Preparation method of barium titanate nano powder
阅读说明：本技术 一种钛酸钡纳米粉体制备方法 (Preparation method of barium titanate nano powder ) 是由 潘鹏飞 于淑会 孙蓉 于 2020-02-24 设计创作，主要内容包括：本发明提供一种钛酸钡纳米粉体及其制备方法和用途,具体公开了以下制备方法：1)液相反应：制备二氧化钛与第一钡源的混合水溶液,在70～120℃下常压反应,干燥后获得壳核结构的二氧化钛浆料；2)固相反应：混合壳核结构的二氧化钛浆料以及第二钡源,并通过煅烧获得钛酸钡纳米粉体；步骤1)中二氧化钛与第一钡源的摩尔比为1:x；步骤2)中第二钡源的物质的量为1-x；所述第一钡源为氢氧化钡、硝酸钡、氯化钡中一种或多种的组合；所述第二钡源为碳酸钡、氧化钡、氢氧化钡中一种或多种的组合。该制备方法不产生废气液、安全性高、设备要求低、操作简单。(The invention provides barium titanate nano powder and a preparation method and application thereof, and particularly discloses the following preparation method: 1) liquid-phase reaction: preparing a mixed aqueous solution of titanium dioxide and a first barium source, reacting at 70-120 ℃ under normal pressure, and drying to obtain titanium dioxide slurry with a shell-core structure; 2) solid-phase reaction: mixing the titanium dioxide slurry with the shell-core structure and a second barium source, and calcining to obtain barium titanate nano powder; the molar ratio of the titanium dioxide to the first barium source in the step 1) is 1: x; the amount of the second barium source substance in the step 2) is 1-x; the first barium source is one or a combination of more of barium hydroxide, barium nitrate and barium chloride; the second barium source is one or a combination of more of barium carbonate, barium oxide and barium hydroxide. The preparation method does not generate waste gas liquid, has high safety, low equipment requirement and simple operation.)
1. A method for preparing barium titanate nano powder is characterized by comprising the following steps: comprises the following steps
1) Liquid-phase reaction: preparing a mixed aqueous solution of titanium dioxide and a first barium source, reacting at 70-120 ℃ under normal pressure, and drying to obtain titanium dioxide slurry with a shell-core structure;
2) solid-phase reaction: mixing the titanium dioxide slurry with the shell-core structure and a second barium source, and calcining to obtain barium titanate nano powder;
in the step 1), the molar ratio of titanium dioxide to the first barium source is 1: x, wherein x is 0.1-0.9;
the amount of the second barium source substance in the step 2) is 1-x;
the first barium source is one or a combination of more of barium hydroxide, barium nitrate and barium chloride;
the second barium source is one or a combination of more of barium carbonate, barium oxide and barium hydroxide.
2. The method according to claim 1, wherein the sintering temperature is 750 to 1050 ℃, preferably 800 to 900 ℃.
3. The method according to claim 1, wherein the reaction of step 1) is carried out under an inert atmosphere.
4. The method according to claim 1, wherein x is 0.1 to 0.5.
5. The method of claim 1, wherein the sintering is performed in a thin uniform layer, preferably with a mass per unit area of less than 1g/cm2。
6. The preparation method according to claim 1, wherein the upper temperature rise rate is 5-30 ℃/min, and the heat preservation time is 1.5-4 h.
7. The production method according to claim 1, wherein the mass fraction of the solute in the mixed solution of titanium dioxide and the first barium source is 15% to 50%.
8. A barium titanate nano powder, characterized by being prepared by the preparation method of any one of claims 1 to 7, and having an average particle size of 60 to 150nm, preferably 80 to 150 nm.
9. The barium titanate nano powder is characterized by being prepared by the preparation method of any one of claims 1 to 7, wherein the c/a ratio of the lattice parameter is 1.0045-1.01, and preferably the c/a ratio of the lattice parameter is 1.007-1.01.
10. Use of the barium titanate nanopowder of any of claims 8 to 9 as a dielectric material.
Technical Field
The invention belongs to the field of material chemistry, and particularly relates to a preparation method of barium titanate nano powder.
Background
Barium titanate (BaTiO)3) Has been widely used as a dielectric for various types of multilayer ceramic capacitors (MLCCs) due to a relatively high dielectric constant at room temperature and a relatively low dielectric loss at room temperature. In order to realize high circuit integration, passive devices such as multilayer ceramic capacitors have been gradually miniaturized. This trend must be addressedIt is required to increase the number of dielectric layers in a multilayer ceramic capacitor in a limited volume and to reduce the thickness of each layer. Thus, BaTiO with submicron or even nanometer particle size is prepared3Powder is of great importance.
