JP2009184868A - Layered rare earth hydroxide and anion-exchange material and fluorescent material using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a layered rare earth hydroxide having a highly symmetric crystal structure and high crystallinity and to provide an anion-exchange material and a fluorescent material using it. <P>SOLUTION: The layered rare earth hydroxide is characterized by having a compositional formula of RE(OH)<SB>2.5</SB>Z<SB>0.5</SB>-0.125XH<SB>2</SB>O (wherein, 6<X<8; RE is a rare earth element; and Z is a halogen element). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a layered rare earth hydroxide, an anion exchange material using the same, and a fluorescent material.

  The layered material has a structure in which host layers spread in a two-dimensional direction through strong chemical bonds are stacked, and there are a wide variety of compounds. Further, it is known that the layered material exhibits reactivity (intercalation) for incorporating a different material (guest) between the layers.

Recently, a layered rare earth hydroxide has been reported as a layered material having anion exchange ability (see, for example, Non-Patent Document 1). According to Non-Patent Document 1, nitrate-type layered rare earth water represented by the composition formula Ln ₂ (OH) ₅ NO ₃ .xH ₂ O (Ln = Y, Gd to Lu, x≈1.5) is obtained by a hydrothermal method. An oxide is synthesized. Further, according to Non-Patent Document 1, nitrate ions in layered rare earth hydroxides undergo anion exchange with organic carboxylate and sulfonate ions, and Ln is weak in Tb and Dy but exhibits fluorescence. Is disclosed.

However, according to Non-Patent Document 1, in the nitrate-type layered rare earth hydroxide, an extremely large number of diffraction lines appear to be superimposed, suggesting that the symmetry of the crystal is low. Therefore, it is considered that it becomes a complicated crystal structure, and it is one of the causes that a quality crystal is not obtained. Moreover, the crystallinity is not sufficient. Therefore, a layered rare earth hydroxide having a higher symmetry crystal structure and higher crystallinity is desirable.
Further, according to Non-Patent Document 1, the rare earth element Ln in the layered rare earth hydroxide is limited to Y and Gd to Lu, and the layered rare earth hydroxide containing other rare earth elements, and also other than the nitric acid type In particular, a layered rare earth hydroxide containing Eu among rare earth elements can be expected to emit red light based on Eu.

McIntyre et al., Chem. Mater. , 20, 335-340 (2008)

  In view of the above, an object of the present invention is to provide a layered rare earth hydroxide having a highly symmetric crystal structure and high crystallinity, an anion exchange material and a fluorescent material using the same.

(Invention 1) The layered rare earth hydroxide according to the present invention is represented by the composition formula RE (OH) _2.5 Z _0.5 · 0.125XH ₂ O (6 <X <8), and the RE is a rare earth element. And Z is a halogen element.
(Invention 2) The layered rare earth hydroxide according to Invention 1, wherein the crystal system of the layered rare earth hydroxide belongs to an orthorhombic system.
(Invention 3) The layered rare earth hydroxide of Invention 1, which is a positively charged [RE ₈ (OH) ₂₀ (H ₂ O) _X ] ⁴⁺ layer and an intermediate layer Z ⁻ made of a negatively charged halogen element. And a laminated structure.
(Invention 4) The layered rare earth hydroxide according to Invention 1, wherein the halogen element Z is Cl or Br.
(Invention 5) The layered rare earth hydroxide according to Invention 1, wherein the RE is a rare earth element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Y. Features.
(Invention 6) The anion exchange material according to the present invention is characterized by comprising the layered rare earth hydroxide according to any one of Inventions 1 to 5 having an intermediate layer exchangeable with anions.
(Invention 7) The fluorescent material according to the present invention is characterized by comprising the layered rare earth hydroxide according to any one of Inventions 1 to 5 containing a rare earth element serving as an emission center.

The layered rare earth hydroxide according to the present invention is represented by the composition formula RE (OH) _2.5 Z _0.5 · 0.125XH ₂ O (6 <X <8), where RE is a rare earth element and Z is a halogen atom. It is an element. Since halogen ions are present as Z, the shape is simple and isotropic spheres compared to conventional bulky nitrate ions. As a result, a layered rare earth hydroxide having a highly symmetric crystal structure and high crystallinity is obtained. Z does not directly coordinate to RE, and thus exhibits anion exchange ability at room temperature. If such a layered rare earth hydroxide is used, a highly efficient anion exchange material can be provided. Since fluorescence is exhibited based on RE, a fluorescent material using the layered rare earth hydroxide of the present invention can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
The structure of the layered rare earth hydroxide according to the present invention will be described.

  FIG. 1 is a schematic diagram (A) and a crystal structure (B) of a layered rare earth hydroxide according to the present invention.

The layered rare earth hydroxide 100 according to the present invention has a composition formula RE (OH) _2.5 Z _0.5 · 0.125XH ₂ O (where RE is a rare earth element, Z is a halogen element, 6 <X <8). It is represented by For example, when RE is Eu, Z is Cl ⁻ , and X is 7, Eu (OH) _2.5 Cl _0.5 · 0.9H ₂ O is obtained.

  Rare earth elements RE are lanthanoids from lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71, scandium (Sc) with atomic number 21 and yttrium (Y) with atomic number 39. Is intended. In particular, it is preferable that RE is Eu since red light emission based on Eu is expected. Further, as shown in Examples 1 to 12 described later, the layered rare earth of the present invention is used in most rare earth elements (ie, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Y) that exhibit similar properties. Since the hydroxide was confirmed, it can be easily inferred that the layered rare earth hydroxide is similarly synthesized in Er, Tm, Yb and Lu.

  The halogen element Z is an element selected from the group consisting of fluorine, chlorine, bromine and iodine, and exists as ions. The shape of these halogen elements Z is simple and isotropic spherical. This can contribute to the improvement of the symmetry and crystallinity of the crystal structure of the layered rare earth hydroxide 100. In view of ease of production, the halogen element Z is more preferably chlorine or iodine, and most preferably chlorine.

  The reason why X has a range of 6 to 8 is that the number of water molecules slightly changes depending on the humidity. In the perfect state, X = 7.

More particularly, the layered rare earth hydroxide 100 comprises a positively charged [RE ₈ (OH) ₂₀ (H ₂ O) _x ] ⁴⁺ (6 <X <8) layer (or as shown in FIG. 1). (Also called a host layer) 110 and a negatively charged intermediate layer Z ^- 120. However, in either case, some carbonate ions are actually taken in from the air.

As shown in FIG. 1B, since the negatively charged intermediate layer Z ^- 120 is not directly coordinated to the RE, the intermediate layer Z ^- 120 can be easily exchanged for a different anion (ie, The layered rare earth hydroxide 100 has anion exchange ability). For example, when RE is Eu in the [RE ₈ (OH) ₂₀ (H ₂ O) _x ] ⁴⁺ layer 110 of the layered rare earth hydroxide 100 and the intermediate layer Z ^- 120 is Cl ⁻ , sulfate ions (alkali metal The above-described anion exchange occurs while maintaining the laminated structure of the layered rare earth hydroxide 100 only by bringing the layered rare earth hydroxide 100 into contact with the layered rare earth hydroxide 100 at room temperature.

