Ceramic material, optical member, head mounted display, and manufacturing method

Abstract

In the present invention, visible light is appropriately refracted and transmitted. A ceramic material (10) contains, as a primary component, a compound having a perovskite structure represented by the chemical formula A(B1v,B21-v)Ow, wherein A is one or more elements selected from among Ba, Sr, Ca, K, Na, La, Gd and Yb, B1 is one or more elements selected from among Ti and Hf, and B2 is one or more elements selected from among Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca and Al. The perovskite structure does not contain Mg, Zn, Y or In. v is a positive number that is less than 1. w is a numerical value that enables the overall chemical formula to have a neutral charge.

Description

Ceramic material, optical member, head-mounted display, and manufacturing method

[0001] The present invention relates to a ceramic material, an optical member, a head-mounted display, and a manufacturing method thereof.

[0002] In recent years, there has been a demand for materials with high refractive indexes and high transmittances. In particular, as shown in Patent Document 1, for example, in wearable devices such as head-mounted displays that realize AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc., light guide plates are required to have high refractive indexes and high transmittance for visible light. Furthermore, Patent Document 2 describes a translucent ceramic whose main component is a perovskite compound.

[0003] International Publication No. 2022 / 234782 Patent No. 4747892

[0004] However, there is room for improvement in terms of transmitting visible light while still appropriately refracting it.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a ceramic material, an optical element, a head-mounted display, and a manufacturing method that can transmit visible light while appropriately refracting the visible light.

[0006] The ceramic material according to the present disclosure is A (B1 ｖ , B2 １－ｖ ) O ｗ wherein A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb, B1 is at least one selected from Ti and Hf, and B2 is at least one selected from Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca, and Al; the perovskite structure does not contain Mg, Zn, Y, or In; v is a positive number less than 1; and w is a value that satisfies charge neutrality of the entire chemical formula.

[0007] The ceramic material according to the present disclosure is A (B1 ｖ , B3 １－ｖ ) Oｗ wherein A is at least one selected from Ba, Sr, Ca, La, K, Na, Gd, and Yb, B1 is at least one selected from Ti, Hf, Ge, and Zr, and B3 is at least one selected from Sc, Y, Zn, Yb, and Al, the perovskite structure does not contain Ta or Nb, v is a positive number less than 1, and w is a value that satisfies charge neutrality of the entire chemical formula.

[0008] The ceramic material according to the present disclosure is A (Ti ｘ , B5 ｖ , B4 １－ｖ－ｘ ) O ｗ wherein A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb, B5 is at least one selected from Hf, Ge, and Zr, and B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn, x is 0.7 or more and 1.0 or less, v is 0 or more and 0.3 or less, and x+v≦1.0 and w are values ​​that satisfy charge neutrality of the entire chemical formula, and the converted internal transmittance for light with a wavelength of 635 nm at a thickness of 1 mm is 5% or more.

[0009] The ceramic material according to the present disclosure is A0 (B1 ｖ , B4 １－ｖ ) O ｗ The main component is a compound having a perovskite structure represented by the chemical formula: wherein A0 contains Sr and at least one of K, Na, La, Gd, and Yb; B1 is at least one selected from Ti, Hf, Ge, and Zr; B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn; v is a positive number less than 1; and w is a numerical value that satisfies charge neutrality of the entire chemical formula.

[0010] The optical member according to the present disclosure uses the ceramic material as a light guide plate.

[0011] The head mounted display according to the present disclosure uses the ceramic material as a light guide plate member.

[0012] In the manufacturing method according to the present disclosure, the ceramic material is manufactured by powder compaction or slip casting.

[0013] In the manufacturing method according to the present disclosure, a transparent ceramic body having a refractive index of 2.30 or more at a wavelength of 635 nm is manufactured by powder compact molding or slip casting.

[0014] According to the present invention, visible light can be transmitted while being appropriately refracted.

[0015] FIG. 1 is a schematic diagram of a ceramic material according to this embodiment.

[0016] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes configurations that are made by combining the respective embodiments. Furthermore, numerical values ​​include the range of rounding.

[0017] (First Embodiment) (Ceramic Material) FIG. 1 is a schematic diagram of a ceramic material according to this embodiment. The ceramic material 10 according to this embodiment is a translucent member capable of transmitting visible light. The ceramic material 10 is preferably a polycrystalline ceramic, and it can also be said that a polycrystalline ceramic sintered body is preferable. As shown in FIG. 1, the ceramic material 10 according to this embodiment is a plate-shaped member, but the shape of the ceramic material 10 is not limited to a plate shape and may be any shape. In this embodiment, the ceramic material 10 is used as an optical element. More specifically, in this embodiment, the ceramic material 10 is used as a light guide plate. That is, in this embodiment, an optical member using the ceramic material 10 as a light guide plate can be provided. Examples of the optical member here include display devices. More specifically, the ceramic material 10 is used as a light guide plate for a head-mounted display. A head-mounted display is a display device (wearable device) worn on a person's head. However, the ceramic material 10 may be used for any purpose, and is not limited to being used as a light guide plate or a head-mounted display. For example, possible uses of the ceramic material 10 include a base substrate for crystal growth, a transparent substrate for a capacitance sensor for remote sensing, a low-voltage driven electrostatic induction panel substrate, an optical lens, jewelry and furnishings, a cover for a mobile terminal or wearable device, an interior or non-contact panel cover for a passenger vehicle, a dielectric antenna, a window material for generating surface microwave plasma, and a substrate for a digital microchannel for droplet control.

[0018] (Main Component) The ceramic material 10 contains a compound (oxide) having a perovskite structure as a main component. The ceramic material 10 of the first embodiment contains A (B1 ｖ , B2 １－ｖ ) O ｗThe ceramic material 10 includes a compound having a perovskite structure represented by the chemical formula: In other words, the compound serving as the main component can be said to be an oxide in which element A is located at the A site in the perovskite structure, element B1 or element B2 is located at the B site in the perovskite structure, and O is located at the O site in the perovskite structure. The main component here may refer to a content of the main component relative to the entire ceramic material 10 exceeding 50% by mass. The content of the main component in the ceramic material 10 is preferably 90% to 100% by mass, more preferably 95% to 100% by mass, relative to the entire ceramic material 10. The content of the main component can be evaluated by quantitative analysis using powder X-ray analysis.

[0019] (Element A) A(B1 ｖ , B2 １－ｖ ) O ｗ In the formula (1), A is an element located at the A site in the perovskite structure. In the first embodiment, the element A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb. That is, the element A may contain two or more elements selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb, or may contain only one element selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb. When the element A contains two or more elements, one of these elements is located at the A site in the perovskite structure, and the same applies to the following description of the B site.

[0020] Element A preferably contains Sr, and more preferably contains only Sr. However, element A may contain Sr and one or more of Ba, Ca, K, Na, La, Yb, and Gd. When element A contains Sr and other elements (one or more of Ba, Ca, K, Na, La, and Gd), the content of Sr relative to the total content of element A is preferably 5% to 100% in molar ratio, more preferably 25% to 100% in molar ratio, more preferably 50% to 100% in molar ratio, and even more preferably 75% to 100% in molar ratio. By keeping the Sr content within this range, high refractive index and high transmittance for visible light can be appropriately ensured. The Sr content can be measured by X-ray fluorescence analysis (XRF). Unless otherwise specified, the measurement method for the contents (contents in molar ratio) of other elements described below may be the same.

[0021] (Element B1) A(B1 ｖ , B2 １－ｖ ) O ｗ In the formula (1), B1 is an element located at the B site in the perovskite structure. In the first embodiment, the element B1 is at least one element selected from Ti and Hf. That is, the element B1 may contain both Ti and Hf, or may contain only one element of Ti and Hf.

[0022] The element B1 preferably contains Ti, and more preferably consists of only Ti. However, the element B1 may contain Hf and Ti. When the element B1 contains Ti and Hf, the content of Ti relative to the total amount of the element B1 is preferably more than 70% and 100% or less, more preferably 80% or more and 100% or less, and even more preferably 90% or more and 100% or less, in molar ratio. By setting the content of Ti within this range, a high refractive index and high transmittance for visible light can be appropriately ensured.

