Phosphor, method for producing the same, pigment including phosphor, pressure standard material including phosphor, and light-emitting device including phosphor

Abstract

To provide a phosphor that is stable even under conditions of high pressure and high temperature, a method for producing the same, a pigment including the phosphor, a pressure standard material including the phosphor, and a light-emitting device including the phosphor.SOLUTION: A phosphor according to the present invention contains a gallium oxide crystal having a corundum structure doped with chromium. Under conditions of 1 atm and 25°C, the phosphor is excited by light having the wavelength range of 250 nm or more and 650 nm or less, emitting light having a peak in the wavelength range of 695 nm or more and 700 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a phosphor using gallium oxide, a manufacturing method thereof, a pigment using the phosphor, a pressure standard material, and a light-emitting device. [Background technology]

[0002] A phosphor in which chromium is added to aluminum oxide (alumina, α-Al2O3) having a corundum structure is known (see, for example, Non-Patent Document 1). According to Non-Patent Document 1, alumina (Al2O3:Cr) having a corundum structure to which chromium is added is a phosphor that emits red light (R1 line, R2 line) when excited by visible light. Since the red emission wavelength shifts to the long wavelength side according to pressure, it is used as a pressure standard substance, and the method of determining pressure from the emission wavelength is called the ruby ​​fluorescence method. However, according to FIG. 15 of Non-Patent Document 1, as the pressure increases, the excitation wavelength shifts to the short wavelength side, which limits the excitation source of the excitation light and reduces the emission intensity. Therefore, a pressure standard substance to replace Al2O3:Cr is desired.

[0003] On the other hand, gallium oxide (Ga2O3) is known to have α (alpha), β (beta), γ (gamma), δ (delta), and ε (epsilon) crystal structures, and is known as a power device semiconductor.

[0004] So far, phosphors in which chromium is added to gallium oxide (Ga2O3) have been reported (see, for example, Non-Patent Document 2 and Patent Document 1). According to Non-Patent Document 2, a phosphor in which chromium is added to Ga2O3 having a monoclinic β-gallium structure emits red light (R1 line, R2 line) when excited by visible light at a low temperature of 85K, and therefore it has been reported that it can be used as a pressure standard material at low temperatures. However, since β-Ga2O3 is not a stable material under high pressure, it cannot measure pressures higher than 20 GPa. In addition, it has not been used as a pressure standard material at room temperature.

[0005] Patent Document 1 also discloses that Ga2O3:Cr phosphor can be obtained by mixing Ga2O3 and Cr2O3 with a flux and firing the mixture in an air atmosphere. According to Patent Document 1, Ga2O3:Cr phosphor is excited by light of 385 nm and has an emission peak at about 730 nm. However, according to Non-Patent Document 3, Ga2O3 described in Patent Document 1 also has a β-gallium structure, similar to Non-Patent Document 2. Therefore, a phosphor that is stable at room temperature and under high pressure, and is also stable under high pressure exceeding 20 GPa, is required. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-71389 A [Non-patent literature]

[0007] [Non-Patent Document 1] K.Syassen,High Pressure Research,Vol.28,No.2,June 2008,75-126 [Non-Patent Document 2] TP Beales et al., Solid State Communications, Vol. 73, No. 1, pp. 1-3, 1990 [Non-Patent Document 3] C.G. Walsh et al., Journal of Luminescence, Vol. 40 & 41, 103-104, 1988 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above, an object of the present invention is to provide a phosphor that is stable even under high pressure and high temperature, a method for producing the same, and an ink, a pressure standard material, and a light-emitting device that use the same. [Means for solving the problem]

