METHOD FOR PRODUCING Ce-ACTIVATED α-SIALON PHOSPHOR

Abstract

To provide a method for producing a Ce-activated α-sialon phosphor having superior internal quantum efficiency.SOLUTION: One aspect of the present disclosure provides a method for producing a Ce-activated α-sialon phosphor. The method includes a step of subjecting a mixture containing a Ce-activated α-sialon and a Eu source to heat treatment at 1200 to 1500°C to produce a heat-treated product.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a Ce-activated α-sialon phosphor.

Background Art

[0002] α-sialon (Si-Al-O-N) is a solid solution having a structure in which specific elements penetrate and solid-solve between the crystal lattices of α-type silicon nitride, and a part of the Si-N bond is replaced by an Al-N bond or an Al-O bond in order to maintain electrical neutrality. Fluorescence is exhibited by replacing a part of the elements that have penetrated and solid-solved with a luminescent center element.

[0003] Patent Document 1 discloses a method for manufacturing a phosphor mainly composed of α-type sialon represented by the general formula: (Ca X , M Y )(Si, Al) 12 (O, N) 16 (where M is one or more elements selected from Ce, Pr, Eu, Tb, Yb, and Er, 0.3 < X + Y < 1.5, 0 < Y < 0.7), which comprises heating a mixed powder composed of (a) silicon nitride, (b) aluminum nitride, (c) calcium fluoride, (d) an oxide or nitride of M, and further, if necessary, (e) aluminum oxide, and pulverizing the obtained product to a desired particle size.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Phosphors containing α-sialon with Ce as the luminescent center element have attracted attention as phosphors that exhibit fluorescence in the blue to green regions. The present disclosure aims to provide a method for manufacturing a Ce-activated α-sialon phosphor having excellent internal quantum efficiency.

Means for Solving the Problems

[0006] The inventors have found that by subjecting α-sialon activated with Ce to heat treatment together with a Eu source, a Ce-activated α-sialon phosphor having excellent internal quantum efficiency can be produced.

[0007] The present disclosure provides the following [1] to [5]. [1] A method for manufacturing a Ce-activated α-sialon phosphor, comprising a step of heat-treating a mixture containing Ce-activated α-sialon and a Eu source at 1200 to 1500 °C to obtain a heat-treated product. [2] The manufacturing method according to [1], wherein the content of the Eu source in the mixture is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the content of Ce-activated α-sialon. [3] The manufacturing method according to [1] or [2], wherein the heat treatment is performed in an atmosphere containing at least one selected from the group consisting of a rare gas and a reducing gas. [4] The manufacturing method according to any one of [1] to [3], further comprising a step of acid-treating the heat-treated product. [5] The manufacturing method according to any one of [1] to [4], further comprising a step of obtaining Ce-activated α-sialon by firing a raw material composition containing an Si source, an Al source, and a Ce source.

Effects of the Invention

[0008] According to the present disclosure, a method for manufacturing a Ce-activated α-sialon phosphor having excellent internal quantum efficiency can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content.

[0011] Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition. The "steps" in this specification may be steps independent of each other or steps performed simultaneously.

[0012] One embodiment of the present disclosure is a method for producing a Ce-activated α-sialon phosphor, which includes a step of heat-treating a mixture containing Ce-activated α-sialon and a Eu source at 1200 to 1500 °C to obtain a heat-treated product.

[0013] <Ce-activated α-sialon (raw material sialon)> The α-sialon activated with Ce (hereinafter also referred to as "raw material sialon") contains Ce as a luminescence center element and can emit fluorescence by itself. The raw material sialon may not substantially contain Eu as a luminescence center element, and may substantially contain only Ce as a luminescence center element. That the raw material sialon does not substantially contain Eu as a luminescence center element means that no emission peak derived from Eu is observed in the emission spectrum of the raw material sialon when excited with light of a wavelength of 405 nm. Also, that the raw material sialon substantially contains only Ce as a luminescence center element means that only the peak derived from Ce is observed as a peak in the emission spectrum of the raw material sialon when excited with light of a wavelength of 405 nm. For example, even if the raw material sialon contains Eu, if no independent emission peak derived from Eu as described above is observed, it is determined in this specification that Eu is not an element contained as a luminescence center element.

[0014] The raw material sialon may contain M, Ce, Si, Al, O, and N as constituent elements. Here, M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). The content of M may be 1 mol% or more, or 2 mol% or more, based on the total content of M, Ce, Si, Al, O, and N in the raw material sialon (hereinafter also referred to as "the total content of the above constituent elements"). Also, the content of M may be 4 mol% or less, or 3 mol% or less, based on the total content of the above constituent elements in the raw material sialon. The content of Ce may be 0.05 mol% or more, or 0.1 mol% or more, based on the total content of the above constituent elements in the raw material sialon. Also, the content of Ce may be 2 mol% or less, or 1 mol% or less, based on the total content of the above constituent elements in the raw material sialon.

[0015] The Si content may be 25 mol% or more, or 30 mol% or more, based on the total content of the above-described constituent elements in the raw material sialon. Further, the Si content may be 45 mol% or less, or 40 mol% or less, based on the total content of the above-described constituent elements in the raw material sialon. The Al content may be 4 mol% or more, 5 mol% or more, or 6 mol% or more, based on the total content of the above-described constituent elements in the raw material sialon. Further, the Al content may be 12 mol% or less, 10 mol% or less, 9 mol% or less, or 8 mol% or less, based on the total content of the above-described constituent elements in the raw material sialon. The contents of M, Ce, Si, and Al are determined by analysis using an ICP emission spectroscopic analysis method with a multi-type ICP emission spectrometer.

[0016] The O content may be 0.5 mol% or more, or 1 mol% or more, based on the total content of the above-described constituent elements in the raw material sialon. Further, the O content may be 5 mol% or less, or 4 mol% or less, based on the total content of the above-described constituent elements in the raw material sialon. The N content may be 40 mol% or more, or 45 mol% or more, based on the total content of the above-described constituent elements in the raw material sialon. Further, the N content may be 60 mol% or less, or 55 mol% or less, based on the total content of the above-described constituent elements in the raw material sialon. The contents of O and N are determined by analysis of the amounts of oxygen and nitrogen using an oxygen-nitrogen analyzer.

