JP2006327903A - Method for producing rare earth oxysulfate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rare earth oxysulfate by using a rare earth oxide as a starting material, wherein the cost reduction and the mass production are easily attained by a new and simple treatment operation process. <P>SOLUTION: An objective rare earth oxysulfate is obtained by preparing a milling product by mixing an oxide of a rare earth element or oxides of a plurality of rare earth elements and a sulfur raw material while giving a mechanical energy by using a ball mill device, and then heating the prepared milling product in air. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a rare earth oxysulfate from a rare earth oxide. More specifically, the present invention relates to a method for producing a rare earth oxysulfate, characterized in that a rare earth oxide and a sulfur raw material are mechanically applied with energy and then heated in air to be converted into a rare earth oxysulfate.

Rare earth oxysulfate (rare earth oxysulfate) represented by the general formula R ₂ O ₂ SO ₄ (R is a combination of one or more rare earth elements consisting of Y, La and a so-called lanthanide element having an atomic number of 58-71) Is well known as a substance used as a phosphor in various video devices and display devices, or as an electronic component material or sensor.

  As a general method for producing a rare earth oxysulfate, it is well known that it is produced by thermally decomposing a rare earth element sulfate. On the other hand, there is a method in which a rare earth oxysulfate is obtained by reacting a rare earth element ion with sulfate ion and urea or a derivative thereof in an aqueous solution to produce a precipitate, and separating and baking this product. It has been proposed (see Patent Document 1).

  Alternatively, one or more rare earth element hydroxides are used as starting materials, and this is reacted with sulfuric acid or water-soluble sulfate in an aqueous solution, and the resulting product is heated in an oxidizing atmosphere. A method for producing rare earth oxysulfate has also been proposed (see Patent Document 2).

  Furthermore, a method of obtaining a rare earth oxysulfate by heating rare earth tridisulfide under a flow of dry air (Patent Document 3), using a rare earth oxide as a starting material, suspending it in water, sulfuric acid or sulfuric acid A method of obtaining a rare earth oxysulfate by adding a salt and reacting, collecting the obtained deposit, and then calcining (Patent Document 4) has been proposed in Patent Document.

JP 58-167426 A JP 59-162132 A JP 2002-267631 A (paragraph 0046) JP 2000-313619 A

  The present invention is a reaction process based on a novel principle, which is different from any of the above-described prior art, that is, a process using a reaction process using an aqueous solution as a reaction medium or a process using a reaction process for oxidizing tridisulfide. Thus, it is intended to propose a method for easily obtaining rare earth oxysulfate. That is, starting from rare earth oxides, the rare earth oxysulfate is manufactured and provided by a simpler process.

Therefore, as a result of intensive studies by the present inventors, a predetermined amount of a rare earth oxide raw material and a sulfur raw material are mixed, processed by a pulverizing mill such as a ball mill apparatus, and mixed with both raw material mixtures by applying mechanical energy. The present inventors have found that a rare earth oxysulfate can be easily produced by simply converting it to a rare earth oxysulfate simply by heating it in air. This invention is made | formed based on this knowledge, and the structure is as describing in (1)-(5) below.
(1) One or more kinds of rare earth oxides and a sulfur raw material are mixed while mechanically giving high energy using a ball mill apparatus, and the obtained milling product is heated in air. , A method for producing rare earth oxysulfate.
(2) The one or more rare earth oxides are rare earth sesquioxides represented by the general formula R ₂ O ₃ (where R is a rare earth element), and the mixing ratio of the sulfur raw material to the rare earth sesquioxides is as follows: Based on the atomic ratio between the number of oxygen atoms N _(O) in the rare earth sesquioxide represented by the general formula R ₂ O ₃ and the number of sulfur atoms N _(S) in the sulfur raw material, N _(O) / The method for producing a rare earth oxysulfate according to (1), wherein the N _(S) ratio is set to 3 or less, preferably 1 to 3.
(3) The method for producing a rare earth oxysulfate according to (1) or (2), wherein the sulfur raw material is granular or powdered simple sulfur composed only of elemental sulfur.
(4) The method for producing a rare earth oxysulfate according to (1) or (2), wherein the sulfur raw material is liquid carbon disulfide.
(5) The method for producing a rare earth oxysulfate according to (1), wherein a temperature at which the obtained milling product is heated in air is in a temperature range of 700 to 1000 ° C.

Here, the significance of mixing one or more kinds of rare earth oxides and sulfur raw materials while giving mechanically high energy using a ball mill device is that not only both raw materials are uniformly mixed but also mechanical energy. As a result, sulfur atoms are substituted at some oxygen sites in the rare earth oxide molecule, and the rare earth oxide is partially sulfided. The resulting intermediate product (milling product) is oxidized by a subsequent heating step to form the desired oxysulfate compound. Therefore, if the amount of the two raw materials is too small, the unreacted rare earth oxide remains in the rare earth oxysulfate produced by the subsequent heating step. good. In (2), the reason why the mixing ratio N _(O) / N _(S) is specified to be 3 or less, preferably 1 to 3, is based on this point.

