Powder material, ceramic material, and method for producing ceramic material

Abstract

The present invention appropriately transmits visible light. This powder material has an average primary particle diameter of 50-500 nm, has a cubicity of 0.96 or less, and contains SrxTiOz as a main component, where x is 0.9-1.0, and z is a numerical value such that the charge of the entire chemical formula is neutral.

Description

Powder material, ceramic material, and method for manufacturing ceramic material

[0001] This invention relates to powder materials, ceramic materials, and methods for producing ceramic materials.

[0002] In recent years, there has been a demand for materials with high transmittance. In particular, in wearable devices such as head-mounted displays that realize AR (Augmented Reality), VR (Virtual Reality), and MR (Mixed Reality), as shown in Patent Document 1, high transmittance to visible light is required for the light guide plate. Patent Document 2 also describes a light-transmitting ceramic mainly composed of a perovskite compound.

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

[0004] In this context, ceramic materials are required to transmit visible light appropriately.

[0005] The present invention aims to provide a powder material, a ceramic material, and a method for manufacturing a ceramic material that can appropriately transmit visible light.

[0006] The powder material relating to this disclosure has an average primary particle size of 50 nm or more and 500 nm or less, a cubicity of 0.96 or less, and Sr x TiO ｚ The main component is , x is between 0.9 and 1.0, and z is a value that maintains charge neutrality for the entire chemical formula.

[0007] The powder material relating to this disclosure has an average primary particle size of 50 nm or more and 500 nm or less, and a specific surface area of ​​5 m². ２ / g or more 18m ２ / g or less, Sr x TiO ｚ The main component is , x is between 0.9 and 1.0, and z is a value that maintains charge neutrality for the entire chemical formula.

[0008] The ceramic material according to the present disclosure is a sintered body of the powder material, having a total light internal transmittance of 70% or more and 100% or less for light with a wavelength of 635 nm and a thickness of 1 mm, and a refractive index of 2.35 or more and 2.40 or less for light with a wavelength of 635 nm.

[0009] The method for manufacturing a ceramic material according to the present disclosure manufactures a ceramic material by sintering the powder material.

[0010] According to the present invention, a ceramic material capable of appropriately transmitting visible light can be provided.

[0011] FIG. 1A is a schematic diagram for explaining the degree of cubicity. FIG. 1B is a flowchart showing a method for manufacturing a powder material. FIG. 2 is a flowchart showing a method for manufacturing a ceramic material according to the present embodiment. FIG. 3 is a schematic diagram of a furnace for performing primary sintering. FIG. 4 is a schematic diagram of a furnace for performing HIP treatment. FIG. 5 is a schematic diagram of a furnace for performing post-annealing treatment.

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. Also, numerical values include the range of rounding. In the present embodiment, the lower limit value and the upper limit value of the numerical range can be appropriately combined.

[0013] (Powder Material) The powder material according to the present embodiment is a powder mainly composed of Sr x TiO ｚ Although it is used as a raw material for the ceramic material 10 described later, its use is not limited to the raw material for the ceramic material 10 and may be arbitrary.

[0014] (Composition of Powder Material) The powder material contains, as a main component, a compound (oxide) having a perovskite structure represented by the chemical formula of Sr x TiO ｚ Here, the main component may refer to a content rate with respect to the whole powder material being more than 50% in molar ratio. The powder material is Sr x TiO ｚThe content of the element is preferably 90% to 100% in molar ratio of the total powder material, more preferably 95% to 100%, and even more preferably 99% to 100%. Whether or not a particular element is contained in the perovskite crystal can be analyzed by methods such as peak shift of diffraction lines by X-ray diffraction (XRD), structural analysis such as the Rietveld method, or X-ray absorption fine structure (EXAFS) analysis. The element content can also be measured by X-ray fluorescence analysis (XRF). The content of the main component can be evaluated by quantitative analysis using powder X-ray diffraction. The content of trace elements can also be measured by GDMS (glow discharge mass spectrometry).

[0015] Sr powder material x TiO ｚ In this formula, x represents the molar ratio of the Sr content, more specifically, the molar ratio of Sr content to Ti content. The value x is between 0.9 and 1.0, preferably between 0.95 and 1.0, and more preferably between 0.98 and 1.0. By having the value x within this range, an appropriate crystal structure can be achieved.

[0016] Sr powder material x TiO ｚ In this formula, z is a numerical value indicating the O content (molar ratio), and more specifically, it is the molar ratio of the O content to the Ti content. The numerical value z is derived from the chemical formula Sr x TiO ｚ This is a value that maintains overall charge neutrality, and for example, it could be 3.

[0017] The powder material is Sr x TiO ｚThe powder material may also contain auxiliary components other than those listed above. The powder material may contain Ge, Zr, Yb, and Gd as auxiliary components. The powder material may also contain the auxiliary components in the form of oxides or carbonates of the elements listed above. By introducing these auxiliary components, it is possible to adjust the sinterability while maintaining the transparency of the final material. The content of these auxiliary components is preferably 0% to 1% in molar ratio of the total powder material, more preferably 0% to 0.5%, and even more preferably 0% to 0.1%. By setting the content of the auxiliary components within this range, a ceramic material 10 with high refractive index and high transmittance can be appropriately manufactured. The content of the auxiliary components can be measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0018] In addition to the main and minor components described above, the powder material may contain any other components as unavoidable impurities. Preferably, the powder material is free of components other than the main and minor components, excluding unavoidable impurities.

[0019] The total content of Fe, Cr, and Ni in the powder material is preferably less than 20 ppm by mass, more preferably 10 ppm or less, and even more preferably 5 ppm or less, relative to the total mass of the powder material. The lower limit is not particularly limited, but the lower limit of the total content of Fe, Cr, and Ni is, for example, 0.5 ppm or more. Here, Fe, Cr, and Ni refer not only to the elemental metals of Fe, Cr, and Ni contained in the powder material, but may also include elemental metals of Fe, Cr, and Ni and compounds. In other words, the total content of Fe, Cr, and Ni can be said to include the content of elemental metals of Fe, Cr, and Ni and the content of Fe, Cr, and Ni ions in compounds. By keeping the total content of the colorable transition metals Fe, Cr, and Ni within this range, it is possible to manufacture ceramic materials that can appropriately transmit visible light. The total content of Fe, Cr, and Ni can be measured by ICP mass spectrometry. For example, the Agilent 8800 from Agilent Technologies can be used as a measuring instrument.

