CN113402275B - Multilayer BMN dielectric thin film material and preparation method thereof - Google Patents

Abstract

The invention relates to a preparation method of a dielectric film material, in particular to a preparation method of a multilayer dielectric film material with a low dielectric constant. The molecular formula of the film material is Bi _1.5 MgNb _1.5 O ₇ The preparation method comprises the following process steps: preparing a precursor liquid A, wherein the precursor liquid A is Nb ⁵⁺ A solution; preparing precursor liquid B and precursor liquid C, wherein the precursor liquid B is Bi ³⁺ Solution, the precursor solution C is Mg ²⁺ A solution; preparing a BMN film, preparing BMN sol, and then depositing a plurality of layers of BMN films on a substrate by using the BMN sol as a raw material to finally obtain the BMN multi-layer dielectric film material. The preparation method of the BMN dielectric film material 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 microwave dielectric property, and has wide application prospect.

Description

A kind of multilayer BMN dielectric film material and preparation method thereof

technical field

The invention relates to a preparation method of a dielectric thin film material, in particular to a preparation method of a multi-layer BMN dielectric thin film material with low dielectric constant.

Background technique

The rapid development of wireless technology over the past decade has greatly stimulated research into novel dielectric materials suitable for the development of mobile and satellite communications. In the microwave frequency range, these devices used in information and communication technology, their dielectric materials should preferably have large dielectric constant, low dielectric loss, small leakage current and stable resonant frequency temperature coefficient (TCF) , which can meet the requirements of miniaturization and high efficiency. This aspect has also become an inevitable trend of today's scientific development.

The dielectric constant of a dielectric material can vary with the electric field, and based on this, the circuit of the material device can be tuned. Materials with dielectric tunability are mainly divided into ferroelectric dielectric materials and non-ferroelectric dielectric materials. Ferroelectric materials with dielectric tunability are mainly concentrated on BST (Ba _x Sr _1-x TiO ₃ ) ferroelectric thin films with perovskite structure. From the analysis of many researchers' reports, BST thin film materials usually have high Dielectric constant, very fast electric field effect and large dielectric tuning ratio. However, the dielectric loss of this material is high. Scholars have carried out dielectric modification on BST materials by doping and compounding, but the effect is very small, and most of the modifications are at the expense of reducing the dielectric constant of the material. , so the development of new tunable dielectric materials with low loss has become a demand and trend.

In recent years, some nonferroelectric materials with dielectric tunability have been discovered, among which the representative material is BZN (Bi _1.5 ZnNb _1.5 O ₇ ) with a pyrochlore structure. According to the research of scholars, BZN materials have moderate dielectric Electric constant, very low dielectric loss, but its high dielectric tuning rate requires a high bias field, which limits the integrated application of BZN thin film materials. Moreover, Zn in BZN materials is volatile at high temperature, and the stoichiometric ratio is not easy to control. Mg ²⁺ is used to replace Zn ²⁺ in BZN materials, because Mg ²⁺ is more polar than Zn ²⁺ and has a smaller ionic radius, the prepared BMN dielectric material also has a cubic pyrochlore structure, which is a non-ferroelectric Material. The material maintains the characteristics of low dielectric loss of BZN material, has moderate dielectric constant and good temperature stability. Therefore, BMN thin film material is a very valuable new dielectric tunable material, which has great application prospects in the field of communication, especially in varactors.

