JPS6126513A - Preparation of compound oxide of rare earth metal - Google Patents

Abstract

PURPOSE:To prepare the titled oxide having uniform quality and easily adjustable composition and particle size, by suspending the powder of a rare earth element oxide in a solution of other rare earth element, adding an alkali to the obtained slurry, and calcining the obtained mixed precipitate. CONSTITUTION:Powder of the oxide of a rare earth element M or powder of a compound giving the oxide by calcination is suspeneded in a solution of other rare earth element M'. An alkali (NaOH, NH4OH, etc.: NH4OH is used in the case of preventing the contamination with an alkali metal or alkaline earth metal) is added to the slurry to form an amorphous hydroxide gel of M'. The resultant mixed precipitate is calcined to obtain a compound oxide of rare earth elements (M1-xM'x)2O3 (M and M' are one or more kinds of rare earth elements). The process can be controlled easily compared with conventional dry process and coprecipitation process, and the composition and particle size of the product can be controlled easily. Various compound oxides of rare earth elements having uniform quality can be produced. A fluorescent material having high and uniform luminance can be produced by using the compound oxide of rare earth elements as a raw material of the fluorescent material.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to rare earth elements represented by the general formula (M+-x, M'xhOs (where M and M' represent at least one kind of rare earth element)) This paper relates to a new manufacturing technology for elemental composite oxides.

<Conventional technology> A rare earth element composite oxide is made of (Y, Eu)20s, (
It is a compound that is used for various purposes, including as a raw material for phosphors such as Gd, Tb)203. Conventionally, the following methods have been used to produce this compound.

(2) A method in which powders of oxides of rare earth elements M and M' or compounds that become oxides upon firing are mixed and then fired.

■A crystallizing agent such as oxalic acid, ammonium carbonate, ammonia, etc. is added to a solution containing rare earth elements M and M', and M, M'
A method of co-precipitating and then firing.

<Problems to be Solved by the Invention> -However, since the method (2) uses a solid phase reaction, it requires high temperature and long time for calcination, and there are problems in that it is difficult to control the particle size. In method (2), the rate of precipitation and solubility when a crystallizing agent is added differs depending on the type of rare earth element, so there may be a difference in the composition ratio during the co-precipitation operation, or some of the constituent elements may There was a fear that it would remain in the solution, resulting in poor yield and increased costs.

Means and operation for solving the problems> The present inventors discovered an extremely interesting phenomenon in the process of studying the production of inorganic compounds using gel-like amorphous hydroxide, and led to the present invention. .

That is, an alkali is added to a slurry in which a powder of an oxide of a rare earth element M or a compound that becomes an oxide upon firing is suspended in a solution of another rare earth element M' to form a gelatinous amorphous water of M'. A rare earth element composite characterized by firing a mixed precipitate produced by producing an oxide,
Oxide (Mt-x, M'x)*Oa (However, M, M'
represents at least one kind of rare earth element).

The details of the present invention will be described below.

The rare earth elements in the present invention are elements of the lanthanide group, namely lanthanum, cerium, praseodymium, neodymium,
It is a general term for the /j elements of promethecum, samarium, eurobicum, gadolinium, terbium, dysprosium, holsium, erbium, thulium, ytterbium, and ruffium, plus scandium and yttricum, and the rare earth elements M and M' are , represents seven or more elements selected from these.

Father, M contains elements other than rare earth elements within the range of θmot (l or less, such as alkali metal elements, alkaline earth metal elements, group ■ elements such as aluminum and gallicum, group ■ elements such as silicon and zirconium) It is also within the scope of the present invention that Group V elements such as panadicum and niobium, Group I elements such as molybdenum and tungsten, and transition metals are contained.

In carrying out the present invention, the abundance ratio X of the rare earth element M' contained in the composite oxide is not particularly limited, but is preferably θ, 3 or less for practical purposes. If it is larger than this, the filtration rate of the mixed precipitate produced after addition of the alkali will be reduced, and the advantage of the present invention in terms of operability will be lost.

The oxide of rare earth element M in the present invention has the general formula Mn0
m (However, with some exceptions, n = , j, m = 3)
It is a compound that can be represented by the following, and there are no particular restrictions on the crystal structure. In addition, the compound that becomes an oxide by firing the rare earth element M is a compound that can be made into an oxide by thermal decomposition,
For example, it may be selected from oxalates, carbonates, hydroxides, etc.

The rare earth element M' solution may be obtained by dissolving water-soluble salts such as nitrates, chlorides, sulfates, etc. in water, or may be obtained by dissolving oxides, hydroxides, etc. in nitric acid, hydrochloric acid, etc. It may also be obtained by dissolving in an acid such as sulfuric acid.

