1. The preparation method of the multilayer BMN dielectric thin film material is characterized in that the molecular formula of the thin film material is Bi_1.5MgNb_1.5O₇The preparation method comprises the following process steps:

preparation of precursor solution A:

the precursor liquid A is Nb⁵⁺A solution;

preparing a precursor liquid B and a precursor liquid C:

the precursor liquid B is Bi³⁺Solution, the precursor solution C is Mg²⁺A solution;

preparation of BMN thin films:

preparing BMN sol, and then depositing a plurality of layers of BMN films on a substrate by taking the BMN sol as a raw material to finally obtain the BMN multilayer dielectric film material.

2. The method of claim 1, wherein the BMN multilayer dielectric thin film material is oriented at 222.

3. The method according to claim 1, wherein the preparation of the precursor liquid a in step 1 specifically comprises the steps of:

(1) mixing Nb with₂O₅Mixing with hydrofluoric acid to obtain NbF₅Solution for later use;

(2) the NbF obtained above was diluted with water₅Solution to obtain diluted NbF₅Solution for later use;

(3) diluting NbF obtained in the above₅The solution is filtered by suction to obtain Nb (OH)₅Precipitating;

(4) nb (OH)₅Adding the precipitate into citric acid aqueous solution to carry out complexation reaction, thus obtaining precursor solution A.

4. The method of manufacturing according to claim 3, wherein the Nb is₂O₅The molar ratio of the hydrofluoric acid to the hydrofluoric acid is 1: 10-13; the citric acid and Nb⁵⁺The molar ratio of (A) to (B) is 5-7: 1; the conditions of the complexation reaction are as follows: the temperature is 60-90 ℃, and the reaction time is 30-120 min.

5. The method according to claim 3, wherein the precursor liquid B is BiCl₃The precursor solution C is MgCl₂Solution of said Nb₂O₅、BiCl₃、MgCl₂The molar ratio of (a) to (b) is 3-4: 6: 4.

6. The method according to claim 1, wherein the step 3 of preparing the BMN thin film specifically comprises the following steps:

preparation of BMN sol:

respectively adding the prepared precursor liquid B and the precursor liquid C into the prepared precursor liquid A, adjusting the solution to be weakly acidic to obtain a mixed solution, adding a stabilizer into the mixed solution, stirring for reaction and aging to obtain BMN sol for later use;

depositing a plurality of BMN thin films on a substrate:

and coating a film on a Si substrate by using the prepared BMN sol as a raw material, then carrying out annealing heat treatment, generating a film on the substrate after cooling, then repeating the processes of coating and annealing heat treatment, and depositing a plurality of BMN films on the substrate to finally obtain the BMN multilayer dielectric film material.

7. The method according to claim 6, wherein the mixed solution has a pH of 6.5; the stabilizing agent is ethylene glycol, and the mole ratio of the ethylene glycol to the citric acid is 1-4: 1; the stirring reaction conditions are as follows: stirring for 1-3 hours in a water bath at 70-90 ℃; the aging conditions are as follows: the time is 24-48 h at room temperature.

8. The method according to claim 6, wherein the substrate is an ITO and P-type Si substrate; the coating mode is a spin coating method; the specific process conditions of the coating are as follows: the rotating speed is 1000-2000 r/min during glue dripping, the rotating speed is 2500-4000 r/min during glue throwing, the glue throwing lasts for 30-50 s each time, and the coating amount is 1-1.5 mL each time.

9. The method according to claim 6, wherein the annealing temperature is 500 to 700 ℃ and the annealing time is 80 to 120 min; the sequence of the repeated coating and annealing heat treatment processes is coating → annealing heat treatment →.. 7 layers of coating → annealing heat treatment, the coating is repeated, after each annealing heat treatment, the obtained film is cooled to room temperature, and then the coating and annealing heat treatment processes are repeated.

