. A second step of obtaining an oxide conversion body by converting to a third step, a third step of obtaining a compact by hot forging the oxide conversion body at a pressure higher than the temporary forming pressure in the first step, and a compact And a fourth step of obtaining a sintered body by sintering.

In the method for producing oxide ceramics according to the present invention, the temporary forming pressure in the first step can be 1000 kgf / cm ² or less, and the hot forging pressure in the third step can be 5000 kgf / cm ² or more. Moreover, the heating temperature in a 2nd process can be 300 degreeC or more. Moreover, the die temperature of hot forging in the third step can be set to 300 ° C. or higher.

  The method for producing oxide ceramics according to the present invention may further include a fifth step of obtaining a HIP body by subjecting the sintered body to hot isostatic pressing.

  Moreover, in the manufacturing method of oxide ceramics concerning this invention, oxide ceramics can be used as a spinel. The oxide ceramics can be MgO. The oxide ceramic is a solid solution in which at least one element selected from the group consisting of Fe, Ni, Co, Cu, Mn and Zn as a second component is dissolved in the first component containing MgO as a main component. Can be included as a main component. Here, the ratio of the metal element of the second component to the total amount of the metal elements of the first component and the second component can be 0.3 mol% or more and 5 mol% or less. Further, when the thickness of the oxide ceramic is 1 mm, the linear transmittance of light in the wavelength region of 420 nm to 680 nm can be 85% or more.

  Moreover, this invention is an optical element for color liquid crystal projectors containing the oxide ceramics obtained by said manufacturing method.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of precise | minute oxide ceramics can be provided using a cheap metal hydroxide as a raw material compared with a metal oxide.

<Embodiment 1>
Referring to FIG. 1, one embodiment of a method for producing an oxide ceramic according to the present invention includes a first step S1 for temporarily forming a raw material powder containing a metal hydroxide as a main component to obtain a temporary molded body, Heating the temporary molded body, converting the metal hydroxide in the temporary molded body to a metal oxide to obtain an oxide converted body, and a pressure higher than the temporary molding pressure in the first step, A third step S3 for obtaining a compact by hot forging the oxide conversion body, and a fourth step S4 for obtaining a sintered compact by sintering the compact.

(First step)
With reference to FIG. 1, the manufacturing method of the oxide ceramics of this embodiment is a 1st process S1. The process (temporary molding) which pre-forms the raw material powder which contains a metal hydroxide as a main component, and forms it. Step). When a raw material powder containing a metal hydroxide as a main component is molded and sintered at once, voids are generated in the sintered body due to volume shrinkage when the metal hydroxide is converted into a metal oxide, and its relative density As a result, a dense oxide ceramic cannot be obtained. In order to solve such a problem, after providing a step of obtaining a temporary formed body by temporarily forming a raw material powder containing a metal hydroxide as a main component as the first step, metal hydroxide in the temporary formed body is provided as a second step. The product was converted to a metal oxide to obtain an oxide conversion product.

  Here, the raw material powder containing a metal hydroxide as a main component means, for example, a raw material powder containing a metal hydroxide at 50 wt% or more, preferably 90 wt% or more, more preferably 99 wt% or more.

Further, the pressure during temporary molding (hereinafter referred to as temporary molding pressure) is not particularly limited as long as the temporary molded body maintains its shape, but it is preferably as small as possible. As the temporary molding pressure increases, the relative density of the temporary molded body increases, and a large pressure is required in the subsequent hot forging, and cracks and cracks are likely to occur. Specifically, the provisional molding pressure is preferably 1000kgf / cm ² (98MPa) hereinafter, 100kgf / cm ² (9.8MPa) or less is more preferable. Further, the temperature at which the temporary molding is performed (hereinafter referred to as the temporary molding temperature) is not particularly limited, and is preferably room temperature (for example, 5 ° C. to 35 ° C.) from the viewpoint of cost reduction.

(Second step)
With reference to FIG. 1, the manufacturing method of the oxide ceramics of this embodiment heats a temporary molded object as 2nd process S2, and converts the metal hydroxide in a temporary molded object into a metal oxide. A step of obtaining an oxide conversion body (conversion step) is provided. By performing the second step (conversion step) after the first step (temporary forming step), a dense oxide ceramic can be easily obtained without generating cracks or cracks.

