A Sr5Nb5O 17 Method for producing a phase material

Abstract

This invention relates to the field of functional materials preparation technology, and particularly to a Sr5Nb5O with a five-layered perovskite structure. 17 A method for preparing phase materials, which involves creating oxygen vacancies by doping with metal cations to obtain Sr5Nb5O with a five-layer structure. 17 The preparation steps of the polycrystalline powder material include: (1) raw material preparation; (2) grinding; (3) pressing; (4) pre-firing; (5) secondary grinding and pressing; (6) sintering; and (7) acid washing to remove impurities. This preparation method can overcome the limitations of current layered perovskite Sr5Nb5O 17 The preparation process of basic ceramic materials suffers from drawbacks such as complexity, numerous procedures, and instability. This paper describes a simple, stable, and efficient method for preparing five-layered perovskite Sr5Nb5O. 17 Ceramic-based materials.

Description

Technical Field

[0001] This invention relates to the field of functional materials preparation technology, and particularly to a Sr5Nb5O with a five-layered perovskite structure. 17 Methods for preparing phase materials. Background Technology

[0002] Layered perovskite niobate compounds have attracted widespread attention as novel functional materials. These materials exhibit unique chemical properties in photocatalysis, ion exchange, high-temperature piezoelectricity, electrochemistry, and photoluminescence, demonstrating broad application prospects. Therefore, the simple, efficient, and reliable preparation of high-quality layered perovskite niobate ceramic materials has always been a research focus. This material belongs to the general formula A. n B n O 3n+2 (A = Sr, Ca, La; B = Nb, Ta, Ti) is a member of the layered perovskite family. It is a layered structure composed of perovskite units consisting of oxygen octahedrons (BO6) sharing a vertex oxygen atom and 12-coordinated A-site cations, where n is the number of octahedral layers in the perovskite structure. The chemical formula is Sr. n Nb n O 3n+2 It is usually represented as (SrNbO) x Sr niobate compounds. The crystal structure and physical properties of these compounds are determined by their oxygen content; even minute changes in oxygen content can control their atomic structure and physical properties. n Nb n O 3n+2 The two most representative compounds in the n=5 group are the n=5 type compound Sr5Nb5O. 17 (SrNbO 3.4 ) and n=4 type compound Sr2Nb2O7(SrNbO) 3.5 ).

[0003] Because Sr₂Nb₂O₇ has relatively low raw material costs, and previous studies have shown that while Sr₂Nb₂O₇-based materials have significant potential applications in many different fields due to their diverse functionalities, they also have some limitations. For example, although the four-layered parent Sr₂Nb₂O₇ exhibits oxygen ion conductivity, its electrical conductivity is not high; as a high-temperature piezoelectric ceramic, it has a high coercivity field, is difficult to polarize, and has an extremely low piezoelectric constant; as a novel photocatalytic material, its wide bandgap and low efficiency are the main reasons restricting its application. Therefore, it is necessary to further explore the effects of different doping strategies on its structure, electrical properties, and photocatalytic performance, with the aim of obtaining Sr₂Nb₂O₇-based functional materials with multifaceted high performance.