  Further, the morphology of the layered rare earth hydroxide 100 according to the present invention is a plate shape (also referred to as a small plate) reflecting the layered structure described above, and more specifically, a rectangular plate shape. Such a shape is different from the hexagonal shape of Non-Patent Document 1, and from this point as well, the layered rare earth hydroxide 100 according to the present invention has a Z is simple and isotropic spherical halogen ion. It is suggested that it has a highly symmetric crystal structure and high crystallinity as compared with 1 nitrate type layered rare earth hydroxide. Note that such morphology depends on the degree of crystallinity. When the crystallinity is good, the edge becomes sharp, and when the crystallinity is low, the edge tends not to be sharp.

  Furthermore, the crystal system of the layered rare earth hydroxide 100 according to the present invention belongs to an orthorhombic system, more specifically to a simple orthorhombic lattice. From the above morphology and crystal structure, whether or not the obtained product is a layered rare earth hydroxide is simply determined whether or not the platelet is confirmed by surface observation with an electron microscope. This can be determined by indexing the X-ray diffraction pattern of the product.

  In addition, RE is known to exhibit luminescent properties, magnetic properties and high catalytic activity. Also in the layered rare earth hydroxide 100 of the present invention, in addition to the anion exchange ability, the light emission characteristics, magnetism and catalytic activity based on the contained RE are exhibited, and applications using them (anion exchange materials, light emitting materials, magnetic materials) Etc.) is expected.

(Embodiment 2)
Although the manufacturing method of the layered rare earth hydroxide according to the present invention is not particularly limited, it can be manufactured by a uniform precipitation method as an example. The layered rare earth hydroxide according to the present invention comprises, for example, hexamethylenetetramine (HMT) or urea in a mixed aqueous solution comprising a rare earth element halide, hexamethylenetetramine (HMT) or urea, and a solvent containing water. It is obtained by decomposing and hydrolyzing rare earth halides. For convenience, the preparation of the mixed aqueous solution and the hydrolysis of the rare earth element halide will be described separately. This will be described in detail with reference to the flowchart.

  FIG. 2 is a flow chart illustrating steps for producing an exemplary layered rare earth hydroxide according to the present invention.

  This will be described in detail for each step.

Step S210: A mixed aqueous solution containing a halide of RE (hereinafter simply referred to as REZ ₃ ), hexamethylenetetramine (hereinafter simply referred to as HMT) or urea, and a solvent containing water is prepared. RE and Z are the rare earth element and the halogen element described in the first embodiment, respectively.

The solvent containing water may be water (for example, ultrapure water) alone, or a nonaqueous solvent such as ethanol may be used in addition to water, but at least water is sufficient. This is because the reaction is promoted by hydration of rare earth ions with water. Since at least water is sufficient, a hydrate of REZ ₃ may be used together with a solvent containing water.

Both HMT and urea function to increase the pH of the mixed aqueous solution after decomposition. Preferably, the molar ratio of REZ ₃ to HMT or urea is 0.75. If this ratio is not satisfied, impurities such as RE (OH) ₃ and RE (OH) ₂ Cl may be generated.

The pH of the mixed aqueous solution is, for example, in the range of 5.5 to 6.5 when RE is an element selected from the group consisting of Nd, Eu, Gd, Tb, Dy, Ho, and Y. In this range, rises until the pH of the mixed aqueous solution in step S220 is 8 to 10 described below, to promote the hydrolysis REZ _3, it is possible to reliably obtain a layered earth hydroxides. On the other hand, when RE is La, the pH of the mixed aqueous solution is preferably set to be lower than the above range and in the range of 4.5 or more and less than 5.5. This is because in the rare earth series, the basicity increases as the size increases, that is, toward the La side, and RE (OH) ₃ tends to be generated. In order to suppress this, it is effective to generate a layered hydroxide to set the pH lower. In addition, what is necessary is just to add acids, such as HCl suitably, for such adjustment of pH. The pH of the mixed aqueous solution is appropriately adjusted according to the RE selected in this way.

In step S210, an alkali metal halide may be further mixed in the mixed aqueous solution. Examples of the alkali metal halide include NaCl and KCl, but are not limited thereto. This promotes synthesis even under conditions where the concentration of REZ ₃ is low. As a result, the morphology or crystallinity of the obtained layered rare earth hydroxide can be improved.

Step S220: HMT or urea in the mixed aqueous solution obtained in step S210 is decomposed, and REZ ₃ is hydrolyzed.

HMT and urea are decomposed to produce ammonia. Thereby, pH of mixed aqueous solution rises and it becomes alkaline. As a result, REZ ₃ is hydrolyzed and a layered rare earth hydroxide precipitates. Both HMT and urea (preferably by heating) produce ammonia slowly at a controlled rate, so there is no bias in nucleation and crystallization, and high quality layered rare earth water with uniform grain size and high crystallinity. An oxide is obtained.

  The decomposition of HMT and urea is performed, for example, by stirring the mixed aqueous solution obtained in step S210 at room temperature for a long time. From the viewpoint of efficiency, it is preferable to heat the mixed aqueous solution while stirring at a temperature of 70 ° C. or higher. . Thereby, since decomposition | disassembly of HMT and urea is accelerated | stimulated, a synthesis | combination advances efficiently. Crystal formation can be visually confirmed by heating for 30 minutes to 1 hour, but typically heating is performed for 6 hours to 10 hours. In particular, heating for 8 hours or more is preferable because the crystallinity of the layered rare earth hydroxide is improved. Moreover, although the upper limit of heating temperature changes with solvents to be used, it is the temperature which does not exceed 100 degreeC.

  Subsequent to step S220, the obtained layered rare earth hydroxide may be washed and dried at room temperature. This makes it possible to obtain a powdery layered rare earth hydroxide that is easy to handle. Washing is repeated several times with water and ethanol.

  Thereby, the layered rare earth hydroxide of the present invention is obtained. The method for producing the layered rare earth hydroxide of the present invention is not limited to the homogeneous precipitation method described with reference to FIG. 2, but a dedicated high pressure apparatus such as an autoclave is not necessary if the homogeneous precipitation method is used. This is advantageous because the layered rare earth hydroxide can be provided inexpensively and in large quantities.

  Next, examples will be described, but it should be noted that the present invention is not limited to the examples.

And _{EuCl 3 · 6H 2 O (5mM} ) as REZ _3, the HMT (3.75 mM), and NaCl (65 mM) were dissolved in ultrapure water 1000 ml, the final concentration was prepared a mixed aqueous solution of 5.65 mm ( Step S210 in FIG. Here, the rare earth element halide has six water molecules, but since the rare earth element halide is hygroscopic, it is known to vary between 6 and 7 depending on the environment. The same applies to the following embodiments. The pH of the mixed aqueous solution thus obtained was about 6. Next, the mixed aqueous solution was stirred with a magnetic stirrer and heated at a reflux temperature (about 100 ° C.) in nitrogen gas. Thereby, HMT was decomposed | disassembled (step S220 of FIG. 2). At this time, the pH of the mixed aqueous solution rose to about 8. These operations were performed using a two-necked flask equipped with a reflux condenser under a nitrogen flow.

  After 1 hour, white streamlines were observed in the mixed solution. This suggests that an anisotropic shaped crystal was formed. The product was then filtered, washed several times with water and ethanol, and dried at room temperature.