  The heating temperature in the second step is not particularly limited as long as it is equal to or higher than the temperature at which the metal hydroxide is converted into the metal oxide. Thermodynamically, the metal hydroxide is converted to a metal oxide at 300 ° C. or higher. The apparatus for heating in the second step is not particularly limited, and a normal atmospheric heating furnace can be used. A temporary molded body in which a metal hydroxide powder is temporarily molded is inserted into a heating furnace and held at a predetermined temperature. The holding time may be short as long as the entire temporary molded body reaches the holding temperature uniformly. When the entire temporary molded body reaches the holding temperature uniformly, the metal hydroxide in the temporary molded body is converted into an oxide. Since the oxide converter after the conversion step is taken out of the heating furnace and placed in a die for performing the next hot forging, the oxide converter is slightly cooled, so the temperature of the oxide converter The heating temperature is preferably 400 ° C. or higher from the viewpoint of securing the temperature of 300 ° C. or higher.

(Third step)
With reference to FIG. 1, the manufacturing method of the oxide ceramics of this embodiment WHEREIN: As a 3rd process S3, the oxide conversion body is hot-forged by the pressure higher than the temporary forming pressure in a 1st process, and a molded object The process (hot forging process) of obtaining is provided. By performing the third step (hot forging step) after the second step (conversion step), a dense molded body can be easily obtained without generating cracks or cracks.

Here, hot forging means that the material is heated to a temperature higher than the recrystallization temperature and is deformed by applying pressure with a mold or the like. Further, the higher the pressure during hot forging (hereinafter, referred to as hot forging pressure), the more preferable a dense molded body is obtained. Specifically, the hot forging pressure is preferably 5000 kgf / cm ² (490 MPa) or more. On the other hand, when the hot forging pressure exceeds 9000 kgf / cm ² (833 MPa), the increase in the relative density of the compact reaches a peak. Further, the higher the mold temperature during hot forging, the more preferable the ceramic temporary molded body is likely to be deformed. Specifically, the mold temperature is preferably 300 ° C. or higher.

(4th process)
With reference to FIG. 1, the manufacturing method of the oxide ceramic of this embodiment is equipped with the process (sintering process) of sintering a molded object and obtaining a sintered compact as 4th process S4. By performing the fourth step (sintering step) after the third step (hot forging step), a dense molded body can be easily obtained without generating cracks or cracks.

  Here, the sintering method in the fourth step is not particularly limited, and a conventional method can be applied. The temperature during sintering (hereinafter referred to as sintering temperature) and the pressure during sintering (hereinafter referred to as sintering pressure) vary depending on the type of oxide ceramics to be produced.

(Oxide ceramics)
Although there is no restriction | limiting in particular in oxide ceramics, the thing containing MgO is preferable from a viewpoint of improving thermal conductivity. The oxide ceramic is preferably, for example, single phase MgO, spinel. Here, in order to produce spinel as an oxide ceramic, a mixture of Mg (OH) ₂ and Al (OH) ₃ is preferably used as the metal hydroxide of the raw material powder. In order to produce single-phase MgO as the oxide ceramic, Mg (OH) ₂ is preferably used as the metal hydroxide of the raw material powder.

  From the viewpoint of improving the water resistance of the oxide ceramic, the oxide ceramic is selected from the group consisting of Fe, Ni, Co, Cu, Mn and Zn as the second component in the first component containing MgO as the main component. It is preferable to contain as a main component a solid solution in which at least one kind of element is dissolved.

For example, MgO is a ceramic that is very easy to react with moisture, and not only reacts with moisture in the air to form Mg (OH) ₂ to devitrify, but also eventually collapses. When such MgO is used as an optical material, the surface devitrifies over time. This phenomenon is particularly remarkable in the sintered body of MgO.

  On the other hand, the main component is a solid solution in which at least one element selected from the group consisting of Fe, Ni, Co, Cu, Mn, and Zn is dissolved in the first component containing MgO as a main component. The oxide ceramic used as a component is a material that is chemically stable even in the long term because the surface activity of MgO, which is the main component of the first component, is reduced and the reaction with moisture is suppressed.

Here, in order to manufacture oxide ceramics containing as a main component a solid solution in which the second component is dissolved in the first component, Mg (OH) ₂ , Fe (OH) ₂ , Ni (OH) _{2 are used.} A mixture with at least one metal hydroxide selected from the group consisting of Co (OH) ₂ , Cu (OH) ₂ , Mn (OH) ₂ and Zn (OH) ₂ is preferably used.

