KR101552146B1 - Novel strontium bismuth selenite hydrate - Google Patents

Abstract

The present invention relates to a novel mixed metal oxide which may be used in product developments applied in a catalyst, an interlayer inserted complex, a drug carrier, a secondary battery positive electrode material, an electro-optic material, etc. based on properties by a layer frame structure of the mixed metal oxide. The mixed metal oxide is obtained by hydrothermal synthesis of SrCO_3, Bi_2O_3 and SeO_2.

Description

Novel strontium bismuth selenite hydrate < RTI ID = 0.0 >

The present invention relates to a strontium bismuth selenide hydrate of a new layer structure.

Mixed metal oxides generally exhibit extended structures such as chains, strata and three-dimensional frameworks. Therefore, various polyhedra of cations that can show abundant structural chemistry are observed in this oxide. Of these, selenite, that is, an oxide containing a Se ^{4 +} cation, has attracted particular interest. Synthetically, SeO ₂ has been widely introduced in most solid phase and solvent thermal reactions due to its low triple point (340 ° C), good solubility in many solvents and excellent reactivity with other oxides to make selenite. In addition, the Se ^{4 +} cations, which are the second yarn-to-teller twisted cation group, contain a stereoselectively isolated electron pair to create an essentially asymmetric coordination environment. The combination of local asymmetric geometries is known to have a tendency to increase the occurrence of macroscopic noncentral symmetry (NCS) in materials with extended structures, so that the properties of very important materials such as nonlinear optics, ferroelectricity, superconductivity, Can be expected. With this in mind, the inventors have decided to investigate the Bi ³⁺ -Se ⁴⁺ -oxide system. So far, we have reported quite a lot of bismuth selenite, and they showed abundant structural chemistry as well as interesting material properties. For example, some bismuth selenite containing a halogen, for _{example, Bi (SeO 3) Cl,} Bi 6 (SeO 3) 3 O 5 Br 2 , and _{Cu 3 Bi (SeO 3) 2} O 2 X (X = Cl or Br) due to a function as a chemical scissors for Se ^{4 +} and halogen anions that - shows the structure of a dimension. In addition, the bismuth selenide a small number of crystallizing in NCS space nitro group, for _{example, Bi (SeO 3) Cl,} Bi 2 SeO 5 and _{Bi (SeO 3) (HSeO 3} ) represents the SHG property.

As a result of this effort, the present inventors have found that a novel strontium bismuth selenite hydrate, Sr ₃ Bi ₂ (SeO ₃ ) ₆ ? ₂ O2O was synthesized and the present invention was completed by identifying the overall characteristics such as structure determination, thermal analysis, UV-vis diffuse reflectance spectrum, infrared spectrum, local dipole moment calculation, electronic structure calculation and the like.

U.S. Patent No. 8,034,250 (Oct. 11, 2011) Japanese Patent Application Laid-Open No. 1992-124023 (Apr. 24, 1992)

 Fang Kong et al. Struct Bond vol. 144, pp. 43-104 (2012)

It is an object of the present invention to provide a novel strontium bismuth selenite hydrate comprising a second yarn-Teller twist cation and its use.

In order to achieve the above object, the present invention provides a mixed metal oxide represented by the following formula (1)

[Chemical Formula 1]

Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O

The mixed metal oxide may be SrCO ₃ , Bi ₂ O ₃ And it can be obtained by hydrothermal synthesis reaction between the SeO _2.

The compound of Formula 1 may represent a layered structure composed of BiO ₇ and SeO ₃ polyhedra containing Bi-O-Bi and Bi-O-Se bonds.

The compound of formula (1) has a characteristic of exhibiting weight change at 390 ° C to 400 ° C.

Accordingly, the present invention provides a product in which the mixed metal oxide is applied to any one of a catalyst, an intercalation composite, a drug delivery system, a secondary battery positive electrode material, or an electrooptic material material.

The present invention provides mixed metal oxides of the novel strontium bismuth selenite hydrate composition.

The mixed metal oxide may be applied to a catalyst, an intercalation composite, a drug delivery system, a secondary battery positive electrode material, or an electro-optic material based on characteristics of a layered skeleton structure.

