JP2006335914A - Powdery phosphor, method for producing the same and luminescent device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ZnMgO-based powdery phosphor in which high-concentration Mg forms a solid solution and to provide a luminescent device by using the phosphor. <P>SOLUTION: The present invention provides the powdery phosphor characterized in that a surface layer, in which at least all or a part of the surface is represented by chemical formula Zn<SB>(1-x)</SB>R<SB>x</SB>O (R is an element of the group IIA; 0.05≤x), having a hexagonal structure is formed on the surface of a minute substrate. In the powdery phosphor, R in the chemical formula is preferably Mg. The present invention further provides a method for producing the powdery phosphor and the luminescent device using the phosphor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phosphor that emits visible light to ultraviolet light with high efficiency by low-energy electron beam irradiation, a method for producing the same, and a light-emitting device using the phosphor.

  Due to recent environmental problems, the use of devices and devices that use mercury as a light emitter is being regulated. Typical devices that use mercury are lighting or light source devices such as fluorescent lamps, low-pressure, medium-pressure, high-pressure, and ultra-high-pressure mercury lamps. All of these operate on the principle of emitting visible light or ultraviolet light by irradiating phosphors with ultraviolet light generated by mercury discharge.

The high-pressure mercury lamp is an ultraviolet lamp that mainly emits light having a wavelength of 365 nm, and is used for curing a resin in an electronic component. The low-pressure mercury lamp is used as an essential lamp in a sterilization apparatus in order to efficiently generate 254 nm ultraviolet rays that can directly destroy the DNA of living organisms.
Therefore, there is a strong demand for a light-emitting device that can efficiently emit ultraviolet light having these wavelengths, particularly 300 nm or less, without using mercury.

  On the other hand, there is a fluorescent display tube as an environmentally friendly light emitting device that does not use mercury. It emits visible light by irradiating a phosphor with a low-speed electron beam generated from a hot cathode or cold cathode, and has features such as long life, high reliability, and low power consumption. It is used as a display or outdoor display device (see Patent Document 1).

  The most standard fluorescent display tube has a phosphor attached to the anode (plate) of a directly heated triode (patterning), and the thermoelectrons emitted from the filament are controlled by a grid. When the thermoelectrons hit the anode, the phosphor is fluorescent. The body emits light. The filament material is basically a tungsten alloy, but various other alloys can also be used.

  Recently, LCD (Liquid Crystal Display) and organic EL (Electro Luminance) displays are also available, but they still have a wide viewing angle, beautiful light emission, long life, operating temperature range, etc. In general, fluorescent display tubes have a long day, and they are used mainly in audio and video equipment, especially because they have a bright light emission and a clear display. It is also often used for car clocks because of its high visibility and reliability. Organic EL displays also have the disadvantages of having a short lifetime despite their advantages of wide viewing angle and high luminous efficiency due to self-emission. In this respect, the life of the fluorescent display tube is a long life exceeding 30,000 hours. Furthermore, since the problem that the hot filament is broken can be solved by making the cathode into a cold cathode type, the lifetime is further increased and the reliability is increased. This is commonly referred to as a field emission display (FED).

A fluorescent lamp uses the above-described fluorescent display tube as a light source, not as a display. Cold cathode fluorescent lamps are promising as low power consumption and long-life lamps.
However, the conventional fluorescent display tube is intended only for display device use and is not intended to generate ultraviolet rays. Therefore, in a fluorescent display tube, a method has been proposed in which the surface of a phosphor powder that emits visible light when irradiated with an electron beam is coated with a phosphor that emits ultraviolet light when irradiated with an electron beam. This is based on the principle that ultraviolet light is emitted once by irradiating an electron beam onto an ultraviolet light-emitting phosphor, and visible light having a desired wavelength is generated by irradiating the ultraviolet light with this electron beam. ZnO, ZnO.Ga ₂ O ₃ : Cd, etc. have been reported as ultraviolet light emitting phosphors. ZnO.Ga ₂ O ₃ : Cd emits light with an emission peak wavelength of 365 nm (see Patent Documents 2, 3, and 4).

