Phosphor, method for producing phosphor, and light-emitting device

Abstract

The present invention provides: a phosphor including a garnet crystal phase having a composition represented by formula [α] [CexA1-x]3D2E3O12 (A represents at least one selected from Ca, Mg, and Sr, D represents at least one selected from Al, Ga, and In, E represents at least one selected from Si and Ge, and x represents a positive number that satisfies formula 0<x≤0.3); a method for producing said phosphor, the method comprising a formulation step for preparing raw materials formulated so as to achieve an elemental proportion of the composition represented by formula [α], a mixing step for mixing the raw materials to obtain a mixture, and a high pressure synthesis step for subjecting the mixture to high pressure synthesis to obtain the intended phosphor; and a light-emitting device comprising said phosphor and an excitation light source that emits light for exciting the phosphor. The present invention provides: a Ce3+ activated garnet phosphor that has a composition having less content of rare-earth elements or not containing a rare-earth element, that is stable under ordinary temperatures and ordinary pressures, and that has excellent light emission properties; a method for producing the same; and the like.

Description

Phosphor, Method for Producing Phosphor, and Light-Emitting Device

[0001] The present invention relates to a phosphor, a method for producing a phosphor, and a light-emitting device.

[0002] Garnet phosphor is a phosphor having a garnet crystal phase (garnet-type crystal structure). For example, Y ３ Al ５ O １２ In the garnet host crystal of, Ce ３＋ activated YAG (Yttrium Aluminum Garnet) phosphor absorbs blue light and exhibits yellow light emission with high wavelength conversion efficiency. Thus, it is known that by combining with a blue LED, a high-brightness white LED can be realized.

[0003] In relation to the present invention, Patent Document 1 discloses a light-emitting device using Ce ３＋ activated Lu ３ Ga ２ (AlO ４ ) ３ or Ce ３＋ activated Lu ２ CaMg ２ (SiO ４ ) ３ garnet phosphor.

[0004] Further, Patent Document 2 discloses, as an example of a green phosphor, Ce ３＋ activated Ca ３ Sc ２ Si ３ O １２ garnet phosphor.

[0005] Japanese Patent No. 7022914 Japanese Patent No. 6723939

[0006] As described in Patent Documents 1 and 2, the host crystal of the Ce ３＋ activated garnet phosphor generally widely used in light-emitting devices and the like contains rare earths such as Sc, Y, Gd, La, and Lu. When the composition of the host crystal contains rare earths, Ce ３＋Activated garnet phosphors are readily available. However, these rare earth raw materials are imported from specific producing countries, making stable supply difficult and posing a high supply risk. Therefore, there is a need to develop novel phosphors with reduced or no rare earth content and superior luminescence properties.

[0007] This invention has been made in view of the above circumstances, and has a composition in which the rare earth content is reduced or does not contain rare earths, is stable at room temperature and pressure, and has excellent luminescence properties. ３＋ Activated garnet phosphor and method for producing the same, and the Ce ３＋ The objective is to provide a light-emitting device that uses activated garnet phosphor as a light-emitting material.

[0008] The inventors diligently conducted research to solve the above problems. As a result, they found that Ce can be added to a garnet matrix crystal that contains a specific element but does not contain rare earth elements. ３＋ Ce obtained by adding ３＋ We discovered that the activated garnet phosphor is stable at room temperature and pressure and possesses excellent luminescence properties, which led to the completion of the present invention.

[0009] Thus, the present invention provides the phosphors described in [1] to [3] below, the methods for producing the phosphors described in [4] and [5], and the light-emitting device described in [6].

[0010] [1] A phosphor containing a garnet crystalline phase having a composition represented by the following formula [α].

[0011]

