JP2007217202A - Method for producing complex metal oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently and inexpensively producing a single-phase complex metal oxide having a small particle diameter and a homogeneous chemical composition by a liquid phase process using a smaller amount of an organic compound and more particularly, to provide a method for producing inexpensively with reduced environmental load a complex metal oxide phosphor having excellent crystallinity, a high luminance equivalent to that of a conventional large particle and realizing high-definition displays, high-luminance lighting elements or fixtures, or high-speed immunoassay systems. <P>SOLUTION: The method for producing the complex metal oxide is a method for producing a complex metal oxide by a liquid phase process using an organic compound, wherein the amount of the organic compound used is 0.1 to 10 pts.wt., per 1 pt.wt. complex metal oxide produced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a composite metal oxide by a liquid phase method. Specifically, the chemical composition is small and has a uniform chemical composition suitable for a magnetic material, a dielectric material, a phosphor, a photocatalyst, a conductor, a filter pigment, and the like. The present invention relates to a method for efficiently producing a single-phase composite metal oxide.

  Composite metal oxides, in particular, composite metal oxides containing metals whose valence is easily changed, typified by transition metals, are used in magnetic materials, dielectrics, phosphors, photocatalysts, conductors, filter pigments, and the like. . Such a composite metal oxide is required to have a fine particle size, a highly single phase, and a chemically uniform composition.

  Conventionally, composite metal oxides, for example, in the case of production of oxide phosphors, use a plurality of compounds containing metal elements constituting phosphors as raw materials, and after mixing these raw materials, 1400 ° C. or higher It is common to produce a composite metal oxide by a solid-solid reaction by firing at a high temperature for a long time (solid phase method).

  However, in order to produce a composite metal oxide by this solid phase method, it is necessary to perform firing for a long time at a high temperature, and as a result, the particle diameter of the composite metal oxide (phosphor) also increases. In order to obtain a strong and small particle size, it is necessary to pulverize and classify the baked product, but this calcination pulverization method has a low yield and is difficult to adjust the particle size. If the firing temperature is lowered, unreacted raw materials remain, so the firing temperature has to be set to a high temperature of, for example, 1400 ° C. or higher. Such high-temperature firing cannot avoid volatilization of the low boiling point metal element in the production of the composite metal oxide containing the low boiling point metal element, and therefore, a single-phase complex metal oxide having a uniform chemical composition. Could not get.

On the other hand, in addition to the solid phase method, there are the following liquid phase methods as a method for producing the composite metal oxide.
(B) A plurality of organic acid metal salts are dissolved in an organic solvent together with citric acid, and then heated to evaporate a part of the organic solvent to form a gel-like precursor, which is thermally decomposed. Citric acid method (for example, Non-Patent Document 1)
(B) A coprecipitation method in which a precipitation agent such as alkali or oxalic acid is added to an aqueous solution of a plurality of metal salts to coprecipitate metal hydroxides or oxalates and the resulting precipitate is oxidized. An alkoxide method for thermally decomposing a metal alkoxide obtained by the reaction of a plurality of metal compounds and an alcohol. (D) A complex containing a metal ion group capable of forming a composite metal oxide can be decomposed under the action of heat. A method of forming a stable solution of a curable organic substance, rapidly concentrating the solution to form a solid, and thermally decomposing the solid (see, for example, Patent Document 1)
(E) a complex polymerization method in which a polyol is added to a solvent containing a plurality of metal salts and / or alkoxides and an oxycarboxylic acid or a polyamino chelating agent (see Patent Document 2)
(F) After dissolving a compound of a plurality of metal elements and polyvinyl alcohol in a solvent and reacting both to form a metal complex, the metal complex is heated and gelled by heating to remove the solvent. And a method of further heating the generated gel to generate a precursor of a composite metal oxide and then firing the precursor (see Patent Document 3)

  Among these liquid phase methods, the (a) citric acid method and the (c) alkoxide method differ in the solubility of each raw material compound when the organic solvent in the raw material is removed. It is difficult to obtain, and the production of the complex metal oxide is complicated. In particular, in the (c) alkoxide method, the individual components in the raw material are extremely difficult to uniformly disperse due to the difference in the hydrolysis reaction rate of each metal element. In addition, (b) the coprecipitation method has a narrow operation range for coprecipitation, so the applicable metal elements are limited, and it is difficult to freely select the combination of metal elements and the ratio of metal elements. A metal oxide cannot be obtained. Furthermore, the (e) complex polymerization method has to use a large amount of complex-forming organic matter in order to obtain a uniform composition, and it is disadvantageous to emit a large amount of carbon dioxide during firing. There is a need for improvement in terms of manufacturing costs. Also in the method (f), polyvinyl alcohol is used in a large amount and has the same drawbacks as the method (e).

  A phosphor is mentioned as a typical example of the industrial product in which a composite metal oxide is used. Conventionally, a phosphor used for a cathode ray tube, a field emission display (FED) or the like has a median particle diameter (median diameter d50) of primary particles constituting the phosphor of 5 μm to 30 μm, and grows a host crystal constituting the phosphor greatly. As a result, the volume fraction of the non-radiation-inactivated layer present on the particle surface was reduced to obtain a powder having high luminance. In addition, primary particles made of single crystals grown in this manner absorb energy such as electron beams, ultraviolet rays, and X-rays, and efficiently emit fluorescence. For example, such a phosphor has an internal quantum efficiency defined by the number of photons emitted with respect to the number of photons absorbed when the phosphor is excited by irradiating with ultraviolet rays having a wavelength of 254 nm. Shows high efficiency.

  A conventional phosphor manufacturing method generally includes mixing raw material powders, putting them in a firing vessel such as a crucible, and generating and crystallizing the phosphors by a solid-phase reaction that is heated at a high temperature, and then using a ball mill or the like. This is a pulverization method (see, for example, Non-Patent Document 2).