There are many preparation methods for BMN dielectric thin film materials, mainly including physical deposition method and chemical deposition method. The most widely used physical deposition methods are sputtering, molecular beam epitaxy (MBE), and pulsed laser deposition (PLD). The MBE method has good film formation uniformity, few defects, and is easy to control the stoichiometric ratio. However, the equipment is expensive, the operation is complicated, and it is limited by external conditions (such as crucibles), making it difficult to prepare materials with high melting points and complex compositions. The PLD method has obvious advantages in the preparation of oxide thin films, with fast film formation speed and low cost, but poor film uniformity and many defects, which are not suitable for the preparation of large-area thin film materials. The magnetron sputtering method has a slow growth rate, and different materials have different sputtering rates. The composition of the obtained film and the composition of the target material are different to some extent, and the microstructure and composition uniformity of the film need to be improved. Chemical deposition methods are mainly divided into vapor deposition and solution deposition. The thin film prepared by vapor deposition can precisely control the composition, and the prepared thin film has good uniformity, which can be used for the preparation of large-area thin film. However, the equipment of this method is expensive, and the required precursor is not easy to synthesize and purify. In contrast, the chemical solution deposition method uses simple and inexpensive equipment, and can produce high-quality thin film materials.

Sol-gel method (Sol-Gel) is one of the most commonly used chemical solution deposition methods. The method is to dissolve several metal alkoxides, organic salts or inorganic compounds in the same suitable solvent to form a solution, form a polymer sol through hydrolysis and polymer reaction, and then use pulling, spin coating, brush coating, etc. The method coats the sol on the substrate, and then volatilizes the organic solvent at high temperature and crystallizes the microparticles.

According to relevant research reports, the solution systems of BMN thin film materials prepared by sol-gel method are mainly divided into two types: one is metal alkoxide system; the other is non-alkoxide system. Metal alkoxides are expensive, easily hydrolyzed, and difficult to preserve. During the experiment, the operation of metal alkoxides requires harsh environment and must be carried out in a vacuum glove box with nitrogen or inert gas. Therefore, it is of great significance to use the sol-gel non-alkoxide method to prepare BMN thin film materials. On the one hand, it can reduce the cost and reduce the requirements of experimental equipment, and on the other hand, it can fill the research gap in this field.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a multilayer dielectric film material with low dielectric constant and high quality factor - Bi _1.5 MgNb _1.5 O ₇ and a preparation method thereof. The preparation method of the present invention is a sol-gel method. The process is simple, the process is pollution-free, the production cost is low, the dielectric properties can be significantly improved, and the invention has wide application prospects.

To achieve the above object, the present invention adopts the following technical solutions:

The BMN mentioned in the present invention is the abbreviation of Bi _1.5 MgNb _1.5 O ₇ .

A multilayer BMN dielectric thin film material, the molecular formula of the thin film material is Bi _1.5 MgNb _1.5 O ₇ , the orientation of the thin film material is 222, the grain orientation of the dielectric thin film material is controllable, and can be used to make a dielectric resonator , filters, varactors and other devices, can be used in the field of communications. The invention also discloses a method for preparing the sol-gel non-alkoxide system of the above-mentioned multilayer BMN microwave dielectric film material, which comprises the following steps:

(1) Preparation of Precursor A:

Described precursor liquid A is Nb ⁵⁺ solution;

(2) Preparation of Precursor B and Precursor C:

The precursor solution B is a Bi ³⁺ solution, and the precursor solution C is a Mg ²⁺ solution;

(3) Preparation of BMN film:

The BMN sol is prepared, and then the BMN sol is used as a raw material to deposit a multi-layer BMN film on the substrate, and finally a BMN multi-layer dielectric film material is obtained.

Preferably, the preparation of the precursor solution A in step 1 specifically includes the following steps:

(1) Mix Nb ₂ O ₅ with hydrofluoric acid to obtain NbF ₅ solution, which is for later use;

(2) adding water to dilute the NbF ₅ solution obtained above, and then adjusting the pH of the solution to 6 to obtain a diluted NbF ₅ solution for use;

(3) performing suction filtration on the diluted NbF ₅ solution obtained above to obtain Nb(OH) ₅ precipitation;

(4) The above-mentioned Nb(OH) ₅ precipitation is added to the aqueous citric acid solution to undergo a complexation reaction, that is, the precursor solution A is obtained.