[0020] (Properties of powder materials) Next, we will explain the properties of powder materials.

[0021] (Average Primary Particle Size) The average primary particle size of the powder material is 50 nm to 500 nm, preferably 60 nm to 400 nm, more preferably 80 nm to 350 nm, and even more preferably 110 nm to 250 nm. The primary particle size refers to the particle size of a single particle of the powder material, and the average primary particle size refers to the average value of the primary particle sizes. By making the powder material such a size, it is possible to manufacture a ceramic material that can appropriately transmit visible light. The average primary particle size of the powder material can be evaluated by acquiring images with an electron microscope. For example, it can be measured using a field emission scanning electron microscope (JEOL: JSM-7800F).

[0022] (Cubicity) Figure 1A is a schematic diagram illustrating cubicity. The cubicity of the powder material is preferably 0.96 or less, more preferably 0.86 or more and 0.96 or less. The cubicity of the powder material is more preferably 0.86 or more and 0.95 or less, and even more preferably 0.93 or less. The cubicity of the powder material is even more preferably 0.93 or less, and even more preferably 0.86 or more and 0.93 or less. A cubicity of 0.86 or more is advantageous from the viewpoint of reaction efficiency because there are many reaction contact surfaces between the powder particles, and sintering is thought to proceed more easily. By using powder material with such cubicity, it is possible to increase the surface energy of the material and lower the sintering temperature, and ceramic material that can appropriately transmit visible light can be manufactured. The cubicity can be calculated by observing with FE-SEM, for example, and analyzing the observed image by the following method. SrTiO ３It is known that powders are most stable in a cubic shape that reflects the symmetry of the crystal, and as stability decreases, they change from a cubic shape. Depending on the manufacturing conditions such as firing, they can change to a rectangular parallelepiped shape, and further adjustments to the firing conditions and process conditions such as grinding can adjust the shape of the edges and vertices of the particles. Therefore, from the observed SEM image, a rectangular parallelepiped that circumscribes each primary particle powder (each particle P of the powder material) in such a way that the voids are minimized is drawn as the circumscribed rectangular parallelepiped C. For example, in this case, for the particle P shown in the 2D SEM image, a rectangle that circumscribes in such a way that the voids are minimized can be calculated, and a rectangular parallelepiped whose height is equal to the shorter side of the rectangle, with that rectangle as one face, can be used as the circumscribed rectangular parallelepiped C. Next, a right-angled triangular pyramid T is constructed at each corner of the circumscribed rectangular prism C, with the corners of the circumscribed rectangular prism C serving as the vertices of the pyramids, the triangular base touching the powder material particles P, and the three sides of the pyramids lying on the three faces of the circumscribed rectangular prism surrounding the corners of the circumscribed rectangular prism C. The sum of the volumes of each right-angled triangular pyramid T constructed for the powder material particles P is then calculated as the volume sum (or, a right-angled triangular pyramid T can be constructed at one corner, and its volume multiplied by eight is used as the volume sum). In this case, the ratio of the difference between the volume of the circumscribed rectangular prism C and the volume sum ((volume of circumscribed rectangular prism C - sum of volumes of right-angled triangular pyramid T) / (volume of circumscribed rectangular prism C)) is defined as the degree of cubicity for the particle P. In this method, the degree of cubicity is defined in the range of 0.83 to 1.00. Furthermore, to define the cubicness of a powder material as satisfying the above numerical range (for example, 0.96 or less), it may be necessary to randomly select multiple particles P contained in the powder material, calculate their cubicness, and define the top 20% of the cubicness values ​​among the selected particles P as the cubicness of the powder material.

[0023] (Specific surface area) The specific surface area of ​​powdered material is 5 m². ２ / g or more 18m ２ Preferably less than / g, and 5m ２ / g or more 16m ２ It is more preferable to have a value of 5m or less. ２ / g or more 14m ２ It is more preferable to have a value of 5m or less. ２ / g or more 10.0m ２A specific surface area of ​​less than or equal to / g is even more preferable. By using powder materials with such a specific surface area, the surface shape can be made more complex and the sinterability can be improved, making it possible to lower the sintering temperature and produce ceramic materials that can appropriately transmit visible light. The specific surface area of ​​the powder material is the BET specific surface area and can be measured using a specific surface area measuring device (Quantachrome: NOVA-TOUCH).

[0024] (50% particle size D ５０ ) 50% particle size D of powder material ５０ The particle size is preferably 200 nm to 3000 nm, more preferably 400 nm to 2600 nm, even more preferably 500 nm to 2400 nm, and still more preferably 800 nm to 2000 nm. By arranging the particle size distribution of the powder material in this way, the variation in particle size can be increased, improving sinterability, which in turn allows for a lower sintering temperature and enables the production of ceramic materials that can appropriately transmit visible light. 50% particle size D of the powder material ５０ This can be measured using a particle size distribution analyzer (Shimadzu Corporation: SALD-2300).

[0025] (Method for manufacturing powder materials) The method for manufacturing powder materials described above may be arbitrary, but one example is described below. Figure 1B is a flowchart for manufacturing powder materials.

[0026] (Preparation of raw materials) As shown in Figure 1B, in this manufacturing method, the raw materials for the powder material are prepared (step S10). In this step, as raw materials for the powder material, an Sr raw material, which is a powdered compound containing Sr, and a Ti raw material, which is a powdered compound containing Ti, are prepared. The Sr raw material may be any compound containing Sr, but an oxide of Sr or a carbonate of Sr is preferred, and a carbonate of Sr (for example, SrCO3) is preferred. ３ ) is more preferable. The Ti raw material can be any compound containing Ti, but an oxide of Ti (e.g., TiO) is more preferable. ｚ ) is preferable.

[0027] The average particle size of the Sr and Ti raw materials is preferably 1.0 μm or less, more preferably 0.05 μm to 0.9 μm, and even more preferably 0.08 μm to 0.8 μm. The average particle size can be measured by laser diffraction / scattering. Specifically, it can be measured using a particle size distribution analyzer (Shimadzu Corporation: SALD-2300).

[0028] (Calibration of raw materials) Next, the prepared raw materials are mixed and calcined to produce powdered raw materials (step S12).