The ion concentration of the rare earth element M' in the solution is not particularly limited, but if the concentration is too high, it may become difficult to stir the slurry in which the rare earth element M is suspended in powder form, or a gel-like substance may form. θ, θl ~ θ, 3 mol/L, preferably θ
, θλ˜θ, t s mot7t.

The alkali used in the present invention may be an alkali metal or alkaline earth metal hydroxide solution or aqueous ammonia, but if the purpose of use is to avoid contamination with alkali metals or alkaline earth metals, ammonia It is recommended to use water. The amount of alkali to be used is not particularly limited as long as the total amount of ions contained in the solution of rare earth element M' is at least the theoretical equivalent required to generate hydroxide, but an amount larger than necessary is The yield of the present invention does not change even if . The concentration of the alkaline aqueous solution to be used is not particularly limited, but the concentration that efficiently generates the gel-like amorphous hydroxide of the rare earth element M' is, for example, in the case of ammonia water, NH3-containing @j
-/θ ratio is appropriate.

In carrying out the present invention, the reaction is usually carried out at room temperature, and a reaction time of 70 minutes or more is required for the reaction to proceed sufficiently.

Gel-like amorphous hydroxide of rare earth element M' is a translucent paste-like substance that does not have a clear structural formula, and is an amorphous substance that shows a halo pattern in X-ray diffraction measurements. When an alkali is added to a slurry in which an oxide of the rare earth element M or a powder of a compound that becomes an oxide upon firing is suspended in a solution, the mixed precipitate that is formed is not gel-like and has good sedimentation properties. It is expected that the gel-like amorphous hydroxide adhered to the rare earth element M powder present in the slurry and precipitated together.

Rare earth element M contained in the mixed precipitate thus generated
The gel-like amorphous hydroxide of
s M'x) produces 20g.

In carrying out the present invention, the firing temperature of the precipitate is usually 60θ~/2θθ℃, more preferably 20θ~//θθ℃, although it varies somewhat depending on the type of constituent rare earth element and the type of compound. be. Regarding the firing time, 30 minutes to one hour is sufficient after reaching the specified temperature, but Tenryu's
Calcining the precipitate may require an even longer time.

The firing atmosphere may normally be air, but an inert atmosphere or a weakly reducing atmosphere may be required depending on the type of constituent rare earth elements.

Examples will be described below, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Examples/~3 5 Q mmol of powdered yttrium oxalate is suspended in a europium nitrate solution to form a slurry with the composition shown in Table/~3. Add 2. male thiammonia water to this slurry while stirring. After adding j and tt at once and reacting for 30 minutes, the precipitate was taken out in a furnace and calcined in air at θO°C for one hour.

The powder obtained by the above operation is mixed with each /? It was collected and dissolved in hydrochloric acid. After adjusting the volume to a constant value of θ, the concentration of yttrium and europium in the solution was measured using fluorescent X-rays to determine the europium content (Eu) in the product.
/ Y + Eu motqb) were found to be 3o♂♂, 3.99, ri, //, respectively. These values almost match the initial charging composition. Moreover, Y
, Bu had very little loss and showed a high yield.

In addition, the X-ray diffraction patterns of these powders are all
As shown in the figure, it matched the pattern of yttrium oxide on the A8TM card. This shows that europium is sufficiently dissolved in the crystals of yttrium oxide, and it can be seen that yttrium-europium composite oxides (Yl-x, Eux) 203 of various compositions are produced. .

In addition, after filling these powders into number cells and molding them, they were set in Shimadzu's fluorescent advance meter RF-jθθ, and the excitation wavelength 264 was detected in the 2θ0 direction in the case of a plane by detection with a photomultiplier tube. When the light emission (wavelength 6//nm) was measured, the relative luminances shown in Table 7 were obtained.

(Left below) Comparative Examples 7 to 3 Yttrium nitrate and europium nitrate were dissolved in a bath with the compositions listed in A/ to 3 of Table 2, and the total amount was -00 m
Prepare a solution with a concentration of mat/L.

Add 3/θ oxalic acid bath solution to each of these solutions under stirring.
Add 9. After 7 hours, the sediment was collected and the air qo
Bake at 0°C for 1 hour.

Regarding the powder obtained by the above operation, the europium content (Eu /Y + Eu mot%) was determined in Example 7.
When calculated using the same method as in 3. to 3, the values were 3, 3.93, 3.93, and θθ, which was a considerable deviation from the initial composition. Also, as can be seen from the yields of yttrium and europium in the table, especially for europium, around 3% of the undiluted solution is F.
It is being lost towards the liquid, and fractionation is getting worse.

Furthermore, when the fluorescent brightness of these powders was measured in the same manner as in Examples 7 to 3, the relative brightness values were as shown in Table 1.

Comparative example Y2O3/0. Za4tr (Y Wa4mmot) Eu
203 0.7θy (Bu 4tmmot) After mixing the above substances for λ time using a ball mill, in air, 73
It was baked at 00°C for 3 hours.