If the temperature at which the product obtained by milling with a ball mill is heated in air is too low, the oxidation reaction of the sulfur atom substituted with the rare earth oxide does not occur and the desired rare earth oxysulfate compound is obtained. If the temperature is too high, the target final product (rare earth oxysulfate) contains a large amount of rare earth oxides. The heating temperature is preferably about 700 to 1000 ° C. In order to obtain an almost single-phase oxysulfate, it is necessary to determine the heating temperature more strictly according to the raw materials and milling conditions. For example, when N ₍₀₎ / N _(S) = 1 using carbon disulfide, a heating temperature of about 865 ° C. is sufficient if milling is sufficiently performed. When sulfur is used so that N _(O) / N _(S) = 3, heat treatment is preferably performed at a higher temperature.

  The method for producing a rare earth oxysulfate according to the present invention comprises mechanically milling a rare earth oxide as a starting material and a sulfur raw material with a ball mill device to uniformly mix both raw materials, and the resulting mixed product is obtained using an electric furnace or the like. Since the rare earth oxysulfate can be obtained simply by heating in air, the production process is very simple, and the concentration, temperature, time, and pH adjustment when depositing the precipitation product as in aqueous reaction systems Such complicated reaction operation and management are not necessary. In addition, since the ball mill apparatus used can handle a large amount of raw materials at one time, it is also suitable for the case where a large amount of rare earth oxysulfate is manufactured, and it has a special effect that can be easily implemented. Is played.

  In the present invention, the mechanical milling operation is performed in the air from the viewpoint of simplifying the process, but on the other hand, it can be performed in a controlled atmosphere, for example, an inert atmosphere. Includes making this an embodiment, and does not exclude it. In any case, according to the present invention, the target compound can be easily obtained at low cost by using a simple processing operation and apparatus.

  Hereinafter, the present invention will be specifically described with reference to the drawings and examples. However, these examples are disclosed as an aid for facilitating the understanding of the present invention, and are not limited by these examples.

  The present invention comprises a two-step process comprising preparing a rare earth element oxide and a sulfur raw material and milling them, and then heating the milling product in air to produce a rare earth oxysulfate. is there.

  The mill used for the milling operation is not particularly limited as long as it has a function of mixing both raw materials uniformly and mechanically imparting high energy, and a ball mill device can be used. From the viewpoint of providing, it is desirable that the material of the ball and the container (pot) of the ball mill apparatus is hard and has a high density, for example, cemented carbide (tungsten carbide). The device type is also preferably a high energy ball mill device such as a planetary ball mill. Of course, it is desirable that there is no fear of contamination with impurities other than rare earths by this operation.

  Milling while applying mechanically high energy replaces the oxygen atom of the rare earth oxide with the sulfur atom of the sulfur raw material, producing a mixture with different properties from the ordinary mixture just by mixing them. Is done. In order to distinguish this mixture from a simple mixture in which a rare earth oxide and a sulfur raw material are mixed, the mixture produced by this milling operation is referred to herein as a milled product.

  After the milling operation is completed, the milled product is heat-treated in air at a temperature of 700 to 1000 ° C. using a heating apparatus such as an electric furnace, whereby the target compound, rare earth oxysulfate is generated. In the milling operation, the amount of the rare earth element and the sulfur raw material is set so that the sulfur atom ratio is somewhat larger than the stoichiometric ratio (2: 1) of the rare earth atom and the sulfur atom in consideration of sulfur loss due to milling. Choose it.

That is, rare earth trioxide represented by the general formula R ₂ O ₃ (R: any one of rare earth elements including yttrium, lanthanum, and lanthanide elements having atomic numbers of 58 to 71) is used as the rare earth element oxide. A kind or a plurality of kinds may be used, and the amounts of the trioxide and the sulfur raw material may be selected so that the sulfur atom of the sulfur raw material has a ratio of one or more to three oxygen atoms of the trioxide.

  Further, the sulfur raw material may be simple sulfur composed only of small granular or powdery sulfur elements, and liquid carbon disulfide or the like can be used. When using elemental sulfur, it is preferable to use a slightly excessive amount of sulfur relative to the stoichiometric ratio. If an excessive amount of elemental sulfur is used, it takes a long time to perform sufficient milling. So be careful. When elemental sulfur is used, milling may be performed in an inert atmosphere such as an argon atmosphere. When liquid carbon disulfide is used as a sulfur raw material, even if the ratio of the rare earth sesquioxide oxygen atom to the carbon disulfide sulfur atom is selected to be about 1: 1, there is little effect on milling.