Preferably, the molar ratio of the Nb ₂ O ₅ to hydrofluoric acid is 1:10-13; the molar ratio of the citric acid to Nb ⁵⁺ is 5-7:1; the conditions of the complexation reaction are: The temperature is 60-90°C, and the reaction time is 30-120min.

Preferably, the precursor solution B is a BiCl ₃ solution, the precursor solution C is a MgCl ₂ solution, and the molar ratio of the Nb ₂ O ₅ , BiCl ₃ , and MgCl ₂ is 3-4:6:4.

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

(1) Preparation of BMN sol:

The prepared precursor solution B and the precursor solution C are respectively added to the prepared precursor solution A, and the solution is adjusted to be weakly acidic to obtain a mixed solution, a stabilizer is added to the mixed solution, stirred for reaction, and aged to obtain a BMN sol, which is used for later use. ;

(2) Deposition of multilayer BMN films on the substrate:

The prepared BMN sol is used as a raw material to coat films on different substrates respectively, and then perform annealing heat treatment. BMN multilayer dielectric film material.

Preferably, the pH of the mixed solution is 6.5; the stabilizer is ethylene glycol, and the molar ratio of ethylene glycol and citric acid is 1 to 4:1; the stirring reaction conditions are: the stirring reaction conditions are: 70 to 90° C. In a water bath, stir for 1 to 3 hours; the aging conditions are: room temperature, and the time is 24 to 48 hours.

Preferably, the substrates are ITO and P-type Si substrates; the coating method is spin coating; the specific process conditions for the coating are as follows: the rotational speed during dispensing is 1000-2000 r/min, The rotating speed is 2500-4000 r/min when the glue is spun, the glue-swinging lasts for 30-50 s each time, and the coating amount of the coating is 1-1.5 mL per coating.

Preferably, 1. the annealing temperature is 500～700℃, and the annealing time is 80～120min; the sequence of the repeated coating and annealing heat treatment process is coating film→annealing heat treatment→coating film→annealing heat treatment→... ... coating → annealing heat treatment, repeat the coating film for 5-7 layers, after each annealing heat treatment, cool the obtained film to room temperature and then repeat the coating film and annealing heat treatment process.

beneficial effect

In the present invention, we use Nb ₂ O ₅ as the niobium raw material, use the soluble niobium salt prepared by the citrate method as the niobium source, use magnesium chloride and bismuth chloride as the magnesium source and the bismuth source, and add chelating agents citric acid and ester. BMN sol was prepared by using ethylene glycol as a chemical agent and ammonia water as a pH regulator. The preparation method of the invention has the advantages of low cost, non-toxicity, practicality, safety and the like.

The preparation method of the microwave dielectric thin film material BMN of the present invention is a sol-gel method, the preparation process is simple, the process is pollution-free, the production cost is low, the microwave dielectric performance can be significantly improved, and it has wide application prospects.

The method performs layer-by-layer annealing heat treatment on the prepared film, and each layer of the film is heated evenly, which can further limit the thickness of the BMN multilayer dielectric film and the size of the BMN particles, and the thickness and particle size of the prepared film are controllable, preferred orientation and uniform high. Quality BMN multilayer dielectric films. The grain orientation of the microwave dielectric thin film material prepared by the invention is controllable, can be used to manufacture devices such as dielectric resonators, filters, varactors and the like, and can be applied to the field of communication.

The excellent properties of the multi-layer BMN dielectric film material prepared by the present invention mainly include:

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

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

(3) The BMN dielectric thin film prepared by the experimental method of the present invention is dense and uniform, with uniform particle size, good crystallinity, no cracks on the surface, and no void-like structure.

(4) The grain orientation of the BMN dielectric film prepared by the experimental method of the present invention is controllable and can grow along the (222) orientation, and the BMN film with the (222) orientation is the key to obtain good dielectric properties.

Description of drawings

Fig. 1 is the process flow diagram of BMN sol preparation.