[0012] (In the above formula [α], A is at least one element selected from the group consisting of Ca, Mg, and Sr, D is at least one element selected from the group consisting of Al, Ga, and In, E is at least one element selected from the group consisting of Si and Ge, and x is a positive number satisfying the formula: 0 < x ≤ 0.3.) [2] The phosphor according to [1], characterized in that the excitation wavelength peak is located in the range of 410 nm to 490 nm, and the emission wavelength peak is located in the range of 480 nm to 650 nm. [3] The fluorescence lifetime at 300 K is τ３００ , the fluorescence lifetime at 800K is τ ８００ When this is the case, τ ３００ The interval is between 40 ns and 100 ns, and 0.8 ≤ τ ８００ / τ ３００ A phosphor according to [1], characterized in that it satisfies ≤ 1.2. [4] A method for producing a phosphor according to any one of [1] to [3], comprising: a preparation step (S101) of preparing raw materials prepared to have an elemental ratio of the composition represented by the formula [α]; a mixing step (S102) of mixing the raw materials to obtain a mixture; and a high-pressure synthesis step (S103) of synthesizing the mixture under high pressure to obtain a phosphor having a garnet crystal structure. [5] A method for producing a phosphor according to [4], characterized in that the conditions for the high-pressure synthesis reaction in the high-pressure synthesis step (S103) are a temperature of 1200°C or more and 1600°C or less, and a pressure of 1 GPa or more and 20 GPa or less. [6] A light-emitting device comprising: a phosphor according to any one of [1] to [3]; and an excitation light source for irradiating the phosphor with light to excite it.

[0013] According to the present invention, Ce has a composition in which the rare earth content is reduced or does not contain rare earth elements, is stable at room temperature and pressure (10 to 50°C, atmospheric pressure, the same applies hereafter), and has excellent luminescence properties. ３＋ Activated garnet phosphor and method for producing the same, and the Ce ３＋ A light-emitting device is provided that uses an activated garnet phosphor as a light-emitting material.

[0014] This is a flowchart showing the method for manufacturing a phosphor according to the embodiment. This is a diagram showing the Rietveld analysis results of the X-ray diffraction pattern of the phosphor according to the example. This is a diagram showing the excitation spectrum and emission spectrum of the phosphor according to the example. This is a diagram showing the temperature characteristics of the emission spectrum of the phosphor according to the example.

[0015] The present invention will be described in detail below, divided into three sections: 1) phosphor, 2) method for producing the phosphor, and 3) light-emitting device.

[0016] 1) Phosphor The phosphor according to the embodiment of the present invention is a phosphor comprising a garnet crystal phase having a composition represented by the following formula [α], that is, Ce having a composition represented by the following formula [α] ３＋ It is an activated garnet phosphor (a fluorescent material having a garnet structure).

[0017]

[0018] Ce having the composition represented by the above formula [α] ３＋ The activated garnet phosphor is given by formula [β]

[0019]

[0020] This substance is obtained by adding Ce, an activating substance, to a matrix crystal having the composition represented by the above formula [α]. In the above formula [α], Ce(Ce ３＋ ) is A (A) in the matrix crystal ２＋ It is an activating substance that is substituted with the element of ).

[0021] The presence of a garnet crystalline phase in a phosphor having the composition represented by the above formula [α] can be confirmed, for example, by powder X-ray diffraction (XRD).

[0022] In formula [α], the amount of Ce in the activating substance x is a positive number satisfying 0 < x ≤ 0.3. Since it is necessary to include Ce to obtain luminescence, x is greater than 0. From the viewpoint of increasing luminescence intensity, x is preferably 0.0003 or more, more preferably 0.015 or more. As long as the phosphor can emit light, there is no particular limit to the maximum value of x. However, if x becomes too large, the luminescence intensity will decrease due to concentration quenching. Therefore, by setting x to 0.3 or less, the decrease in luminescence intensity can be suppressed. Also, from the viewpoint of increasing luminescence intensity, x is preferably 0.1 or less, more preferably 0.05 or less.

[0023] Element A, which constitutes the matrix crystal, is at least one element selected from the group consisting of Ca, Mg, and Sr, with Ca being preferred. Element D, which constitutes at least one element selected from the group consisting of Al, Ga, and In, with Al being preferred. Element E, which constitutes at least one element selected from the group consisting of Si and Ge, with Si being preferred. By appropriately selecting elements A, D, and E from the above groups, the crystal field within the garnet crystal structure changes, allowing for control of the excitation and emission wavelengths of the phosphor.

[0024] As a matrix crystal having the composition shown by the above formula [β], from the viewpoint of easily obtaining a phosphor that is stable at room temperature and atmospheric pressure (does not decompose and change into a different crystal structure) and has excellent luminescence properties, formula: A ３ D ２ Si ３ O １２ A composition represented by formula: A is preferred. ３ Al ２ Si ３ O １２ The composition shown by formula: Ca ３ D ２ Si ３ O １２ The composition shown in formula [β] is particularly preferred. In formula [β], the valencies of each element (A, D, E, Ce) are as follows: ２＋ , D ３＋ , E ４＋ Ce ３＋ (This is the same in equation [α].)