  Here, the first component containing MgO as a main component refers to a component containing 50 wt% or more, preferably 90 wt% or more, more preferably 99 wt% or more of MgO. The oxide ceramic containing as a main component a solid solution in which the second component is dissolved in the first component is an oxide containing 50 wt% or more, preferably 90 wt% or more, more preferably 99 wt% or more of the solid solution. Ceramics.

  In the solid solution, the ratio of the metal element of the second component to the total amount of the metal elements of the first component and the second component is not particularly limited as long as a solid solution is obtained, but is 0.3 mol% or more and 5 mol%. The following is preferred. If the ratio of the metal element of the second component to the total amount of the metal elements of the first component and the second component is less than 0.3 mol%, the moisture resistance of the oxide ceramic is not high, and if it is greater than 5 mol%, the oxide ceramics Thermal conductivity is greatly reduced.

  Further, when the thickness of the oxide ceramic is 1 mm, the oxide ceramic can have excellent translucency such that the linear transmittance of light in the wavelength region of 420 to 680 nm is 85% or more. The linear transmittance is more preferably 87% or more.

  On the other hand, the upper limit of the linear transmittance is calculated from the refractive index of oxide ceramics (for example, the refractive index of spinel is 1.67 to 1.71, the refractive index of MgO is 1.75, etc.). Here, the linear transmittance indicates the transmittance of light in the direction perpendicular to the surface of the oxide ceramic having a thickness of 1 mm (that is, the depth direction of the thickness). Such linear transmittance can be measured with a spectrophotometer.

<Embodiment 2>
Referring to FIG. 1, in another embodiment of the method for producing oxide ceramics according to the present invention, the sintered body obtained in the fourth step S <b> 4 of Embodiment 1 is subjected to hot isostatic pressing and HIP. A fifth step S5 for obtaining a body is further provided.

(5th process)
With reference to FIG. 1, the manufacturing method of the oxide ceramics of this embodiment is equipped with the process (HIP processing process) of obtaining a HIP body by carrying out the hot isostatic pressing process of a sintered compact as 5th process S5. . By performing the fifth step (HIP treatment step) after the fourth step (sintering step), a denser molded body can be obtained without generating cracks or cracks.

  In this HIP treatment step, the pressure medium is not particularly limited, but it is preferable to use an industrially available inert gas. The HIP processing temperature is preferably about 1200 ° C. or higher. When the temperature is lower than 1200 ° C., vacancies cannot be completely removed, and when the sintering temperature is exceeded, grain growth proceeds and residual vacancies tend to occur. For this reason, it is preferable that the upper limit of the HIP processing temperature does not exceed the sintering temperature. On the other hand, the HIP treatment pressure is preferably 500 atm (50.7 MPa) or more and 2000 atm (202.7 MPa) or less. If the pressure is less than 500 atm (50.7 MPa), a sufficient effect cannot be obtained, and even if it exceeds 2000 atm (202.7 MPa), the translucency is not further improved, and the apparatus becomes large. Therefore, it is not preferable. Further, it is sufficient that the HIP treatment time is 0.5 hours or longer, for example, 0.5 hours or longer and 2 hours or shorter, and various times may be changed depending on the thickness of the obtained MgO ceramics. Such HIP processing time varies depending on the holding time at the maximum temperature.

<Embodiment 3>
An optical element for a color liquid crystal projector according to the present invention includes an oxide ceramic obtained by the manufacturing method of any one of the first and second embodiments. Since the oxide ceramics (sintered body or HIP body) obtained by the manufacturing method of any of Embodiments 1 and 2 above has high translucency, heat resistance, water resistance and thermal conductivity and is not birefringent, it is usually It satisfies the physical properties required for this optical lens, and is particularly preferably used as an optical element for a color liquid crystal projector. Here, as a physical property required for an optical element for a color liquid crystal projector, for example, an oxide ceramic used as an optical element has a thickness of 1 mm, and linearly transmits light in a wavelength region of 420 nm to 680 nm. The rate is 85% or more.

