Preparation method of B-site doped perovskite oxide nanotube

Abstract

The invention discloses a preparation method of a B-site doped perovskite oxide nanotube, which is characterized in that a plurality of metal salts are used as raw materials, PVP (Polyvinyl Pyrrolidone) is used as a structure-directing agent, a liquid nitrogen rapid curing technology is combined with high-temperature roasting, and the inner diameter of the prepared perovskite oxide nanotube is 1t; 10 nm; the method is simple to operate, does not need a template, does not need special professional equipment, and provides a technical method for application of perovskite in multiple fields.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and in particular relates to a method for preparing a B-site doped perovskite oxide nanotube. Background Art

[0002] Perovskite oxide is a densely packed oxide with a structure similar to CaTiO3. It is favored by researchers for its diversified elements, low price, abundant reserves, and stable structure. In addition, perovskite oxide has unique physical and chemical properties such as ferroelectricity, superconductivity, high thermal conductivity, and fluorescence due to the coupling and strong correlation between its lattice, charge, orbit, and spin. It is widely used in ferroelectrics, high-temperature superconductivity, solar cells, and multiphase catalysis. Although perovskite covers many elements and many types of compounds, there are very few species that exist directly in nature, so most perovskite oxides need to be synthesized.

[0003] Commonly used perovskite synthesis methods include solid phase synthesis, mechanical synthesis, hydrothermal synthesis, sol-gel method, etc. The solid phase synthesis method is to use oxide powder or metal carbonate as raw materials, and then grind, mix and treat at high temperature to obtain the perovskite oxide material. The perovskite oxide material obtained by this method has a symmetrical structure and has certain advantages; however, this method requires a high temperature, and the product particles are seriously aggregated. Mechanical synthesis is a preparation method that continuously grinds the initial raw materials at high speed. This method mixes the raw materials more evenly, can control the particles at the micro-nano scale, and can synthesize substances that are difficult to synthesize at room temperature and pressure, but has high requirements for equipment. The hydrothermal synthesis method uses water as a solvent and conducts chemical reactions under sealed, high temperature and high pressure conditions. It has unique advantages in synthesizing some perovskite oxides with special structures. The sol-gel method uses alkoxides, inorganic salts and nitrates as raw materials, mixes the raw materials evenly in a solution, adjusts the pH of the solution to hydrolyze and condense them, and then forms a sol, which is then dehydrated, dried and calcined at high temperature. The products obtained by the above-mentioned perovskite synthesis methods are mostly irregular and in the form of aggregated particles, which greatly hinders the multi-field application of perovskite oxides.

[0004] Perovskite oxides with one-dimensional nanotube structures are of great significance for constructing new nanodevices and in-depth research on the physical nature of size effects. At present, the main preparation method of perovskite oxide nanotubes is the molten salt method, which is to heat and calcine the salt and reactants mixed in proportion at the same time, and the reactants are reacted in liquid molten salt. After cooling and washing, the corresponding products can be obtained. The molten salt method has the advantages of low reaction temperature, short reaction time and high product purity, but the process is complicated and the yield is low. Summary of the invention

[0005] The invention provides a method for preparing B-site doped perovskite oxide nanotubes. The method uses lanthanum nitrate and acetate of metal A as raw materials, doping Fe ions or Cu ions, using polyvinyl pyrrolidone (PVP) as a structure directing agent, and combining liquid nitrogen rapid solidification technology with high-temperature calcination. The method is simple to operate, does not require special professional equipment, and solves the problem of complex perovskite oxide nanotube preparation process in the prior art.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a B-site doped perovskite oxide nanotube comprises the following steps:

[0008] 1) using lanthanum nitrate and acetate of metal A as raw materials, using deionized water as solvent, adding polyvinyl pyrrolidone (PVP) as a structure directing agent, ultrasonicating and stirring to form a uniform solution A, wherein the metal A is one of cobalt, nickel and manganese;

[0009] 2) adding acetate of metal B to solution A in step 1), and stirring by ultrasonication until a uniform solution B is formed, wherein the metal B is iron or copper;

[0010] 3) The solution B in step 2) is rapidly solidified by cooling with liquid nitrogen, and then calcined at 600-900° C. in an inert atmosphere for 4-6 hours to obtain a B-site doped perovskite oxide nanotube sample, which is ground and set aside.