[0025] In the phosphor of the present invention, the peak of the excitation wavelength of the phosphor (the wavelength of light required to excite the phosphor) is preferably in the range of 410 nm to 490 nm. Furthermore, the peak of the emission wavelength of the phosphor (the wavelength of light emitted when returning from the excited state to the original state (ground state)) is preferably located in the range of 480 nm to 650 nm. Phosphors with excitation and emission wavelengths within these ranges are suitably used as light emitters in the light-emitting devices of the present invention, which will be described later.

[0026] The excitation wavelength peaks and emission wavelength peaks of a phosphor can be determined by measuring the fluorescence spectrum of the phosphor, converting the X-axis from wavelength (nm) to energy (eV), fitting it with a Gaussian function, and then converting the resulting energy back to wavelength. Alternatively, this can be done by reading the wavelength of maximum emission intensity from the fluorescence spectrum where the X-axis is wavelength.

[0027] Furthermore, the matrix crystal having the composition shown by formula [β] does not contain rare earth elements (Sc, Y, Gd, La, Lu). Generally, garnet matrix crystals and their activators (activated garnet phosphors) having compositions that do not contain rare earth elements are often unstable at room temperature and atmospheric pressure (they cannot be synthesized at atmospheric pressure, or if synthesized they decompose), but the phosphor of the present invention is stable at room temperature and atmospheric pressure (it can exist without decomposing after synthesis). In addition, because it does not contain rare earth elements, the raw materials for production can be obtained cheaply, and a stable supply can be ensured.

[0028] The fluorescence lifetime (time taken for the phosphor to reach 1 / e after excitation) τ of the phosphor according to the embodiment of the present invention may be less than or equal to 100 ns. The fluorescence lifetime (τ) of the phosphor can be determined by obtaining fluorescence decay data using a time-resolved fluorescence measurement method and using a single exponential function: I(t) = Aexp(-t / τ) [wherein I(t) is the fluorescence intensity at time (t) and A is the initial fluorescence intensity].

[0029] The phosphor of the present invention has a fluorescence lifetime at 300K τ ３００ , the fluorescence lifetime at 800K is τ ８００ When this is the case, τ ３００ The interval is between 40 ns and 100 ns, and 0.8 ≤ τ ８００ / τ ３００ It is preferable that the condition ≤ 1.2 is satisfied. ３００ A shorter duration is preferable because it increases the transition probability. ３００ and τ ８００ Phosphors having this relationship are useful as light-emitting elements in the light-emitting devices described later. Furthermore, the fluorescence lifetime at temperature K is τ Ｋ In this case, 0.8 ≤ τ Ｋ / τ ３００The higher the temperature K that satisfies ≤ 1.2, the more preferable. Fluorescence lifetime τ of the phosphor. ３００ , τ ８００ , τ Ｋ This can be measured by the method described in the examples.

[0030] Fluorescence lifetime affects brightness saturation characteristics. Conventional Eu-activated phosphors have a longer fluorescence lifetime compared to Ce-activated phosphors. Therefore, Eu-activated phosphors are prone to brightness saturation due to a decrease in quantum efficiency at high-power excitation. Accordingly, the Ce-activated garnet phosphor according to the embodiment of the present invention is promising as a green phosphor with high quantum efficiency even at high power compared to conventional Eu-activated phosphors.

[0031] 2) Method for producing Ce-activated garnet phosphor The production method according to this embodiment is a method for producing Ce-activated garnet phosphor according to the present invention. As shown in Figure 1, the production method according to this embodiment comprises a preparation step (S101), a mixing step (S102), and a high-pressure synthesis step (S103).

[0032] According to the phosphor manufacturing method of this embodiment, a Ce-activated garnet phosphor that is stable at room temperature and atmospheric pressure, has excellent luminescence properties, and whose matrix crystal is rare earth-free can be efficiently and stably produced.

[0033] [Preparation Step (S101)] First, a raw material containing at least one element A selected from the group consisting of Ca, Mg, and Sr, a raw material containing at least one element D selected from the group consisting of Al, Ga, and In, a raw material containing at least one element E selected from the group consisting of Si and Ge, and a raw material containing the activating substance Ce are prepared and prepared to have a composition represented by the following formula [α].