  However, the phosphors produced by this method are often composed of aggregate powders, which are secondary particles formed by agglomeration of primary particles that are single crystals. Fluorescent films such as cathode ray tubes and FEDs obtained by forming the film are inhomogeneous and have a low packing density, and thus have low luminous efficiency.

  In addition, phosphor particles having a desired particle diameter are obtained by pulverizing with a ball mill or the like after the solid phase reaction, and at that time, physical and chemical impacts are applied. There is a disadvantage that the crystal habit plane appearing is reduced, and defects are generated in the particles or on the surface, resulting in a decrease in luminous efficiency.

  On the other hand, in recent years, phosphors with finer and higher brightness than the particle size obtained by the conventional technology have been required from the viewpoint of luminous efficiency for solid-state lighting elements and the like for pixel definition in FEDs and the like. Yes. In response to these requirements, miniaturization by pulverization after firing is not possible, and the conventional method has a large decrease in luminous efficiency, low internal quantum efficiency, and a desired phosphor cannot be obtained. High-definition display and high-efficiency lighting could not be obtained.

  On the other hand, when the particles obtained by solid phase reaction are made fine, it is necessary to lower the reaction temperature. However, in this case, the reaction does not proceed completely and the impurity phase is mixed, resulting in incomplete crystal growth of the particles. As a result, the phosphor obtained has a low internal quantum efficiency, leading to a decrease in light emission characteristics.

Various additives, synthesis methods, and treatment methods have been reported to improve the fluorescence intensity of the phosphor. For example, in Non-Patent Document 3, the emission intensity is improved by adding a lithium salt in the process of synthesizing Y ₂ O ₃ : Eu ³⁺ , causing gelation and self-combustion reaction. In Non-Patent Document 4, it is reported that the Y ₃ site of Y ₂ O ₃ : Eu ³⁺ is doped with La to improve concentration quenching of Eu ³⁺ by synthesis using hydrolysis using microwaves.
Japanese Patent Publication No.49-6040 JP-A-6-115934 JP 11-314905 A Journal of the Japan Institute of Metals, Vol. 26, No. 10, pp. 943-949 "Phosphor Handbook" (published by Ohm Corporation), page 166 Takeda, et al., Proceedings of the 18th Autumn Symposium of the Ceramic Society of Japan, 175 pages N. Imanaka, et al, Electrochemical and Solid-State Letters, 7 (6) D7-D9 (2004)

  Thus, in order to produce a composite metal oxide capable of providing a phosphor having high internal quantum efficiency and excellent emission characteristics, the solid phase method cannot be used, and an improvement of the liquid phase method is expected.

  Therefore, the present invention eliminates the above-mentioned problems in producing composite metal oxides by the liquid phase method, and uses a small amount of organic compound, small particle size, uniform chemical composition, and single-phase composite metal oxide. An object of the present invention is to provide a method for efficiently and inexpensively producing a slag.

  In particular, the present invention is capable of realizing a high-definition display, a high-luminance lighting element, a lighting fixture, a high-speed immunoassay system, and the like. It aims at providing the method of manufacturing a metal oxide fluorescent substance cheaply, reducing the load with respect to an environment.

  The present invention makes it possible to solve the above problems by adopting the following configurations (1) to (10).

(1) In the method for producing a composite metal oxide by a liquid phase method using an organic compound, the organic compound is 0.1 parts by weight or more and 10 parts by weight or less based on 1 part by weight of the produced composite metal oxide. A method for producing a composite metal oxide, characterized by being used.

(2) The method for producing a composite metal oxide according to (1), comprising the following steps.
a) Step of dissolving at least one metal element compound and polyvinyl alcohol in a solvent and reacting both to form a metal complex b) Step of gelling by removing the solvent from the liquid produced by the metal complex c) Step of generating a composite metal oxide precursor by heating the generated gel d) Step of heat-treating the composite metal oxide precursor

(3) The method for producing a composite metal oxide according to (1), comprising the following steps.
e) In water, a compound of at least one metal element selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W and Bi (hereinafter referred to as “first metal element”), and hydroxy A step of preparing a hydroxycarboxylic acid complex aqueous solution of the first metal element by reacting with a carboxylic acid; f) at least one different from the first metal element in the hydroxycarboxylic acid complex aqueous solution of the first metal element; A step of adding a compound of a seed metal element and polyvinyl alcohol to obtain a mixed solution; g) a step of removing water from the mixed solution to form a gel; h) a composite metal oxide precursor by heating the formed gel; Step i) Step of heat-treating the composite metal oxide precursor

(4) The method for producing a composite metal oxide according to any one of (1) to (3), including a microwave irradiation step on the composite metal oxide precursor or the heat-treated product thereof.

(5) The method for producing a composite metal oxide according to any one of (1) to (4), wherein a primary particle size of the obtained composite metal oxide is 0.05 μm or more and 5 μm or less.

(6) A composite metal oxide obtained includes a rare earth element or an alkaline earth element and at least one metal element selected from Nb, V, Ta, Ti, Zr, Hf, Mo, W, and Bi. It is a metal oxide phosphor, The manufacturing method of the composite metal oxide in any one of (1)-(5) characterized by the above-mentioned.

(7) The method for producing a composite metal oxide according to (6), wherein the obtained composite metal oxide phosphor is represented by any one of the following composition formulas [1] to [3].
(Ln _1-x R _x ) M ¹ O ₄ ... [1]
(E _1-x R _x ) M ² O ₃ ... [2]
(E _1-x R _x ) M ³ O ₄ ... [3]
(In the composition formulas [1] to [3], Ln is at least one element selected from the group consisting of Sc, Y, La, Gd and Lu, and E is selected from the group consisting of Mg, Ca, Sr and Ba. At least one element, M ¹ is at least one element selected from the group consisting of Nb, V and Ta, M ² is at least one element selected from the group consisting of Ti, Zr and Hf, and M ³ is Mo And at least one element selected from the group consisting of W, R is at least selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Mn, Sb and Bi. Represents one element, and x is a number satisfying 0 ≦ x ≦ 0.5.)