  The morphology and structure of the product thus obtained were observed using a scanning electron microscope SEM (JEOL, JSM-6700F) and a transmission electron microscope TEM (JEOL, JEM-1010). The observation results are shown in FIGS. 3 and 4 and will be described later. Moreover, the limited-field diffraction pattern (SAED) was obtained from the product put on the copper grid using TEM. The results are shown in FIG.

  The structure of the product was evaluated using X-ray diffraction. X-ray diffraction was measured with a Rigaku Rint-2000 diffractometer equipped with a Cu counter cathode (Cu—Kα ray) (λ = 1.5405 ＝). For further structural analysis, high-resolution synchrotron powder X-ray diffraction data was obtained using the beam line BL15 (λ = 0.65297Å) of the large synchrotron radiation facility (Spring 8). The respective results are shown in FIGS. 6 and 7 and will be described later.

Subsequently, structure determination was performed using the result of FIG. The structure was determined by the following procedure. First, the integrated intensity was extracted from the XRD pattern of FIG. 7 using the Le Bail method. The extracted integrated intensity was redistributed by the maximum entropy Patterson program ALBA to obtain a more reliable value. The obtained structural factors were directly introduced into the method program EXPO 2004, and the positions of rare earth atoms were determined. The positions of other atoms were obtained by electron density distribution analysis by MEM / Rietveld. Finally, the structure was refined using the Rietan-FP program. The electron density distribution was obtained by MEM using the structure factor F ₀ value obtained by the PRIMA program. If additional peaks were found in the electron density distribution, the structural model was modified and refinement was repeated until no further decrease in reliability factor (R factor) was visible. These results are shown in FIGS. 8 to 11 and Table 2 and will be described in detail.

  Elemental analysis of the product was performed. The amount of Eu was measured using an inductively coupled plasma (ICP) atomic emission spectrometry (Seiko SPS1700HVR) after dissolving the sample in an aqueous hydrochloric acid solution. The amount of OH in the product was determined by neutralizing titration with NaOH after dissolving a precisely weighed sample in sulfuric acid (0.1 mol). The amount of Cl in the product was determined by the ion electrode method. At this time, DKK IM-40S was used as a concentration meter, DKK CL-125B was used as an ion electrode, and DKK RE-2 was used as a reference electrode. The C content in the product was determined with a LECO RC-412 analyzer. The water content in the product was determined by thermogravimetric analysis. The results of elemental analysis of the obtained product will be described later with reference to FIGS.

  The emission characteristics of the product were examined. Excitation and emission spectra at room temperature were measured using a fluorescence spectrophotometer (Hitachi F-4500). The measurement results are shown in FIG.

Next, the anion exchange ability of the product was examined. A sample (0.2 g) was added to a NaNO ₃ aqueous solution (1 M, 200 cm ³ ), a Na ₂ SO ₄ aqueous solution (1 M, 200 cm ³ ), and a sodium dodecyl sulfate (C ₁₂ H ₂₅ OSO ₃ Na) aqueous solution (0.5 M, 200 cm). ³ ) Each was dispersed. The reaction vessel containing each mixed aqueous solution was sealed and shaken at room temperature for 2 days. Two days later, samples were collected from each reaction vessel.

  The structural evaluation of the collected sample was performed using X-ray diffraction. X-ray diffraction was measured with a Rigaku Rint-2000 diffractometer equipped with a Cu counter cathode (Cu—Kα ray) (λ = 1.5405 ＝). The results are shown in FIG. 13 and will be described later. The morphology of the collected sample was observed using SEM. The observation results are shown in FIGS.

The recovered sample was subjected to Fourier transform infrared spectroscopic analysis (FT-IR), and qualitative analysis was performed as to whether or not anion exchange was performed. The measurement was performed by the KBr pellet method using a Varian 7000e FT-IR spectrophotometer equipped with an MCT detector in a wave number range of 400 to 4000 cm ⁻¹ . The results are shown in FIG.

In Example 1, the product was obtained by the same procedure except that YCl ₃ · 6H ₂ O (5 mM) was used as REZ ₃ . For the obtained product, XRD and SEM were measured in the same manner as in Example 1. The results are shown in FIGS. 18 and 19 and will be described later.

In Example 1, the product was obtained by the same procedure except that SmCl ₃ · 6H ₂ O (5 mM) was used as REZ ₃ . For the obtained product, XRD and SEM were measured in the same manner as in Example 1. The results are shown in FIGS. 20 and 21 and will be described later.

In Example 1, the product was obtained by the same procedure except that GdCl ₃ · 6H ₂ O (5 mM) was used as REZ ₃ . For the obtained product, XRD and SEM were measured in the same manner as in Example 1. The results are shown in FIGS. 22 and 23 and will be described later.

In Example 1, the product was obtained by the same procedure except that TbCl ₃ · 6H ₂ O (5 mM) was used as REZ ₃ . For the obtained product, the XRD, SEM and excitation / emission spectrum were measured in the same manner as in Example 1. The results are shown in FIGS.

In Example 1, the product was obtained by the same procedure except that DyCl ₃ · 6H ₂ O (5 mM) was used as REZ ₃ . For the obtained product, XRD and SEM were measured in the same manner as in Example 1. The results are shown in FIGS. 27 and 28 and will be described later.

In Example 1, except for using _{HoCl 3 · 6H 2 O (5mM} ) as REZ ₃ was obtained the product by the same procedure. For the obtained product, XRD and SEM were measured in the same manner as in Example 1. The results are shown in FIGS. 29 and 30 and will be described later.

In Example 1, the product was obtained by the same procedure except that NdCl ₃ · 6H ₂ O (5 mM) was used as REZ ₃ . For the obtained product, XRD and SEM were measured in the same manner as in Example 1. The results are shown in FIGS. 31 and 32 and will be described later.

And _{LaCl 3 · 6H 2 O (5mM} ) as REZ _3, the HMT (3.75 mM), and NaCl (65 mM) were dissolved in ultrapure water 1000 ml, to obtain a mixed aqueous solution. HCl (0.1 M) was further added to the mixed aqueous solution to adjust the mixed aqueous solution to have a pH of 5 (step S210 in FIG. 2). Next, the mixed aqueous solution was stirred with a magnetic stirrer and heated at a reflux temperature (about 100 ° C.) in nitrogen gas. Thereby, HMT was decomposed | disassembled (step S220 of FIG. 2). These operations were performed using a two-necked flask equipped with a reflux condenser under a nitrogen stream.

  After 1 hour, white streamlines were observed in the mixed solution. This suggests that an anisotropic shaped crystal was formed. The product was then filtered, washed several times with water and ethanol, and dried at room temperature. For the obtained product, XRD was measured in the same manner as in Example 1. The results are shown in FIG. 33 and will be described later.

In Example 5, a product was obtained by the same procedure except that NaCl was not used and the concentration of TbCl ₃ .6H ₂ O was changed to 5 mM, 10 mM, 15 mM, 25 mM, and 50 mM. For the products obtained from each concentration, XRD was measured in the same manner as in Example 5. The results are shown in FIG. 34 and will be described later.

  In Example 5, a product was obtained by the same procedure except that NaCl was not used and a mixed solvent of ethanol and water (ethanol: water = 9: 1) was used instead of ultrapure water. . For the obtained product, XRD was measured in the same manner as in Example 5. The results are shown in FIG. 35 and will be described later.