[0034]

[0035] In formula [α], x is a positive number satisfying 0 < x ≤ 0.3. More preferably, x satisfies 0.0003 < x ≤ 0.2, and even more preferably, 0.015 ≤ x ≤ 0.05. By having x in this range, a Ce-activated garnet phosphor with excellent luminescence properties can be obtained.

[0036] The raw materials for each element (A, D, E, Ce) are not particularly limited. Examples include elemental elements, oxides, nitrides, hydroxides, chlorides, halides such as fluorides, inorganic salts such as sulfates, nitrates, and phosphates, and organic acid salts such as acetates. In addition, compounds containing two or more of the above-mentioned elements may be used. Furthermore, each compound may be in the form of a hydrate.

[0037] There are no particular restrictions on how each raw material is obtained, and commercially available products can be used as is. There are no particular restrictions on the purity of each raw material, but from the viewpoint of strictly controlling the elemental ratio and avoiding the appearance of different phases due to impurities, higher purity is preferable. The purity of the raw materials is usually 90 mol% or more, preferably 95 mol% or more, more preferably 97 mol% or more, and even more preferably 99 mol% or more. There is no particular upper limit, but it is usually 100 mol% or less, and may contain impurities that are inevitably mixed in.

[0038] In addition to the raw materials for each element, a flux may also be included. By including a flux, the reaction of each compound is further promoted, and the solid-phase reaction proceeds more uniformly, making it possible to produce a calcined product with a large particle size and superior luminescence properties of garnet phosphors.

[0039] Examples of fluxes that can be used include halides containing at least one element selected from the group consisting of alkaline earth metal elements and alkali metal elements. Specifically, LiF, LiCl, etc., can be used.

[0040] The flux can be added in such a way that it becomes part of the elements of the desired composition of the resulting heat-treated product, or it can be added by further adding it to a raw material mixture that has been weighed to achieve the desired composition of the resulting heat-treated product.

[0041] [Mixing process (S102)] Next, the raw materials prepared in the preparation process (S101) are mixed to obtain a mixture. Mixing is carried out by common mixing methods such as wet mixing, dry mixing, or ball milling.

[0042] [High-Pressure Synthesis Process (S103)] Next, a high-pressure synthesis reaction is carried out on the raw materials mixed in the mixing process (S102). The method of pressurization is not particularly limited, and methods such as heating a sealed container, mechanically pressurizing, isotropically pressurizing using water pressure, or using gas pressure can be used.

[0043] The conditions for the high-pressure synthesis reaction are, for example, 1200°C to 1600°C and 1 GPa to 20 GPa. If the synthesis temperature is lower than 1200°C, the solid-phase reaction is less likely to occur. On the other hand, if the temperature is higher than 1600°C, the raw materials may melt and vitrify, or high-temperature crystalline phases may precipitate, making it difficult to obtain garnet crystals. Furthermore, if the synthesis pressure is lower than 1 GPa, crystalline phases such as gehlenite, wollastonite, and anorthite will precipitate, and if it exceeds 20 GPa, crystalline phases such as perovskite will precipitate, making it difficult to obtain the desired garnet crystalline phase.

[0044] As described above, a Ce-activated garnet phosphor with a rare earth-free matrix crystal that satisfies formula [α] can be obtained. The obtained phosphor may be subjected to post-treatment such as classification and washing by conventional methods.

[0045] 3) Light-emitting device The light-emitting device according to this embodiment comprises the Ce-activated garnet phosphor of the present invention and an excitation light source that irradiates the phosphor with light to excite it.

[0046] {Configuration of the Light-Emitting Device} The configuration of the light-emitting device according to this embodiment is not particularly limited, as long as it uses the Ce-activated garnet phosphor of the present invention as the light-emitting element. For example, it may have a first light-emitting element (excitation light source) and, as a second light-emitting element, it may use a light-emitting element comprising, for example, one or more phosphors having an emission peak in the wavelength region of 480 nm to less than 650 nm and one or more other phosphors having an emission peak wavelength in the wavelength region of 600 nm to 700 nm. However, the configuration is not limited, and any known device configuration can be arbitrarily adopted.

[0047] As the first light-emitting element, an LED element can be used in which a light-emitting structure is formed from various semiconductors such as GaN-based semiconductors, ZnO-based semiconductors, and SiC-based semiconductors.

