Sol-gel method-based high-temperature superconducting film and preparation method thereof

文档序号：80310 发布日期：2021-10-08 浏览：32次中文

阅读说明：本技术 一种基于溶胶-凝胶法制备高温超导薄膜及制备方法 (Sol-gel method-based high-temperature superconducting film and preparation method thereof ) 是由赵高扬沈明虎雷黎贾纪强于 2021-07-14 设计创作，主要内容包括：本发明公开的一种基于溶胶-凝胶法制备高温超导薄膜的制备方法,如下：步骤1：制备(Bi,Pb)-2223溶胶,然后采用浸渍提拉法在将(Bi,Pb)-2223溶胶涂敷在铝酸镧单晶基板上或钛酸锶单晶基板上制备(Bi,Pb)-2223凝胶薄膜；步骤2：将得到的(Bi,Pb)-2223凝胶薄膜在80℃～100℃下干燥10～20min；步骤3：将制备好的(Bi,Pb)-2223凝胶薄膜在特定的热处理温度和热处理气氛条件下进行热处理,得到(Bi,Pb)-2223高温超导薄膜。还提供该方法制备得到的超导薄膜。该薄膜稳定性好、镀膜效率高。(The invention discloses a preparation method for preparing a high-temperature superconducting film based on a sol-gel method, which comprises the following steps: step 1: preparing (Bi, Pb) -2223 sol, and then coating the (Bi, Pb) -2223 sol on a lanthanum aluminate single-crystal substrate or a strontium titanate single-crystal substrate by adopting a dip-coating method to prepare a (Bi, Pb) -2223 gel film; step 2: drying the obtained (Bi, Pb) -2223 gel film for 10-20 min at the temperature of 80-100 ℃; and step 3: and (Bi, Pb) -2223 gel film is subjected to heat treatment at a specific heat treatment temperature under a heat treatment atmosphere condition to obtain the (Bi, Pb) -2223 high-temperature superconducting film. Also provides a superconducting film prepared by the method. The film has good stability and high film coating efficiency.)

1. A method for preparing a high-temperature superconducting film based on a sol-gel method is characterized by comprising the following steps:

step 1: preparing (Bi, Pb) -2223 sol, and then coating the (Bi, Pb) -2223 sol on a lanthanum aluminate single-crystal substrate or a strontium titanate single-crystal substrate by adopting a dip-coating method to prepare a (Bi, Pb) -2223 gel film;

step 2: drying the obtained (Bi, Pb) -2223 gel film for 10-20 min at the temperature of 80-100 ℃;

and step 3: and (Bi, Pb) -2223 gel film is subjected to heat treatment at a specific heat treatment temperature under a heat treatment atmosphere condition to obtain the (Bi, Pb) -2223 high-temperature superconducting film.

2. The method for preparing a high-temperature superconducting thin film based on the sol-gel method according to claim 1, wherein the specific method for preparing the (Bi, Pb) -2223 sol in the step 1 is as follows:

s1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 8-10 to obtain a bismuth solution;

s2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a lead solution;

s3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a strontium solution;

s4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a calcium solution;

s5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 3-5 to obtain a copper solution;

and (3) mixing the bismuth solution, the lead solution, the strontium solution, the calcium solution and the copper solution obtained in the steps S1-S5 according to the molar ratio of metal ions of 2:0.2:2:1:2, and stirring at room temperature to obtain the (Bi, Pb) -2223 sol.

