JP2002187717A - Rare earth element compound, rare earth element oxide, phosphor and method for manufacturing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide single-phase spheric powder of rare earth element salt having 2 to 10 μm average particle size which is suitable as a source material of a phosphor and having an extremely small proportion of fine particles of <=1 μm size mixed which are not preferable as the source material of the phosphor, to provide powder of rare earth element oxide obtained by calcining the above powder of rare earth salt, to provide a method for easily manufacturing the rare earth salt powder and rare earth oxide powder, and to provide a phosphor using the above powder and a method for manufacturing the phosphor. SOLUTION: The spheric powder of rare earth element salt has the chemical composition expressed by X2(CO3)a(SO4)b(OH)c.nH2O and <=20% proportion of particles having 1 μm or smaller particle size in the whole particles. The rare earth oxide powder is obtained by calcining the powder of the rare earth element salt at 1,100 to 1,600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spherical rare earth element salt powder having a particle diameter and shape useful as a raw material for a phosphor, and having a very small amount of fine particles of 1 μm or less, which are undesirable as a raw material for a phosphor. The present invention relates to a rare earth element oxide powder obtained by calcining the rare earth element salt powder, a phosphor using the same, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, phosphors have been produced by mixing and sintering a raw material powder and a flux, followed by pulverization and classification (for example, JP-A-55-161882, JP-B-45-22).
413, JP-A-53-25840, etc.), but in such a production method, the flux component remains on the particle surface as surface impurities, or the particle surface is mechanically damaged during the pulverization process. Was receiving. In addition, mixing of impurities during the pulverizing step was inevitable.

In recent years, displays such as a field emission display (FED) and a plasma display (PDP) have attracted attention. Since the FED uses a low-speed electron beam and the PDP uses a vacuum ultraviolet ray as an excitation source, excitation is performed only on the very surface of the phosphor. In these applications, characteristics higher than those of the conventional phosphor are required. Specific examples include low mixing of fine powder, suitable particle diameter and shape, and excellent surface light emission characteristics.

[0004] For this reason, in FED applications and PDP applications, it is important to produce a phosphor without using a flux and without pulverization. One solution is to synthesize a phosphor precursor in a solution. Then, there is a method of firing with no flux while keeping the shape.

In this case, as a method of synthesizing a precursor, for example, Japanese Patent Application Laid-Open No. Hei 6-271316 discloses a method in which an yttrium salt is heated in an acidic aqueous solution containing a yttrium salt, a europium salt and urea at a pH of 3 or less until the pH reaches 7 or more. A method for obtaining a coprecipitate containing europium has been proposed. However, the particles obtained by this method have an average particle size of 1 μm or less, which is too small when used as a phosphor raw material, and a method of obtaining larger particles has been desired.

[0006] Also, Japanese Patent Application Laid-Open No. 7-97211,
After heating in the coexistence of a small amount of 0.01 to 0.2 mol of sulfate ion and 5 to 50 mol of urea per 1 mol of rare earth element, the mixture is calcined at 700 to 900 ° C. so that the average particle size is 2 mol.
A method for obtaining a spherical rare earth element oxide of 10 to 10 μm has been proposed. However, in this method, although the average particle diameter of the obtained particles is increased, the particles do not always have a satisfactory particle size distribution and shape, such as a large number of fine particles of 1 μm or less and coarse particles composed of aggregates thereof. .