[0048] Examples of the apparatus configuration and embodiments of the light-emitting device include those described in Japanese Patent Application Publication No. 2007-291352.

[0049] In addition, the LED element may be fixed to a package such as a bullet-shaped package or an SMD package, or it may be directly fixed to a circuit board, as in the case of a chip-on-board light-emitting device. There are no limitations on the form of optical coupling between the LED element and the phosphor; the space between them may simply be filled with a transparent medium (including air), or optical elements such as lenses, optical fibers, light guide plates, or reflective mirrors may be interposed between them. A structure in which phosphor particles are dispersed in a translucent matrix is ​​typically formed by curing a resin paste in which particulate phosphor is dispersed. Various structures can be employed, including a structure in which the cured paste embeds the LED element, a structure in which the cured paste covers a part of the surface of the LED element in a film-like manner, and a structure in which a film made of the cured paste is placed at a location away from the LED element.

[0050] {Applications of Light-Emitting Devices} The applications of light-emitting devices are not particularly limited and can be used in various fields where ordinary light-emitting devices are used. Light-emitting devices with high color rendering are particularly suitable as light sources for lighting devices and image display devices. In addition, light-emitting devices equipped with a red phosphor with a good emission wavelength can be used in red vehicle indicator lights, or in vehicle indicator lights that emit white light including the red color.

[0051] [Lighting Device] In one embodiment, the present invention can be a lighting device equipped with the light-emitting device as a light source. When the light-emitting device is applied to a lighting device, there are no restrictions on the specific configuration of the lighting device, and the light-emitting device described above can be appropriately incorporated into a known lighting device. For example, a surface-emitting lighting device in which a large number of light-emitting devices are arranged on the bottom surface of a holding case can be given.

[0052] [Image Display Device] In one embodiment, the present invention can be an image display device equipped with the light-emitting device as a light source. When the light-emitting device is used as a light source for an image display device, there are no restrictions on the specific configuration of the image display device, but it is preferable to use it together with a color filter. For example, when the image display device is a color image display device using a color liquid crystal display element, the light-emitting device can be used as a backlight, and the image display device can be formed by combining a light shutter using liquid crystal and a color filter having red, green, and blue pixels.

[0053] The embodiments described above are for illustrative purposes only and do not limit the scope of the present invention. Various embodiments and modifications are possible without departing from the spirit of the present invention.

[0054] The phosphor, its manufacturing method, and light-emitting device of the present invention will be described in more detail below with reference to examples. However, the following examples represent only one embodiment of the present invention, and the present invention is not limited to these examples.

[0055] (Example 1) By the method for producing the phosphor shown in Figure 1, Ce ３＋ Ca containing ３ Al ２ Si ３ O １２ They manufactured it.

[0056] In the preparation step (S101), Ca ３ Al ２ Si ３ O １２ The raw materials for the matrix crystal were prepared to achieve the following elemental ratios. The activating material was CeO ２ This was added to the Ca site at a concentration of 0.2 mol% relative to the matrix crystal (in equation [α], A = Ca, D = Al, E = Si, and x = 0.002).

[0057] In the mixing step (S102), the raw materials prepared in the preparation step (S101) were mixed.

[0058] In the high-pressure synthesis step (S103), the raw materials mixed in the mixing step (S102) were sealed in a container and high-pressure synthesis was performed using a high-pressure generator. The conditions for the high-pressure synthesis reaction were 1400°C and 5 GPa. As a result, the phosphor Ce of Example 1 was synthesized. ３＋ Ca containing ３ Al ２ Si ３ O １２ A garnet phosphor (hereinafter abbreviated as "phosphor 1") was obtained.

[0059] X-ray diffraction measurements were performed on phosphor 1 manufactured in Example 1, followed by analysis of the XRD pattern (Rietveld analysis). The X-ray diffraction measurements were performed using an X-ray diffraction analyzer (product name: D8 ADVANCE Diffraction Meter, manufactured by Bruker AXS). Figure 2 shows the Rietveld analysis results for phosphor 1. In Figure 2, the horizontal axis represents the diffraction angle 2θ, the vertical axis represents the peak intensity, "+" indicates the plotted measured value, and the peak curve (solid line) represents the calculated result. Also, in Figure 2, R ｗｐ This is a weighted confidence factor, an index that evaluates the degree of agreement between the measured XRD pattern and the calculated XRD pattern; a lower value indicates a higher degree of agreement. From Figure 2, the peak position and peak intensity of the diffraction angle 2θ (°) of phosphor 1 obtained in Example 1 agree well with the calculated results, and R ｗｐ Since the value was sufficiently small, it was confirmed that phosphor 1 has a Ce-activated garnet structure.