10. A multilayer BMN dielectric thin film material prepared by the preparation method of any one of claims 1 to 9.

Background

The rapid development of wireless technology over the past decade has greatly stimulated research into new dielectric materials suitable for use in developing mobile and satellite communications. In the microwave frequency range, the dielectric material of these devices for information and communication technology should preferably have a large dielectric constant, low dielectric loss, small leakage current and stable temperature coefficient of resonance frequency (TCF), so as to satisfy the requirements of miniaturization and high efficiency. This aspect has also become a necessary trend in the scientific development of today.

The dielectric constant of the dielectric material can change along with the change of the electric field, and based on the change, the circuit of the material device can be tuned. Materials having dielectric tunability are largely classified into dielectric materials having ferroelectricity and dielectric materials having non-ferroelectricity. Ferroelectric materials with dielectric tunability are mainly focused on BST (Ba) with perovskite structure_xSr_1-xTiO₃) On ferroelectric thin films, BST thin film materials typically have high dielectric constants, fast electric field effects, and large dielectric tuning rates, as analyzed by numerous investigators reports. However, the dielectric loss of the material is high, and researchers modify BST materials dielectrically by doping and complexing, but the effect is very little, and most modifications are at the cost of reducing the dielectric constant of the material, so that it is a need and trend to develop a novel tunable dielectric material with low loss.

In recent years, non-ferroelectric materials with dielectric tunability have been discovered, of which the representative material is BZN (Bi) with pyrochlore structure_1.5ZnNb_1.5O₇) According to the research of scholars, BZN material has moderate dielectric constant and very low dielectric loss, but the higher dielectric tuning rate needs to be loaded with very high bias electric fieldThis limits the integration application of BZN thin film materials. And Zn in the BZN material is volatile at high temperature, and the stoichiometric ratio is not easy to control. Using Mg²⁺Substitute Zn in BZN material²⁺Due to Mg²⁺Specific ratio of Zn to Zn²⁺The prepared BMN dielectric material also has a cubic pyrochlore structure and is a non-ferroelectric material. The material keeps the low dielectric loss characteristic of the BZN material, and has moderate dielectric constant and better temperature stability. Therefore, the BMN thin film material is a valuable novel medium adjustable material, and has a great application prospect in the communication field, especially in a varactor.

The preparation method of the BMN dielectric film material has various methods, mainly comprises a physical deposition method and a chemical deposition method. The physical deposition method is currently applied in many cases, such as sputtering, Molecular Beam Epitaxy (MBE), Pulsed Laser Deposition (PLD), and the like. The MBE method has good film forming uniformity, few defects and easy control of stoichiometric ratio, but has expensive equipment, complex operation, more limitation by external conditions (such as a crucible) and difficulty in preparing materials with high melting points and complex components. The PLD method has the advantages of high film forming speed and low cost in preparing oxide film, but the film has poor uniformity and many defects, and is not suitable for preparing large-area film materials. The magnetron sputtering method has slow growth speed, different sputtering rates corresponding to different materials, a certain difference between the components of the obtained film and the components of the target material, and the microstructure and the component uniformity of the film are to be improved. The chemical deposition method is mainly classified into vapor deposition and solution deposition. The film prepared by vapor deposition can accurately control components, has good uniformity, and can be used for preparing large-area films. However, the method is expensive in equipment, and the required precursor liquid is not easy to synthesize and purify. In contrast, the chemical solution deposition method uses simple equipment and is low in price, and high-quality thin film materials can be prepared.

The Sol-Gel method (Sol-Gel) is one of the most commonly used chemical solution deposition methods. The method comprises dissolving several metal alkoxides, organic salts or inorganic compounds in a suitable solvent to form a solution, forming a polymer sol by hydrolysis and polymer reaction, coating the sol on a substrate by pulling, spin coating, brush coating, etc., volatilizing the organic solvent at high temperature, and crystallizing the particles.