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the problems of the prior art, and has an average particle diameter of 2 to 10 μm suitable for a phosphor material and 1 μm or less which is not preferable for a phosphor material. Of rare-earth element salt powder in a single phase and spherical, rare-earth element oxide powder obtained by baking this rare-earth element salt powder, and rare-earth element salt powder and rare-earth element oxide powder Another object of the present invention is to provide a phosphor which has the above-mentioned particle properties and has excellent emission characteristics on the surface of the particles, and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have solved such problems.
Rare earths that have characteristics suitable for phosphor materials
When producing elemental oxide powder, sulfate ions must be
Various conditions were examined by the urea method. As a result, certain
In an aqueous solution containing sulfate ions and salts of rare earth elements in a ratio,
Add urea, heat and add carbonate, sulfate and water.
Precipitated as double salt of rare earth element with oxide ion
That the chemical composition is X_Two(CO_Three) _a(SO_Four)
_b(OH)_C・ NH_TwoO (where X is Y, La, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
selected from the group consisting of o, Er, Tm, Yb and Lu
Is a single element or a mixture of two or more elements, wherein a is
A real number satisfying 0.7 <a <1.5, and b is 0.3 <b <1.
3, a real number satisfying c = 6-2a-2b,
n is a real number satisfying 0 ≦ n <6. ), Average
The particle size is 2 to 10 μm suitable as a phosphor material,
Of fine particles of 1 μm or less
Extremely low spherical content of 20% or less based on the total number of particles
It has been found that particles can be obtained. Furthermore, this deposited
By firing the double salt at a temperature of 1100 to 1600 ° C,
Spherical, while maintaining the shape of the precipitated double salt,
Chemical composition X_TwoO_ThreeIs obtained.
I found that. Further phosphors produced from them
Excites only extreme surfaces such as slow electron beams and vacuum ultraviolet rays.
Excellent emission characteristics for no excitation source
And finally completed the present invention.

Hereinafter, the present invention will be described in detail. <Rare earth element salt powder> The rare earth element salt powder of the present invention (hereinafter referred to as “the salt powder of the present invention”) has a chemical composition of X
₂ (CO ₃ ) _a (SO ₄ ) _b (OH) _C · nH ₂ O (where X is
Is Y, La, Ce, Pr, Nd, Pm, Sm, Eu, G
d is a single element selected from the group consisting of Tb, Dy, Ho, Er, Tm, Yb, and Lu or a mixture of two or more elements, and a is a real number satisfying 0.7 <a <1.5. , B is a real number satisfying 0.3 <b <1.3, and c is c = 6-2a-2.
A real number satisfying b, n is a real number satisfying 0 ≦ n <6. )
The ratio of the number of particles having a particle diameter of 1 μm or less to the total number of particles is 20% or less, and the powder is a spherical rare earth element oxide powder.

Here, the chemical composition of the salt powder of the present invention is X ₂ (CO ₃ ) _a (SO ₄ ) _b (OH) _6-2a-2b · nH ₂
O. In the chemical composition formula, X is a rare earth element commonly used as a phosphor material, and specifically, Y, La, C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb, and Lu. Among these, Y, Eu, and Gd are preferable, but are not limited to these depending on the use of the powder of the present invention, and may be any of the elements listed here.
The species may be used alone, or may be a mixture of elements obtained by combining two or more arbitrary elements.

In the above composition formula, a, b, c
Is a coefficient indicating the composition of carbonate ion, sulfate ion, and hydroxide ion, respectively, a is a real number satisfying 0.7 <a <1.5, and b is 0.3 <b <1.3. And c is a real number satisfying c = 6-2a-2b. When the composition of these ions satisfies the relationship of a, b, and c, the powder of the present invention exhibits preferable physical properties as a raw material for a phosphor. Similarly, n is a water content, and is preferably a real number satisfying 0 ≦ n <6. The coefficients indicating these compositions can be determined by, for example, thermal analysis, generated gas analysis, or ICP analysis, as described in Examples in this specification.

The particles constituting the salt powder of the present invention have an average particle size of 2 to 10 μm suitable as a raw material for a phosphor, and the amount of particles having a particle size of 1 μm or less which is not preferable as a raw material for a phosphor is reduced. Is 2 for the total number of particles
0% or less. If this ratio exceeds 20%,
In some cases, problems may occur in terms of application as a phosphor raw material.
The particle distribution can be determined, for example, by a commonly used particle size distribution measuring device.

The salt powder of the present invention is a powder having the above-mentioned composition, and is not substantially a mixture.