[0017] For example, in the raw material sialon, based on the total content of M, Ce, Si, Al, O, and N in the raw material sialon, the content of the above-described M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 4 to 12 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol%, and the content of the above-described M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 5 to 9 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol%.

[0018] The starting sialon may contain, as the main crystal, a crystal having the same crystal structure as α-sialon, or may consist of a crystal having the same crystal structure as α-sialon. In the powder X-ray diffraction pattern of the starting sialon, the ratio of the maximum diffraction line intensity of a foreign phase to the diffraction line intensity of the (101) plane may be 10% or less, 5% or less, 3% or less, or 2% or less. In this specification, the powder X-ray diffraction pattern means one obtained by the powder X-ray diffraction method using CuKα rays under the condition of 25°C. Also, the maximum diffraction line of the foreign phase means the one with the maximum diffraction intensity among the diffraction lines that cannot be attributed to α-sialon in the powder X-ray diffraction pattern.

[0019] The starting sialon may contain, for example, α-sialon represented by the following general formula (1). (M a+ x ,Ce 3+ y )Si 12-(m+n) Al (m+n) O n N 16-n (1) [In general formula (1), M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). If the valence of M is a, then m = ax + 3y. Ce 3+ substitutes the M site, 0.3 ≤ x + y ≤ 2, 0.03 ≤ y ≤ 0.5, and 0 ≤ n ≤ m.]

[0020] The starting sialon may contain Ca, or may contain α-sialon in which Ca is solid-solved. In the above general formula (1), M may be Ca, or may be two or more elements including Ca and at least one element selected from the group consisting of Li, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). When M is Ca, in general formula (1), a = 2. Whether the starting sialon contains Ca can be confirmed by performing quantitative analysis of elements using an ICP emission spectrometer.

[0021] In general formula (1), x + y may be 0.4 or more, 0.5 or more, 0.6 or more, or 0.7 or more, and may also be 1.8 or less, 1.5 or less, 1.3 or less, 1.1 or less, 1.0 or less, or 0.9 or less. In general formula (1), y may be 0.05 or more, or 0.06 or more, and may also be 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. In general formula (1), n may be 0.01 or more, 0.05 or more, or 0.10 or more, and may also be less than m.

[0022] The raw material sialon containing α-sialon represented by the general formula (1) means that in the powder X-ray diffraction pattern of the raw material sialon, the ratio of the maximum diffraction line intensity of the heterogeneous phase to the diffraction line intensity of the (101) plane is 10% or less, and the content ratios of the respective constituent elements (M, Ce, Si, Al, O, and N) calculated by the ICP emission spectroscopic analysis method using a multi-type ICP emission spectrometer and the analysis of the amounts of oxygen and nitrogen by an oxygen and nitrogen analyzer are equal to the ratios shown in the general formula (1).

[0023] The raw material sialon may be represented by, for example, the general formula (1) above. In this case, M, x + y, y, and n may be as described above, respectively. The constituent elements and ratios of the raw material sialon can be determined by the analysis of the amounts of oxygen and nitrogen by an oxygen and nitrogen analyzer and the ICP emission spectroscopic analysis method using a multi-type ICP emission spectrometer. The fact that the raw material sialon is represented by the general formula (1) means that when the constituent elements and ratios of the raw material sialon are determined by the above analysis, the content ratios of Ce, Si, Al, O, N, and M in the general formula (1) are within the ranges shown in the general formula (1), and the content rate of elements other than the above elements is 1.5% by mass or less.

[0024] The manufacturing method according to one embodiment may have a step of obtaining a raw material sialon (hereinafter, also simply referred to as "step of obtaining α-sialon"). In the step of obtaining α-sialon, for example, a raw material composition containing an Si source, an Al source, and a Ce source is fired to obtain a raw material sialon.

[0025] The Si source means a compound or a simple substance containing silicon as a constituent element; the Al source means a compound or a simple substance containing aluminum as a constituent element; and the Ce source means a compound or a simple substance containing cerium as a constituent element. In this specification, a compound containing silicon as a constituent element is also referred to as a silicon compound, a compound containing aluminum as a constituent element is also referred to as an aluminum compound, and a compound containing cerium as a constituent element is also referred to as a cerium compound. The silicon compound, the aluminum compound, and the cerium compound may each be any of a nitride, an oxide, a oxynitride, and a hydroxide. At least one of the Si source, the Al source, and the Ce source may be a nitride. Since the nitride contains nitrogen which is a constituent element of the raw material sialon, it can also be called a nitrogen source.

[0026] Examples of the silicon compound include silicon nitride (Si3N4), silicon dioxide (SiO2), and the like.

[0027] Examples of the aluminum compound include aluminum nitride (AlN), aluminum oxide (Al2O3), aluminum hydroxide (Al(OH)3), and the like.

[0028] Examples of the cerium compound include cerium oxide (CeO2), cerium nitride (CeN), cerium hydroxide (Ce(OH)4), and cerium fluoride (CeF3).

[0029] The raw material composition may include other raw materials containing elements that can form α-sialon, other than the Si source, Al source, and Ce source. Examples of other raw materials include a Li source, a Ca source, etc. The Li source means a compound or a simple substance containing lithium as a constituent element, and the Ca source means a compound or a simple substance containing calcium as a constituent element. In this specification, a compound containing lithium as a constituent element is also referred to as a lithium compound, and a compound containing calcium as a constituent element is also referred to as a calcium compound. Each of the lithium compound and the calcium compound may be any of a halide, a nitride, an oxide, an oxynitride, a carbonate, and a hydroxide. Examples of the lithium compound include lithium halides such as lithium fluoride, lithium nitride, lithium oxide, lithium carbonate, and lithium hydroxide. Examples of the calcium compound include calcium halides such as calcium fluoride, calcium oxide, calcium carbonate, calcium nitride, and calcium hydroxide.

[0030] The raw material composition may further include α-sialon or α-sialon activated with Ce. α-sialon or α-sialon activated with Ce can serve as an aggregate or a nucleus for obtaining the raw material sialon.