According to related research reports, the solution systems for preparing the BMN thin film material by the sol-gel method are mainly divided into two types: one is a metal alkoxide system; the second is a non-alkoxide system. Metal alkoxides are expensive, very susceptible to hydrolysis, and difficult to store. In the experiment, the operation of the metal alkoxide requires a harsh environment and must be performed in a vacuum glove box filled with nitrogen or inert gas. Therefore, the research on preparing the BMN thin film material by adopting the sol-gel non-alkoxide method has great significance, on one hand, the cost can be reduced, the requirements of experimental equipment can be reduced, and on the other hand, the research blank in the field can be filled.

Disclosure of Invention

The invention aims to provide a multi-layer dielectric thin film material-Bi with low dielectric constant and high quality factor_1.5MgNb_1.5O₇The preparation method is a sol-gel method, has the advantages of simple preparation process, no pollution in the process and low production cost, can obviously improve the dielectric property, and has wide application prospect.

In order to achieve the purpose, the invention adopts the following technical scheme:

BMN in the invention are all Bi_1.5MgNb_1.5O₇For short.

A multilayer BMN dielectric thin film material with the molecular formula of Bi_1.5MgNb_1.5O₇The orientation of the film material is 222, the crystal grain orientation of the dielectric film material is controllable, and the dielectric film material can be used for manufacturing devices such as dielectric resonators, filters, varactors and the like and can be applied to the field of communication. The invention also discloses a preparation method of the sol-gel non-alkoxide system of the multilayer BMN microwave dielectric thin film material, which comprises the following steps:

(1) preparation of precursor solution A:

the precursor liquid A is Nb⁵⁺A solution;

(2) preparing a precursor liquid B and a precursor liquid C:

the precursor liquid B is Bi³⁺Solution, the precursor solution C is Mg²⁺A solution;

(3) preparation of BMN thin films:

preparing BMN sol, and then depositing a plurality of layers of BMN films on a substrate by taking the BMN sol as a raw material to finally obtain the BMN multilayer dielectric film material.

Preferably, the preparation of the precursor liquid a in step 1 specifically comprises the following steps:

(1) mixing Nb with₂O₅Mixing with hydrofluoric acid to obtain NbF₅Solution for later use;

(2) the NbF obtained above was diluted with water₅The solution was then adjusted to pH 6 to obtain diluted NbF₅Solution for later use;

(3) diluting NbF obtained in the above₅The solution is filtered by suction to obtain Nb (OH)₅Precipitating;

(4) nb (OH)₅Adding the precipitate into citric acid aqueous solution to carry out complexation reaction, thus obtaining precursor solution A.

Preferably, the Nb is₂O₅The molar ratio of the hydrofluoric acid to the hydrofluoric acid is 1: 10-13; the citric acid and Nb⁵⁺The molar ratio of (A) to (B) is 5-7: 1; the conditions of the complexation reaction are as follows: the temperature is 60-90 ℃, and the reaction time is 30-120 min.

Preferably, the precursor liquid B is BiCl₃The precursor solution C is MgCl₂Solution of said Nb₂O₅、BiCl₃、MgCl₂The molar ratio of (a) to (b) is 3-4: 6: 4.

Preferably, the preparation of the BMN thin film in step 3 specifically includes the following steps:

(1) preparation of BMN sol:

respectively adding the prepared precursor liquid B and the precursor liquid C into the prepared precursor liquid A, adjusting the solution to be weakly acidic to obtain a mixed solution, adding a stabilizer into the mixed solution, stirring for reaction and aging to obtain BMN sol for later use;

(2) depositing a plurality of BMN thin films on a substrate:

respectively coating films on different substrates by using the prepared BMN sol as a raw material, then carrying out annealing heat treatment, generating a film on the substrate after cooling, then repeating the processes of coating and annealing heat treatment, and depositing a plurality of layers of BMN films on the substrate to finally obtain the BMN multilayer dielectric film material.

Preferably, the pH of the mixed solution is 6.5; the stabilizing agent is ethylene glycol, and the mole ratio of the ethylene glycol to the citric acid is 1-4: 1; the stirring reaction conditions are as follows: the stirring reaction conditions are as follows: stirring for 1-3 hours in a water bath at 70-90 ℃; the aging conditions are as follows: the time is 24-48 h at room temperature.