Figure 2 is a process flow diagram of the preparation of the BMN multilayer dielectric film.

FIG. 3 is the XRD patterns of the BMN multilayer dielectric films prepared at different temperatures in the present invention.

4 is a 30,000-fold SEM image of BMN dielectric films with different layers prepared by the present invention (in the figure (a) 3-layer film, (b) 5-layer film, (c) 6-layer film, (d) 7-layer film );

5 is a 50,000-fold SEM image of BMN dielectric films with different layers prepared by the present invention (in the figure (a) 3-layer film, (b) 5-layer film, (c) 6-layer film, (d) 7-layer film ).

Detailed ways

The BMN multilayer dielectric film provided by the present invention and the preparation method thereof will be described in detail below with reference to the examples, and the advantages and characteristics of the present invention will become more clear with the description. Hereinafter, the present invention will be described in detail. Before proceeding with the description, it should be understood that the terms used in this specification and the appended claims should not be construed to be limited to ordinary and dictionary meanings, but should be used in the context of allowing the inventor to properly define the terms for best interpretation On the basis of the principles of the present invention, explanations are made according to meanings and concepts corresponding to the technical aspects of the present invention. Accordingly, the descriptions presented herein are merely preferred examples for illustrative purposes and are not intended to limit the scope of the invention, whereby it is to be understood that other, etc. may be derived therefrom without departing from the spirit and scope of the invention. price or improvement.

The following examples are only listed as examples of the embodiments of the present invention, and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope of the spirit and concept of the present invention are all within the protection of the present invention. scope. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

In the present invention, unless otherwise specified, the raw materials used are conventional commercially available products in the art or prepared by conventional methods in the art.

Example 1

A multilayer BMN dielectric thin film material, the molecular formula of the thin film material is Bi _1.5 MgNb _1.5 O ₇ , the orientation of the thin film material is 222, the grain orientation of the dielectric thin film material is controllable, and can be used to make a dielectric resonator , filters, varactors and other devices, can be used in the field of communications. The preparation method of the sol-gel non-alkoxide system of the above-mentioned multilayer BMN dielectric film material comprises the following steps:

1. Preparation of Precursor A:

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

(1) Select high-purity (99.90%) Nb ₂ O ₅ , add Nb ₂ O ₅ and hydrofluoric acid in a polytetrafluoroethylene container, and react in an oven at 120 ° C for 5 hours to obtain a NbF ₅ solution. The niobium oxide and The molar ratio of hydrofluoric acid is 1:10;

(2) Add water to dilute the NbF ₅ solution obtained above, and adjust the pH of the solution to 6 with saturated aqueous ammonia; then adjust the pH to 9 with a mixed solution of saturated ammonium carbonate and ammonia in a volume ratio of 1:10.

(3) performing suction filtration on the solution obtained in the above step 2 to obtain Nb(OH) ₅ precipitation;

(4) The above-mentioned Nb(OH) ₅ precipitate was added to the citric acid aqueous solution to generate a complexation reaction. Under the condition of a 90 ℃ water bath, heating and stirring for 30 min to complete the dissolution of the precipitate, that is, the precursor solution A—Nb-CA solution was obtained. The molar ratio of the citric acid to the niobium ion is 6:1.

2. Preparation of Precursor B and Precursor C:

_The precursor solution B is a BiCl solution, and the precursor solution C is a _MgCl solution, which specifically includes the following steps:

BiCl ₃ and MgCl ₂ were dissolved in HCl and water, respectively, to obtain precursor solution B and precursor solution C. The molar ratio of Nb ₂ O ₅ , BiCl ₃ , and MgCl ₂ was 3:6:4.

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

(1) Preparation of BMN sol

The prepared precursor solution B and the precursor solution C were respectively slowly added dropwise to the prepared precursor solution A, and the pH value of the solution was adjusted to 6.5 to obtain a mixed solution for use.