Figure 1 shows experimental and calculated values of the powder X-ray diffraction pattern for the mixed metal oxide, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O of the present invention.
FIG. 2 is a view showing ORTEP (50% probability ellipsoids) of BiO ₇ and SeO ₃ polyhedrons in mixed metal oxide, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O of the present invention.
Figure 3 (a) BiO ₇ Bi ₂ O is obtained by sharing the edges of the group ₁₂ dimer, (b) SeO ₃ group is one-dimensional band, (c) bc configured to connect to the Bi ₂ O ₁₂ dimer - Sr from the surface (Yellow, Bi, green, Se; cyan, Sr; red, O) of ₃ Bi ₂ (SeO ₃ ) ₆ H ₂ O.
Figure 4 (a) ab - in terms of _{Sr 3 Bi 2 (SeO 3)} 6 · view of the H ₂ O-and-stick and polyhedral figure (yellow, Bi; green, Se; turquoise, Sr; red, O) and , and (b) ELF calculations at η = 0.9 show steric active lone pair electrons visible around Bi ^{3 +} and Se ^{4 +} on the lobed isosurface (for clarity, Sr and H ₂ O are omitted has exist).
FIG. 5 shows an infrared spectrum of the mixed metal oxide of the present invention, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O. FIG.
Figure 6 shows the UV-vis diffuse reflectance spectrum of a mixed metal oxide, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O of the present invention showing absorption limits at 3.3 eV.
Figure 7 shows the temperature-dependent TGA diagram (a) and powder XRD pattern (b) of the mixed metal oxide, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O of the present invention.
Figure 8 shows the total electron state density (TDOS) and partial electron state density (PDOS) for the mixed metal oxide, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O of the present invention, The vertical line means E _F.
Figure 9 shows a specific PDOS plot of Sr, Bi, Se and O from the PW-PP calculation, where the vertical dashed line means the Fermi level, E _F.

Hereinafter, the configuration of the present invention will be described in detail.

The present invention relates to a mixed metal oxide represented by the following general formula (1)

[Chemical Formula 1]

Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O

The mixed metal oxide of the present invention crystallizes in a monoclinic space group and shows a layered structure composed of BiO ₇ and SeO ₃ polyhedra containing Bi-O-Bi and Bi-O-Se bonds.

The mixed metal oxide of the present invention is SrCO ₃ , Bi ₂ O ₃ And SeO2. ≪ / _RTI >

More specifically, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is hydrothermally reacted by maintaining a mixture of SrCO ₃ , Bi ₂ O ₃ , SeO ₂ and water at a temperature of 200 to 240 ° C. for 3 to 5 days , The reaction product is cooled to room temperature at a rate of 0.05 to 6 캜 / min to obtain crystals, whereby colorless crystals can be obtained.

FIG. 1 shows a powder X-ray diffraction pattern for a single crystal of a mixed metal oxide according to the present invention. The calculated value for the Sr ₃ Bi ₂ (SeO ₃ ) ₆ H ₂ O single crystal coincides with the crystal pattern of the experimental value, 5, the Se-O frequency is observed at about 740-807 cm ^-1 , and the frequency band occurring around 414-469 cm ^-1 is seen as both Bi-O and Se-O frequencies And the frequencies for H ₂ O are observed at about 1633 and 3440 cm ^-1 , confirming the mixed metal oxide synthesis of the present invention.

In addition, a definite crystal structure can be presented from the single crystal for the mixed metal oxide of the present invention.

2 to 4 show ball-and-stick model drawings of a skeleton structure in a single crystal of a mixed metal oxide of the present invention,

Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is crystallized in the macroscopic center symmetric monoclinic space group P 2 ₁ / m (No. 11) and contains Bi-O-Bi and Bi-O-Se bonds And a BiO ₇ and SeO ₃ polyhedron. Proprietary Bi ^{3 +} is bound to seven oxygen atoms in a twisted coordination environment due to a lone pair of electrons in the Bi ^{3 +} atom, and four proprietary Se ^{4 +} cations that exhibit an asymmetric coordination environment due to the stereoselective lone pair of electrons have. Se ^{4 +} cations are bound to three oxygen atoms in a triangular environment. Two proprietary Sr ²⁺ cations, Sr (1) ²⁺ and Sr (2) ²⁺ interact with 8 and 9 oxygen atoms. Two twisted BiO ₇ polyhedra share their edges through two O (1) atoms to form a Bi ₂ O ₁₂ dimer. Each Bi ₂ O ₁₂ dimer is further connected by Se (1) O ₃ and Se (4) O ₃ groups along the [100] and [001] directions to form an infinite band traveling in the [001] direction do. Here, the Se (1) O ₃ polyhedra is simply attached to the crosslinking oxygen, O (1), while the Se (4) O ₃ group is provided as an intermolecular linker. The 1-dimensional bands are connected by Se (2) O ₃ and Se (3) O ₃ groups through O (5) and O (7) along the [010] direction, . Thus, the Se (2) O ₃ and Se (3) O ₃ groups are provided as band-to-band linkers. Within the layer, an 8-membered ring (8MRs) composed of BiO ₇ and SeO ₃ polyhedra is observed. Further, the water molecule is located inside the 8MRs. In addition, Sr ^{2 +} cations are located between the layer of _{Sr 3 Bi 2 (SeO 3)} 6 · H 2 O. The lone pair of electrons on the Se (2) O ₃ and Se (3) O ₃ linkers are oriented in the [100] and [-100] directions, and the skeleton structure of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is {2 _{[Bi (1) O 5/2 O} 2/3] -3.333 2 [Se (1) O 2/1 O 1/3] -0.667 [Se (2) O 1/1 O 2/2] 0 [Se _{(3) O 1/1 O 2/} 2] 0 2 can be described as an anionic layer of _{[Se (4) O 3/2]} +1} -6.

Hereinafter, physical properties and characteristics of the mixed metal oxide of the present invention will be described with reference to the drawings.

Figure 7 illustrates a thermogravimetric analysis of the mixed metal oxide of the present invention, from the TGA diagram result _{Sr 3 Bi 2 (SeO 3)} 6 · H 2 O represents the weight change at 390 ℃ to 400 ℃, of SeO ₂ Due to sublimation, the skeleton was completely decomposed at 1000 ° C and finally decomposed into SrBi ₄ O ₇ .

In addition, the mixed metal oxide of the present invention is crystallized in a macroscopic center symmetric space group, but is composed only of asymmetric polyhedrons such as BiO ₇ and SeO _3, so that local dipole moments are calculated to quantify the degree of twist of the constituent polyhedrons. The calculated local dipole moments for the BiO ₇ and SeO ₃ polyhedra in the mixed metal oxide were found to be about 5.1 and 7.0-8.0 D (Debyes), respectively.

The mixed metal oxide of the present invention, Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O, contains Bi ^{3 +} and Se ^{4 +} , so that the related lone pair is understood and the electronic structure is calculated result, the electronic structure is in proportion to the respective e _F narrow and wide valence stand which exhibits a roughly 2.8 eV of energy gap (also sets the e _F to 0 eV) Fermi level indicates the insulative, separated by about 2 eV - 9 eV and -7 eV. Further, according to the partial result of the electronic density of states (PDOS), a narrow band mainly O (2sp), Se (4s ), and Bi (6s), but consists of an orbital contributions, wide band, the two areas, that is, E _F (About -7.0 eV to -4.0 eV) and a higher area (about -4.0 eV). The lower region contains a larger contribution from the O (2p) and Se (4p) orbital states with a smaller contribution from the Bi (6p) state, It has a small contribution and a valid contribution from the O (2p) state. This means that their non-binding properties, and, in particular, weak contribution of the valence band higher region from Se (4p) and Bi (6p) is associated with a three-dimensional active lone pair of electrons formed in the Se ^{4 +} and Bi ^{3 +} cations . Calculations of the ELF equilibrium surface revealed that a lobed isosurface considered to be a sterically active lone pair of electrons was clearly observed near both Bi ^{3 +} and Se ^{4 +} cations.

As described above, the mixed metal oxide of the present invention has a layered structural feature composed only of asymmetric cations, so that the intercalation reaction is possible, so that under a suitable condition, one kind of compound is formed as a layer interposed between different kinds of materials It can be used as an interlayer-inserting complex or a drug carrier, and can be used as a secondary battery anode material using reversible migration of metal cations inserted between layers, and can be used for electro-optical material materials using structural characteristics.

In addition, it can be used as a heterogeneous acid catalyst which easily converts various organic materials such as acetalization reaction of aldehyde.