The salt powder of the present invention has a spherical shape suitable as a raw material for a phosphor. This shape can be confirmed by, for example, an electron microscope image as described in Examples of the present specification. Further, depending on the purpose, these can be image-processed and quantified to an appropriate range. <Method for producing rare earth element salt powder> Next, a method for producing the salt powder of the present invention will be described.

The method for producing a salt powder according to the present invention is characterized in that urea is added to an aqueous solution containing a sulfate ion and a salt of a rare earth element and having a sulfate ion concentration of 0.2 to 5 moles per mole of the rare earth element, followed by heating. , A precipitation step of precipitating a double salt of a rare earth element having a carbonate ion, a sulfate ion and a hydroxide ion. Each step will be described below.

<Precipitation Step> In the precipitation step, urea is added to an aqueous solution containing a sulfate ion and a salt of a rare earth element, and heated to form a double salt of a rare earth element having a carbonate ion, a sulfate ion and a hydroxide ion. Precipitate.

As the salts of rare earth elements used in the method of the present invention, chlorides, nitrates, acetates, sulfates, and the like can be used. Is possible, but
In the case where metal ions are not to be mixed into the product, sulfuric acid or ammonium sulfate is preferably used.

The concentration of the rare earth element salt in the aqueous solution containing the sulfate ion and the rare earth element salt is 0.01 to 0.5.
A range of 5 mol / l is preferred. Deviating from this range, the concentration of the rare earth element salt in the aqueous solution may be 0.01 mol / mol.
If it is less than 1 liter, productivity may be significantly poor,
If it is more than 0.5 mol / l, agglomeration of particles may occur during precipitation.

Regarding the amount of sulfate ions, it is preferable that 0.2 to 5 moles of sulfate ions per mole of rare earth element be present in the aqueous solution. If the amount of sulfate ion is less than 0.2 mol per mol of the rare earth element, many particles of 1 μm or less are contained.

Further, the amount of urea added to the aqueous solution is preferably 2 to 50 mol per 1 mol of the rare earth element. If the amount of urea deviates from this range, if the amount of urea is less than 2 moles per 1 mole of rare earth element, a sufficient amount of precipitates may not be obtained. If the amount exceeds 50 moles, the cost of urea increases and the economic efficiency deteriorates. Become.

The aqueous solution containing the sulfate ion and the salt of the rare earth element is heated by adding urea. The heating temperature is preferably 60 ° C. or higher in order to avoid a reduction in the reaction rate. In addition, the reaction time is not constant depending on the heating temperature and the concentration of the raw material and cannot be unconditionally determined, but may be appropriately determined within a few minutes to a few days.

By this heating, urea is hydrolyzed to release a gas such as ammonia or carbon dioxide gas. As a result, a double salt of a rare earth element having carbonate ion, sulfate ion and hydroxide ion is precipitated. The deposited precipitate is filtered off by a known method and further washed with water.

Thus, the salt powder of the present invention is obtained.
The salt powder of the present invention is used as a raw material of a rare earth element oxide powder or a raw material of a phosphor described below, but can be used for other purposes if necessary. <Rare earth element oxide powder> Next, the rare earth element oxide powder (hereinafter referred to as "the oxide powder of the present invention") will be described.

The above-mentioned salt powder of the present invention is further calcined,
A rare earth oxide powder is obtained.

The chemical composition of the oxide powder of the present invention is X ₂ O
₃ (where X is Y, La, Ce, Pr, Nd, Pm, S
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb
And Lu or a mixture of two or more elements selected from the group consisting of Lu. ), Spherical,
The shape of the salt powder of the present invention is maintained. For this reason, it has extremely useful characteristics as a phosphor raw material.

Here, in the chemical composition formula of the oxide powder of the present invention, X is a rare earth element commonly used as a phosphor material, and specifically, Y, La, Ce, Pr, Nd, Pm,
Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, Lu. Of these, Y, Eu, Gd
However, depending on the use of the powder of the present invention, the powder is not limited thereto, and may be any of the elements listed here, and these elements may be used alone.
A mixture of elements obtained by combining two or more arbitrary elements may be used. These compositions can be determined using a known method.