In Example 5, a product was obtained by the same procedure except that TbBr ₃ · 6H ₂ O (5 mM) and NaBr (65 mM) were used instead of TbCl ₃ · 6H ₂ O and NaCl, respectively. The XRD and SEM of the obtained product were measured in the same manner as in Example 5. The results are shown in FIGS. 36 and 37 and will be described later.

Comparative Example 1

In place of EuCl ₃ in Example 1, EuNO ₃ .6H ₂ O (5 mM), HMT (3.75 mM), and NaNO ₃ (65 mM) were dissolved in 1000 ml of ultrapure water to give a final concentration of 5.65 mM. Was prepared (step S210 in FIG. 2). Here, as in Example 1, the rare earth element nitrate has six water molecules, but since the rare earth element nitrate is hygroscopic, it is understood that it varies between 6 and 7 depending on the environment. Yes. Next, the mixed aqueous solution was stirred with a magnetic stirrer and heated at a reflux temperature (about 100 ° C.) in nitrogen gas. Thereby, HMT was decomposed | disassembled (step S220 of FIG. 2). These operations were performed using a two-necked flask equipped with a reflux condenser under a nitrogen stream.

  After 1 hour, white streamlines were observed in the mixed solution. This suggests that an anisotropic shaped crystal was formed. The product was then filtered, washed several times with water and ethanol, and dried at room temperature.

The XRD and SEM of the obtained product were measured in the same manner as in Example 1. The results are shown in FIGS. 38 and 39 and will be described later.
Table 1 shows the experimental conditions and results of Examples 1 to 12 and Comparative Example 1 described above.

  Since the intensity (count value) of the XRD pattern, excitation spectrum, and emission spectrum varies depending on the measurement apparatus and conditions, the unit is an arbitrary unit. That is, it should be noted that the comparison can be made only within the present example measured under the same conditions.

  FIG. 3 is a SEM image of the product of Example 1.

  4 is a TEM image of the product of Example 1. FIG.

From FIG. 3 and FIG. 4, it was confirmed that the obtained product was a rectangular plate (platelet). Moreover, it turned out that it is a uniform magnitude | size over the whole product from FIG. From FIG. 4, the morphology (plate thickness) of the rectangular platelet was about 20 nm. In addition, the size of one rectangular small plate was about 2 μm in the longitudinal direction and about 1 μm in the short direction. These characteristics strongly suggest that a layered rare earth hydroxide having an intermediate layer Z ^- 120 (FIG. 1) of Cl ⁻ was obtained.

  FIG. 5 is a diagram showing the SAED pattern (A) of Example 1 and the relationship (B) between the basic unit cell and the superlattice.

FIG. 5A shows two sets of spot groups having different luminances. This suggests that a superlattice structure is formed. Specifically, the brighter spots forming the hexagons correspond to hexagonal symmetric elementary unit cells (a _f = 3.7Å). Meanwhile, a darker spot to form a rectangle, rectangular superlattice _{(a s = 2√3Å, a f} = 13.1Å, b s = 2a f = 7.4Å) corresponds to. The relationship between these basic unit lattices and superlattices is schematically shown in FIG. The basic unit cell (hexagonal unit cell) indicates a hexagonal arrangement of rare earth atoms (Eu in this case), and is a brucite type (Mg (OH) ₂ ) or a layered double hydroxide LDH type ([M ²⁺ _α M ³⁺ _1-α (OH) ₂ ] ^1-α (α is a rational number not exceeding 1)) is implied by the similarity to the host layer structure. It is considered that a rectangular superlattice is formed by the deviation from the ideal brucite structure atomic position.

  6 is a diagram showing an XRD pattern of the product of Example 1. FIG.

  The XRD pattern is composed of sharp diffraction peaks, indicating that the product has high crystallinity. In particular, the very strong peaks at about 10.6 ° and about 21.2 ° in the low angle region imply that the resulting product is a layered material. Next, the crystal structure of the product of Example 1 was examined in more detail.

  7 is a high resolution synchrotron powder X-ray diffraction (XRD) pattern of the product of Example 1. FIG.

  The peaks seen in the XRD pattern in FIG. 7 were all orthorhombic, and more specifically, simple orthorhombic lattices could be indexed. In particular, the peak intensity of 001 reflection and 002 reflection was stronger than other peak intensities. It was confirmed that these peaks corresponded to the peaks at about 10.6 ° and about 21.2 ° in FIG. The lattice constants a, b and c of the simple orthorhombic lattice were a = 12.92 (1) Å, b = 7.38 (1) Å and c = 8.71 (1) Å, respectively. The ratio of a and b did not completely match √3. This suggests that the above-described hexagonal symmetric basic unit cell is not completely hexagonal symmetric as in an ideal bullsite structure.

  A and b obtained from FIG. 7 matched well with a and b obtained from the SAED pattern of FIG. This is because the platelets seen in FIG. 4 are located on the {001} crystal plane, and the SAED pattern of FIG. 5 (A) was taken along the [001] direction, that is, along the z-axis. It shows that.

As a result of the composition analysis, it was found that the elemental composition was Eu (OH) _2.36 Cl _0.51 (CO ₃ ) _0.065 · 0.87H ₂ O. From the results of indexing in the XRD pattern of FIG. 7, it was found that a series of peaks of h = 2n + 1 (in the case of h00) and k = 2n + 1 (in the case of 0k0) disappeared. This suggests that the product space group is P2 ₁ 2 ₁ 2. Further, as a result of intensity extraction by the Le Bail method, the space groups P2 ₁ 2 ₁ 2 matched best. From the above, it was concluded that the product space group was P2 ₁ 2 ₁ 2.

Next, as described with reference to FIG. 5, since eight Eu exist in the unit cell, Z = 8 and the unit formula is Eu ₈ (OH) _18.88 Cl _4.08 (CO _{3 0.52} · 6.96H ₂ O For simplicity, transferred charge of carbonate ion to hydroxide ion, the unit formula was _{Eu 8 (OH) 20 Cl 4} · 7.0H 2 O. First, the direct method using the program EXPO 2004 was applied to determine the atomic positions of 8 Eu. Other light element species (OH, H ₂ O, Cl) were determined by electron density distribution analysis employing MEM / Rietveld of the maximum entropy method. From this result, a layered crystal structure model was generated.

  FIG. 8 is a schematic diagram of a layered crystal structure model.

  The left diagram in FIG. 8 is a layered crystal structure model projected from the [001] direction, and the right diagram in FIG. 8 is a layered crystal structure model in the [010] direction. Based on these crystal structure models, the structural parameters were refined from the Rietan-FP program. The result is shown in FIG.

  FIG. 9 is a diagram showing a Rietveld pattern of the product in Example 1.

FIG. 9 shows experimental values, calculated values, and differences. Satisfactory pattern fitting was achieved as shown in FIG. The final confidence factor (R factor) is R _wp = 2.04% (S = 0.5167), R _p = 1.52%, R _I = 3.98% and R _F = 1.65%. It became. These extremely small R factors suggest that the layered structure model shown in FIG. 8 is valid. Table 2 shows the structural parameters obtained as a result of the refinement.

In Table 2, the numbers in parentheses are standard deviations. The space group is P2 ₁ 2 ₁ 2 and the lattice constants a, b and c are a = 12.9155 (3) Å, b = 7.3763 (1) Å and c = 8.70223 (3) （, respectively. Met. All temperature factors ( _Biso ) were fixed at 1.0 ² for the Eu site and 2.0 ² for the other species. In the final stage, the water molecule occupancy was fixed according to the elemental composition determined by elemental analysis. Further, the Eu3 site is a space group in which P2 ₁ 2 ₁ 2 does not have a symmetric center, and thus is fixed at a value obtained from the direct method.