[0023] (Element B2) A(B1 ｖ , B2 １－ｖ ) O ｗIn the formula, B2 is an element located at the B site in the perovskite structure. In the first embodiment, the element B2 is at least one selected from Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca, and Al. That is, the element B2 may contain two or more elements selected from Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca, and Al, or may contain only one element selected from Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca, and Al. The element B2 is preferably at least one selected from Zr, Ge, Gd, and Yb, and more preferably at least one selected from Zr and Yb.

[0024] In this embodiment, element B2 is substituted for element B1 in part of the B site. This allows high transmittance to be appropriately ensured while maintaining a high refractive index. That is, for example, if element B1 contains Ti, a high refractive index can be achieved by Ti, but Ti is easily reduced during sintering, and the reduction can cause coloration, which can reduce transmittance. Furthermore, for example, if element A contains Sr, defects can occur during sintering, which can reduce transmittance. In contrast, by substituting element B2 in part of the B site, the reduction in transmittance can be suppressed, and a high refractive index and high transmittance can be ensured.

[0025] (Number v) A (B1 ｖ , B2 １－ｖ ) O ｗ In the formula, v is a numerical value indicating the ratio (molar ratio) between the content of element B1 and the content of element B2, and more specifically, the molar ratio of the content of element B1 to the total content of element B1 and element B2. That is, for example, when element B1 is only Ti, the numerical value v can be said to be the molar ratio of the content of Ti to the total content of Ti and element B2. Furthermore, when element B1 contains multiple elements, the content of element B1 refers to the total content of these multiple elements, and the same applies to the contents of other elements (element B2 and other elements described below).

[0026] The numerical value v is a positive number less than 1. The numerical value v is preferably set so that the average valence of the elements B1 and B2 is 4. In other words, the average valence of the elements B1 and B2 is determined based on the types of the elements B1 and B2 and the numerical value v. Therefore, it can be said that the types of the elements B1 and B2 and the numerical value v are preferably set so that the average valence of the elements B1 and B2 is 4.

[0027] The value v is preferably 0.7 or more and less than 1.0, more preferably 0.8 or more and less than 1.0, and even more preferably 0.9 or more and less than 1.0. When the value v is in this range, the ratio of element B1 to element B2 can be made appropriate, and a high refractive index and high transmittance for visible light can be appropriately ensured.

[0028] Whether or not a specific element is contained in a perovskite crystal can be analyzed by techniques such as peak shift of diffraction lines in X-ray diffraction (XRD), structural analysis such as the Rietveld method, or X-ray absorption fine structure (EXAFS) analysis.

[0029] (Number w) A (B1 ｖ , B2 １－ｖ ) O ｗ In the formula (A(B1), w is a numerical value indicating the content (molar ratio) of O, more specifically, the molar ratio of the content of O to the total content of element A, element B1, element B2, and O. ｖ , B2 １－ｖ ) O ｗ ) is a value at which overall charge neutrality is achieved, and may be, for example, 3.

[0030] (Non-contained elements) The ceramic material 10 according to the first embodiment does not contain Mg, Zn, Y, or In in the perovskite structure (the compound having the perovskite structure as the main component). ｖ , B2 １－ｖ ) O ｗThe compound represented by the formula (I) does not contain any of Mg, Zn, Y, or In at the A site, B site, or O site. This ensures a high refractive index and high transmittance while suppressing the structural complexity caused by an excessive number of substitution elements. Note that the ceramic material 10 may contain Mg, Zn, Y, and In in portions other than the perovskite structure, or may contain Mg, Zn, Y, and In as inevitable impurities.

[0031] (Preferable examples of main components) A (B1 ｖ , B2 １－ｖ ) O ｗ Preferred examples of the compound represented by the formula are Sr(Ti ｖ , Ta １－ｖ ) O ｗ , Sr(Ti ｖ , Nb １－ｖ ) O ｗ , Sr(Ti ｖ , Al １－ｖ ) O ｗ Examples include:

[0032] (Minor Component) The ceramic material 10 preferably contains a minor component other than the main components listed above. The ceramic material 10 preferably contains at least one minor component selected from Li, Si, B, and Mg, and more preferably contains Si. This minor component is derived from a sintering aid used when sintering the raw materials to produce the ceramic material 10. The ceramic material 10 may contain the minor component in the form of an oxide of the above-listed element. The content of this minor component is preferably 50 ppm to 50,000 ppm, more preferably 50 ppm to 20,000 ppm, and even more preferably 50 ppm to 5,000 ppm, by mass relative to the entire ceramic material 10. By setting the content of the minor component within this range, a ceramic material 10 with a high refractive index and high transmittance can be appropriately produced. The content of the minor component can also be measured by X-ray fluorescence analysis (XRF).

[0033] The ceramic material 10 may also contain auxiliary components other than those derived from the sintering aid. If the auxiliary components other than those derived from the sintering aid are referred to as auxiliary components, the ceramic material 10 preferably contains at least one selected from Ce and Pr as the auxiliary component. By including such an auxiliary component, the auxiliary component functions as an oxidizer, appropriately receiving electrons and more effectively suppressing a decrease in transmittance. The ceramic material 10 may also contain the auxiliary component in the form of an oxide of the above-listed element. The content of the auxiliary component is preferably 50 ppm to 50,000 ppm, more preferably 50 ppm to 20,000 ppm, and even more preferably 50 ppm to 5,000 ppm, by mass relative to the entire ceramic material 10. By setting the content of the auxiliary component within this range, a ceramic material 10 with a high refractive index and high transmittance can be appropriately produced. The content of the auxiliary component can also be measured by X-ray fluorescence spectroscopy (XRF).

[0034] In addition to the above-described main component, subcomponent, and auxiliary component, the ceramic material 10 may contain any component as an inevitable impurity. It is preferable that the ceramic material 10 does not contain any component other than the main component, subcomponent, and auxiliary component, except for the inevitable impurities.

[0035] (Characteristics of Ceramic Material) Next, the characteristics of the ceramic material 10 will be described.

[0036] (Refractive Index) The refractive index of the ceramic material 10 for light with a wavelength of 635 nm is preferably 2.25 or more and 2.45 or less, more preferably 2.30 or more, even more preferably 2.30 or more and 2.45 or less, and even more preferably 2.35 or more and 2.45 or less. A refractive index within this range allows for appropriate refracting of visible light. The refractive index can be measured by spectroscopic ellipsometry (JA Woollam Co., Inc.; M-2000 DI).

[0037] (Transmittance) The ceramic material 10 preferably has an equivalent internal transmittance per 1 mm thickness for light with a wavelength of 635 nm of 5% or more, preferably 10% or more, preferably 15% or more, more preferably 20% or more, more preferably 30% or more, more preferably 40% or more, more preferably 50% or more, more preferably 60% or more, and even more preferably 80% or more. The equivalent internal transmittance here refers to the internal transmittance per unit thickness of the ceramic material 10, and is the value obtained by dividing the measured internal transmittance (%) by the thickness (mm) of the ceramic material 10 being measured. Having an internal transmittance within this range ensures appropriate transmission of visible light. The internal transmittance can be calculated using the following procedure using the measured values ​​T1 and reflectance R of the external transmittance of two different plate thicknesses. The external transmittance refers to the transmittance including surface reflection loss. The equivalent internal transmittance can be calculated as follows. When the refractive index at 635 nm is n, the formula (n-1) is used: ２ / (n+1) ２ The reflectance at the incident surface is calculated from the above equation, and the theoretical transmittance T0 is calculated by subtracting twice the reflectance from 1, and T2 = T1 / T0 is the internal transmittance. The apparent absorption coefficient α (cm －１) can be calculated. The apparent absorption coefficient can be evaluated as the converted internal transmittance T3 (%) per 1 mm thickness by multiplying it by 0.1 (cm), taking the negative sign, and exponent with e as the base. The external transmittance can be measured using a spectrophotometer (U-4100 manufactured by Hitachi High-Technologies Corporation) for a sample that has been mirror-polished on both sides to a thickness of 0.5 mm to 10 mm. Alternatively, the converted internal transmittance may be evaluated using the following method. A laser light source with a spot diameter of 2 mm and a wavelength of 635 nm is incident perpendicularly on the polished surface of a mirror-polished ceramic parallel plate, and a Si photodetector is installed 20 cm from the side of the sample facing the light source. Using the transmittance T1', the ratio of the light intensity received by the Si photodetector to the output of the incident light source is used to take the natural logarithm of T2' = T1' / T0, taking the negative sign, and dividing by the sample thickness (unit: cm) to obtain the apparent absorption coefficient α' (cm －１ ) can be calculated. The apparent absorption coefficient is multiplied by 0.1 (cm), negatively signed, and the exponent with base e is used to calculate the converted internal transmittance T3' per 1 mm thickness, which can be evaluated as the converted internal transmittance. The polished surface of the sample is sufficiently large relative to the laser spot diameter, typically about 1 cm. The converted internal transmittance is determined by the composition of the ceramic material 10, but even with the same composition, it may vary depending on the production process of the ceramic material 10. Therefore, for example, the converted internal transmittance can be adjusted to the above range by appropriately adjusting the production process of the ceramic material 10. The production process can be adjusted using known methods, such as carefully mixing the raw materials. For example, the converted internal transmittance can be appropriately adjusted to the above range by adjusting the ratio of the total content of K, Na, La, Yb, and Gd in element A to the total content of element A, for example, to 0.05% or more and 10% or less in molar ratio.