[0009] The phosphor of the present invention contains a gallium oxide crystal having a corundum structure added with chromium, thereby solving the above problems. At 1 atmosphere and 25 ° C, it may be excited by light having a wavelength in the range of 250 nm or more and 650 nm or less, and emit light having a peak at a wavelength in the range of 695 nm or more and 700 nm or less. At 1 atmosphere and 25 ° C, it may be excited by light having a wavelength in the range of 250 nm or more and 650 nm or less, and emit light (R1 line) having a peak at a wavelength in the range of 697 nm or more and 700 nm or less, and light having a peak at a wavelength in the range of 695 nm or more and less than 697 nm (R2 line). P = (λ - λ0) / (0.315 ± 0.005) (where P is the pressure (GPa), λ0 is the peak wavelength (nm) of the R1 line at 25 ° C and 1 atmosphere, and λ is the peak wavelength (nm) of the R1 line at 25 ° C and pressure P) may be satisfied. The gallium oxide crystal is (Ga 1-x Cr x )2O 3-α (where Ga is gallium, Cr is chromium, O is oxygen, x is 0 <x ≦ 0.1, and α is -0.2 ≦ α ≦ 0.2) may be represented. The x may satisfy 0.001 ≦ x ≦ 0.05. The gallium oxide crystal may be single crystal particles. The average particle size of the single crystal particles may be in the range of 1 μm or more and 120 μm or less. The method for producing the phosphor of the present invention includes treating a raw material powder containing gallium oxide powder and chromium oxide powder in a temperature range of 700 ° C or more and 2300 ° C or less and a pressure range of 2 GPa or more and 30 GPa or less, thereby solving the above problems. In the raw material powder, the chromium oxide powder may be contained in a range of more than 0 mol% and 10 mol% or less with respect to the gallium oxide powder. The temperature range may be in the range of 1000 ° C or more and 1500 ° C or less. The pressure range may be in the range of 2 GPa or more and 10 GPa or less. The pigment of the present invention contains at least the above phosphor, thereby solving the above problems. The pressure standard material of the present invention contains at least the above phosphor, thereby solving the above problems. The light emitting device of the present invention comprises an excitation source that emits light having a wavelength in the range of 300 nm or more and 650 nm or less, and at least the above phosphor, thereby solving the above problems. Effect of the Invention

[0010] The phosphor of the present invention contains gallium oxide crystals having a corundum structure to which chromium is added. The phosphor of the present invention is excited by irradiation with visible light at room temperature and atmospheric pressure, and emits red light having a peak in the range of 650 nm to 700 nm. The phosphor of the present invention is stable even under high temperature and high pressure because it is based on gallium oxide having a corundum structure. The phosphor of the present invention can be produced by a high temperature and high pressure process.

[0011] By using the phosphor of the present invention, a white or non-white light emitting device can be provided. In addition, the phosphor of the present invention has a green object color and can be used as a pigment. In addition, the phosphor of the present invention can be used as a pressure standard material because the emission wavelength changes according to the change in pressure. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of a high-pressure cell equipped with a capsule used in the production of a phosphor of the present invention. [Diagram 2] FIG. 1 is a schematic diagram showing a belt-type high-pressure device used in the production of a phosphor according to the present invention. [Diagram 3] FIG. 1 shows how pressure is measured using the pressure standard material of the present invention. [Figure 4] Schematic diagram showing a light-emitting device of the present invention. [Diagram 5] A diagram showing the appearance of the sample in Example 1 [Figure 6] FIG. 1 shows an optical microscope photograph of a sample of Example 1. [Figure 7]A diagram showing the sample in Example 1 emitting light. [Figure 8] FIG. 1 shows the XRD pattern of the sample of Example 1. [Figure 9] XRD pattern of the sample from Example 1 showing the temperature durability of the corundum structure [Figure 10] FIG. 1 shows the emission spectrum of the sample in Example 1. [Figure 11] FIG. 1 shows a detailed emission spectrum of the sample in Example 1. [Figure 12] Figure showing the excitation spectrum of the sample in Example 1 [Figure 13] Figure showing the pressure dependence of the R1 line of the sample in Example 1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are given like reference numerals and their description will be omitted.

[0014] The present inventors discovered that by adding chromium to a gallium oxide crystal having a corundum structure, which is a stable phase at high pressure, through high temperature and pressure treatment, the crystal is metastable even at room temperature and pressure, and thus arrived at the present invention.

[0015] The phosphor of the present invention contains gallium oxide crystals having a corundum structure to which chromium has been added, which results in a phosphor that emits fluorescence when irradiated with an excitation source.

[0016] In the phosphor of the present invention, gallium oxide has a corundum structure. Gallium oxide having a corundum structure is also called α-type or α-Ga2O3, and belongs to a rhombohedral symmetric crystal structure and belongs to the R-3c space group (167th in the International Talbes for Crystallography). In this specification, "-3" represents an overbar of 3. Whether or not a synthesized sample is the phosphor of the present invention can be determined by, for example, whether or not the main peaks (e.g., 8 peaks) in the X-ray diffraction pattern of the sample match the diffraction pattern of ICDD#27431 powder diffraction and crystal structure data.