  FIG. 10 is a diagram showing an electron density distribution.

According to the illustration of the result of the electron density distribution analysis of FIG. 10, the electron density distribution matched well with the layered crystal structure model of FIG. A remarkable feature is that the electron density corresponding to the intermediate layer Cl ⁻ exhibits a substantially spherical distribution. This is because Cl ⁻ is also well arranged between the layers, and has characteristics different from other layered double hydroxides in which intermediate layer anions are often arranged randomly.

From the above results, it was shown that the structure of the product obtained in Example 1 was the layered rare earth hydroxide described with reference to FIG. Specifically, the layered rare earth _hydroxides, RE _{(OH) 2.5} meets Cl 0.5 · 0.9H ₂ O of composition formula, positively charged _{[Eu 8 (OH) 20 (} H 2 O) ₇ ] It consists of a ⁴⁺ layer and a negatively charged intermediate layer Cl ⁻ located between the layers. Thereby, the charge is compensated and stabilized.

  Next, coordination of Eu cation sites will be described. The Eu cation has an 8-coordinate, ie, 4c (0.2736, 0.2503, 0.9349) position with seven hydroxyl groups and one water molecule, and a nine-coordinate, ie, eight hydroxyl groups and one water molecule. There are three patterns with accompanying 2a (0, 0, 0.9194) sites or 2b (0, 0.5, 0.9324) positions.

  FIG. 11 is a diagram showing the coordination environment of Eu in the product in Example 1.

FIG. 11 schematically shows the coordination environment of the three different Eu sites described above. In any coordination, all the hydroxyl groups are bonded to Eu at a distance of 2.1 to 2.6. In addition, the distance between H ₂ O and Eu in 8-coordinate and 9-coordinate was 2.35 (2) Å, 2.65 (6), and 2.45 (5) Å, respectively. Eu coordinated with these hydroxyl groups and H ₂ O molecules is chained in a two-dimensional direction, and a layer parallel to the ab plane as shown at 110 in FIG. 1 is generated.

  The deviation of the Eu position from the ideal in-plane hexagonal arrangement was in good agreement with the SAED results. This is because although the hexagonal symmetrical basic unit cell is substantially recognized in the actual structure, the position of Eu undulates in the [001] direction, that is, the z-axis direction, and is also distorted in the ab plane. This is because the details are a simple orthorhombic superlattice. From the above, it has been found that the crystal system of the layered rare earth hydroxide containing Cl ions between the layers of the present invention belongs to orthorhombic crystal, and specifically has a simple orthorhombic superlattice structure.

  12 shows the excitation spectrum (A) and emission spectrum (B) of the product of Example 1. FIG.

12 (A) shows the observed emission wavelength 612 nm ^- a excitation spectrum when the ⁽⁵ _D 0 7 _{F 2} line), FIG. 12 (B) when excited with 395nm (intra-4f ⁶ direct excitation) Is an emission spectrum. The excitation spectrum showed multiple sharp peaks due to the intra-4f ⁶ transition in the Eu ³⁺ 4f ⁶ electron configuration. Emission spectra, 578.4nm, 594.6nm, 612.4nm, the 649.0nm and 696.8nm, typical ⁵ D ₀ - showed ⁷ F _{j (j} = ^0~4) transition. Fluorescence from higher excitation levels such as ⁵ D ₁ was not detected. This suggests that very efficiently non-radiative relaxation to ⁵ D ₀ level.

⁵ D ₀ in FIG. _{^{12 (B) - 7 F j}} (j = 0~4) emission peak intensity of the transition, and, by using the division of these emission peaks, were examined ^{Eu 3+} ions environment. According to FIG. 12 (B), ⁵ D ₀ to about 612 nm - showed the strongest emission peak of ⁷ F ₂ transition. Theoretically, ^{Eu 3+} If the the inversion symmetry in the crystal lattice, the magnetic dipole transition ⁵ D ₀ at about 590 nm - ⁷ F ₁ becomes a major emission peak, otherwise, at about 610nm~620nm electric dipole transition ⁵ D ₀ - ⁷ F ₂ becomes the major emission peak. This suggests that Eu ³⁺ in the layered rare earth hydroxide of Example 1 does not have inversion symmetry, that is, has no inversion center.

In addition, according to FIG. _{^{12 (B), 5 D 0}} - 7 F 1 transition and ⁵ D ₀ - ⁷ F ₂ emission peak by the transition, respectively, and the peak split into three and two. This suggests that the symmetry of the crystal field around Eu ³⁺ is low. These results were in good agreement with the crystal structure analysis results. As described with reference to FIG. 11, Eu ³⁺ has two local coordinations, namely an 8-coordinate 4c position in the point group C ₁ and a 9-coordinate 2a and 2b in the point group C _4ν . Both of the Eu ³⁺ coordinations (ie, the three positions) belong to low symmetry with no inversion center.

As described above, typical Eu ³⁺ emission (red emission) was confirmed from the excitation spectrum and emission spectrum of FIG. This suggests that RE (here, Eu) functions as a luminescent center in the product of the present invention, and is applicable to fluorescent materials and further to light emitting devices.

  FIG. 13 is a diagram showing an XRD pattern after anion exchange of the product of Example 1.

  FIG. 13 also shows an XRD pattern of a sample (including Cl ions between layers) before anion exchange for reference. The XRD pattern of the product after anion exchange showed a clear peak shift.

The interlayer distance before anion exchange was 8.63 mm. On the other hand, the interlayer distance of the product after anion exchange with sodium nitrate (NO ₃ ⁻ ), sodium sulfate (SO ₄ ²⁻ ), and sodium dodecyl sulfate (C ₁₂ H ₂₅ OSO ₃ ⁻ ) was 8.32 cm, 8 Changed to .94 cm and 23.6 cm.

  In addition, the XRD pattern of the product after anion exchange maintained a sharp diffraction peak, and it was found that high crystallinity was maintained by the process during anion exchange.

14 is a diagram showing an SEM image of the product after anion exchange with sodium nitrate (NO ₃ ⁻ ) in Example 1. FIG.

15 is a diagram showing an SEM image of the product after anion exchange with sodium sulfate (SO ₄ ²⁻ ) in Example 1. FIG.

16 is a diagram showing an SEM image of the product after anion exchange with sodium dodecyl sulfate (C ₁₂ H ₂₅ OSO ₃ ⁻ ) in Example 1. FIG.

  Comparing the SEM image of the product before the anion exchange of Example 1 in FIG. 3 with the SEM images of FIGS. 14 to 16, the product after the anion exchange is also a rectangular platelet in the product before the anion exchange. It was found to maintain the morphology of. This also shows that high crystallinity and crystal structure are maintained by the process during anion exchange.

  17 is a diagram showing an FT-IR absorption spectrum of the product after anion exchange in Example 1. FIG.

