JPS59162132A - Production of oxysulfate of rare earth element - Google Patents

Abstract

PURPOSE:The reaction between a hydroxide of rare earth element and sulfuric acid or a sulfate salt is effected in water and the product is heated in an oxidative atmosphere to enable the easy production of an oxysulfate of rare earth element of less fluctuation in quality, thus being suitable for use as a fluorescent parent material. CONSTITUTION:One or more than 2 kinds of hydroxides of rare earth elements such as yttrium hydroxide or terbium hydroxide and sulfuric acid or a water- soluble sulfate salt such as ammonium sulfate or potassium sulfate are allowed to react with each other in water, preferably under heating. Then, the resultant product is placed in a roasting oven and heated in an oxidative atmosphere of air or oxygen at 600-1,200 deg.C for 1-5hr to give the objective oxysulfate of rare earth element. The resultant oxysulfate is high in purity and the fluorescent body therefrom is higher in brightness with less fluctuation than those in the fluorescent bodies which are prepared by the conventional processes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new method for producing oxysulfate of rare earth elements, which is easier to produce than the conventionally used production methods, and the quality of the resulting product is less variable. It has the characteristic of having few 2nd defects. Furthermore, the rare earth element oxysulfate obtained by the production method of the present invention is excellent as a matrix for a phosphor.

Oxysulfates of rare earth elements have the general formula Lnti
t (SO4) (Ln; rare earth element) and table t) f;
It is a compound that can be formed with carbon, and the method of producing this compound has conventionally been to thermally decompose a sulfate of a rare earth element. This method uses gold that undergoes a thermal decomposition reaction at high temperatures, but the difference between the thermal decomposition temperature of sulfate and the thermal decomposition temperature of oxysulfate, which becomes the product, is not large, so there is always oxysulfate in the product. It contained oxides produced by thermal decomposition or undecomposed compounds.

Furthermore, slight variations in the particle size of the raw sulfate, the amount of filling in the incense bowl, the roasting time, the roasting temperature, etc. can significantly change the quality of the product, making it difficult to produce rare earth oxysulfates on an industrial scale. That was difficult.

The present inventors previously discovered a new method for producing oxysulfate of rare earth elements and filed a patent application (Japanese Patent Application No. 57-488
No. 32, Japanese Patent Application No. 112489/1989).

Furthermore, the present inventors have intensively investigated the reaction characteristics of rare earth element hydroxides, and have found that rare earth element hydroxides and sulfuric acid or sulfuric acid salts do not undergo any interesting reactions.
This heading led to the present invention.

The configuration of the present invention is as follows. In other words, rare earth elements are produced by heating a product obtained by reacting one or more rare earth element hydroxides with sulfuric acid or a water-bathable sulfate in water in an oxidizing atmosphere. This is a method for producing oxysulfate.

In the present invention, the rare earth elements are elements of the lanthanide group, namely lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
It is a general term for the fc17 elements, which includes scandium and yttrium.

The hydroxide of a rare earth element in the present invention has a general formula. Ln(
It is expressed as OH)s, and the manufacturing method thereof is not limited.

The water-soluble sulfates mentioned in the present invention include sulfates of rare earth elements, sulfates of metals such as magnesium sulfate, calcium sulfate, and potassium sulfate, and sulfates of amines such as ammonium sulfate and pyridinium sulfate.

In carrying out the entire invention, the raw material hydroxide of rare earth element is reacted in the form of a slurry, and its concentration Fi
It is not particularly limited. In addition, the raw material sulfuric acid is
1/2 mole is required per mole of the rare earth element, and if more than this is used, sulfate of the rare earth element will be produced as an unreacted product, resulting in a low yield of the target product of the present invention. When using a sulfuric acid salt as a raw material, the amount used is 1
It is sufficient that the amount is 1/2 mole or more, and even if it is too large, the yield of the target product of the present invention will not change.

The rare earth element hydroxide slurry used in the present invention is prepared by adding ammonia, alkali such as sodium hydroxide to an aqueous solution of the rare earth element chloride, sulfate, nitrate, acetate, etc.
It is possible to use the slurry liquid thus produced. That is, CZ- ion, NO3- ion, CH
Even if sCoo- ions and the like coexist, the object of the present invention can be achieved.