Preferably, the substrate is an ITO and P-type Si substrate; the coating mode is a spin coating method; the specific process conditions of the coating are as follows: the rotating speed is 1000-2000 r/min during glue dripping, the rotating speed is 2500-4000 r/min during glue throwing, the glue throwing lasts for 30-50 s each time, and the coating amount is 1-1.5 mL each time.

Preferably, 1, the annealing temperature is 500-700 ℃, and the annealing time is 80-120 min; the sequence of the repeated coating and annealing heat treatment processes is coating → annealing heat treatment →.. 7 layers of coating → annealing heat treatment, the coating is repeated, after each annealing heat treatment, the obtained film is cooled to room temperature, and then the coating and annealing heat treatment processes are repeated.

Advantageous effects

In the present invention, we use Nb₂O₅As a niobium raw material, a soluble niobium salt prepared by a citrate method is adopted as a niobium source, magnesium chloride and bismuth chloride are adopted as a magnesium source and a bismuth source, and a chelating agent citric acid, an esterifying agent glycol and p H conditioning agent ammonia water are added to prepare the BMN sol. The preparation method has the advantages of low cost, no toxicity, practicality, safety and the like.

The preparation method of the microwave dielectric thin film material BMN is a sol-gel method, has the advantages of simple preparation process, no pollution in the process and low production cost, can remarkably improve the microwave dielectric property, and has wide application prospect.

The method carries out annealing heat treatment layer by layer on the prepared film, each layer of the film is heated uniformly, the thickness and the BMN particle size of the BMN multilayer dielectric film can be further limited, and the BMN multilayer dielectric film with controllable film thickness and particle size, preferred orientation and uniform high quality is prepared. The microwave dielectric film material prepared by the invention has controllable grain orientation, can be used for manufacturing devices such as dielectric resonators, filters, varactors and the like, and can be applied to the field of communication.

The multilayer BMN dielectric thin film material prepared by the invention has the following excellent properties:

(1) the BMN dielectric film has a cubic pyrochlore structure and good temperature and chemical stability.

(2) The BMN dielectric film has low dielectric loss and moderate dielectric constant.

(3) The BMN dielectric film prepared by the experimental method of the invention has the advantages of compactness, uniformity, uniform particle size, good crystallization, no crack on the surface and no hollow structure.

(4) The BMN dielectric film prepared by the experimental method has controllable grain orientation and can grow along the (222) orientation, and the BMN dielectric film with the (222) orientation is the key for obtaining good dielectric property.

Drawings

FIG. 1 is a process flow diagram for the preparation of BMN sol.

FIG. 2 is a process flow diagram for BMN multilayer dielectric thin film fabrication.

FIG. 3 is an XRD pattern of a BMN multilayer dielectric film prepared at different temperatures according to the present invention.

FIG. 4 is SEM images (in the figure, (a)3 layers of thin films, (b)5 layers of thin films, (c)6 layers of thin films, and (d)7 layers of thin films) of BMN medium thin films with different numbers of layers prepared by the invention;

fig. 5 is a fifty thousand SEM image of BMN dielectric thin films with different numbers of layers prepared according to the present invention (in the figure, (a)3 layers of thin films, (b)5 layers of thin films, (c)6 layers of thin films, and (d)7 layers of thin films).

Detailed Description

The BMN multilayer dielectric thin film and the method for manufacturing the same according to the present invention will be described in detail with reference to the following examples, and the advantages and features of the present invention will become more apparent from the following description. Hereinafter, the present invention will be described in detail. Before the description is made, it should be understood that the terms used in the present specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.

The following examples are given by way of illustration of embodiments of the invention and are not to be construed as limiting the invention, and it will be understood by those skilled in the art that modifications may be made without departing from the spirit and scope of the invention. Unless otherwise specified, reagents and equipment used in the following examples are commercially available products.