<Example 1>
(A) Raw material powder All the raw material powders used had a purity of 99.99 wt% or more. Referring to Table 1, Mg (OH) ₂ powder having an average particle size of 0.3 μm was used as a raw material powder for MgO ceramics (Sample Nos. ₂ to 7). For comparison, MgO powder having an average particle size of 0.3 μm was used (Sample No. 1). Moreover, as the raw material powder of the solid solution ceramics in which the second component is dissolved in MgO as the first component, Mg (OH) ₂ powder having an average particle size of 0.3 μm is used as the first component powder raw material. As raw materials, Zn (OH) ₂ , Cu (OH) ₂ or Ni (OH) ₂ powder having an average particle size of 0.5 μm was used (Sample Nos. 8 to 11). Further, Mg (OH) ₂ powder having an average particle size of 0.3 μm and Al (OH) ₃ powder having an average particle size of 0.2 μm were used as raw material powders for spinel ceramics (Sample Nos. 13 and 14). For comparison, MgO powder having an average particle size of 0.3 μm and Al ₂ O ₃ powder having an average particle size of 0.2 μm were used (Sample No. 12).

(B) Temporary molding step (first step)
Sample No. About 1-14, 5 wt% of PVB-BL1 made by Sekisui Chemical was added as a binder to the raw material powder shown in Table 1, ethanol was added, and the mixture was collected for 24 hours using a nylon pot and a nylon ball, and then collected. The recovered raw material powder was loaded into a temporary mold and pressed at the pressure shown in Table 1 to obtain a disk-shaped temporary molded body having a diameter of 35 mm and a thickness of 10 mm. The relative density of the obtained temporary molded body (percentage of the apparent density of the temporary molded body with respect to the true density of the material) was measured by the Archimedes method. The results are summarized in Table 1.

(C) Conversion step (second step)
Next, sample no. About 3-11 and 14, the temporary molded body obtained by the said temporary molding process is heated to the temperature shown in Table 1 within a tubular atmospheric furnace, and it hold | maintains for 15 minutes at the temperature (heating temperature), and oxide conversion body Got. Sample No. For 1, 2, 12, and 13, this conversion step was not performed.

(D) Hot forging process (third process)
Next, sample no. About 3-11 and 14, the oxide conversion body obtained by the said conversion process was loaded in the metal mold | die of 36-mm internal diameter of a 100-ton hot forging apparatus, and it heated by the metal mold | die temperature and hot forging pressure which are shown in Table 1. Forging was performed to obtain a disk-shaped molded body having a diameter of 36 mm. Sample No. For 1, 2, 12, and 13, this hot forging process was not performed.

(E) Sintering process (4th process)
Next, sample no. For 3 to 11 and 14, the molded body obtained in the above-mentioned hot forging process, and for sample Nos. 1, 2, 12 and 13, the temporary molded body obtained in the above-mentioned temporary molding process are loaded into the sintering furnace. Then, the sintered body was obtained by sintering at a temperature (sintering temperature) shown in Table 1 for 15 hours in an air atmosphere and at atmospheric pressure. The relative density (percentage of the apparent density of the sintered body with respect to the true density of the sintered body material) of the obtained sintered body was measured by Archimedes method. Moreover, the formation phase of the sintered body was confirmed by powder X-ray diffraction. The results are summarized in Table 1. Here, “MgO” in the generated phase column of Table 1 indicates that the generated phase is MgO or a polycrystalline phase of a solid solution in which the second component is dissolved in MgO, and “spinel” means that the generated phase is spinel ( It shows that it is a polycrystalline phase of MgAl ₂ O ₄ ). Further, the true density of the sintered body powder is measured with a pycnometer, and the first component metal with respect to the total amount of the first and second component metal elements in the sintered body powder is determined from the true density value of the sintered body material. As a result of calculating the ratio (mol%) of the element and the metal element of the second component, they are respectively in the powder of the first component with respect to the total amount of the metal element in the powder of the first component (MgO) and the powder of the second component. It was the same as the ratio (mol%) of the metal element and the metal element in the powder of the second component.

(F) HIP processing step (fifth step)
Next, sample no. About 1-14, each sintered compact obtained at the said sintering process was heated up to the temperature (HIP processing temperature) shown in Table 1 by 800 degreeC / hr in Ar gas, and the pressure of 1000 atmospheres (101.3 MPa) The HIP body was obtained by holding for 1 hour and performing HIP (hot isostatic pressing). The relative density of the obtained HIP body (percentage of the apparent density of the HIP body with respect to the true density of the HIP body material) was measured by the Archimedes method. The results are summarized in Table 1. In Table 1, sample No. 3 to 11 and 14 are examples of the present invention. 1, 2, 12 and 13 are comparative examples.