However, the present invention is for obtaining a fluorescent display tube that emits visible light, and is not a device that emits ultraviolet light. That is, there has never been a phosphor that can efficiently generate ultraviolet rays when irradiated with an electron beam. The reason is estimated as follows.
In the fluorescent display tube of the invention, the visible light emitting phosphor absorbs the ultraviolet light emitted by the ultraviolet light emitting phosphor and emits visible light, and at the same time, it absorbs an electron beam to a certain extent and emits visible light. Therefore, the intensity of ultraviolet rays does not have to be so high. However, when only the ultraviolet light-emitting phosphor is used, the light emission efficiency is too low to be put into practical use as an ultraviolet light-emitting fluorescent lamp. Addition of Cd in ZnO.Ga ₂ O ₃ : Cd may harm the environment, and the peak wavelength cannot be made smaller than 365 nm.

Recently, by adding Mg to a ZnO thin film that is a phosphor matrix to form a ZnMgO thin film and increasing the band gap of the matrix, the emission wavelength can be blue shifted (shifted to the short wavelength side). For example, by using a Zn _0.8 Mg _0.2 O composition, the peak wavelength of the emission spectrum is blue shifted to 462 nm. At this time, since the bottom of the short wavelength side is blue shifted to about 360 nm, which is ultraviolet light, the proportion of ultraviolet light emission is large in the entire spectrum, and it has the possibility of functioning as an ultraviolet light emitting phosphor (Non-patent Document 1). ).
JP 2001-176433 A JP-A-8-27769 JP-A-8-45438 JP 63-15879 A Annual Meeting of the Ceramic Society of Japan, 13 pages (2005)

However, this phosphor could only be produced with a thin film and could not be realized with powder. The reason will be described below.
According to the phase diagram of the ZnO-MgO system, Mg only dissolves up to about 4 mol% with respect to hexagonal ZnO, and beyond this, cubic MgO phase starts to precipitate in addition to hexagonal ZnMgO. Thin film technology has been developed as a method for dissolving Mg at a high concentration. That is, when a hexagonal single crystal such as sapphire is used as a substrate and a ZnMgO thin film is epitaxially grown thereon, Mg can be mixed up to a composition of Zn _0.6 Mg _0.4 O.
However, when a normal powder firing method in which ZnO and MgO powder are mixed and then fired is used, as described above, a solid solution is generated only up to a Zn _0.96 Mg _0.04 O composition which is a thermodynamic equilibrium composition.

  The present invention has been made to cope with such problems, and relates to a ZnMgO-based powder phosphor in which a high concentration of Mg is dissolved, a method for producing the same, and a light emitting device using the same.

That is, the present invention
(1) At least all or part of the surface has a surface layer represented by a chemical formula Zn _(1-x) R _x O (R is a Group IIA element, 0.05 ≦ x) and having a hexagonal crystal structure. Powder phosphor,
(2) The powder phosphor of the above (1), wherein R in the chemical formula is Mg,
(3) The powder phosphor according to (1) or (2), wherein 0.2 <x,
(4) The powder phosphor of (1) to (3) above, wherein a part of the spectrum having a peak on the short wavelength side in the cathodoluminescence spectrum is in a region smaller than the wavelength of 370 nm,
(5) The powder phosphor of (4) above, wherein a part of the spectrum having a peak on the short wavelength side in the cathodoluminescence spectrum is in a region smaller than a wavelength of 350 nm,
(6) The powder phosphor of (5) above, wherein a part of the spectrum having a peak on the short wavelength side in the cathodoluminescence spectrum is in a region smaller than the wavelength of 300 nm,

(7) The powder phosphor of the above (1) to (6), wherein the surface layer is formed on the surface of a micro substrate,
(8) The powder phosphor of (7) above, wherein the microsubstrate is a hexagonal crystal,
(9) The powder phosphor according to (7) or (8), wherein the micro-substrate is at least one of ZnO, sapphire, AlN, and SiC,
(10) The powder phosphor according to (7) to (9) above, wherein the micro-substrate is c-axis oriented,

(11) A method for producing a powder phosphor by a hydrothermal synthesis method, in which a powdery micro-substrate is dispersed in a solvent, and after dissolving a solute component containing Zn and Mg in the solvent of Step 1, The method for producing a powder phosphor according to (7) above, comprising the step 2 of precipitating the phosphor on a micro substrate by holding at a predetermined temperature and pressure,
(12) The method for producing a powder phosphor according to (11), wherein the micro-substrate is a hexagonal crystal,
(13) The method for producing a powder phosphor according to (11) or (12), wherein the micro-substrate is at least one of ZnO, sapphire, AlN, and SiC,
(14) The method for producing a powder phosphor according to the above (11) to (13), wherein the micro-substrate is c-axis oriented,

(15) A light emitting device that emits light by colliding electrons emitted from a hot cathode or a cold cathode with the powder phosphors of (1) to (10) formed on the anode,
(16) The light-emitting device according to (15), wherein the anode voltage is 5 kV or less,
It becomes more.