Accordingly, the present invention is useful for the development of a product using the mixed metal oxide of the present invention, such as a catalyst, an intercalation composite, a drug delivery vehicle, a secondary battery positive electrode material, or an electro-optical material.

Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

≪ Example 1 > Synthesis of mixed metal oxide

SrCO ₃ (Aldrich, 99.9%), Bi ₂ O ₃ (Alfa Aesar, 99%) and SeO ₂ (Aldrich, 98%) used for the synthesis of mixed metal oxides were used for the synthesis as purchased.

Single crystals of Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O were obtained by hydrothermal reaction. 0.443 g min (3.00 × 10 ^-3 mol) of _{SrCO 3, 0.233 g (5.00 ×} 10 -4 mol) of _{Bi 2 O 3, 0.666 g (} 6.00 × 10 -3 mol) SeO 2 and deionized water in 5 mL of Were mixed and placed in a 23 mL-Teflon cup and placed in a stainless steel autoclave. The reactor was tightly sealed, heated to 230 占 폚 for 4 days, and cooled to room temperature at a rate of 0.1 占 폚 / min. After cooling, the autoclave was opened, and the product was recovered by filtration and washed several times with distilled water. The product was dried overnight at room temperature. The colorless crystals of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O yielded 77% based on SrCO ₃ with very small amounts of polycrystalline Bi ₂ O ₃ and SrSeO ₄ .

A pure polycrystalline sample of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O contained 0.590 g (4.00 × 10 ^-3 mol) of SrCO ₃ , 0.233 g (5.00 × 10 ^-4 mol) of Bi ₂ O ₃ , 0.777 g (7.00 × 10 ^-3 mol) of SeO ₂ and 5 mL of deionized water under similar reaction conditions.

Experimental Example 1 Powder X-ray diffraction pattern analysis

Powder X-ray diffraction was used to determine the phase purity for Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O. Powder XRD patterns were obtained on a Bruker D8-Advance diffractometer at 40 kV and 40 mA using Cu Kα radiation at room temperature. Powder samples were placed in a sample holder and scanned over a 2? Range of 5-70 ° with a step time of 0.2 s and a step size of 0.02 °.

Figure 1 compares the calculated XRD patterns of Sr ₃ Bi ₂ (SeO ₃ ) ₆ H ₂ O polycrystals with calculated values and shows that the pure phase of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O has been successfully Was synthesized and was in good agreement with the pattern calculated in the single crystal model.

<Experimental Example 2> Structural analysis

A standard crystallographic method was used to measure the crystal structure of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O. For single crystal data analysis were selected _{Sr 3 Bi 2 (SeO 3)} 6 · Colorless plate crystals of _{H 2 O (0.012 × 0.033 ×} 0.044 mm 3). Diffraction data were collected at room temperature on a Bruker SMART BREEZE diffractometer equipped with a 1K CCD area detector using graphite monochromated Mo Kα radiation. This data was obtained using a narrow-frame method with a scan width of 0.30 ° and an exposure time of 10 s / frame. To confirm the determination and equipment stability, we again measured at the end of the data collection for the initial 50 frames. The maximum correction applied to the strength was <1%. The SAINT program was used to integrate all the diffractions collected. Also, intensities for air absorption, Lorentz factor, polarization, and absorption due to variables in the path length through the detector faceplate were collected. The structure was solved using SHELXS-97, and data was improved using SHELXL-97. All calculations were performed through the WinGX-98 crystallography software package. The crystallographic information according to the selected binding distance to Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is listed in Tables 1 and 2.

Crystallographic data of Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O Empirical formula Sr ₃ Bi ₂ Se ₆ O ₁₉ H ₂ Empirical molecular weight 1460.60 Crystal system Monoclinic system Space group P 2 ₁ / m (No. 11) a / A 7.0054 (10) b / A 17.5092 (3) c / Å 7.3053 (10) β / ° 92.299 (10) V / Å ³ 895.34 (2) Z 2 T / K 298.0 (2) λ / Å 0.71073 R ( F ) ^a 0.0363 R _w ( F _o ² ) ^b 0.0975 ^a R ( F ) = S || F _o | - | F _c || / S | F _o |.
^b R _w ( F ² ) = [S w ( F _o ² - F _c ² ) ² / S w ( F _o ² ) ² ] ^1/2 .

