WO2011030671A1

WO2011030671A1 - Method for producing zn-al-oxide fluorescent material

Info

Publication number: WO2011030671A1
Application number: PCT/JP2010/064448
Authority: WO
Inventors: 躍進単; 諒仁山口; 慶太郎手塚; 英夫井本
Original assignee: 国立大学法人宇都宮大学
Priority date: 2009-09-14
Filing date: 2010-08-26
Publication date: 2011-03-17
Also published as: JP5210272B2; JP2011057941A

Abstract

Disclosed is a production method wherein industrial production is possible of a low-cost Zn-Al-oxide fluorescent material via a simple method. The production method includes a starting material solution preparation step wherein a starting material solution is prepared by mixing a starting material containing at least a zinc salt and an aluminum salt with a solvent comprising an aqueous solution containing a water-soluble organic compound that can dissolve said starting material; a heat-concentrating step wherein the starting material solution is heat concentrated causing the water in the starting material solution to be eliminated, resulting in a highly viscous solution; a calcination step wherein the highly viscous solution is heat treated, eliminating at least a portion of the water-soluble organic compound in the highly viscous solution, resulting in an amorphous powder; and a roasting step wherein the amorphous powder is roasted in an inert gas ambient, resulting in a Zn-Al-oxide.

Description

Method for producing ZnAl-based oxide phosphor

The present invention relates to a method for producing a ZnAl-based oxide phosphor.

Spinel is derived from the mineral name of MgAl ₂ O ₄ (Japanese name: spinel), and its structure is based on a diamond structure, and its general chemical formula is represented as AB ₂ X ₄ . In this chemical formula, the A site forms an isolated tetrahedron surrounded by four X site anions (eg, oxide ions), and the B site is an octahedron surrounded by six anions and sharing sides. It is represented by the structure formed.

ZnGa ₂ O _4, which is a spinel-type ZnGa-based oxide, has been reported as an oxygen-deficient (matrix emission) blue phosphor (see, for example, Non-Patent Document 1 below). However, there is a problem that the price of Ga constituting the B site of ZnGa ₂ O ₄ is high and the cost is high as a whole. In order to reduce the cost, it is conceivable that B site uses inexpensive Al, but ZnAl ₂ O ₄ having the same structure as ZnGa ₂ O ₄ is known not to emit fluorescence because oxygen deficiency cannot be introduced. ing. Actually, the following Non-Patent Document 2 reports ZnAl ₂ O ₄ doped with Dy ³⁺ as the emission center, but using an oxygen-deficient phosphor that emits as a host light like ZnGa ₂ O _4. is not.

Since Ga in the ZnGa-based oxide is an expensive material, development of a ZnAl-based oxide phosphor typified by ZnAl ₂ O ₄ is desired as an inexpensive material instead. However, at present, ZnAl ₂ O ₄ does not emit light from the host body, and does not emit light unless doped with other elements. Therefore, the development of ZnAl-based oxide phosphors that emit inexpensive ZnAl ₂ O ₄ as a host without performing such doping has been an issue. In addition, development of a production method capable of industrial production of such ZnAl-based oxide phosphors by a simple method is also an issue.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a ZnAl-based oxide phosphor that can be industrially produced by a simple method without using expensive Ga. There is.

In order to cause ZnAl ₂ O ₄ to emit light as a host, it is considered necessary to introduce oxygen vacancies (also referred to as oxygen vacancies; hereinafter the same) in the crystal. However, ZnAl ₂ O ₄ is an oxide having a very stable spinel structure, and it is difficult to introduce defects, and it is difficult to form oxygen vacancies serving as emission centers. Therefore, as a result of intensive studies on the introduction of oxygen vacancies into ZnAl ₂ O ₄ , the present inventors have controlled the type and amount of water-soluble organic compounds used in the raw material solution in the production of oxides, and The inventors have found that oxygen vacancies can be introduced into ZnAl ₂ O ₄ by crystallization by firing in a reducing atmosphere after making it amorphous, and the present invention has been completed.

In order to solve the above problems, a method for producing a ZnAl-based oxide phosphor according to the present invention comprises mixing a raw material containing at least a zinc salt and an aluminum salt with a solvent comprising an aqueous solution containing a water-soluble organic compound that dissolves the raw material. A raw material solution preparing step for preparing a raw material solution, a heating and concentrating step for heating and concentrating the raw material solution to remove water in the raw material solution to obtain a high viscous solution, and a heat treatment for the high viscous solution. A calcining step of obtaining an amorphous powder by removing at least part of the water-soluble organic compound in the highly viscous solution, and firing the amorphous powder in an inert gas atmosphere to obtain a ZnAl-based oxide. And a firing step to be obtained.

