Blue light-emitting transparent sialon ceramics and its manufacturing method

Abstract

To provide blue light-emitting transparent sialon ceramics that are transparent and blue fluorescent, and can increase the productivity while having durability comparable to or higher than the prior art.SOLUTION: Such blue light-emitting transparent sialon ceramics have a main phase of α-sialon having general formula Mx(Si,Al)12(N,O)16 (where M is at least one selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium and lutetium, and 0.3≤x≤1) in which some M are substituted with Ce, so that a luminescent center ion is at least Ce3+.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to blue-emitting transparent SiAlON ceramics and methods for making the same. [Background technology]

[0002] With the practical application of blue light-emitting diodes (LEDs), the development of white LEDs utilizing these blue LEDs has been vigorously pursued. Compared to existing white light sources, white LEDs have lower power consumption and a longer lifespan, making them useful for backlights for liquid crystal displays, indoor and outdoor lighting equipment, and the like. For example, one white LED has a powdered phosphor dispersed in a resin, which is then fixed to the surface of a blue LED (see, for example, Patent Document 1). The present inventors recently proposed transparent bulk bodies, such as Eu-β-sialon phosphor ceramics and Y-α-sialon phosphor ceramics, made of nitride ceramic phosphors that can be used in white LEDs by molding the ceramic phosphors themselves into a predetermined shape (Patent Document 2).

[0003] Although its fluorescence has not been investigated, Lu-α-sialon ceramics with excellent transparency in the visible light range have been reported (Non-Patent Document 1), which were obtained by hot pressing a mixture of Si3N4, Lu2O3, AlN, and Al2O3 in a nitrogen atmosphere at 1950°C for 2 hours. The present inventors have also reported highly transparent Lu-α-sialon ceramics in which α-sialon is the main phase and β-sialon and J phases are present as secondary phases (Non-Patent Document 2). In addition, Ho-α-sialon ceramics with a high α-sialon ratio and high relative density (Non-Patent Document 3) have been reported. 3+ of 5 I6→ 5 I8 (1195 nm) 5 F5 → 5 It was reported that the fluorescence was thought to be due to the ff transition between the I7 (985 nm) levels (Non-Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-173868 [Patent Document 2] International Publication No. 2015 / 133612 [Non-patent literature]

[0005] [Non-Patent Document 1] MI Jones, etal., Highly transparent Lu-α-SiAlON, J. Am. Ceram. Soc., 87, 714-716 (2004) [Non-patent document 2] Proceedings of the 2020 Annual Meeting of the Ceramic Society of Japan, 1P010 (2020) [Non-patent document 3] Proceedings of the 33rd Autumn Symposium of the Ceramic Society of Japan, 2F27 (2020) [Non-patent document 4] Proceedings of the 34th Autumn Symposium of the Ceramic Society of Japan, 2T26 (2021) Summary of the Invention [Problem to be solved by the invention]

[0006] Methods that involve resins have durability issues, while methods using hot pressing, spark plasma sintering, and hot isostatic pressing have productivity issues from the perspective of practical application. Phosphors with transparency and blue fluorescence have been proposed, but the market demands blue fluorescent materials with higher quality and superior productivity than conventional materials in order to improve the color rendering properties of white light. Note that while the issues with white light have been discussed, similar issues can arise with blue fluorescent materials and their applications in general.