[0031] The raw material composition can be prepared, for example, by weighing and mixing each compound. The mixing ratio of each compound is designed according to the composition of the raw material sialon and the Ce-activated α-sialon phosphor, and the α-sialon contained therein. For mixing, a dry mixing method or a wet mixing method may be used. The dry mixing method, also called the dry blending method, may be a method of mixing each component using, for example, a V-type mixer or the like. The wet mixing method may be a method of adding a solvent or a dispersion medium such as water to prepare a solution or a slurry, mixing each component, and then removing the solvent or the dispersion medium. Also, after weighing and mixing each compound, the one with adjusted particle size may be used as the raw material composition. The adjustment of the particle size can be carried out, for example, by sieving.

[0032] The firing temperature of the raw material composition may be 1600 °C or higher, 1650 °C or higher, or 1700 °C or higher from the viewpoint of promoting the grain growth of the main crystal phase of α-sialon and making the solid solution amount of Ce more sufficient. Also, the firing temperature of the raw material composition may be 2000 °C or lower, 1900 °C or lower, or 1800 °C or lower from the viewpoint of sufficiently suppressing the decomposition of the main crystal phase of α-sialon. The firing temperature of the raw material composition may be, for example, 1600 to 2000 °C, 1650 to 1900 °C, or 1700 to 1800 °C.

[0033] The firing time of the raw material composition may be 1 hour or longer, 3 hours or longer, or 5 hours or longer from the viewpoint of promoting the growth of primary particles of α-sialon. Also, the firing time of the raw material composition may be 30 hours or shorter, 28 hours or shorter, or 25 hours or shorter from the viewpoint of economy.

[0034] The firing may be carried out, for example, in a nitrogen gas atmosphere. The nitrogen gas atmosphere may be at atmospheric pressure, but the decomposition of α-sialon generated at high temperatures can be suppressed by heating under conditions of high nitrogen pressure. Also, the firing may be carried out, for example, in a pressurized atmosphere. When the atmosphere is pressurized, the pressure may be 0.001 MPaG or higher, 0.005 MPaG or higher, 0.01 MPaG or higher, or 0.02 MPaG or higher. Also, the pressure may be 100 MPaG or lower, 50 MPaG or lower, 10 MPaG or lower, 5 MPaG or lower, or 1 MPaG or lower.

[0035] In the step of obtaining α-sialon, the number of firing times may be 1 time, or may be 2 times or more. The number of firing times may be, for example, 5 times or less, or 4 times or less. When the number of firing times is 2 times or more, the respective firing conditions may be the same as each other or may be different.

[0036] As the raw material sialon used for the heat treatment, the fired product obtained by the above method may be used as it is, or may be used after adjusting the particle size. The adjustment of the particle size can be carried out, for example, by crushing (coarse crushing) using a stamp mill or the like, pulverizing using a jet mill or the like, sieving using a vibrating sieve or the like.

[0037] <Heat treatment step> The manufacturing method has a step of heating (annealing) a mixture containing raw material sialon and a Eu source at 1200 to 1500°C to obtain a heat-treated product (hereinafter, also referred to as the "heat treatment step"). The inventors have found that by going through such a heat treatment step, a Ce-activated α-sialon phosphor excellent in internal quantum efficiency can be manufactured. The heating temperature of 1200 to 1500°C corresponds to a temperature lower than the general temperature as the firing temperature for obtaining raw material sialon from the above raw material composition. By heating at such a temperature, it is considered that the internal quantum efficiency can be further improved by suppressing the further progress of grain growth of the raw material sialon and reducing the density of crystal defects contained in the heat-treated product.

[0038] In particular, in the above heat treatment step, the internal quantum efficiency can be improved by heating the raw material sialon together with the Eu source. Generally, in an α-sialon phosphor, it is known that fluorescence appears in different wavelength ranges when Ce is used as the luminescence center element and when Eu is used. In a Ce-activated α-sialon phosphor, it is considered undesirable to use another element that emits fluorescence, such as Eu, in combination with Ce in order to obtain excellent luminescence characteristics, and it is avoided to add an element that can be another luminescence center element such as Eu in the manufacturing method of an α-sialon phosphor having Ce as the luminescence center. However, in the above heat treatment step, by deliberately heating the raw material sialon together with the Eu source, although the reason is not clear, it is considered that the internal quantum efficiency is improved because the reduction in the density of crystal defects proceeds more efficiently.

[0039] The mixture containing raw material sialon and a Eu source can be obtained, for example, by adding the Eu source to the raw material sialon and mixing them.

[0040] The Eu source means a compound or a single substance containing europium as a constituent element. In this specification, a compound containing europium as a constituent element is also referred to as a europium compound. Examples of europium compounds include europium oxides (europium oxide), europium hydroxides (europium hydroxide), europium nitrides (europium nitride), europium sulfides (europium sulfide), and europium halides (europium halide), etc. Examples of europium halides include europium fluoride, europium chloride, europium bromide, and europium iodide. In these compounds, the valence of europium may be trivalent or divalent. The europium compound may be, for example, one or more selected from the group consisting of europium oxides, nitrides, and halides. The europium compound preferably contains europium oxide.

[0041] The content of the Eu source in the above mixture may be 0.01 part by mass or more, 0.05 part by mass or more, 0.1 part by mass or more, or 0.3 part by mass or more with respect to 100 parts by mass of the raw material sialon content in the mixture. By setting the content of the Eu source within the above numerical range, the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. Also, the content of the Eu source in the above mixture may be 10.0 parts by mass or less, 8.0 parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, or 2.0 parts by mass or less with respect to 100 parts by mass of the raw material sialon content in the mixture. By setting the content of the Eu source within the above numerical range, the amount of heterophase that adversely affects the luminescence characteristics of the Ce-activated α-sialon phosphor can be reduced. The content of the Eu source in the mixture may be, for example, 0.01 to 10 parts by mass, 0.05 to 5.0 parts by mass, or 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the raw material sialon content in the mixture.

[0042] The heating temperature in the heat treatment step is 1200 - 1500 °C, but it may be 1250 °C or higher, or 1280 °C or higher. By setting the heating temperature within the above numerical range, the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. Also, the heating temperature may be 1450 °C or lower, 1400 °C or lower, or 1360 °C or lower. By setting the heating temperature within the above numerical range, the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. The heating temperature in the heat treatment step may be, for example, 1250 - 1450 °C, or 1250 - 1400 °C.