3. The method for preparing a high-temperature superconducting thin film based on the sol-gel method according to claim 2, wherein the specific implementation method of the step 3 is as follows:

step 3.1, putting the (Bi, Pb) -2223 gel film obtained in the step 2 into a tubular furnace, introducing an atmosphere A into the furnace, and heating to 120-125 ℃ at a speed of 2-10 ℃/min;

step 3.2, after the step 3.1 is finished, raising the temperature in the furnace from 120-125 ℃ in the first step to 580-600 ℃ at the speed of 5-10 ℃/min, preserving the temperature for 60-80 min, and switching the atmosphere A introduced into the furnace into a mixed atmosphere B while raising the temperature;

step 3.3, after the temperature is kept for 60-80 min, the temperature in the furnace is continuously increased to 845-860 ℃ from 580-600 ℃ in the step 3.2 at the speed of 5-10 ℃/min, the mixed atmosphere B introduced into the furnace is switched to the mixed atmosphere C while the temperature is increased, and the temperature is kept for 100-120 min after the temperature is increased to 845-860 ℃;

and 3.4, after preserving the heat for 100-120 min, cooling to room temperature along with the furnace to obtain the (Bi, Pb) -2223 superconducting thin film with the superconducting critical transition temperature of 100-106K.

4. The method according to claim 3, wherein in step 3.1, the atmosphere A is high-purity nitrogen and the flow rate is 1L/min.

5. The method for preparing a high-temperature superconducting thin film based on the sol-gel method as claimed in claim 3, wherein in step 3.2, the mixed atmosphere B is N with a certain humidity₂Atmosphere, wherein the humidity is controlled by passing the atmosphere A during the heat treatment through a water bath at 35-45 deg.C.

6. The method for preparing a high-temperature superconducting thin film based on the sol-gel method according to claim 3, wherein in step 3.3: the mixed atmosphere C comprises the following components in percentage by volume: 2-4% of high-purity oxygen and the balance of high-purity nitrogen, wherein the sum of the volume percentages of the components is 100%.

7. The method for preparing a high-temperature superconducting thin film based on the sol-gel method according to claim 3, wherein the purity of the high-purity nitrogen used in the step 3 is as follows: 99.999 percent; the purity of the high purity oxygen used was: 99.999 percent.

8. A high-temperature superconducting thin film prepared based on a sol-gel method, characterized by being prepared by the preparation method according to any one of claims 1 to 7.

Technical Field

The invention belongs to the technical field of high-temperature superconducting films in the material electronic industry, and particularly relates to a sol-gel method-based preparation method of a high-temperature superconducting film, and a sol-gel method-based preparation method of a high-temperature superconducting film.

Background

The bismuth-based superconductor has important application in the fields of terahertz devices, superconducting quantum interferometers, tunable filters and the like. At present, the research on the high-temperature superconducting terahertz device is mainly focused onBi-2212 (Bi) with lower critical temperature₂Sr₂CaCu₂O_8+δ) Superconductor, intrinsic Josephson effect formed by using its special structure, preparing terahertz radiation source and high-sensitivity detector, and Bi-2223 (Bi) with higher critical temperature₂Sr₂Ca₂Cu₃O_10+δ) The application of the superconductor in the terahertz field is rarely reported, and the preparation of the Bi-2223 material is not well solved mainly because the problems of complex phase structure, narrow phase temperature region, complex preparation process and the like of the Bi-2223 film, so that the research on the preparation method of the Bi-2223 film with the biaxial texture has important significance for the development of high-temperature superconducting devices.

However, in the proposed phase forming mechanism of the Bi-2223 phase, whether it is a disproportionation reaction mechanism, an insertion mechanism, a liquid phase diffusion mechanism or a two-dimensional nucleation growth mechanism, it is widely believed that the Bi-2223 phase is generated by the Bi-2212 phase and some Cu-rich and Ca-rich phases, which leads to the inevitable generation of the Bi-2212 phase in the Bi-2223 film, and the preparation of the pure Bi-2223 film is very difficult. The Sol-Gel method is widely applied to the preparation of the film, the method can realize the sufficient mixing of the raw materials, and the uniformity of the film is also improved. Meanwhile, the method has high efficiency and low cost, can form a film in a large area, and has great industrialization potential.

The high-temperature superconducting film applied to industrial production is required to have good growth orientation, high phase purity, compact structure and excellent electrical properties. Therefore, the preparation of the (Bi, Pb) -2223 high-temperature superconducting film with high purity, good orientation and excellent performance has important significance.