FIG. 17 also shows the FT-IR absorption spectrum (a) of the product before anion exchange for reference. Any spectrum (a) ~ (d) also, about 3500 cm ^-1, and an absorption band at about 1650 cm ^-1 and about 620 cm ^-1. The absorption band of about 3500 cm ⁻¹ is due to the O—H bond and the stretching vibration of ν (OH), and suggests that hydroxide ions due to the metal-OH layer exist in the crystal. The absorption band of about 1650 cm ⁻¹ is due to the expansion / contraction mode of water molecules. The absorption band of about 620 cm ⁻¹ is caused by Eu / O stretching / deformation vibration.

Further, the FT-IR absorption spectrum of FIG. 17 also shows an absorption band due to the type of the intermediate layer Z ⁻ . Specifically, the FT-IR absorption spectrum (b) of the product after anion exchange with sodium nitrate (NO ₃ ⁻ ) showed sharp and strong absorption at 1385 cm ⁻¹ and 1410 cm ⁻¹ . These are each, NO ₃ ^- anions _{D 3h,} [nu ₃ vibration mode, and, O-NO ₂ of _{C 2v,} due to _ν4 asymmetric stretching mode. These absorption bands were not found in the spectrum (a) before the reaction.

The FT-IR absorption spectrum (c) of the product after anion exchange with sodium sulfate (SO ₄ ²⁻ ) showed absorption at 1120 cm ⁻¹ due to SO ₄ ²⁻ . This absorption band was not seen in spectrum (a).

Sodium dodecyl sulfate ^{_{(C 12 H 25 OSO 3 -}} ) FT-IR absorption spectrum of the by product after anion exchange (d) is a strong absorption at 2920 cm ^-1 and 2850cm ^-1, 2958cm ^-1, 1470cm ^-1 and Relatively weak absorption was shown at 1300 cm ^{−1 to} 900 cm ⁻¹ . The absorptions at 2920 cm ⁻¹ and 2850 cm ⁻¹ are attributed to asymmetric CH ₂ stretching vibration and symmetric CH ₂ stretching vibration in the alkyl chain of dodecyl sulfate, respectively. Further, the relatively weak absorption at 2958 cm ⁻¹ is attributed to the stretching vibration of the CH ₃ group which is a hydrocarbon end group. The relatively weak absorption near 1470 cm ⁻¹ is due to the CH ₂ bending (or scissor) mode. ^Furthermore, a series of weak absorption in 1300cm ^-1 ~900cm -1 is sulfate ^- due to the expansion and contraction mode (OSO _3). These absorption bands were not found in spectrum (a).

Thus, it was found that the product of the present invention can be easily anion-exchanged at room temperature and maintain high crystallinity and crystal structure (layered structure) even after anion exchange. The above results indicate that the intermediate layer 120 (here, the Cl ⁻ layer) functions as a counter anion, as described with reference to FIG. When the layered rare earth hydroxide of the present invention is used as an anion exchange material, it is suggested that anion exchange can be performed with high efficiency at room temperature.

  18 is a diagram showing an XRD pattern of the product of Example 2. FIG.

The XRD pattern of FIG. 18 is similar to the XRD pattern of FIG. 6 in addition to strong peaks at about 10.6 ° and about 21.2 °, all other peaks are layered rare earth hydroxide (RE (OH) _{2 .5} Z _0.5 · 0.9 H ₂ O). From this, the product of Example 2 is a Y (OH) _2.5 Cl _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H _This shows that a layered rare earth hydroxide in which RE is Y in the ₂ O) _x ] ⁴⁺ layer 110 and the intermediate layer Z ⁻ 120 is Cl ⁻ is obtained.

  19 is a view showing an SEM image of the product of Example 2. FIG.

FIG. 19 shows a morphology in which rectangular platelets typical of layered rare earth hydroxides in which the intermediate layer Z ^- 120 (FIG. 1) is Cl ⁻ are aggregated. This also suggests that a layered rare earth hydroxide was obtained.

  20 shows the XRD pattern of the product of Example 3. FIG.

The XRD pattern of FIG. 20 is similar to the XRD pattern of FIG. 6, in addition to the strong peaks at about 10.6 ° and about 21.2 °, all other peaks are layered rare earth hydroxide (RE (OH) _{2 .5} Z _0.5 · 0.9 H ₂ O). From this, the product of Example 3 is a single phase of Sm (OH) _2.5 Cl _0.5 · 0.9 H ₂ O, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is Sm, the intermediate layer ^Z - 120 are Cl ^- layered earth hydroxides it is indicated that the obtained a.

  21 is a SEM image of the product of Example 3. FIG.

From FIG. 21, the morphology of the product of Example 3 is similar to the morphology of the product of Example 1, the intermediate layer Z ^- 120 are Cl ^- typical small rectangular layered rare earth hydroxide is A plate was obtained uniformly throughout the product. This also suggests that the layered rare earth hydroxide was obtained in a single phase.

  22 shows the XRD pattern of the product of Example 4. FIG.

The XRD pattern of FIG. 22 is similar to the XRD pattern of FIG. 6 in addition to strong peaks at about 10.6 ° and about 21.2 °, all other peaks are layered rare earth hydroxide (RE (OH) _{2 .5} Cl _0.5 · 0.9 H ₂ O). From this, the product of Example 4 is a Gd (OH) _2.5 Cl _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is Gd, intermediate layer ^Z - 120 are Cl ^- layered earth hydroxides it is indicated that the obtained a.

  23 is a view showing an SEM image of the product of Example 4. FIG.

From FIG. 23, the intermediate layer Z ^- 120 are Cl ^- morphology typical rectangular platelets are aggregated in a layered earth hydroxide is is shown. This also suggests that a layered rare earth hydroxide was obtained.

  FIG. 24 shows the XRD pattern of the product of Example 5.

The XRD pattern of FIG. 24 is similar to the XRD pattern of FIG. 6 in addition to the strong peaks at about 10.6 ° and about 21.2 °, all other peaks are layered rare earth hydroxide (RE (OH) _{2 .5} Cl _0.5 · 0.9 H ₂ O). From this, the product of Example 5 is a Tb (OH) _2.5 Cl _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is Tb, the intermediate layer ^Z - 120 are Cl ^- layered earth hydroxides it is indicated that the obtained a.

  FIG. 25 is a view showing an SEM image of the product of Example 5.

From FIG. 25, the intermediate layer Z ^- 120 are Cl ^- morphology typical platelets are aggregated in a layered earth hydroxide is is shown. This also suggests that a layered rare earth hydroxide was obtained.

  FIG. 26 shows the excitation / emission spectrum of the product of Example 5.

FIG. 26 shows an excitation spectrum when the observed emission wavelength is 543 nm and an emission spectrum when excited at 252 nm. Emission of a typical ^{Tb 3+} (green light emission) ^is, _{5 D} 4 ^- 7 _F 5 was confirmed to 543m by the transition. In the product of the present invention, RE (here, Tb) functions as an emission center, suggesting that it can be applied to fluorescent materials and further to light emitting devices.

  FIG. 27 is an XRD pattern of the product of Example 6.

The XRD pattern of FIG. 27 is similar to the XRD pattern of FIG. 6 in addition to strong peaks at about 10.6 ° and about 21.2 °, all other peaks are layered rare earth hydroxide (RE (OH) _{2 .5} Z _0.5 · 0.9 H ₂ O). From this, the product of Example 6 is a Dy (OH) _2.5 Cl _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is Dy, intermediate layer ^Z - 120 are Cl ^- layered earth hydroxides it is indicated that the obtained a.