Since the Zn _(1-x) R _x O-based powder phosphor of the present invention is epitaxially grown on a micro substrate by hydrothermal synthesis, for example, a hexagonal solid solution can be formed even in a high concentration Mg composition. Such a high Mg composition powder phosphor is extremely promising as a phosphor for a fluorescent lamp because it can emit ultraviolet rays having a short wavelength by electron beam irradiation.

The production method of the present powder phosphor will be described below.
The product of the present invention can be produced by a hydrothermal synthesis method using epitaxial growth in a liquid phase. In the present invention, Step 1 in which a powdery micro-substrate is dispersed in a solvent, and a solute component containing Zn and Mg is dissolved in the solvent in Step 1 and then held at a predetermined temperature and pressure to cause fluorescence on the micro-substrate. It is obtained by precipitating the body. In the case where a micro substrate is used, it is preferable that the maximum average diameter is less than 100 μm.

The hydrothermal synthesis conditions are not particularly special conditions, and may be general ZnO hydrothermal synthesis conditions. As raw materials, besides using ZnO or MgO powder, nitrates such as Zn (NO ₃ ) ₂ .6H ₂ O, Mg (NO ₃ ) ₂ .6H ₂ O, and Zn (CH ₃ COO) ₂ .2H ₂ O Or acetate such as Mg (CH ₃ COO) ₂ .2H ₂ O may be used. Since nitrates and acetates are easily dissolved in water, there is no problem. However, when using ZnO or MgO powder, fine particles are preferred because they are easier to dissolve. These powders are preferably 1/10 or less of the size of the micro-substrate. The solvent may be deionized water, a mixed solution of KOH and LiOH, or the like. In general, the temperature is about 150 to 400 ° C. and the pressure is several MPa to several tens of MPa. The holding time is several hours to several hundred hours. In general, the smaller the cooling rate, the higher the crystallinity of the deposited ZnMgO.
For example, in a mixed solution of KOH having a concentration of 5.45 mol / l and LiOH having a concentration of 0.7 mol / l, as raw materials, ZnO powder having an average particle size of about 0.1 μm, MgO powder having a size of about 0.1 μm, and a minute amount As a substrate, a ZnO substrate having a size of about 5 μm and a thickness of about 1 μm is loaded and held at a temperature of 380 ° C. and a pressure of 20 MPa for 5 hours. Thereby, a part of ZnO and MgO powder which are raw materials melt | dissolve. On the other hand, a part of the micro-substrate is also dissolved, but since the size is larger and the dissolution rate is lower than the raw material powder, the dissolution amount is very small.
Note that the hydrothermal synthesis conditions described above are examples, and even if they are outside the above range, they may be suitable for depositing the phosphor on the micro substrate. For example, in a ZnMgO system, it is generally synthesized at a temperature of 300 to 800 ° C. and a pressure of several MPa to several tens of MPa.

  After that, when cooling to about 100 ° C. at a rate of 0.5 / min, the solubility decreases due to the temperature drop, so the supersaturation increases, and the ZnMgO component that can no longer be dissolved is deposited on the surface of the micro-substrate. is there. At this time, since the precipitated powder is affected by the orientation of the substrate, it is possible to precipitate while maintaining the hexagonal crystal even when the Mg concentration in the precipitated powder increases.

  The micro substrate preferably has a crystal system of hexagonal crystal or a lattice constant close to that of ZnMgO. Of course, ZnMgO is most preferable. Most preferably, it is hexagonal and has a close lattice constant. Hexagonal crystals include sapphire, GaN, AlN, SiC, InN, and the like. Those having a close lattice constant include cubic MgO and cubic SiC. In particular, GaN and AlN have close lattice constants. Sapphire is also relatively close. In the case of a hexagonal crystal, the c-plane is preferably developed. Such crystals are often hexagonal.