The X-ray diffraction pattern of the powder obtained by the above operations is
As shown in FIG. 2, the peak of europium oxide appears as a shoulder along with the peak of yttrium oxide, indicating that europium is not sufficiently dissolved in the crystals of yttrium oxide.

Figure 3 shows the yttrium-europium composite oxides (Yo) obtained in Example λ and Comparative Example
, 96, Euo, o4>20g The particle size distribution of the powder was measured using a light transmission centrifugal sedimentation method Micron Photosizer 8 manufactured by Seishin Enterprises.
The results measured by KA-J-θ00 are shown.

As can be seen from FIG. 3, the composite oxide obtained by the present invention had a smaller particle size and a sharper distribution than that obtained by the dry method.

Further, when the fluorescent brightness of this powder was measured in the same manner as in Examples/--3, the relative brightness was 3j.

Example: Yttrium carbonate/3.0θf (Y 4tJ'mmo
To the slurry obtained by suspending the liquid in θmmoL/L europium nitrate solution θ-, 2.3 j t/1 ammonia water was added at once under stirring, and after reacting for 3θ minutes, the precipitate was removed. The sample was taken out and calcined in air at θθ°C for several hours.

Regarding the powder obtained by the above operation, the europium content (Eu /Y + Eu mat) was determined in Example/
When determined using the same method as in 3., θ/ was found to be approximately the same as the initial composition.

Moreover, the X-ray diffraction pattern of this powder is as shown in FIG. 9, and as in Examples/~3, europium is sufficiently solid bathed in the crystals of yttrium oxide, and the yttrium-europium composite oxide is formed. (Yo, 96, EuO, 04)2
03 is generated.

Further, when the fluorescent luminance of this powder was measured in the same manner as in Examples/--3, the relative luminance was 2.theta., which was higher than that obtained by the conventional method.

The yield for both yttrium and europium is 99.7.
He was in charge.

Example j Yttrium oxalate/za, 9otf (Yg θmmot),
50 m mol/ was added to europium nitrate solution 2θθgo(
To the slurry obtained by suspending Eu/θmmot), aqueous ammonia/J, 7jt was added all at once under stirring, and after reacting for 3θ minutes, the precipitate was separated and placed in air at 9θ0°C. It was baked for 2 hours.

Regarding the powder obtained by the above operation, the europium content (Eu /Y + gu mot ratio) was determined in Example/
It was determined by the same method as in 3 to 3, and it was 10./, which was in good agreement with the initial composition.

The X-ray diffraction pattern of this powder is similar to Examples 7 to 3, indicating that europium is sufficiently dissolved in the crystals of yttrium oxide, and the yttrium-europium composite oxide (Yll-8, Buo, 2 ) 20g is produced.

In addition, by the same method as in Examples/~3, the excitation wavelength! The relative brightness of this powder was 1<1 when the luminescence (wavelength: //nm) was measured.

The yield is 99.6% yttrium and 9% europium. , Z rose.

Example 6 and Comparative Example Gadolinium oxalate, 29.77r (Gd4tJ'mm
ot) to 1. To the slurry obtained by suspending J Ommot/ in terbium nitrate bath liquid θ-(Tb2mmot), /% ammonia water 2. ．． After adding f-ft at once and reacting for 30 minutes, the precipitate was separated and 90g was added at ℃ in a weakly reducing atmosphere (j% H2 + Tatachi Nz).
Baked for an hour.

Regarding the powder obtained by the above operation, the terbicum content [1 (Tb/Gd + Tb mo1%) was determined in the same manner as in Examples/--3.3. Tata, which matched well with the initial preparation composition.

Also, the X-ray diffraction pattern of this powder is as shown in Figure 5, and it is an ASTM card gadolinium oxide.

It matched Ram's pattern. This indicates that terbium is sufficiently dissolved in the crystal of gadolinium oxide, and the gadolinium-terbium composite oxide (
Gd0.96. This shows that Tb0.04 hog is generated.

Furthermore, when the luminescence at an excitation wavelength of 26 nm (wavelength: 4t3 nm) was measured by the same method as in Examples 1 to 3, the relative brightness of this powder was ≦2.

What is the yield of gadolinium? 9.9%, Terbium cotton. It was 2 chi.

For comparison, a composite oxide with the same composition as above was obtained by a coprecipitation method and a dry method, and the relative brightness of the composite oxide was measured. The results were j3 and 32.

Example? and Comparative Examples 7 to ♂ Yttrium/j mo1%, Gadolinium/rt
Rare earth element oxalate containing mot t6. ／♂f (Y
/4t, 4tmmot, Gd J' /-4mmo
t) to jθmmot/to terbium nitrate solution lθ-(T
To the slurry obtained by suspending in 4tmmot), 1 thiammonium water and /θi were added all at once under stirring, and 30
After reacting for a minute, the precipitate was collected and a weakly reducing atmosphere (
The product was fired for 2 hours at θ°C for 9 nights at 93% H2 + 934 N2).