Also, when making rare earth element hydroxides using the above method,
The object of the present invention can also be achieved by simultaneously dissolving all of the sulfuric acid or sulfuric acid salts that serve as a source of sulfuric acid radicals, and then adding an alkali to produce the hydroxide of the rare earth element.

In carrying out the present invention, the reaction of the rare earth element with the hydroxide in water proceeds even at room temperature, but in order to complete the reaction in a short time, it is preferable to heat the reaction.

The method of heating in an oxidizing atmosphere as used in the present invention is carried out in an ordinary roasting furnace in air or in a gas with an appropriate oxygen concentration, and the temperature is suitably in the range of 600 to 1200°C. A temperature range of 700 to 800°C is economical.

If the temperature exceeds 1200°C, some oxides will be mixed. Further, the roasting time varies depending on the roasting temperature, etc., but in the above roasting temperature range, 1 to 5 hours is appropriate.

The rare-earth elements used in the present invention include a matrix that constitutes a normal phosphor and its activating material, such as yttrium and europium as its activating material, or gadolinium and terbium as its activating material. Furthermore, if a mixture of lanthanum and terbium, yttrium and terbium, or lanthanum and europium is used, it is possible to produce a new oxysulfate-based phosphor that has never existed before.

That is, conventionally, phosphors are composed of a rare earth element oxysulfate as a base material and doped with another type of rare earth element as an activating substance (specifically, terbium-activated gadolinium oxysulfate). (G40tSO
4: Tb), europium-activated yttrium oxysulfate (Y2O2SO4: Eu), europium-activated lanthanium oxysulfate (La20,
804: Eu ) and the like are made by thermally decomposing a mixed sulfate of a rare earth element as a base and a rare earth element as an activating material. In this case, the purity of the product obtained is low;
Impurities include constituent rare earth element oxides and undecomposed sulfates.

Therefore, when used as a phosphor, light emission at a wavelength other than the designed emission wavelength is observed, and for this reason, this type of phosphor has not been put to practical use in the past. The method of the present invention can be said to be a new and practical method that eliminates such drawbacks.

Conventionally, rare earth element oxysulfate has to be obtained by roasting the rare earth element sulfate at high temperature for many hours, so during its production, sulfur dioxide gas is generated, resulting in equipment corrosion and durability deterioration. However, according to the present invention, by roasting at a relatively low temperature and in a short time, it can be roasted at a relatively low temperature and in a short time, resulting in high purity and almost no generation of harmful gases such as sulfur dioxide gas. Now you can get it without having to worry about it. The production method of the present invention has the advantage that it is possible to control the particle size in terms of reaction time, etc., and it is possible to obtain powder with a narrow particle size distribution. Moreover, the rare earth element oxysulfate obtained in this way? The present invention has great practical significance also in that the phosphor used as the base material has higher brightness and less glare than that produced by conventional manufacturing methods.

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

Examples 1 to 3 Raw materials having the compositions listed in Tables 1 to 6 of Table 10 were placed in 1 ton flasks and heated at 95°C for 2 hours with stirring. Roasted for 2 hours. The results of X-ray diffraction of each of the obtained white powders are shown in Figures 1 to 3. When the interplanar spacings are calculated from the figures, they are as shown in Table 2 (C1). Regarding gadolinium. Good agreement was seen with the value of the ASTM card, and good agreement with that of gadolinium was also found for yttrium, although it is not listed in the ASTM card.In addition, some parts of lanthanum are not listed in the ASTM card. A peak was observed, but the lattice constants a=4.227, b=4.310, obtained using the values of the interplanar spacing of the peak.
c=13.575 is the literature value (a-4,257, b=
4,173, c = I S, 67) and is in good agreement within the accuracy of XlfIA diffraction, and it seems that the ASTM card was old and there was an omission in the description.

Furthermore, each of the powders obtained in Examples 1 to 3 was added at 0.6
0 f! , 0.80 f/, 0.909 sampled and added mL
.