[0029] In the calcination process, it is preferable to add water to the Sr and Ti raw materials to produce a slurry, and then add a dispersant to the slurry and mix to obtain a mixture to be calcined. It is preferable to use a polycarboxylate as the dispersant. When mixing, it is preferable to use a ball mill, and it is preferable to use alumina or zirconia balls. The mixing time is preferably 2 hours to 48 hours, more preferably 3 hours to 36 hours, and even more preferably 4 hours to 24 hours. By obtaining a mixture under the above conditions, the sinterability of the powder material can be increased, and a ceramic material that can appropriately transmit visible light can be manufactured.

[0030] In the calcination process, it is preferable to dry and crush the mixture obtained as described above, and then calcine it to obtain a powder material. The calcination temperature, which is the temperature at which the mixture is heated in the calcination process, is preferably 800°C to 1100°C, more preferably 820°C to 1070°C, and even more preferably 840°C to 1040°C. The calcination time, during which the mixture is held at the calcination temperature, is preferably 4 hours to 48 hours, more preferably 5 hours to 36 hours, and even more preferably 6 hours to 24 hours. Calcination is preferably carried out in an oxygen-containing atmosphere (for example, in an atmospheric atmosphere). By calcining under the above conditions, the sinterability of the powder material can be increased, and a ceramic material that can appropriately transmit visible light can be manufactured.

[0031] Furthermore, if the powder material contains auxiliary components, the auxiliary component raw materials may be mixed in addition to the Sr and Ti raw materials and then calcined, and the Sr obtained by calcination x TiOｚ Auxiliary components may be added.

[0032] (Ceramic Material) The ceramic material 10 manufactured using the powder material described above will now be explained.

[0033] 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 more preferably a polycrystalline ceramic sintered body. Although the ceramic material 10 according to this embodiment is a plate-shaped member, the shape of the ceramic material 10 is not limited to a plate and can be arbitrary. 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 optical members here include display devices. Even 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 use of the ceramic material 10 is arbitrary and is not limited to use as a light guide plate, nor is it limited to use in a head-mounted display. For example, ceramic material 10 is also useful for base substrates for growing other materials, transparent substrates for capacitive sensors for remote sensing, low-voltage driven electrostatic induction panel substrates, jewelry and furnishings, cover glass and housings for mobile terminals and wearable devices, interiors and non-contact panel covers for mobile bodies such as automobiles, dielectric antennas, window materials for surface microwave plasma generation, and droplet-controlled digital microfluidic substrates.

[0034] (A x１ BO ｚ１ ) The ceramic material 10 is A x１ BO ｚ１The ceramic material 10 contains a perovskite compound (oxide) represented by the chemical formula as its main component. That is, the main component compound is an oxide in which one or more types of element A are located at the A site in the perovskite structure, one or more types of element B are located at the B site in the perovskite structure, and O (oxygen element) is located at the O site in the perovskite structure. Here, "main component" may refer to a content of more than 50% in molar ratio of the ceramic material 10 as a whole. The ceramic material 10 contains the main component A x１ BO ｚ１ The content of is preferably 90% to 100% in molar ratio of the total ceramic material 10, and more preferably 95% to 100%. The content of the main component can be evaluated by quantitative analysis using powder X-ray diffraction. When element A contains two or more elements, one of those elements will be located at each A site in the perovskite structure, and the same applies to the subsequent explanation of B sites.

[0035] (Element A) (Main component) A x１ BO ｚ１ In this example, A is the element located at the A site in the perovskite structure. Element A is primarily composed of Sr. In other words, Sr is the main component among the elements located at the A site (the element with the highest content among the elements located at the A site).

[0036] A of ceramic material 10 x１ BO ｚ１ In this configuration, the ratio of the amount of Sr contained in element A to the total amount of each element A (each element located at site A) (amount of Sr / total amount of element A) is preferably 50% or more in molar terms, preferably 95% or more and 100%, and more preferably 99.9% or more and 100% or less. When the amount of Sr contained in site A is within this range, it becomes possible to appropriately transmit visible light and also to appropriately refract visible light.

[0037] (Rare Earth Elements) Element A may contain rare earth elements as substitutional components. The rare earth elements contained in element A are preferably at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, more preferably at least one of La, Sm, Eu, Gd, Tb, Ho, Yb, and Lu, and more preferably at least one of La, Sm, Gd, Tb, Yb, and Lu. The inclusion of such rare earth elements in element A improves sinterability, making it possible to appropriately transmit visible light and to appropriately refract visible light.

[0038] A of ceramic material 10 x１ BO ｚ１ In this configuration, the ratio of the amount of rare earth elements contained in element A (rare earth elements located at site A) to the total amount of each element A (each element located at site A) (amount of rare earth elements / total amount of element A) is preferably 0% to 2.0% in molar ratio, more preferably 0% to 1.5%, and even more preferably 0% to 1%. When the amount of rare earth elements contained at site A is within this range, it becomes possible to appropriately transmit visible light and to appropriately refract visible light. Note that, if element A contains multiple types of rare earth elements, the amount of rare earth elements contained in element A here refers to the total amount of those rare earth elements.

[0039] (Other components) A of ceramic material 10 x１ BO ｚ１ In this, element A may contain elements other than alkaline earth metal elements and rare earth elements as other components (modifying agents). Examples of other components include at least one of Na, K, and Bi.

[0040] (Element B) (Main component) A x１ BO ｚ１ In this example, B is the element located at the B site in the perovskite structure. Element B is primarily composed of Ti. In other words, Ti is the main component among the elements located at the B site (the element with the highest content among the elements located at the B site).

[0041] A of ceramic material 10 x１ BO ｚ１ In this configuration, the ratio of the amount of Ti contained in element B (Ti located at the B site) to the total amount of each element B (each element located at the B site) (amount of Ti / total amount of element B) is preferably 50% or more in molar terms, preferably 90% or more and 100%, and more preferably 99.9% or more and 100% or less. When the amount of Ti contained in the B site is within this range, it becomes possible to appropriately transmit visible light and also to appropriately refract visible light.

[0042] (Rare Earth Elements) Element B may contain rare earth elements as substitutional components. The rare earth elements contained in element B are preferably at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and more preferably at least one of La, Sm, Eu, Gd, Tb, Ho, Yb, and Lu, and more preferably Sm, Gd, Tb, Yb, and Lu. The inclusion of such rare earth elements in element B improves sinterability, making it possible to appropriately transmit visible light and to appropriately refract visible light.