Currently, commercial BaTiO3The powder is mainly prepared by a solid phase method, a hydrothermal method and a coprecipitation method. Wherein, the solid phase method is generally to mix the oxide or acid salt and hydroxide containing barium ion and titanium ion uniformly and sinter at 1000-1200 ℃, and BaTiO is generated by the interface reaction between different phase crystal grains3And (3) powder. Although the solid phase method has simple preparation process, the prepared powder has serious agglomeration phenomenon and relatively large particle size. The hydrothermal method generally uses water as a solvent, an organic compound such as tetrabutyl titanate as a titanium source, and barium hydroxide (Ba (OH)2) As a barium source, the nano BaTiO is generated by long-time (1-48 h) reaction in a high-temperature (80-450 ℃) and high-pressure environment3And (4) precipitating. In order to increase the extent of the reaction, an excess of barium source is usually added, thereby bringing about a large amount of heavy metal waste liquid. The coprecipitation method comprises adding precipitant into aqueous solution of metal salts of titanium and barium to obtain barium titanyl oxalate precipitate, filtering, drying and sintering to obtain BaTiO3And (3) powder. Similar to the hydrothermal method, a large amount of heavy metal waste liquid is also generated in the process of preparing the barium titanium oxyoxalate precipitate, and meanwhile, the agglomeration of part of powder is induced in the sintering process, so that the particle size distribution of the powder is influenced. Therefore, in consideration of increasingly strict environmental requirements and requirements of miniaturization of MLCC devices on powder dielectricity and particle size, a BaTiO with uniform particle size, high crystallinity, good dispersibility and series c/a ratio based on a zero-pollution emission solid phase method is urgently needed to be designed3A method for preparing nano powder.
Further, BaTiO3The traditional solid phase reaction usually requires the sintering temperature to be 1000-1200 ℃. However, titanium dioxide (TiO)2) Phase transformation generally occurs within 650 c to 950 c with a significant increase in grain size. In the sintering process, if the grain shell layer has relatively low crystallinity, the shell layer can absorb heat energy to improve the crystallinity, and simultaneously reduce the heat energy transferred to the crystal nucleus to limit the growth of the crystal nucleus. Thus, it can be seen that in TiO2BaTiO with relatively low crystallinity coated outside crystal grains3The shell layer is taken as one of the precursor powder for the solid phase reaction, and the grain size of the crystal grain in the phase change process can be effectively limited, thereby further reducing the BaTiO3The particle size of the powder.
Disclosure of Invention
To solve the above-mentioned commercial BaTiO3The invention provides a BaTiO powder, which has the problems in the powder preparation method3A method for preparing nano powder. Firstly, TiO with a shell-core structure is generated based on a normal pressure liquid phase method2Intermediate powder, and then BaTiO with high crystallinity, uniform grain diameter, good dispersibility and series c/a ratio is generated by a solid phase method3And (3) nano powder. In the preparation method, the ratio of the first barium source to the second barium source in the liquid phase reaction stage and the solid phase reaction stage is changed, so that the BaTiO can be further reduced3The grain diameter of the nano powder and the c/a ratio of the crystal lattice parameter are regulated and controlled.
In order to achieve the purpose, the invention adopts the following technical scheme:
one aspect of the invention provides a BaTiO3The preparation method of the nano powder comprises the following steps:
1) liquid-phase reaction: preparation of TiO2Reacting with the mixed aqueous solution of the first barium source at the temperature of 70-120 ℃ under normal pressure, and drying to obtain the TiO with the shell-core structure2Sizing agent;
2) solid-phase reaction: mixed shell-core structure TiO2A second barium source and BaTiO obtained by calcination3Nano powder;
TiO in step 1)2The molar ratio of the barium source to the first barium source is 1: x, wherein x is 0.1-0.9, and preferably x is 0.1-0.5;
the amount of the second barium source substance in the step 2) is 1-x;
the first barium source is barium hydroxide (Ba (OH)2) Barium nitrate (Ba (NO)3)2) Barium chloride (BaCl)2) A combination of one or more of the foregoing;
the second barium source is barium carbonate (BaCO)3) Barium oxide (BaO), barium hydroxide (Ba (OH)2) One or more ofCombinations of (a) and (b).