According to this invention, a raw material solution preparation step of preparing a raw material solution prepared by mixing a raw material containing at least a zinc salt and an aluminum salt and a solvent comprising an aqueous solution containing a water-soluble organic compound that dissolves the raw material; Concentrate the solution by heating to remove the water in the raw material solution to make a highly viscous solution, and heat treat the highly viscous solution to remove at least part of the water-soluble organic compounds in the highly viscous solution Thus, an oxygen deficiency is introduced by a simple process because it includes a calcination step for obtaining amorphous powder and a firing step for obtaining ZnAl-based oxide by firing amorphous powder in an inert gas atmosphere. hard to typical oxide ZnAl ₂ O ₄ in it is possible to introduce the oxygen deficiency, resulting in providing child a manufacturing method of industrial production possible ZnAl based oxide phosphor in a simple way Can.

In a preferred embodiment of the method for producing a ZnAl-based oxide phosphor of the present invention, the water-soluble organic compound is glycerin.

According to this invention, since the water-soluble organic compound is glycerin, it becomes easy to introduce oxygen deficiency into the ZnAl-based oxide in the firing step, and it becomes easy to produce a ZnAl-based oxide phosphor having better light emission characteristics. .

In a preferred embodiment of the method for producing a ZnAl-based oxide phosphor of the present invention, the inert gas is nitrogen gas, argon gas, helium gas or a mixed gas thereof.

According to the present invention, since the inert gas is nitrogen gas, argon gas, helium gas or a mixed gas thereof, the oxide is baked in a non-oxidizing atmosphere. It becomes easier to introduce oxygen deficiency.

According to the method for producing a ZnAl-based oxide phosphor of the present invention, it is possible to provide a method for producing a phosphor that can be industrially produced by a simple method. Since the produced ZnAl-based oxide emits fluorescence, a novel ZnAl-based oxide phosphor can be produced without using expensive Ga, and can be preferably used as a fluorescent material for displays such as fluorescent lamps and PDPs. .

It is a powder X-ray-diffraction measurement result of the ZnAl type oxide obtained by changing baking temperature. Changing the molar ratio of glycerin and ZnAl ₂ O ₄ is a powder X-ray diffraction measurement results of the ZnAl based oxide. They are the measurement result of the fluorescence spectrum which measured the ZnAl type oxide fluorescent substance obtained by changing baking temperature with the excitation wavelength of 370 nm, and the measurement result of an excitation spectrum. The measurement result of the fluorescence spectra of ZnAl based oxide phosphor obtained by the molar ratio was varied was measured at excitation wavelength 370nm of glycerin and ZnAl ₂ O _4, the measurement results of the excitation spectrum. ZnAl based oxide phosphor and serving standard the measurement results of the fluorescence spectrum of the (CaWO _4). It is a measurement result of cathodoluminescence of the obtained ZnAl system oxide. It is a measurement result of the fluorescence spectrum (excitation wavelength of 370 nm) of the obtained ZnAl-type oxide. It is a TG-DTA measurement result of the obtained ZnAl-based oxide. It is an ESR measurement result of each ZnAl-based oxide.

Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[ZnAl-based oxide phosphor]
The ZnAl-based oxide phosphor obtained by the production method of the present invention is made of a ZnAl-based oxide having oxygen vacancies. Thereby, Al which is an inexpensive material can be used, and as a result, a ZnAl-based oxide phosphor can be provided without using expensive Ga. That is, by introducing oxygen vacancies into the ZnAl-based oxide, for example, ZnAl ₂ O ₄ that has been considered not to emit light can be emitted.

The ZnAl-based oxide phosphor is, in principle, a compound composed of Zn, Al, and O elements and has oxygen vacancies. The degree of oxygen deficiency in the ZnAl-based oxide phosphor is not easy to quantify, but if the composition formula of the ZnAl-based oxide is expressed by ZnAl ₂ O _4-x , x is usually larger than 0, Preferably it is 0.000001 or more and usually 0.001 or less. If it is the said range, it will become easy to ensure the light emission characteristic of ZnAl type oxide fluorescent substance.

Whether the ZnAl-based oxide phosphor has oxygen vacancies can be confirmed using an electron spin resonance (ESR) method. That is, the ESR method can detect free electrons in a substance, so that a signal appears if there is an oxygen deficiency. However, depending on the manufacturing method, carbon may be contained in the ZnAl-based oxide, so that a signal due to carbon may be detected by the ESR method. In this case, it becomes difficult to confirm the signal of oxygen deficiency due to the signal from carbon. Therefore, in the case where carbon is contained in the ZnAl-based oxide, for example, the carbon may be removed by firing in air and then analysis by the ESR method may be performed. The firing temperature for removing the carbon is, for example, by analyzing the sample before firing by the differential thermal-thermogravimetric simultaneous measurement (TG-DTA) method, and referring to the temperature at which weight loss due to carbon is observed. I can decide.

The properties of ZnAl-based oxide phosphors are usually powder at normal temperature / normal humidity (25 ± 5 ° C./50±10% RH). From the viewpoint of ensuring the light emission characteristics, it is preferable to use a white powder.

When the ZnAl-based oxide phosphor is powdery (particulate), the average particle size is usually 1 nm or more and 50 nm or less. The particle diameter can be measured, for example, by a small angle scattering X-ray method, and as a measuring device, for example, SmartLab manufactured by Rigaku Corporation can be used.