[0004] Sr5Nb5O17 The material has been reported to possess thermoelectric properties, and the measured thermoelectric parameters exhibit strong anisotropy, with significant anisotropy also present in the in-plane direction of the layered structure. Therefore, the thermoelectric properties depend on the measurement direction. In Sr5Nb5O 17 The material exhibits the best performance along the a-axis, with a ZT value of 3.6 × 10⁻⁶ at room temperature. -3 In addition, Sr5Nb5O 17 Sr₅Nb₅O₂ exhibits highly anisotropic quasi-one-dimensional electrical conductivity, with the highest conductivity along the a-axis and displaying obvious metallic conductivity characteristics. Previous studies have typically employed complex suspended-region melting techniques and controlled different synthesis atmospheres to adjust the valence state of Nb to prepare Sr₅Nb₅O₂. 17 Single crystal (Chen C, et al. ACS Nano, 2017, 11(12): 12519-12525.). This preparation method requires stringent conditions and involves a complex process with numerous manual operations. The crystal properties are significantly affected by these manual operations, resulting in high error and failure rates, which hinders large-scale production and widespread application. Therefore, it is crucial to provide a simple, efficient, and easily controllable five-layered perovskite Sr5Nb5O. 17 The preparation method of ceramic materials is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The objective of this invention is to address the aforementioned problems by providing a Sr5Nb5O structure with a five-layered perovskite structure. 17 A method for preparing phase materials that can overcome the limitations of current methods for preparing layered perovskite Sr5Nb5O 17 The preparation process of basic ceramic materials suffers from drawbacks such as complexity, numerous procedures, and instability. This paper describes a simple, stable, and efficient method for preparing five-layered perovskite Sr5Nb5O. 17 Ceramic-based materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A Sr5Nb5O with a five-layered perovskite structure 17 A method for preparing phase materials, which utilizes metal cation doping to create oxygen vacancies to obtain Sr5Nb5O with a five-layer structure. 17 The specific preparation steps for the polycrystalline powder-based material are as follows:

[0008] (1) Preparation of raw materials: according to Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9The molar ratio of Sr, Nb, Ga, and Mo in the raw materials SrCO3, Nb2O5, Ga2O3, and MoO3 is determined.

[0009] (2) Grinding: Grind the raw materials prepared in step (1) in a liquid grinding medium. After grinding evenly, dry the mixed slurry to obtain a mixture powder.

[0010] (3) Tableting: The mixture powder obtained in step (2) is pressed into tablets to obtain sample tablet A;

[0011] (4) Pre-firing: The sample A obtained in step (3) is pre-firing to obtain the pre-firing sample;

[0012] (5) Secondary grinding and tableting: The pre-burnt sample obtained in step (4) is ground in liquid grinding medium and then dried to obtain a powder sample after secondary grinding. The powder sample after secondary grinding is then pressed into tablets to obtain sample tablet B.

[0013] Secondary grinding can effectively prevent recrystallization during pre-calcination; re-pressing can increase the contact area and bonding force, facilitate the reaction, and reduce volatilization; in addition, secondary grinding and pressing can fully react the sample obtained after pre-calcination in step (4), which is conducive to the next step of sintering and further obtaining the five-layer structure of Sr5Nb5O. 17 Prepare phase materials;

[0014] (6) Sintering: The sample sheet B obtained in step (5) is sintered to obtain a ceramic sheet;

[0015] (7) Acid washing to remove impurities: After grinding the ceramic sheet obtained in step (6) into powder, the powder is added to 0.05-0.8 mol / L sulfuric acid, and then heated. After heating, it is filtered and washed to obtain the target product, namely Sr5Nb5O with a five-layered layered perovskite structure. 17 Phase materials.

[0016] Furthermore, in the above preparation method, the purity of SrCO3, Nb2O5, Ga2O3 and MoO3 in step (1) is all above 99.50% (mass percentage).

[0017] Furthermore, in the above preparation method, the liquid grinding medium in steps (2) and (5) is anhydrous ethanol or pure water.

[0018] Furthermore, in the above preparation method, the grinding time in steps (2) and (5) is 30 to 120 minutes.

[0019] Furthermore, in the above preparation method, in steps (3) and (5), the mixed powder is pressed into tablets under a pressure of 1 to 8 MPa.

[0020] Furthermore, in the above preparation method, in step (4), the pre-calcination temperature is 1000-1300℃ and the pre-calcination time is 2-20h.

[0021] Furthermore, in the above preparation method, in step (6), the sintering temperature is 1350-1550℃ and the sintering time is 6-20h.

[0022] Furthermore, in the above preparation method, in step (7), the heating temperature is 50-150°C and the heating time is 10-90 minutes.