[0038] (Fracture toughness value) Fracture toughness value K of ceramic material 10 ＩＣ is 1.0 MPa m ０．５ More preferably, 1.05 MPa m ０．５ 2.5MPa・m or more ０．５ More preferably, 1.05 MPa m ０．５2.2 MPa・m or more ０．５ More preferably, 1.05 MPa m ０．５ 2.00MPa・m or more ０．５ More preferably, 1.05 MPa m ０．５ Over 1.9 MPa m ０．５ More preferably, 1.05 MPa m ０．５ 1.80MPa・m or more ０．５ The following is more preferable: Fracture toughness value K ＩＣ When the fracture toughness value K is in this range, the ceramic material 10 can be prevented from being broken. ＩＣ This can be carried out, for example, by the IF method or the SEPB method conforming to JIS R1607.

[0039] Single crystal SrTiO ３ Fracture toughness value K ＩＣ The fracture toughness value K of the ceramic material 10 ＩＣ Ratio of (K of ceramic material 10 ＩＣ / Single crystal SrTiO ３ K ＩＣ ) is preferably 1.05 or more, more preferably 1.10 or more and 1.30 or less, and even more preferably 1.15 or more and 1.30 or less. ＩＣ When the temperature is in this range, damage to the ceramic material 10 can be suppressed.

[0040] (Vickers Hardness) The Vickers hardness of the ceramic material 10 is preferably 500 HV or more, more preferably 550 HV or more, more preferably 600 HV or more, more preferably 650 HV or more, more preferably 700 HV or more, more preferably 750 HV or more, even more preferably 800 HV or more, and even more preferably 850 HV or more. When the Vickers hardness is within this range, the wear resistance of the ceramic material 10 is improved. The Vickers hardness can be evaluated using a Vickers hardness tester (FV-800) manufactured by Future Tech. In this case, the measurement conditions may be a load of 0.5 kgf and a pressure time of 15 seconds. The same conditions may be used when evaluating fracture toughness using the IF method.

[0041] (Evaluation of Color) This ceramic material is prone to coloration due to its high Ti content, but it is preferable for the ceramic material to be colorless. Therefore, color evaluation is performed. The method used was to roughen both surfaces of a sample using #500 sandpaper, irradiate it with 100 W white light, and visually confirm the color of the scattered light. In this color evaluation, it is preferable that the ceramic material 10 has a white appearance (color of scattered light).

[0042] (Method for Manufacturing Ceramic Material) The ceramic material 10 according to this embodiment may be manufactured by any method, and an example of the manufacturing method will be described below.

[0043] (Preparation of Raw Materials) In this manufacturing method, a powdered main raw material that is the raw material of the main component of the ceramic material 10 is prepared as the raw material used to manufacture the ceramic material 10. The main raw material is a material that contains elements contained in the main component of the ceramic material 10. The main raw material may be any material that contains elements contained in the main component of the ceramic material 10. The main raw material may be, for example, the main component of the ceramic material 10 itself. That is, for example, in this embodiment, the main raw material is A (B1 ｖ , B2 １－ｖ ) O ｗ ) powder. The main raw material may also be a plurality of types of materials containing some of the elements contained in the main components of the ceramic material 10. That is, for example, in this embodiment, the main raw materials may be an oxide of element A, an oxide of element B1, and an oxide of element B2.

[0044] When the ceramic material 10 contains a minor component, a powdered minor component that is the raw material of the minor component of the ceramic material 10 is also prepared. The minor component is a material containing an element contained in the minor component of the ceramic material 10, and is a so-called sintering aid. The minor component may be any material containing an element contained in the minor component of the ceramic material 10. The minor component may be an oxide of an element contained in the minor component (for example, Li ２ O, SiO ２ , B ２ O ３ , MgO, etc.), fluorides of elements contained in the secondary components (e.g., LiF, MgF ２etc.), carbonates of elements contained in the secondary components (e.g., Li ２ CO ３ etc.)

[0045] When the ceramic material 10 contains an auxiliary component, a powdered auxiliary raw material that is the raw material for the auxiliary component of the ceramic material 10 is also prepared. The auxiliary raw material is a material that contains an element contained in the auxiliary component of the ceramic material 10, and is a so-called oxidizer. The auxiliary raw material may be any material that contains an element contained in the auxiliary component of the ceramic material 10. The auxiliary raw material may be an oxide of the element contained in the auxiliary component (e.g., CeO ２ , Pr ６ O １１ etc.)

[0046] The average particle size of the raw materials (main raw material, auxiliary raw material, and supplementary raw material) may be any value, but is preferably 0.03 μm or more and 5.00 μm or less. This allows for proper sintering. The average particle size can be measured, for example, using a particle size distribution analyzer (Shimadzu Corporation: SALD-2300).

[0047] The types and compounding ratios of the raw materials may be appropriately set depending on the composition of the ceramic material 10 to be produced.

[0048] (Mixing of Raw Materials) Next, the prepared raw materials are mixed. Any method for mixing the raw materials may be used, for example, a ball mill may be used. Alternatively, a solvent may be added to the raw materials to perform wet mixing. In this case, for example, a solvent (e.g., water or ethanol) and a mixing medium (e.g., alumina or zirconia) may be added to the raw materials, and the raw materials may be wet-mixed for a period of 1 hour to 5 hours. A dispersant may also be added to dissolve aggregations between the raw material powders. When wet mixing is performed, once mixing is complete, liquid components are removed from the mixed raw materials (slurry) by a drying process or the like. If the mixed raw materials contain carbon components, a carbon removal process may be performed to remove the carbon components. The carbon removal process may be, for example, a process in which the mixed raw materials are held at a temperature range of 800°C to 1100°C for 1 hour to 20 hours. The carbon removal process may be performed in an air atmosphere or an oxygen atmosphere.

[0049] (Shaping of raw materials) Next, the mixed raw materials are molded into a desired shape to obtain a molded body, which is an assembly of raw materials molded into a desired shape. The method for manufacturing the molded body is not particularly limited, but molding by powder compact molding or slip casting is preferred.

[0050] (Powder Compaction Method) In the powder compaction method, for example, a binder (e.g., an organic binder such as polyvinyl alcohol) may be added to the mixed raw materials to obtain a raw material slurry containing the binder added to the raw materials. In addition to the binder, an organometallic compound or a lactate component may also be added. The obtained raw material slurry is then pressurized and molded into a desired shape. For example, the raw material slurry is molded using a uniaxial press, and then subjected to a CIP (Cold Isostatic Pressing) process under conditions of 125 MPa or more and 175 MPa or less to obtain a molded body.