When the ZnAl-based oxide phosphor is in a powder form (particulate form), the specific surface area is usually 10 m ² / g or more and 200 m ² / g or less. The specific surface area can be measured using the BET method. As a measuring device, for example, Yuasa Ionics Co., Ltd. NOVA1200 can be used.

As shown in the examples described later, the ZnAl-based oxide thus configured can be confirmed to exhibit sufficient fluorescence even when inexpensive Al is used, and a novel ZnAl-based oxide without using expensive Ga. A phosphor can be provided. This ZnAl-based oxide phosphor preferably has an excitation wavelength of 350 nm or more. This makes it possible to excite with light close to visible light. Note that this ZnAl-based oxide phosphor is not a light emitter whose emission center is a dopant, but an oxygen-deficient light emitter that emits a base light. However, in this ZnAl-based oxide phosphor, a dopant may be appropriately introduced when higher light emission intensity is required depending on the practical application. In other words, any ZnAl-based oxide that emits light based on oxygen vacancies can be a ZnAl-based oxide phosphor here, even when elements other than Zn, AL, and O are included.

Such a ZnAl-based oxide phosphor can be obtained by the production method according to the present invention described later.

Since the obtained ZnAl-based oxide phosphor was confirmed to emit fluorescence as described later, a novel ZnAl-based oxide phosphor can be manufactured without using expensive Ga, and it can be used for displays such as fluorescent lamps and PDPs. It can be preferably used as a fluorescent material.

[Production method]
The method for producing a ZnAl-based oxide phosphor of the present invention provides a raw material solution prepared by mixing a raw material containing at least a zinc salt and an aluminum salt and a solvent comprising an aqueous solution containing a water-soluble organic compound that dissolves the raw material. A raw material solution preparation step, a heat concentration step for heating and concentrating the raw material solution to remove water in the raw material solution to make a highly viscous solution, and a heat treatment of the highly viscous solution to dissolve the water in the highly viscous solution. A calcining step of obtaining an amorphous powder by removing at least part of the organic compound; and a calcining step of calcining the amorphous powder in an inert gas atmosphere to obtain a ZnAl-based oxide having oxygen deficiency. Including. This makes it possible to introduce oxygen vacancies into the representative oxide ZnAl ₂ O _4, which is difficult to introduce oxygen vacancies by a simple process, and as a result, manufacture of a ZnAl-based oxide phosphor that can be industrially produced by a simple method. A method can be provided. Hereinafter, each step will be described.

The raw material solution preparation step is a step of preparing a raw material solution obtained by mixing a raw material containing at least a zinc salt and an aluminum salt and a solvent composed of an aqueous solution containing a water-soluble organic compound that dissolves the raw material. In the present invention, the ZnAl-based oxide is finally obtained. Therefore, even in this raw material solution preparation step, the blending amount of each salt is adjusted so that the oxide has a desired stoichiometric composition. For example, in order to obtain a spinel-type ZnAl-based oxide, the amount of each salt is adjusted so that the B site of AB ₂ X ₄ is composed of Al and the A site is composed of Zn. Good. As long as oxygen deficient fluorescence is emitted, other elements other than Al may be added to the B site, and other elements other than Zn may be added to the A site. In the raw material solution, such other salts can be blended in any amount.

Examples of the salt include acetate, nitrate, carbonate, hydrochloride and the like. As the salt, water-soluble salts are preferable. For example, as shown in the following experimental examples, zinc acetate or the like can be used as the zinc salt, and aluminum nitrate or the like can be used as the aluminum salt. Zinc salts and aluminum salts may be used as hydrates.

On the other hand, a solvent made of an aqueous solution containing a water-soluble organic compound is used as a solvent for dissolving the raw material made of such salt.

The water-soluble organic compound means an organic compound having a property of being dissolved in water and carbonized by heat treatment. Such a water-soluble organic compound is not particularly limited, and examples thereof include polyhydric alcohols, monosaccharides, disaccharides, and the like. From the viewpoint of easy introduction of oxygen deficiency, polyhydric alcohols may be used. preferable. The water-soluble organic compound is at least one selected from the group consisting of ethylene glycol, propylene glycol, 1,2-butylene glycol, 2,3-butylene glycol, trimethylene glycol, glycerin, erythritol, xylitol, and sorbitol. Is more preferable. Of these materials, glycerin is more preferably used as the water-soluble organic compound. Thereby, it becomes easy to introduce oxygen vacancies into the ZnAl-based oxide in the baking step, and it becomes easy to manufacture a ZnAl-based oxide phosphor having better light emission characteristics. More specifically, as described later, by using a polyhydric alcohol such as glycerin, it becomes easy to obtain a ZnAl-based oxide having oxygen deficiency. The water-soluble organic compound may be used by mixing any two or more of them in an arbitrary ratio within the scope of the present invention.

