CN102432283B - Preparation Method of BaTiO3 Composite Film with Grain Boundary Layer Structure - Google Patents

Abstract

The invention discloses a preparation method of a grain boundary layer type structure BaTiO3 composite membrane. In the prepared grain boundary layer type structure, a core is made of barium titanate, a shell layer is made of copper oxide, polystyrene is firstly adopted to wrap the barium titanate to prepare core shell structure microspheres which are utilized to prepare colloid crystals, non-close packed opal type colloid crystals are obtained after the shell layer polystyrene is calcinated to be removed, the non-close packed opal type colloid crystals are soaked in a prepared copper oxide reaction precursor, and the grain boundary layer type structure BaTiO3 composite membrane is obtained after glue drying and calcination.

Description

Preparation Method of BaTiO3 Composite Film with Grain Boundary Layer Structure

technical field

The invention relates to a preparation method of a ceramic membrane, in particular to a preparation method of a grain boundary layer structure BaTiO ₃ composite membrane.

Background technique

With the development of electronic technology towards miniaturization and high density, electronic ceramics have attracted attention due to their unique properties of electricity, magnetism, sound, light, heat and force. According to the structure and principle, semiconductor ceramic capacitors can be divided into two types: surface layer type and grain boundary layer type. An insulating layer is formed at the grain boundaries of the ceramic crystals, thereby forming multiple series and parallel capacitor networks. The series-parallel connection of the device finally obtains a high dielectric constant. _BaTiO3 is a ferroelectric material with extremely high dielectric constant, which has been widely used in multilayer ceramic capacitors and dielectric amplifiers. However, the sintering temperature of BaTiO ₃ is relatively high, so the early sintering process of boundary layer ceramic capacitors is high-temperature secondary firing, which will not only increase energy consumption, cause environmental pollution, but also use high-temperature silver paste, which has a higher cost. However, the method of doping modification, adding flux, and forming low-temperature glass to reduce the sintering temperature of BaTiO ₃ is affected by factors such as powder purity and uneven particle size, and it is difficult to mix uniformly between particles, resulting in uneven microstructure. Uniformity.

Contents of the invention

In order to overcome the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a kind of grain boundary layer structure BaTiO ₃ preparation method of the composite film, the preparation product grain size, uniform distribution, closely combined, and the production process is simple, the cycle is short, The required equipment is simple and the energy consumption is low.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

The first step is to dissolve two equal parts of citric acid in ammonia water with a mass concentration of 25-28%. Barium was dissolved in the above two citric acid solutions respectively to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid was 1:1.5-2.5, and the solution A and the solution B Mix well, add absolute ethanol with 1/3 to 1/2 of the total volume of ammonia water, adjust the pH value to 5.0 to 7.0 with ammonia water, then add polyethylene glycol with 1/3 to 1/2 of the total mass of citric acid, Stir evenly, evaporate in a water bath at 80-90°C to a wet gel, then dry the wet gel at 150°C and calcinate at 700-750°C to obtain barium titanate particles;

In the second step, ultrasonically disperse 3 to 5 g of the obtained barium titanate particles in 50 ml of isopropanol, and add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 2 to 3: 1, Nitrogen is blown, and benzoyl peroxide-isopropanol solution with a concentration of 1-2 mol/L is added dropwise under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 1/2 of the volume of the styrene mixture 1 to 2%, after reacting for 20 to 24 hours, wash the precipitate with toluene and absolute ethanol respectively, and dry at 35 to 40°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene means styrene The amount of substance, n _{barium titanate} represents the amount of substance of barium titanate;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 2 to 3 hours to obtain a suspension with a particle mass fraction of 1% to 2%, and immerse the substrate vertically Placed in a stable suspension, vacuum-dried at 40-50°C, after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate;

The fourth step is to calcinate the core-shell structure colloidal crystals at 400-500°C for 4-6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 100-150°C, and then calcined at 1150-1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

In the third step, the organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol.

The substrate in the third step is glass slide, ITO glass or silicon wafer.

After the film is pulled out in the fifth step, filter paper is used to absorb excess colloid on the surface, and then it is dried.

Compared with the prior art, the present invention wraps barium titanate particles with polystyrene to form core-shell structure particles, assembles the core-shell structure particles to form colloidal crystals, and then obtains non-close-packed opal-type titanic acid after calcination to remove polystyrene Barium colloidal crystals are immersed in a saturated solution of copper nitrate, and then precipitated, dried and dehydrated, and calcined to obtain a grain boundary layer structure BaTiO ₃ composite film. In this way, the grain size and distribution of each grain in the grain boundary layer structure ceramic film are uniform, and the combination is tight, and it avoids the formation of substances such as barium titanate and grain boundaries that are too fast and the difference between the two speeds is too small. The case of the core-shell structure.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples.