In the technical scheme of the invention, x is 0.1, 0.2, 0.3, 0.4, 0.5 or any value in the period.
In the technical scheme of the invention, the reaction in the step 1) is carried out under the protection of inert atmosphere.
In the technical scheme of the invention, the titanium dioxide slurry with the shell-core structure comprises BaTiO shell3The inner core is TiO2A slurry of particles.
In the technical scheme of the invention, the normal-pressure reaction time in the step 1) is 3-5 hours.
In the technical scheme of the invention, the step of ball milling the mixture is also included after the mixing in the step 2).
Further, the inert gas atmosphere is selected from inert gas atmospheres such as nitrogen and argon.
Further, in the liquid phase reaction stage, TiO is prepared2The mixed aqueous solution with the first barium source can be TiO2Adding the aqueous dispersion into the first barium source aqueous solution, or adding the first barium source aqueous solution into TiO2In the aqueous dispersion, TiO may be added2The aqueous dispersion and the first barium source aqueous solution are mixed in parallel flow, even TiO can be used2The powder is added directly to the first aqueous barium source solution.
Further, in the liquid phase reaction stage, TiO2The mass fraction of solute in the mixed solution with the first barium source is 15-50%.
Further, the molar ratio of total barium ions to total titanium ions in the mixed powder participating in the solid-phase reaction is controlled to be 1:1, and the addition amount of the second barium source is determined according to the amount of the substance of the first barium source participating in the liquid-phase reaction.
In the technical scheme of the invention, the sintering temperature is 750-1050 ℃, and preferably 800-900 ℃.
In the technical scheme of the invention, the sintering mode is a uniform thin layer, and preferably, the mass per unit area is less than 1g/cm during sintering2Preferably less than 0.5g/cm2More preferably 0.1 to 0.3g/cm2。
According to the technical scheme, during sintering, the upper heating rate is 5-30 ℃/min, and the heat preservation time is 1.5-4 h.
In the technical solution of the present invention, no pH adjustment is performed in step 1).
Further, BaTiO prepared by the above procedure3The nano powder has an average particle size of 60-150 nm, a lattice parameter c/a ratio of 1.0045-1.01, a purity of more than 99.9%, and a specific surface area of more than 10m2(ii)/g, particle size distribution (D50) less than 4 μm.
Preferably, BaTiO3The nano powder has an average particle size of 80-150 nm, a lattice parameter c/a ratio of 1.007-1.01, a purity of more than 99.9%, and a specific surface area of more than 10m2(ii)/g, particle size distribution (D50) less than 4 μm.
Another aspect of the present invention provides BaTiO obtained based on the above-mentioned preparation method3And (3) nano powder.
In another aspect of the present invention, there is provided the BaTiO of the present invention3The nano powder is used as a dielectric material.
Barium titanate and BaTiO in the present invention3And the same may be substituted for each other.
Advantageous effects
The invention firstly obtains TiO with a shell-core structure by a liquid phase method2And obtaining the barium titanate nano powder by a solid phase method. The preparation method does not generate waste gas liquid, has high safety, low equipment requirement and simple operation. Under the condition of controlling the molar ratio of barium ions to titanium ions in the whole system to be 1:1, the BaTiO can be further reduced by regulating and controlling the proportion of the first barium source to the second barium source in the liquid phase reaction stage and the solid phase reaction stage3The grain diameter of the nano powder and the c/a ratio of the lattice parameter are optimized. Thus, the preparation method is significantly superior to the existing BaTiO for commercial use3A solid phase method, a hydrothermal method and a co-precipitation method for powder production.
Drawings
The above and other aspects, features and advantages of embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
FIG. 1 Synthesis of BaTiO according to example 23X-ray diffraction (XRD) pattern of the nanopowder.
FIG. 2 Synthesis of BaTiO according to example 33X-ray diffraction (XRD) pattern of the nanopowder.
FIG. 3 Synthesis of BaTiO according to example 43X-ray diffraction (XRD) pattern of the nanopowder.
FIG. 4 Synthesis of BaTiO according to example 53X-ray diffraction (XRD) pattern of the nanopowder.
FIG. 5 Synthesis of BaTiO according to comparative example 13X-ray diffraction (XRD) pattern of the nanopowder.
FIG. 6 Synthesis of BaTiO according to comparative example 23X-ray diffraction (XRD) pattern of the nanopowder.