In the invention, the raw materials are all conventional commercial products in the field or are prepared by conventional methods in the field if no special indication is given.

Example 1

A multilayer BMN dielectric thin film material with the molecular formula of Bi_1.5MgNb_1.5O₇The orientation of the film material is 222, the crystal grain orientation of the dielectric film material is controllable, and the dielectric film material can be used for manufacturing devices such as dielectric resonators, filters, varactors and the like and can be applied to the field of communication. The preparation method of the sol-gel non-alkoxide system of the multilayer BMN dielectric thin film material comprises the following steps:

1. preparation of precursor solution A:

the precursor solution A is Nb-CA solution, and specifically comprises the following steps:

(1) high-purity (99.90%) Nb is selected₂O₅Adding Nb into a polytetrafluoroethylene container₂O₅Reacting with hydrofluoric acid in an oven at 120 ℃ for 5 hours to obtain NbF₅A solution ofThe molar ratio of niobium oxide to hydrofluoric acid is 1: 10;

(2) the NbF obtained above was diluted with water₅A solution, the pH of which is adjusted with saturated ammonia = 6; then, a mixed solution of saturated ammonium carbonate and ammonia water is used, and the volume ratio is 1: the pH was adjusted to 9 at 10.

(3) Carrying out suction filtration on the solution obtained in the step 2 to obtain Nb (OH)₅Precipitating;

(4) nb (OH)₅Adding the precipitate into citric acid aqueous solution for complex reaction, heating and stirring for 30min under the condition of water bath at 90 ℃ until the precipitate is completely dissolved, thus obtaining precursor solution A-Nb-CA solution. The molar ratio of the citric acid to the niobium ions is 6: 1.

2. preparing a precursor liquid B and a precursor liquid C:

the precursor liquid B is BiCl₃The precursor solution C is MgCl₂The solution specifically comprises the following steps:

adding BiCl₃With MgCl₂Respectively dissolving in HCl and water to obtain precursor solution B and precursor solution C, and Nb₂O₅、BiCl₃、MgCl₂In a molar ratio of 3:6: 4.

3. The preparation of the BMN film specifically comprises the following steps:

(1) preparation of BMN Sol

And (3) slowly and dropwise adding the prepared precursor liquid B and the prepared precursor liquid C into the prepared precursor liquid A respectively, and adjusting the pH value of the solution to be 6.5 to obtain a mixed solution for later use.

And (2) adding ethylene glycol as a stabilizer into the obtained mixed solution to promote the polymerization of the mixed citrate, wherein the mol ratio of the ethylene glycol to the citric acid is 3: 1. then stirring the mixture in a water bath at the temperature of 80 ℃ for 2 hours to obtain BMN sol, and aging the BMN sol for 24 hours. The invention can remove impurities in the sol by aging treatment, improve the purity of the BMN sol and contribute to reducing Bi_1.5MgNb_1.5O₇Dielectric loss of the multilayer dielectric film.

(2) Deposition of multiple BMN thin films on a substrate

The BMN sol prepared above was used as a raw material, and films were coated on ITO and P-type Si substrates, respectively, using a spin coater. The rotating speed is 1000r/min when glue is dripped during film coating, is 3500r/min during glue throwing, and lasts for 50s each time. Annealing the prepared film for 120min at the annealing temperature of 500 ℃, and then repeating the film coating operation after the film is cooled to the room temperature: coating-annealing heat treatment-coating. The coating was repeated for 5 layers. After final stabilization, a thin film of a certain thickness is formed on the substrate.