In the mixed solution obtained above, ethylene glycol is added as a stabilizer to promote the polymerization of the mixed citrate, and the molar ratio of ethylene glycol and citric acid is 3:1. Then, in an 80° C. water bath, the mixture was stirred for 2 hours to obtain a BMN sol, which was aged for 24 hours. The aging treatment of the invention can remove impurities in the sol, improve the purity of the BMN sol, and help reduce the dielectric loss of the Bi _1.5 MgNb _1.5 O ₇ multilayer dielectric film.

(2) Deposition of multilayer BMN thin films on the substrate

The BMN sol prepared above was used as a raw material, and a spin coater was used to coat the ITO and P-type Si substrates respectively. Set the speed of 1000r/min for dispensing and 3500r/min for ejection during film coating. Each ejection lasts for 50s. The obtained film was annealed at an annealing temperature of 500°C for 120 minutes, and then the film was cooled to room temperature, and the film coating operation was repeated: coating - annealing heat treatment - coating - annealing heat treatment - ...... coating - annealing heat treatment. Repeat 5 coats of coating. After final stabilization, a film of a certain thickness is formed on the substrate.

Example 2

A multilayer BMN dielectric thin film material, the molecular formula of the thin film material is Bi _1.5 MgNb _1.5 O ₇ , the orientation of the thin film material is 222, the grain orientation of the microwave dielectric thin film material is controllable, and can be used for making dielectric resonance devices, filters, varactors, etc., can be used in the field of communications. The preparation method of the sol-gel non-alkoxide system of the above-mentioned multilayer BMN dielectric film material comprises the following steps:

1. Preparation of Precursor A:

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

(1) Select high-purity (99.90%) Nb ₂ O ₅ , add Nb ₂ O ₅ and hydrofluoric acid in a polytetrafluoroethylene container, and react in an oven at 120 ° C for 5 hours to obtain a NbF ₅ solution. The niobium oxide and The molar ratio of hydrofluoric acid is 1:13;

(2) Add water to dilute the NbF ₅ solution obtained above, and adjust the pH of the solution to 6 with saturated ammonia; then use a mixed solution of saturated ammonium carbonate and ammonia in a volume ratio of 1:5, and adjust the pH to 9.

(3) performing suction filtration on the solution obtained in the above step 2 to obtain Nb(OH) ₅ precipitation;

(4) The above-mentioned Nb(OH) ₅ precipitate is added to the aqueous citric acid solution to generate a complexation reaction, and the molar ratio of citric acid and niobium ion is 7:1; under the condition of a 60 ℃ water bath, heat and stir for 120 min until the precipitate dissolves completely, that is, obtain Precursor A—Nb-CA solution.

2. Preparation of Precursor B and Precursor C:

_The precursor solution B is a BiCl solution, and the precursor solution C is a _MgCl solution, which specifically includes the following steps:

BiCl ₃ and MgCl ₂ were dissolved in HCl and water, respectively, to obtain precursor solution B and precursor solution C. The molar ratio of Nb ₂ O ₅ , BiCl ₃ , and MgCl ₂ was 4:6:4.

2. The preparation of BMN film specifically includes the following steps:

(2) Preparation of BMN sol

The prepared precursor solution B and the precursor solution C were respectively slowly added dropwise to the prepared precursor solution A, and the pH value of the solution was adjusted to 6.5 to obtain a mixed solution for use.

In the mixed solution obtained above, ethylene glycol is added as a stabilizer to promote the polymerization of the mixed citrate, and the molar ratio of ethylene glycol and citric acid is 4:1. Then, in a 90° C. water bath, the solution was stirred for 1 hour to obtain a BMN sol, which was aged for 48 hours. The aging treatment of the invention can remove impurities in the sol, improve the purity of the BMN sol, and help reduce the dielectric loss of the Bi _1.5 MgNb _1.5 O ₇ multilayer dielectric film.