[0043] A of ceramic material 10 x１ BO ｚ１ In this configuration, the ratio of the amount of rare earth elements contained in element B (rare earth elements located at the B site) to the total amount of each element B (each element located at the B site) (amount of rare earth elements / total amount of element B) is preferably 0% to 2.0% in molar ratio, more preferably 0% to 1.5%, and even more preferably 0% to 1.0%. When the amount of rare earth elements contained at the B site falls within this range, it becomes possible to appropriately transmit visible light and to appropriately refract visible light. Note that, if element B contains multiple types of rare earth elements, the amount of rare earth elements contained in element B here refers to the total amount of those rare earth elements.

[0044] (Other components) A of ceramic material 10 x１ BO ｚ１In this, element B may contain elements other than Ti and rare earth elements as other components (modifying agents). Examples of other components include at least one of Zr, Ge, Zn, Sc, Y, Ga, Si, Sn, Nb, Ta, Hf, and Al.

[0045] (Value x 1) A of ceramic material 10 x１ BO ｚ１ In this equation, x1 is a numerical value that indicates the ratio (molar ratio) of the content of element A, or more specifically, the molar ratio of the content of element A to the content of element B. Here, the content of element A refers to the total content of all elements if element A contains multiple types of elements, and similarly, the content of element B refers to the total content of all elements if element B contains multiple types of elements.

[0046] The numerical value x1 is between 0.9 and 1.0, preferably between 0.95 and 1.0, and more preferably between 0.98 and 1.0. A suitable crystal structure can be achieved when the numerical value x1 falls within this range.

[0047] (Value z1) A of ceramic material 10 x１ BO ｚ１ In this equation, z1 is a numerical value that indicates the content (molar ratio) of O, or more specifically, the molar ratio of the O content to the content of element B. The numerical value z1 is the value of chemical formula A x１ BO ｚ１ This is a value that maintains overall charge neutrality, and for example, it could be 3.

[0048] (Minor component) The ceramic material 10 is the main component A mentioned above. x１ BO ｚ１The ceramic material 10 may also contain auxiliary components other than those listed above. The ceramic material 10 preferably contains at least one element selected from Li, Si, B, Y, Al, Ca, and Mg as an auxiliary component, and more preferably contains Si. This auxiliary component originates from the sintering aid used when sintering the raw materials to form the ceramic material 10. The ceramic material 10 may also contain the auxiliary component in the form of oxides or carbonates of the elements listed above. The content of this 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, in molar ratio relative to the total ceramic material 10. By setting the auxiliary component content within this range, a ceramic material 10 with high refractive index and high transmittance can be appropriately manufactured. The content of the auxiliary component can be measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0049] The ceramic material 10 may contain auxiliary components other than those derived from the sintering aid. If the auxiliary components other than those derived from the sintering aid are considered auxiliary components, it is preferable that the ceramic material 10 contains at least one selected from Ce and Pr as an auxiliary component. By including such an auxiliary component, the auxiliary component can function as an oxidizing agent, appropriately receiving electrons and more favorably suppressing the decrease in transmittance. The ceramic material 10 may also contain the auxiliary component in the form of an oxide of the elements listed above. 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, in molar ratio relative to the total amount of the ceramic material 10. By setting the content of the auxiliary component within this range, a ceramic material 10 with high refractive index and high transmittance can be appropriately manufactured. The content of the auxiliary component can also be measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0050] In addition to the main component, minor component, and auxiliary component described above, the ceramic material 10 may also contain any other components as unavoidable impurities. Preferably, the ceramic material 10 does not contain any components other than the main component, minor component, and auxiliary component, excluding unavoidable impurities.

[0051] (Properties of ceramic material) Next, the properties of the ceramic material 10 will be described.

[0052] (Internal Transmittance) The ceramic material 10 has an internal total light transmittance of 50% or more for light with a wavelength of 635 nm at a thickness of 1 mm, preferably 60% to 100%, and more preferably 70% to 100%. The internal total light transmittance at a thickness of 1 mm can be measured by using a spectrophotometer (PerkinElmer; LAMBDA950) with an integrating sphere unit (150 mm InGaAs Int. Sptere) as a detector, and bringing the ceramic material 10 into close contact with the integrating sphere. If the actual thickness of the ceramic material 10 is not 1 mm, the measured value can be used to convert it to the total light transmittance equivalent to a thickness of 1 mm using the Lambert-Beer law. If the plate thickness t is greater than 1 mm, the plate thickness of the ceramic material 10 may be adjusted to 1 mm by polishing or etching before measurement. The total light transmittance is determined by the composition of the ceramic material 10, but even with the same composition, it may differ depending on the manufacturing process of the ceramic material 10. Therefore, by manufacturing the ceramic material 10 using, for example, the manufacturing method described later, the total internal light transmittance can be set to the above range. The internal transmittance can be calculated using the measured values ​​T1 and reflectance R of two types of external transmittances with different plate thicknesses in the following procedure. Note that external transmittance means transmittance including surface reflection loss. The converted internal transmittance can be calculated as follows. When the refractive index at 635 nm is n, equation (n-1) ２ / (n+1) ２The reflectance at the incident surface is calculated, and the theoretical transmittance T0 is obtained by subtracting twice the reflectance from 1, so the internal transmittance is T2 = T1 / T0. The apparent absorption coefficient α (cm) is obtained by taking the natural logarithm of the internal transmittance T2, adding a negative sign, and dividing by the sample thickness (in cm). －１ The apparent absorption coefficient can be calculated by multiplying it by 0.1 (cm), adding a negative sign, and taking an exponent with base e, which can be evaluated as the converted internal transmittance T3 (%) for a 1 mm thickness. External transmittance can be measured using a spectrophotometer (Hitachi High-Technologies Corporation: U-4100) on a sample with a plate thickness of 0.5 mm to 10 mm that has been mirror-polished on both sides. Alternatively, the converted internal transmittance may be evaluated by 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 parallel plate of ceramics, and a Si photodetector is placed at a distance of 20 cm from the sample on the side facing the light source. The transmittance T1' is taken from the ratio of the light intensity received by the Si photodetector to the output of the incident light source, and the natural logarithm of T2' = T1' / T0 is taken and added a negative sign, and divided by the sample thickness (in cm) to obtain the apparent absorption coefficient α'(cm －１ The following can be calculated: The apparent absorption coefficient is multiplied by 0.1 (cm), a negative sign is added, and an exponent with base e is taken to obtain the converted internal transmittance T3' for a 1 mm thickness, which can then be evaluated as the converted internal transmittance. Note that the sample polished surface is sufficiently large relative to the laser spot diameter, typically around 1 cm.