  28 is a SEM image of the product of Example 6. FIG.

FIG. 28 shows a morphology in which platelets typical of a layered rare earth hydroxide are aggregated although the size is not uniform. Moreover, the shape was partially broken, and the shape was rectangular. This also intermediate layer Z ^- 120 are Cl ^- that the layered rare earth hydroxides is obtained is suggested that.

  FIG. 29 is a diagram showing an XRD pattern of the product of Example 7. FIG.

The XRD pattern of FIG. 29 is similar to the XRD pattern of FIG. 6 in addition to the strong peaks at about 10.6 ° and about 21.2 °, all other peaks are layered rare earth hydroxide (RE (OH) _{2 .5} Z _0.5 · 0.9 H ₂ O). From this, the product of Example 7 is a Ho (OH) _2.5 Cl _0.5 · 0.9 H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is Ho, intermediate layer ^Z - 120 are Cl ^- layered earth hydroxides it is indicated that the obtained a.

  30 is a SEM image of the product of Example 7. FIG.

From FIG. 30, although a part shape is collapsed, the intermediate layer Z ^- 120 are Cl ^- morphology typical rectangular platelets are aggregated in a layered earth hydroxide is is shown. This also suggests that a layered rare earth hydroxide was obtained.

  FIG. 31 shows the XRD pattern of the product of Example 8.

The XRD pattern of FIG. 31 is similar to the XRD pattern of FIG. 6 in that the layered rare earth hydroxide (RE (OH) _2.5 Z _{0 at} about 10.6 ° and about 21.2 ° is the same as in Example 1. _.5 · 0.9H ₂ O) showed a typical peak, but a part of the peak showing Nd (OH) ₃ was also observed. From this, it was found that the product of Example 8 was a mixture of Nd (OH) _2.5 Cl _0.5 · 0.9H ₂ O and Nd (OH) ₃ . As a result of structural refinement, it was found that the amount of Nd (OH) ₃ produced was 10% or less, and Nd (OH) _2.5 Cl _0.5 · 0.9H ₂ O was the main product.

  32 is a SEM image of the product of Example 8. FIG.

FIG. 32 shows a needle-like piece in addition to the morphology of platelets typical of layered rare earth hydroxide. In particular, the shape of the platelet was rectangular. This also indicates that the product of Example 8 is a mixture of Nd (OH) _2.5 Cl _0.5 · 0.9H ₂ O (rectangular platelet morphology) and Nd (OH) ₃ (acicular morphology). It is suggested that As described above, a layered rare earth hydroxide in which RE is Nd in the [RE ₈ (OH) ₂₀ (H ₂ O) _x ] ⁴⁺ layer 110 and the intermediate layer Z ^- 120 is Cl ⁻ , although not a complete simple substance. I understood that it was obtained.

  FIG. 33 is an XRD pattern of the product of Example 9.

According to FIG. 33, a peak corresponding to La (OH) ₃ was mainly detected, but a slight amount of layered rare earth hydroxide (RE (OH) _2.5 Z was observed at about 10.6 ° and about 21.2 °. _A typical peak was observed at _0.5 · 0.9H ₂ O). From this, it was found that the product of Example 9 was mainly La (OH) ₃ but also contained La (OH) _2.5 Cl _0.5 · 0.9H ₂ O. Although the layered rare earth hydroxide of the present invention is obtained in La, Nd (see Example 8), and Sm (see Example 3) among the rare earth elements RE that are not completely simple elements, It can be easily inferred that the layered rare earth hydroxide of the present invention can be obtained for Ce, Pr and Pm sandwiched between La and Sm.

  FIG. 34 is an XRD pattern of the product of Example 10.

According to FIG. 34, all XRD patterns were the same XRD patterns as in Example 5 shown in FIG. From this, the product of Example 10 is a Tb (OH) _2.5 Cl _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is is Tb, the intermediate layer ^Z - 120 are Cl ^- be layered rare earth hydroxides is obtained is suggested that. From the above, it was shown that a layered rare earth hydroxide can be obtained without adding an alkali metal halide.

Furthermore, the peak intensity of the XRD pattern of the product obtained from 5 mM TbCl ₃ in FIG. 34 was found to be lower than the peak intensity of the XRD pattern shown in FIG. This indicates that, when the same TbCl ₃ molar concentration is used, crystallinity is improved by adding an alkali metal halide (NaCl in Example 5). However, it was confirmed that when a high-concentration salt of TbCl ₃ 10 mM or more was used, a good-quality layered rare earth hydroxide with good crystallinity was obtained without adding an alkali metal halide. From the above, it is suggested that it is desirable to add an alkali metal halide when a relatively low concentration salt of less than 10 mM is used as REZ ₃ in step S210 of FIG.

  FIG. 35 shows the XRD pattern of the product of Example 11.

The XRD pattern in FIG. 35 was the same XRD pattern as in Example 5 shown in FIG. From this, the product of Example 11 is a Tb (OH) _2.5 Cl _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is is Tb, the intermediate layer ^Z - 120 are Cl ^- be layered rare earth hydroxides is obtained is suggested that. From the above, it was shown that a layered rare earth hydroxide can be obtained without adding an alkali metal halide and using a mixed solvent of water and ethanol as a solvent.

  FIG. 36 shows the XRD pattern of the product of Example 12.

The XRD pattern in FIG. 36 was the same XRD pattern as in Example 5 shown in FIG. From this, the product of Example 12 is a Tb (OH) _2.5 Br _0.5 · 0.9H ₂ O single phase, and in detail, [RE ₈ (OH) ₂₀ (H ₂ O) _x] RE in ⁴⁺ layer 110 is Tb, the intermediate layer ^Z - 120 is Br ^- be layered rare earth hydroxides is obtained is suggested that.

  FIG. 37 is a SEM image of the product of Example 12.

FIG. 37 shows a morphology in which rectangular platelets typical of a layered rare earth hydroxide having a part of an amorphous shape, but having an intermediate layer Z ^- 120 of Cl 2 ⁻ are aggregated. This also suggests that a layered rare earth hydroxide was obtained. From the above, it was shown that layered rare earth hydroxide can be obtained even if bromide is used in place of chloride as REZ ₃ in step S210 of FIG. This suggests that the halogen elements are not limited to Cl and Br, and layered rare earth hydroxides containing other halogen elements are also easily synthesized. Again, the morphology of the layered rare earth hydroxide in which the intermediate layer Z ^- 120 is a halogen element is shown to be a rectangular plate.

  38 is a view showing an SEM image of the product of Comparative Example 1. FIG.

The morphology of the product of Comparative Example 1 was plate-like typical for layered rare earth hydroxides and was obtained uniformly throughout the product. The plate shape was an elongated hexagonal shape unlike the case where the intermediate layer Z ^- 120 was halogen. This elongated hexagon is similar to the shape shown in Non-Patent Document 1, suggesting that a nitrate-type layered rare earth hydroxide was obtained.

  FIG. 39 is a diagram showing an XRD pattern of the product of Comparative Example 1.