When 6N hydrochloric acid was added dropwise little by little, 2
．． 03, 6.2.02, and 2.017 were dissolved at the time of addition. This hydrochloric acid cap almost matches the theoretical amount of 2tILt when the produced powder is oxysulfate.

In addition, when the total amount of this solution was made into a constant amount of 200 ml, and the molar ratio (Ln/s) of rare earth elements and sulfur in the solution was measured using fluorescent X-rays, it was found that yttrium, lanthanum, and gadolinium each had a molar ratio of 2. It was C2, 2, 03, 2, 01. These values are in close agreement with the theoretical amounts for pure oxysulfate. The above results prove that the powders obtained in all of Examples 1 to 5 are pure oxysulfates.

1) A, A, Grizik, N, G, Abdu
llina.

N, M, Garifdzhanova; Z, h, N
eorgan, Khim, 18.

596, (1975); Ru5s, J, Ino
rg, Chem.

Su, 515. (1973) Table 1 Table 2 (A) Table 2 (B) Table 2 (C) c= obtained by Kempo
1367 It can be said that there is good agreement within the accuracy range of X-ray diffraction.

Examples 4 to 7 Raw materials having the compositions shown in Table 6 were placed in 1 t flasks,
The mixture was heated at 95°C for 2 hours with stirring, and the resulting precipitate was collected and roasted in air at 800°C for 2 hours. X-ray diffraction of each of the obtained white powders and the molar ratio (Gd/S)'(r) of rare earth elements and sulfur performed in Examples 1 to 5 revealed that Gd2O, So , which matched well with my aspirations.

Table 3 Examples 8 to 10 Gadolinium oxide (Gd, O8) o, t mol to 6N-
Five batches of slurry of gadolinium hydroxide were prepared by dissolving it in 105'td of hydrochloric acid, adding water to the solution, and then adding 1105m of 6N ammonia water. Add 0.1 mol and 0.2 mol of ammonium sulfate to each slurry, respectively.
After adding 0.5 mole, the mixture was heated and stirred in the same manner as in Example 1, and roasted at 800° C. in air. The X-ray diffraction patterns of the obtained powders were the same for each powder, with Gd, 0. S
It was that of o. In addition, when the molar ratio of Gd/S was measured using the same method as in Example 1, it was found that each
．． 01.2, 10.2.05'ii, and were in good agreement. In addition, the respective yields were 98%, 98%, and 97%.
It was in good agreement with Chi.

Example 11 Gadolinium oxide (Gd, 03) 0.1 mol 6N-
Dissolve in 105 m of hydrochloric acid, add water and bind to 500 m, add a solution of 0.1 mol of ammonium sulfate dissolved in 20 m of water, stir, and add 105 fn of 6N aqueous ammonia.
t was added to make a cloudy slurry.

The slurry was heated to 95°C and stirred for 2 hours, and then the entire precipitate was collected and roasted at 800°C for 2 hours. As a result of analyzing the obtained white powder in the same manner as in Example 1, it was found that Gd, 0
It was confirmed that it was 1804. Also, Gd, 0tS
The yield of 0.0 was 98.

Comparative Example 1 Yttrium sulfate Yz(SO4)s.8H,010f was roasted at 800°C and 1000°C for 6 hours each. 800℃
The results of X-ray diffraction of the powder obtained by roasting are shown in Figure 2.As can be seen from this figure, aoo'c
No yttrium oxysulfate was produced during roasting. Further, the results of X-ray diffraction of the powder obtained by roasting at 100° C. are shown in FIG. In addition to the peak of yttrium oxysulfate, there were also peaks other than the compound in the diffraction pattern. As can be seen from the results, in the roasting at 100° C., yttrium peroxysulfate was partially produced, but other compounds were also mixed. Also, Y/S by Fluorescence XIw
When the molar ratio was measured, it was 2.98.

In addition, Fig. 6 shows Example 1 and Comparative Example 1 (1000°C
The particle size distribution of the yttrium oxysulfate powder obtained in each case (roasting) is shown below. As can be seen from the figure, the oxysulfate obtained by the present invention had a smaller particle size and a sharper distribution than that obtained by the conventional method.