[0051] (Slip Casting Method) For example, a molded body can also be produced by slip casting. Slip casting methods include flow casting, pressure casting, and drain casting. Pressure casting is a method in which raw material slurry is poured into a stack of molds (e.g., plaster) under pressure from below, and the raw material slurry is dried without being discarded. The raw material slurry can be obtained by a method similar to that described for the powder compact molding method. The drain casting method is a method in which a mixed raw material slurry is poured into a mold and the solvent is dried to obtain a molded body. The raw material slurry is obtained by adding a solvent to the mixed raw materials. The solvent may be aqueous or non-aqueous. However, if the solvent is aqueous, a plaster mold, which is typically used as a slip casting mold, may dissolve water in the plaster and become mixed into the molded body, potentially degrading the optical properties. Therefore, a resin mold or porous ceramic mold is preferred. When using a non-aqueous solvent such as alcohol as the solvent, a plaster mold is preferred. In this embodiment, an aqueous solvent is preferred. The mold is preferably made of porous ceramics, and the mold wall may be made of mirror-finished glass or PVC to improve mold releasability.

[0052] (Degreasing of the compact) Next, a degreasing treatment is performed to remove the binder component from the compact. In the degreasing treatment, for example, the obtained compact is heated to 700° C. or higher and 800° C. or higher in the air atmosphere.

[0053] (Sintering of the molded body) Next, the degreased molded body is sintered to obtain a ceramic material 10, which is a sintered body of the molded body (raw material). In the sintering process, the molded body is heat-treated in an oxygen atmosphere. In this heat treatment, it is preferable to heat the molded body while applying pressure. For example, the pressure applied to the molded body may be 1 atm or more and 3 atm or less, the heating temperature of the molded body may be 1300°C or more and 1550°C or less, and the pressurizing and heating time may be more than 0 hours and 24 hours or less. In addition, in the sintering process, after the heat treatment in the oxygen atmosphere, a hot isostatic pressing (HIP) process may be performed in an atmosphere containing Ar (e.g., an Ar atmosphere or a mixed atmosphere of Ar and oxygen). The applied pressure in the HIP process may be 100 MPa or more and 200 MPa or less, the heating temperature may be 1250°C or more and 1450°C or less, and the HIP process time may be 1 hour or more and 4 hours or less. Furthermore, the sintered body after the HIP treatment may be subjected to a post-annealing treatment in which the sintered body is held at 800° C. or higher and 1400° C. or lower in an air atmosphere or an oxygen atmosphere, thereby recovering the reduced state caused by the HIP treatment.

[0054] The ceramic material 10 obtained by sintering in this manner may be subjected to mechanical processing such as polishing.

[0055] The powder compaction method and slip casting method described above are not limited to use in manufacturing the ceramic material 10 according to this embodiment. For example, a transparent ceramic body having a refractive index of 2.30 or more at a wavelength of 635 nm may be manufactured by powder compaction method or slip casting method. That is, in this case, a green body is formed by powder compaction method or slip casting method using raw materials for the transparent ceramic body, and the green body is sintered to manufacture a transparent ceramic body having a refractive index of 2.30 or more at a wavelength of 635 nm.

[0056] As described above, the ceramic material 10 according to the first embodiment is A (B1 ｖ , B2 １－ｖ ) O ｗ The ceramic material 10 of this embodiment is mainly composed of a perovskite-structured compound represented by the chemical formula: ##STR1## The perovskite structure does not contain Mg, Zn, Y, or In. Since the ceramic material 10 of this embodiment contains a perovskite-structured compound with element A at the A site and element B1 at the B site, it has a high refractive index for visible light. Furthermore, since it contains such a perovskite-structured compound, it becomes a cubic polycrystal and has high transmittance for visible light. Furthermore, since a portion of the B site is substituted with element B2, a decrease in transmittance can be suppressed, ensuring a high refractive index and high transmittance. Furthermore, since the perovskite structure does not contain Mg, Zn, Y, or In, it is possible to ensure a high refractive index and high transmittance while suppressing the complexity of the structure caused by too many substitution elements.

[0057] Second Embodiment Next, a second embodiment will be described. In the second embodiment, the composition of the main component contained in the ceramic material 10 is different from that in the first embodiment. In the second embodiment, the description of the parts common to the first embodiment will be omitted.

[0058] (Main Component) The ceramic material 10 contains a compound (oxide) having a perovskite structure as a main component. The ceramic material 10 of the second embodiment contains A (B1 ｖ , B3 １－ｖ ) O ｗ The ceramic material 10 includes a compound having a perovskite structure represented by the chemical formula: In other words, the compound that is the main component can be said to be an oxide in which element A is located at the A site in the perovskite structure, element B1 or B3 is located at the B site in the perovskite structure, and O is located at the O site in the perovskite structure. The main component here may refer to a content of the main component relative to the entire ceramic material 10 that is greater than 50% by mass. The content of the main component in the ceramic material 10 is preferably 90% to 100% by mass, more preferably 95% to 100% by mass, relative to the entire ceramic material 10.

[0059] (Element A) The element A in the second embodiment is the same as the element A in the first embodiment, and therefore a description thereof will be omitted.

[0060] (Element B1) The element B1 in the second embodiment is the same as the element B1 in the first embodiment, and therefore a description thereof will be omitted.

[0061] (Element B3) A(B1 ｖ , B3 １－ｖ ) O ｗ In the formula (2), B3 is an element located at the B site in the perovskite structure. In the second embodiment, the element B3 is at least one element selected from Sc, Y, Zn, Yb, and Al. That is, the element B3 may contain two or more elements from Sc, Y, Zn, Yb, and Al, or may contain only one element from Sc, Y, Zn, Yb, and Al. The element B3 is preferably at least one element selected from Zn, Yb, and Al, and more preferably at least one element selected from Yb and Al.

[0062] In this embodiment, element B3 is substituted for element B1 in part of the B site. This allows high transmittance to be appropriately ensured while maintaining a high refractive index. That is, for example, if element B1 contains Ti, a high refractive index can be achieved by Ti, but Ti is easily reduced during sintering, and the reduction can cause coloration, which can reduce transmittance. Furthermore, for example, if element A contains Sr, defects can occur during sintering, which can reduce transmittance. In contrast, by substituting element B3 in part of the B site, the reduction in transmittance can be suppressed, and a high refractive index and high transmittance can be ensured.

[0063] (Number v) A (B1 ｖ , B3 １－ｖ ) O ｗ In the formula, v is a numerical value indicating the ratio (molar ratio) of the content of element B1 to the content of element B3, more specifically, the molar ratio of the content of element B1 to the total content of element B1 and element B3. That is, for example, when element B1 is only Ti, the numerical value v can be said to be the molar ratio of the content of Ti to the total content of Ti and element B3.

[0064] The numerical value v is a positive number less than 1. The numerical value v is preferably set so that the average valence of the elements B1 and B3 is 4. It can also be said that the types of the elements B1 and B3 and the numerical value v are preferably set so that the average valence of the elements B1 and B3 is 4.

[0065] The value v is preferably 0.7 or more and less than 1.0, more preferably 0.8 or more and less than 1.0, and even more preferably 0.9 or more and less than 1.0. When the value v is in this range, the ratio of element B1 to element B3 can be made appropriate, and a high refractive index and high transmittance for visible light can be appropriately ensured.

[0066] (Number w) A (B1 ｖ , B3 １－ｖ ) O ｗ In the formula (A(B1), w is a numerical value indicating the content (molar ratio) of O, more specifically, the molar ratio of the content of O to the total content of element A, element B1, element B3, and O. ｖ , B3 １－ｖ ) O ｗ ) is a value at which overall charge neutrality is achieved, and may be, for example, 3.

[0067] (Non-contained elements) The ceramic material 10 according to the second embodiment does not contain Ta and Nb in the perovskite structure (the compound having the perovskite structure as the main component). ｖ , B3 １－ｖ ) O ｗ The compound represented by the formula (I) does not contain Ta or Nb at the A site, B site, or O site. This ensures a high refractive index and high transmittance while suppressing the structural complexity caused by an excessive number of substitution elements. Note that the ceramic material 10 may contain Ta and Nb in locations other than the perovskite structure, or may contain Mg, Ta, and Nb as inevitable impurities.