[0017] The phosphor of the present invention has a green object color. That is, when the phosphor of the present invention is irradiated with sunlight or illumination such as a fluorescent lamp, a green object color is observed, and since the color is good and does not deteriorate over a long period of time, the phosphor of the present invention is suitable for use as a pigment. When such a pigment is used in paints, inks, paints, glazes, colorants, and the like, good color development can be maintained for a long period of time.

[0018] The phosphor of the present invention is irradiated with an excitation source to produce Cr 3+ Specifically, when excited by light having a wavelength in the range of 250 nm to 650 nm at 1 atmospheric pressure and 25° C., the phosphor of the present invention emits red light having a peak in a wavelength range of 695 nm to 700 nm. More preferably, the phosphor of the present invention is efficiently excited by ultraviolet or visible light of 380 nm to 500 nm, or visible light of 500 nm to 630 nm, and emits red light having a peak in a wavelength range of 695 nm to 700 nm.

[0019] More specifically, the phosphor of the present invention is excited by light having a wavelength in the range of 250 nm to 650 nm at 1 atmospheric pressure and 25° C., and emits light (R1 line) having a peak in the wavelength range of 697 nm to 700 nm and light (R2 line) having a peak in the wavelength range of 695 nm to less than 697 nm. At this time, the emission intensity of the R1 line is higher than that of the R2 line.

[0020] The inventors of the present invention have focused on the R1 line of the phosphor of the present invention and found that the peak position of the R1 line shifts to the longer wavelength side with an increase in pressure of the order of GPa. In detail, the phosphor of the present invention satisfies the following formula. P = (λ-λ0) / (0.315±0.005) Here, P is pressure (GPa), λ0 is the peak wavelength (nm) of the R1 line at 25° C. and 1 atmosphere, and λ is the peak wavelength (nm) of the R1 line at 25° C. and pressure P.

[0021] In addition, since the phosphor of the present invention is based on gallium oxide having a corundum structure stable in the high-pressure phase, as described in H. Yusa et al., Physical Review B, 2008, Vol. 77, Issue 6, it is stable up to a high pressure of 30 GPa. Furthermore, as shown in the examples described later, the phosphor of the present invention is stable up to a high temperature of 500 °C. Therefore, the phosphor of the present invention can be used as a pressure standard material. In particular, since the phosphor of the present invention is excited in a wide range from the ultraviolet region (250 nm) to the visible region of 650 nm, unlike Non-Patent Document 1, even if the excitation spectrum shifts to the shorter wavelength side with an increase in pressure, for example, any laser light in the range of 480 nm to 630 nm can be used as a light source, and it can be efficiently excited without a decrease in emission intensity. For this reason, if the phosphor of the present invention is used as a pressure standard material, pressure can be measured accurately.

[0022] The phosphor of the present invention only needs to contain a gallium oxide crystal having a corundum structure to which chromium is added. Such a gallium oxide crystal is preferably (Ga 1-x Cr x )2O 3-α (where Ga is gallium, Cr is chromium, O is oxygen, x satisfies 0 < x ≦ 0.1, and α satisfies -0.2 ≦ α ≦ 0.2).

[0023] x is the addition amount of chromium which is the emission center. If it is within the above range, the crystal structure becomes stable, so that it functions as a phosphor. x preferably satisfies 0.001 ≦ x ≦ 0.05. If it is within this range, the crystal structure becomes stable, concentration quenching is suppressed, and the emission intensity is excellent.

[0024] α is the oxygen content derived from oxygen deficiency or oxygen excess. From the viewpoint of emission intensity, it is better if there is no oxygen deficiency or oxygen excess. However, oxygen deficiency and oxygen excess in production are allowed. If it is within the above range, the crystal structure is efficiently maintained and it functions as a phosphor. α is preferably -0.1 ≦ α ≦ 0.1, more preferably -0.05 ≦ α ≦ 0.05, and still more preferably α = 0.

[0025] In the phosphor of the present invention, the gallium oxide crystal is preferably a single crystal particle or an aggregate of single crystal particles. This allows for high-brightness emission. Although it depends on the application, for example, when the phosphor is used as the above-mentioned pressure standard material, a single single crystal particle can be used. In this case, the average particle size of the single crystal particles is preferably in the range of 1 μm to 120 μm. Within this range, handling of a single single crystal particle is excellent. For high-brightness emission, it is also possible to crush the single crystal particles and use them in the range of 1 μm to 50 μm.