[0011] Preferably, in step 1), the polyvinylpyrrolidone (PVP) is selected from PVPs with different molecular weights, selected from one of PVP-K15, PVP-K30, and PVP-K40.

[0012] Preferably, in step 1), the polyvinyl pyrrolidone accounts for 0.1% to 1.5% of the molar ratio of lanthanum nitrate.

[0013] Preferably, in step 3), the curing time is 1 min to 5 min.

[0014] Preferably, in step 3), the inert atmosphere is one of nitrogen and argon.

[0015] Preferably, the ratio of lanthanum atoms to the sum of metal A and metal B atoms in lanthanum nitrate is 1:1; based on the total atomic fraction of metal A and metal B being 100%, the atomic fraction of metal A is 60-90%, and the rest is metal B.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention proposes a method for preparing B-site doped perovskite oxide nanotubes, wherein the doping ions can be Fe ions or Cu ions. The method is simple to operate, does not require a template, and does not require special professional equipment, thus providing a technical method for the application of perovskite in multiple fields.

[0018] (2) The method of the present invention uses PVP as a structure directing agent, and after rapid cooling and solidification with liquid nitrogen and high-temperature calcination, the inner diameter of the prepared B-site doped perovskite oxide nanotubes is less than 10 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The LaCo prepared in Example 1 0.9 Fe 0.1 TEM image of O3 perovskite oxide nanotubes.

[0020] Figure 2 The LaCo prepared in Example 1 0.9 Fe 0.1 XRD pattern of O3 perovskite oxide nanotubes.

[0021] Figure 3 This is a TEM image of the perovskite oxide nanotubes prepared in Comparative Example 1. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] LaCo 0.9 Fe 0.1 The preparation of O3 perovskite oxide nanotubes is carried out according to the following steps:

[0025] (1) 40 mmol of lanthanum nitrate and 36 mmol of cobalt acetate were used as raw materials, deionized water was used as solvent, PVP-K40 was added at a ratio of 0.1% of the molar ratio of lanthanum nitrate, and ultrasonication and stirring were performed to form a uniform solution A;

[0026] (2) adding 4 mmol of ferric acetate to the solution A of step (1), and stirring by ultrasonication until a uniform solution B is formed; wherein the atomic ratio of metal cobalt to metal iron is 9:1;

[0027] (3) The solution B in step (2) was rapidly solidified by liquid nitrogen cooling and solidification, and the solidification time was 1 min; the solidified sample was directly placed in a nitrogen atmosphere and calcined at 600° C. for 4 hours to obtain a solid product, which was ground and set aside.

[0028] The prepared solid product was physically characterized and the results are shown in Figure 1 and Figure 2 . Figure 1 The prepared LaCo 0.9 Fe 0.1 TEM image of O3 perovskite oxide nanotubes. From the image, it can be seen that the prepared material has a one-dimensional structure with an inner diameter of <10 nm, which shows that the method of the present invention can be used to prepare perovskite oxide nanotubes and is feasible. Figure 2 For LaCo 0.9 Fe 0.1 XRD patterns of O3 perovskite oxide nanotubes, LaCo 0.9 Fe 0.1 The O3 perovskite oxide nanotube samples have characteristic peaks at 23.1°, 33.1°, 40.4°, 47.4°, 53.7°, and 59.5°, corresponding to the (110), (112), (020), (220), (231), and (332) crystal planes, respectively. By comparing with the XRD pattern of LaCoO3, it can be seen that LaCo 0.9 Fe 0.1 The characteristic peak of O3 perovskite oxide nanotubes shifted negatively, which was attributed to the doping of Fe ions.