[0068] (Preferable examples of main components) A (B1 ｖ , B3 １－ｖ ) O ｗ Preferred examples of the compound represented by the formula are Sr(Tiｖ , Sc １－ｖ ) O ｗ , Sr(Ti ｖ , Y １－ｖ ) O ｗ , Sr(Ti ｖ , Zn １－ｖ ) O ｗ , Sr(Ti ｖ , Al １－ｖ ) O ｗ Examples include:

[0069] (Subcomponents) As in the first embodiment, the ceramic material 10 according to the second embodiment also preferably has a subcomponent derived from a sintering aid. As in the first embodiment, the ceramic material 10 according to the second embodiment also preferably has an auxiliary component. The preferred compositions and contents of the auxiliary component and auxiliary component are the same as those in the first embodiment, and therefore will not be described here.

[0070] The ceramic material 10 according to the second embodiment may contain any component as an inevitable impurity in addition to the main component, the subcomponent, and the auxiliary component described above. It is preferable that the ceramic material 10 according to the second embodiment does not contain any component other than the main component, the subcomponent, and the auxiliary component, except for the inevitable impurities.

[0071] (Characteristics of Ceramic Material) The characteristics of the ceramic material 10 according to the second embodiment are the same as those of the ceramic material 10 according to the first embodiment, and therefore, description thereof will be omitted.

[0072] (Method for manufacturing ceramic material) The ceramic material 10 according to the second embodiment may be manufactured by any method. An example of the method for manufacturing the ceramic material 10 according to the second embodiment is similar to the example of the method for manufacturing the ceramic material 10 according to the first embodiment, and therefore a description thereof will be omitted. However, the second embodiment differs from the first embodiment in that a main raw material containing element B3 instead of element B2 is prepared.

[0073] As described above, the ceramic material 10 according to the second embodiment is A (B1 ｖ , B3 １－ｖ ) O ｗThe ceramic material 10 of this embodiment is mainly composed of a perovskite-structured compound represented by the chemical formula: ##STR1## The perovskite structure does not contain Mg, Zn, Y, or In. Since the ceramic material 10 of this embodiment contains a perovskite-structured compound with element A at the A site and element B1 at the B site, it has a high refractive index for visible light. Furthermore, since it contains such a perovskite-structured compound, it becomes a cubic polycrystal and has high transmittance for visible light. Furthermore, since a portion of the B site is substituted with element B3, a decrease in transmittance can be suppressed, ensuring a high refractive index and high transmittance. Furthermore, since the perovskite structure does not contain Ta or Nb, it is possible to ensure a high refractive index and high transmittance while suppressing the structural complexity caused by too many substitution elements.

[0074] Third Embodiment Next, a third embodiment will be described. In the third embodiment, the composition of the main components contained in the ceramic material 10 is different from that in the first embodiment. In the third embodiment, the description of the parts common to the first embodiment will be omitted.

[0075] (Main Component) The ceramic material 10 contains a compound (oxide) having a perovskite structure as a main component. The ceramic material 10 of the third embodiment contains A (Ti x , B5 ｖ , B4 １－ｖ-x ) O ｗ The ceramic material 10 includes a compound having a perovskite structure represented by the chemical formula: In other words, the compound that is the main component can be said to be an oxide in which element A is located at the A site in the perovskite structure, Ti, element B5, or element B4 is located at the B site in the perovskite structure, and O is located at the O site in the perovskite structure. The main component here may refer to a content of the main component relative to the entire ceramic material 10 that is greater than 50% by mass. The content of the main component in the ceramic material 10 is preferably 90% to 100% by mass, more preferably 95% to 100% by mass, relative to the entire ceramic material 10.

[0076] (Element A) The element A in the third embodiment is the same as the element A in the first embodiment, and therefore a description thereof will be omitted.

[0077] (Element B5) A(Ti x , B5 ｖ , B4 １－ｖ-x ) O ｗ The element B5 in the formula (I) is at least one selected from Hf, Ge, and Zr. That is, the element B5 may contain two or more elements selected from Hf, Ge, and Zr, or may contain only one element selected from Hf, Ge, and Zr.

[0078] (Element B4) A(Ti x , B5 ｖ , B4 １－ｖ-x ) O ｗ In the formula (3), B4 is an element located at the B site in the perovskite structure. In the third embodiment, the element B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn. That is, the element B4 may contain two or more elements selected from Ta, Nb, Al, Sc, Y, and Zn, or may contain only one element selected from Ta, Nb, Al, Sc, Y, and Zn. The element B4 is preferably at least one selected from Ta, Nb, Al, and Zn, and more preferably at least one selected from Ta, Nb, and Al.

[0079] (value v) A(Ti x , B5 ｖ , B4 １－ｖ-x ) O ｗIn the formula, x represents the ratio (molar ratio) of the content of Ti, the content of element B5, and the content of element B4, more specifically, the molar ratio of the content of Ti to the total content of Ti, element B1, and element B4. v represents the ratio (molar ratio) of the content of Ti, element B5, and the content of element B4, more specifically, the molar ratio of the content of element B5 to the total content of Ti, element B5, and element B4. The value x is 0.7 or more and 1.0 or less, preferably 0.8 or more and 1.0 or less, and more preferably 0.9 or more and 1.0 or less. The value v is 0.0 or more and 0.3 or less, preferably 0.0 or more and 0.2 or less, and more preferably 0.0 or more and 0.1 or less. Furthermore, the sum of the values ​​x and v is 1.0 or less (x + v ≦ 1.0), preferably 0.99 or less, more preferably 0.97 or less, preferably 0.94 or less, and more preferably 0.90 or less. By setting the values ​​x and v within these ranges, the ratio of Ti element, element B5, and element B4 can be optimized, thereby ensuring a high refractive index and high transmittance for visible light. That is, for example, Ti element in the B site can achieve a high refractive index, but Ti is easily reduced during sintering, and the reduction can cause coloration, which can reduce transmittance. Furthermore, for example, element A can cause defects during sintering, which can reduce transmittance. On the other hand, by substituting a portion of the B site with element B4 and keeping the molar ratio (values ​​x, v) of Ti element, element B5, and element B4 within the above range, the decrease in transmittance can be suppressed, ensuring a high refractive index and high transmittance.

[0080] The numerical value v is a positive number less than 1. The numerical value v is preferably set so that the average valence of the elements B5 and B4 is 4. It can also be said that the types of the elements B5 and B4 and the numerical value v are preferably set so that the average valence of the elements B5 and B4 is 4.

[0081] (Number w) A (Ti x , B5 ｖ , B4 １－ｖ-x ) O ｗIn the formula, w is a numerical value indicating the content (molar ratio) of O, more specifically, the molar ratio of the content of O to the total content of element A, element B5, element B4, and O. The numerical value w is x , B5 ｖ , B4 １－ｖ-x ) O ｗ This is a value that ensures overall charge neutrality, and may be, for example, 3.

[0082] (Preferable examples of main components) A (Ti) in the third embodiment ｘ , B5 ｖ , B4 １－ｖ－ｘ ) O ｗ Preferred examples of the compound represented by the formula are Sr(Ti ｘ , Zr v ) O ｗ、 Sr(Ti ｘ , Ge v ) O ｗ,　 Sr(Ti ｘ , Hf v ) O ｗ,　 Sr(Ti ｘ , Zr v , Ta １－ｖ-x ) O ｗ , Sr(Ti ｘ , Zr v , Nb １－ｖ ) O ｗ , Sr(Ti ｘ , Zr v , Al １－ｖ-x ) O ｗ Sr(Ti x,　 Zr v , Sc １－ｖ-x ) O ｗ , Sr(Ti x , Zr v , Y １－ｖ-x ) O ｗ , Sr(Ti x , Zr v , Zn １－ｖ-x ) O ｗ、 Sr(Ti ｘ , Ge v , Ta １－ｖ-x ) O ｗ , Sr(Ti ｘ , Ge v , Nb １－ｖ ) O ｗ , Sr(Ti ｘ, Ge v , Al １－ｖ-x ) O ｗ Sr(Ti x, Ge v , Sc １－ｖ-x ) O ｗ , Sr(Ti x , Ge v , Y １－ｖ-x ) O ｗ , Sr(Ti x , Ge v , Zn １－ｖ-x ) O ｗ Examples include:

[0083] (Subcomponents) As in the first embodiment, the ceramic material 10 according to the third embodiment also preferably has a subcomponent derived from a sintering aid. As in the first embodiment, the ceramic material 10 according to the third embodiment also preferably has an auxiliary component. Since the preferred compositions and contents of the auxiliary component and auxiliary component are the same as those in the first embodiment, the description thereof will be omitted.