It is preferable to use a water-soluble organic compound having a boiling point or decomposition temperature higher than that of water. This is because, as will be described later, it is assumed that moisture is removed in the heating and concentration step, and at least a part of the water-soluble organic compound is removed in the subsequent calcination step. To explain this by taking the above preferred water-soluble organic compound as an example, the boiling point of water is 100 ° C., ethylene glycol (C2) is 197.6 ° C., and propylene glycol (C3) is 188 at 1 atm. 2 ° C, 1,2-butylene glycol (C4) is 192-194 ° C, 2,3-butylene glycol (C3) is 177 ° C, and trimethylene glycol (C3) is 210-211 ° C. Yes, glycerin (C3) is 290 ° C, erythritol (C4) is 330 ° C, xylitol (C5) is 216 ° C, and sorbitol (C6) is 296 ° C. That is, all the water-soluble organic compounds that are considered preferable have a boiling point higher than that of water.

The water-soluble organic compound is preferably a substance that coordinates with the elements constituting each salt. By including a water-soluble organic compound coordinated with an element constituting each salt as a solvent species, such a water-soluble organic compound is an element that constitutes each salt even after heat treatment in the calcining step described later. Probably coordinating to form an amorphous state or a microcrystalline state, and as a result, the remaining water-soluble organic compound C (carbon) of the water-soluble organic compound is coordinated by firing in the subsequent firing step. This is because it is presumed that a ZnAl-based oxide having oxygen deficiency can be obtained by performing a reducing action so as to partially extract oxygen. That is, it can be said that the water-soluble organic compound here is a water-soluble organic compound having a higher boiling point than water in which each salt is mainly dissolved and capable of coordinating with the elements constituting the salt. . As long as it is an organic compound having such characteristics, it may be the same organic compound as the above propylene glycol, ethylene glycol or the like, or another organic compound, but in the present invention, an OH group is present as shown in the examples described later. When a glycerin having three is used, a ZnAl-based oxide having an oxygen deficiency is obtained. Therefore, it is preferable to use a polyhydric alcohol such as glycerin.

A solvent composed of an aqueous solution containing a water-soluble organic compound is usually formed by dissolving a water-soluble organic compound in water. However, within the scope of the gist of the present invention, a material other than water and the water-soluble organic compound is prescribed. You may make it contain by content of. The content of water in the solvent is usually an amount that can sufficiently dissolve the raw materials. In addition, the content of the water-soluble organic compound in the same solvent is usually an amount that can reliably form a coordinate bond with the element constituting each salt in the raw material. It is preferable to make it contain excessively with respect to a salt and aluminum salt. If this is expressed by the ratio (molar ratio) of the amount of water-soluble organic compound to the amount of ZnAl-based oxide produced, the amount of water-soluble organic compound when the amount of ZnAl-based oxide is 1. The ratio is usually 1 or more, preferably 2 or more, more preferably 3 or more, still more preferably 5 or more, particularly preferably 9 or more, and usually 50 or less, preferably 40 or less, more preferably 35 or less, still more preferably 30. Hereinafter, it is particularly preferably 20 or less, most preferably 15 or less. If it is within the above range, a good ZnAl-based oxide phosphor can be easily obtained, but particularly when the substance amount ratio of the water-soluble organic compound is 9 to 15 when the substance amount of the ZnAl-based oxide is 1. It becomes easy to show strong fluorescence.

The mixing ratio of the solvent composed of the aqueous solution containing the water-soluble organic compound and the raw material is the above-described fluorescence characteristics, the solubility of the raw material, the coordinate bond between the element constituting each salt in the raw material and the water-soluble organic compound, which will be described later. What is necessary is just to determine suitably, considering each conditions, such as the temperature and time of heat concentration in the heating concentration process to perform, and the temperature and time of heat processing in a calcination process.

The heating concentration step is a step of heating and concentrating the raw material solution obtained in the raw material solution preparation step to remove water in the raw material solution to obtain a highly viscous solution. In this step, since heat concentration is performed at a temperature that can remove water in the raw material solution, the heating temperature is usually 100 ° C. or higher and 150 ° C. or lower. The atmosphere for the heat treatment is not particularly limited, and may be any of an air atmosphere, an inert atmosphere such as a nitrogen atmosphere and argon. The removal of water in the raw material solution preferably means that the water in the raw material solution is almost completely removed, and more preferably that the water in the raw material solution is completely removed. In the case where the light emission characteristics of the obtained ZnAl-based oxide phosphor are not impaired, moisture may remain in the raw material solution. The properties of the highly viscous solution obtained through the heat concentration step are usually sol.

The calcination step is a step of further heating the high-viscosity solution obtained by heat concentration to remove at least a part of the water-soluble organic compound in the high-viscosity solution to obtain an amorphous powder. At least a part of the water-soluble organic compound is removed by the heat treatment. However, when the water-soluble organic compound is excessively contained in the raw material solution with respect to the zinc salt and the aluminum salt in the raw material solution preparation step, the water-soluble organic compound is excessive. It is preferable to remove a water-soluble organic compound (for example, an organic solvent such as glycerin). More specifically, it is preferable to remove “remaining water-soluble organic compound” other than the necessary and sufficient water-soluble organic compound coordinated to the element constituting the salt by heat treatment.