[0029] Example 2

[0030] Refer to Example 1, except that in step (2), copper acetate is added to solution A, that is, the doping ions are Cu ions, and the other steps are the same as in Example 1. The prepared product is LaCo 0.9 Cu 0.1 O3.

[0031] Example 3

[0032] Refer to Example 1, except that in step (1), the PVP added is PVP-K30, and the other steps are the same as Example 1.

[0033] Example 4

[0034] Refer to Example 1, except that in step (1), cobalt acetate is replaced by nickel acetate, and the other steps are the same as in Example 1. The prepared product is LaNi 0.9 Fe 0.1 O3.

[0035] Example 5

[0036] Refer to Example 1, except that in step (1), cobalt acetate is replaced by manganese acetate, and the other steps are the same as in Example 1. The prepared product is LaMn 0.9 Fe 0.1 O3.

[0037] Example 6

[0038] Refer to Example 1, except that in step (3), the solidified sample is calcined at 900°C in a nitrogen atmosphere for 6 hours, and the other steps are the same as in Example 1. The prepared product is LaCo 0.9 Fe 0.1 O3.

[0039] Example 7

[0040] Refer to Example 1, except that in step (2), the atomic ratio of metal cobalt to metal iron is 6:4, and the other steps are the same as in Example 1. The prepared product is LaCo 0.6 Fe 0.4 O3.

[0041] Example 8

[0042] Refer to Example 1, except that in step (3), the curing time is 5 minutes, and the other steps are the same as in Example 1. The prepared product is LaCo 0.9 Fe 0.1 O3.

[0043] Comparative Example 1:

[0044] Refer to Example 1, except that: in step (3), the solution B in step (2) is solidified by heating and boiling; the solidified sample is directly placed in a nitrogen atmosphere at 600° C. for 4 hours to obtain a solid product, which is ground and used for later use. The other steps are the same as in Example 1.

[0045] The solid product prepared in Comparative Example 1 was characterized by TEM. Figure 3 It can be seen that compared with the liquid nitrogen cooling and solidification adopted in the present invention, the nanotube-like structure of the sample prepared by the temperature-raising boiling method is more obviously agglomerated, and the dispersion is not as good as the nanotubes prepared by the present invention.

Claims

1. A method for preparing B-site doped perovskite oxide nanotubes, characterized in that: The following steps are involved: 1) Lanthanum nitrate and acetate of metal A are used as raw materials, deionized water is used as solvent, polyvinyl pyrrolidone is added, and ultrasonication and stirring are performed to form a uniform solution A, wherein the metal A is one of cobalt, nickel, and manganese; 2) adding acetate of metal B to solution A in step 1), and stirring by ultrasonication until a uniform solution B is formed, wherein the metal B is iron or copper; 3) The solution B in step 2) is rapidly solidified by cooling with liquid nitrogen, and then calcined at 600-900° C. in an inert atmosphere for 4-6 hours to obtain a B-site doped perovskite oxide nanotube sample.

2. The method according to claim 1, characterized in that In step 1), the polyvinyl pyrrolidone is selected from polyvinyl pyrrolidone K15, polyvinyl pyrrolidone K30 and polyvinyl pyrrolidone K40.

3. The method according to claim 1, characterized in that In step 1), the polyvinyl pyrrolidone accounts for 0.1% to 1.5% of the molar ratio of lanthanum nitrate.

4. The method according to claim 1, characterized in that: In step 3), the curing time is 1 min to 5 min.

5. The method according to claim 1, characterized in that In step 3), the inert atmosphere is one of nitrogen and argon.

6. The method according to claim 1, characterized in that The ratio of lanthanum atoms to the sum of metal A and metal B atoms in lanthanum nitrate is 1:1; based on the total atomic fraction of metal A and metal B being 100%, the atomic fraction of metal A is 60-90%, and the rest is metal B.

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