[0084] The ceramic material 10 according to the third embodiment may contain any component as an inevitable impurity in addition to the main component, the subcomponent, and the auxiliary component described above. It is preferable that the ceramic material 10 according to the third embodiment does not contain any component other than the main component, the subcomponent, and the auxiliary component, except for the inevitable impurities.

[0085] (Characteristics of Ceramic Material) The characteristics of the ceramic material 10 according to the third embodiment are the same as those of the ceramic material 10 according to the first embodiment, and therefore a description thereof will be omitted. However, the equivalent internal transmittance of the ceramic material 10 according to the third embodiment for light with a wavelength of 635 nm is 5% or more, preferably 15% or more, per 1 mm thickness. As described above, the equivalent internal transmittance is determined depending on the composition of the ceramic material 10. However, even with the same composition, the equivalent internal transmittance may vary depending on the production process of the ceramic material 10. Therefore, for example, the equivalent internal transmittance can be adjusted to the above range by appropriately adjusting the production process of the ceramic material 10. Note that the production process can be adjusted using known methods, such as carefully mixing raw materials. For example, the equivalent internal transmittance can also be adjusted to the above range by adjusting the ratio of the total content of K, Na, La, Yb, and Gd in element A to the total content of element A, for example, to 0.05% or more and 10% or less in molar ratio.

[0086] (Method for manufacturing ceramic material) The ceramic material 10 according to the third embodiment may be manufactured by any method. An example of the method for manufacturing the ceramic material 10 according to the third embodiment is similar to the example of the method for manufacturing the ceramic material 10 according to the first embodiment, and therefore a description thereof will be omitted. However, the third embodiment differs from the first embodiment in that a main raw material containing element B4 instead of element B3 is prepared.

[0087] As described above, the ceramic material 10 according to the third embodiment is x , B5 ｖ , B4 １－ｖ―ｘ ) O ｗThe ceramic material 10 of this embodiment is mainly composed of a perovskite-structured compound represented by the chemical formula: where x is 0.7 or more and 1.0 or less, v is 0.0 or more and 0.3 or less, and x + v ≦ 1.0. The equivalent internal transmittance at a thickness of 1 mm for light with a wavelength of 635 nm is 5% or more. Since the ceramic material 10 of this embodiment contains a perovskite-structured compound with element A as the A site and element B1 as the B site, it has a high refractive index for visible light. Furthermore, since it contains such a perovskite-structured compound, it becomes a cubic polycrystal and has high transmittance for visible light. Furthermore, by substituting a portion of the B site with element B4 and setting the ratio (value v) of element B5 to element B4 within the above range, a decrease in transmittance can be suppressed, ensuring a high refractive index and high transmittance.

[0088] (Fourth embodiment) Next, a fourth embodiment will be described. In the third embodiment, the composition of the main component contained in the ceramic material 10 is different from that in the first embodiment. In the fourth embodiment, the description of the parts common to the first embodiment will be omitted.

[0089] (Main Component) The ceramic material 10 contains a compound (oxide) having a perovskite structure as a main component. The ceramic material 10 of the third embodiment contains A0 (B1 ｖ , B4 １－ｖ ) O ｗ The ceramic material 10 includes a compound having a perovskite structure represented by the chemical formula: In other words, the compound that is the main component can be said to be an oxide in which element A0 is located at the A site in the perovskite structure, element B1 or element B4 is located at the B site in the perovskite structure, and O is located at the O site in the perovskite structure. The main component here may refer to a content of the main component relative to the entire ceramic material 10 that is greater than 50% by mass. The content of the main component in the ceramic material 10 is preferably 90% to 100% by mass, more preferably 95% to 100% by mass, relative to the entire ceramic material 10.

[0090] (Element A0) A0(B1 ｖ , B4 １－ｖ ) O ｗIn the formula, A0 is an element located at the A site in the perovskite structure. In the fourth embodiment, the element A0 includes Sr and at least one of K, Na, La, Gd, and Yb. That is, the element A0 may include Sr and one of K, Na, La, Gd, and Yb, or may include Sr and two or more of K, Na, La, Gd, and Yb. By including Sr in the element A0, a high refractive index and high transmittance for visible light can be appropriately ensured. However, if the element A0 includes Sr, defects may occur during sintering, which may reduce the transmittance. On the other hand, by substituting a portion of the A site with La, Gd, Yb, K, or Na, the decrease in transmittance can be suppressed.

[0091] The content of Sr relative to the entire element A0 is preferably 50% or more, more preferably 60.0% or more and 99.5% or less, and even more preferably 70% or more and 99.5% or less, in molar ratio. By setting the Sr content within this range, high refractive index and high transmittance for visible light can be appropriately ensured. The content of K, Na, La, Gd, and Yb relative to the entire element A0 is preferably 0.5% or more and 50% or less, more preferably 0.5% or more and 40% or less, more preferably 0.5% or more and 30% or less, and even more preferably 0.5% or more and 20% or less, in molar ratio. Here, the content of K, Na, La, Gd, and Yb refers to the total content of K, Na, La, Gd, and Yb contained in element A0, and when element A0 contains all of K, Na, La, Gd, and Yb, it refers to the total content of K, Na, La, Gd, and Yb, and when element A0 contains only a part of K, Na, La, Gd, and Yb, it refers to the content of that part of the components contained. By setting the content within this range, it is possible to suitably suppress a decrease in transmittance.

[0092] The element A0 may contain an element other than Sr, K, Na, La, Gd, and Yb. Examples of elements other than Sr, K, Na, La, Gd, and Yb include Ba.

[0093] (Element B1) The element B1 in the fourth embodiment is the same as the element B1 in the first embodiment, and therefore a description thereof will be omitted.

[0094] (Element B4) Element B4 in the fourth embodiment is the same as element B4 in the third embodiment, and therefore description thereof will be omitted.

[0095] (Number v) A0(B1 ｖ , B4 １－ｖ ) O ｗ In the formula, v is a numerical value indicating the ratio (molar ratio) of the content of element B1 to the content of element B4, and more specifically, the molar ratio of the content of element B1 to the total content of element B1 and element B4.

[0096] The numerical value v is a positive number less than 1. The numerical value v is preferably set so that the average valence of the elements B1 and B4 is 4. It can also be said that the types of the elements B1 and B4 and the numerical value v are preferably set so that the average valence of the elements B1 and B4 is 4.

[0097] The numerical value v is preferably 0.5 or more and 1 or less, more preferably 0.7 or more and 1 or less, more preferably 0.8 or more and 1 or less, and even more preferably 0.9 or more and 1 or less. When the numerical value v is within this range, the ratio of the element B1 to the element B4 can be made appropriate, and a high refractive index and high transmittance for visible light can be appropriately ensured.

[0098] (Number w) A0 (B1 ｖ , B4 １－ｖ ) O ｗ In the formula (A0(B1), w is a numerical value indicating the content (molar ratio) of O, more specifically, the molar ratio of the content of O to the total content of element A0, element B1, element B4, and O. ｖ , B4 １－ｖ ) O ｗ ) is a value at which overall charge neutrality is achieved, and may be, for example, 3.

[0099] (Preferable examples of main components) A0 (B1 ｖ , B4 １－ｖ ) O ｗ Preferred examples of the compound represented by the formula: ｖ , Ta １－ｖ ) O ｗ , A0(Ti ｖ , Nb １－ｖ ) Oｗ , A0(Ti ｖ , Al １－ｖ ) O ｗ , A0(Ti ｖ , Sc １－ｖ ) O ｗ , A0(Ti ｖ , Y １－ｖ ) O ｗ , A0(Ti ｖ , Zn １－ｖ ) O ｗ Here, A0 is preferably Sr and La, Sr and Gd, or Sr, La and Gd.

[0100] (Subcomponents) As in the first embodiment, the ceramic material 10 according to the fourth embodiment also preferably has a subcomponent derived from a sintering aid. As in the first embodiment, the ceramic material 10 according to the fourth embodiment also preferably has an auxiliary component. Since the preferred compositions and contents of the auxiliary component and auxiliary component are the same as those in the first embodiment, the description thereof will be omitted.