[0007] The present disclosure has been made in view of the above circumstances, and aims to provide a blue-emitting transparent sialon ceramic that has durability equal to or greater than that of conventional ceramics, is capable of increasing productivity, and possesses both transparency and blue fluorescence, and a method for manufacturing the same. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that the present problem can be solved in the following manner. [1]: General formula M x (Si, Al) 12 (N,O) 16 (wherein M is at least one element selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and 0.3≦x≦1), wherein the main phase is an α-sialon in which part of M is substituted with Ce, The luminescent center ion is at least Ce 3+ A blue-emitting transparent SiAlON ceramic. [2]: The blue light-emitting transparent sialon ceramic according to [1], characterized in that the Ce element content is 0.05 to 10 mass %. [3]: The blue light-emitting transparent sialon ceramic according to [1] or [2], characterized in that the emission peak wavelength when excited at 365 nm is 490 nm or less. [4]: A method for producing a blue light-emitting transparent sialon ceramic according to any one of [1] to [3], a step of uniaxially pressing a mixture containing at least one or more selected from dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide, silicon nitride, aluminum nitride, and at least one of cerium oxide and a cerium-containing compound that becomes cerium oxide when treated at high temperature, to produce a primary compact; a step of cold isostatically pressing the primary compact to produce a secondary compact; sintering the secondary compact in a nitrogen atmosphere to produce a sintered body; A method for producing a blue light-emitting transparent sialon ceramic, comprising: [5]: The method for producing blue-emitting transparent sialon ceramics according to [4], characterized in that the average particle size of the cerium oxide and the cerium-containing compound is 100 nm or less. [Effects of the Invention]

[0009] The present disclosure has the excellent effect of providing a blue-light-emitting transparent SiAlON ceramic that has durability equal to or greater than that of conventional ceramics, while enabling increased productivity and that combines transparency and blue fluorescence, and a method for manufacturing the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a graph showing the in-line transmittance spectra of the ceramics of Example 1 and Comparative Example 1. [Figure 2] 1 is a graph showing the in-line transmittance spectra of the ceramics of Examples 2 to 4. [Figure 3] 1 is a graph showing the in-line transmittance spectra of the ceramics of Examples 5 to 7. [Figure 4] Graph showing the emission spectra of the ceramics of Example 1 and Comparative Example 1. [Figure 5] Graph showing the emission spectra of the ceramics of Examples 2 to 4. [Figure 6] Graph showing the emission spectra of the ceramics of Examples 5 to 7. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of this embodiment will be described below. However, this disclosure is not limited to this embodiment, and other embodiments may also fall within the scope of this disclosure as long as they conform to the gist of the present disclosure. Furthermore, the numerical values ​​"A to B" specified in this specification refer to a range that satisfies the range between numerical value A and a value greater than numerical value A, and between numerical value B and a value smaller than numerical value B. Unless otherwise noted, the various components appearing in this specification may each be used independently, either alone or in combination of two or more.

[0012] 1. Blue-emitting transparent SiAlON ceramics The blue-emitting transparent SiAlON ceramic of the present disclosure (hereinafter also referred to as the present ceramic) is a blue-emitting transparent SiAlON ceramic represented by the general formula M x (Si, Al) 12 (N,O) 16 (wherein M is at least one selected from the group consisting of dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and 0.3≦x≦1), the main phase is an α-sialon in which part of M is substituted with Ce (cerium). The luminescent center ion is at least Ce. 3+ In α-sialon, the metal element M acts as a stabilizing ion, and usually Dy is 3+ , Ho is Ho 3+ , Er is Er 3+ , Tm is Tm 3+ , Yb is Yb 2+ or Yb 3+ , Lu is Lu 3+ Here, the main phase means that it accounts for 50 mass % or more per 100 mass % of the crystalline phase of the present ceramic. The main phase preferably accounts for 70 mass % or more.

[0013] General formula M x (Si, Al) 12 (N,O) 16 is the general formula M x Si 12-(b+c) Al (b+c) O c N 16-c (wherein M is at least one selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and 0.3≦x≦1, 0.9≦b≦3, and 0≦c≦2). x Si 12-(b+c) Al (b+c) O c N 16-c In the general formula M, x is preferably 0.3 or more and 0.8 or less. x Si 12-(b+c) Al (b+c) O c N16-c In the above formula, it is preferable that b / c is 1.5 or more.

[0014] The present ceramics are not particulate (powdered) but polycrystalline bodies formed by the aggregation of many single crystals of a sialon phosphor, and are sintered bodies of any shape. The shape of the sintered body is not particularly limited, and examples thereof include disks, plates, convex lenses, concave lenses, spheres, hemispheres, cubes, rectangular parallelepipeds, pillars such as prisms and cylinders, and tubular shapes such as square tubes and cylinders. When the present ceramics are applied to white LEDs, they are used by being molded into a shape that can be fixed to the outer periphery of a blue LED, which serves as the light source.