Disclosure of Invention

The invention aims to provide a sol-gel method-based high-temperature superconducting film with good stability.

The second purpose of the invention is to provide a method for preparing a high-temperature superconducting thin film based on a sol-gel method, which can prepare a (Bi, Pb) -2223 thin film with high critical transition temperature and good superconductivity in a large area, and the thin film prepared based on the method has low cost and good stability.

The technical scheme adopted by the invention is that the preparation method for preparing the high-temperature superconducting film based on the sol-gel method comprises the following steps:

step 2: drying the obtained (Bi, Pb) -2223 gel film for 10-20 min at the temperature of 80-100 ℃;

The present invention is also characterized in that,

the specific method for preparing the (Bi, Pb) -2223 sol in the step 1 is as follows:

s1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 8-10 to obtain a bismuth solution;

s2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a lead solution;

s3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a strontium solution;

s4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a calcium solution;

s5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 3-5 to obtain a copper solution;

The specific implementation method of the step 3 is as follows:

step 3.1, putting the (Bi, Pb) -2223 gel film obtained in the step 2 into a tubular furnace, introducing an atmosphere A into the furnace, and heating to 120-125 ℃ at a speed of 2-10 ℃/min;

In step 3.1, atmosphere A is high-purity nitrogen and the flow rate is 1L/min.

In step 3.2, the mixed atmosphere B is N with a certain humidity₂Atmosphere, wherein the humidity is controlled by passing the atmosphere A during the heat treatment through a water bath at 35-45 deg.C.

Step 3.3: the mixed atmosphere C comprises the following components in percentage by volume: 2-4% of high-purity oxygen and the balance of high-purity nitrogen, wherein the sum of the volume percentages of the components is 100%.

In step 3, the purity of the high-purity nitrogen used is as follows: 99.999 percent; the purity of the high purity oxygen used was: 99.999 percent.

The second technical scheme adopted by the invention is that the high-temperature superconducting film is prepared by adopting the preparation method based on the sol-gel method.

The invention has the beneficial effects that:

(1) the preparation method of the invention has good stability and can obtain the (Bi, Pb) -2223 high-temperature superconducting film with excellent performance.

(2) The preparation method has high film coating efficiency and low film preparation cost.

(3) The preparation method has large film forming area and solves the preparation problem of the current (Bi, Pb) -2223 high-temperature superconducting thin film.

Drawings

FIG. 1 is a flow chart of a method for preparing a high-temperature superconducting thin film based on a sol-gel method according to the present invention;

FIG. 2 is a flow chart of the preparation of the (Bi, Pb) -2223 sol in the method of the present invention;

FIG. 3 is a diagram of a thermal treatment process for a (Bi, Pb) -2223 thin film in the method of the present invention;

FIG. 4 is an XRD pattern of the (Bi, Pb) -2223 superconducting thin film obtained in example 1;

FIG. 5 is a Phi scan of the (Bi, Pb) -2223 superconducting thin film obtained in example 1;

FIG. 6 is a.omega.scan of a (Bi, Pb) -2223 superconducting thin film obtained in example 1;

FIG. 7 is an R-T curve of the (Bi, Pb) -2223 superconducting thin film obtained in example 1, the superconducting critical temperature of which is 106K.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The invention provides a preparation method for preparing a high-temperature superconducting thin film based on a sol-gel method, which comprises the following steps of:

the specific method for preparing the (Bi, Pb) -2223 sol in the step 1 is as follows:

s1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 8-10 to obtain a bismuth solution;

s2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a lead solution;

s3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a strontium solution;

s4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 10-12 to obtain a calcium solution;

s5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1: 15-20: 3-5 to obtain a copper solution;

Step 2: drying the obtained (Bi, Pb) -2223 gel film for 10-20 min at the temperature of 80-100 ℃;

The specific implementation method of step 3 is as follows, as shown in fig. 3:

step 3.1, putting the (Bi, Pb) -2223 gel film obtained in the step 2 into a tubular furnace, introducing an atmosphere A into the furnace, and heating to 120-125 ℃ at a speed of 2-10 ℃/min;

in step 3.1, atmosphere A is high-purity nitrogen and the flow rate is 1L/min.