The heat treatment temperature in the calcining step varies depending on the type of the water-soluble organic compound. For example, in the case of propylene glycol described above, the boiling point (188.2 ° C.) is about 60 ° C. (about 40 ° C. to 80 ° C.). The range is preferably about 250 ° C. (a range of about 230 ° C. to 270 ° C.). For example, in the case of the above-described glycerin, the boiling point (290 ° C.) is about 60 ° C. The range is preferably about 350 ° C. (range of about 330 ° C. to 370 ° C.). In any case, it is only necessary to remove at least a part of the water-soluble organic compound in the highly viscous solution by heat treatment to obtain an amorphous powder. The atmosphere for the heat treatment is not particularly limited, and may be any of an air atmosphere, an inert atmosphere such as a nitrogen atmosphere and argon. The amorphous powder can be confirmed by measuring the powder after the heat treatment with a powder X-ray diffractometer, so that a crystalline peak does not appear, and a so-called amorphous peak or microcrystalline peak is obtained. It is such a powder. The obtained amorphous powder is usually not white when a water-soluble organic compound or its carbide remains.

The firing step is a step of obtaining a ZnAl-based oxide having oxygen deficiency by firing amorphous powder in an inert gas atmosphere. This step can be called a reduction step because oxygen deficiency is generated. In the present invention, a desired ZnAl-based oxide exhibiting a white color can be obtained by firing in an inert gas atmosphere.

The firing temperature in the firing step is usually 800 ° C. or higher, preferably 850 ° C. or higher, more preferably 900 ° C. or higher, and usually 1500 ° C. or lower from the viewpoint of forming oxygen deficiency while removing the carbonized water-soluble organic compound. The temperature is preferably 1200 ° C. or lower, more preferably 1000 ° C. or lower.

In the firing step, the amorphous powder is fired in an inert gas atmosphere. The inert gas is preferably nitrogen gas, argon gas, helium gas or a mixed gas thereof. As a result, the oxide is fired in a non-oxidizing atmosphere, and as a result, oxygen vacancies are more easily introduced into the ZnAl-based oxide.

In the calcination step, a ZnAl-based oxide having oxygen deficiency can be obtained by performing a reducing action so that a part of C (carbon) extracts oxygen. Specifically, in the calcination step described above, C (carbon) of the carbonized water-soluble organic compound probably remains coordinate-bonded to the oxide constituent element in the amorphous state or the microcrystalline state, and does not coordinate-bond. Excess water-soluble organic compound is removed by heat treatment to produce an amorphous powder, but in the subsequent firing step, C (carbon) in the water-soluble organic compound that is probably coordinated to the oxide constituent element by firing. It is presumed that oxygen deficiency is given to the ZnAl-based oxide by reducing the oxygen so that a part of it extracts oxygen.

According to such a manufacturing method, no special equipment is required, and it is not necessary to perform high-temperature baking at 1100 ° C. or higher like powder baking. For this reason, a phosphor made of ZnAl-based oxide having oxygen deficiency can be manufactured by a relatively simple synthesis method.

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless it exceeds the gist.

[Experimental example 1: Confirmation of light emission characteristics, etc.]
(Sample preparation)
The sample was synthesized by the solution method.

Aluminum nitrate nonahydrate _{_{[Al (NO 3) 3 ·}} 9H 2 O] a raw material, a solution prepared solvent as water, zinc acetate dihydrate _{_{[(CH 3 COO) 2 Zn}} · 2H 2 O] and Were mixed at a molar ratio so as to obtain the desired composition, and a water-soluble organic compound (glycerin) was added to prepare a raw material solution. At this time, the substance amount (molar ratio) of glycerin with respect to the substance amount of ZnAl ₂ O ₄ finally obtained is such that (substance quantity of glycerin) / (substance quantity of ZnAl ₂ O ₄ ) is 3 times, 9 times, The raw material solution was prepared so as to be 15 times and 36 times (raw material solution preparation step).

Next, the raw material solution was heated and concentrated at about 120 ° C. to remove water in the raw material solution to obtain a sol (high viscosity solution) (heat concentration step).

Next, the sol was heated at 350 ° C. to obtain an amorphous powder (calcination step). After removing excess glycerin by calcination process, a brown powder was obtained. When powder X-ray diffraction measurement was performed, a broad amorphous or microcrystalline diffraction pattern that did not exhibit a crystalline peak was obtained. Indicated. This is considered to be based on the fact that glycerin is coordinated to Zn and Al constituting each salt.

Thereafter, this amorphous powder is further heated in an inert atmosphere (in a nitrogen atmosphere) at 800 ° C., 900 ° C., and 1000 ° C. for 7 hours, respectively, thereby introducing oxygen defects to obtain a target substance. (Firing process). The nitrogen atmosphere at this time was performed while constantly flowing nitrogen gas at a rate of 40 ml / min in the heating furnace, and after cooling to 200 ° C., the atmosphere was released to the atmosphere.