  The powder thus synthesized is extremely effective as a fluorescent lamp phosphor. In other words, a fluorescent lamp is characterized in that electrons emitted from a hot cathode or a cold cathode are caused to emit light by colliding with the present powder phosphor formed on the anode, and a high-intensity, low-power consumption lamp can be realized. . In particular, when the cathode is a cold cathode, the fluorescent lamp consumes less power. In general, when a phosphor is irradiated with a low-speed electron beam, if the phosphor has a high resistance, the phosphor surface will be charged negatively, causing a phenomenon in which stable light emission is inhibited. A so-called metal back treatment is necessary to release charges by forming, but the ZnMgO-based phosphor has a low resistance, so that such treatment is not necessary. This effect is significant when the anode voltage becomes 5 kV or less.

In the chemical formula Zn _(1-x) Mg _x O, x is preferably a solid solution up to a composition with 0.5 as the upper limit.
In the Zn _(1-x) Mg _x O composition, when the Mg content is 5 mol% or more, the emission peak wavelength is 370 nm or less. When the amount of Mg is 20 mol% or more, the emission peak wavelength is 350 nm or less. Since such ultraviolet rays can excite the titanium oxide photocatalyst very efficiently, it becomes effective as a light source for photocatalyst excitation. Moreover, since the ultraviolet light centered at 365 nm is used as the main light source of the ultraviolet resin curing device, it is also effective as a light source for the ultraviolet resin curing device. Phosphors with a Zn _(1-x) Mg _x O composition have extremely high luminous efficiency when excited with an electron beam, so high-intensity ultraviolet emission is possible even if only a part of the wavelength range of the emission spectrum can be used. It becomes.

When the amount of Mg is 40 mol% or more, the emission peak wavelength is 300 nm or less. Ultraviolet light having a wavelength of 300 nm is effective as a sterilizing lamp instead of a conventionally used mercury lamp because it has a high function of directly destroying DNA of organisms, microorganisms, bacteria, viruses and the like.
The present phosphor becomes a similar short wavelength luminescent powder phosphor even when a Group IIA element such as Be, Mg, Ca, Sr or Ba is used instead of Mg. In this case, the emission peak wavelength changes depending on the phosphor composition and the band gap of BeO, MgO, CaO, SrO, and BaO.

<Fabrication of phosphor>
(1) Raw materials The following were used as the first component.
Zn (CH ₃ COO) ₂ · 2H ₂ O: average particle size is 0.1 μm
The following were used as the second component.
Mg (CH ₃ COO) ₂ · 2H ₂ O: average particle size is 0.1 μm
Micro substrate:
(A) ZnO (hexagonal crystal): A c-plane growth product having a diameter of 50 mm and a thickness of 5 μm was pulverized to obtain a micro substrate having a diameter of 20 μm and a thickness of 5 μm.

(2) Hydrothermal treatment 100 ml of a mixed solvent of NaOH having a concentration of 5.45 mol / l and LiOH having a concentration of 0.7 mol / l was prepared.
The autoclave container was charged with a solvent, raw materials, and a fine substrate, sealed, and then loaded into an autoclave, and maintained at a temperature of 1700 ° C. and a pressure of 2 MPa for 24 hours. Thereafter, it was cooled to 100 ° C. at a rate of 0.5 ° C./min. The contents were taken out and the solvent was removed, followed by drying to obtain a powder. The powder was identified by powder X-ray diffraction. Powders were similarly prepared and evaluated by changing the addition amount of the second component Mg (CH ₃ COO) ₂ .2H ₂ O to the components shown in Table 1.
For comparison, powders were similarly prepared and evaluated without using a micro substrate.

<Production of fluorescent lamp>
15 μm or more of the produced phosphor was removed by sieving, and mixed with ethyl cellulose and an organic binder to obtain a slurry. The slurry was applied to an anode conductor made of an ITO film having a thickness of 0.1 μm formed on a quartz glass substrate having a size of 10 × 40 × 1 mm (thickness) using a screen printing machine, and 420 ° C. in the air. Then, the binder was removed by baking for 3 hours to prepare an anode substrate on which a phosphor layer having a thickness of 15 μm was formed. Separately, a slurry made of carbon nanotubes and an organic binder was applied to an aluminum electrode (thickness 0.1 μm) formed on a 8 × 38 × 1 mm (thickness) size soda lime glass substrate with a screen printer. Then, it was baked for 1 hour at 400 in an argon gas to produce a cold cathode.
A cold cathode and an anode are installed in parallel at a distance of 10 mm, and further, a mesh-like grid electrode having the same area as the cold cathode is provided between the cold cathode and the anode at a distance of 200 μm and an oxidation as a getter in advance. Various control electrodes in which barium was vapor-deposited by 0.1 μm were installed and wired. These were inserted into a quartz glass container having a diameter of 30 mm, a length of 200 mm, and a thickness of 1 mm, and then deaerated at 380 ° C. for 4 hours while the inside was evacuated to high vacuum (10 ⁻⁷ Pa). Thereafter, it was sealed with frit glass to obtain a fluorescent lamp.
While applying a grid voltage of 0.65 kV and a voltage of about 4 kV to the anode conductor, and controlling the anode current value to 100 μA, the phosphor emits light, and the emission wavelength from the anode side is measured with a multiphotonic analyzer (manufactured by Hamamatsu Photonics). It was measured. The results are shown in Table 1.