[0053] (Refractive Index) The ceramic material 10 preferably has a refractive index of 2.30 or higher for light with a wavelength of 635 nm, more preferably 2.30 or higher and 2.45 or lower, and even more preferably 2.35 or higher and 2.40 or lower. A refractive index within this range allows for appropriate refraction of visible light. The refractive index can be measured by spectroscopic ellipsometry (JAWoollam Co., Inc.; M-2000 DI).

[0054] (Average particle size) A is a perovskite compound of the ceramic material 10. x１ BO ｚ１The average particle size of each particle is preferably 2 μm to 100 μm, more preferably 2 μm to 80 μm, and even more preferably 2 μm to 50 μm. This average particle size range allows for the transmission of visible light while appropriately refracting it. The average particle size can be measured as follows: The surface of the ceramic material 10 is mirror-polished with a grinding wheel of grit size #30000 as specified in JIS R6001, and the mirror-polished ceramic material is heat-treated at (sintering temperature - 100) °C (1350 °C if the sintering temperature is unknown) for 30 minutes. Ten images of the surface of the heat-treated ceramic material 10 are acquired using a scanning electron microscope (SEM) at an appropriate magnification (for example, a magnification that captures 10 to 50 particles (entire particle area) within the imaging range), and the total particle area included in each image is measured. Then, the diameter of each particle is calculated from its area, assuming it is circular. This calculated diameter is then defined as the particle size, and the average of the particle sizes is defined as the average particle size.

[0055] (Number of pores) 1 mm of ceramic material 10 ３ The number of pores with a radius of 5 μm or more per unit area is preferably 0 to 520, more preferably 0 to 50, and even more preferably 0 to 10. Having a pore count within this range allows for the transmission of visible light while appropriately refracting it. The number of pores can be measured as follows: The central part of the ceramic material 10 is cut to a size of 1 mm (length) x 1 mm (width) x 10 mm (height), and a cross-section perpendicular to the height direction is measured using X-ray Computer Tomography (X-ray CT) with a voxel size of 1.7 μm using a Bruker SkyScan 2214. A single-layer cross-sectional image is obtained using a Bruker NRecon. Then, while shifting the imaging height, the obtained three-dimensional images are analyzed using a Bruker CTAN, and the number of pores with a radius of 5 μm or more is determined per unit area. ３ Converting this to a per-unit rate gives the number of pores per unit area.

[0056] (Method for manufacturing ceramic material) The ceramic material 10 according to this embodiment may be manufactured by any method, but it is preferably manufactured by a solid-phase method, and an example of such a manufacturing method is described below. Figure 2 is a flowchart showing the method for manufacturing the ceramic material according to this embodiment.

[0057] (Molding of powder material) As shown in Figure 2, in this manufacturing method, the powder material is molded to obtain a molded body 10a (step S20). That is, the molded body 10a is made of Sr x TiO ｚ It can be described as a molded body of powder material with as its main component. The size and shape of the molded body 10a are set in accordance with the size and shape of the ceramic material 10 to be obtained. The molding conditions for the molded body 10a may be arbitrary, and for example, CIP (Cold Isostatic Pressing) molding may be used.

[0058] If the A site or B site of the ceramic material 10 contains rare earth elements as substitution components, the powdered substitution raw material, which is the raw material for the substitution component, is mixed with the powder material and molded. The substitution raw material may be an oxide of a rare earth element.

[0059] If the ceramic material 10 contains auxiliary components, the powdered auxiliary material that serves as the raw material for the auxiliary components of the ceramic material 10 is mixed together with the powder material and molded. The auxiliary material is a material containing elements included in the auxiliary components of the ceramic material 10, and is a so-called sintering aid. The auxiliary material may be any material containing elements included in the auxiliary components of the ceramic material 10. As an auxiliary material, oxides of elements included in the auxiliary components (for example, Li ２ O, SiO ２ , B ２ O ３ Fluorides of elements contained in the minor components (e.g., LiF, MgF) ２ (e.g., carbonates of elements included in the minor components (e.g., Li) ２ CO ３ Examples include:

[0060] If the ceramic material 10 contains auxiliary components, the powdered auxiliary raw materials that serve as the raw materials for the auxiliary components of the ceramic material 10 are mixed together with the powdered material and molded. The auxiliary raw materials are materials containing elements included in the auxiliary components of the ceramic material 10, and are so-called oxidizing agents. The auxiliary raw materials may be any materials containing elements included in the auxiliary components of the ceramic material 10. As auxiliary raw materials, oxides of elements included in the auxiliary components (for example, CeO) ２ , Pr ６ O １１ Examples include:

[0061] (Primary Sintering) Next, the obtained molded body 10a is subjected to primary sintering to obtain a primary sintered body 10b (step S22). That is, the primary sintered body 10b is a sintered body obtained by subjecting the molded body 10a to primary sintering treatment.

[0062] Figure 3 is a schematic diagram of a furnace used for primary sintering. As shown in Figure 3, in this manufacturing method, the molded body 10a is placed in the furnace F and the furnace F is heated to perform primary sintering of the molded body 10a.

[0063] The primary sintering temperature, which is the temperature at which the molded body 10a is heated in the primary sintering process (temperature inside the furnace F), is preferably 1200°C to 1450°C, more preferably 1250°C to 1420°C, and even more preferably 1300°C to 1400°C. The heating rate (temperature increase inside the furnace F) when raising the temperature of the molded body 10a to the primary sintering temperature in the primary sintering process is preferably 300°C / h or less, more preferably 30°C / h to 200°C / h, and even more preferably 50°C / h to 150°C / h. The primary sintering time, during which the molded body 10a (inside the furnace F) is held at the primary sintering temperature, is preferably 2 hours to 72 hours, more preferably 4 hours to 48 hours, and even more preferably 6 hours to 36 hours. Primary sintering may be carried out under any atmosphere, but it is preferably carried out under an oxygen atmosphere (e.g., an atmospheric atmosphere) or a vacuum atmosphere (e.g., a total pressure of less than 10 Pa). Furthermore, the pressure (pressure inside the furnace F) during primary sintering can be arbitrary, but in the case of an oxygen atmosphere, it may be set to 1 atm or more and 5 atm or less. By performing primary sintering under these conditions, a ceramic material 10 that can appropriately transmit visible light can be manufactured.