Comparative Examples 2 and 3 Sulfuric acid rank y Lay (80,), -9H,010
9” and gadolinium sulfate G4 (So<)s・8H
, 010f in the same manner as in Comparative Example 1.
Roasting was performed at 0°C and 1000°C. When X-ray diffraction was performed on each obtained powder to check the formation of oxysulfate of the corresponding rare earth element, no diffraction peak of oxysulfate appeared after roasting at 800°C, as in Comparative Example 1. , 1000℃ roasted tea, Comparative Example 1
Similarly, the diffraction peak of oxysulfate also appeared, but there were also peaks of other corresponding rare earth element oxides. La/S of each powder by fluorescent X-ray
, Gd/S molar ratio was measured and found to be 3.1, respectively.
It was 1.3.09.

Example 12 Yttrium oxide (Yz03) 0.095 mol and europium oxide (Eu, O,) 0.005 mol'
fc was dissolved in 110 nLlVc of 6N hydrochloric acid, and then water was added to make a 1 t solution. Add ammonium sulfate (
A solution of 0.1 mol of (NH4)tso4) dissolved in 200 ml of water was added, and after stirring, 110 d'i of 6N ammonia water was added.
In addition, a cloudy slurry was made. The slurry was heated to 95°C and stirred for 2 hours, then the precipitate tF was collected and roasted in air at 800°C for 2 hours. Take one part of the obtained powder,
As a result of dissolving it in hydrochloric acid and analyzing its composition using the usual method, Y:
The molar ratio of Eu:S was 95:5:50. Furthermore, the X-ray diffraction and folding patterns of the obtained powder are almost the same as those shown in FIG. 1, and its composition is y,..., zu. ,, o
, so4. Also, the yield at this time was 9
It was 8chi.

After filling the obtained powder into a sample cell and molding it, it was set in a Shimadzu fluorescence photometer RF-500, and detected with a photomultiplier tube to detect the emission in the 90° direction when the excitation wavelength was 290 nm (wavelength: 615 nm). )'i measurement, a relative intensity of 57 was obtained. On the other hand, yttrium sulfate and europium sulfate were mixed in the same ratio as in this example, and thermal decomposition (
The powder obtained at 1100° C. for 4 hours was measured using the same scale and had a relative strength of 30. That is, the phosphor based on yttrium oxysulfate-1t-based material obtained in this example had luminance 1.9 times higher than that of the phosphor based on oxysulfate obtained by the conventional method. Ta.

Note that the yield of YtOHSo4;Eu was 96%.

As can be seen from the Examples and Comparative Examples, the effects of the present invention are as follows.

■The purity of rare earth element oxysulfate is higher than that produced by conventional methods, and a sharp particle size distribution can be obtained.

Q) The method for producing oxysulfate of rare earth elements is simpler than conventional methods, and the yield is also high.

(2) When applied as a method for producing phosphors, the luminance of the powder obtained is higher than that obtained by conventional methods.

[Brief explanation of drawings]

Figure 1 shows the X-ray diffraction pattern of the powder obtained in Example 1, Figure 2 shows the X-ray diffraction pattern of the powder obtained in Example 2, and Figure 3 shows the X-ray diffraction pattern of the powder obtained in Example 5. The line diffraction pattern, FIG. 4, is for Comparative Example 1.
X-ray diffraction pattern of powder obtained by roasting at ℃, 5th
The figure shows the X-ray diffraction pattern of the powder obtained by roasting at 1000°C in Comparative Example 1. Figure 6 shows the particle size of the powder obtained in Example 1j=- and Comparative Example i (roasted at 1000°C). It is a graph showing distribution. Figure 1 Y2o2S04 Figure 2 Figure 3 GdzO2SO+ 20 30 40 5
0Figure 4 20 30 40
500 Figure 5 20 30 40
50Figure 6 0 2 4 6 8 IQ 14 16 18 2
0 company investment (/J)

Claims (1)

[Claims] () Heating a product obtained by reacting J1m or a hydroxide of two or more rare earth elements with a high-value acid or a water-soluble sulfate in water in an oxidizing atmosphere. A method for producing an oxysulfate of a rare earth element according to claim 1, wherein the two or more rare earth elements contain a phosphor matrix and its activating material. Method for producing oxysulfate.