[0026] When the phosphor of the present invention is used as a pigment or a light-emitting device, it may be further pulverized to have an average particle size of, for example, 0.1 μm to 20 μm, which provides excellent applicability and operability when mounting the phosphor on various light-emitting devices.

[0027] In this specification, the average particle size is the average value of the particle sizes of 100 randomly selected particles measured in an image observed by an optical microscope using image analysis software. In this specification, Image J (ver. 1.54d; open source, public domain image processing software) was used as the image analysis software.

[0028] Next, a method for producing the phosphor of the present invention will be described. The phosphor of the present invention is produced by high-temperature and high-pressure treatment. Specifically, this involves treating a raw material powder containing a gallium oxide powder and a chromium oxide powder at a temperature of 700° C. to 2300° C. and a pressure of 2 GPa to 30 GPa.

[0029] The gallium oxide powder may be β-gallium oxide, which is easily available. The chromium oxide powder contains Cr as a luminescent center. 3+ Since the oxide is introduced, chromium (III) oxide is preferred, but chromium (I) oxide, chromium (II) oxide, chromium (IV) oxide, chromium (V) oxide, or a mixture thereof may be used.

[0030] The particle size of the gallium oxide powder and the chromium oxide powder is preferably 0.1 μm or more and 1 μm or less, in which case the gallium oxide powder and the chromium oxide powder are mixed uniformly.

[0031] In the raw material powder, the chromium oxide powder may be contained in a range of more than 0 mol % to 10 mol % or less with respect to the gallium oxide powder, and more preferably, the chromium oxide powder may be contained in a range of more than 0 mol % to 5 mol % or less with respect to the gallium oxide powder.

[0032] The time for the high-temperature, high-pressure treatment varies depending on the amount of raw material and the apparatus used, but may be, for example, from 5 minutes to 24 hours.

[0033] The above-mentioned treatment steps may be carried out by high-temperature and high-pressure treatment using an apparatus selected from the group consisting of a diamond anvil apparatus, a multi-anvil apparatus and a belt-type high-pressure apparatus, or by shock compression. These methods can achieve the above-mentioned temperature and pressure ranges. As long as the apparatus can achieve the above-mentioned high temperature and high pressure conditions, it is not necessary to be limited to the above-mentioned apparatus.

[0034] Here, a high-pressure cell equipped with a capsule filled with raw material powder is used, and high-temperature, high-pressure processing is performed using a belt-type high-pressure device.

[0035] FIG. 1 is a schematic cross-sectional view of a high-pressure cell equipped with a capsule used in producing a phosphor of the present invention.

[0036] The high-pressure cell comprises cylindrical pyrophyllite 1, two steel rings 2 arranged inside the pyrophyllite 1 so as to contact the upper and lower sides of the inner wall surface of the cylinder, a cylindrical carbon heater 4 arranged on the central axis side of the steel ring 2, a metal capsule 6 arranged inside the carbon heater 4, and raw material powder filled inside the metal capsule 6. The gap between the pyrophyllite 1 and the carbon heater 4 is filled with filling powder 3, and the gap between the carbon heater 4 and the metal capsule 6 is also filled with filling powders 3 and 5.

[0037] FIG. 2 is a schematic diagram showing a belt-type high-pressure device used in the production of the phosphor of the present invention.

[0038] The high-pressure cell described with reference to Fig. 1 is disposed between the cylinders 27A and 27B of the belt-type high-pressure device 21 and between the anvils 25A and 25B by contacting the conductors 26A and 26B made of thin metal plates at predetermined positions. Next, pyrophyllite 28 is filled between these members and the high-pressure cell.

[0039] The anvils 25A, 25B and the cylinders 27A, 27B are moved to the high-pressure cell side, and the high-pressure cell is pressurized to satisfy the above-mentioned conditions. In the pressurized state, the cell is heated to satisfy the above-mentioned conditions, and is maintained for a predetermined time. For example, when the belt-type high-pressure device 21 is used, a phosphor containing gallium oxide crystals having the above-mentioned chromium-added corundum structure can be produced by treating the cell at a temperature range of 1000°C to 1500°C and a pressure range of 2 GPa to 10 GPa.

[0040] Next, applications of the phosphor of the present invention will be described. FIG. 3 is a diagram showing a state in which pressure is measured using the pressure standard material of the present invention.

[0041] Figure 3 shows how the pressure standard material of the present invention is applied to a high-pressure generating apparatus using a diamond anvil cell (DAC) to measure pressure. In Figure 3, a gasket with a hole is sandwiched between a pair of diamond anvils with flattened tips, and the sample to which pressure is to be applied, the phosphor of the present invention as a pressure standard material, and a pressure transmission medium are enclosed in the hole.