Embodiment one

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 28%. Dissolve in the above two citric acid solutions to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:1.5, fully mix solution A and solution B, Add anhydrous ethanol with 1/3 of the total volume of ammonia water, and adjust the pH value to 7.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C until wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 750°C;

In the second step, ultrasonically disperse 5 g of the obtained barium titanate particles in 50 ml of isopropanol, add styrene under continuous stirring, wherein the molar ratio is n _styrene : n barium _titanate = 3: 1, blow nitrogen, and Under the condition of reflux at 65°C, add dropwise a benzoyl peroxide-isopropanol solution with a concentration of 1mol/L, wherein the volume of the benzoyl peroxide-isopropanol solution is 2% of the volume of the styrene mixture, and after 20 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in ethanol for 2 hours to obtain a suspension with a mass fraction of the particles of 2%. In the suspension, vacuum-dry at 40°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the glass slide;

The fourth step is to calcinate the core-shell structure colloidal crystals at 400°C for 6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 100°C, and then calcined at 1150°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

Embodiment two

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 28%. Dissolve in the above two citric acid solutions to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2.5, fully mix solution A and solution B, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C until wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 700°C;

In the second step, ultrasonically disperse 5 g of the obtained barium titanate particles in 50 ml of isopropanol, add styrene under continuous stirring, wherein the molar ratio is n _styrene : n barium _titanate = 3: 1, blow nitrogen, and Under the condition of reflux at 65°C, add dropwise a benzoyl peroxide-isopropanol solution with a concentration of 2mol/L, wherein the volume of the benzoyl peroxide-isopropanol solution is 2% of the volume of the styrene mixture, and after 24 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 40°C to obtain polystyrene-wrapped barium titanate particles;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in methanol for 3 hours to obtain a suspension with a particle mass fraction of 1%, and vertically immerse the ITO glass into a stable suspension solution, dried in vacuum at 50°C, and after the solution was completely evaporated, a layer of core-shell structure colloidal crystals grew on the surface of the ITO glass;

The fourth step is to calcinate the core-shell structure colloidal crystals at 500°C for 4 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 150°C, and then calcined at 1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

Embodiment three

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 25%, and the ammonia water was determined to be able to dissolve citric acid, and then butyl titanate and barium acetate with a molar ratio of 1:1 were respectively dissolved. Dissolve in the above two citric acid solutions to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2.5, fully mix solution A and solution B, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 6.0 with ammonia water, then add polyethylene glycol with 1/3 of the total mass of citric acid, stir evenly, evaporate in a 90°C water bath to a wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 700°C;

In the second step, ultrasonically disperse 3 g of the obtained barium titanate particles in 50 ml of isopropanol, and add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 2: 1, nitrogen, in Under the condition of reflux at 65°C, add dropwise a benzoyl peroxide-isopropanol solution with a concentration of 1mol/L, wherein the volume of the benzoyl peroxide-isopropanol solution is 1% of the volume of the styrene mixture, and after 24 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in acetone for 2 hours to obtain a suspension with a mass fraction of 2% of the particles, and vertically immerse the silicon wafer in a stable suspension solution, dried in vacuum at 50°C, and after the solution was completely evaporated, a layer of core-shell structure colloidal crystals grew on the surface of the silicon wafer;

The fourth step is to calcinate the core-shell structure colloidal crystals at 450°C for 5 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 100°C, and then calcined at 1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

Embodiment four

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 26%. Dissolve in the above two citric acid solutions to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:1.5, fully mix solution A and solution B, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 85°C to a wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 720°C;

In the second step, ultrasonically disperse 5 g of the obtained barium titanate particles in 50 ml of isopropanol, add styrene under continuous stirring, wherein the molar ratio is n _styrene : n barium _titanate = 3: 1, blow nitrogen, and Add dropwise a benzoyl peroxide-isopropanol solution with a concentration of 1.5mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 1% of the volume of the styrene mixture, and react for 20 hours Finally, the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in acetonitrile for 3 hours to obtain a suspension with a mass fraction of 2% of the particles. In the suspension, vacuum-dry at 45°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the glass slide;

The fourth step is to calcinate the core-shell structure colloidal crystals at 450°C for 4 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 120°C, and then calcined at 1200°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