[0064] Furthermore, in this manufacturing method, it is preferable to perform primary sintering in the furnace F with the molded body 10a placed on the base portion A1. That is, it is preferable that the molded body 10a is in contact with the base portion A1 without contacting the inner surface Fa of the furnace F during primary sintering. The base portion A1 is made of a material with a thermal conductivity of 5 W / m / K or more and 60 W / m / K or less, and may be made of alumina, for example. The shape of the base portion A1 may be arbitrary, but may be plate-shaped, for example. In this case, the entire surface of the molded body 10a on the base portion A1 side may be in contact with the base portion A1. By performing primary sintering in this state of contact with the base portion A1, cracking can be suppressed during sintering, and a ceramic material 10 that can appropriately transmit visible light can be manufactured.

[0065] (Relative density after primary sintering) The relative density of the ceramic material 10 after primary sintering, i.e., the relative density of the primary sintered body 10b, is preferably 95% to 100%, more preferably 97% to 100%, and even more preferably 99% to 100%. Having a relative density of the primary sintered body 10b within this range allows for appropriate transmission of visible light through subsequent HIP and post-annealing processes. The relative density is expressed as bulk density ρb (g / cm³). ３ ) and true density ρs (g / cm³) ３ The following formula can be used to calculate the relative density (%): Relative density (%) = bulk density ρb / true density ρs × 100 The bulk density can be measured according to the method for measuring the apparent density, bulk density and open porosity of sintered fine ceramics (JIS R1634:1998). The true density can be calculated from the addition ratio of raw materials (powder materials, sintering aids, etc.) to the molded body of ceramic material 10.

[0066] (HIP) Next, the obtained primary sintered body 10b is subjected to HIP (Hot Isostatic Pressing) treatment to obtain a secondary sintered body 10c (step S24). That is, the secondary sintered body 10c is a sintered body obtained by subjecting the primary sintered body 10b to HIP treatment.

[0067] Figure 4 is a schematic diagram of a furnace used for HIP treatment. As shown in Figure 4, in this manufacturing method, the molded body 10a is placed in the furnace F, and the primary sintered body 10b is subjected to HIP treatment by heating the furnace F under pressure. The furnace F used for HIP treatment may be the same furnace F used for primary sintering, or it may be a different furnace.

[0068] The pressure applied to the primary sintered body 10b during the HIP treatment (pressure inside the furnace F) is preferably 100 MPa or more, more preferably 110 MPa to 190 MPa, and even more preferably 120 MPa to 180 MPa. The HIP temperature, which is the temperature at which the primary sintered body 10b is heated during the HIP treatment (temperature inside the furnace F), is preferably 1150°C to 1450°C, more preferably 1200°C to 1400°C, and even more preferably 1250°C to 1350°C. By setting the HIP treatment temperature to 1350°C or lower, the reduction of the material can be suppressed as much as possible, and the subsequent post-annealing process can efficiently restore the color. The heating rate (heating temperature in the furnace F) when raising the primary sintered body 10b to the HIP temperature during the HIP treatment is preferably 400°C / h or less, more preferably 100°C / h to 380°C / h, and even more preferably 150°C / h to 370°C / h. The HIP time for holding the primary sintered body 10b (inside the furnace F) at the HIP temperature is preferably 0.5 hours to 8 hours, more preferably 0.5 hours to 6 hours, and even more preferably 1 hour to 4 hours. The HIP treatment may be carried out under any atmosphere, but it may be carried out under an oxygen atmosphere (for example, an atmospheric atmosphere) or under an Ar-containing atmosphere (for example, an Ar atmosphere, or a mixed atmosphere of Ar and oxygen). By performing the HIP treatment under the above conditions, a ceramic material 10 that can appropriately transmit visible light can be manufactured.

[0069] Furthermore, in this manufacturing method, it is preferable to perform HIP treatment in the furnace F with the primary sintered body 10b placed on the base portion A2. That is, it is preferable that the primary sintered body 10b is in contact with the base portion A2 without contacting the inner surface Fa of the furnace F while undergoing HIP treatment. The base portion A2 is made of a material with a thermal conductivity of 5 W / m / K or more and 60 W / m / K or less, and may be made of alumina, for example. It is also preferable that the base portion A2 contacts only a part of the surface of the primary sintered body 10b on the base portion A2 side. In other words, it is preferable that the surface of the primary sintered body 10b on the base portion A2 side is in contact with the base portion A2 in a part of the area, and the remaining area is open in the furnace F (not in contact with other members). This allows the primary sintered body 10b to be uniformly pressed, suppressing cracking and enabling the production of the ceramic material 10. The base portion A2 may have any shape that contacts only a part of the surface of the primary sintered body 10b, but for example, it may be composed of multiple spherical members or multiple columnar members. This allows the surface of the primary sintered body 10b to be appropriately open between the spherical or columnar members.

[0070] (Post-annealing) Next, the obtained secondary sintered body 10c is subjected to post-annealing treatment to obtain the ceramic material 10 (step S26).

[0071] Figure 5 is a schematic diagram of a furnace used for post-annealing. As shown in Figure 5, in this manufacturing method, the secondary sintered body 10c is placed in the furnace F and the inside of the furnace F is heated to perform post-annealing on the secondary sintered body 10c. The furnace F used for post-annealing may be the same furnace F used for primary sintering or HIP treatment, or it may be a different furnace.

[0072] The annealing temperature, which is the temperature at which the secondary sintered body 10c is heated in the post-annealing process (temperature inside the furnace F), is preferably 700°C to 1400°C, more preferably 750°C to 1270°C, and even more preferably 800°C to 1250°C. The heating rate (temperature increase inside the furnace F) when raising the secondary sintered body 10c to the annealing temperature in the post-annealing process is preferably 200°C / h or less, more preferably 150°C / h to 200°C / h, and even more preferably 100°C / h to 200°C / h. The annealing time, during which the secondary sintered body 10c (inside the furnace F) is held at the annealing temperature, is preferably 5 hours to 120 hours, more preferably 6 hours to 96 hours, and even more preferably 7 hours to 72 hours. The post-annealing treatment may be carried out under any atmosphere, but it may be carried out under an oxygen atmosphere (for example, an atmospheric atmosphere) or under an atmosphere containing Ar (for example, an Ar atmosphere, or a mixed atmosphere of Ar and oxygen). The pressure applied to the secondary sintered body 10c during the post-annealing treatment (pressure inside the furnace F) may be arbitrary, but it may be set to 1 atm or more and 5 atm or less. By performing the post-annealing treatment under the above conditions, even large molded bodies 10a can be sintered while suppressing cracking, so that a highly versatile ceramic material 10 can be manufactured while appropriately transmitting visible light.