[0015] The term "transparent" in this ceramic refers to a linear transmittance at a wavelength of 600 nm of 20% or more per 100 nm film thickness. When the ceramic is irradiated with near-ultraviolet light as an excitation source, it emits blue visible light that exhibits a high color rendering emission spectrum with an emission peak in the wavelength range of 430 nm to 490 nm. Near-ultraviolet light refers to the near-ultraviolet region with a wavelength of 200 nm or more, and for example, near-ultraviolet light in the band of 350 nm to 420 nm can be suitably used. Here, "blue" refers to the wavelength range of 430 nm to 490 nm, and also includes blue leaning toward green, i.e., blue-green. The peak wavelength is required to be within this wavelength range, and emission wavelengths outside the wavelength range may also be included.

[0016] The ceramic preferably has an emission peak wavelength of 480 nm or less. When the ceramic has a thickness of 100 μm, the in-line transmittance of visible light at 600 nm is preferably 25% or more, more preferably 30% or more, and particularly preferably 35% or more.

[0017] The present ceramic uses at least one element selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, and lutetium as the metal element M, and by substituting a portion of M with Ce, it is possible to provide a blue-emitting transparent SiAlON ceramic that achieves optimal transparency for blue fluorescence, a shorter emission wavelength, and excellent durability, as well as a method for producing the same.

[0018] Generally, as the atomic weight of the metal element M in an α-sialon phosphor increases, i.e., as the ionic radius of the metal ion decreases, the viscosity of the liquid phase increases, making mass transfer in the liquid phase more difficult. This makes it difficult to obtain a dense bulk body, resulting in reduced durability and quality. However, after extensive research, the present inventors surprisingly overturned this conventional wisdom and discovered that the present ceramics use at least one element selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, which has a smaller ionic radius than yttrium, which is commonly used in sialon phosphors, as the metal element M, and that by substituting a portion of M with Ce, it is possible to obtain sialon ceramics that are highly dense and can achieve shorter blue emission wavelengths. The reason for this is only speculation, but it is thought that the combination of Ce, which has a small atomic weight, i.e., a large ionic radius, with a metal element M selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, which has a large atomic weight, i.e., a small ionic radius, results in appropriate values ​​for the nucleation and melt viscosity of α-sialon; in other words, the constituent elements are blended in an optimal balance, thereby achieving densification of the sintered body.

[0019] This ceramic has Ce as the luminescent center ion. 3+The ceramic is a mass made of a sialon phosphor containing SiO2, and the ceramic itself can be molded into a predetermined shape and applied as a blue phosphor, for example, in white LEDs. This eliminates the need to disperse the sialon phosphor in a resin, as in the past, and prevents a reduction in the luminous efficiency of white LEDs due to light scattering caused by the difference in refractive index between the sialon phosphor and the resin. Furthermore, because the sialon phosphor is uniformly distributed throughout the ceramic, this ceramic has the advantage of providing uniform, unbiased fluorescent light emission and uniform, unbiased visible light transmittance.

[0020] From the viewpoint of densification and luminescence intensity, the content of Ce element contained as the luminescence center element is preferably 0.05 to 10 mass % relative to 100 mass % of the present ceramic, more preferably 0.1 to 8 mass %, and even more preferably 0.3 to 4 mass %. The present ceramic contains Ce as the luminescence center ion. 3+ In addition to the mode in which only holmium ions (Ho 3+ ), dysprosium ion (Dy 3+ ) and luminescence due to at least one M selected from Ce 3+ It is also possible to use light emission by the method.

[0021] From the viewpoint of further improving durability and quality, the present ceramics preferably have an emission peak wavelength of 490 nm or less when excited at 365 nm. More preferably, the emission peak wavelength is 480 nm or less, and even more preferably, the emission peak wavelength is 476 nm or less. Light at 365 nm is advantageous in that it is highly versatile in laser light sources and the like.