[0060] The excitation and emission spectra of phosphor 1 obtained in Example 1 were measured. The measurements were performed using an emission analyzer (Xe lamp + spectrometer (SpectraPro-300i, Princeton Instruments) + photomultiplier tube (R3896, Hamamatsu Photonics)). The measurement results are shown in Figure 3. In Figure 3, the vertical axis is normalized intensity, and the horizontal axis is wavelength, λ. ｅｍ The curve on the left represents the emission wavelength. The curve on the right represents the excitation band, and the curve on the left represents the fluorescence band.

[0061] The excitation band of the phosphor 1 has a peak at 450 nm and was found to be excitable within the wavelength range of 410 nm to 490 nm, which corresponds to the near-ultraviolet region to the blue-green region. Also, the peak wavelength in the emission spectrum of the phosphor 1 was around 500 nm, and it had emission intensity over the wavelength range of 500 nm to 600 nm. The fluorescence color emitted from the phosphor 1 was green.

[0062] Next, the fluorescence lifetime of the phosphor 1 was measured. The measurement of the fluorescence lifetime of the phosphor 1 was carried out using a small fluorescence lifetime measurement device (Quantaurus-Tau, manufactured by Hamamatsu Photonics), excited by a 405 nm LED, detecting the emission at 500 nm, and using the time-correlated single photon counting method. Also, the temperature was controlled by holding the sample on a heating stage (10033L, manufactured by Linkam). The measurement temperature was room temperature (RT).

[0063] The measurement results are summarized and shown in Fig. 4. In Fig. 4, the vertical axis represents the fluorescence lifetime (Lifetime), and the horizontal axis represents the measurement temperature (Temperature). Also, λ ｅｍ represents the emission wavelength, λ ｅｘ represents the irradiation wavelength, "●" represents the measurement results of the phosphor 1, and "▼" represents the measurement results of Y ３＋ containing Ce ３ Al ５ O １２ .

[0064] From the obtained measurement results, the temperature dependence of the fluorescence lifetime of the phosphor 1 was compared with that of the phosphor of Comparative Example 1, Y ３＋ containing Ce ３ Al ５ O １２ (hereinafter, this will be abbreviated as "phosphor of Comparative Example”). The phosphor 2 of Comparative Example 1 is a YAG phosphor used in general white LEDs. As shown in Fig. 4, the phosphor 1 of Example 1 showed no decrease in fluorescence lifetime from the temperature dependence of the fluorescence lifetime from 80 K to 800 K, and it was revealed that it did not quench even at a high temperature of 800 K (527 °C). In contrast, the phosphor 2 of Comparative Example 1 started to quench at around 600 K.

[0065] As described above, the phosphor 1 of Example 1 exhibited green emission with an emission peak at 500 nm upon excitation with blue light. From the measurement of the emission excitation spectrum, it was found that the excitation band of the phosphor 1 had a peak at 450 nm and was excitable in the wavelength range from 410 nm to 490 nm. Also, from the temperature dependence of the fluorescence lifetime from 80 K to 800 K, it was revealed that the phosphor of Example 1 showed no decrease in the fluorescence lifetime and did not quench even at a high temperature of 800 K (527 °C).

[0066] In addition, the phosphor 1 of Example 1 synthesized under high pressure was stable in storage at normal temperature and pressure, experiments with high-intensity laser excitation, and heating experiments up to 800 K, and maintained the garnet crystal structure. Thus, the phosphor 1 of Example 1 has high structural stability and high emission temperature characteristics with respect to remarkable temperatures, and can be expected to be applied to high-intensity laser excitation lighting and the like at higher temperatures.

[0067] Also, it is considered that a similar effect can be obtained by using a host crystal having a composition in which part or all of the Ca in the host crystal Ca ３ Al ２ Si ３ O １２ is replaced with Mg or Sr. Therefore, Ce ３＋ -containing Ca ３－ｚ－ｙ Mg ｚ Sr ｙ Al ２ Si ３ O １２ (0 ≤ z ≤ 3, 0 ≤ y ≤ 3, z + y ≤ 3) has excellent emission characteristics while reducing the amount of rare earth used in the host crystal. Also, the rare earth-free host crystal has the merit of low geopolitical risk and low raw material cost.