The particles constituting the oxide powder of the present invention have the same properties as the above-mentioned salt powder of the present invention.

The oxide powder of the present invention is a powder having the above-mentioned composition, and is not substantially a mixture. Whether the powder is in a single phase or not can be confirmed by, for example, a commonly used powder X-ray diffractometer.

The oxide powder of the present invention has a spherical shape suitable as a phosphor material. This shape can be confirmed by, for example, an electron microscope image. Further, depending on the purpose, these can be image-processed and quantified to an appropriate range. <Method for producing rare earth element oxide powder> Next, a method for producing the oxide powder of the present invention will be described.

The method for producing an oxide powder of the present invention comprises a firing step of firing the above-described salt powder of the present invention,
This will be described below.

<Firing Step> In the firing step, the salt powder of the present invention, which is a double salt of a rare earth element obtained in the above-mentioned precipitation step, and if necessary, a rare earth element compound, are added.
By baking at a temperature of 0 to 1600 ° C., a spherical rare earth oxide powder is obtained.

The firing temperature is 1100-1600 ° C.
And more preferably 1300 to 1600 ° C. When the calcination temperature is out of this range and lower than 1100 ° C., the resulting rare earth element double salt does not become a single phase, but becomes 1 phase.
If the temperature exceeds 600 ° C., energy costs are increased and the load on the apparatus is increased, and the shape of the powder particles obtained by sintering is not spherical, which is not preferable. The firing time is not constant than the firing temperature and cannot be unconditionally determined, but may be determined as appropriate within a few minutes to a few days. Furthermore, the heating device and the like used for firing are not particularly limited, and a known device can be used.

The raw material to be subjected to the calcination step may be the salt powder of the present invention alone, but a rare earth element compound other than the rare earth element constituting the salt powder of the present invention or a rare earth element compound of the same type is added and mixed. It can also be obtained by baking later. The kind of these rare earth element compounds may be appropriately determined in consideration of the chemical composition of the finally obtained rare earth oxide powder and the like.

More specifically, for example, when finally obtaining a material having only Y as a rare earth element, a salt powder of the present invention containing only Y as a rare earth element is obtained, and this is used as it is or as a rare earth element. What is necessary is just to bake after mixing with the rare earth compound which consists only of Y as an element. Further, when obtaining a material having Y and Eu as rare earth elements,
The present invention can be obtained by obtaining a salt powder of the present invention composed of Y or Eu alone or both as a rare earth element, mixing with the corresponding rare earth element or a rare earth compound composed of both as the rare earth element, and firing.

The oxide powder of the present invention is extremely useful as a raw material for a phosphor due to its excellent properties.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, each evaluation was implemented by the method shown below. <Average particle size> The average particle size was measured by a particle size distribution analyzer (manufactured by Beckman Coulter, Inc.). <Particle Shape> The particle shape was confirmed by scanning electron microscope observation (manufactured by JEOL Ltd.). <Composition of the precipitate> The composition of the precipitate was determined by thermal analysis (manufactured by Rigaku Denki Co., Ltd.)
Confirmed by law. <Powder X-Ray Diffraction> The precipitate is converted to a powder X-ray diffractometer (Mac
MPX3 manufactured by Science Co., Ltd., using an X-ray source of Cu-Kα radiation) to confirm whether the obtained precipitate was a single phase or a mixture. <Method of Determining Composition> FIG. 1 shows a typical thermal analysis result of the double salt of a rare earth element obtained in the present invention. From the results of the thermal analysis, a three-stage weight reduction was observed. Further, from this result and the analysis of the generated gas at the time of temperature increase, in the temperature range of less than 400 ° C., mainly desorption of hydroxide ions and adsorbed water, 400 ° C or higher 8
In the temperature range below 00 ° C., mainly carbonate ion desorption, 800
In the temperature range above ℃, desorption of sulfate ions was mainly observed. Therefore, the composition of the obtained double salt is changed to X ₂ (CO ₃ )
_a (SO ₄ ) _b (OH) _c · nH ₂ O, and coefficients a and b were calculated from the weight loss by thermal analysis. The coefficient c was calculated as c = 6-2a-2b, with the rare earth ion being trivalent. After determining the coefficients a, b, and c, the coefficient n was calculated so as to be compatible with the remaining weight. For the coefficient b, ICP of sulfate ion in double salt
It was also calculated from the results of the quantitative analysis, and it was confirmed that the value was almost equal to the value from the result of the thermal analysis. Thus, double salts of rare earth elements obtained in the following Examples and Comparative Examples were measured, and the respective coefficients a, b, c, and n calculated from the results are shown in Table 2. <Evaluation of Light Emission by Slow Electron Beam Excitation> FIG. 2 schematically shows an apparatus used for evaluation of light emission by slow electron beam excitation. L which is an electron beam source
aB ₆ filament (cathode) 1, Wehnelt cap 2, electron extraction electrode (grid) 3 made of SUS mesh, incidence limiting slit (slit width 5 mm diameter circle) 4, phosphor-coated glass substrate (anode) 5
Is installed in the vacuum chamber 6.