(G) Evaluation (g-1) Linear transmittance The oxide ceramic (HIP body) obtained above is processed into a thickness of 1 mm, mirror-polished with diamond slurry, and used as a spectrophotometer. The linear transmittance (thickness 1 mm) was measured. Here, the linear transmittance of light in the wavelength region of 420 nm to 680 nm is lowest for light having a wavelength of 420 nm. For this reason, the linear transmittance of light having a wavelength of 420 nm was measured in the samples of the examples and comparative examples. The results are summarized in the column of “Linear transmittance (%)” in Table 1.

(G-2) Water resistance Water resistance was evaluated by conducting a water resistance acceleration test of the oxide ceramics (HIP body) obtained above. That is, each oxide ceramic was pulverized with a planetary ball mill at a crushing acceleration of 150 G for 10 minutes to form a powder until the BET specific surface area value was about 0.3 m ² / g, and this was immersed in boiling water at 98 ° C. for 5 hours. The weight increase ratio after immersion was measured by immersion. It shows that it is inferior to water resistance, so that a weight increase becomes large. The results are summarized in the column of “weight increase rate during water resistance test (wt%)” in Table 1.

(G-3) Thermal conductivity A test piece having a diameter of 10 mm and a thickness of 2 mm was cut out from the oxide ceramic (HIP body) obtained above, and the thermal conductivity at room temperature (for example, 25 ° C.) was measured by a laser flash method. did. The results are summarized in the column of “thermal conductivity (W · m ⁻¹ · K ⁻¹ )” in Table 1.

  As is apparent from Table 1, the first step of temporarily forming a raw material powder containing a metal hydroxide as a main component to obtain a temporary molded body, and heating the temporary molded body to metal hydroxide in the temporary molded body A second step of obtaining an oxide converter by converting the product into a metal oxide, and a third step of obtaining a compact by hot forging the oxide converter at a pressure higher than the temporary forming pressure in the first step. And a fourth step of sintering the compact to obtain a sintered body, an oxide ceramic having high relative density, linear light transmittance, and high water resistance was obtained.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a flowchart which shows the manufacturing method of the oxide ceramics concerning this invention.

Explanation of symbols

  S1 1st process, S2 2nd process, S3 3rd process, S4 4th process, S5 5th process.

Claims (11)

A first step of temporarily forming a raw material powder containing a metal hydroxide as a main component to obtain a temporary molded body;
A second step of heating the temporary molded body to convert the metal hydroxide in the temporary molded body into a metal oxide to obtain an oxide converted body;
A third step of obtaining a molded body by hot forging the oxide conversion body at a pressure higher than the temporary forming pressure in the first step;
And a fourth step of obtaining the sintered body by sintering the shaped body. The method for producing oxide ceramics according to claim 1, wherein the temporary forming pressure in the first step is 1000 kgf / cm ² or less, and the hot forging pressure in the third step is 5000 kgf / cm ² or more.   The method for producing an oxide ceramic according to claim 1 or 2, wherein the heating temperature in the second step is 300 ° C or higher.   The method for producing an oxide ceramic according to any one of claims 1 to 3, wherein a mold temperature of hot forging in the third step is 300 ° C or higher.   The manufacturing method of the oxide ceramics in any one of Claims 1-4 further equipped with the 5th process of obtaining the HIP body by carrying out the hot isostatic pressing process of the said sintered compact.   The said oxide ceramics is a spinel, The manufacturing method of the oxide ceramics in any one of Claims 1-5.   The method for producing an oxide ceramic according to any one of claims 1 to 5, wherein the oxide ceramic is MgO.   The oxide ceramics comprises a solid solution in which at least one element selected from the group consisting of Fe, Ni, Co, Cu, Mn and Zn as a second component is dissolved in a first component containing MgO as a main component. The manufacturing method of the oxide ceramics in any one of Claims 1-5 included as a main component.   The oxidation according to any one of claims 1 to 8, wherein a ratio of the metal element of the second component to a total amount of the metal elements of the first component and the second component is 0.3 mol% or more and 5 mol% or less. Of manufacturing ceramics.   The oxide ceramic according to any one of claims 7 to 9, wherein the oxide ceramic has a linear transmittance of 85% or more for light in a wavelength region of 420 nm to 680 nm when the thickness is 1 mm. Manufacturing method.   The optical element for color liquid crystal projectors containing the said oxide ceramics obtained by the manufacturing method in any one of Claims 1-10.

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