(8) The method for producing a composite metal oxide according to (7), wherein the obtained composite metal oxide phosphor is represented by the following composition formula [4].
^{_{(Ln 1-x R x)}} (Nb 1-y M 1 y) O 4 ······ [4]
(In composition formula [4], Ln, M ¹ , R, and x have the same meaning as in composition formula [1], and y is a number that satisfies 0 ≦ y ≦ 0.5.)

(9) The method for producing a composite metal oxide according to any one of (1) to (8), comprising a step of adding an alkali metal to the reaction system.

(10) The method for producing a mixed metal oxide according to any one of (1) to (9), comprising a step of adding Tb and / or Pr to the reaction system.

  According to the method for producing a composite metal oxide of the present invention, a single-phase composite metal oxide having a small particle size and a uniform chemical composition can be efficiently produced by a liquid phase method. Moreover, since the method of the present invention can select an aqueous solvent, the amount of the organic compound used is small, the load on the environment is small, and the manufacturing cost can be reduced.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to the gist of the present invention. The content of is not specified.

[Production of composite metal oxides]
The method for producing a composite metal oxide of the present invention is a method for producing a composite metal oxide by a liquid phase method using an organic compound, wherein the organic compound is added to 1 part by weight of the produced composite metal oxide. This is a method for producing a composite metal oxide with a small amount of organic compound used of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight.

  Here, when the amount of the organic compound used is less than 0.1 part by weight with respect to 1 part by weight of the composite metal oxide to be produced, a composite metal oxide having a uniform chemical composition cannot be produced, and exceeds 10 parts by weight. In addition, the object of the present invention for reducing the production cost by reducing the use amount of the organic compound and reducing the burden on the environment cannot be achieved.

In the method for producing a composite metal oxide of the present invention, the composite metal oxide is specifically produced through the following steps a) to d).
a) Step of dissolving at least one metal element compound and polyvinyl alcohol in a solvent and reacting both to form a metal complex b) Step of gelling by removing the solvent from the liquid produced by the metal complex c) Step of generating a composite metal oxide precursor by heating the generated gel d) Step of heat-treating the composite metal oxide precursor

  That is, in the method for producing a composite metal oxide of the present invention, a compound of each metal element constituting the composite metal oxide and polyvinyl alcohol (hereinafter referred to as “PVA”) are dissolved in a solvent, and both are reacted to form a metal. After the complex is formed, it is gelled by removing the solvent from the liquid containing the generated metal complex by holding it at a certain temperature, for example, by heating as necessary, and then thermally decomposing PVA to complex metal In this method, a precursor of an oxide is manufactured, and then this precursor is heat-treated to manufacture a composite metal oxide.

  Hereinafter, this method is referred to as a PVA method.

  The PVA used in the present invention has a polymerization degree of 300 to 100000, preferably 500 to 2000, and a saponification degree of 70 to 100 mol%, preferably 80 to 90 mol%. Suitable because it has good solubility in water. As PVA, modified PVA modified with a cation or an anion may be used.

  In addition, as the solvent used in the present invention, various liquids can be used. Among them, one or more of water, alcohol, acetone and the like are preferable from the viewpoint of simplifying the manufacturing process and reducing the manufacturing cost. In particular, it is particularly preferable to use water.

In the method for producing a composite metal oxide of the present invention, the composite metal oxide is more preferably produced through the following steps e) to i).
e) In water, a compound of at least one metal element selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W and Bi (hereinafter referred to as “first metal element”), and hydroxy A step of preparing a hydroxycarboxylic acid complex aqueous solution of the first metal element by reacting with a carboxylic acid; f) at least one different from the first metal element in the hydroxycarboxylic acid complex aqueous solution of the first metal element; A step of adding a compound of a seed metal element and polyvinyl alcohol to obtain a mixed solution; g) a step of removing water from the mixed solution to form a gel; h) a composite metal oxide precursor by heating the formed gel; Step i) Step of heat-treating the composite metal oxide precursor

  The steps e) to i) will be described below.

e) Step: In water, a compound of at least one metal element selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W, and Bi (hereinafter referred to as “first metal element”) The step of preparing a hydroxycarboxylic acid complex aqueous solution of a first metal element by reacting with a hydroxycarboxylic acid, f) In the step, the first metal element compound and the hydroxycarboxylic acid are used in water to form a first An aqueous solution is prepared by forming a hydroxycarboxylic acid complex of a metal element.

  The method for producing a composite metal oxide of the present invention is particularly a composite metal oxide containing at least one metal element selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W and Bi. It is effective for manufacturing. In order to make these metal elements into solution, it is generally necessary to use a coordination compound having a high carbon content as a counter anion. As a result, a large amount of organic matter and carbon dioxide are used in the thermal decomposition process of the precursor. However, according to the present invention, by using hydroxycarboxylic acid, it is possible to make a solution with a small amount of organic compound, and as a result, the heat of the precursor in the latter stage can be reduced. This is because an organic substance removed in the decomposition step and a precursor with a small amount of carbon dioxide are obtained. At this time, by using hydroxycarboxylic acid, a solution containing no halogen can be obtained. If the solution does not contain halogen as described above, the halogen content of the resulting composite metal oxide can be reduced. For example, it is effective in improving the light emission characteristics of the phosphor.

Here, the first metal element compound as a starting material is not particularly limited, and is a chloride, oxide, hydroxide, acetate, nitrate, carbonate, sulfate, fluoride of the first metal element. Etc. can be used. To this first metal element compound, H ₂ O ₂ which is a peroxo complex forming agent and an alkaline compound such as NH ₃ and hydrazine are added, and then an organic solvent miscible with water such as ethanol, methanol and acetone is added. Then, a peroxo compound of the first metal element is generated, and the peroxo compound of the first metal element and the hydroxycarboxylic acid are reacted to form a complex.