The LaB ₆ filament 1 has a direct current of 2.6 A.
(Described in 7), and 40V is applied to the electron extraction electrode.
Was applied (described in 8). Anode voltage is 865V
(Described in 9). The luminance was measured from the back side of the light emitting surface using a luminance meter (Minolta nt- ／ ° p). <Evaluation of Vacuum Ultraviolet Excitation Emission> A phosphor evaluation device for PDP (146 nm excitation) manufactured by Otsuka Electronics Co., Ltd. was used.

Example 1 57.6 g of urea and 1.58 g of ammonium sulfate were added to 1 liter of a 0.04 mol / liter yttrium chloride aqueous solution, and completely dissolved. This solution was placed in a three-necked round bottom flask equipped with a reflux condenser and a thermometer, heated to 80 ° C. in an oil bath, and kept for 4 hours.
After cooling in a water bath, the mixture was filtered off with a Buchner funnel and washed twice with 300 ml of pure water. Thereafter, the solvent was replaced with 150 ml of ethanol and air-dried. The composition of the obtained precipitate is Y _{2
(CO 3) 1.2 (SO 4} ) 0.6 (OH) was _{2 .4} · 4.2H ₂ O. This precipitate is spherical particles, and the average particle size is 6.
The ratio of the number of particles of 3 μm and 1 μm or less to the total number of particles was 19%.

The obtained precipitate was calcined at 1400 ° C. for 2 hours in the air to obtain 2.7 g of yttrium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase. Further, this oxide was spherical particles, and retained the shape of the precipitate.

Example 2 In addition to changing the addition amount of ammonium sulfate to 2.64 g,
A precipitate was obtained under the same steps and conditions as in Example 1.
The composition of this precipitate is Y_Two(CO_Three)_0.9(SO_Four) _0.6(O
H)_Three・ 0.3H_TwoO. This precipitate is a spherical particle
Yes, average particle size is 8.1 μm, 1 μm based on the total number of particles
The ratio of the number of particles below was 17%. Running of this deposit
A scanning electron micrograph is shown in FIG.

The obtained precipitate was calcined at 1400 ° C. for 2 hours in the air to obtain 2.8 g of yttrium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase. Further, this oxide was spherical particles, and retained the shape of the precipitate.

Example 3 Other than changing the amount of ammonium sulfate to 13.2 g,
A precipitate was obtained under the same steps and conditions as in Example 1.
The composition of this precipitate is Y_Two(CO_Three)_0.9(SO_Four) _1.0(O
H)_2.2・ 1.6H_TwoO. This precipitate is a spherical particle
And the average particle size was 6.0 μm, 1 μm based on the total number of particles.
The ratio of the number of particles of m or less was 7.8%.