[0022] Since the ceramic emits blue to blue-green visible light, it can be used in white light emitting devices by combining it with other known phosphors. It can also be used in light emitting elements, light emitting devices, etc.

[0023] 2. Manufacturing method for blue-emitting transparent SiAlON ceramics An example of a method for producing the present ceramics will be described below, but the present ceramics are not limited to the following method.

[0024] The method for producing the ceramics includes the steps of uniaxially pressing a mixture containing at least one selected from dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide, silicon nitride powder, aluminum nitride, and at least one of cerium oxide and a cerium-containing compound that becomes cerium oxide upon high-temperature treatment to produce a primary compact, and cold isostatically pressing the primary compact to produce a secondary compact. The secondary compact can then be gas-pressured and fired under a nitrogen atmosphere to produce a sintered body. Examples of cerium-containing compounds that become cerium oxide upon high-temperature treatment include cerium nitrate, cerium carbonate, cerium hydroxide, and cerium oxalate. Specific examples are described in detail below.

[0025] The raw material powder is a mixture containing at least one selected from the group consisting of dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide, silicon nitride, aluminum nitride, and cerium (IV) oxide (CeO2), weighed out to a predetermined mass ratio. Cerium oxide is preferably used as the source of the luminescent center element. The mixing ratio of these raw material powders is adjusted appropriately depending on the fluorescence and light transmittance of the desired blue-emitting transparent SiAlON ceramic.

[0026] From the viewpoint of shortening the wavelength of the blue light emitted by the present ceramic, the average particle size of cerium oxide is preferably 100 nm or less, more preferably 70 nm or less. The lower limit of the average particle size is not particularly limited, but considering availability, it is usually 10 nm or more. The average particle size of cerium oxide was determined by measuring the maximum lengths of 50 particles in the field of view of an electron microscope photograph and taking the average of the measured lengths.

[0027] From the viewpoint of shifting the wavelength of the blue light emitted by the present ceramic to a shorter wavelength, it is preferable that the average particle size of any one or more selected from dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide is small. A preferred range is 20 μm or less, more preferably 10 μm or less, and even more preferably less than 2 μm. There is no restriction on the lower limit, but considering ease of availability, it is usually 10 nm or more. Note that the average particle size here is the same as that of cerium oxide.

[0028] A dispersant is added to these raw material powders, and the mixture is wet-mixed in, for example, ethanol using a ball mill to prepare a slurry containing the raw material powders. The resulting slurry is heated using a heater such as a mantle heater to thoroughly evaporate the ethanol contained in the slurry, thereby obtaining a mixture of the raw material powders (mixed powder). Note that a known mixer may be used instead of or in addition to stirring using a ball mill.

[0029] The mixed powder is forced to pass through two or more sieves with different mesh sizes in stages to granulate the mixed powder to a predetermined particle size. Separately, a binder such as fully melted paraffin, a lubricant such as bis(2-ethylhexyl) phthalate, and a solvent such as cyclohexane are thoroughly stirred and mixed to prepare a binder solution. Granulation may also be performed by spray drying or freeze drying instead of or in combination with sieving.

[0030] The granulated mixed powder is added to the obtained binder solution and mixed so that the binder solution permeates the entire mixed powder. The mixture is then heated to evaporate the solvent. After the solvent has sufficiently evaporated, the mixed powder is forced to pass through a sieve with openings of a predetermined size to obtain a granulated powder having a predetermined particle size.

[0031] A predetermined amount of the obtained granulated powder is taken so that the thickness of the molded body after molding is a predetermined size, and the granulated powder is fed into a mold. Then, using a uniaxial pressing machine, uniaxial pressing is performed at a pressure of 50 MPa for 30 seconds, for example, to obtain a primary molded body.

[0032] The obtained primary compact is chamfered and vacuum-packed, and then the vacuum-packed primary compact is subjected to cold isostatic pressing (CIP) using a cold isostatic pressing device at a pressure of 200 MPa, for example, once for 1 minute or repeatedly 10 times to obtain a secondary compact.