[0043] In the heat treatment step, the heat treatment may be performed in an atmosphere containing at least one selected from the group consisting of a noble gas and a reducing gas. Examples of the noble gas include argon gas and helium gas. The noble gas may be argon gas. Examples of the reducing gas include hydrogen gas, ammonia gas, hydrocarbon gas, and carbon monoxide gas. The reducing gas may be hydrogen gas. In the atmosphere in which the heat treatment is performed, the content of at least one selected from the group consisting of a noble gas and a reducing gas may be 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more based on the total volume of the atmosphere. Also, the content of argon gas may be 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more based on the total volume of the atmosphere.

[0044] The heat treatment may be performed in an atmosphere of atmospheric pressure or in a pressurized atmosphere. When it is in a pressurized atmosphere, the pressure may be, for example, 0.05 MPaG or lower, or 0.01 MPaG or lower. The pressure may be the same as the pressure during firing in the step of obtaining the above α-sialon, or may be smaller than the pressure during the firing.

[0045] The heating time in the heat treatment may be 2 hours or more, 4 hours or more, or 6 hours or more from the viewpoint of further enhancing the internal quantum efficiency improvement effect. Also, the heating time may be 24 hours or less, 20 hours or less, or 12 hours or less from the viewpoint of economy. The heating time may be, for example, 6 to 12 hours.

[0046] In the heat treatment step, the number of heat treatments may be 1 time, or may be 2 times or more. The number of heat treatments may be, for example, 5 times or less, or 4 times or less. When the number of heat treatments is 2 times or more, the type and content of the Eu source, the heating temperature, the heating atmosphere, and the heating time in each time may be the same or different from each other, and can be appropriately set within the above ranges. However, the heating temperature is at least in the range of 1200 to 1500 °C.

[0047] The manufacturing method according to one embodiment may further include steps other than the step of obtaining the above-described α-sialon and the heat treatment step. Examples of other steps include a step of treating the heat-treated product obtained by the above heat treatment with an acid (acid treatment step), and a step of classifying the heat-treated product or the acid-treated product (classification step).

[0048] <Acid treatment step> The acid treatment is performed by bringing the above heat-treated product into contact with an acid. Specifically, for example, it is performed by putting the heat-treated product into an acid and stirring. By performing the acid treatment, the amount of the altered phase formed by the heat treatment, the compound derived from the remaining Eu source, and the heterogeneous phase can be reduced, so that the internal quantum efficiency of the Ce-activated α-sialon phosphor can be further improved. An acid-treated product is obtained by the acid treatment step.

[0049] Examples of the acid used for the acid treatment include hydrofluoric acid (HF), nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and mixtures thereof (mixed acids). As the acid, for example, a mixed acid of HF and nitric acid may be used. In the mixed acid of HF and nitric acid, the mass ratio of the content of HF to the content of HNO3 may be, for example, 0.5 / 1 to 1 / 1.

[0050] The time for performing the acid treatment may be, for example, 10 minutes or more and 1 hour or less. Note that the time for performing the acid treatment means the time during which the above heat-treated product is in contact with the acid. Further, the acid treatment may be performed at room temperature or may be performed while heating. The temperature for performing the acid treatment may be, for example, 30°C or higher, 50°C or higher, or 70°C or higher. The temperature for performing the acid treatment may be 100°C or lower or 90°C or lower. Note that the temperature for performing the acid treatment means the temperature of the acid used for the acid treatment.

[0051] The number of times of the acid treatment may be 1 time or may be 2 times or more. The number of times of the acid treatment may be, for example, 5 times or less or 4 times or less. When the number of times of the acid treatment is 2 times or more, the treatment time, temperature, and type of acid in each time may be the same as or different from each other, and can be appropriately set within the above range. When the acid treatment is performed 2 times, for example, after the acid treatment using a mixed acid of hydrofluoric acid and nitric acid, the acid treatment using hydrochloric acid may be performed. According to such treatment, for example, non-solid-solved Eu in the heat-treated product can be removed by changing Eu to EuF3 with the mixed acid and then dissolving the EuF3 in hydrochloric acid.

[0052] <Classification step> The classification may be, for example, wet classification or dry classification. An example of wet classification is elutriation classification. In elutriation classification, for example, the heat-treated product or the acid-treated product is added to a mixed solvent containing ion-exchanged water and a dispersant (for example, sodium hexametaphosphate, etc.) or a mixed solvent containing ion-exchanged water and aqueous ammonia, stirred, and then allowed to stand to remove particles with a small particle diameter.

[0053] The Ce-activated α-sialon phosphor obtained by the above manufacturing method (hereinafter, also simply referred to as "Ce-activated α-sialon phosphor") contains Ce as a luminescence center element. The Ce-activated α-sialon phosphor may not substantially contain Eu as a luminescence center element, and may substantially contain only Ce as a luminescence center element. The fact that the Ce-activated α-sialon phosphor does not substantially contain Eu as a luminescence center element means that no emission peak derived from Eu is observed in the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm. Also, the fact that the Ce-activated α-sialon phosphor substantially contains only Ce as a luminescence center element means that only the peak derived from Ce is observed as a peak in the emission spectrum of the Ce-activated α-sialon phosphor when excited with light having a wavelength of 405 nm. For example, even if the Ce-activated α-sialon phosphor contains Eu, if the above-mentioned emission peak derived from Eu is not observed, in this specification, it shall be determined that Eu is not an element contained as a luminescence center element.

[0054] The Ce-activated α-sialon phosphor may contain M, Ce, Si, Al, O, and N as constituent elements. Here, M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). The contents of M, Ce, Si, Al, O, and N may be within the numerical ranges described as the contents of the respective elements based on the total content of M, Ce, Si, Al, O, and N in the raw material sialon described above. Here, the phrase "in the raw material sialon" shall be read as "in the Ce-activated α-sialon phosphor".

[0055] For example, in the case of a Ce-activated α-sialon phosphor, based on the total content of M, Ce, Si, Al, O, and N in the Ce-activated α-sialon phosphor, the content of the above M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 4 to 12 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol%, and the content of the above M is 1 to 4 mol%, the content of Ce is 0.05 to 2 mol%, the content of Si is 25 to 45 mol%, the content of Al is 5 to 9 mol%, the content of O is 0.5 to 5 mol%, and the content of N is 40 to 60 mol%.