The bonding distance (A) selected for Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O, Bi (1) -O (1) 2.368 (8) Se (1) -O (1) 1.739 (8) Bi (1) -O (1) 2.456 (8) Se (1) -O (2) 1.699 (8) Bi (1) -O (5) 2.429 (9) Se (1) -O (3) 1.675 (8) Bi (1) -O (7) 2.655 (8) Se (2) -O (4) 1.654 (13) Bi (1) -O (8) 2.531 (8) Se (2) -O (5) x 2 1.712 (8) Bi (1) -O (9) 2.593 (8) Se (3) -O (6) 1.685 (11) Bi (1) -O (10) 2.330 (8) Se (3) -O (7) x 2 1.709 (8) Se (4) -O (8) 1.691 (8) Se (4) -O (9) 1.685 (8) Se (4) -O (10) 1.740 (7)

FIGS. 2 to 4 show ball-and-stick model drawings of the crystal structure of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O of the present invention,

Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O has a layered structure and crystallizes in monoclinic space group P 2 ₁ / m (No. 11). The structure backbone of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is composed of BiO ₇ and SeO ₃ polyhedra containing Bi-O-Bi and Bi-O-Se bonds. Proprietary Bi ^{3 +} is bound to seven oxygen atoms in a twisted coordination environment due to its lone pair of electrons (Figure 2).

The Bi-O bond distance and the O-Bi-O bonding angle observed in the BiO ₇ polyhedra are 2.330 (8) -2.655 (8) A and 66.5 (2) -154.8 (3) °, respectively. There are also four unique Se ^{4 +} cations that exhibit an asymmetric coordination environment due to a solubilized lone pair of electrons in the asymmetric unit (Fig. 2). The Se ^{4 +} cations had three Se-O bond lengths and three O-Se-O bonds in a triangular environment with O-Se-O bond angles of 1.654 (13) -1.740 (7) Å and 95.1 (4) -102.3 And are bonded to oxygen atoms. 2 of the original Sr ^{2 +} cations, Sr (1) ²⁺ and Sr (2) ²⁺ are each 2.540 8 to 2.848 8, 8 and 9, one oxygen atom having a Sr-O contact length of Å Lt; / RTI &gt; The two twisted BiO ₇ polyhedra share their edges through two O (1) atoms to form a Bi ₂ O ₁₂ dimer (Fig. 3a). Each Bi ₂ O ₁₂ dimer is further connected by Se (1) O ₃ and Se (4) O ₃ groups along the [100] and [001] directions to form an infinite band traveling in the [001] direction do. Here, the Se (1) O ₃ polyhedron is simply attached to the crosslinking oxygen, O (1), while the Se (4) O ₃ group is provided as an intermolecular linker (FIG. Then, as can be seen in FIG. 3c, the 1-dimensional bands are added to the Se (2) O ₃ and Se (3) O ₃ groups via O (5) and O And a layered structure is formed on the bc - plane. Thus, the Se (2) O ₃ and Se (3) O ₃ groups are provided as band-to-band linkers. Within the layer, an 8-membered ring (8MRs) composed of BiO ₇ and SeO ₃ polyhedra is observed (FIG. 3C). In addition, water molecules are located inside 8MRs. It can be seen that the new layered skeleton with ₈ MRS in Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O consists solely of the polyhedral cations of the electron pair cations, namely Bi ^{3 +} O ₇ and Se ^{4 +} O ₃ . So far, a small number of layered structures composed of isolated electron pair cations have been reported, but they contain 6MRs in the layer.

Finally, Sr ^{2 +} cations are Sr ₃ Bi ₂ (SeO ₃₎ is positioned completely between the layer of ₆ · H ₂ O (Fig. 4a). As can be seen in the ELF visualization with eta = 0.9 in Figure 4b, the isosurface of the lobed shape is clearly observed near Bi ^{3 +} and Se ^{4 +} , so that the isosurface is considered to be a sterically active isolated electron pair will be. In particular, the isolated electron pairs on the Se (2) O ₃ and Se (3) O ₃ linkers are oriented in the [100] and [-100] directions (FIG. Therefore, Bi ₂ Sr ₃ (SeO _{3) 6} · H ₂ O is the skeleton of 2 {[Bi (1) _5/2 O O _2/3] 2 ^-3.333 [Se (1) _2/1 O O _{1 / ^{3] -0.667 [Se (2)}} O 1/1 O 2/2] 0 [Se (3) O 1/1 O 2/2] 0 2 [Se (4) O 3/2] +1} -6 Of the anionic layer. The total sum of bonding atoms for Sr ^{2 +} , Bi ^{3 +} and Se ^{4 +} was found to be 1.62-1.95, 2.73 and 3.98-4.08, respectively.