[0033] Next, the secondary compact is placed on an alumina boat, for example, and heated in a tubular resistance furnace in an air stream of, for example, 70 L / min to degrease the secondary compact and remove the binder contained in the secondary compact. In this degreasing process, the heating temperature and heating time of the secondary compact are set in two stages. In the first heating stage, for example, the heating temperature is 250°C and the heating time is 3 hours. In the second heating stage, for example, the heating temperature is 500°C and the heating time is 3 hours. In order to promote the thermal decomposition and oxidation of the binder and lubricant contained in the secondary compact, it is preferable to heat the secondary compact to a temperature of 300 to 600°C and a heating time of 1 to 10 hours.

[0034] Next, the degreased secondary compact is fired in a nitrogen atmosphere using a multipurpose high-temperature sintering furnace to obtain a sintered body. To sinter the secondary compact, a porous Si3N4 crucible made by reaction sintering is placed inside a carbon housing, and a porous Si3N4 shelf is placed inside the crucible, and the secondary compact is placed on the shelf. For example, the sintering process can be performed under the following conditions: from room temperature to 1200°C under vacuum (6.7 x 10 -2The temperature is increased at 20°C / min (less than 100 Pa), and at 1200°C, the pressure is increased to 0.25 MPa with nitrogen gas. From 1200°C to the target sintering temperature, the temperature is increased at 10°C / min, and the pressure is increased to 0.9 MPa with a nitrogen gas flow of 4 L / min. The sintering temperature of the secondary compact is 1600°C, and the sintering time is 2 hours. The pressure during sintering is 0.88 MPa to 0.91 MPa in a nitrogen atmosphere. After sintering is complete, the sintered body is allowed to cool naturally to room temperature.

[0035] According to this ceramic manufacturing method, the primary compact is cold isostatically pressed to produce a secondary compact, and the secondary compact is fired in a nitrogen atmosphere to produce a sintered body. This process removes regions with different refractive indices that scatter light and glass phases that absorb light. As a result, the resulting blue-emitting transparent SiAlON ceramic has SiAlON phosphors uniformly distributed throughout. This results in uniform, even fluorescent light emission and uniform visible light transmittance. Furthermore, because the blue-emitting transparent SiAlON ceramic has few internal pores or glass phases, there is no loss of transparency due to pores or glass phases, resulting in excellent light transmittance.

[0036] This ceramic manufacturing method has been found to produce high-quality ceramics without the need for the hot isostatic pressing firing process, which requires special equipment and statutory inspections such as open inspections, and is a factor in high production costs. In other words, it has been found that ceramics can be produced that have durability equal to or greater than conventional ceramics, are highly productive, and possess both transparency and blue fluorescence. Note that this ceramic does not exclude the possibility of a further firing process using hot isostatic pressing. By performing a firing process using hot isostatic pressing, the linear transmittance of the resulting ceramics can be increased. Hot isostatic pressing can be added depending on the needs and applications of the desired ceramics.

[0037] This ceramic can be applied to light-emitting devices such as light-emitting diodes (LEDs), fluorescent lights, scintillators, and lasers, as well as display devices such as televisions and computer displays, and sensors. Conventionally, phosphors have been supplied in powder form, making it difficult to apply phosphors to fields that use single crystals, such as scintillators. This ceramic is a sintered body that can take any shape, so it can be widely applied to fields that use single crystals. This ceramic has extremely little quenching with temperature rise, making it possible to realize light-emitting devices with excellent color rendering properties, etc.

[0038] <<Example>> The present disclosure will be described in more detail below, but the present disclosure is not limited to the following examples.