Embodiment five

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 27%. Dissolve in the above two citric acid solutions to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2, fully mix solution A and solution B, Add anhydrous ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 6.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C to a wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 700°C;

In the second step, 4 g of the obtained barium titanate particles were ultrasonically dispersed in 50 ml of isopropanol, and styrene was added under continuous stirring, wherein the molar ratio was n _styrene : n _{barium titanate} = 2.5: 1, and nitrogen gas was used to Under the condition of reflux at 65°C, add dropwise a benzoyl peroxide-isopropanol solution with a concentration of 1mol/L, wherein the volume of the benzoyl peroxide-isopropanol solution is 2% of the volume of the styrene mixture, and after 20 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in isopropanol for 3 hours to obtain a suspension with a mass fraction of 1% of the particles. ITO glass is vertically immersed in a stable In the suspension, dry it in vacuum at 40°C. After the solution is completely evaporated, a layer of core-shell structure colloidal crystals grows on the surface of the ITO glass;

The fourth step is to calcinate the core-shell structure colloidal crystals at 500°C for 6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 150°C, and then calcined at 1150°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

Embodiment six

The preparation method of grain boundary layer structure BaTiO ₃ composite film comprises the following steps:

In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 28%. Dissolve in the above two citric acid solutions to form solution A and solution B, the molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2.5, fully mix solution A and solution B, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 with ammonia water, then add polyethylene glycol with 1/3 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C until wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 750°C;

In the second step, 5 g of the obtained barium titanate particles were ultrasonically dispersed in 50 ml of isopropanol, and styrene was added under continuous stirring, wherein the molar ratio was n _styrene : n _{barium titanate} = 2: 1, and nitrogen gas was used to Under the condition of reflux at 65°C, add dropwise a benzoyl peroxide-isopropanol solution with a concentration of 1mol/L, wherein the volume of the benzoyl peroxide-isopropanol solution is 1% of the volume of the styrene mixture, and after 24 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles;

The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in ethanol for 2 hours to obtain a suspension with a mass fraction of 1% of the particles, and vertically immerse the silicon wafer in a stable suspension solution, dried in vacuum at 50°C, and after the solution was completely evaporated, a layer of core-shell structure colloidal crystals grew on the surface of the silicon wafer;

The fourth step is to calcinate the core-shell structure colloidal crystals at 400°C for 6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals;

The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in a saturated solution of copper nitrate, add dropwise a NaOH solution with a concentration of 2mol/L under ultrasonic stirring, and the molar ratio of copper nitrate to NaOH is 1:2, and pull it after 30 minutes of reaction. The film is produced, dried and dehydrated at 100°C, and then calcined at 1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film.

In each of the above embodiments, the organic solvent for the ultrasonic dispersion of spherical particles can also have other choices; in each of the embodiments, the substrate can be a glass slide, ITO glass or silicon wafer.

Claims (9)