[0023] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0024] This invention employs solid-state synthesis and acid washing methods to generate oxygen vacancies by doping with metal cations, thereby obtaining Sr5Nb5O with a five-layer structure. 17 This method utilizes a powder-based polycrystalline material, which, compared to existing technologies that use suspended melting techniques and control different synthesis atmospheres to adjust the valence state of Nb, prepares Sr5Nb5O. 17 The preparation method provided by this invention for single crystal Sr5Nb5O is not only simple and easy to implement, reducing manual labor input, but also yields high-quality Sr5Nb5O. 17 The phase material has high crystal purity and good stability, and can be synthesized on a large scale with a five-layered perovskite structure, Sr5Nb5O 17 Phase materials. Attached Figure Description

[0025] Figure 1 The five-layered Sr5Nb5O prepared in Example 1 17 XRD patterns of phase materials.

[0026] Figure 2 The five-layered Sr5Nb5O prepared in Example 2 17 XRD patterns of phase materials.

[0027] Figure 3 The five-layered Sr5Nb5O prepared in Example 3 17 XRD patterns of phase materials.

[0028] Figure 4 The five-layered Sr5Nb5O prepared in Example 4 17 XRD patterns of phase materials.

[0029] Figure 5 The five-layered Sr5Nb5O prepared in Example 5 17 XRD patterns of phase materials.

[0030] Figure 6 It is the Sr5Nb5O with a five-layer structure prepared in Example 3. 17 Microscopic morphology and elemental distribution of the material under a scanning electron microscope.

[0031] Figure 7 It is the Sr5Nb5O with a five-layer structure prepared in Example 3. 17 Transmission electron microscope (TEM) images of the phase materials, where (a) is the electron diffraction (SAED) pattern of the material prepared in Example 3 under a TEM, and (b) is the elemental distribution (EDS) pattern of the material prepared in Example 3 under a TEM.

[0032] Figure 8 Sr5Nb5O with a five-layer structure prepared in Example 3 17 Second harmonic generation (SHG) test results for phase materials. Detailed Implementation

[0033] To more clearly illustrate the present invention, the following specific embodiments will be used to further explain the invention.

[0034] The raw materials strontium carbonate, niobium oxide, gallium oxide and molybdenum oxide used in the following examples are all analytical grade reagents, and their specifications are shown in Table 1.

[0035] Specifications of raw materials used (Table 1)

[0036]

[0037] Example 1:

[0038] This embodiment provides a method for preparing a five-layered perovskite structure Sr5Nb5O 17 The method for phase materials includes the following steps:

[0039] (1) Preparation of raw materials: SrCO3, Nb2O5, Ga2O3 and MoO3 with a purity of 99.50% or higher (mass percentage) are prepared according to the Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The molar ratio of Sr, Nb, Ga, and Mo in the feed was weighed and mixed, i.e., the molar ratio of SrCO3, Nb2O5, Ga2O3, and MoO3 was 2:0.8:0.1:0.2.

[0040] (2) Grinding: Place the raw materials prepared in step (1) into an agate mortar and grind them repeatedly in anhydrous ethanol for 30 minutes. After grinding evenly, dry the mixed slurry to obtain the mixed powder.

[0041] (3) Tableting: Pour the mixture powder obtained in step (2) into a mold and press it into a tablet under a pressure of 1 MPa using a tablet press to obtain sample tablet A;

[0042] (4) Pre-calcination: The sample A obtained in step (3) is placed in an alumina crucible and placed in a muffle furnace. It is pre-calcined at 1000℃ for 2 hours to obtain the pre-calcined sample.

[0043] (5) Secondary grinding and tableting: The pre-calcined sample obtained in step (4) is ground in anhydrous ethanol for 30 minutes and dried to obtain a powder sample after secondary grinding. The powder sample after secondary grinding is loaded into a mold and pressed into a tablet under a pressure of 1 MPa by a tablet press to obtain sample tablet B.

[0044] (6) Sintering: The sample sheet B obtained in step (5) is placed in a muffle furnace and sintered at 1350℃ for 6 hours to obtain a ceramic sheet;

[0045] (7) Acid washing to remove impurities: After grinding the ceramic pieces obtained in step (6) into powder in a mortar, the powder is added to 0.05 mol / L sulfuric acid and heated at 50°C for 10 minutes. Then, the product is obtained by filtration and washing.