  The rotation speed and operation time of the ball mill for high energy milling are the type of ball mill used, the reaction vessel and ball material, the size of the reaction vessel, the weight and number of balls, the amount of rare earth oxide and sulfur raw material charged, etc. Varies depending on the conditions. In the case of using a planetary ball mill, when the total weight of both raw materials is set to about 1/70 of the ball weight, for example, milling at 250 rpm for at least about 4 hours is required. If sufficient high energy milling is not performed here, care must be taken because rare earth oxides are mixed in the final product. If the amount of raw material charged relative to the ball is small, the time required for milling may be short, but the possibility of impurities being mixed increases. On the other hand, if the amount of raw material charged is relatively large, the possibility of impurities being mixed can be reduced, but the time required for milling becomes longer. If liquid carbon disulfide is used as the sulfur raw material, the milling time can be shortened compared with the use of powdered single sulfur.

  After the milling operation, the obtained milling product is subjected to a heat treatment in air. The temperature of this heat treatment step depends on various conditions such as the state of the milled product. Rare earth oxysulfate starts to be generated from about 700 ° C., but a more preferable heating temperature is preferably from about 850 ° C. to about 1000 ° C. If the heating temperature is higher than 1000 ° C., rare earth oxides may be produced even if milling is sufficient. When using liquid carbon disulfide as the sulfur raw material, if a quantity larger than the stoichiometric ratio is selected, the carbon component remains in the product obtained by milling, and the milling product is heated. In this case, heat generation due to carbon oxidation occurs, so that a rare earth oxysulfate can be obtained at a lower heating temperature.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1;
1.7179 g of commercially available yttrium sesquioxide (Y ₂ O ₃ , white powder, purity 99.9%) was weighed and commercially available carbon disulfide (CS ₂ , liquid, purity 99.0%, density 1. 266 g / ml (20 ° C.) is placed in a tungsten carbide container (capacity: 80 ml) loaded with 23 tungsten carbide balls having a diameter of 10 mm (total weight: about 181 g), and a planetary ball mill is used. Milling was performed in air for 6 hours at a rotational speed of 250 revolutions per minute. During milling, the container was cooled with a spot air conditioner. At this time, the molar ratio of the oxygen atom contained in yttrium sesquioxide and the sulfur atom contained in carbon disulfide was about 1: 1. This stoichiometric relationship was in excess of CS ₂ over the expected product Y ₂ O ₂ SO ₄ .
The product obtained by milling was collected and heat-treated in an electric furnace at 865 ° C. for 30 minutes in the presence of air. As a result, a white powder was obtained. The heating rate of the electric furnace was about 3.3 ° C. per minute.

A diffraction pattern of the obtained white powder was obtained with an X-ray diffractometer to identify the product. FIG. 1A is an X-ray diffraction pattern of white powder obtained after heating, and FIG. 1B is a graph of yttrium oxysulfate (Y ₂ O ₂ SO ₄ ) registered in the powder X-ray diffraction database. It is an X-ray diffraction pattern (# 41-0685).
From these comparisons, it became clear that the white powder according to this example had a crystal structure belonging to orthorhombic system. In addition, the peak positions of the two coincided within the measurement error range. From this, it was confirmed that the white product was yttrium oxysulfate. That is, it has been clarified that yttrium oxysulfate can be produced by the reaction process of the present invention.

Example 2;
0.6339 g of commercially available yttrium trioxide (Y ₂ O ₃ , white powder, purity 99.9%)
Similarly, 0.9926 g of commercially available europium sesquioxide (Eu ₂ O ₃ , white powder, purity 99.99%) was weighed respectively, and this was commercially available carbon disulfide (CS ₂ , liquid, purity 99.0%, It is mixed with 0.508 ml of density 1.266 g / ml (20 ° C.) and placed in a tungsten carbide container (capacity 80 ml) charged with 23 tungsten carbide balls (10 mm diameter) (total weight: about 181 g). Using a planetary ball mill, milling was performed in the air for 12 hours at a rotational speed of 250 revolutions per minute. During milling, the container was cooled with a spot air conditioner. At this time, the molar ratio of yttrium to europium is approximately 1: 1. The molar ratio of oxygen atoms contained in yttrium sesquioxide and europium sesquioxide to sulfur atoms contained in carbon disulfide is also about 1: 1, and yttrium europium oxysulfate (YEu) expected to be produced. ) CS ₂ was excessive with respect to ₂ O ₂ SO ₄ . The product obtained by milling was collected, and this was heat-treated at 865 ° C. for 30 minutes in the presence of air in an electric furnace to obtain a white powder. The heating rate of the electric furnace was about 3.3 ° C. per minute.