  Thus, by producing a peroxo compound of the first metal element and reacting it with a hydroxycarboxylic acid, a stable solution as a complex is obtained, which is preferable.

  In order to form a hydroxycarboxylic acid complex of the first metal element, the peroxo compound of the first metal element and the hydroxycarboxylic acid are mixed in a solvent, preferably water, in a ratio of 1: 1 to 1: 5 (molar ratio). React at a rate. The more the hydroxycarboxylic acid is, the easier the dissolution of the peroxo compound is. However, since excess organic matter increases, it is preferable to use as little hydroxycarboxylic acid as possible.

  The hydroxycarboxylic acid used here has a high ability to form a complex with a metal element compound even if it contains a small amount of carbon atoms, and prepare a precursor with a low carbon content per unit amount of the metal element. This is suitable for the present invention.

  The hydroxycarboxylic acid used in the present invention is preferably a hydroxycarboxylic acid having 2 to 5 carbon atoms such as glycolic acid, lactic acid, malic acid, tartaric acid, citramalic acid (2-methylmalic acid), among which glycolic acid and lactic acid are preferred. preferable. One kind of hydroxycarboxylic acid may be used alone, or two or more kinds thereof may be mixed and used.

f) Step: In the hydroxycarboxylic acid complex aqueous solution of the first metal element obtained in step e), a compound of at least one metal element different from the first metal element and polyvinyl alcohol, preferably an aqueous polyvinyl alcohol solution In step f), one or two metal elements different from the first metal are added to the aqueous solution of the first metal element hydroxycarboxylic acid complex obtained in step e). The above-described compound (hereinafter referred to as “second metal element”) and the PVA aqueous solution are added to obtain a mixed solution. PVA is not an aqueous solution but can be added as it is, but it is preferably added as an aqueous solution in order to increase the solubility of PVA.

  Here, as the compound of the second metal element, one or more of chloride, oxide, hydroxide, acetate, nitrate, carbonate, sulfate, fluoride, etc. of the second metal element are used. Can be used.

  The compound of the second metal element is added in such a ratio that a composite metal oxide having a target chemical composition can be obtained.

  In preparing this mixed solution, an acid and complex forming agent such as acetic acid and citric acid is used at a ratio of metal: acid complex forming agent of 1: 1 to 1: 5 (molar ratio). By adding, it can be dissolved stably.

  The PVA concentration in the obtained mixed solution is preferably 0.1% by weight or more and 10% by weight or less. If the PVA concentration is too low, metal ions are hydrolyzed during the removal of the solvent to cause segregation. If the PVA concentration is too high, dissolution of PVA is difficult and excessive organic matter increases, which is not preferable. Moreover, it is preferable that the metal element compound density | concentration in a mixed solution is 10 weight% or less in total. When the concentration of the metal element compound is too high, segregation occurs. When the concentration is too low, a large amount of solvent or organic matter is wasted for the amount of the composite metal oxide to be generated, which is not preferable.

  Further, in the present invention, in order to obtain a composite metal oxide having a uniform composition after reducing the amount of organic compound used per composite metal oxide to be produced, the PVA (including modified PVA) used in this step, e) The total addition amount with the hydroxycarboxylic acid used in the step is 0.5 times or more by weight with respect to the total weight of all metal elements (all metal elements constituting the composite metal oxide) in the raw metal compound. It is preferably 1 times by weight or more, more preferably 10 times by weight or less, and more preferably 3 times by weight or less. If the amount of PVA and hydroxycarboxylic acid used is less than this lower limit, the gelation reaction is unlikely to occur, and there is a possibility that a uniform metal complex cannot be formed. Although the effect of uniformly dispersing does not increase, it is not preferable because the amount of organic matter used increases, the production cost of the composite metal oxide increases, and the amount of organic matter and carbon dioxide discharged during heating increases.

g) Step: f) Step of removing water from the mixed solution obtained in step to gel, and f) Step, forming a metal complex by reaction of raw material metal element ions with hydroxycarboxylic acid and / or PVA After the gelation treatment, a mixed solution containing metal element ions and hydroxycarboxylic acid and / or PVA (modified PVA or cationic and / or anionic polymer compound may coexist) is used. This is done by keeping the temperature constant. The holding temperature at this time is 10 to 250 ° C, preferably 100 to 200 ° C. When the holding temperature is lower than 10 ° C., it takes a long time for gelation, which is not preferable. When the holding temperature is higher than 250 ° C., the hydroxycarboxylic acid and / or PVA is thermally decomposed early and a desired gel is not formed. In addition, there is a risk of producing a composite metal oxide having a non-uniform chemical composition. This temperature holding is continued further after the gel is formed until the water is removed. The removal of water by this temperature holding is usually carried out by evaporating to dryness by heating in a state of standing in the atmosphere, but after appropriately evaporating the water, spray drying, vacuum drying, freeze drying, etc. These means can also be used. Further, the drying atmosphere can be performed in a nitrogen atmosphere or the like.
In this step, the OH group of PVA and the COOH group of hydroxycarboxylic acid are bonded through a dehydration condensation reaction to promote gelation.

h) Step: Step of heating the gel generated in step g) to produce a composite metal oxide precursor The gelled product (metal complex) of the metal thus obtained and hydroxycarboxylic acid and / or PVA The organic component is then thermally decomposed and removed by heating to obtain a composite metal oxide precursor. The thermal decomposition temperature at this time is 250 to 550 ° C., preferably 400 to 500 ° C., although it depends on the type of the target composite metal oxide. If the thermal decomposition temperature is less than 250 ° C, the organic component of the gelled product may not be thermally decomposed, and if it exceeds 500 ° C, the grain growth may proceed abnormally, or the constituent components of the composite metal oxide may evaporate. There is a possibility that a desired composite metal oxide cannot be obtained.

i) Step: Step of heat-treating the composite metal oxide precursor obtained in step h) The composite metal oxide precursor thus obtained is subjected to heat treatment until a desired particle size is obtained. The heat treatment temperature and treatment time are usually 600 to 1400 ° C., preferably 700 to 1200 ° C., depending on the type of the composite metal oxide. The treatment time is usually 0.5 hours to 12 hours, preferably 2 to 6 hours. It is also a preferable method to perform heat treatment a plurality of times while changing the temperature. For example, heating at 450 to 700 ° C., particularly 600 ° C. for a predetermined time, followed by heating at 700 to 1400 ° C., for example, 1100 ° C. for a predetermined time, is a preferable method in terms of improving crystallinity.