[0042] The pressure is measured as follows: pressure is applied by the DAC, and light with a wavelength in the range of 250 nm to 650 nm (blue light in FIG. 3) is irradiated onto the phosphor of the present invention through the hole. The fluorescence from the phosphor is measured with a fluorescence spectrophotometer to determine the wavelength λ of the R1 line, and the pressure P can be calculated by substituting this into the following equation. P = (λ-λ0) / (0.315±0.005) Here, P is pressure (GPa), λ0 is the peak wavelength (nm) of the R1 line at 25° C. and 1 atmosphere, and λ is the peak wavelength (nm) of the R1 line at 25° C. and pressure P. According to the pressure standard material of the present invention, the above formula holds at room temperature (25° C.), and therefore pressure can be measured in a room temperature environment, unlike Non-Patent Document 2.

[0043] FIG. 4 is a schematic diagram showing a light emitting device of the present invention.

[0044] The light emitting device of the present invention comprises at least an excitation source that emits light having a wavelength in the range of 300 nm to 650 nm, and the phosphor of the present invention. In Fig. 4, an example of a bullet-type white light emitting diode is shown as the light emitting device 400. There are two lead wires 410 and 420, and one of the lead wires 410 has a recess formed therein, on which a blue light emitting diode element 430 having an emission peak at 485 nm is mounted.

[0045] The lower electrode of the blue light emitting diode element 430 and the bottom surface of the recess are electrically connected by a conductive paste, and the upper electrode and another lead wire 420 are electrically connected by a gold thin wire 450. The phosphor 440 of the present invention and a yellow phosphor represented by YAG:Ce are dispersed in a resin and mounted near the blue light emitting diode element 430. The resin in which the phosphor is dispersed is transparent and covers the entire blue light emitting diode element 430. The tip of the lead wire including the recess, the blue light emitting diode element, and the resin in which the phosphor is dispersed are sealed with a transparent resin 460. The resin 460 is generally cylindrical, and its tip is curved in a lens shape, and is called a bullet type. It goes without saying that a known phosphor other than YAG:Ce can be used as the yellow phosphor.

[0046] The light emitting device 400 of the present invention can emit white light by mixing, for example, blue light emitted by the excitation source, red light emitted by the phosphor of the present invention, and yellow light emitted by the yellow phosphor, but if, for example, ultraviolet light is used as the excitation source instead of blue light, a light emitting device that emits red light can be provided. In this way, by appropriately using an excitation source, a light emitting device that emits light other than white light can be provided.

[0047] As described above, the phosphor of the present invention has a green object color and can be used as a pigment. In particular, it is excited by irradiation with light having a wavelength of 250 nm or more and 650 nm or less and emits red light, so that using it as green ink for bills, certificates, receipts, gift certificates, etc. is useful for preventing counterfeiting.

[0048] The present invention will now be described in detail with reference to specific examples, but it should be noted that the present invention is not limited to these examples. EXAMPLES

[0049] [Example 1] In Example 1, the production apparatus shown in FIG. 1 and FIG. 2 was used to produce (Ga 1-x Cr x )2O 3+α A phosphor (x=0.01) was prepared.

[0050] A raw powder containing β-type gallium oxide (β-Ga2O3) powder (manufactured by Kojundo Chemical Laboratory, purity 99.999%, particle size 0.5μm) and chromium (III) oxide (Cr2O3) powder (manufactured by Sigma-Aldrich, purity 99.9%, particle size 0.2μm) was subjected to high temperature and high pressure treatment. In detail, the raw powder (200mg) was prepared by weighing and mixing 1mol% chromium oxide powder with respect to the gallium oxide powder to obtain the designed composition shown in Table 1.

[0051] The raw powder was filled into a cylindrical metal capsule 8 (Fig. 1) made of Au (gold) with one end closed by a disk-shaped lid, and the other end was sealed with a disk-shaped Au lid. Next, the filling powder (NaCl+20wt%ZrO2) was spread on the inner bottom of a cylindrical carbon heater 4 (Fig. 1) with one end closed by a disk-shaped lid, and the metal capsule was placed coaxially inside the cylindrical carbon heater, and the filling powder (NaCl+20wt%ZrO2) was spread on top of it again, and the metal capsule was placed coaxially. Next, the gap between the metal capsule and the inner wall surface of the carbon heater was filled with the filling powder (NaCl+10wt%ZrO2), and the filling powder (NaCl+20wt%ZrO2) was further spread on the top of the metal capsule, and the other end was sealed with a disk-shaped lid.