(2) Deposition of multilayer BMN thin films on the substrate

The BMN sol prepared above was used as a raw material, and a spin coater was used to coat the ITO and P-type Si substrates respectively. Set the speed of 2000r/min for dispensing and 4000r/min for ejection, and each ejection lasts for 40s. The obtained film was annealed at an annealing temperature of 700°C for 80 minutes, and then the film was cooled to room temperature, and the film coating operation was repeated: coating - annealing heat treatment - coating - annealing heat treatment - ...... coating - annealing heat treatment. Repeat coating for 6 coats. After final stabilization, a film of a certain thickness is formed on the substrate.

Example 3

A multilayer BMN dielectric thin film material, the molecular formula of the thin film material is Bi _1.5 MgNb _1.5 O ₇ , the orientation of the thin film material is 222, the grain orientation of the dielectric thin film material is controllable, and can be used to make a dielectric resonator , filters, varactors and other devices, can be used in the field of communications. The preparation method of the sol-gel non-alkoxide system of the above-mentioned multilayer BMN dielectric film material comprises the following steps:

1. Preparation of Precursor A:

Specifically include the following steps:

(1) Select high-purity (99.90%) Nb ₂ O ₅ , add Nb ₂ O ₅ and hydrofluoric acid in a polytetrafluoroethylene container, and react in an oven at 120 ° C for 5 hours to obtain a NbF ₅ solution. The niobium oxide and The molar ratio of hydrofluoric acid is 1:11;

(2) Add water to dilute the NbF ₅ solution obtained above, and adjust the pH of the solution to 6 with saturated aqueous ammonia;

(3) performing suction filtration on the solution obtained in the above step 2 to obtain Nb(OH) ₅ precipitation;

(4) The above-mentioned Nb(OH) ₅ precipitate is added to the citric acid aqueous solution for complexation reaction, and the molar ratio of citric acid and niobium ion is 5:1; under the condition of 80 ℃ water bath, heat and stir for 100 min until the precipitate dissolves completely, that is, obtain Precursor A—Nb-CA solution.

2. Preparation of Precursor B and Precursor C:

_The precursor solution B is a BiCl solution, and the precursor solution C is a _MgCl solution, which specifically includes the following steps:

BiCl ₃ and MgCl ₂ were dissolved in HCl and water, respectively, to obtain precursor solution B and precursor solution C. The molar ratio of Nb ₂ O ₅ , BiCl ₃ , and MgCl ₂ was 3:6:4.

2. The preparation of BMN film specifically includes the following steps:

(3) Preparation of BMN sol

The prepared precursor solution B and the precursor solution C were respectively slowly added dropwise to the prepared precursor solution A, and the pH value of the solution was adjusted to 6.5 to obtain a mixed solution for use.

In the mixed solution obtained above, ethylene glycol is added as a stabilizer to promote the polymerization of the mixed citrate, and the molar ratio of ethylene glycol and citric acid is 1:1. Then, in a 70° C. water bath, the mixture was stirred for 3 hours to obtain a BMN sol, which was aged for 24 hours. The aging treatment of the invention can remove impurities in the sol, improve the purity of the BMN sol, and help reduce the dielectric loss of the Bi _1.5 MgNb _1.5 O ₇ multilayer dielectric film.

(2) Deposition of multilayer BMN thin films on the substrate

The BMN sol prepared above was used as a raw material, and a spin coater was used to coat the ITO and P-type Si substrates respectively. Set the speed of 1500r/min for dispensing and 3000r/min for ejection during film coating, and each ejection lasts for 30s. The obtained film was annealed at an annealing temperature of 600°C for 100 minutes, and then the film was cooled to room temperature, and the film coating operation was repeated: coating - annealing heat treatment - coating - annealing heat treatment - ...... coating - annealing heat treatment. Repeat the coating for 7 layers. After final stabilization, a film of a certain thickness is formed on the substrate.