[0101] The ceramic material 10 according to the fourth embodiment may contain any component as an inevitable impurity in addition to the main component, the subcomponent, and the auxiliary component described above. It is preferable that the ceramic material 10 according to the fourth embodiment does not contain any component other than the main component, the subcomponent, and the auxiliary component, except for the inevitable impurities.

[0102] (Characteristics of Ceramic Material) The characteristics of the ceramic material 10 according to the fourth embodiment are the same as the characteristics of the ceramic material 10 according to the first embodiment, and therefore, description thereof will be omitted.

[0103] (Method for manufacturing ceramic material) The ceramic material 10 according to the fourth embodiment may be manufactured by any method. An example of the method for manufacturing the ceramic material 10 according to the fourth embodiment is similar to the example of the method for manufacturing the ceramic material 10 according to the first embodiment, and therefore a description thereof will be omitted. However, the fourth embodiment differs from the first embodiment in that a main raw material containing elements A0 and B4 instead of elements A and B3 is prepared.

[0104] As described above, the ceramic material 10 according to the fourth embodiment has a structure of A0 (B1ｖ , B4 １－ｖ ) O ｗ The ceramic material 10 of this embodiment mainly comprises a compound with a perovskite structure represented by the chemical formula: ##STR1## Since the ceramic material 10 of this embodiment contains a compound with a perovskite structure in which an element A0 containing Sr is at the A site and an element B1 is at the B site, it has a high refractive index for visible light. Furthermore, since it contains such a compound with a perovskite structure, it becomes a cubic polycrystal and has high transmittance for visible light. Furthermore, by substituting a portion of the A site with K, Na, La, Gd, Yb, or the like and substituting a portion of the B site with element B4, it is possible to suppress a decrease in transmittance and ensure a high refractive index and high transmittance.

[0105] (Effects) As described above, the ceramic material 10 according to the first aspect of the present disclosure has A (B1 ｖ , B2 １－ｖ ) O ｗ The present disclosure has as its main component a compound with a perovskite structure represented by the chemical formula: wherein element A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb, element B1 is at least one selected from Ti and Hf, and element B2 is at least one selected from Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca, and Al, the perovskite structure does not contain Mg, Zn, Y, or In, v is a positive number less than 1, and w is a value that achieves charge neutrality in the entire chemical formula. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0106] The ceramic material 10 according to the second aspect of the present disclosure is A (B1 ｖ , B3 １－ｖ ) O ｗThe present disclosure has as its main component a compound with a perovskite structure represented by the chemical formula: wherein element A is at least one selected from Ba, Sr, Ca, La, K, Na, Gd, and Yb, element B1 is at least one selected from Ti, Hf, Ge, and Zr, and element B3 is at least one selected from Sc, Y, Zn, Yb, and Al, the perovskite structure does not contain Ta or Nb, v is a positive number less than 1, and w is a value that achieves charge neutrality in the entire chemical formula. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0107] The ceramic material 10 according to the third aspect of the present disclosure is ｘ , B5 ｖ , B4 １－ｖ-x ) O ｗ The present disclosure has as its main component a compound with a perovskite structure represented by the chemical formula: wherein element A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb, element B5 is at least one selected from Hf, Ge, and Zr, element B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn, x is 0.7 or more and 1.0 or less, v is 0 or more and 0.3 or less, x + v ≦ 1.0, and w is a value that satisfies charge neutrality of the entire chemical formula, and the equivalent internal transmittance at a thickness of 1 mm for light with a wavelength of 635 nm is 5% or more. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0108] The ceramic material 10 according to the fourth aspect of the present disclosure is the ceramic material according to the third aspect, and preferably has an internal transmittance of 15% or more at a thickness of 1 mm for light having a wavelength of 635 nm. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0109] The ceramic material 10 according to the fifth aspect of the present disclosure is A0 (B1 ｖ , B4 １－ｖ ) O ｗThe present disclosure has as its main component a compound with a perovskite structure represented by the chemical formula: wherein the element A0 contains Sr and at least one of K, Na, La, Gd, and Yb, the element B1 is at least one selected from Ti, Hf, Ge, and Zr, the element B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn, v is a positive number less than 1, and w is a value that achieves charge neutrality in the entire chemical formula. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0110] The ceramic material 10 according to a sixth aspect of the present disclosure is the ceramic material 10 according to any one of the first to fifth aspects, and preferably contains at least one auxiliary component selected from Li, Si, B, and Mg. According to the present disclosure, the inclusion of such auxiliary components allows for the appropriate production of a ceramic material 10 with a high refractive index and high transmittance.

[0111] The ceramic material 10 according to a seventh aspect of the present disclosure is the ceramic material 10 according to the sixth aspect, and preferably has a content of the accessory component of 50 ppm to 50,000 ppm by mass relative to the entire ceramic material 10. According to the present disclosure, by setting the content of the accessory component within this range, it is possible to appropriately produce a ceramic material 10 having a high refractive index and high transmittance.

[0112] The ceramic material 10 according to an eighth aspect of the present disclosure is the ceramic material 10 according to any one of the first to seventh aspects, and preferably has an internal transmittance of 5% or more per 1 mm of material thickness for light with a wavelength of 635 nm. According to the present disclosure, the ceramic material 10 can adequately transmit visible light.

[0113] The ceramic material 10 according to a ninth aspect of the present disclosure is the ceramic material 10 according to any one of the first to eighth aspects, and preferably has a refractive index of 2.3 or more for light with a wavelength of 635 nm. According to the present disclosure, visible light can be appropriately refracted.

[0114] The ceramic material 10 according to a tenth aspect of the present disclosure is the ceramic material 10 according to any one of the first to ninth aspects, and is a single crystal material of SrTiO ３ Fracture toughness value KＩＣ Fracture toughness value K ＩＣ It is preferable that the ratio is 1.05 or more. According to the present disclosure, breakage of the ceramic material 10 can be appropriately suppressed.

[0115] The ceramic material 10 according to an eleventh aspect of the present disclosure is the ceramic material 10 according to any one of the first to tenth aspects, and preferably has a Vickers hardness of 500 HV or more. According to the present disclosure, breakage of the ceramic material 10 can be appropriately suppressed.

[0116] An optical member according to a twelfth aspect of the present disclosure includes the ceramic material 10 according to any one of the first to eleventh aspects as a light guide plate. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0117] A head-mounted display according to a thirteenth aspect of the present disclosure includes a light guide plate member made of the ceramic material 10 according to any one of the first to twelfth aspects. According to the present disclosure, visible light can be transmitted while being appropriately refracted.

[0118] A manufacturing method according to a fourteenth aspect of the present disclosure manufactures the ceramic material 10 according to any one of the first to twelfth aspects by powder compaction or slip casting. According to the present disclosure, it is possible to appropriately manufacture a ceramic material that can transmit visible light while appropriately refracting it.

[0119] In a fifteenth aspect of the present disclosure, a transparent ceramic body having a refractive index of 2.30 or more at a wavelength of 635 nm is produced by powder compaction or slip casting. According to the present disclosure, a ceramic material that can transmit visible light while appropriately refracting it can be produced appropriately.

[0120] Examples Next, examples will be described. Note that the embodiment may be modified as long as the effects of the invention are achieved. Tables 1-12 show the ceramic materials of each example and their evaluation results.

[0121]

[0122] (Example 1) In Example 1, strontium carbonate, titanium oxide, and aluminum oxide powder were prepared as main raw materials, and SiO was prepared as a secondary raw material (sintering aid). ２ Powders were prepared. Each main raw material was stoichiometrically divided into SrTi and ０．９９５ Zr ０．００５ O ３ The blending ratio was set to obtain the following. The average particle size of the raw materials measured using a particle size distribution analyzer (Shimadzu Corporation: SALD-2300) was 0.1 to 2.0 μm. The raw materials were wet-mixed using alumina balls as grinding media in a ball mill for 2 hours, and then the mixed raw materials were dried at 80°C for 10 hours. The dried raw materials were then decarbonized at 1050°C for 10 hours. A binder (aqueous PVA solution, prepared from Kanto Chemical Co., Inc.) was added to the decarbonized raw materials to obtain a raw material slurry. The obtained raw material slurry was dried at 80°C for 10 hours, and a compact was obtained using a uniaxial press and CIP method. The obtained compact was then degreased at 900°C for 5 hours. The degreased compact was sintered at 1500°C under conditions of 2 atm oxygen, then HIP-treated at 1350°C for 1 hour in an Ar atmosphere of 150 MPa, and then annealed at 1000°C for 6 hours in an air atmosphere to obtain the ceramic material of Example 1.