[0073] Also, in this manufacturing method, it is preferable to perform post-annealing on the secondary sintered body 10c while it is placed on the base portion A3 inside the furnace F. That is, the secondary sintered body 10c is preferably post-annealed in a state of contacting the base portion A3 without contacting the inner surface Fa of the furnace F. The base portion A3 is made of a material having a thermal conductivity of 5 W / m / K or more and 60 W / m / K or less, and may be made of, for example, alumina. Further, the base portion A3 preferably contacts only a part of the surface of the secondary sintered body 10c on the base portion A3 side. In other words, the surface of the secondary sintered body 10c on the base portion A3 side preferably contacts the base portion A3 in a partial region, and the remaining region is open (not in contact with other members) inside the furnace F. Thereby, the ceramics material 10 can be manufactured while suppressing cracking. Note that the base portion A3 may have any shape that contacts only a part of the surface of the secondary sintered body 10c. For example, it may be composed of a plurality of spherical members or a plurality of columnar members. Thereby, the surface of the secondary sintered body 10c can be appropriately opened between the spherical or columnar members.

[0074] (Total heating time) Here, the time during which the green compact 10a is exposed to a temperature of 1000°C or higher from the green compact 10a until the ceramics material 10 is manufactured is defined as the total heating time. That is, for example, the total time of the time reaching 1000°C or higher during primary sintering, the time reaching 1000°C or higher during HIP, and the time reaching 1000°C or higher during post-annealing can be said to be the total heating time. In this case, the total heating time is preferably 124 hours or less, more preferably 24 hours or more and 100 hours or less, and even more preferably 30 hours or more and 76 hours or less. By setting the total heating time within this range, coloring due to excessive defects in the ceramics material 10 can be suppressed, and a ceramics material 10 that can appropriately transmit visible light can be manufactured.

[0075] (Effect) As described above, the powder material according to the first aspect of the present disclosure has an average primary particle size of 50 nm or more and 500 nm or less, a cubicity of 0.96 or less, and Sr x TiO ｚTaking [the main component], x is 0.9 or more and 1.0 or less, and z is a numerical value that satisfies the charge neutrality of the entire chemical formula. According to the present disclosure, since the surface shape can be made complex to improve the sinterability, the sintering temperature can be lowered, and a ceramic material that can appropriately transmit visible light can be manufactured.

[0076] The powder material according to the second aspect of the present disclosure is the powder material of the first aspect, and the cubicity is 0.93 or less. According to the present disclosure, a ceramic material that can appropriately transmit visible light can be manufactured.

[0077] The powder material according to the third aspect of the present disclosure has an average primary particle size of 50 nm or more and 500 nm or less, and a specific surface area of 5 m ２ / g or more and 18 m ２ / g or less, taking Sr x TiO ｚ as the main component, x is 0.9 or more and 1.0 or less, and z is a numerical value that satisfies the charge neutrality of the entire chemical formula. According to the present disclosure, since the surface shape can be made complex to improve the sinterability, the sintering temperature can be lowered, and a ceramic material that can appropriately transmit visible light can be manufactured.

[0078] The powder material according to the fourth aspect of the present disclosure is the powder material of the third aspect, and the specific surface area is 5 m ２ / g or more and 14 m ２ / g or less. According to the present disclosure, a ceramic material that can appropriately transmit visible light can be manufactured.

[0079] The powder material according to the fifth aspect of the present disclosure is the powder material according to any one of the first aspect to the fourth aspect, and x is 0.98 or more and 1.0 or less. According to the present disclosure, a ceramic material that can appropriately transmit visible light can be manufactured.

[0080] The powder material according to the sixth aspect of the present disclosure is the powder material according to any one of the first aspect to the fifth aspect, and the average primary particle size is 80 nm or more and 350 nm or less. According to the present disclosure, a ceramic material that can appropriately transmit visible light can be manufactured.

[0081] The powder material according to the seventh aspect of the present disclosure is the powder material according to any one of the first aspect to the sixth aspect, and the 50% particle size D ５０However, the wavelength is between 200 nm and 3000 nm. According to this disclosure, the sinterability can be improved by making the surface shape complex, which makes it possible to lower the sintering temperature and produce a ceramic material that can appropriately transmit visible light.

[0082] The powder material relating to the eighth aspect of this disclosure is the powder material of any of the first to seventh aspects, wherein the 50% particle size D ５０ However, the wavelength range is between 500 nm and 2400 nm. According to this disclosure, it is possible to manufacture ceramic materials that can appropriately transmit visible light.

[0083] The powder material according to the ninth aspect of this disclosure is the powder material according to any of the first to eighth aspects, wherein the total content of Fe, Cr, and Ni is less than 20 ppm by mass ratio. According to this disclosure, it is possible to manufacture a ceramic material that can appropriately transmit visible light.

[0084] The ceramic material according to the tenth aspect of this disclosure is a sintered body of any of the powder materials of the first to ninth aspects, wherein the total light internal transmittance for light with a wavelength of 635 nm at a thickness of 1 mm is 70% or more and 100% or less, and the refractive index for light with a wavelength of 635 nm is 2.35 or more and 2.40 or less. According to this disclosure, visible light can be appropriately transmitted.

[0085] A method for manufacturing a ceramic material according to the eleventh aspect of this disclosure involves manufacturing a ceramic material by sintering a powder material according to any of the first to ninth aspects. According to this disclosure, a ceramic material capable of appropriately transmitting visible light can be manufactured.

[0086] A method for manufacturing a ceramic material according to a twelfth aspect of this disclosure is a manufacturing method according to an eleventh aspect, comprising: molding a powder material; performing a primary sintering treatment on the molded powder material by heating it to a sintering temperature of 1200°C to 1450°C to obtain a primary sintered body; performing a HIP treatment on the primary sintered body by heating it to a temperature of 1150°C to 1450°C under conditions of 100 MPa or more; and performing a post-annealing treatment on the secondary sintered body, which is the primary sintered body that has undergone HIP treatment, by heating it to a sintering temperature of 700°C to 1400°C to obtain a ceramic material. According to this disclosure, a ceramic material that can appropriately transmit visible light can be manufactured.