Regarding the powder obtained by the above operation, the terbium content (Tb /Y + Gd + Tb moL'ly
) was determined using the same method as in Examples/~3.1,4
t, 0/, which matched well with the initial charging composition.

The X-ray diffraction pattern of this powder is shown in Figure 6, and it shows gadolinium-yttrium oxide (Gdo,
It matched the pattern of ss, Yo, xs)son.

This indicates that terbium is sufficiently dissolved in the crystals of gadolinium yttricum oxide, and the gadolinium yttrium-terpicum composite oxide (Gdo, +ns, YIl , 144 , T bo, o
n) indicates that tOs is generated.

By the same method as in Examples 7 to 3, the excitation wavelength was −21
h 4tn (emission in case of n (wavelength jgJ' nm)
When measured, the relative brightness of this powder was 63.

What is the yield of yttrium? Section 9.2, Gadolinium 9.
94J, Terbium 9? , it was 2 yen.

For comparison, a composite oxide having the same composition as above was obtained by a coprecipitation method and a dry method, and the relative brightness of the composite oxide was measured. The results were rs and 3ge.

Example ♂ and Comparative Example 2~/θ Rare earth element oxalate 4t2.3jt (Y♂6゜4tmm) containing yttrium and calcilam in a molar ratio of 1
otSCa 9. To the slurry obtained by suspending jθmmoA/A europium nitrate solution lθ-(Eugmmot), aqueous ammonia j,
/θ2 was added at once and reacted for 3θ minutes, and then the precipitate was separated and calcined in air at 00°C for 2 hours.

Regarding the powder obtained by the above operation, europium-containing t (Ru / Y + Ca −)-Bu mo
When L'4) was determined in the same manner as in Examples 1 to 3, it was found to be U and OO, which matched well with the initial charging composition.

Moreover, the X-ray diffraction pattern of this powder matched the pattern of yttrium oxide in the A37M card.

This means that europium and calcium are oxidized)
It is shown that yttrium calcium-eurobium complex oxide (YO, m4.CaO009g, Bu6.04) to
This shows that n is being generated.

In addition, by the same method as in Examples 7 to 3, the excitation wavelength, 2
The relative brightness of this powder was 6θ when the luminescence (wavelength: 1/plane) was measured at 4tnm. On the other hand, when measurements were carried out in the interval, the relative brightness of composite oxides with the same composition obtained by the conventional coprecipitation method or dry method was 3 and 33, respectively.

The yield is yttricumtata, 6chi, calcillum? 9.
3'A, Europium Tower, 7%.

For comparison, a composite oxide having the same composition as above was obtained by a coprecipitation method and a dry method, and the relative brightness of the composite oxide was measured. The results were j3 and 33.

Effect> The present invention improves the dry manufacturing method, which conventionally required high temperature and long time for calcination and had difficulties in controlling particle size, and the rate of mutual precipitation of rare earth elements when adding a crystallizing agent. This method is an alternative to the coprecipitation method, which has the risk of discrepancies in composition ratio or poor yield due to differences in solution and bath solubility. etc., and the quality of the obtained products has little variation, making it possible to manufacture various rare earth element composite oxides. Moreover, the rare earth element composite oxide obtained by the production method of the present invention, especially when used as a raw material for a phosphor, exhibits better characteristics compared to those obtained by the conventional production method, and has better brightness. , the variation is also small.

In this way, the present invention provides a rare earth element composite oxide (M+-
This method has great practical significance as a method for producing 8, M'X)2O3 on an industrial scale.

[Brief explanation of drawings]

Figure 1 shows the X-ray diffraction pattern of the powder obtained in Examples 7 to 3, and Figure 2 shows the X-ray diffraction pattern of the powder obtained in Comparative Example G.
Linear diffraction pattern, Figure 3 is the particle size distribution of the powder obtained in Example G and Comparative Example G, Figure G is the X-ray diffraction pattern of the powder obtained in Example G, and Figure 5 is the particle size distribution of the powder obtained in Example G. The X-ray diffraction pattern of the powder obtained in Example B is shown, and FIG. 6 is the X-ray diffraction pattern of the powder obtained in Example 7. Patent applicant: Asahi Kasei Kogyo Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 3 (P) Figure 4 2e Figure 5 Figure 6

Claims (1)

[Claims] A gel-like amorphous hydroxide of M' is produced by adding an alkali to a slurry in which a powder of an oxide of a rare earth element M or a compound that becomes an oxide upon firing is suspended in a solution of another rare earth element M'. A rare earth element composite oxide (M_
1_-_x, M'_X)_2O_3 (However, M, M'
represents at least one rare earth element).