[0046] Example 2:

[0047] This embodiment provides a method for preparing a five-layered perovskite structure Sr5Nb5O 17 The method for phase materials includes the following steps:

[0048] (1) Preparation of raw materials: SrCO3, Nb2O5, Ga2O3 and MoO3 with a purity of 99.50% or higher (mass percentage) are prepared according to the Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The molar ratio of Sr, Nb, Ga, and Mo in the feed was weighed and mixed, i.e., the molar ratio of SrCO3, Nb2O5, Ga2O3, and MoO3 was 2:0.8:0.1:0.2.

[0049] (2) Grinding: Place the raw materials prepared in step (1) into an agate mortar and grind them repeatedly in pure water for 50 minutes. After grinding evenly, dry the mixed slurry to obtain the mixed powder.

[0050] (3) Tableting: Pour the mixture powder obtained in step (2) into a mold and press it into a tablet under a pressure of 3 MPa using a tablet press to obtain sample tablet A;

[0051] (4) Pre-calcination: The sample A obtained in step (3) is placed in an alumina crucible and placed in a muffle furnace. It is pre-calcined at 1100℃ for 6 hours to obtain the pre-calcined sample.

[0052] (5) Secondary grinding and tableting: The pre-calcined sample obtained in step (4) is ground in pure water for 50 minutes, dried to obtain a powder sample after secondary grinding, and then loaded into a mold and pressed into a tablet by a tablet press under a pressure of 3 MPa to obtain sample tablet B.

[0053] (6) Sintering: The sample sheet B obtained in step (5) is placed in a muffle furnace and sintered at 1400℃ for 10h to obtain a ceramic sheet;

[0054] (7) Acid washing to remove impurities: After grinding the ceramic pieces obtained in step (6) into powder in a mortar, the powder is added to 0.2 mol / L sulfuric acid and heated at 80°C for 20 minutes. Then, the product is obtained by filtration and washing.

[0055] Example 3:

[0056] This embodiment provides a method for preparing a five-layered perovskite structure Sr5Nb5O 17 The method for phase materials includes the following steps:

[0057] (1) Preparation of raw materials: SrCO3, Nb2O5, Ga2O3 and MoO3 with a purity of 99.50% or higher (mass percentage) are prepared according to the Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The molar ratio of Sr, Nb, Ga, and Mo in the feed was weighed and mixed, i.e., the molar ratio of SrCO3, Nb2O5, Ga2O3, and MoO3 was 2:0.8:0.1:0.2.

[0058] (2) Grinding: Place the raw materials prepared in step (1) into an agate mortar and grind them repeatedly in anhydrous ethanol for 70 minutes. After grinding evenly, dry the mixed slurry to obtain the mixed powder.

[0059] (3) Tableting: Pour the mixture powder obtained in step (2) into a mold and press it into a tablet under a pressure of 5 MPa using a tablet press to obtain sample tablet A;

[0060] (4) Pre-calcination: The sample A obtained in step (3) is placed in an alumina crucible and placed in a muffle furnace. It is pre-calcined at 1200℃ for 12 hours to obtain the pre-calcined sample.

[0061] (5) Secondary grinding and tableting: The pre-calcined sample obtained in step (4) is ground in anhydrous ethanol for 70 minutes, dried to obtain a powder sample after secondary grinding, and then loaded into a mold and pressed into a tablet by a tablet press under a pressure of 5 MPa to obtain sample tablet B.

[0062] (6) Sintering: The sample sheet B obtained in step (5) is placed in a muffle furnace and sintered at 1450℃ for 12 hours to obtain a ceramic sheet;

[0063] (7) Acid washing to remove impurities: After grinding the ceramic pieces obtained in step (6) into powder in a mortar, the powder is added to 0.4 mol / L sulfuric acid and heated at 100°C for 40 minutes. Then, the product is obtained by filtration and washing.