[0087] A method for manufacturing a ceramic material according to a thirteenth aspect of this disclosure is a manufacturing method according to a twelfth aspect, which includes primary sintering of a molded body, which is a molded powder material, while it is placed on a base, HIP treatment of the primary sintered body while it is placed on the base, and post-annealing treatment of the secondary sintered body while it is placed on the base. According to this disclosure, a ceramic material that can appropriately transmit visible light can be manufactured.

[0088] (Examples) Next, examples will be described. The embodiments may be modified as long as the effects of the invention are achieved. Table 1 shows the powder materials for each example and their evaluation results.

[0089]

[0090] (Example 1) In Example 1, strontium carbonate powder as the Sr raw material and titanium oxide powder as the Ti raw material are used in a stoichiometric ratio as SrTiO ３ The compounds were mixed in the following proportions. The measurements were taken using the method described in the above embodiment. The mixed compounds were wet-mixed using zirconia balls as the grinding media under ball mill mixing conditions for 4 hours, the mixture was dried under conditions of holding at 80°C for 10 hours, and the dried mixture was calcined under conditions of holding at 1000°C for 10 hours to obtain SrTiO ３ A powder material was obtained. The average primary particle size, specific surface area, cubicity, and D of the obtained powder material were determined. ５０ The total content of Fe, Cr, and Ni was measured using the method described in this embodiment. The measurement results are shown in Table 1. The obtained powder was processed using a uniaxial press and CIP method, and the main surface area was 8 cm². ２A disc-shaped molded body with a thickness of 5 mm was obtained. The obtained molded body was placed on a base made of alumina plate (with the entire surface of the molded body in contact with the alumina plate) and subjected to primary sintering treatment under the conditions of an oxygen atmosphere of 2 atm, a heating rate of 100°C / h, a primary sintering temperature of 1350°C, and a holding time (primary sintering time) of 2 hours to obtain a primary sintered body. The relative density of the obtained primary sintered body was measured using the method described in this embodiment. The obtained primary sintered body was placed on a base made of multiple alumina balls (with only a portion of the primary sintered body in contact with the alumina) and subjected to HIP treatment under the conditions of an Ar atmosphere, an applied pressure of 150 MPa, a HIP temperature of 1300°C, and a holding time (HIP time) of 1 hour to obtain a secondary sintered body. The obtained secondary sintered body was placed on a base plate covered with multiple alumina balls (so that only a portion of the secondary sintered body was in contact with the alumina), and post-annealing treatment was performed in an atmospheric atmosphere under the following conditions: heating rate of 200°C / h, annealing temperature of 1000°C, and holding time (annealing time) of 10 hours to obtain a ceramic material. The obtained ceramic material has the chemical formula SrTiO ３ A sintered body of a perovskite crystal with the composition represented by [formula] was obtained.

[0091] The relative density, transmittance (total light transmittance at a 1 mm thickness) for light with a wavelength of 635 nm, refractive index for light with a wavelength of 635 nm, and resistivity of the ceramic material in Example 1 were measured using the method described in this embodiment. The measurement results are shown in Table 1.

[0092] (Examples 2 to 9) In Examples 2 to 9, the ceramic material was manufactured using the same method as in Example 1, except that the manufacturing conditions were as shown in Table 1. The measurement results for each example are also shown in Table 1.

[0093] (Evaluation) The transmittance of visible light was evaluated for each example of ceramic material. In the evaluation of transmittance, a transmittance of 90% or more for light with a wavelength of 635 nm (total light transmittance at a thickness of 1 mm) was marked as ○, 50% or more but less than 90% was marked as △, and less than 50% was marked as ×.

[0094] As shown in Table 1, in Examples 1-4 and 8, which are embodiments, the transmittance evaluation is ○ or △, indicating that visible light can be transmitted appropriately. On the other hand, in Examples 5-7 and 9, which are comparative examples, the transmittance evaluation is ×, indicating that visible light cannot be transmitted appropriately.

[0095] Although embodiments of the present disclosure have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above.

[0096] 10. Ceramic Materials

Claims

1. The average primary particle size is 50 nm or more and 500 nm or less, the cubicness is 0.96 or less, and Sr x TiO ｚ A powder material having as its main component, wherein x is between 0.9 and 1.0, and z is a value that maintains charge neutrality for the entire chemical formula.

2. The powder material according to claim 1, wherein the degree of cubicity is 0.93 or less.

3. The average primary particle size is between 50 nm and 500 nm, and the specific surface area is 5 m². ２ / g or more 18m ２ / g or less, Sr x TiO ｚ A powder material having as its main component, wherein x is between 0.9 and 1.0, and z is a value that maintains charge neutrality for the entire chemical formula.

4. The specific surface area is 5 m² ２ / g or more 14m ２ The powder material according to claim 3, wherein the amount is less than or equal to / g.

5. The powder material according to any one of claims 1 to 4, wherein x is 0.98 or more and 1.0 or less.

6. The powder material according to any one of claims 1 to 4, wherein the average primary particle size is 80 nm or more and 350 nm or less.

7. The particle size D of 50% ５０ is 200 nm or more and 3000 nm or less, and the powder material according to any one of claims 1 to 4.

8. 50% particle size D ５０ The powder material according to any one of claims 1 to 4, wherein the wavelength is between 500 nm and 2400 nm.

9. The powder material according to any one of claims 1 to 4, wherein the total content of Fe, Cr, and Ni is less than 20 ppm by mass ratio.

10. A sintered body of a powder material according to any one of claims 1 to 4, wherein the total light internal transmittance of a 1 mm thickness for light with a wavelength of 635 nm is 70% or more and 100% or less, and the refractive index for light with a wavelength of 635 nm is 2.35 or more and 2.40 or less, and the ceramic material.

11. A method for producing a ceramic material, comprising sintering a powder material according to any one of claims 1 to 4.

12. A method for producing a ceramic material according to claim 11, comprising: molding the powder material; performing a primary sintering treatment on the molded powder material by heating it to a sintering temperature of 1200°C to 1450°C to obtain a primary sintered body; performing a HIP treatment on the primary sintered body by heating it to a temperature of 1150°C to 1450°C under conditions of 100 MPa or more; and performing a post-annealing treatment on the secondary sintered body, which is the primary sintered body that has been HIP treated, by heating it to a sintering temperature of 700°C to 1400°C to obtain a ceramic material.

13. A method for manufacturing a ceramic material according to claim 12, comprising: primary sintering a molded body, which is the molded powder material, while it is placed on a base; HIP treatment while the primary sintered body is placed on the base; and post-annealing treatment while the secondary sintered body is placed on the base.

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