FIG. 7 Synthesis of BaTiO according to example 23Scanning Electron Microscope (SEM) photograph of the nanopowder.
FIG. 8 Synthesis of BaTiO according to example 33Scanning Electron Microscope (SEM) photograph of the nanopowder.
FIG. 9 Synthesis of BaTiO according to example 43Scanning Electron Microscope (SEM) photograph of the nanopowder.
FIG. 10 Synthesis of BaTiO according to example 53Scanning Electron Microscope (SEM) photograph of the nanopowder.
FIG. 11 Synthesis of BaTiO according to comparative example 13Scanning Electron Microscope (SEM) photograph of the nanopowder.
FIG. 12 Synthesis of BaTiO according to comparative example 23Scanning Electron Microscope (SEM) photograph of the nanopowder.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. Those skilled in the art may make similar modifications without departing from the spirit of the invention, and therefore the invention is not limited to the specific embodiments disclosed below.
Considering the existing commercial BaTiO3In the process of powder productionThe invention provides a BaTiO powder which has the problems of large heavy metal waste liquid generation, relatively large particle size of product powder and the like3A method for preparing nano powder. Has the following advantages: 1) the preparation method does not generate waste gas and liquid in the whole process, and realizes BaTiO3The nano powder is prepared in an environment-friendly way. 2) Based on TiO having a core-shell structure2The intermediate powder can limit the growth of crystal grains in the solid phase reaction stage and further reduce BaTiO3The particle size of the nano powder. 3) Under the condition of controlling the molar ratio of barium ions to titanium ions in the whole system to be 1:1, the BaTiO can be further reduced by optimizing the proportion of the first barium source to the second barium source in the liquid phase reaction stage and the solid phase reaction stage3The grain diameter of the nano powder and the c/a ratio of the lattice parameter are regulated and controlled.
The preparation method comprises two stages of liquid phase reaction and solid phase reaction, specifically,
the first is the liquid phase reaction stage: under the protection of inert atmosphere, certain amount of TiO2And mixing the aqueous dispersion with the first barium source aqueous solution, and carrying out normal-pressure liquid-phase reaction on the mixed system at the temperature of 70-120 ℃ for 3-5 hours. Drying part of the reaction solution to obtain TiO with a shell-core structure2And (3) slurry.
Then a solid phase reaction stage: the TiO with the shell-core structure2Mixing and ball-milling the slurry and a certain amount of second barium source powder, drying the ball-milled slurry to obtain mixed powder, and calcining the mixed powder by rapid heating to obtain BaTiO3And (3) nano powder.
The first barium source is barium hydroxide (Ba (OH)2) Barium nitrate (Ba (NO)3)2) Barium chloride (BaCl)2) A combination of one or more of the foregoing;
the second barium source is barium carbonate (BaCO)3) Barium oxide (BaO), barium hydroxide (Ba (OH)2) One or more of the above.
Preferably, in the liquid phase reaction stage, the normal pressure liquid phase reaction can be performed under the atmosphere, and can also be performed under the protection of an inert atmosphere, such as nitrogen, argon, and the like.
The liquid phase reaction under normal pressure generally requiresMatching with a condensation reflux device. If the reaction is carried out in an atmospheric environment, a trace amount of barium source may react with carbon dioxide in the air to generate BaCO3. Since a certain amount of barium source (second barium source) powder still needs to be added in the subsequent solid phase reaction stage, trace BaCO is introduced in the liquid phase reaction3Without affecting the purity of the final product. The liquid phase reaction may be carried out in an atmospheric environment in consideration of further reduction of production cost.
Preferably, in the liquid phase reaction stage, the first barium source is reacted with TiO2The molar ratio of (A) to (B) is 0.10 to 0.50.
The liquid phase reaction is designed to prepare intermediate powder with a shell-core structure, wherein the shell layer is BaTiO3The inner core is anatase phase TiO2. Because of BaTiO obtained by the liquid phase method3The crystallinity of the shell layer is less than that of TiO2Core, so that during sintering in the solid phase reaction, BaTiO3The shell layer absorbs heat energy, improves the crystallinity and reduces the transmission to TiO2The heat energy of the inner core, thereby limiting the grain size increase. Furthermore, if the TiO prepared by the first liquid phase reaction is considered to involve interpenetration of titanium ions and barium ions at the grain boundary of different phases in the second solid phase reaction process2The shell layer of the intermediate powder is too thick, which may affect the interdiffusion speed of titanium ions and barium ions in the sintering process. Thereby, in the liquid phase reaction stage, the first barium source and the TiO are controlled2The molar ratio of (A) to (B) is 0.01 to 0.99. According to the experimental results, the first barium source and the TiO are controlled2The molar ratio of (A) to (B) can obtain high-performance barium titanate nano powder with the average particle size of 60-150 nm, the lattice parameter c/a ratio of 1.0022-1.01 and the like. Considering that the preparation of devices such as MLCC and the like requires that the powder has better dispersibility, higher c/a ratio and series particle size (80-150 nm), the first barium source and TiO are further controlled2The molar ratio of (A) to (B) is 0.10 to 0.50.