[0052] Next, this cylindrical carbon heater was placed coaxially inside the cylindrical pyrophyllite, and the gap between the carbon heater and the inner wall surface of the pyrophyllite was filled with a filling powder (NaCl+10 wt% ZrO2).

[0053] Next, a steel ring was pressed into the packing powder on the upper side of the inner wall surface of the pyrophyllite, and another steel ring was pressed into the packing powder on the lower side of the inner wall surface of the pyrophyllite, thus preparing a high-pressure cell.

[0054] The high-pressure cell was placed at a predetermined position in the belt-type high-pressure device shown in Figure 2. The high-pressure cell was pressurized to the pressure value shown in Table 1. Next, while still pressurized, the sample was heated at the temperature and for the holding time shown in Table 1 for high-temperature, high-pressure treatment.

[0055] The temperature was returned to room temperature and normal pressure (25°C, 1 atm), and the product inside the metallic capsule was removed. In this way, a sample of Example 1 was obtained. The appearance of the sample of Example 1 was observed, and the state when irradiated with a halogen lamp and ultraviolet light (wavelengths 280 nm, 365 nm), etc., was observed. These results are shown in Figures 5 to 7.

[0056] The sample of Example 1 was identified by X-ray diffraction at a synchrotron radiation facility (Aichi Synchrotron Radiation Facility). The results are shown in Figures 8 and 9. X-ray: Synchrotron radiation X-ray (wavelength 0.7233Å) Scanning range 2θ(°): 5~40° Exposure time: 60 seconds

[0057] Next, the emission spectrum and excitation spectrum of the sample of Example 1 were measured at 1 atmospheric pressure and 25° C. using a fluorescence spectrophotometer (JASCO Corporation, FP8500). The excitation emission spectrum is shown in FIGS.

[0058] Next, the fluorescence spectrum was measured when a pressure of up to 10 GPa was applied to the sample of Example 1 using the diamond anvil cell apparatus shown in Figure 3. The results are shown in Figure 13.

[0059] [Example 2 to Example 4] In Examples 2 to 4, the production apparatus shown in FIG. 1 and FIG. 2 was used, and the (Ga 1-x Cr x )2O 3+α Phosphors (x=0.001, 0.0005, 0.05) were produced. For the obtained samples of Examples 2 to 4, the powder X-ray diffraction, the excitation emission spectrum, and the pressure dependence of the emission spectrum were examined in the same manner as in Example 1. The results are shown in Table 2.

[0060] [Table 1]

[0061] The results of the samples of Examples 1 to 4 will be explained together. FIG. 5 is a diagram showing the appearance of the sample of Example 1.

[0062] Fig. 5(a) shows the appearance under indoor fluorescent lighting, and Fig. 5(b) shows the appearance when irradiated with ultraviolet light (wavelength 280 nm). Fig. 5 shows the grayscale, but according to Fig. 5(a), the sample of Example 1 exhibited green light under indoor fluorescent lighting, and according to Fig. 5(b), it exhibited red light when irradiated with ultraviolet light. Although not shown, the samples of Examples 2 to 4 also exhibited similar light emission.

[0063] FIG. 6 shows an optical microscope photograph of the sample of Example 1.

[0064] Fig. 6 shows the state of the sintered body shown in Fig. 5 after pulverization. According to Fig. 6, all of the particles are single crystal particles, the particle size is about 50 μm to 100 μm, and the average particle size is 75 μm. Although not shown, the samples of Examples 2 to 4 are also aggregates of single crystal particles of about 50 μm to 100 μm, and according to Image J, the average particle size is 75 μm. Those skilled in the art will understand that the particle size can be adjusted by pulverizing the single crystal particles depending on the application.

[0065] FIG. 7 is a diagram showing the state in which the sample of Example 1 emits light.

[0066] Fig. 7(a) shows the light emission when the sample (single crystal particles) of Example 1 was irradiated with a halogen lamp, and Fig. 7(b) shows the light emission when the sample (single crystal particles) of Example 1 was irradiated with ultraviolet light (wavelength 365 nm). Although shown in gray scale in Fig. 7, the sample (single crystal particles) of Example 1 exhibited a green to yellow color when irradiated with a halogen lamp according to Fig. 7(a), and exhibited a red color when irradiated with ultraviolet light according to Fig. 7(b), which was the same result as Fig. 5. Although not shown, the samples of Examples 2 to 4 also exhibited similar light emission.