[0123] As shown in Table 1, the composition of the main component (perovskite structure compound) of the ceramic material of Example 1 is SrTi ０．９９５ Zr ０．００５ O ３ The composition of the subcomponent is SiO ｘ The content of the subcomponent was 5000 ppm. The refractive index, converted internal transmittance, and color evaluation of the ceramic material of Example 1 for light with a wavelength of 635 nm were measured. The measurement conditions were the same as those described in this embodiment. The measurement results of the refractive index and converted internal transmittance are shown in Table 1.

[0124] (Examples 2 to 8) In Examples 2 to 8, ceramic materials were obtained in the same manner as in Example 1, except for the conditions of the raw material composition, auxiliary raw materials, and supplementary raw materials. In Example 3, SrTi ０．９９５ Ge ０．００５ O ３ The main raw materials are prepared so that SrTi is the main component. ０．９９５ Ge ０．００５ O ３ In Example 4, the stoichiometric ratio of SrTi was ０．９９５ Al ０．００５ O ３ The main raw materials are prepared so that SrTi is the main component. ０．９９５ Al ０．００５ O ３ In Example 5, the stoichiometric ratio of SrTi was ０．９９５ Ta ０．００５ O ３ The main raw materials are prepared so that SrTi is the main component. ０．９９５ Ta ０．００５ O ３ In Example 6, the stoichiometric ratio of SrTi was ０．９９５ Nb ０．００５ O ３ The main raw materials are prepared so that SrTi is the main component. ０．９９５ Nb ０．００５ O ３ In Example 7, the stoichiometric ratio of Sr ０．９９５ Yb ０．００５ TiO ３ The main raw material is prepared so that Sr ０．９９５ Yb ０．００５ TiO ３ In Example 8, the stoichiometric ratio of SrTiO ３ The main raw material was prepared so that polycrystalline SrTiO ３ The table shows the results of measurements of the main component composition, the subcomponent composition and content, the refractive index and converted internal transmittance, and the color evaluation of the ceramic material of each example.

[0125] (Example 9) In Example 9, SrTiO was used for comparison with ceramic materials in terms of refractive index and Vickers hardness test. ３ The results of measurement and evaluation of single crystal materials are shown below.

[0126] In Examples 10 to 42, ceramic materials were obtained in the same manner as in Examples 1 to 8 except for the raw material composition, auxiliary raw material, and supplementary raw material conditions. Examples 1 to 7 and 10 to 42 are working examples, Example 8 is a comparative example, and Example 9 is a reference example.

[0127] (Examples 17, 32 to 35, 37, and 38) The degreased compacts of Example 1 were sintered at 1450°C under conditions of 2 atm oxygen, HIPed at 1350°C for 1 hour in an Ar atmosphere of 150 MPa, and annealed at 1100°C in air to obtain ceramic materials in the same manner as above.

[0128] (Examples 18 to 31, Example 36) The degreased compact of Example 1 was sintered at 1450°C under conditions of 2 atm oxygen, and then HIP-treated at 1350°C for 1 hour in an Ar atmosphere of 150 MPa to obtain ceramic materials in the same manner.

[0129] (Examples 43 to 61) In Examples 43 to 61, ceramic materials were obtained in the same manner as Examples 1 to 8 and Examples 10 to 42, except for the raw material composition and the conditions of the auxiliary raw materials and supplementary raw materials. Examples 43 to 61 are comparative examples for Examples 10 to 42. Various sintering conditions and HIP conditions were investigated, but it was not possible to obtain translucency.

[0130] (Evaluation) The evaluation included refractive index evaluation, transmittance evaluation, Vickers hardness, and color evaluation. For the evaluation of converted internal transmittance, the internal transmittance of a 1 mm thickness was evaluated, and when evaluation was possible, the numerical value was entered in each table. For the evaluation of color, a white appearance was rated as A (good), and a colored appearance was rated as B (fair). For Vickers hardness and fracture toughness evaluation (IF method), evaluations were conducted on representative materials.

[0131] Although the embodiments of the present invention have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0132] 10. Ceramic materials

Claims

1. A (B1 ｖ , B2 １－ｖ ) O ｗ a ceramic material having as its main component a compound having a perovskite structure represented by the chemical formula: wherein A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb; B1 is at least one selected from Ti and Hf; and B2 is at least one selected from Ta, Nb, Zr, Ge, Gd, Yb, Ga, Ca, and Al; the perovskite structure does not contain Mg, Zn, Y, or In; v is a positive number less than 1, and w is a number that satisfies charge neutrality of the entire chemical formula.

2. A (B1 ｖ , B3 １－ｖ ) O ｗ a ceramic material having as its main component a compound having a perovskite structure represented by the chemical formula: wherein A is at least one selected from Ba, Sr, Ca, La, K, Na, Gd, and Yb; B1 is at least one selected from Ti, Hf, Ge, and Zr; and B3 is at least one selected from Sc, Y, Zn, Yb, and Al; the perovskite structure does not contain Ta or Nb; v is a positive number less than 1, and w is a number that satisfies charge neutrality of the entire chemical formula.

3. A (Ti x , B5 ｖ , B4 １－ｖ-x ) O ｗ a compound having a perovskite structure represented by the chemical formula: A is at least one selected from Ba, Sr, Ca, K, Na, La, Gd, and Yb; B5 is at least one selected from Hf, Ge, and Zr; B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn; x is 0.7 or more and 1.0 or less, v is 0 or more and 0.3 or less, x+v≦1.0, and w are values ​​that satisfy charge neutrality of the entire chemical formula; and the ceramic material has an internal transmittance of 5% or more for light with a wavelength of 635 nm at a thickness of 1 mm.

4. The ceramic material according to claim 3, having an internal transmittance of 15% or more for light having a wavelength of 635 nm per 1 mm thickness.

5. A0 (B1 ｖ , B4 １－ｖ ) O ｗ a ceramic material having as its main component a compound having a perovskite structure represented by the chemical formula: wherein A0 contains Sr and at least one of K, Na, La, Gd, and Yb; B1 is at least one selected from Ti, Hf, Ge, and Zr; B4 is at least one selected from Ta, Nb, Al, Sc, Y, and Zn; v is a positive number less than 1; and w is a numerical value that satisfies charge neutrality of the entire chemical formula.

6. A ceramic material according to any one of claims 1 to 5, containing at least one element selected from the group consisting of Li, Si, B, and Mg as an auxiliary component.

7. The ceramic material according to claim 6, wherein the content of the subcomponent is 50 ppm or more and 50,000 ppm or less by mass ratio with respect to the entire ceramic material.

8. A ceramic material according to any one of claims 1, 2 and 5, having an internal transmittance of 5% or more for light having a wavelength of 635 nm per 1 mm thickness.

9. A ceramic material according to any one of claims 1 to 4, having a refractive index of 2.30 or more for light with a wavelength of 635 nm.

10. Single crystal SrTiO ３ Fracture toughness value K ＩＣ Fracture toughness value K ＩＣ The ceramic material according to any one of claims 1 to 5, wherein the ratio is 1.05 or more.

11. The ceramic material according to any one of claims 1 to 5, having a Vickers hardness of 500 HV or more.

12. An optical component comprising a light guide plate made of the ceramic material according to any one of claims 1 to 5.

13. A head mounted display using the ceramic material according to any one of claims 1 to 5 as a light guide plate member.

14. A method for producing a ceramic material according to any one of claims 1 to 5 by powder compaction or slip casting.

15. A manufacturing method for producing a transparent ceramic body having a refractive index of 2.30 or more at a wavelength of 635 nm by powder compact molding or casting molding.

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