[0039] (Manufacturing blue light-emitting transparent sialon ceramics) Example 1: (Lu 0.5 ,Ce 0.5 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 ) The raw materials used were silicon nitride (α-Si3N4) powder (average particle size 0.2 μm, SN-E10, manufactured by Ube Industries, Ltd.), aluminum nitride (AlN) powder (average particle size 0.6 μm, H grade, manufactured by Tokuyama Corporation), Lu2O3 (average particle size 2-10 μm, STD, manufactured by Shin-Etsu Chemical Co., Ltd.), and CeO2 (average particle size 2-10 μm, STD, manufactured by Shin-Etsu Chemical Co., Ltd.). These powders were weighed out so that the molar ratio of Si3N4:AlN:Lu2O3:CeO2 was 21:9:0.5:1. These were mixed with 2% by mass of a dispersant (polyacrylic acid-based, Cerna E503, manufactured by Chukyo Yushi Co., Ltd.) and mixed in ethanol using a ball mill (pot: silicon nitride, internal volume: 400 mL, sialon balls: particle size 5 mm, 1,400 balls) at a rotation speed of 110 rpm for 48 hours to prepare a slurry containing the raw material powder.

[0040] The obtained slurry was heated using a heater such as a mantle heater to thoroughly evaporate the ethanol contained in the slurry, thereby obtaining a mixture of raw material powders (mixed powder).

[0041] Next, the mixed powder was forced to pass through a sieve #32 (nominal size: 500 μm) and a sieve #48 (nominal size: 300 μm) in this order to granulate the mixed powder having a predetermined particle size.

[0042] Separately, a binder solution was prepared by thoroughly stirring and mixing a fully melted binder paraffin (melting point 46°C to 48°C, manufactured by Junsei Chemical Co., Ltd.), a lubricant bis(2-ethylhexyl) phthalate (purity 97.0%, manufactured by Wako Pure Chemical Industries, Ltd.), and a solvent cyclohexane (purity 99.5%, manufactured by Wako Pure Chemical Industries, Ltd.). The amount of paraffin added was 4 mass% and the amount of bis(2-ethylhexyl) phthalate added was 2 mass% relative to the total amount of raw material powder. The amount of cyclohexane added was 35 mL / 100 g.

[0043] The granulated mixed powder was added to the obtained binder solution, and the mixture was heated while mixing so that the binder solution permeated the entire mixed powder, and the solvent was evaporated. After the solvent was sufficiently evaporated, the mixed powder was forced to pass through a sieve of #60 (nominal size: 250 μm) to obtain a granulated powder having a predetermined particle size.

[0044] Next, 0.7 g of the granulated powder was collected using a cylindrical stainless steel mold with a diameter of 15 mm, and the granulated powder was supplied into the mold so that the thickness of the molded body would be 2 mm. Then, using a uniaxial pressing machine (product name: MP-500H, manufactured by Maruto Co., Ltd.), uniaxial pressing was performed at a pressure of 50 MPa for 30 seconds to obtain a primary compact. The obtained primary compact was chamfered and vacuum-packed. Next, using a cold isostatic pressing device (product name: CPA50-200, manufactured by NPA Systems Co., Ltd.), the vacuum-packed primary compact was cold-isostatically pressed 10 times at a pressure of 200 MPa for 60 seconds to produce a secondary compact.

[0045] This secondary compact was placed on an alumina boat and heated in a tubular resistance furnace in an air flow of 70 L / min to degrease the secondary compact and remove the binder, lubricant, and other organic substances contained in the secondary compact. In this degreasing process, the secondary compact was heated in air at 250°C for 3 hours, then degreased at 500°C for 3 hours (heating rate 1°C / min), and gas-pressure sintered at 1600°C for 4 hours in 0.9 MPa N2.

[0046] Comparative Example 1: (Y 0.5 ,Ce 0.5 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 )) The ceramics of Comparative Example 1 were obtained in the same manner as in Example 1, except that Y2O3 (average particle size 1 μm, RU-P, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of Lu2O3, and the powder mixture was weighed so that the molar ratio of Si3N4:AlN:Y2O3:CeO2 = 21:9:0.5:1.