Step 3.2, after the step 3.1 is finished, raising the temperature in the furnace from 120-125 ℃ in the first step to 580-600 ℃ at the speed of 5-10 ℃/min, preserving the temperature for 60-80 min, and switching the atmosphere A introduced into the furnace into a mixed atmosphere B while raising the temperature;

in step 3.2, the mixed atmosphere B is N with a certain humidity₂Atmosphere, wherein the humidity is controlled by passing the atmosphere A during the heat treatment through a water bath at 35-45 deg.C.

Step 3.3, after the temperature is kept for 60-80 min, the temperature in the furnace is continuously increased to 845-860 ℃ from 580-600 ℃ in the step 3.2 at the speed of 5-10 ℃/min, the mixed atmosphere B introduced into the furnace is switched to the mixed atmosphere C while the temperature is increased, and the temperature is kept for 100-120 min after the temperature is increased to 845-860 ℃;

step 3.3: the mixed atmosphere C comprises the following components in percentage by volume: 2-4% of high-purity oxygen and the balance of high-purity nitrogen, wherein the sum of the volume percentages of the components is 100%.

And 3.4, keeping the temperature for 100-120 min, and cooling to room temperature along with the furnace to obtain the (Bi, Pb) -2223 superconducting film.

In step 3, the purity of the high-purity nitrogen used is as follows: 99.999 percent; the purity of the high purity oxygen used was: 99.999 percent.

The invention also provides a high-temperature superconducting film prepared based on the sol-gel method, and the high-temperature superconducting film is prepared by adopting the preparation method.

Example 1

Under the condition of room temperature, preparing (Bi, Pb) -2223 sol by using bismuth acetate, lead acetate, strontium acetate, calcium acetate and copper acetate as raw materials, acrylic acid as a chemical modifier and methanol as a solvent, wherein the specific implementation method comprises the following steps:

step 1.1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:10 to obtain a bismuth solution;

step 1.2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:12 to obtain a lead solution;

step 1.3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:12 to obtain a strontium solution;

step 1.4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:12 to obtain a calcium solution;

step 1.5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:5 to obtain a copper solution;

and (2) mixing the bismuth solution, the lead solution, the strontium solution, the calcium solution and the copper solution obtained in the steps (1) to (5) according to the metal ion molar ratio of 2:0.2:2:1:2, and stirring at room temperature to obtain the (Bi, Pb) -2223 sol.

The (Bi, Pb) -2223 sol prepared by the method is coated on an LAO (001) single crystal substrate by a dip-coating method at room temperature to prepare the (Bi, Pb) -2223 gel film. The (Bi, Pb) -2223 gel film was placed in an oven and dried at 80 ℃ for 10min, after which the (Bi, Pb) -2223 gel film was placed in a tube furnace and heated to 125 ℃ at a rate of 2 ℃/min in an atmosphere of high purity nitrogen (purity 99.999%) at a flow rate of 1L/min. Subsequently, the temperature was raised to 580 ℃ at a rate of 10 ℃/min in a nitrogen atmosphere of a certain humidity (obtained by passing high-purity nitrogen into a water bath at 35 ℃), and the temperature was maintained for 60 min. And finally, rapidly heating to 860 ℃ at the speed of 10 ℃/min in the mixed atmosphere of high-purity oxygen (with the purity of 99.999%) with the volume ratio of 4% and the balance of high-purity nitrogen, and preserving the heat for 120 min. After the heat preservation is finished, the temperature is reduced to the room temperature along with the furnace, and the (Bi, Pb) -2223 superconducting film can be obtained.

The XRD results of the prepared thin film are shown in fig. 4. When the heat treatment temperature was 860 ℃, it was found from the figure that the (00l) characteristic diffraction peak of (Bi, Pb) -2223 appeared, and the film exhibited mainly the (Bi, Pb) -2223 phase, and no impurity phase was formed.