In the XRD pattern of FIG. 39, in addition to the strong peaks at 9.8 ° and 19.7 °, a number of sharp diffraction lines were observed. When this pattern was indexed, the compound was monoclinic and the lattice constants were a = 12.800 (7) Å, b = 7.692 (8) Å, c = 9.002 (9). Å and β = 94.65 (9) ° were obtained. The length of a-axis and b-axis chlorine type compounds because it matches well with it very (i.e. the intermediate layer Z ^{- -} 120 are Cl layered rare earth hydroxide is), the compound is the same as the chlorine-type compound host It is suggested to have a layer. It is understood that the layering pattern of the host layer changes due to the effect of the interlayer ions changing from halogen ions to nitrate ions, resulting in a monoclinic structure. From the above, it was confirmed that the product of Comparative Example 1 was a nitrate-type layered rare earth hydroxide represented by the composition formula Eu (OH) _2.5 (NO ₃ ) _0.5 · 0.9H ₂ O. It is suggested.

  Comparing the XRD diffraction lines of FIG. 6 and FIG. 39, FIG. 39 was more complicated than that of FIG. In general, it is known that the number of diffraction lines appearing in XRD increases as the symmetry of the crystal structure decreases. This suggests that the symmetry of the crystal structure of the chlorine-type layered rare earth hydroxide of Example 1 is higher than that of the nitrate-type layered rare earth hydroxide of Comparative Example 1.

  Further, when the line widths of the XRD diffraction lines in FIGS. 6 and 38 were compared, it was found that the diffraction lines in FIG. 6 were sharper and the line widths shorter than those in FIG. In general, it is known that when the crystallinity is high, the line width of the XRD diffraction line is short and the peak becomes sharp. This suggests that the crystallinity of the chlorine-type layered rare earth hydroxide of Example 1 is higher than that of the nitrate-type layered rare earth hydroxide of Comparative Example 1.

  The halogen type layered rare earth hydroxide according to the present invention has been described in detail using the above examples. In particular, according to Example 1, the anion exchange ability at room temperature of the halogen-type layered rare earth hydroxide according to the present invention was confirmed. Moreover, according to Example 1 and Example 5, the fluorescence based on the rare earth element of the halogen type layered rare earth hydroxide according to the present invention was confirmed. From these, it is suggested that the layered rare earth hydroxide of the present invention is suitable as a light emitting material and an anion exchange material.

  Further, according to Examples 1 to 8, when the uniform precipitation method is employed, a rare earth element RE halide (in particular, Y, Nd, Sm, Eu, Gd, Tb, Dy, and Ho is formed at a predetermined ratio. The element selected from the group) and HMT were dissolved in ultrapure water, and it was found that the layered rare earth hydroxide of the present invention can be easily obtained at least as a main component simply by heating the resulting mixed aqueous solution. .

The layered rare earth hydroxide according to the present invention is represented by the composition formula RE (OH) _2.5 Z _0.5 · 0.125XH ₂ O (6 <X <8), where RE is a rare earth element and Z is a halogen atom. It is an element. The layered rare earth hydroxide represented by such a composition formula has a highly symmetric crystal structure and high crystallinity. Z does not directly coordinate to RE, and thus exhibits anion exchange ability at room temperature. If such a layered rare earth hydroxide is used, a highly efficient anion exchange material can be provided. Furthermore, since the layered rare earth hydroxide of the present invention exhibits fluorescence based on rare earth elements, it can function as a fluorescent material. As a matter of course, the layered rare earth hydroxide of the present invention further comprises an anion exchange material based on a layered substance having a counter anion, a light emitting material based on a rare earth element, a magnetic material, a catalyst material, and a combination thereof. Can be used for devices using these materials.

Schematic diagram (A) and crystal structure (B) of layered rare earth hydroxide according to the present invention Flowchart showing steps for producing an exemplary layered rare earth hydroxide according to the present invention. The figure which shows the SEM image of the product of Example 1 The figure which shows the TEM image of the product of Example 1 The figure which shows the SAED pattern (A) of Example 1, and the relationship (B) of a basic unit cell and a superlattice. Figure showing the XRD pattern of the product of Example 1 FIG. 5 shows a high-resolution synchrotron powder X-ray diffraction (XRD) pattern of the product of Example 1 Schematic diagram of a layered crystal structure model The figure which shows the Rietveld pattern of the product of Example 1 Diagram showing electron density distribution The figure which shows the coordination environment of Eu in the product in Example 1 The figure which shows the excitation spectrum (A) and emission spectrum (B) of the product of Example 1 The figure which shows the XRD pattern after anion exchange of the product of Example 1 Shows an SEM image of the product after the anion exchange with _- sodium nitrate in Example 1 (NO ³⁾ Shows an SEM image of the product after anion exchange with sodium sulfate of Example 1 _(SO ^{4 2-)} It shows an SEM image of the product after the anion exchange with ^- sodium dodecyl sulfate of Example _{1 (C 12 H 25 OSO 3} ) The figure which shows the FT-IR absorption spectrum of the product after anion exchange of Example 1. Figure 4 shows the XRD pattern of the product of Example 2 The figure which shows the SEM image of the product of Example 2 Figure 3 shows the XRD pattern of the product of Example 3 The figure which shows the SEM image of the product of Example 3 Figure 4 shows the XRD pattern of the product of Example 4 The figure which shows the SEM image of the product of Example 4 Figure 5 shows the XRD pattern of the product of Example 5 The figure which shows the SEM image of the product of Example 5 FIG. 5 shows the excitation / emission spectrum of the product of Example 5 Figure 4 shows the XRD pattern of the product of Example 6 The figure which shows the SEM image of the product of Example 6 Figure 7 shows the XRD pattern of the product of Example 7 The figure which shows the SEM image of the product of Example 7 Figure 4 shows the XRD pattern of the product of Example 8 The figure which shows the SEM image of the product of Example 8 Figure 5 shows the XRD pattern of the product of Example 9 Figure 5 shows the XRD pattern of the product of Example 10 FIG. 11 shows the XRD pattern of the product of Example 11. Figure 4 shows the XRD pattern of the product of Example 12 The figure which shows the SEM image of the product of Example 12 The figure which shows the SEM image of the product of the comparative example 1 The figure which shows the XRD pattern of the product of the comparative example 1

Explanation of symbols

100 layered rare earth hydroxide 110 [RE ₈ (OH) ₂₀ (H ₂ O) _x ] ⁴⁺ layer or host layer 120 intermediate layer

Claims (7)

Represented by the composition formula RE (OH) _2.5 Z _0.5 · 0.125XH ₂ O (6 <X <8),
The layered rare earth hydroxide, wherein RE is a rare earth element and Z is a halogen element.   2. The layered rare earth hydroxide according to claim 1, wherein the crystal system of the layered rare earth hydroxide belongs to an orthorhombic system. The layered rare earth hydroxide according to claim 1,
A laminate structure of a positively charged [RE ₈ (OH) ₂₀ (H ₂ O) _X ] ⁴⁺ layer (6 <X <8) and an intermediate layer Z ⁻ made of a negatively charged halogen element. A layered rare earth hydroxide.   2. The layered rare earth hydroxide according to claim 1, wherein the halogen element Z is Cl or Br.   2. The layered rare earth hydroxide according to claim 1, wherein the RE is a rare earth element selected from the group consisting of La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Y. A layered rare earth hydroxide.   An anion exchange material comprising the layered rare earth hydroxide according to any one of claims 1 to 5, wherein the anion exchange material has an intermediate layer exchangeable with an anion.   A fluorescent material that emits light by excitation from an excitation source, comprising a rare earth element as a light emission center, and comprising the layered rare earth hydroxide according to claim 1.