[0067] FIG. 8 shows the XRD pattern of the sample of Example 1. Figure 9 is a diagram showing the temperature durability of the random structure according to the XRD pattern of the sample of Example 1.

[0068] Figure 8 shows the XRD pattern of Example 1 at 1 atm and 25 °C, and all peaks matched the diffraction peaks of gallium oxide of the random structure (ICDD #27431). As shown in Table 2, the samples of Examples 2 to 4 also showed a similar XRD pattern, confirming that they have a random structure.

[0069] According to Figure 9, it was found that the random structure was maintained from 25 °C to 400 °C, but the random structure could not be maintained above 600 °C, and it was found that a stable β-gallia structure was obtained at 800 °C. From this, it was found that the phosphor of the present invention is stable up to a temperature of about 500 °C.

[0070] From the above Figures 5 to 9, it was shown that a phosphor containing a gallium oxide crystal having a random structure added with chromium can be obtained by the high-temperature and high-pressure treatment of the present invention. In particular, the phosphor of the present invention contains a gallium oxide crystal represented by (Ga 1-x Cr x )2O 3+α (where x is 0 < x ≦ 0.1 and α is 0 ≦ α ≦ 0.2), and it was shown that it emits red light when irradiated with ultraviolet to visible light.

[0071] Figure 10 is a diagram showing the emission spectrum of the sample of Example 1. Figure 11 is a diagram showing the details of the emission spectrum of the sample of Example 1. Figure 12 is a diagram showing the excitation spectrum of the sample of Example 1.

[0072] 10 and 11 are diagrams showing the emission spectra when the sample of Example 1 is irradiated with a 429 nm light source and a blue laser (wavelength 488 nm) at 1 atmosphere and 25° C., respectively. According to FIG. 10, it was found that the sample of Example 1 is excited by the 429 nm light source at 1 atmosphere and 25° C. and emits light having a peak in the wavelength range of 695 nm to 700 nm. More specifically, according to FIG. 11, the light having a peak in the wavelength range of 695 nm to 700 nm includes Cr lines of 697.57 nm (R1 line) and 695.94 nm (R2 line). 3+ As shown in Table 2, the samples of Examples 2 to 4 were excited by a blue laser in the same way as Example 1, and emitted Cr 3+ The fluorescence lines R1 and R2 derived from

[0073] [Table 2]

[0074] FIG. 12 shows a spectrum of the emission intensity measured when the emission wavelength is fixed at 697.5 nm at 25° C. and 1 atm and the wavelength of the excitation light is scanned. FIG. 12 also shows the excitation spectrum (dashed line) of the R1 line (694.5 nm) of Al2O3:Cr. According to FIG. 12, it was shown that the sample of Example 1 is efficiently excited at a wavelength of 250 nm or more and 650 nm or less, and emits light having a peak in the wavelength range of 695 nm or more and 700 nm or less. Surprisingly, the excitation wavelength of the sample of Example 1 was shifted to the long wavelength side compared to the excitation wavelength of Al2O3:Cr. This suggests that, as shown in FIG. 15 of Non-Patent Document 1, the excitation spectrum of the sample of Example 1 shifts to the short wavelength side with increasing pressure, and even if it cannot be excited by ultraviolet light or blue light, green light or red light can be used as an excitation source.

[0075] As shown in Figures 10 to 12 and Table 2 above, when the phosphor of the present invention is excited with light having a wavelength in the range of 250 nm or more and 650 nm or less at 1 atmosphere and 25°C, it emits light having a peak in a wavelength range of 695 nm or more and 700 nm or less, and more specifically, emits light having a peak in a wavelength range of 697 nm or more and 699 nm or less (R1 line) and light having a peak in a wavelength range of 695 nm or more and less than 697 nm (R2 line).

[0076] FIG. 13 is a graph showing the pressure dependence of the R1 line of the sample of Example 1.

[0077] As shown in Figure 3, in the diamond anvil apparatus, two diamonds, each polished to a flat bottom, are placed with their bottoms facing each other, and pressure is applied to the sample when the sample is held on the bottom via a gasket. At 25°C, the sample was irradiated with ultraviolet light with a wavelength of 365 nm as an excitation source, and pressure was applied up to 10 GPa. The fluorescence R1 line from the sample was measured with a high-resolution spectrophotometer.