The Phi scanning and omega rocking curve results of the prepared film are shown in FIGS. 5-6, and the (115) crystal plane diffraction peak of the (Bi, Pb) -2223 film is selected to be used for the Phi scanning test, and the (0014) crystal plane diffraction peak is used for the omega scanning test. Phi scanning selects an included angle of a (115) crystal face and a (00l) crystal face of a (Bi, Pb) -2223 phase to be 62.77 degrees, in the process, when a sample inclines 62.77 degrees and then rotates 360 degrees around a c axis, the sample respectively scans the (115) crystal face and the (00l) crystal face at intervals of 90 degrees,Andfour crystal planes. As a result, four diffraction peaks with uniform height and 90 degrees are generated between 0 degree and 360 degrees, and the full width at half maximum FWHM is 1.308 degrees, and the included angle of (Bi, Pb) -2223 crystal grains in an a-b plane is small, so that the epitaxial growth consistency is good. The FWHM value of the (0014) crystal plane omega of (Bi, Pb) -2223 measured by scanning is 0.48 degrees, which shows that the included angle of the (Bi, Pb) -2223 crystal grains in the a-c plane is small, and the epitaxial growth uniformity of the (Bi, Pb) -2223 thin film on the LAO substrate along the c-axis direction is good. The results of this example show that the film produced has good biaxial texture.

The R-T curve of the prepared film is shown in FIG. 7. When the heat treatment temperature is 860 ℃, it can be seen that the Tc of the (Bi, Pb) -2223 thin film is 106K, which is close to the theoretical superconducting transition temperature of Bi-2223, and the Delta Tc is 6K.

Example 2

step 1.1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:15:10 to obtain a bismuth solution;

step 1.2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:15:12 to obtain a lead solution;

step 1.3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:15:12 to obtain a strontium solution;

step 1.4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:15:12 to obtain a calcium solution;

step 1.5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:15:5 to obtain a copper solution;

The (Bi, Pb) -2223 sol prepared by the method is coated on an LAO (001) single crystal substrate by a dip-coating method at room temperature to prepare the (Bi, Pb) -2223 gel film. The (Bi, Pb) -2223 gel film was placed in an oven and dried at 80 ℃ for 10min, after which the (Bi, Pb) -2223 gel film was placed in a tube furnace and heated to 120 ℃ at a rate of 2 ℃/min in an atmosphere of high purity nitrogen (purity 99.999%) at a flow rate of 1L/min. Subsequently, the temperature was raised to 580 ℃ at a rate of 5 ℃/min in a nitrogen atmosphere of a certain humidity (obtained by passing high purity nitrogen into a water bath at 35 ℃), and the temperature was maintained for 60 min. And finally, rapidly heating to 845 ℃ at the speed of 5 ℃/min in the mixed atmosphere of high-purity oxygen (with the purity of 99.999%) with the volume ratio of 2% and the balance of high-purity nitrogen, and preserving the heat for 100 min. After the heat preservation is finished, the temperature is reduced to the room temperature along with the furnace, and the (Bi, Pb) -2223 superconducting film can be obtained.

Example 3

step 1.1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:10 to obtain a bismuth solution;

step 1.2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:12 to obtain a lead solution;

step 1.3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:12 to obtain a strontium solution;

step 1.4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:12 to obtain a calcium solution;

step 1.5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:20:5 to obtain a copper solution;