X-ray diffraction pattern of the white powder obtained after heating in FIG 2 (a), X-ray diffraction of yttrium oxysulfate registered in the powder X-ray diffraction database in FIG. _{(B) (Y 2 O 2} SO 4) X-ray diffraction pattern (# 48-1211) of europium oxysulfate (Eu ₂ O ₂ SO ₄ ) registered in the powder X-ray diffraction database is shown in FIG. It was.

  From these comparisons, it was clarified that the white powder obtained in Example 2 had an orthorhombic crystal structure. Further, when the diffraction peaks of (b) and (c) are compared at the peak position near the diffraction angle (2θ) of 30 degrees, which is the peak corresponding to the lattice spacing with respect to the same lattice plane, the present embodiment is concerned. The peak position of the white powder is located between the peak position of yttrium oxysulfate and the peak position of europium oxysulfate. As a result of the oxysulfate complexed with yttrium and europium, the lattice spacing was different for each oxysulfate. It was found that the structure showed an intermediate value.

As a result, the white powder obtained by the synthesis process shown in Example 2 is not a mixture of yttrium oxysulfate and europium oxysulfate, but a composite oxyoxygen represented by the general formula: (YEu) ₂ O ₂ SO ₄ It was confirmed to be a sulfate compound, that is, yttrium europium oxysulfate.

  In the examples shown above, an example of synthesizing yttrium oxysulfate from yttrium sesquioxide and an example of synthesizing yttrium europium oxysulfate from yttrium sesquioxide and europium sesquioxide in a molar ratio of 1: 1. Although shown, these examples are one embodiment of the present invention, and the present invention is not limited to these examples.

In other words, the present invention includes the case where oxysulfate having various compositions can be synthesized and provided by including other rare earth sesquioxides or combinations thereof. In addition, a rare earth oxysulfate doped with one or a plurality of rare earths (for example, Y ₂ O ₂ SO ₄ : Eu, Gd ₂ O ₂ SO ₄ : Eu, etc.) by appropriately selecting a blending amount of a plurality of rare earth sesquioxides. ) Can be obtained and included in a similar manner.

  Further, granular or powdered simple sulfur may be used instead of liquid carbon disulfide. However, when elemental sulfur is used, or when the amount of carbon disulfide is the minimum amount necessary to obtain oxysulfate, heat generation due to oxidation of carbon does not occur in the heat treatment step, so the heat treatment temperature is It is necessary to take measures such as raising the time or lengthening the time.

  As described above, it is clear that the method for producing the rare earth oxysulfate according to the present invention has been described in detail. The present invention can be started from rare earth oxides, troublesome reaction operation and separation / recovery operation in an aqueous solution. It can be easily manufactured by simple operation starting from easily available raw materials, etc., and provides an excellent means for synthesizing rare earth oxysulfate. In recent years, rare earth oxysulfates have been widely used for phosphors for various applications such as phosphors for liquid crystal televisions, plasma televisions, phosphors for projectors, phosphors for lighting, etc., or electronic parts, fine ceramics, disks, superconductors, etc. ,Attention has been paid. The rare earth oxysulfate synthesis means of the present invention is suitable for mass production and cost reduction by a very unique process as described above, and will be used and implemented greatly in the future, thereby contributing to industrial development. It is expected.

The figure which shows the X-ray-diffraction pattern (a) of the product which concerns on Example 1, and the X-ray-diffraction pattern (b) of the yttrium oxysulfate recorded on the powder X-ray-diffraction database. X-ray diffraction pattern (a) of the product according to Example 1, X-ray diffraction pattern (b) of yttrium oxysulfate recorded in the powder X-ray diffraction database, and europium recorded in the powder X-ray diffraction database The figure which shows the X-ray-diffraction pattern (c) of an oxysulfate.

Claims (5)

  A rare earth oxysulfate characterized by mixing one or more kinds of rare earth oxides with a sulfur raw material while mechanically applying energy using a ball mill device, and heating the resulting milled product in air. Production method. The one or more kinds of rare earth oxides are rare earth sesquioxides represented by the general formula R ₂ O ₃ (R is a rare earth element), and the mixing ratio of the sulfur raw material to the rare earth sesquioxides is represented by the general formula R Based on the atomic ratio between the number of oxygen atoms N _(O) in the rare earth trioxide represented by ₂ O ₃ and the number of sulfur atoms N _(S) in the sulfur raw material, N _(O) / N _{(S The} method for producing a rare earth oxysulfate according to claim 1, wherein the ratio is set to 3 or less.   The method for producing a rare earth oxysulfate according to claim 1 or 2, wherein the sulfur raw material is granular or powdered elemental sulfur composed only of elemental sulfur.   The method for producing a rare earth oxysulfate according to claim 1 or 2, wherein the sulfur raw material is liquid carbon disulfide. The method for producing a rare earth oxysulfate according to claim 1, wherein a temperature at which the obtained milling product is heated in air is in a temperature range of 700 to 1000 ° C.

Images