[0047] Example 2: (Lu 0.9 ,Ce 0.1 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 )) The ceramics of Example 2 were obtained in the same manner as in Example 1, except that CeO2 nanoparticles (<50 nm (BET), Sigma-Aldrich) were used instead of CeO2, and the powder mixture was weighed out so that the molar ratio of Si3N4:AlN:Lu2O3:CeO2 = 21:9:0.9:0.2.

[0048] Example 3: (Lu 0.95 ,Ce 0.05 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 )) The ceramics according to Example 3 were obtained in the same manner as in Example 1, except that the powder mixture was weighed out so that the molar ratio of Si3N4:AlN:Lu2O3:CeO2 was 21:9:0.95:0.1.

[0049] Example 4: (Lu 0.95 ,Ce 0.05 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 )) The ceramics of Example 4 were obtained in the same manner as in Example 2, except that the powder mixture was weighed out so that the molar ratio of Si3N4:AlN:Lu2O3:CeO2 was 21:9:0.95:0.1.

[0050] Example 5: (Ho 0.5 ,Ce 0.5 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 ) The ceramics of Example 5 were obtained in the same manner as in Example 1, except that Ho2O3 (average particle size 2-10 μm, STD, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of Lu2O3, and the powder mixture was weighed out so that the molar ratio of Si3N4:AlN:Ho2O3:CeO2 = 21:9:0.5:1.

[0051] Example 6: (Dy 0.5 ,Ce 0.5 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 ) The ceramics of Example 6 were obtained in the same manner as in Example 1, except that DyO (average particle size 2-10 μm, STD, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of LuO and the powder mixture was weighed so that the molar ratio of SiN:AlN:DyO:CeO = 21:9:0.5:1.

[0052] Example 7: (Lu 0.9 ,Ce0.1 ) 1 / 3 Si 10.5 Al 1.5 O 0.5 N 15.5 ) The ceramics of Example 7 were obtained in the same manner as in Example 1, except that Lu2O3 (average particle size 1 μm, RU, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of Lu2O3, and the powder mixture was weighed so that the molar ratio of Si3N4:AlN:Lu2O3:CeO2 = 21:9:0.9:0.2.

[0053] (Measurement of in-line transmittance) The samples (cylindrical sialon ceramics) of each example and comparative example were machined to thin slices, ultimately to a thickness of 100 μm. Simultaneously with the thinning, both sides were mirror-polished. The linear transmittance of visible light was measured for these double-sided mirror-polished samples. The linear transmittance was measured by clamping a 100 μm-thick sample between an 8 mm diameter aperture and using an ultraviolet-visible-near-infrared spectrophotometer (UV-3600Plus, manufactured by Shimadzu Corporation) over a wavelength range of 190 nm to 3200 nm. The results are shown in Figures 1 to 3. Table 1 also shows the transmittance per 100 nm of film thickness at 600 nm.

[0054] 1 to 3, it was confirmed that Examples 1 to 7 exhibited higher linear transmittance than Comparative Example 1 across the entire visible to near-infrared bands. Sources of light scattering include pores, second phases, and coarse particles. The porosity was approximately 3% in each of the Examples and Comparative Examples (see Table 1), and it was confirmed that the second phase consisted solely of α-Si3N4 and β-sialon, which have a refractive index that is only slightly different from that of β-sialon. From these results, it is believed that these factors are not the reason why Examples 1 to 7 had higher transmittance than Comparative Example 1.

[0055] The average particle size of the α-sialon in Example 1 was 328 nm, and the average particle size of the α-sialon in Comparative Example 1 was 413 nm. It was confirmed that the average particle size of Example 1 was smaller than that of Comparative Example 1. This is due to the fact that Lu, which has a small ionic radius, 3+This is thought to be due to the high viscosity of the liquid phase caused by the addition of Lu2O3 as a raw material, and the large number of nuclei generated due to the wide α-sialon formation region, which suppressed grain growth. The average grain size of α-sialon is the value determined in accordance with the intercept method of ISO 13383-1:2012.