[0064] Example 4:

[0065] This embodiment provides a method for preparing a five-layered perovskite structure Sr5Nb5O 17 The method for phase materials includes the following steps:

[0066] (1) Preparation of raw materials: SrCO3, Nb2O5, Ga2O3 and MoO3 with a purity of 99.50% or higher (mass percentage) are prepared according to the Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The molar ratio of Sr, Nb, Ga, and Mo in the feed was weighed and mixed, i.e., the molar ratio of SrCO3, Nb2O5, Ga2O3, and MoO3 was 2:0.8:0.1:0.2.

[0067] (2) Grinding: Place the raw materials prepared in step (1) into an agate mortar and grind them repeatedly in pure water for 100 minutes. After grinding evenly, dry the mixed slurry to obtain the mixed powder.

[0068] (3) Tableting: Pour the mixture powder obtained in step (2) into a mold and press it into a tablet under a pressure of 5 MPa using a tablet press to obtain sample tablet A;

[0069] (4) Pre-calcination: The sample A obtained in step (3) is placed in an alumina crucible and placed in a muffle furnace. It is pre-calcined at 1250°C for 16 hours to obtain the pre-calcined sample.

[0070] (5) Secondary grinding and tableting: The pre-calcined sample obtained in step (4) is ground in pure water for 100 minutes, dried to obtain a powder sample after secondary grinding, and then loaded into a mold and pressed into a tablet by a tablet press under a pressure of 5 MPa to obtain sample tablet B.

[0071] (6) Sintering: The sample sheet B obtained in step (5) is placed in a muffle furnace and sintered at 1500℃ for 16h to obtain a ceramic sheet;

[0072] (7) Acid washing to remove impurities: After grinding the ceramic pieces obtained in step (6) into powder in a mortar, the powder is added to 0.6 mol / L sulfuric acid and heated at 120°C for 60 minutes. Then, the product is obtained by filtration and washing.

[0073] Example 5:

[0074] This embodiment provides a method for preparing a five-layered perovskite structure Sr5Nb5O 17 The method for phase materials includes the following steps:

[0075] (1) Preparation of raw materials: SrCO3, Nb2O5, Ga2O3 and MoO3 with a purity of 99.50% or higher (mass percentage) are prepared according to the Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The molar ratio of Sr, Nb, Ga, and Mo in the feed was weighed and mixed, i.e., the molar ratio of SrCO3, Nb2O5, Ga2O3, and MoO3 was 2:0.8:0.1:0.2.

[0076] (2) Grinding: Place the raw materials prepared in step (1) into an agate mortar and grind them repeatedly in anhydrous ethanol for 120 minutes. After grinding evenly, dry the mixed slurry to obtain the mixed powder.

[0077] (3) Tableting: Pour the mixture powder obtained in step (2) into a mold and press it into a tablet under a pressure of 8 MPa using a tablet press to obtain sample tablet A;

[0078] (4) Pre-calcination: The sample A obtained in step (3) is placed in an alumina crucible and placed in a muffle furnace. It is pre-calcined at 1300℃ for 20 hours to obtain the pre-calcined sample.

[0079] (5) Secondary grinding and tableting: The pre-calcined sample obtained in step (4) is ground in anhydrous ethanol for 120 minutes and dried to obtain a powder sample after secondary grinding. The powder sample after secondary grinding is loaded into a mold and pressed into a tablet under a pressure of 8 MPa by a tablet press to obtain sample tablet B.

[0080] (6) Sintering: The sample sheet B obtained in step (5) is placed in a muffle furnace and sintered at 1550℃ for 20h to obtain a ceramic sheet;

[0081] (7) Acid washing to remove impurities: After grinding the ceramic pieces obtained in step (6) into powder in a mortar, the powder is added to 0.8 mol / L sulfuric acid and heated at 150°C for 90 minutes. Then, the product is obtained by filtration and washing.

[0082] Figure 1-5The XRD patterns of the target products prepared in Examples 1-5 are shown below. As can be seen from the XRD patterns, the target products prepared in Examples 1-5 all match the standard Sr5Nb5O. 17 The PDF card indicates that the target product prepared in Examples 1-5 of this invention is Sr5Nb5O. 17 Phase materials; in addition, Figures 1-5 Sr5Nb5O 17 The structure of the phase material before and after acid leaching is basically the same. In other words, acid leaching does not cause Sr5Nb5O 17 With the alteration of the phase material structure, the SrMoO4 ​​impurity was removed, further yielding Sr5Nb5O with a five-layered perovskite structure. 17 Phase materials.