The obtained precipitate was calcined in the air at 1400 ° C. for 2 hours to obtain 2.9 g of yttrium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase. Further, this oxide was spherical particles, and retained the shape of the precipitate.

Example 4 Other than changing the addition amount of ammonium sulfate to 26.4 g,
A precipitate was obtained under the same steps and conditions as in Example 1.
The composition of this precipitate is Y_Two(CO_Three)_0.9(SO_Four) _1.1(O
H)_2.0・ 2.3H_TwoO. This precipitate is a spherical particle
And the average particle size was 5.8 μm, 1 μm based on the total number of particles.
The ratio of the number of particles of m or less was 3.2%.

The obtained precipitate was calcined at 1400 ° C. for 2 hours in the air to obtain 2.5 g of yttrium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase. Further, this oxide was spherical particles, and retained the shape of the precipitate.

Example 5 Example 1 except that a 0.002 mol / l aqueous solution of europium chloride was added to an aqueous solution of yttrium chloride.
A precipitate was obtained according to the same steps and conditions as described above. The composition of this precipitate is (Y, Eu) ₂ (CO ₃ ) _0.9 (SO ₄ ) _0.6 (O
H) was _3.0 · 3.4H ₂ O. The precipitate is spherical particles, the average particle size is 6.9 μm, and the average particle size is 1 μm.
The ratio of the number of particles of m or less was 13%.

The obtained precipitate was calcined at 1400 ° C. for 2 hours in the air to obtain 2.9 g of a powder of yttrium / europium composite oxide. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase. Further, this oxide was spherical particles, and retained the shape of the precipitate.

Example 6 Example 1 was repeated except that an aqueous solution of 0.04 mol / l gadolinium chloride was used instead of the aqueous solution of yttrium chloride.
A precipitate was obtained according to the same steps and conditions as described above. The composition of this precipitate is Gd ₂ (CO ₃ ) _1.0 (SO ₄ ) _0.7 (OH) _2.6
3.6H was ₂ O. This precipitate is a spherical particle,
The average particle size was 7.5 μm, and the ratio of the number of particles of 1 μm or less to the total number of particles was 14%.

The obtained precipitate was calcined in the air at 1400 ° C. for 2 hours to obtain 4.8 g of gadolinium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase. Further, this oxide was spherical particles, and retained the shape of the precipitate.

Comparative Example 1 A precipitate was obtained by the same steps and conditions as in Example 1 except that ammonium sulfate was not added. The composition of the precipitate was Y ₂ (CO ₃ ) _2.7 (OH) _0.6 · _0.3 H ₂ O. Although the precipitate was spherical particles, the average particle size was 2.
The ratio of the number of particles of 1 μm or less to the total number of particles was as small as 2 μm and extremely high at 63%.

The obtained precipitate was calcined in the air at 1400 ° C. for 2 hours to obtain 3.7 g of yttrium oxide powder.

Comparative Example 2 A precipitate was obtained by the same steps and conditions as in Example 1 except that the amount of ammonium sulfate added was 0.53 g.
The composition of the precipitate _{Y 2 (CO 3) 2 (} SO 4) 0. 2 (O
H) It was _1.6 · 2.8H ₂ O. Although this precipitate was spherical particles, the average particle size was 3.6 μm, but the ratio of the number of particles of 1 μm or less to the total number of particles was as extremely high as 54%. FIG. 4 shows a scanning electron micrograph of this precipitate.

The obtained precipitate was calcined in the air at 1400 ° C. for 2 hours to obtain 2.6 g of yttrium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase.

Comparative Example 3 In addition to the addition of 39.6 g of ammonium sulfate,
A precipitate was obtained under the same steps and conditions as in Example 1.
The composition of this precipitate is Y_Two(CO_Three)_1.0(SO_Four) _1.1(O
H)_1.8・ 2.7H_TwoO. This precipitate has an average grain size.
The diameter is 4.8 μm, the number of particles less than 1 μm to the total number of particles
Was 0.8%, but not spherical particles. This
FIG. 5 shows a scanning electron micrograph of the precipitate of FIG.