[0056] The Ce-activated α-sialon phosphor may contain, as a main crystal, a crystal having the same crystal structure as α-sialon. The Ce-activated α-sialon phosphor may contain heterogeneous phases as long as the gist of the present disclosure is not impaired. In the powder X-ray diffraction pattern of the Ce-activated α-sialon phosphor, the ratio of the maximum diffraction line intensity of the heterogeneous phase to the diffraction line intensity of the (101) plane may be 10% or less, 5% or less, 3% or less, or 2% or less.

[0057] The Ce-activated α-sialon phosphor may contain, for example, an α-sialon represented by the following general formula (1). (M a+ x ,Ce 3+ y )Si 12-(m+n) Al (m+n) O n N 16-n (1) [In the general formula (1), M is at least one element selected from the group consisting of Li, Ca, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). When the valence of M is a, m = ax + 3y, Ce 3+ substitutes the M site, 0.3 ≤ x + y ≤ 2, 0.03 ≤ y ≤ 0.5, and 0 ≤ n ≤ m.]

[0058] The Ce-activated α-sialon phosphor may contain Ca and may contain an α-type sialon in which Ca is solid-dissolved. In the general formula (1) above, M may be Ca, or may be two or more elements including Ca and at least one element selected from the group consisting of Li, Mg, Y, and lanthanide elements (excluding La, Ce, and Eu). When M is Ca, in the general formula (1), a = 2. The fact that the Ce-activated α-sialon phosphor contains Ca can be confirmed by performing quantitative analysis of elements using an ICP emission spectroscopic analyzer.

[0059] In the general formula (1), x + y may be 0.4 or more, 0.5 or more, 0.6 or more, or 0.7 or more, and may be 1.8 or less, 1.5 or less, 1.3 or less, 1.1 or less, 1.0 or less, or 0.9 or less. In the general formula (1), y may be 0.05 or more, or 0.06 or more, and may be 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. In the general formula (1), n may be 0.01 or more, 0.05 or more, or 0.10 or more, and may be less than m.

[0060] The fact that the Ce-activated α-sialon phosphor contains the α-type sialon represented by the general formula (1) means that in the powder X-ray diffraction pattern of the Ce-activated α-sialon phosphor, the ratio of the maximum diffraction line intensity of the heterogeneous phase to the diffraction line intensity of the (101) plane is 10% or less, and the content ratios of the respective constituent elements (M, Ce, Si, Al, O, and N) calculated by analysis by an ICP emission spectroscopic analysis method using a multi-type ICP emission spectroscopic analyzer and analysis of the amounts of oxygen and nitrogen by an oxygen-nitrogen analyzer are equal to the ratios shown in the general formula (1).

[0061] The Ce-activated α-sialon phosphor may be represented by, for example, the above general formula (1). In this case, M, x + y, y, and n may be as described above. The constituent elements and ratios of the Ce-activated α-sialon phosphor can be determined by analyzing the amounts of oxygen and nitrogen using an oxygen-nitrogen analyzer and by ICP emission spectroscopic analysis using a multi-type ICP emission spectrometer. The fact that the Ce-activated α-sialon phosphor is represented by the above general formula (1) means that when the constituent elements and ratios of the Ce-activated α-sialon phosphor are determined by the above analysis, the content ratios of Ce, Si, Al, O, N, and M in the general formula (1) are equal to the ratios shown in the general formula (1), and the content rate of elements other than the above elements is 1.5% by mass or less.

[0062] The Ce-activated α-sialon phosphor may contain Eu. The content of Eu may be 0.0001% by mass (1 ppm by mass) or more, or 0.0002% by mass (2 ppm by mass) or more based on the total mass of the Ce-activated α-sialon phosphor. The content of Eu may be 5.0% by mass or less, 3.0% by mass or less, 1.5% by mass or less, or 1.5% by mass or less based on the total mass of the Ce-activated α-sialon phosphor. The content of Eu may be, for example, 0.0001 to 5.0% by mass, 0.0001 to 3.0% by mass, or 0.0001 to 1.5% by mass based on the total mass of the Ce-activated α-sialon phosphor. In this specification, the content of Eu means that which is obtained by performing quantitative analysis of elements using an ICP emission spectrometer. Specifically, the content of Eu is obtained by the method described in the examples. When the Ce-activated α-sialon phosphor contains Eu as a luminescence center element, the above content of Eu means the total amount of the content of Eu as a luminescence center element and the content of Eu that does not function as a luminescence center element.

[0063] When the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the wavelength at which the emission peak is located in the emission spectrum may be 470 to 525 nm. The lower limit value of the above wavelength range may be, for example, 480 nm or 490 nm. The upper limit value of the above wavelength range may be, for example, 520 nm or 510 nm. The above wavelength range corresponds to the range in which an emission peak is observed when the α-sialon phosphor is activated with Ce and is at least substantially not activated with Eu. When multiple peaks are observed in the emission spectrum when the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the peak with the highest intensity is treated as the "emission peak" in this specification. The emission peak wavelength is specifically determined by the method described in the examples of this specification.

[0064] When the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the full width at half maximum (FWHM) of the emission peak may be 100 nm or more, 101 nm or more, or 102 nm or more. The FWHM of the emission peak may be, for example, 150 nm or less, 130 nm or less, 120 nm or less, 115 nm or less, or 110 nm or less. In this specification, the full width at half maximum means the full width at half height. The full width at half maximum is specifically determined by the method described in the examples of this specification.

[0065] In the emission spectrum when the Ce-activated α-sialon phosphor is excited with light having a wavelength of 405 nm, the ratio of the emission intensity observed at a wavelength of 580 nm to the intensity of the emission peak (emission intensity observed at a wavelength of 580 nm / intensity of the emission peak. Hereinafter, also simply referred to as "ratio of emission intensity") may be less than 90%, less than 70%, less than 60%, less than 50%, less than 45%, less than 40%, less than 35%, or less than 30%. The ratio of emission intensity may be, for example, 0% or more, or 10% or more. In the above emission spectrum, emission derived from Ce is observed around 470 to 525 nm, and emission derived from Eu is considered to be observed around 580 nm. Therefore, particularly when the wavelength at which the emission peak is located is 470 to 525 nm, the small ratio of the emission intensity means that the amount of Eu contained as the emission center element is small relative to the amount of Ce contained as the emission center element. The ratio of emission intensity is specifically determined by the method described in the examples of this specification.