[0056] The reason why Example 1 had a higher linear transmittance than Comparative Example 1 is that Lu 3+ This is thought to be due to the fact that the use of Lu2O3 as a raw material generates a highly viscous liquid phase at high temperatures, which inhibits grain growth and reduces light scattering by α-sialon particles. The reason for the particularly high linear transmittance of Example 7 is thought to be that the average particle size of the Lu2O3 used as a raw material was small, which resulted in a more uniform formation of the liquid phase and a narrower particle size distribution.

[0057] (Measurement of emission spectrum) Emission spectra were measured for samples prepared in the same manner as for transmittance measurements. Specifically, fluorescence spectra were measured using a fluorescence spectrophotometer (FP6300, manufactured by JASCO Corporation) on samples that had been mirror-polished on both sides to a thickness of 0.1 mm. The excitation wavelength was set to 365 nm, and a sharp-cut filter (L-37, manufactured by Hoya) was set on the fluorescence side. The results are shown in Figures 4 to 6. The emission peak wavelengths are shown in Table 1.

[0058] All samples contained Ce 3+ The peak wavelength of the fluorescence spectrum of Example 1 was 487 nm, while that of Comparative Example 1 was 494 nm, confirming that Example 1 could emit light at a shorter wavelength. In addition, the lattice volume of Comparative Example 1 was 299.15 Å. 3 whereas the lattice volume of Example 1 is 298.92 Å 3 It was confirmed that the lattice volume of Example 1 was smaller. Such a decrease in lattice volume is due to the 3+ This is due to the small ionic radius of Lu. 3+By including Ce, the crystal lattice of α-sialon becomes more contracted, and 3+ This is thought to be due to a change in the crystal field acting on the luminescence wavelength. As a result, it is thought that a shift to shorter wavelengths occurred in Example 1 compared to Comparative Example 1. The lattice volume was calculated from the lattice constant determined by X-ray diffraction.

[0059] It has been confirmed that this ceramic can achieve a shorter emission peak wavelength than conventional ceramics when manufactured using the same manufacturing process and with the same excitation wavelength. Note that even when the same raw materials are used, the emission peak wavelength of the resulting ceramic varies depending on the manufacturing process. Furthermore, the emission peak wavelength of the same ceramic can vary when the excitation wavelength is changed.

[0060] [Table 1]

[0061] From the results in Table 1 and Figures 4 to 6, it was confirmed that the present ceramics of Examples 1 to 7 emitted fluorescent light in a range of blue to blue-green. Furthermore, from Table 1, it was confirmed that the emission wavelength became shorter as the average particle size of the cerium (IV) oxide (CeO2) used as a raw material or the average particle size of the rare earth oxide (M2O3) used as a raw material became smaller. This is because the composition of the α-sialon was homogenized.

Claims

1. General formula M ｘ (Si, Al) １２ (N, O) １６ (wherein M is at least one element selected from the group consisting of dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and 0.3≦x≦1), wherein a main phase is an α-sialon in which a portion of M is substituted with Ce, The content of the Ce element is 0.05 to 10 mass %, and a molar ratio of M to Ce (M:Ce) of 95:5 to 50:50; The luminescent center ion is at least Ce ３＋ A blue-emitting transparent SiAlON ceramic.

2. 2. The blue light-emitting transparent sialon ceramic according to claim 1, wherein the blue light-emitting transparent sialon ceramic has an emission peak wavelength of 490 nm or less when excited at 365 nm.

3. A method for producing the blue light-emitting transparent Sialon ceramic according to claim 1 or 2, comprising the steps of: a step of uniaxially pressing a mixture containing at least one selected from the group consisting of dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide, silicon nitride, aluminum nitride, and at least one of cerium oxide and a cerium-containing compound that becomes cerium oxide when treated at high temperature, to produce a primary compact; a step of cold isostatically pressing the primary compact to produce a secondary compact; A step of firing the secondary compact in a nitrogen atmosphere to produce a sintered body; A method for producing a blue light-emitting transparent sialon ceramic, comprising:

4. 4. The method for producing blue-emitting transparent sialon ceramics according to claim 3, wherein the average particle size of the cerium oxide and the cerium-containing compound is 100 nm or less.

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