  The thermal decomposition step for obtaining the composite metal oxide precursor and the heat treatment step for obtaining the composite metal oxide from the composite metal oxide precursor may be performed continuously, but the organic compound contained in the thermal decomposition step Therefore, the pyrolysis process is preferably a separate process from the subsequent heat treatment process.

In such a method for producing a composite metal oxide of the present invention, since a uniform gelled product (metal complex) is preliminarily formed in a state where each metal ion is uniformly dispersed in a liquid phase, By low-temperature heat treatment, it is possible to form a single-phase composite metal oxide having a uniform chemical composition with excellent crystallinity, and to obtain an ultrafine composite metal oxide having a particle size of 1 μm or less. it can. The firing atmosphere is preferably in the air, but is not necessarily in the air, and may be performed in a neutral atmosphere (inert gas atmosphere) or a reducing atmosphere as necessary. As the neutral or reducing firing atmosphere, for example, an N ₂ , Ar, H ₂ , CO atmosphere or a mixed gas atmosphere thereof is preferable.

  The present invention may further include a microwave irradiation step, and the microwave irradiation step is preferably performed between the aforementioned h) precursor generation step and i) heat treatment step, or i) heat treatment step. By providing it later, the aggregated particles can be dispersed.

  Specifically, this microwave irradiation step is performed by performing heat treatment by microwave irradiation in a state where the composite metal oxide precursor or the composite metal oxide is dispersed in a solvent in a pressure resistant container.

  The treatment temperature of microwave irradiation is usually 100 ° C. or higher, preferably 130 ° C. or higher, more preferably 150 ° C. or higher. The upper limit of the treatment temperature is not particularly limited, but a temperature of 300 ° C. or lower is usually used because a pressure vessel that can withstand high pressure is required.

  The microwave power to be applied is not particularly limited, but is adjusted so that the necessary temperature can be maintained while monitoring the internal temperature of the container. Also, the processing time is not particularly limited, but is usually 5 minutes or longer and 60 minutes or shorter.

  The microwave irradiation process may be a multi-stage process at different temperatures and different electric powers.

  The microwave irradiation process may be performed on the composite metal oxide precursor, the precursor may be performed once after firing, or may be further fired after the treatment.

Although there is no restriction | limiting in particular in the solvent used at a microwave irradiation process, Usually, water is used. Further, ions other than the metal elements constituting the composite metal oxide may be added to the solvent, and the composite metal oxide is added by adding an additive that improves the material properties of the obtained composite metal oxide to the solvent. A part of the product can also be contained. In this case, the additive may be one or more of alkali metal hydroxides such as KOH, NaOH and LiOH, or alkaline earth metal hydroxides such as Ba (OH) ₂ and Sr (OH) _2. Usually, it is used at a concentration of about 0.1 to 5M. By adjusting the concentration of the additive in the solvent, the amount of additive introduced into the obtained composite metal oxide can be limited.

  In addition, the composite metal oxide obtained by the production method of the present invention is subjected to a dispersion treatment with a bead mill or the like when the surface modification of a desired composition is performed according to the purpose of use or application, and then the above-described micro metal oxide. It is also possible to obtain fine particles having a composite function by repeating the wave irradiation step and then performing firing to perform surface modification.

  The composite metal oxide produced by the production method of the present invention can be used for various applications such as a magnetic substance, a dielectric, a phosphor, a photocatalyst, a conductor, and a filter pigment. In some cases, it can be used for cathode ray tubes, FEDs, PDPs, solid state lighting devices, solid state lighting fixtures, fluorescent lamps, backlight fluorescent lamps, fluorescent display tubes, luminous paints, X-ray intensifying screens, and the like.

[Production of composite metal oxide phosphor]
A representative example of the composite metal oxide produced in the present invention is a composite metal oxide phosphor.

The composition of the composite metal oxide phosphor to be produced is not particularly limited, but a metal oxide typified by YVO _{4 as} a crystal matrix is Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb. A combination of ions of rare earth metals or alkaline earth metal elements such as Dy, Ho, Er, Tm, and Yb or ions of metals such as Mn, Sb, and Bi as activators or coactivators is preferable. In the case of a material that emits light without adding an activator or a coactivator, a material synthesized without adding them is also useful.

  As described above, the method for producing a composite metal oxide of the present invention is a composite metal oxide containing at least one selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W, and Bi. Since the method of the present invention is effective for production, the method of the present invention is a composite metal oxidation comprising a crystal matrix containing at least one selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W and Bi. This is effective for the production of phosphors.

The composite metal oxide phosphor produced in the present invention is preferably represented by any one of the following composition formulas [1] to [3], particularly by the following composition formula [4].
(Ln _1-x R _x ) M ¹ O ₄ ... [1]
(E _1-x R _x ) M ² O ₃ ... [2]
(E _1-x R _x ) M ³ O ₄ ... [3]
(In the composition formulas [1] to [3], Ln is at least one element selected from the group consisting of Sc, Y, La, Gd and Lu, and E is selected from the group consisting of Mg, Ca, Sr and Ba. At least one element, M ¹ is at least one element selected from the group consisting of Nb, V and Ta, M ² is at least one element selected from the group consisting of Ti, Zr and Hf, and M ³ is Mo And at least one element selected from the group consisting of W, R is at least selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Mn, Sb and Bi. Represents one element, and x is a number satisfying 0 ≦ x ≦ 0.5.)
^{_{(Ln 1-x R x)}} (Nb 1-y M 1 y) O 4 ······ [4]
(In composition formula [4], Ln, M ¹ , R, and x have the same meaning as in composition formula [1], and y is a number that satisfies 0 ≦ y ≦ 0.5.)