The obtained precipitate was calcined in the air at 1400 ° C. for 2 hours to obtain 2.6 g of yttrium oxide powder. When this powder was measured with a powder X-ray diffractometer, it was confirmed that it was a single phase.

As a result of the above Examples 1 to 6 and Comparative Examples 1 to 3, Table 1 shows that the molar ratio of sulfate ion to 1 mol of the rare earth element in the starting material, the average particle size of the obtained precipitate, The ratio of the number of particles of 1 μm or less to the total number of particles and the particle shape are shown. Table 2 shows numerical values of coefficients a, b, c, and n calculated from the results of thermal analysis and ICP of the obtained precipitates based on the above-described composition determination method. still,
The weight loss in Table 2 is less than 400 ° C,
The amount of weight loss in the temperature range of less than 0 ° C. and 800 ° C. or more, and the remaining weight are shown.

[0057]

[Table 1]

[Table 2] Comparative Example 4 A calcination powder (3.0 g) was obtained by the same process and conditions as in Example 1 except that the calcination temperature was changed to 1000 ° C. This calcined powder is converted into a powder X-ray diffractometer (Mc Science M
PX3 and the X-ray source used were Cu-Kα rays). As a result, it was a mixture of Y ₂ O ₃ and Y ₂ O ₂ SO _4, and single-phase yttrium oxide was not obtained.

Comparative Example 5 In order to make a comparison with the phosphor of the present invention, a phosphor according to a conventional method was manufactured in the following procedure.

22.58 g of yttrium oxide and 1.760 g of europium oxide were dissolved in 130 mL of 6N hydrochloric acid, and 220 mL of an aqueous oxalic acid solution was added with stirring. Yttrium and europium co-precipitated as oxa oxide. The precipitate was sufficiently washed with pure water, dried at 200 ° C., and baked at 1000 ° C. for 90 minutes. 0.007 g of boron oxide, 0.24 g of barium chloride dihydrate and 0.13 g of lithium chloride were added to 23.19 g of the calcined powder, and calcined at 1400 ° C. for 2 hours. The obtained powder was sufficiently washed with pure water and dried to obtain (Y, Eu) ₂ O ₃ (hereinafter referred to as “comparative phosphor”).

Example 7 Emission of the yttrium-europium composite oxide obtained in Example 5 was evaluated by excitation with a low-speed electron beam. As a result, it was 1.18 times as bright as the comparative phosphor.

Example 8 When the emission of the yttrium-europium composite oxide obtained in Example 5 was evaluated by excitation with vacuum ultraviolet light, it showed 1.29 times the luminance of the comparative phosphor.

Example 9 The precipitate obtained in Example 2 and europium chloride were weighed so that the atomic ratio of yttrium to europium was 100: 3, mixed in 50 mL of ethanol, and mixed for 12 hours. Dried at 60 ° C. 1400 ° C in air
For 2 hours to obtain 2.9 g of (Y, Eu) ₂ O ₃ . When this phosphor was evaluated for light emission by low-speed electron beam excitation, it showed 1.23 times the luminance of the comparative phosphor.

Example 10 When the phosphor obtained in Example 9 was evaluated by excitation with vacuum ultraviolet light, it showed 1.31 times the luminance of the comparative phosphor.

[0064]

According to the present invention, the following excellent effects can be obtained. (1) The rare earth element salt powder of the present invention has an average particle size of 2
It has a small particle size of 1 μm or less, which is unfavorable as a raw material for a phosphor, and a spherical shape. Also, the manufacturing method is extremely simple. (2) The rare earth element oxide powder of the present invention has an average particle diameter of 2 to 2.
10 μm, with little mixing of fine particles and spherical shape,
It is extremely useful as a phosphor material. Further, the production method thereof is extremely simple, and a rare earth element oxide powder can be obtained while maintaining the excellent characteristics of the rare earth salt powder. (3) The phosphor obtained by the present invention has better surface emission characteristics than the phosphor produced by the conventional method, and is used in FED applications, PDP applications, or fluorescent display tube applications in which only the phosphor surface is involved in light emission. Useful.