In the case where the micro substrate was not used, the cubic component was precipitated when the Mg amount was 5% or more of the whole (Zn + Mg). As a result of powder X-ray diffraction, MgO was present in the sample in which the cubic component was deposited. The emission peak wavelength did not become smaller than 374 nm.
On the other hand, when the micro substrate was used, the cubic component did not precipitate up to 50 mol% even when the amount of Mg increased. The emission peak wavelength was shortened with increasing amount of Mg. When the amount of Mg exceeded 20 mol%, the emission wavelength became 350 nm or less. When the amount of Mg exceeded 40 mol%, the emission wavelength became 300 nm or less.

<Fabrication of phosphor>
(1) Raw materials The following were used as the first component.
ZnO: average particle size of 0.1 μm
The following were used as the second component.
MgO: average particle size is 0.1 μm
Micro substrate:
(A) ZnO (hexagonal crystal): A c-plane growth product having a diameter of 50 mm and a thickness of 5 μm was pulverized to obtain a micro substrate having a diameter of 20 μm and a thickness of 5 μm.
(B) Sapphire (hexagonal crystal): A c-plane growth product having a diameter of 50 mm and a thickness of 5 μm was pulverized to obtain a micro substrate having a diameter of 22 μm and a thickness of 5 μm.
(C) GaN (hexagonal crystal): A c-plane growth product having a diameter of 50 mm × thickness of 5 μm was pulverized to obtain a micro substrate having a diameter of 18 μm × thickness of 5 μm.
(D) AlN (hexagonal crystal): A c-plane growth product having a diameter of 10 mm and a thickness of 5 μm was pulverized to obtain a micro substrate having a diameter of 19 μm and a thickness of 5 μm.
(E) SiC (hexagonal crystal): A c-plane growth product having a diameter of 50 mm and a thickness of 6 μm was pulverized to obtain a micro substrate having a diameter of 22 μm and a thickness of 6 μm.
(F) SiC (cubic crystal): A product having a diameter of 50 mm × thickness of 5 μm was pulverized to obtain a fine substrate having an average particle diameter of 5 μm.
(G) Quartz glass (amorphous): A product having a diameter of 20 mm × thickness of 5 mm was pulverized to obtain a fine substrate having an average particle diameter of 5 μm.

(2) Hydrothermal treatment 100 ml of KOH solvent having a concentration of 5.45 mol / l was prepared.
The solvent, the raw material, and the micro substrate of any one of the above (a) to (g) were charged in an autoclave container, and after sealing, the autoclave was charged and held at a temperature of 366 ° C. and a pressure of 20 MPa for 5 hours. Thereafter, it was cooled to 100 ° C. at a rate of 0.4 ° C./min. The contents were taken out and the solvent was removed, followed by drying to obtain a powder. The powder was identified by powder X-ray diffraction.