<Experimental Example 3> Infrared spectrum analysis

Infrared spectra were recorded in the spectral range of 400-4000 cm &lt; ^-1 &gt; using a Varian 1000 FT-IR spectrometer for the samples sandwiched in the KBr matrix.

As shown in Figure 5, it shows a characteristic Se-O frequency at about 740-807 cm ^-1 . The frequency bands occurring around 414-469 cm ^-1 can be seen in both Bi-O and Se-O oscillations. The frequencies for H ₂ O were observed at about 1633 and 3440 cm ^-1 . This arrangement corresponds to the frequency of the substances already reported.

EXPERIMENTAL EXAMPLE 4 UV-Vis Diffuse Reflectance Spectroscopy (Diffuse Reflectance Spectroscopy)

The UV-Vis diffuse reflectance spectra were collected on a Varian Cary 500 scan UV-vis-NIR spectrophotometer over a spectral range of 200-2500 nm at room temperature in a Korean photovoltaic source. The UV-Vis diffuse reflectance spectrum was converted to absorbance using the Kubelka-Munk function.

[Equation 1]

Here, K represents absorption, S represents scattering, and R represents reflection.

In the ( K / S ) - versus E plot for Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O, extrapolation of the straight line portion of the rising curve to zero shows an onset of absorption at 3.3 eV (FIG. The bandgap for Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O appears to be due to the interaction of Se-O and Bi-O bonds, as will be explained in more detail later in the calculation section. In addition, the distortion caused by the SeO ₃ and BiO ₇ polyhedra will affect the onset of absorption for Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O.

&Lt; Experimental Example 5 >

The thermal behavior of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O was tested using thermogravimetric analysis and powder X-ray diffraction. Thermogravimetric analysis was performed on a Setaram LABSYS TG-DTA / DSC thermogravimetric analyzer. A finely ground powder sample was placed in an aluminum crucible and heated from room temperature to 1000 ° C at a rate of 10 ° C / min while flowing argon gas.

Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O shows very little weight loss (1.2%) between room temperature and 280 ° C due to the loss of trapped water molecules. Although the trapped water molecules have been removed, the skeleton of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O remains the same when viewed based on the PXRD pattern at different temperatures (FIG. 7A). The skeleton of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is thermally stable up to 390 ° C. When this temperature is exceeded, the skeleton of Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O begins to collapse due to the sublimation of SeO ₂ and is completely decomposed at 1000 ° C. The thermal stability of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is confirmed in powder X-ray diffraction (FIG. 7b). The thermal decomposition product is confirmed to be SrBi ₄ O ₇ (PDF- # 46-0752) based on the PXRD pattern.

Experimental Example 6 SEM / EDAX analysis

SEM / EDAX (Scanning Electron Microscopy / Energy Dispersive Analysis by X-ray) was performed using a Hitachi S-3400N and a Horiba Energy EX-250 device.

The EDAX for Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O showed a Sr: Bi: Se ratio of 3.0: 2.2: 5.7.

Experimental Example 7 Dipole Moment Calculation

The new layered bismuth selenite, Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O crystallizes in the macroscopic center symmetric space group, P 2 ₁ / m . However, the backbone of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O consists solely of asymmetric polyhedra such as BiO ₇ and SeO ₃ due to the stereoselectively isolated electron pairs. Therefore, in order to better understand how the skeleton of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O is composed of asymmetric units, methods described previously (J. Galy and G. Meunier, J. Solid State Chem . , 1975, 13, 142), it is necessary to quantify the degree of distortion of the constituent polyhedrons.

The calculated local dipole moments for the BiO ₇ and SeO ₃ polyhedra in Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O were about 5.1 and 7.0-8.0 D (Debyes), respectively, similar to those reported previously . The local dipole moments for the BiO ₇ and SeO ₃ groups are listed in Table 3.