And (Bi, Pb) -2223 sol prepared by the method is coated on a lanthanum aluminate single crystal substrate by adopting a dip-draw method at room temperature to prepare the (Bi, Pb) -2223 gel film. The (Bi, Pb) -2223 gel film was placed in an oven and dried at 100 ℃ for 20min, after which the (Bi, Pb) -2223 gel film was placed in a tube furnace and heated to 125 ℃ at a rate of 10 ℃/min in an atmosphere of high purity nitrogen (purity 99.999%) at a flow rate of 1L/min. Subsequently, the temperature was raised to 600 ℃ at a rate of 10 ℃/min in a nitrogen atmosphere of a certain humidity (obtained by passing high-purity nitrogen into a water bath at 45 ℃), and the temperature was maintained for 80 min. And finally, rapidly heating to 860 ℃ at the speed of 10 ℃/min in the mixed atmosphere of high-purity oxygen (with the purity of 99.999%) with the volume ratio of 2% and the balance of high-purity nitrogen, and preserving the heat for 120 min. After the heat preservation is finished, the temperature is reduced to the room temperature along with the furnace, and the (Bi, Pb) -2223 superconducting film can be obtained.

Example 4

step 1.1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:18:10 to obtain a bismuth solution;

step 1.2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:18:12 to obtain a lead solution;

step 1.3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:18:12 to obtain a strontium solution;

step 1.4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:18:12 to obtain a calcium solution;

step 1.5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:18:5 to obtain a copper solution;

And (Bi, Pb) -2223 sol prepared by the method is coated on a strontium titanate single crystal substrate by adopting a dip-coating method at room temperature to prepare the (Bi, Pb) -2223 gel film. The (Bi, Pb) -2223 gel film was placed in an oven and dried at 90 ℃ for 15min, after which the (Bi, Pb) -2223 gel film was placed in a tube furnace and heated to 124 ℃ at a rate of 5 ℃/min in an atmosphere of high purity nitrogen (purity 99.999%) at a flow rate of 1L/min. Subsequently, the temperature was raised to 590 ℃ at a rate of 8 ℃/min in a nitrogen atmosphere of a certain humidity (obtained by passing high purity nitrogen through a water bath at 45 ℃), and the temperature was maintained for 70 min. And finally, rapidly heating to 850 ℃ at the speed of 8 ℃/min in the mixed atmosphere of high-purity oxygen (with the purity of 99.999%) with the volume ratio of 3% and the balance of high-purity nitrogen, and preserving the heat for 110 min. After the heat preservation is finished, the temperature is reduced to the room temperature along with the furnace, and the (Bi, Pb) -2223 superconducting film can be obtained.

Example 5

step 1.1, preparation of bismuth solution: mixing bismuth acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:17:10 to obtain a bismuth solution;

step 1.2, preparation of lead solution: adding lead acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:17:12 to obtain a lead solution;

step 1.3, preparation of strontium solution: the ratio of strontium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:17:12 to obtain a strontium solution;

step 1.4, preparation of calcium solution: adding calcium acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:17:12 to obtain a calcium solution;

step 1.5, preparation of copper solution: adding copper acetate: methanol: mixing and stirring acrylic acid in a molar ratio of 1:17:5 to obtain a copper solution;

And (Bi, Pb) -2223 sol prepared by the method is coated on a strontium titanate single crystal substrate by adopting a dip-coating method at room temperature to prepare the (Bi, Pb) -2223 gel film. The (Bi, Pb) -2223 gel film was placed in an oven and dried at 90 ℃ for 15min, after which the (Bi, Pb) -2223 gel film was placed in a tube furnace and heated to 124 ℃ at a rate of 5 ℃/min in an atmosphere of high purity nitrogen (purity 99.999%) at a flow rate of 1L/min. Subsequently, the temperature was raised to 590 ℃ at a rate of 8 ℃/min in a nitrogen atmosphere of a certain humidity (obtained by passing high purity nitrogen through a water bath at 45 ℃), and the temperature was maintained for 70 min. And finally, rapidly heating to 850 ℃ at the speed of 8 ℃/min in the mixed atmosphere of high-purity oxygen (with the purity of 99.999%) with the volume ratio of 3% and the balance of high-purity nitrogen, and preserving the heat for 120 min. After the heat preservation is finished, the temperature is reduced to the room temperature along with the furnace, and the (Bi, Pb) -2223 superconducting film can be obtained.

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Sol-gel method-based high-temperature superconducting film and preparation method thereof

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