[0083] In addition, the present invention also uses the Sr5Nb5O with a five-layer structure prepared in Example 3. 17 The phase material was used as a sample and subjected to scanning electron microscopy, transmission electron microscopy, and second harmonic distortion (HTD) testing. Figure 6 The image shows the microstructure and elemental distribution of the sample prepared in Example 3 under a scanning electron microscope. Figure 7 It is the Sr5Nb5O with a five-layer structure prepared in Example 3. 17 Transmission electron microscopy (TEM) images of the phase materials, where (a) is the electron diffraction (SAED) pattern of the material prepared in Example 3 along the

[001] projection direction, indicating that Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The sample after acid washing to remove SrMoO4 ​​has a five-layered perovskite structure; (b) is the elemental distribution (EDS) diagram of the material prepared in Example 3 under transmission electron microscopy. It can be seen from the EDS that after acid washing, the signal of Mo is very weak, and the other elements are uniformly distributed. Figure 8 This is a second harmonic generation (SHG) test pattern of the sample prepared in Example 3. Second harmonic signals appear in non-centrosymmetric materials, so the symmetry of the material can be verified by measuring SHG. Figure 8 The intensity of the SHG signal I is proportional to the square of the incident light power, exhibiting second-order nonlinear optical behavior, indicating that the five-layer structure sample has a non-centrosymmetric crystal structure.

[0084] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A Sr5Nb5O 17 Method for producing a material of a phase, characterized by Oxygen vacancies were created by doping with metal cations to obtain Sr5Nb5O with a five-layer structure. 17 The specific preparation steps for the polycrystalline powder-based material are as follows: (1) Preparation of raw materials: according to Sr2Nb 1.6 Ga 0.2 Mo 0.2 O 6.9 The molar ratio of Sr, Nb, Ga, and Mo in the raw materials SrCO3, Nb2O5, Ga2O3, and MoO3 is determined. (2) Grinding: Grind the raw materials prepared in step (1) in a liquid grinding medium. After grinding evenly, dry the mixed slurry to obtain a mixture powder. (3) Tableting: The mixture powder obtained in step (2) is pressed into tablets to obtain sample tablet A; (4) Pre-firing: The sample A obtained in step (3) is pre-firing at a temperature of 1000~1300℃ for 2~20h to obtain the pre-firing sample; (5) Secondary grinding and tableting: The pre-calcined sample obtained in step (4) is ground in liquid grinding medium and then dried to obtain a powder sample after secondary grinding. The powder sample after secondary grinding is then pressed into tablets to obtain sample tablet B. (6) Sintering: The sample sheet B obtained in step (5) is sintered at a temperature of 1350~1550℃ for 6~20h to obtain a ceramic sheet. (7) Acid washing to remove impurities: After grinding the ceramic sheet obtained in step (6) into powder, the powder is added to 0.05~0.8 mol / L sulfuric acid, and then heated. After heating, it is filtered and washed to obtain the target product, namely Sr5Nb5O with a five-layered layered perovskite structure. 17 Phase materials.

2. The production method according to claim 1, characterized by, The purity of SrCO3, Nb2O5, Ga2O3 and MoO3 in step (1) is above 99.50% by mass.

3. The preparation method according to claim 1, characterized in that, The liquid grinding medium in steps (2) and (5) is anhydrous ethanol or pure water.

4. The method of claim 1, wherein, The grinding time in steps (2) and (5) is 30 to 120 minutes.

5. The preparation method according to claim 1, characterized in that, The mixture powder in step (3) and the powder sample after secondary grinding in step (5) are pressed into tablets under a pressure of 1~8 MPa.

6. The method of claim 1, wherein, In step (7), the heating temperature is 50~150℃ and the heating time is 10~90 minutes.

Images