Calculation of dipole moments for BiO ₇ and SeO ₃ polyhedra in Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O (D = Debyes) Bell Dipole moment (D) Bi (1) O ₇ 5.1 Se (1) O ₃ 8.0 Se (2) O ₃ 7.7 Se ₍₃₎ O 3 7.6 Se (4) O ₃ 7.0

&Lt; Experimental Example 8 > Electronic structure calculation

The electronic structure calculations for Sr ₃ Bi ₂ (SeO ₃ ) ₆ · H ₂ O were performed not only to understand the lone pair of electrons related to Bi ^{3 +} and Se ^{4 +} , but also to test the bonding structure. First-principles density functional theory (DFT) for Sr ₃ Bi ₂ (SeO ₃ ) ₆ H ₂ O Electronic structure calculations are performed as described in the Quantum ESPRESSO (version 5.0.2) package plane-wave (PW) pseudo-potential (PP) method. The norm-conserving Martins-Troullier (MT) similar potential for all elements was used with a generalized gradient approximation (GGA) for exchange-relationship correction. The plane-wave energy cutoff was fixed at 37 Ry. The Brillouin zone was used as a sample of 4 x 4 x 4 Monkhorst-Pack (MP) k-mesh. The total - energy convergence threshold was set to 10 ^-6 Ry. Experimental crystal structures were used for all calculations. Using the program VESTA we were able to obtain a structural description.

The total electron state density (TDOS) and the partial density of states (PDOS) of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O are shown in FIG. Sr ₃ Bi ₂ (SeO ₃ ) ₆ ? A specific PDOS plot for Sr, Bi, Se, and O that can provide an understanding of the binding characteristics between atoms in ₂ O 2 O is shown in FIG.

As shown in Figure 8, the electronic structure exhibits approximately 2.8 eV of energy gap (also E _F set to 0 eV) Fermi level. Although the calculated bandgap is slightly smaller than the experimental value of 3.3 eV obtained in the UV-vis diffuse reflectance spectrum, both the calculated and the experimental data consistently indicate the insulation of Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O. It is also known that the calculation of the electronic coupling structure tends to underestimate the band gap energy. The narrow and broad valence electron bands, which are separated by approximately 2 eV, are observed around -9 eV and -7 eV, respectively, in proportion to E _F (Fig. 8). PDOS also suggests that the narrow band is composed primarily of O (2sp), Se (4s) and Bi (6s) orbital contributions. However, the wide band exhibits two regions: a lower region (about -7.0 eV to -4.0 eV) and a higher region (about -4.0 eV) versus E _F. The lower region contains a larger contribution from the O (2p) and Se (4p) orbital states with a smaller contribution from the Bi (6p) state, It has a small contribution and a valid contribution from the O (2p) state. The larger contribution to both the low and high regions in the O (2p) state is considered to be their unconjugated nature. In particular, the weak contribution of Se (4p) and Bi (6p) to higher regions of valence electron bands is associated with the formation of stereoselectively isolated electron pairs in Se ^{4 +} and Bi ^{3 +} cations. The ELF equilibrium was also calculated by the norm-conserving MT-like potency calculation (FIG. 4b). Although a certain degree of caution is required to obtain from the ELF equilibrium, a lobe-like isosurface considered to be a sterically active lone pair of electrons was naturally observed in the vicinity of both Bi ^{3 +} and Se ^{4 +} cations.

Claims (5)

A mixed metal oxide represented by the following general formula (1)
[Chemical Formula 1]
Sr ₃ Bi ₂ (SeO ₃ ) ₆ .H ₂ O
The method according to claim 1,
The mixed metal oxide is SrCO ₃ , Bi ₂ O ₃ And SeO2. &Lt; / _RTI &gt;
The method according to claim 1,
Wherein the mixed metal oxide of the formula (1) exhibits a layered structure composed of BiO ₇ and SeO ₃ polyhedra containing Bi-O-Bi and Bi-O-Se bonds.
The method according to claim 1,
Wherein the mixed metal oxide of formula (1) exhibits a change in weight at 390 캜 to 400 캜.
A product in which the mixed metal oxide according to claim 1 is applied to any one of a catalyst, an intercalation composite, a drug delivery system, a secondary battery positive electrode material or an electrooptic material material.

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