Example 2

A multilayer BMN dielectric thin film material with the molecular formula of Bi_1.5MgNb_1.5O₇The orientation of the film material is 222, the orientation of the grain of the microwave dielectric film material is controllable, and the microwave dielectric film material can be used for manufacturing devices such as dielectric resonators, filters, varactors and the like and can be applied to the field of communication. The preparation method of the sol-gel non-alkoxide system of the multilayer BMN dielectric thin film material comprises the following steps:

1. preparation of precursor solution A:

the precursor solution A is Nb-CA solution, and specifically comprises the following steps:

(1) high-purity (99.90%) Nb is selected₂O₅Adding Nb into a polytetrafluoroethylene container₂O₅Reacting with hydrofluoric acid in an oven at 120 ℃ for 5 hours to obtain NbF₅The molar ratio of the niobium oxide to the hydrofluoric acid is 1: 13;

(2) the NbF obtained above was diluted with water₅A solution, the pH of which is adjusted with saturated ammonia = 6; then, a mixed solution of saturated ammonium carbonate and ammonia water is used, and the volume ratio is 1: 5, the pH was adjusted to 9.

(3) Carrying out suction filtration on the solution obtained in the step 2 to obtain Nb (OH)₅Precipitating;

(4) nb (OH)₅Adding the precipitate into a citric acid aqueous solution to perform a complexing reaction, wherein the molar ratio of citric acid to niobium ions is 7: 1; heating and stirring for 120min under the condition of water bath at 60 ℃ until the precipitate is completely dissolved, thus obtaining precursor solution A-Nb-CA solution.

2. Preparing a precursor liquid B and a precursor liquid C:

the precursor liquid B is BiCl₃Solutions ofThe precursor liquid C is MgCl₂The solution specifically comprises the following steps:

adding BiCl₃With MgCl₂Respectively dissolving in HCl and water to obtain precursor solution B and precursor solution C, and Nb₂O₅、BiCl₃、MgCl₂In a molar ratio of 4:6: 4.

The preparation of the BMN thin film specifically comprises the following steps:

(2) preparation of BMN Sol

And (3) slowly and dropwise adding the prepared precursor liquid B and the prepared precursor liquid C into the prepared precursor liquid A respectively, and adjusting the pH value of the solution to be 6.5 to obtain a mixed solution for later use.

And (2) adding ethylene glycol as a stabilizer into the obtained mixed solution to promote the polymerization of the mixed citrate, wherein the mol ratio of the ethylene glycol to the citric acid is 4: 1. then stirring the mixture in a water bath at the temperature of 90 ℃ for 1 hour to obtain BMN sol, and aging the BMN sol for 48 hours. The invention can remove impurities in the sol by aging treatment, improve the purity of the BMN sol and contribute to reducing Bi_1.5MgNb_1.5O₇Dielectric loss of the multilayer dielectric film.

(2) Deposition of multiple BMN thin films on a substrate

The BMN sol prepared above was used as a raw material, and films were coated on ITO and P-type Si substrates, respectively, using a spin coater. The rotating speed is 2000r/min when glue is dripped during film coating and 4000r/min during glue throwing, and the glue throwing lasts for 40s each time. Annealing the prepared film for 80min at the annealing temperature of 700 ℃, and then repeating the film coating operation after the film is cooled to the room temperature: coating-annealing heat treatment-coating. The coating was repeated for 6 layers. After final stabilization, a thin film of a certain thickness is formed on the substrate.

Example 3

A multilayer BMN dielectric thin film material with the molecular formula of Bi_1.5MgNb_1.5O₇The orientation of the film material is 222, the crystal grain orientation of the dielectric film material is controllable, and the dielectric film material can be used for manufacturing devices such as dielectric resonators, filters, varactors and the like and can be applied to the field of communication. Dissolving the multilayer BMN dielectric film materialThe preparation method of the gel non-alkoxide system comprises the following steps:

1. preparation of precursor solution A:

the method specifically comprises the following steps:

(1) high-purity (99.90%) Nb is selected₂O₅Adding Nb into a polytetrafluoroethylene container₂O₅Reacting with hydrofluoric acid in an oven at 120 ℃ for 5 hours to obtain NbF₅The molar ratio of the niobium oxide to the hydrofluoric acid is 1: 11;

(2) the NbF obtained above was diluted with water₅A solution, the pH of which is adjusted with saturated ammonia = 6; then, a mixed solution of saturated ammonium carbonate and ammonia water is used, and the volume ratio is 1: 19, the pH was adjusted to 9.