[0068] As described above, the phosphor of this embodiment has excellent emission characteristics while reducing the amount of rare earth used in the host crystal. Specifically, as shown in the above-described examples, Ce ３＋ -containing Ca ３ Al ２ Si ３ O １２ shows green emission with an emission peak at 500 nm upon excitation with blue light. Also, Ce ３＋ -containing Ca３ Al ２ Si ３ O １２ The excitation band has a peak at 450 nm, and it can be excited in the wavelength range of 410 nm to 490 nm. Furthermore, from the temperature dependence of the fluorescence lifetime from 80 K to 800 K, Ce ３＋ Ca containing ３ Al ２ Si ３ O １２ It shows absolutely no decrease in fluorescence lifetime and does not quench even at high temperatures of 800K (527°C).

[0069] Also, Ce synthesized under high pressure ３＋ Ca containing ３ Al ２ Si ３ O １２ It is stable under normal temperature and pressure storage, high-intensity laser excitation experiments, and heating experiments up to 800K, and maintains its garnet crystal structure. Therefore, Ce ３＋ Ca containing ３ Al ２ Si ３ O １２ It possesses remarkably high structural stability and emission temperature characteristics, making it promising for applications such as high-intensity laser-pumped illumination at higher temperatures.

[0070] Rare earth-free matrix crystals have the advantage of lower geopolitical risks and lower raw material costs. ３ Al ２ Si ３ O １２ It is thought that a similar effect can be obtained by replacing some or all of the Ca with Mg or Sr. Therefore, Ce ３＋ Ca containing ３－ｚ－ｙ Mg ｚ Sr ｙ Al ２ Si ３ O １２ The (0 ≤ z ≤ 3, 0 ≤ y ≤ 3, z + y ≤ 3) configuration exhibits excellent luminescence properties while reducing the amount of rare earth elements used in the host crystal.

[0071] This application is based on Japanese Patent Application No. 2024-158028, filed on 12 September 2024. The entire specification, claims, and drawings of Japanese Patent Application No. 2024-158028 are incorporated herein by reference.

Claims

1. A phosphor containing a garnet crystalline phase having a composition represented by the following formula [α]. (In the above formula [α], A is at least one element selected from the group consisting of Ca, Mg, and Sr; D is at least one element selected from the group consisting of Al, Ga, and In; E is at least one element selected from the group consisting of Si and Ge; and x is a positive number that satisfies the formula: 0 < x ≤ 0.3.) 2. The phosphor according to claim 1, characterized in that the excitation wavelength peak is located in the range of 410 nm to 490 nm, and the emission wavelength peak is located in the range of 480 nm to 650 nm.

3. The fluorescence lifetime at 300K is τ ３００ , the fluorescence lifetime at 800K is τ ８００ When this is the case, τ ３００ The interval is between 40 ns and 100 ns, and 0.8 ≤ τ ８００ / τ ３００ The phosphor according to claim 1, characterized in that it satisfies ≤ 1.

2.

4. A method for producing a phosphor according to any one of claims 1 to 3, comprising: a preparation step (S101) of preparing raw materials that have been prepared to have an elemental ratio represented by the following formula [α]; a mixing step (S102) of mixing the raw materials to obtain a mixture; and a high-pressure synthesis step (S103) of synthesizing the mixture under high pressure to obtain a phosphor having a garnet crystal structure. (In the above formula [α], A is at least one element selected from the group consisting of Ca, Mg, and Sr; D is at least one element selected from the group consisting of Al, Ga, and In; E is at least one element selected from the group consisting of Si and Ge; and x is a positive number that satisfies the formula: 0 < x ≤ 0.3.) 5. The method for producing a phosphor according to claim 4, characterized in that the conditions for the high-pressure synthesis reaction in the high-pressure synthesis step (S103) are a temperature of 1200°C or more and 1600°C or less, and a pressure of 1 GPa or more and 20 GPa or less.

6. A light-emitting device comprising: a phosphor according to any one of claims 1 to 3; and an excitation light source for irradiating the phosphor with light to excite it.

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