[0066] The α-sialon phosphor obtained by the above manufacturing method is excellent in internal quantum efficiency. The internal quantum efficiency when the α-sialon phosphor obtained by the above manufacturing method is excited with light having a wavelength of 405 nm can be, for example, 75.0% or more, 76.0% or more, 77.0% or more, 78.0% or more, or 79.0% or more. The above manufacturing method can also be regarded as a method for improving the internal quantum efficiency of the α-sialon phosphor. The method for improving the internal quantum efficiency of the phosphor includes, for example, heat-treating a mixture containing α-sialon activated with Ce and a Eu source at 1200 to 1500 °C to obtain a heat-treated product. As specific embodiments and the like in this method, each embodiment in the above manufacturing method can be applied without particular limitation.

[0067] In this specification, the internal quantum efficiency means the internal quantum efficiency calculated based on the data of the emission spectrum obtained when the phosphor is excited with light having a wavelength of 405 nm. The internal quantum efficiency is specifically determined by the method described in the examples of this specification.

[0068] The absorption rate of the Ce-activated α-sialon phosphor for light with a wavelength of 405 nm may be 65.0% or more, 70.0% or more, 72.0% or more, or 75.0% or more. The absorption rate of the Ce-activated α-sialon phosphor for light with a wavelength of 405 nm may be 100.0% or less, 90.0% or less, or 80.0% or less.

[0069] The absorption rate of light with a specific wavelength means the one determined as follows. First, attach the phosphor to the opening of the integrating sphere, introduce light with a specific wavelength into the integrating sphere as excitation light, and measure the emission spectrum using a spectrophotometer. From the obtained emission spectrum data, calculate the number of excitation reflected photons (Qref) and the number of fluorescence photons (Qem). Also, measure the spectrum of the excitation light in the same manner as above except that a standard reflector is attached to the opening of the integrating sphere instead of the phosphor. Calculate the number of excitation light photons (Qex) from the obtained spectrum data. Then, calculate the absorption rate of light with a specific wavelength according to the following formula. Absorption rate of light with a specific wavelength = ((Qex - Qref) / Qex) × 100 Specifically, the absorption rate of light with a specific wavelength is determined by the method described in the examples of this specification. As the spectrophotometer, "MCPD-7000" (trade name) manufactured by Otsuka Electronics Co., Ltd. etc. can be used.

[0070] The above Ce-activated α-sialon phosphor may have an absorption rate of light with a wavelength of 405 nm of 65.0% or more and an internal quantum efficiency of 76.0% or more. From the viewpoint of practical use, the absorption rate of light with a wavelength of 405 nm may be 72.0% or more and the internal quantum efficiency may be 78.0% or more.

[0071] The Ce-activated α-sialon phosphor may be used alone or in combination with other phosphors. Since the Ce-activated α-sialon phosphor has excellent internal quantum efficiency, it can be suitably used, for example, in light-emitting devices such as LEDs. The Ce-activated α-sialon phosphor can also be used, for example, by being dispersed in a cured resin. As the cured resin, for example, a resin used as a sealing resin for a light-emitting device etc. can be used.

[0072] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments at all. Also, the description contents of the above-described embodiments can be applied to each other.

Example

[0073] Hereinafter, the content of the present disclosure will be described in more detail with reference to Examples and Comparative Examples. However, the present disclosure is not limited to the following Examples.

[0074] [Production of raw material sialon] [Production of raw material sialon A] The design composition was set to Ca 0.645 Ce 0.07 Si 9.75 Al 2.25 O 0.75 N 15.25 Raw material powder a having a blending composition of 52.3 mol% of silicon nitride powder (manufactured by UBE Industries, Ltd., E10 grade), 36.2 mol% of aluminum nitride powder (manufactured by Tokuyama Corporation, E grade), 1.1 mol% of cerium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., C type), 2.6 mol% of calcium fluoride powder (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), and 7.8 mol% of calcium carbonate powder (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) was prepared. In the raw material powder a, the content of calcium fluoride powder (CaF2 / (CaF2 + CaCO3)) based on the total amount of calcium compounds was 25 mol%. The blending composition was calculated so that calcium fluoride and calcium carbonate satisfied the above design composition in terms of the same number of moles of calcium as calcium oxide. The raw material powder a was bag-mixed for several minutes, and the obtained mixture was passed through a nylon sieve (mesh size: 150 μm) to obtain a raw material composition.

[0075] 35 g of the above raw material composition was filled into a boron nitride crucible with an inner diameter of 60 mm and a height of 30 mm, and fired in a nitrogen gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater. The firing temperature was 1750 °C, and the firing time was 8 hours. The obtained fired product was crushed by a stamp mill (manufactured by Nippon Tokushu Kagaku Co., Ltd., high-speed stamp mill ANS-143PL) so that all of the fired product passed through a sieve (mesh size: 250 μm), thereby obtaining raw material sialon A (the phosphor of Comparative Example 1).

[0076] <Preparation of Raw Material Sialon B> A raw material composition was obtained in the same manner as in the above <Preparation of Raw Material Sialon A>, except that the blending amount of calcium fluoride powder was 5.2 mol% and the blending amount of calcium carbonate powder was 5.2 mol% (CaF2 / (CaF2 + CaCO3) = 50 mol%). 300 g of this raw material composition was filled into a boron nitride crucible with an inner diameter of 150 mm and a height of 55 mm, and fired at 1750 °C for 16 hours in a nitrogen gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater to obtain a fired product. The obtained fired product was roughly crushed by a stamp mill and then crushed by a jet mill (manufactured by Nippon Pneumatic Mfg. Co., Ltd., PJM-80, sample feed rate: 50 g / min, crushing pressure: 0.2 MPa), and then passed through a vibrating sieve (mesh size: 45 μm). The powder that passed through the vibrating sieve was recovered as raw material sialon B (the phosphor of Comparative Example 3).