Particularly preferable examples of the crystal matrix of the composite metal oxide phosphor produced in the present invention include, for example, LnNbO ₄ , LnVO ₄ , Ln (V, P) O ₄ , LnTaO ₄ (Ln is Sc, Y, La , Gd, niobates such as representing one or more) selected from Lu, vanadate, phosphate vanadate _{tantalate, ETiO 3, EZrO 3, EHfO} 3, E 2 TiO 4 (E is, Mg , Representing one or more selected from Ca, Sr, and Ba), zirconates, hafnates, tungstates such as EWO ₄ and EMoO ₄ , and molybdates.

  However, the elemental composition of the crystal matrix and the activator or coactivator is not particularly limited, and can be partially replaced with a similar element or an element having a close ionic radius. Any material that emits visible light by excitation by X-rays or absorption of light in the X-ray and ultraviolet to visible regions can be used.

In particular, according to the production method of the present invention, a red phosphor having particularly excellent characteristics can be obtained using Eu ³⁺ as an activator and YNbO ₄ as a crystal matrix. In order to produce this phosphor, the ratio of the total molar amount of Y and Eu to the molar amount of Nb is preferably 1. As for the ratio of Y and Eu, the ratio of Eu to the total molar amount of Y and Eu is preferably 0.05 to 0.5. Even if the ratio of Eu increases, the emission intensity does not decrease so much. However, if Eu is large, the cost of raw materials increases. It is preferable that the Eu ratio is 0.1 to 0.2 because the emission intensity is the highest.

  For this phosphor, an alkali metal element, for example, one or both selected from Li and Na is included in the phosphor so that the phosphor is added to the mixed solution at the time of precursor synthesis in step g) The light emission intensity of can be increased. Among alkali metal elements, it is particularly preferable to add Li. The addition amount of these is preferably 0.01 mol% or more, more preferably 0.03 mol% or more, and more preferably 0.3 mol% or less per mol of the phosphor before the addition thereof. Preferably, it is 0.1 mol% or less. The emission intensity of the phosphor can also be increased by adding one or both of Tb and Pr. The amount added is preferably 10 ppm or more, more preferably 20 ppm or more, more preferably 500 ppm or less, and 200 ppm or less with respect to the mass of the phosphor before the addition. Is more preferable. Further, it is preferable to add both an alkali metal and “one or both of Tb and Pr”, so that the effect of improving both emission intensities appears and the emission intensity is further increased. In any of the additives, an impurity phase is formed when the addition amount is too large, and when the addition amount is too small, the effect of addition cannot be sufficiently obtained.

  These elements can be added as a simple compound such as hydroxide, nitrate, chloride, oxide, acetate, carbonate, sulfate, fluoride, or an aqueous solution thereof.

[Suitable particle size of composite metal oxide]
As a result of intensive studies, the present inventors have studied that a phosphor having a primary particle size defined as a region surrounded by a grain boundary or a surface made of a single crystal is in a range of 0.05 μm to 5 μm (easily dispersed to primary particles). Possible forms) form a uniform and dense high-intensity fluorescent film and fluorescent layer when applied to cathode ray tubes, FEDs, PDPs, solid state lighting elements, fluorescent lamps, fluorescent display tubes, luminous paints, X-ray intensifying screens, etc. I found out that I can do it. Further, it has been found that by using the phosphor of the present invention as a fluorescent bead for radioimmunoassay used for drug development, a high-throughput new drug screening system with higher development efficiency than before can be obtained.

  A primary particle is a region made of a single crystal and surrounded by a grain boundary or surface, and is defined as a region in which the crystal orientation is essentially the same in that region. That is, the primary particle in the present invention represents a crystal region in which the entire region shows a single X-ray reflection in single crystal X-ray diffraction. However, in such a crystal region, not all crystals are perfectly aligned in the exact same direction, and crystal strain is inherent or includes crystal defects. It is possible that different unit cells form a mosaic structure and the crystal orientation is slightly shifted.

  In the present invention, the primary particle size is the particle size of the primary particles, for 10 particles arbitrarily selected from a scanning electron microscope (SEM) photograph, the average value of the maximum diameter and the minimum diameter of each particle, The average value was taken as the primary particle size.

  When the primary particle size is smaller than 0.05 μm, desired high brightness cannot be obtained, and handling of particles becomes difficult in a process such as a coating film, so that a homogeneous and dense fluorescent film or fluorescent layer cannot be formed. On the other hand, when the primary particle size is larger than 5 μm, high-definition fluorescence is used when used for cathode ray tubes, FEDs, PDPs, solid state lighting devices, solid state lighting fixtures, fluorescent lamps, fluorescent display tubes, luminous paints, X-ray intensifying screens, etc. When a membrane cannot be formed and used as a fluorescent bead for radioimmunoassay used in drug development, the sedimentation of the fluorescent substance in the fluorescent bead slurry for dispensing takes place in a short time. Measurement of the fluorescence intensity becomes impossible. The primary particle size is particularly preferably 1 μm or more and 3 μm or less.

  Accordingly, in the present invention, particularly when the composite metal oxide to be produced is a phosphor, for example, the firing temperature and the firing time are adjusted so that a composite metal oxide having a primary particle size in the above range is obtained. It is preferable to do.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example, unless the summary is exceeded.

<Examples 1-5>
A synthesis flowchart of (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ by the PVA method in Examples 1 to 5 is shown in FIG.