1. grain boundary layer structure BaTiO ₃ The preparation method of composite film is characterized in that, comprises the following steps: The first step is to dissolve two equal parts of citric acid in ammonia water with a mass concentration of 25-28%. Barium was dissolved in the above two citric acid solutions respectively to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid was 1:1.5-2.5, and the solution A and the solution B Mix well, add absolute ethanol with 1/3 to 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 to 7.0 with ammonia water, then add polyethylene glycol with 1/3 to 1/2 of the total mass of citric acid, Stir evenly, evaporate in a water bath at 80-90°C to a wet gel, then dry the wet gel at 150°C and calcinate at 700-750°C to obtain barium titanate particles; In the second step, ultrasonically disperse 3 to 5 g of the prepared barium titanate particles in 50 ml of isopropanol, and add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 2 to 3:1, Nitrogen is blown, and benzoyl peroxide-isopropanol solution with a concentration of 1-2 mol/L is added dropwise under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 1/2 of the volume of the styrene mixture 1-2%, after reacting for 20-24 hours, wash the precipitate with toluene and absolute ethanol respectively, and dry at 35-40°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene means styrene The amount of substance, n _{barium titanate} represents the amount of substance of barium titanate; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 2 to 3 hours to obtain a suspension with a particle mass fraction of 1% to 2%, and immerse the substrate vertically Placed in a stable suspension, vacuum-dried at 40-50°C, after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate; The fourth step is to calcinate the core-shell structure colloidal crystals at 400-500°C for 4-6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 100-150°C, and then calcined at 1150-1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film; In the third step, the organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol. 2. The preparation method of grain boundary layer structure _{BaTiO3composite} film according to claim 1, characterized in that, in the third step, the substrate is a glass slide, ITO glass or a silicon wafer. 3. grain boundary layer type structure BaTiO according to claim ₁ The preparation method of composite film is characterized in that, after the film is pulled out in the described 5th step, first use filter paper to absorb the superfluous colloid on the surface, and then carry out dry. 4. the preparation method of grain boundary layer structure BaTiO ₃ composite film is characterized in that, comprises the following steps: In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 28%. Dissolve in the above two citric acid solutions to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:1.5. Mix solution A and solution B thoroughly, Add anhydrous ethanol with 1/3 of the total volume of ammonia water, and adjust the pH value to 7.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C to a wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 750°C; In the second step, ultrasonically disperse 5 g of the prepared barium titanate particles in 50 ml of isopropanol, and add styrene under continuous stirring, wherein the molar ratio is n _styrene : n barium _titanate = 3:1, blow nitrogen, and Add dropwise benzoyl peroxide-isopropanol solution with a concentration of 1mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 2% of the volume of the styrene mixture, and after 20 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene represents the amount of styrene, and n _{barium titanate} represents titanic acid the amount of barium substance; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 2 hours to obtain a suspension with a mass fraction of 2% of the particles, and vertically immerse the substrate in a stable suspension solution, dry it under vacuum at 40°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate. The organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol, and the substrate is glass sheet, ITO glass or silicon wafer; The fourth step is to calcinate the core-shell structure colloidal crystals at 400°C for 6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 100°C, and then calcined at 1150°C to obtain a grain boundary layer structure BaTiO ₃ composite film. 5. the preparation method of grain boundary layer structure BaTiO ₃ composite film is characterized in that, comprises the following steps: In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 28%. Dissolve in the above two citric acid solutions to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2.5. Mix solution A and solution B thoroughly, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C until wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 700°C; In the second step, ultrasonically disperse 5 g of the prepared barium titanate particles in 50 ml of isopropanol, and add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 3:1, blow nitrogen, and Add dropwise benzoyl peroxide-isopropanol solution with a concentration of 2mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 2% of the volume of the styrene mixture, and after 24 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 40°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene represents the amount of styrene, and n _{barium titanate} represents titanic acid the amount of barium substance; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 3 hours to obtain a suspension with a particle mass fraction of 1%. The substrate is vertically immersed in a stable suspension solution, dry it under vacuum at 50°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate. The organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol, and the substrate is glass sheet, ITO glass or silicon wafer; The fourth step is to calcinate the core-shell structure colloidal crystals at 500°C for 4 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 150°C, and then calcined at 1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film. 6. The preparation method of grain boundary layer structure BaTiO ₃ composite film, is characterized in that, comprises the following steps: The first step is to dissolve two equal parts of citric acid in ammonia water with a mass concentration of 25%. Dissolve in the above two citric acid solutions to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2.5. Mix solution A and solution B thoroughly, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 6.0 with ammonia water, then add polyethylene glycol with 1/3 of the total mass of citric acid, stir evenly, evaporate in a 90°C water bath to a wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 700°C; In the second step, ultrasonically disperse 3 g of the prepared barium titanate particles in 50 ml of isopropanol, add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 2:1, blow nitrogen, in Add dropwise benzoyl peroxide-isopropanol solution with a concentration of 1mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 1% of the volume of the styrene mixture, and after 24 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene represents the amount of styrene, and n _{barium titanate} represents titanic acid the amount of barium substance; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 2 hours to obtain a suspension with a mass fraction of 2% of the particles, and vertically immerse the substrate in a stable suspension solution, dry it under vacuum at 50°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate. The organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol, and the substrate is glass sheet, ITO glass or silicon wafer; The fourth step is to calcinate the core-shell structure colloidal crystals at 450°C for 5 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 100°C, and then calcined at 1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film. 7. The preparation method of the grain boundary layer structure BaTiO ₃ composite film, is characterized in that, comprises the following steps: In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 26%. Dissolve in the above two citric acid solutions to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:1.5. Mix solution A and solution B thoroughly, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 85°C to a wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 720°C; In the second step, ultrasonically disperse 5 g of the prepared barium titanate particles in 50 ml of isopropanol, and add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 3:1, blow nitrogen, and Add dropwise benzoyl peroxide-isopropanol solution with a concentration of 1.5mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 1% of the volume of the styrene mixture, and react for 20 hours Finally, the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene represents the amount of styrene, and n _{barium titanate} represents titanium the amount of barium acid substance; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 3 hours to obtain a suspension with a mass fraction of 2% of the particles, and vertically immerse the substrate in a stable suspension solution, dried under vacuum at 45°C, and after the solution was completely evaporated, a layer of colloidal crystals with a core-shell structure grew on the surface of the substrate. The organic solvent was ethanol, methanol, acetone, acetonitrile or isopropanol, and the substrate was glass-mounted sheet, ITO glass or silicon wafer; The fourth step is to calcinate the core-shell structure colloidal crystals at 450°C for 4 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 120°C, and then calcined at 1200°C to obtain a grain boundary layer structure BaTiO ₃ composite film. 8. The preparation method of the grain boundary layer structure BaTiO ₃ composite film, is characterized in that, comprises the following steps: In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 27%. Dissolve in the above two citric acid solutions to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2. Mix solution A and solution B thoroughly. Add anhydrous ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 6.0 with ammonia water, then add polyethylene glycol with 1/2 of the total mass of citric acid, stir evenly, evaporate in a water bath at 80°C until wet gel, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 700°C; In the second step, ultrasonically disperse 4 g of the prepared barium titanate particles in 50 ml of isopropanol, add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 2.5: 1, blow nitrogen, in Add dropwise benzoyl peroxide-isopropanol solution with a concentration of 1mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 2% of the volume of the styrene mixture, and after 20 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene represents the amount of styrene, and n _{barium titanate} represents titanic acid the amount of barium substance; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 3 hours to obtain a suspension with a particle mass fraction of 1%. The substrate is vertically immersed in a stable suspension solution, dry it under vacuum at 40°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate. The organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol, and the substrate is glass sheet, ITO glass or silicon wafer; The fourth step is to calcinate the core-shell structure colloidal crystals at 500°C for 6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 150°C, and then calcined at 1150°C to obtain a grain boundary layer structure BaTiO ₃ composite film. 9. The preparation method of the grain boundary layer structure BaTiO ₃ composite film, is characterized in that, comprises the following steps: In the first step, two equal parts of citric acid were dissolved in ammonia water with a mass concentration of 28%. Dissolve in the above two citric acid solutions to form solution A and solution B. The molar ratio of the sum of the moles of butyl titanate and barium acetate to the total amount of citric acid is 1:2.5. Mix solution A and solution B thoroughly, Add absolute ethanol with 1/2 of the total volume of ammonia water, and adjust the pH value to 5.0 with ammonia water, then add polyethylene glycol with 1/3 of the total mass of citric acid, stir evenly, evaporate to wet gel in a water bath at 80°C, and then Barium titanate particles were obtained by drying the wet gel at 150°C and calcining at 750°C; In the second step, ultrasonically disperse 5 g of the prepared barium titanate particles in 50 ml of isopropanol, add styrene under continuous stirring, wherein the molar ratio is n _styrene : n _{barium titanate} = 2:1, blow nitrogen, in Add dropwise benzoyl peroxide-isopropanol solution with a concentration of 1mol/L under reflux at 65°C, wherein the volume of the benzoyl peroxide-isopropanol solution is 1% of the volume of the styrene mixture, and after 24 hours of reaction , the precipitate was washed with toluene and absolute ethanol, and dried at 35°C to obtain polystyrene-wrapped barium titanate particles, where: n _styrene represents the amount of styrene, and n _{barium titanate} represents titanic acid the amount of barium substance; The third step is to ultrasonically disperse the prepared polystyrene-wrapped barium titanate particles in an organic solvent for 2 hours to obtain a suspension with a mass fraction of 1% of the particles, and vertically immerse the substrate in a stable suspension solution, dry it under vacuum at 50°C, and after the solution is completely evaporated, a layer of colloidal crystals with a core-shell structure grows on the surface of the substrate. The organic solvent is ethanol, methanol, acetone, acetonitrile or isopropanol, and the substrate is glass sheet, ITO glass or silicon wafer; The fourth step is to calcinate the core-shell structure colloidal crystals at 400°C for 6 hours to obtain non-close-packed opal BaTiO ₃ colloidal crystals; The fifth step is to immerse the non-close-packed opal BaTiO ₃ colloidal crystal in the saturated solution of copper nitrate, add dropwise NaOH solution with a concentration of 2mol/L under ultrasonic stirring, the molar ratio of copper nitrate and NaOH is 1:2, and pull it after 30 minutes of reaction The film is produced, dried and dehydrated at 100°C, and then calcined at 1250°C to obtain a grain boundary layer structure BaTiO ₃ composite film.