[0077] <Preparation of Raw Material Sialon C> A raw material composition was obtained in the same manner as in the above <Preparation of Raw Material Sialon B>, except that calcium carbonate powder was changed to calcium oxide (obtained by decarbonating calcium carbonate powder by treating it in the atmosphere at 1000 °C for 8 hours). 200 g of this raw material composition was filled into a boron nitride crucible with an inner diameter of 100 mm and a height of 85 mm, and fired at 1750 °C for 24 hours in a nitrogen gas atmosphere of 0.03 MPaG using an electric furnace equipped with a carbon heater to obtain a fired product. For the obtained fired product, rough crushing, crushing, and sieving treatment were performed in the same procedure as in the above <Preparation of Raw Material Sialon B> to obtain raw material sialon C (the phosphor of Comparative Example 7).

[0078] <Production of starting material sialon D> Except that calcium carbonate powder was changed to calcium oxide, firing, crushing, grinding, and sieving were performed in the same manner as in the above <Production of starting material sialon B> to obtain starting material sialon D (the phosphor of Comparative Example 8).

[0079] <Production of starting material sialon E> Except that the starting material powder obtained by adding 0.5% by mass of europium oxide powder (RU grade, manufactured by Shin-Etsu Chemical Co., Ltd.) to the starting material powder used in the above <Production of starting material sialon D> was used, starting material sialon E (the phosphor of Comparative Example 12) was obtained in the same manner as in the above <Production of starting material sialon D>.

[0080] [Treatment of starting material sialon] For starting material sialons A to E, as shown in Tables 1 to 2, phosphors of Comparative Examples 2, 4 to 6, 9 to 11 and Examples 1 to 8 were obtained by subjecting them to one or more of the following heat treatment, acid treatment, and elutriation treatment. The phosphors of Examples 1 to 8 contained α-sialon represented by the following general formula (1-1). (Ca 2+ x ,Ce 3+ y )Si 12-(m+n) Al (m+n) O n N 16-n (1-1) [In the general formula (1-1), m = 2x + 3y, Ce 3+ replaces the Ca site, 0.7 ≤ x + y ≤ 0.9, 0.03 ≤ y ≤ 0.08, and 0 ≤ n ≤ m / 2.]

[0081] <Heat treatment> For Comparative Examples 4 to 6 and 9 to 10, the α-sialons shown in Tables 1 to 2 were heat-treated in an argon gas atmosphere of 0.03 MPaG at the temperatures described in Tables 1 to 2 using an electric furnace equipped with a carbon heater. The heating time was 8 hours. For Examples 1 to 8, europium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., RU grade) in the amounts shown in Tables 1 to 2 was added as a Eu source to the α-sialons shown in Tables 1 to 2, and the resulting mixtures were heat-treated in the same manner as above. The amounts of the Eu source described in Tables 1 to 2 mean the amounts based on the total mass of each α-sialon. For Comparative Example 11, cerium oxide powder (manufactured by Shin-Etsu Chemical Co., Ltd., C type) instead of europium oxide powder was added in an amount of 1% by mass based on the total mass of the raw material sialon D, and the resulting mixture was heat-treated in the same manner as above.

[0082] <Acid treatment> When the heat treatment was "present", the heat-treated product obtained by the heat treatment was put into a mixed acid of hydrofluoric acid and nitric acid (48 mass% concentrated hydrofluoric acid: 60 mass% concentrated nitric acid: water = 1:1:6 (volume ratio)) heated to 80 °C, and the α-sialons shown in Tables 1 to 2 were used when the heat treatment was "absent", and stirred for 30 minutes. Then, filtration, washing with water, and drying were performed to recover the acid-treated product.

[0083] <Classification (elutriation)> In Examples 2 and 6, the fine powder contained in the acid-treated product obtained after the acid treatment was removed by sedimentation classification. More specifically, first, water containing a small amount of a dispersant was prepared in a beaker. The acid-treated product was dispersed in the water, allowed to stand for a predetermined time, and then the supernatant liquid from the water surface to a predetermined height was removed by a liquid feed pump. Then, a predetermined amount of water containing a small amount of the above dispersant was added to the beaker, and dispersion, standing, and supernatant removal were repeated to remove the fine powder. The predetermined time and the predetermined height were adjusted so that fine powder with a particle size of less than 7.5 μm was removed in Example 2 and fine powder with a particle size of less than 5 μm was removed in Example 6 according to Stokes' formula.

[0084] [Evaluation] <Excitation Light Absorption Rate, Fluorescence Characteristics, and Chromaticity x and Chromaticity y> For the phosphors of each comparative example and example, the excitation light absorption rate, emission peak wavelength, full width at half maximum of the emission peak, ratio of emission intensity, internal quantum efficiency, and external quantum efficiency when the excitation wavelength was 405 nm were calculated by the following procedure. The results are shown in Tables 1 to 2.

[0085] First, the phosphor to be measured was filled in a concave cell so that the surface was smooth and attached to the opening of the integrating sphere. Monochromatic light spectrally separated from a Xe lamp, which is an emission light source, to a wavelength of 405 nm was introduced into the integrating sphere as excitation light for the phosphor using an optical fiber. The phosphor to be measured was irradiated with this monochromatic light as excitation light, and the emission spectrum was measured. A spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., product name: MCPD-7000) was used for the measurement. Among the emission spectra obtained above, the spectra of the phosphors of Comparative Examples 7 and 12 and Examples 1 and 2 are shown in FIG. 1.

[0086] From the data of the obtained emission spectrum, the emission peak wavelength and the full width at half maximum (full width at half maximum) were determined. Also, from the data of the obtained emission spectrum, the fluorescence intensity (intensity of the emission peak) at the emission peak wavelength and the fluorescence intensity at 580 nm were determined, and the ratio of the emission intensity was determined by the following formula. The intensity of the emission observed at 580 nm is adopted as an index of the emission derived from Eu. Ratio of emission intensity = (Emission intensity at 580 nm) / (Intensity of the emission peak) × 100

[0087] Furthermore, from the data of the obtained emission spectrum, the number of excitation reflected light photons (Qref) and the number of fluorescence photons (Qem) were calculated. The number of excitation reflected light photons was calculated in the same wavelength range as the number of excitation light photons, and the number of fluorescence photons was calculated in the range of 415 to 800 nm. Also, using the same apparatus, a standard reflector (manufactured by Labsphere, Spectralon (registered trademark)) with a reflectivity of 99% was attached to the opening of the integrating sphere, and the spectrum of the excitation light with a wavelength of 405 nm was measured. At that time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 400 to 415 nm.