The NbCl ₅ of 0.837g were dissolved in aqueous hydrogen peroxide (concentration 30 wt%) 15 ml aqueous ammonia (concentration 28 wt%) 5 ml, a precipitate formed of Peruokisoniobu compounds by the addition of ethanol 20 ml. Chlorine was removed by filtering this precipitate. The total amount of the filtered precipitate was dissolved in 10 ml of an aqueous glycolic acid solution (concentration 0.114% by weight), and the concentration of Nb in the solution was determined by ICP (inductively coupled plasma) spectroscopy. Weighed "Nb- glycolic acid complex" aqueous _{Eu (NO 3) 3 · 6H} 2 O and 0.335g and PVA aqueous solution (# 500 (polymerization degree 500, saponification degree 86.5 to 89 mol%, concentration 12.5 the weight%)) 8 ml, aqueous acetic acid (concentration 99.7 wt%) _Y was dissolved in 2 ml 2 _{(CO 3)} was added 0.837g of 3 · 2H ₂ O, polymer by performing stirring concentrated 250 ° C. A gel was obtained. The ratio of Nb, Y, and Eu was 1: 0.85: 0.15.

In order to decompose the organic matter, it was heated with a mantle heater set at 450 ° C. to obtain a composite metal oxide precursor. The precursors were heated in an electric furnace at 1000 ° C. (Example 1), 1100 ° C. (Example 2), 1200 ° C. (Example 3), 1300 ° C. (Example 4), and 1400 ° C. (Example 5). The (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ phosphors of Examples 1 to 5 were synthesized by heat treatment for 5 hours (hereinafter referred to as “final heat treatment”).

  The emission / excitation spectrum of the phosphor of Example 2 (final heat treatment temperature 1100 ° C.) is shown in FIG. 2, the powder X-ray diffraction pattern is shown in FIG. 3, and the SEM photograph is shown in FIG.

<Comparative Example 1>
First, Nb ₂ O ₅ .nH ₂ O was heated at 900 ° C. for 2 hours to obtain anhydrous Nb ₂ O ₅ . Anhydrous Nb ₂ O ₅ , Y ₂ O ₃ and Eu ₂ O ₃ were mixed well using a planetary ball mill and heat-treated in an electric furnace at 1200 ° C. for 5 hours to obtain (Y _0.85 , Eu ³⁺ of Comparative Example 1). _0.15 ) NbO ₄ phosphor was synthesized.

<Comparative example 2>
A synthesis flowchart of (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ by the complex polymerization method in Comparative Example 2 is shown in FIG.

NbCl ₅ was dissolved in methanol, citric acid, Y ₂ (CO ₃ ) ₃ · 2H ₂ O, propylene glycol, Eu (NO ₃ ) ₃ · 6H ₂ O was added, and the mixture was stirred at 80 ° C. Next, the polymer gel was obtained by performing heat concentration at 200 degreeC. In order to decompose the organic matter, it was heated to 450 ° C. with a mantle heater to obtain a composite metal oxide precursor. The precursor was heated in an electric furnace at 1300 ° C. for 5 hours to synthesize a (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ phosphor of Comparative Example 2.

<Example 6>
In Example 2, the same procedure as in Example 2 except that an intermediate heat treatment was performed at 600 ° C. between the step of heating at 450 ° C. to obtain the composite metal oxide precursor and the step of final heat treatment at 1100 ° C. (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ phosphor of Example 6 was synthesized.

<Examples 7 to 9>
In Example 2, intermediate heat treatment to 600 ° C. and heat treatment by microwave irradiation were performed between the step of obtaining a composite metal oxide precursor by heating at 450 ° C. and the step of final heat treatment at 1100 ° C. (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ phosphors of Examples 7 to 9 were synthesized by performing the same procedure as in Example 2 except for the above.

In the heat treatment by microwave irradiation, the phosphor precursor subjected to 600 ° C. intermediate heat treatment is put in water (Example 7), 1M KOH aqueous solution (Example 8), 1M LiOH aqueous solution (Example 9), and Co., Ltd. Using the “MWS-2 type microwave decomposing apparatus” manufactured by Actac, the following processing procedure (step 1 → step 2 → step 3) was performed. The phosphor after the treatment was subjected to solid-liquid separation by filtration, and then subjected to a final heat treatment at 1100 ° C. for 5 hours in the same manner as in Example 2, and (Y _0.85 , Eu ^{3+ of} Examples 7 to 9 respectively). It was obtained _0.15) NbO ₄ phosphor.

(Processing procedure of microwave heating process (output 100% = 1000 W))
Process 1: Temperature 150 ° C, time 10 minutes, output 80%
Process 2: Temperature 200 ° C, time 20 minutes, output 80%
Process 3: Natural cooling under sealing

<Examples 10 to 20>
“Nb-glycolic acid complex” solution, Eu (NO ₃ ) ₃ .6H ₂ O, PVA aqueous solution (same as used in Example 2), Y ₂ (CO ₃ ) ₃ · 2H dissolved in acetic acid aqueous solution _{In addition to 2} O, either LiOH and / or Tb (NO ₃ ) ₃ or both were added in the same manner as in Example 2 except that a predetermined amount was added, and Li and / or Tb addition in Examples 10 to 20 ( Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ phosphor was obtained. In addition, LiOH and Tb (NO ₃ ) ₃ are added at such a ratio that the addition ratio with respect to 1 mol of the synthesized (Y _0.85 , Eu ³⁺ _0.15 ) NbO ₄ phosphor becomes the value shown in Table 1. did.

  The emission spectrum and SEM photograph of the phosphor of Example 20 are shown in FIGS. 6 and 7, and the powder X-ray diffraction patterns of the phosphors of Examples 15 to 20 are shown in FIG.

  Regarding Examples 1 to 20 and Comparative Examples 1 and 2, the characteristics of the treatment procedure and the characteristics of the obtained phosphors (the peak height of the emission spectrum, the relative value of the integrated intensity at wavelengths of 580 to 640 nm, the primary particle size) Are summarized in Table 1.