(X-ray diffraction measurement)
The X-ray diffraction measurement was performed using a RINT2200 type manufactured by Rigaku Corporation as a powder X-ray diffractometer under the conditions of CuKα rays, applied voltage of 40 kV, and applied current of 40 mA. The sample for which X-ray diffraction measurement was performed is
(A) Sample obtained by changing (substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 15 (molar ratio) and changing the heating temperature in the firing step to 800 ° C., 900 ° C., and 1000 ° C., respectively. ,
(A) Samples obtained by setting the heating temperature in the firing step to 900 ° C. and changing (amount of glycerin) / (amount of ZnAl ₂ O ₄ ) to 3, 9, 15, 36 (molar ratio), respectively. ,
It is.

FIG. 1 shows the result of powder X-ray diffraction measurement of ZnAl-based oxide obtained by changing the firing temperature. In the figure, the X-ray diffraction measurement result indicated by “800 ° C.” is obtained by firing at 800 ° C., and the X-ray diffraction measurement result indicated by “900 ° C.” is fired at 900 ° C. This is a sample obtained, and the X-ray diffraction measurement result indicated by “1000 ° C.” is obtained by baking at 1000 ° C.

FIG. 2 is a powder X-ray diffraction measurement result of a ZnAl-based oxide obtained by changing the molar ratio of glycerin and ZnAl ₂ O ₄ . In the figure, the X-ray diffraction measurement result indicated by “3” is that of a sample in which (substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 3, and X indicated by “9”. The result of the line diffraction measurement is that of the sample with (substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 9, and the X-ray diffraction measurement result indicated by “15” is (substance amount of glycerin) ) / (Substance amount of ZnAl ₂ O ₄ ) = 15, and the X-ray diffraction measurement result indicated by “36” is (substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 36.

(Fluorescence / excitation spectrum measurement)
Next, fluorescence / excitation spectrum measurement was performed on the sample subjected to powder X-ray diffraction measurement. For the fluorescence / excitation spectrum measurement, a spectrofluorometer (manufactured by JASCO Corporation, FP-6300 type) is used, and as a filter, a sharp cut filter L-37 (manufactured by HOYA Glass Co., Ltd.) with a wavelength of 370 nm or less is blocked. The sample was packed in a powder measurement folder and set in a spectrofluorometer for measurement. In addition, the detection of the double wave was eliminated by attaching a filter to the spectrofluorometer. The fluorescence spectrum was expressed by the result obtained by fixing the wavelength on the excitation side and scanning the wavelength on the fluorescence side. Specifically, the fluorescence wavelength measurement was performed by fixing the wavelength (λex) on the excitation side to 370 nm and scanning the wavelength on the fluorescence side. Moreover, the excitation spectrum was expressed as a result of plotting the fluorescence intensity against the excitation light wavelength by fixing the wavelength on the fluorescence side to the maximum wavelength, scanning the wavelength on the excitation side.

FIG. 3 shows a measurement result of a fluorescence spectrum obtained by measuring a ZnAl-based oxide phosphor obtained by changing a firing temperature at an excitation wavelength of 370 nm, and a measurement result of an excitation spectrum. In the figure, a spectrum indicated by “PL” is a fluorescence (emission) spectrum, and a spectrum indicated by “PLE” is an excitation spectrum. In addition, the measurement result of the fluorescence spectrum indicated by “800 ° C.” in the figure is a sample obtained by firing at 800 ° C., and the measurement result of the fluorescence spectrum indicated by “900 ° C.” is fired at 900 ° C. The measurement result of the fluorescence spectrum indicated by “1000 ° C.” is that of the sample obtained by baking at 1000 ° C. It can be seen from the figure that the sample fired at 900 ° C. exhibits the strongest fluorescence. When the sample was irradiated with 365 nm ultraviolet light and the emission color was observed, both ZnAl-based oxide phosphors fired at 800 ° C. and 900 ° C. emitted blue (475 nm).

FIG. 4 shows a measurement result of a fluorescence spectrum obtained by measuring a ZnAl-based oxide phosphor obtained by changing a molar ratio of glycerin and ZnAl ₂ O ₄ at an excitation wavelength of 370 nm, and a measurement result of an excitation spectrum. In the figure, a spectrum indicated by “PL” is a fluorescence (emission) spectrum, and a spectrum indicated by “PLE” is an excitation spectrum. Further, in the figure, the measurement result of the fluorescence spectrum indicated by “3” is that of the sample where (amount of glycerin) / (amount of ZnAl ₂ O ₄ ) = 3, indicated by “9”. The measurement result of the fluorescence spectrum is (sample amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 9, and the measurement result of the fluorescence spectrum indicated by “15” is Substance amount) / (substance quantity of ZnAl ₂ O ₄ ) = 15, and the measurement result of the fluorescence spectrum indicated by “36” is (substance quantity of glycerin) / (substance of ZnAl ₂ O ₄ ) Amount) = 36. From the figure, the result of strong fluorescence when the molar ratio is 9 to 15 times.