[0088] Based on the above calculation results, the absorption rate of the phosphor to be measured for the 405 nm excitation light, the internal quantum efficiency, and the external quantum efficiency were determined according to the following calculation formulas. Absorption rate of 405 nm excitation light = ((Qex - Qref) / Qex) × 100 Internal quantum efficiency = (Qem / (Qex - Qref)) × 100 External quantum efficiency = (Qem / Qex) × 100 Note that the relational expressions among the external quantum efficiency, the absorption rate of the 405 nm excitation light, and the internal quantum efficiency can be expressed as follows from the above formulas. External quantum efficiency = Absorption rate of 405 nm excitation light × Internal quantum efficiency

[0089] Also, from the spectral data in the wavelength range of 415 to 800 nm of the obtained emission spectrum, the x value (chromaticity x) of the CIE chromaticity coordinates and the y value (chromaticity y) of the CIE chromaticity coordinates in the XYZ colorimetric system defined in JIS Z 8781-3:2016 "Colorimetry - Part 3: CIE tristimulus values" were calculated in accordance with JIS Z 8724:2015 "Method of measuring color - Light source color" to obtain the chromaticity x and the chromaticity y.

[0090] Note that for the standard sample of Eu-activated β-sialon phosphor (manufactured by Sialon Co., Ltd., Standard Phosphor Gree, Lot No. NSG1301. The absorption rate, internal quantum efficiency, and external quantum efficiency of the 405 nm excitation light measured by the method conforming to ISO24936 are 81%, 81%, and 65% respectively), the absorption rate of the 405 nm excitation light, the internal quantum efficiency, the external quantum efficiency, and the chromaticity x and chromaticity y were measured in accordance with the above measurement method. As a result, the absorption rate of the 405 nm excitation light was 83.5%, the internal quantum efficiency was 83.0%, the external quantum efficiency was 69.3%, the chromaticity x was 0.347, and the chromaticity y was 0.628.

[0091] Each measured value regarding the excitation light absorption rate, fluorescence characteristics, and chromaticity x and chromaticity y may vary when the manufacturer of the measuring device, the manufacturing lot number, etc. change. Therefore, as various measured values, the values measured by the measuring method described in this specification are adopted. However, when changing the manufacturer of the measuring device, the manufacturing lot number, etc., it is also possible to correct each measured value using the measured value of the above-described standard sample as a reference value.

[0092] <Diffuse reflectance> The diffuse reflectance of the phosphors of each comparative example and example was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, trade name: V-550) with an integrating sphere device (trade name: ISV-469) attached. After performing baseline correction with the standard reflector attached to the device, a solid sample holder filled with the phosphor to be measured was attached to the spectrophotometer, and the diffuse reflectance was measured in the wavelength range of 220 to 850 nm. Among the measurement results, the peak wavelength of the emission spectrum of each phosphor and the values of the diffuse reflectance at 600 nm, 700 nm, and 800 nm were recorded. The results are shown in Tables 1 to 2.

[0093] <Absorption rate of light at 600 nm and 700 nm> When measuring the emission spectrum, instead of the monochromatic light spectrally separated from the Xe lamp to a wavelength of 405 nm, monochromatic light spectrally separated from the Xe lamp to a wavelength of 600 nm or 700 nm was used respectively, and in addition to measuring the spectrum of the excitation light with a wavelength of 405 nm, the absorption rate of light at 600 nm and 700 nm was measured in the same manner as the above excitation light absorption rate except that the spectrum of the excitation light with a wavelength of 600 nm or 700 nm was measured. The results are shown in Tables 1 to 2.

[0094]

Table 1

[0095]

Table 2

[0096] <Eu content> For the phosphors of Examples 3 to 6, 8 and Comparative Example 12, the Eu content was determined. The Eu content was determined using an ICP emission spectrometer. For quantification of 0.1% or more, the phosphor was dissolved by an alkali fusion method to prepare a sample solution, and for quantification of less than 0.1%, a pressurized acid decomposition method was used. Using an ICP emission spectrometer (manufactured by Agilent, trade name: 5110VDV), quantitative analysis of europium was performed on the obtained sample solution. The Eu content was calculated from the obtained results. Also, for Examples 3 to 8 and Comparative Example 12, the phosphor was treated for 30 minutes with 18 mass% hydrochloric acid heated to 80°C (hydrochloric acid washing). For Examples 3 to 6, 8 and Comparative Example 12, the Eu content was measured after hydrochloric acid washing. The results are shown in Table 3. Note that the Eu content described in Table 3 means the mass ratio based on the total mass of each phosphor. Also, for Examples 3, 4, 6 to 8 and Comparative Example 12, the excitation light absorption rate, fluorescence characteristics, chromaticity, and the absorption rates of light at 600 nm and 700 nm after hydrochloric acid washing, as well as the change amount (value after hydrochloric acid washing - value before hydrochloric acid washing) of these values from the values before hydrochloric acid washing, are shown in Table 4.

[0097]

Table 3

[0098]

Table 4

[0099] For the phosphors of Examples 3 to 5, 6, and 8, the Eu content changed significantly before and after hydrochloric acid washing. On the other hand, for the phosphor of Comparative Example 12, no significant change in the Eu content was observed before and after hydrochloric acid washing. For Comparative Example 12, Eu has entered into the α-type sialon crystal in the Ce-activated α-sialon phosphor due to the addition of a Eu source during the production of Ce-activated α-sialon, while in the phosphors of Examples 3 to 5, 6, and 8, it is considered that Eu has not entered into the α-type sialon crystal.

Claims

Claim 1 A method for manufacturing a Ce-activated α-sialon phosphor, comprising a step of heat-treating a mixture containing Ce-activated α-sialon and a Eu source at 1200 to 1500 °C to obtain a heat-treated product. Claim 2 The manufacturing method according to claim 1, wherein the content of the Eu source in the mixture is 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the content of the Ce-activated α-sialon. Claim 3 The manufacturing method according to claim 1 or 2, wherein the heat treatment is performed in an atmosphere containing at least one selected from the group consisting of a noble gas and a reducing gas. Claim 4 The manufacturing method according to claim 1 or 2, further comprising a step of acid-treating the heat-treated product. Claim 5 The manufacturing method according to claim 1 or 2, further comprising a step of obtaining the Ce-activated α-sialon by firing a raw material composition containing an Si source, an Al source, and a Ce source.

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