  The emission spectrum, the relative value of the integrated intensity at a wavelength of 580 to 640 nm, and the primary particle size were obtained as follows.

(Emission spectrum)
Using a spectrofluorometer F-4500 manufactured by Hitachi, measurement was performed under the conditions of light source: xenon lamp, excitation light: 1.0 nm, and fluorescent slit: 1.0 nm. The excitation wavelength when measuring the fluorescence spectrum was 250 nm, and the fluorescence wavelength when measuring the excitation spectrum was 612 nm.

(Relative value of integrated intensity at a wavelength of 580 to 640 nm)
In the fluorescence spectrum measured under the measurement conditions of the emission spectrum, the sum of intensity values every 0.2 nm in the range of 580 to 640 nm was determined, and the value of the standard phosphor (Y, Eu) VO ₄ obtained by the solid phase method The relative value with 100% was taken as the integrated intensity.

(Primary particle size)
For 10 particles arbitrarily selected from a scanning electron microscope (SEM) photograph, the average value of the maximum diameter and the minimum diameter of each particle was determined, and the average value was calculated to obtain the primary particle size.

  From Table 1, it can be seen that according to the present invention, a phosphor having a small particle size and high emission intensity can be obtained.

  For Example 2 and Comparative Example 2, the amount of organic compound contained in the precursor necessary for synthesizing phosphor 1g is shown in Table 2.

  As is clear from Table 2, it can be seen that the PVA method using glycolic acid, which is a hydroxycarboxylic acid, is a method with less environmental burden and a smaller amount of organic compound that is removed by heating than the complex polymerization method.

It is a synthesis | combination flowchart of the fluorescent substance by the PVA method of Examples 1-5. 4 is an emission / excitation spectrum of the phosphor obtained in Example 2. 3 is a powder X-ray diffraction pattern of the phosphor obtained in Example 2. FIG. 3 is a SEM photograph of the phosphor obtained in Example 2. 5 is a synthesis flowchart of a phosphor by a complex polymerization method of Comparative Example 2. 7 is an emission spectrum of the phosphor obtained in Example 20. 4 is a SEM photograph of the phosphor obtained in Example 20. It is a powder X-ray-diffraction pattern of the fluorescent substance obtained in Examples 15-20.

Claims (10)

  In the method for producing a composite metal oxide by a liquid phase method using an organic compound, the organic compound is used in an amount of 0.1 to 10 parts by weight with respect to 1 part by weight of the produced composite metal oxide. A method for producing a composite metal oxide characterized by the above. The method for producing a composite metal oxide according to claim 1, comprising the following steps.
a) Step of dissolving at least one metal element compound and polyvinyl alcohol in a solvent and reacting both to form a metal complex b) Step of gelling by removing the solvent from the liquid produced by the metal complex c) Step of generating a composite metal oxide precursor by heating the generated gel d) Step of heat-treating the composite metal oxide precursor The method for producing a composite metal oxide according to claim 1, comprising the following steps.
e) In water, a compound of at least one metal element selected from the group consisting of Nb, V, Ta, Ti, Zr, Hf, Mo, W and Bi (hereinafter referred to as “first metal element”), and hydroxy A step of preparing a hydroxycarboxylic acid complex aqueous solution of the first metal element by reacting with a carboxylic acid; f) at least one different from the first metal element in the hydroxycarboxylic acid complex aqueous solution of the first metal element; A step of adding a compound of a seed metal element and polyvinyl alcohol to obtain a mixed solution; g) a step of removing water from the mixed solution to form a gel; h) a composite metal oxide precursor by heating the formed gel; Step i) Step of heat-treating the composite metal oxide precursor   The method for producing a composite metal oxide according to any one of claims 1 to 3, further comprising a microwave irradiation step on the composite metal oxide precursor or the heat-treated product thereof.   5. The method for producing a composite metal oxide according to claim 1, wherein the resulting composite metal oxide has a primary particle size of 0.05 μm or more and 5 μm or less.   The obtained composite metal oxide includes a rare earth element or an alkaline earth element and at least one metal element selected from Nb, V, Ta, Ti, Zr, Hf, Mo, W and Bi. The method for producing a composite metal oxide according to any one of claims 1 to 5, wherein the method is a phosphor. The method for producing a composite metal oxide according to claim 6, wherein the obtained composite metal oxide phosphor is represented by any of the following composition formulas [1] to [3].
(Ln _1-x R _x ) M ¹ O ₄ ... [1]
(E _1-x R _x ) M ² O ₃ ... [2]
(E _1-x R _x ) M ³ O ₄ ... [3]
(In the composition formulas [1] to [3], Ln is at least one element selected from the group consisting of Sc, Y, La, Gd and Lu, and E is selected from the group consisting of Mg, Ca, Sr and Ba. at least one element, ^{M 1} is Nb, at least one element selected from the group consisting of V and Ta, ^{M 2} is Ti, at least one element selected from the group consisting of Zr and Hf, ^{M 3} is Mo And at least one element selected from the group consisting of W, R is at least selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Mn, Sb and Bi. Represents one element, and x is a number satisfying 0 ≦ x ≦ 0.5.) The method for producing a composite metal oxide according to claim 7, wherein the obtained composite metal oxide phosphor is represented by the following composition formula [4].
^{_{(Ln 1-x R x)}} (Nb 1-y M 1 y) O 4 ······ [4]
(In composition formula [4], Ln, M ¹ , R, and x have the same meaning as in composition formula [1], and y is a number that satisfies 0 ≦ y ≦ 0.5.)   The method for producing a composite metal oxide according to any one of claims 1 to 8, further comprising a step of adding an alkali metal to the reaction system.   The method for producing a composite metal oxide according to any one of claims 1 to 9, further comprising a step of adding Tb and / or Pr to the reaction system.

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