<Production of fluorescent lamp>
15 μm or more of the produced phosphor was removed by sieving, and mixed with ethyl cellulose and an organic binder to obtain a slurry. The slurry was applied to an anode conductor made of an ITO film having a thickness of 0.1 μm formed on a quartz glass substrate having a size of 10 × 40 × 1 mm (thickness) using a screen printing machine, and 420 ° C. in the air. Then, the binder was removed by baking for 3 hours to prepare an anode substrate on which a phosphor layer having a thickness of 15 μm was formed. Separately, a slurry made of carbon nanotubes and an organic binder was applied to an aluminum electrode (thickness 0.1 μm) formed on a 8 × 38 × 1 mm (thickness) size soda lime glass substrate with a screen printer. And it baked at 400 degreeC in argon gas for 1 hour, and produced the cold cathode.
A cold cathode and an anode are installed in parallel at a distance of 10 mm, and further, a mesh-like grid electrode having the same area as the cold cathode is provided between the cold cathode and the anode at a distance of 200 μm and an oxidation as a getter in advance. Various control electrodes in which barium was vapor-deposited by 0.1 μm were installed and wired. These were inserted into a quartz glass container having a diameter of 30 mm, a length of 200 mm, and a thickness of 1 mm, and then deaerated at 380 ° C. for 4 hours while the inside was evacuated to high vacuum (10 ⁻⁷ Pa). Thereafter, it was sealed with frit glass to obtain a fluorescent lamp.
While applying a grid voltage of 0.65 kV and a voltage of about 3 kV to the anode conductor and controlling the anode current value to 100 μA, the phosphor emits light, and the emission wavelength from the anode side is measured with a multiphotonic analyzer (manufactured by Hamamatsu Photonics). It was measured. The relative emission areas of the spectra were compared. The results are shown in Table 2.

The emission intensity increased as the lattice constant of the fine substrate was closer to that of the powder phosphor. When the misfit of the lattice constant between the substrate and the powder phosphor was large, the light emission shifted to the long wavelength side. It is presumed that Mg solid solution becomes small. The strength of the hexagonal substrate was higher.
The lattice constant misfit is shown below.
Lattice constant misfit (%) = (a-axis lattice constant of surface layer−a-axis lattice constant of substrate) / a-axis lattice constant of substrate × 100.

<Fabrication of phosphor>
(1) Raw material The following were used as the first component.
Zn (NO ₃ ) ₂ .6H ₂ O: Average particle size is 0.1 μm
The following were used as the second component.
Ca (NO ₃ ) ₂ · 6H ₂ O: Average particle size is 0.1 μm
Sr (NO ₃ ) ₂ · 6H ₂ O: average particle size is 0.1 μm
Ba (NO ₃ ) ₂ · 6H ₂ O: Average particle size is 0.1 μm
Micro substrate:
The same sapphire of Example 2 was used. The results are shown in Table 3.

  As shown in Table 3, even when CaO, SrO, or BaO nitrate was used, light was emitted at a short wavelength.

Claims (16)

It has a surface layer having a hexagonal crystal structure, the chemical formula of which is represented by Zn _(1-x) R _x O (R is a IIA group element, 0.05 ≦ x), at least on all or part of the surface. A powder phosphor. 2. The powder phosphor according to claim 1, wherein R in the chemical formula is Mg. The powder phosphor according to claim 1 or 2, wherein 0.2 <x. 4. The powder phosphor according to claim 1, wherein a part of the spectrum having a peak on the short wavelength side in the cathodoluminescence spectrum is in a region smaller than a wavelength of 370 nm. The powder phosphor according to claim 4, wherein a part of the spectrum having a peak on the short wavelength side in the cathodoluminescence spectrum is in a region smaller than the wavelength of 350 nm. 6. The powder phosphor according to claim 5, wherein a part of the spectrum having a peak on the short wavelength side in the cathodoluminescence spectrum is in a region smaller than the wavelength of 300 nm. The powder phosphor according to any one of claims 1 to 6, wherein the surface layer is formed on a surface of a minute substrate. The powder phosphor according to claim 7, wherein the micro substrate is a hexagonal crystal. 9. The powder phosphor according to claim 7, wherein the micro substrate is at least one of ZnO, sapphire, AlN, and SiC. The powder phosphor according to any one of claims 7 to 9, wherein the micro-substrate is c-axis oriented. A method for producing a powder phosphor by a hydrothermal synthesis method, in which a powdery micro-substrate is dispersed in a solvent, and a solute component containing Zn and Mg is dissolved in the solvent in step 1, and then a predetermined temperature is obtained. The method for producing a powder phosphor according to claim 7, further comprising a step 2 of depositing the phosphor on a micro substrate while being held under pressure. The method for producing a powder phosphor according to claim 11, wherein the micro-substrate is a hexagonal crystal. The method for producing a powder phosphor according to claim 11 or 12, wherein the micro-substrate is at least one of ZnO, sapphire, AlN, and SiC. The method for producing a powder phosphor according to claim 11, wherein the micro-substrate is c-axis oriented. A light-emitting device that emits light by causing electrons emitted from a hot cathode or a cold cathode to collide with the powder phosphor according to claim 1 formed on the anode. The light-emitting device according to claim 15, wherein the anode voltage is 5 kV or less.