[0078] 13, the R1 line of the sample of Example 1 shifted to the longer wavelength side from 697.6 nm (1 atm) to 701.0 nm (11 GPa) with increasing pressure. At this time, it was found that the following equation was satisfied: P = (λ-λ0) / (0.315±0.005) Here, P is pressure (GPa), λ0 is the peak wavelength 697.57 (nm) of the R1 line at 25° C. and 1 atmosphere, and λ is the peak wavelength (nm) of the R1 line at 25° C. and pressure P.

[0079] This shows that the sample in Example 1 can determine the pressure P if the wavelength of the R1 line is known, and can function as a pressure standard sample for pressure measurement. As shown in Figure 12, the excitation wavelength of the sample in Example 1 is shifted to the longer wavelength side compared to that of the conventional Al2O3:Cr phosphor, so not only can long excitation wavelengths such as green and red be used even under high pressure, but the emission intensity is also excellent, making it possible to measure pressure with high accuracy. [Industrial Applicability]

[0080] The phosphor of the present invention is efficiently excited by ultraviolet to visible light and emits red light. In particular, the phosphor of the present invention is stable even under high pressures exceeding 20 GPa, is thermally stable, and the emission wavelength shifts with increasing pressure, so it can be used as a pressure standard material. It can also be used as a pigment, an ultraviolet sensor, or a light-emitting device such as an LED. [Explanation of symbols]

[0081] 1, 28 Pyrophyllite 2 Steel Rings 3 Filling powder 4 Carbon heater 6 Metal Capsule 21 Belt-type high-pressure device 25A, 25B Anvil 26A, 26B Conductor 27A, 27B Cylinders 400 Light Emitting Device 410, 420 Lead Wire 430 Blue light emitting diode element 440 Phosphor 450 Gold thin wire 460 Resin

Claims

1. A phosphor containing gallium oxide crystals having a corundum structure with added chromium.

2. The phosphor according to claim 1, which, when excited by light having a wavelength in the range of 250 nm to 650 nm at 1 atmosphere and 25°C, emits light having a peak in the wavelength range of 695 nm to 700 nm.

3. The phosphor according to claim 2, which, when excited by light having a wavelength in the range of 250 nm to 650 nm at 1 atmosphere and 25°C, emits light having a peak in the wavelength range of 697 nm to 700 nm (R1 line) and light having a peak in the wavelength range of 695 nm to less than 697 nm (R2 line).

4. P = (λ - λ) ０ ) / (0.315 ± 0.005) (where P is the pressure (GPa) and λ ０ The phosphor according to claim 1, wherein λ is the peak wavelength (nm) of the R1 line at 25°C and 1 atm, and λ is the peak wavelength (nm) of the R1 line at 25°C and pressure P.

5. The gallium oxide crystal is (Ga １－ｘ Cr ｘ ) ２ O ３－α The phosphor according to claim 1, represented as follows: (where Ga is gallium, Cr is chromium, O is oxygen, x is 0 < x ≤ 0.1, and α is -0.2 ≤ α ≤ 0.2).

6. The phosphor according to claim 5, wherein x satisfies 0.001 ≤ x ≤ 0.

05.

7. The phosphor according to claim 1, wherein the gallium oxide crystal is a single crystal particle.

8. The phosphor according to claim 7, wherein the average particle size of the single crystal particles is in the range of 1 μm or more and 120 μm or less.

9. A method for producing a phosphor according to any one of claims 1 to 8, comprising treating a raw material powder containing gallium oxide powder and chromium oxide powder at a temperature range of 700°C to 2300°C and a pressure range of 2 GPa to 30 GPa.

10. The manufacturing method according to claim 9, wherein the raw material powder contains the chromium oxide powder in an amount greater than 0 mol% and less than or equal to 10 mol% relative to the gallium oxide powder.

11. The manufacturing method according to claim 9, wherein the temperature range is in the range of 1000°C or more and 1500°C or less.

12. The manufacturing method according to claim 9, wherein the pressure range is in the range of 2 GPa or more and 10 GPa or less.

13. A pigment containing at least the phosphor described in claim 1.

14. A pressure standard material containing at least the phosphor described in claim 1.

15. An excitation source that emits light having a wavelength in the range of 300 nm to 650 nm, At least the phosphor described in claim 1 and A light-emitting device, including a light-emitting device.

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