FIG. 5 shows the measurement results of the fluorescence spectra of the ZnAl-based oxide phosphor and the standard material (CaWO ₄ ). In the same figure, the measurement result of the fluorescence spectrum indicated by “ZnAl ₂ O ₄ ” is (sample substance amount of glycerin) / (substance quantity of ZnAl ₂ O ₄ ) = 9 and the firing temperature is 900 ° C. Is. The excitation wavelength is measured at 370 nm. Further, in the figure, the measurement results of the fluorescence spectra shown in "CaWO _4" is of CaWO ₄ sample as a standard. The excitation wavelength is measured at 256 nm. From the figure, it can be seen that a ZnAl ₂ O ₄ phosphor exhibiting fluorescence stronger than that of CaWO _{4 as} a standard substance can be obtained depending on manufacturing conditions.

In addition, as can be seen by comparing the excitation wavelengths in FIG. 5, the excitation wavelength can be set to 370 nm in the ZnAl ₂ O ₄ phosphor compared to CaWO ₄ that uses an excitation wavelength of 256 nm, and light close to visible light. It can be seen that it is possible to emit light.

(Measurement of particle size and specific surface area)
The particle size and specific surface area of the ZnAl-based oxide powder obtained by changing the molar ratio of glycerin and ZnAl ₂ O ₄ were measured.

The particle size was measured by a small angle scattering X-ray method, and a SmartLab manufactured by Rigaku Corporation was used as a measuring device. As a result, the particle size of the sample obtained as a firing temperature of 900 ° C., (amount of glycerin) / (amount of ZnAl ₂ O ₄ ) = 15 (a 15-fold molar ratio solvent) is 18.206 nm, The particle size of the sample obtained as a temperature of 900 ° C., (amount of glycerin) / (amount of ZnAl ₂ O ₄ ) = 36 (36-fold molar ratio solvent) is 16.919 nm, a firing temperature of 900 ° C., The particle size of the sample obtained as (substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 9 (9-fold molar ratio solvent) was 15.785 nm.

The specific surface area was measured by the BET method, and NOVA 1200 manufactured by Yuasa Ionics Co., Ltd. was used as a measuring device. As a result, the specific surface area of the sample obtained as calcination temperature 900 ° C., (amount of glycerin) / (amount of ZnAl ₂ O ₄ ) = 15 (15 times molar ratio of solvent) is 50.37 m ² / g. The specific surface area of the sample obtained as calcination temperature 900 ° C., (amount of glycerin) / (amount of ZnAl ₂ O ₄ ) = 36 (36-fold molar ratio solvent) was 84.57 m ² / g. It was.

[Experimental Example 2: Measurement of cathodoluminescence]
(Substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 54 and the firing temperature was 900 ° C., and the target substance was obtained in the same manner as in Experimental Example 1. And the cathodoluminescence of the obtained sample was measured.

(Cathodeluminescence measurement)
The measurement of cathodoluminescence was performed using S3000H manufactured by Hitachi, Ltd. The measurement conditions are as follows.

Spectrometer entrance / exit slit: 1000 nm / 1000 nm
Measurement wavelength range: 200-800nm
Measurement wavelength interval: 1 nm
1 wavelength integration time / time: 500μS
1 wavelength twice average

FIG. 6 shows the measurement results of the cathodoluminescence of the obtained ZnAl-based oxide. As can be seen from the figure, light emission by electron beam irradiation was confirmed for the sample obtained in this experimental example.

[Experimental example 3: Confirmation of light emission mechanism]
Using the sample obtained in Experimental Example 2 ((substance amount of glycerin) / (substance amount of ZnAl ₂ O ₄ ) = 54 and the firing temperature of 900 ° C.), the ZnAl system obtained in the present invention In order to confirm the light emission mechanism of the oxide phosphor (whether light emission is based on oxygen deficiency), the following experiment was conducted.

(Fluorescence spectrum measurement)
Under the same conditions as in Experimental Example 1, the fluorescence spectrum of the sample obtained in Experimental Example 2 was measured. FIG. 7 shows the measurement results of the fluorescence spectrum (excitation wavelength: 370 nm) of the obtained ZnAl-based oxide. The measurement result of the fluorescence spectrum indicated by “900 ° C., in N ₂ ” in the figure is that of the sample obtained in Experimental Example 2. As can be seen from the figure, fluorescence was also confirmed for the sample obtained in Experimental Example 2.

(TG-DTA measurement)
The sample (ZnAl-based oxide) was subjected to thermogravimetric analysis. For the thermogravimetric analysis, a differential thermothermal gravimetric simultaneous measurement apparatus (model: TG-DTA / 2020S) manufactured by Bruker AXS Co., Ltd. was used. FIG. 8 shows a TG-DTA measurement result of the obtained ZnAl-based oxide. As can be seen from FIG. 8, the first stage weight reduction is due to adsorbed moisture, and the second and third stage weight reduction is due to adsorbed carbon. From this result, it is understood that carbon is adsorbed (residual) in the ZnAl-based oxide (ZnAl ₂ O ₄ ) obtained in Experimental Example 2.