(3) Carrying out suction filtration on the solution obtained in the step 2 to obtain Nb (OH)₅Precipitating;

(4) nb (OH)₅Adding the precipitate into a citric acid aqueous solution for a complexing reaction, wherein the molar ratio of citric acid to niobium ions is 5: 1; heating and stirring for 100min under the condition of 80 ℃ water bath until the precipitate is completely dissolved, thus obtaining precursor solution A-Nb-CA solution.

2. Preparing a precursor liquid B and a precursor liquid C:

the precursor liquid B is BiCl₃The precursor solution C is MgCl₂The solution specifically comprises the following steps:

adding BiCl₃With MgCl₂Respectively dissolving in HCl and water to obtain precursor solution B and precursor solution C, and Nb₂O₅、BiCl₃、MgCl₂In a molar ratio of 3:6: 4.

The preparation of the BMN thin film specifically comprises the following steps:

(3) preparation of BMN Sol

And (3) slowly and dropwise adding the prepared precursor liquid B and the prepared precursor liquid C into the prepared precursor liquid A respectively, and adjusting the pH value of the solution to be 6.5 to obtain a mixed solution for later use.

And (2) adding ethylene glycol as a stabilizer into the obtained mixed solution to promote the polymerization of the mixed citrate, wherein the molar ratio of the ethylene glycol to the citric acid is 1: 1. then stirring the mixture in a water bath at 70 ℃ for 3 hours to obtain a BMN solutionAnd (5) gluing and aging for 24 h. The invention can remove impurities in the sol by aging treatment, improve the purity of the BMN sol and contribute to reducing Bi_1.5MgNb_1.5O₇Dielectric loss of the multilayer dielectric film.

(2) Deposition of multiple BMN thin films on a substrate

The BMN sol prepared above was used as a raw material, and films were coated on ITO and P-type Si substrates, respectively, using a spin coater. The rotating speed is 1500r/min when glue is dripped during film coating and 3000r/min when glue is thrown, and the glue throwing lasts for 30s each time. Annealing the prepared film at the annealing temperature of 600 ℃ for 100min, and then repeating the film coating operation after the film is cooled to the room temperature: coating-annealing heat treatment-coating. The coating was repeated for 7 layers. After final stabilization, a thin film of a certain thickness is formed on the substrate.

Examples of the experiments

In order to prove the excellent performance of the BMN multilayer dielectric thin film of the present invention, the performance of the BMN multilayer dielectric thin film prepared by the present invention is tested, and fig. 3 is an XRD pattern of the BMN multilayer dielectric thin film prepared by the present invention at different annealing temperatures. It can be seen from fig. 3 that (at 500 ℃ annealing temperature, BMN multilayer microwave dielectric film grows with orientation along (400) direction, (222) diffraction peak is weaker, at 600 ℃ annealing temperature, 222) peak is stronger, 400 peak is weaker, with temperature rising, when 700 ℃ is reached, BMN film grows with orientation along (222) direction obviously, 400 diffraction peak is weaker, and BMN film with (222) orientation is key to obtain good dielectric properties.

FIGS. 4 and 5 are SEM images of a BMN multilayer dielectric thin film prepared according to the present invention, as can be seen from FIGS. 4 and 5 (the larger the number of thin film layers is, the larger the grain size in the thin film is, the more the number of thin film layers is 3, the more the thin film is significantly delaminated, which means that the growth distribution of the thin film is not uniform, and the quality of the thin film is not ideal; after comparing 5, 6, and 7, it is found that the thin film is well crystallized and has no cracks at the number of thin film layers of 6, and the more the quality of the thin film is ideal; however, when the number of thin film layers is 7, it can be seen that larger grains are present due to excessive growth, the size of grains is also uneven, and fine cracks are present in the thin film, and the presence of cracks.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.