Experimental example

In order to prove the excellent performance of the BMN multilayer dielectric film of the present invention, the performance of the BMN multilayer dielectric film prepared by the present invention was tested. FIG. 3 is the XRD pattern of the BMN multilayer dielectric film prepared by the present invention at different annealing temperatures. In the thin film preparation process, the thin film growth temperature is a very important factor, which has a great influence on the crystallinity and composition of the thin film. It can be seen from Fig. 3 that (at 500 °C annealing temperature, the BMN multilayer microwave dielectric film is oriented along the (400) direction, and the (222) diffraction peak is weak; at 600 °C annealing temperature, the (222) peak is enhanced, ( 400) peak weakens; with the increase of temperature, when the temperature reaches 700 °C, the BMN film grows significantly along the (222) direction, and the (400) diffraction peak weakens significantly, while the BMN film with (222) orientation is good. key to dielectric properties.

Figures 4 and 5 are the SEM images of the BMN multilayer dielectric films prepared by the present invention. It can be seen from Figures 4 and 5 (under the condition of It is also larger. When the number of film layers is 3 layers, the film has obvious delamination, which means that the growth distribution of the film is not uniform and the quality is not ideal. After comparing layers 5, 6, and 7, it is found that: compared with the 5-layer film, in the film When the number of layers is 6, the film crystallizes well, and there is no crack, and the quality of the film is ideal. However, when the number of layers is 7, it can be seen that due to excessive growth, larger particles appear, and the size between the grains The size is also uneven, and small cracks start to appear in the film, and the appearance of cracks will inevitably affect the performance of the dielectric film).

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art can still The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed in the present invention.

Claims (2)

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 _1.5 MgNb _1.5 O ₇ The preparation method comprises the following steps:

(1) the preparation of the precursor liquid A specifically comprises the following steps:

mixing Nb with ₂ O ₅ Mixing with hydrofluoric acid to obtain NbF ₅ Solution for later use;

the NbF obtained above was diluted with water ₅ A solution, the pH of which is adjusted with saturated ammonia = 6; then, regulating the pH to 9 by using a mixed solution of saturated ammonium carbonate and ammonia water to obtain a diluted solution for later use;

the diluted solution obtained above was filtered under suction to obtain Nb (OH) ₅ Precipitating;

nb (OH) ₅ Adding the precipitate into citric acid aqueous solution to carry out complexation reaction to obtain precursor solution A;

the Nb ₂ O ₅ The molar ratio of the hydrofluoric acid to the hydrofluoric acid is 1: 10-13; the citric acid and Nb ⁵⁺ 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;

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

the precursor liquid B is BiCl ₃ The precursor solution C is MgCl ₂ A solution;

(3) the preparation method of the BMN film comprises the following steps:

preparation of BMN sol: respectively adding the prepared precursor liquid B and the prepared precursor liquid C into the prepared precursor liquid A, adjusting the solution to be weakly acidic to obtain a mixed solution, wherein the pH of the mixed solution is 6.5, adding ethylene glycol into the mixed solution, carrying out stirring reaction for 1-3 hours in a water bath at 70-90 ℃, and aging for 24-48 hours at room temperature to obtain BMN sol for later use;

the Nb ₂ O ₅ 、BiCl ₃ 、MgCl ₂ The molar ratio of (a) to (b) is 3-4: 6: 4; the molar ratio of the ethylene glycol to the citric acid is 1-4: 1;

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 on the substrates, cooling the substrates to generate a film on the substrates, then repeating the processes of coating and annealing heat treatment, and depositing a plurality of layers of BMN films on the substrates to finally obtain a plurality of layers of BMN dielectric film materials;

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;

the annealing temperature is 700 ℃, and the annealing time is 80-120 min; the sequence of the repeated coating and annealing heat treatment processes is sequentially coating → annealing heat treatment →.... multidot.;

the orientation of the multilayer BMN dielectric thin film material is 222.

2. A multilayer BMN dielectric thin film material, prepared by the method of claim 1.

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