(ESR measurement)
From the results of FIG. 8, carbon adsorption was observed in the ZnAl-based oxide phosphor obtained in Experimental Example 2. From these results, it is considered that it is not the oxygen deficiency but the adsorbed carbon that is involved in the light emission of the ZnAl-based oxide phosphor. Therefore, ESR measurement was performed on the separately prepared black ZnAl-based oxide powder (ZnAl ₂ O ₄ , a sample considered to have excessive carbon attached because of black) and the ZnAl-based oxide obtained in Experimental Example 2. went. Furthermore, for the ZnAl-based oxide obtained in Experimental Example 2, a sample subjected to additional firing (in the atmosphere at 800 ° C. for 1 hour) was prepared, and ESR measurement was also performed on this sample. The reason why the additional baking is performed here is to remove carbon adhering to the ZnAl-based oxide obtained in Experimental Example 2 by performing high-temperature baking in the air. The additional baking temperature of 800 ° C. is determined with reference to the temperature range in which the weight loss of the adsorbed carbon in FIG. 8 occurs. The ESR measurement was performed using an electron spin resonance apparatus (manufactured by JEOL Ltd., model: JES-TE100).

FIG. 9 shows the ESR measurement result of each ZnAl-based oxide. The signal indicated by “excess-carbon” in the upper part of the figure is the ESR measurement result of the black ZnAl-based oxide, and the signal indicated by “900 ° C. in N ₂ ” in the upper part of the figure is obtained in Experimental Example 2. The signal shown by “900 ° C. in N ₂ + 800 ° C. in air 1h” in the lower part of the figure is the result of additional firing of the ZnAl-based oxide obtained in Experimental Example 2 ( It is an ESR measurement result of a sample obtained by performing at 800 ° C. for 1 hour in the air.

The upper part of FIG. 9 is the ESR measurement result of the black ZnAl-based oxide powder as described above. Since this ZnAl-based oxide is a black powder and carbon is excessively attached, a signal with an interest (g = 2.0) due to carbon appears strongly.

9 shows the ESR measurement result of the ZnAl-based oxide obtained in Experimental Example 2 as described above. Also in this ZnAl-based oxide, a signal at g = 2.0 appears. This is due to carbon remaining in the sample, as confirmed from the above TG-DTA measurement. Of course, the vertical axis is enlarged for the middle signal so that the signal strength looks the same in the upper and middle parts of FIG. In comparison, the signal intensity at the middle stage is very small. That is, it can be seen that the ZnAl-based oxide obtained in Experimental Example 2 has a very small amount of carbon deposition compared to the black ZnAl-based oxide. This is presumed to suggest that carbon is surely removed by setting the firing temperature to 900 ° C. in the firing step, and oxygen deficiency is introduced as the carbon is removed.

The lower part of FIG. 9 is an ESR measurement result of a sample obtained by additionally firing the ZnAl-based oxide obtained in Experimental Example 2 (in the atmosphere at 800 ° C. for 1 hour) as described above. As can be seen from the figure, the signal with g = 2.0 was completely extinguished and only a weak signal remained. This indicates that carbon was almost completely removed by the additional firing. This signal is similar to the ESR signal of ZnGa ₂ O ₄ introduced with oxygen deficiency reported in Non-Patent Document 1.

(Measurement of fluorescence spectrum again)
From the measurement results of ESR, it was found that when the ZnAl-based oxide obtained in Experimental Example 2 was further baked (in the atmosphere at 800 ° C. for 1 hour), carbon in the oxide was almost removed. If the ZnAl-based oxide from which most of the carbon has been removed emits fluorescence, it can be proved that the emission does not involve carbon and the emission is based on oxygen vacancies. Then, the fluorescence spectrum measurement was performed about the sample which performed additional baking (1 hour at 800 degreeC in air | atmosphere). The measurement results are shown in FIG. In the figure, the spectrum indicated by “900 ° C., in N ₂ + 800 ° C. in air, 1 h” is the fluorescence spectrum of the sample obtained by performing additional firing on the ZnAl-based oxide obtained in Experimental Example 2.

As can be seen from the figure, although there was a difference in emission intensity, emission was confirmed even in the ZnAl-based oxide subjected to additional firing with almost no carbon residue. From this result, it was proved that the fluorescence emission in the ZnAl-based oxide obtained in the present invention was based on oxygen deficiency.

Claims

A raw material solution preparation step of preparing a raw material solution formed by mixing a raw material containing at least a zinc salt and an aluminum salt and a solvent comprising an aqueous solution containing a water-soluble organic compound that dissolves the raw material;
A heating and concentration step of concentrating the raw material solution to remove water in the raw material solution to obtain a highly viscous solution;
A calcining step of obtaining an amorphous powder by heat-treating the high-viscosity solution to remove at least a part of the water-soluble organic compound in the high-viscosity solution;
A baking step of baking the amorphous powder in an inert gas atmosphere to obtain a ZnAl-based oxide;
A method for producing a ZnAl-based oxide phosphor, comprising:
The method for producing a ZnAl-based oxide phosphor according to claim 1, wherein the water-soluble organic compound is glycerin.
The method for producing a ZnAl-based oxide phosphor according to claim 1 or 2, wherein the inert gas is nitrogen gas, argon gas, helium gas or a mixed gas thereof.