[Brief description of the drawings]

FIG. 1 is a representative thermal analysis result of a double salt (precipitate) of a rare earth element obtained in Example 2. In the figure, the horizontal axis (X axis) is temperature (unit: ° C.), and the left side of the vertical axis (Y axis) is weight (wei).
ght (unit is%)), and the calorie value (Heat Fl)
ow (unit is uV).

FIG. 2 is a schematic view of an apparatus for performing a slow electron beam excitation emission evaluation.

FIG. 3 is a scanning electron micrograph of a double salt (precipitate) of a rare earth element obtained in Example 2. In the figure, the solid line indicates an enlarged length of 10 μm.

4 is a scanning electron micrograph of a double salt (precipitate) of a rare earth element obtained in Comparative Example 2. FIG. In the figure, the solid line indicates an enlarged length of 10 μm.

5 is a scanning electron micrograph of a double salt (precipitate) of a rare earth element obtained in Comparative Example 3. FIG. In the figure, the solid line indicates an enlarged length of 10 μm.

[Explanation of symbols]

1: Electron gun (LaB ₆ filament) 2: Wehnelt cap 3: Leader electrode (SUS mesh) 4: Incident restriction slit 5: Phosphor coated substrate (anode) 6: Vacuum chamber 7: Constant current (2.6A) 8: Withdrawal voltage (40V) 9: Anode voltage (865V)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01J 11/02 H01J 11/02 B 29/20 29/20 29/32 29/32 (72) Inventor Takahata Tsutomu 1-4-5 Akanedai, Aoba-ku, Yokohama-shi, Kanagawa F-term (reference) 4G076 AA02 AA10 AA14 AA16 AA18 AA19 AB06 AB08 AB09 AB10 AB18 BA13 BA38 BC02 BD02 CA03 CA26 DA11 4H001 CA06 CF02 XA00 XA08 XA39 5C036 CC18 5C040KB MA03

Claims (9)

[Claims] (1) The chemical composition is X ₂ (CO ₃ ) _a (SO ₄ ) _b (O
H) _C · nH ₂ O (where X is Y, La, Ce, Pr, N
d, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
one element selected from the group consisting of r, Tm, Yb and Lu or a mixture of two or more elements, and a is 0.7 <
a is a real number satisfying a <1.5, b is a real number satisfying 0.3 <b <1.3, c is a real number satisfying c = 6-2a-2b, and n is 0 ≦
It is a real number satisfying n <6. ), Wherein the ratio of the number of particles having a particle size of 1 μm or less to the total number of particles is 20% or less. 2. An aqueous solution containing a sulfate ion and a salt of a rare earth element and having a sulfate ion concentration of 0.2 to 5 moles per mole of the rare earth element is heated by adding urea to the solution.
The rare earth element salt powder according to claim 1, wherein a double salt of a rare earth element having a sulfate ion and a hydroxide ion is precipitated. 3. An aqueous solution containing a sulfate ion and a salt of a rare earth element and having a sulfate ion concentration of 0.2 to 5 moles per mole of the rare earth element is heated by adding urea,
3. A double salt of a rare earth element having a sulfate ion and a hydroxide ion is precipitated.
The method for producing a rare earth element salt powder according to the above. 4. A rare earth element oxide powder obtained by firing the rare earth salt powder according to claim 1 at 1100 to 1600 ° C. 5. A method for producing a rare earth element oxide powder, comprising firing the rare earth element salt powder according to claim 1 or 1100 to 1600 ° C. 6. A method for producing a rare earth element oxide powder, comprising adding a rare earth element compound to the rare earth salt powder according to claim 1 and firing. 7. A phosphor comprising the rare earth element oxide powder according to claim 4. 8. A phosphor obtained by the method according to claim 5. 9. The phosphor according to claim 7 or claim 8.
Rikatsu (Y, Eu) _TwoO_ThreePhosphor.