Preferably, in the liquid phase reaction stage, the TiO2Mixing the aqueous dispersion with the first barium source aqueous solution, optionally TiO2Adding the aqueous dispersion to the first barium source aqueous solution, optionally adding the first bariumAddition of Source aqueous solution to TiO2In the aqueous dispersion, TiO may be added2The aqueous dispersion may be combined with the first aqueous barium source solution concurrently, or even the TiO may be combined2The powder is added directly to the first aqueous barium source solution.
TiO precursor powder2The anatase phase TiO with relatively large particle size (0.2-0.4 μm) can be selected2The powder is treated by high-energy ball milling for 6 to 24 hours before use, or anatase phase hydrophilic TiO with relatively small particle size (30 to 150nm) is directly used2And (3) powder. Due to TiO2The nano powder can be well dispersed in the deionized water, so that the TiO2The barium sulfate and the barium sulfate can be uniformly distributed in the aqueous solution by mixing the barium sulfate and the barium sulfate with the first barium source aqueous solution in the form of aqueous dispersion or nano powder. For TiO of the invention2Nano powder or TiO2The source of the aqueous dispersion is not limited and may be commercially available or prepared by itself.
Preferably, in the liquid phase reaction stage, the TiO2The mass fraction of solute in the mixed solution with the first barium source is 15-50%.
Reasonable control of solution concentration (15-50%) helps to avoid precursor powder (TiO)2Nanoparticles) and products (TiO with core-shell structure)2Nanoparticles) to promote agglomeration of TiO2Surface BaTiO3Growth of shell layer to improve BaTiO3The coating effect of the shell layer is improved, and the TiO with the shell-core structure is improved2Dispersibility of the intermediate product.
Preferably, in the liquid phase reaction stage, the first barium source is Ba (OH)2、Ba(NO3)2、BaCl2In the liquid phase reaction, the total amount of species of the Ba source participating in the liquid phase reaction is constant.
TiO2Crystalline BaTiO3The shell layer is from Ba ions and TiO in the solution2Chemical reaction between Ti ions on the surface of crystal grains. Thus, BaTiO3Formation and growth of shell, i.e. BaTiO3The thickness of the shell layer is regulated and controlled, and is partially dependent on the concentration of Ba ions in the solution. In order to better react in the TiO phase by liquid phase reaction2Surface coated with BaTiO3Shell layer provided with only Ba solution of ions, preferably Ba (OH)2、Ba(NO3)2、BaCl2Any one or a combination of more of them as a Ba source to participate in the liquid phase reaction. Since 1 mole of barium ions are contained in 1 mole of the above barium sources, the total amount of the barium sources added in the liquid phase reaction stage is not changed regardless of the selected barium source.
Preferably, the molar ratio of total barium ions to total titanium ions in the mixed powder participating in the solid-phase reaction is controlled to be 1:1, and the addition amount of the second barium source is determined according to the amount of the substance of the first barium source participating in the liquid-phase reaction.
In the invention, only partial water is dried in a solution system subjected to liquid phase reaction, then the reaction system is directly transferred to a ball milling tank, and a second barium source and ball milling beads are added for ball milling and drying to obtain the solid phase reaction precursor mixed powder. Therefore, the preparation method can accurately control the Ba ion content of the system, namely the Ba ion content comes from the first barium source participating in the liquid phase reaction and the second barium source participating in the solid phase reaction, and heavy metal waste liquid is avoided.
To ensure that the final product is BaTiO3The molar ratio of total barium ions to total titanium ions in the mixed powder participating in the solid-phase reaction needs to be controlled to be 1:1, that is, the sum of the amount of the first barium-source substance participating in the liquid-phase reaction and the amount of the second barium-source substance participating in the solid-phase reaction and TiO2The amount of material was consistent. Thus, the amount of the second barium source to be added can be determined according to the amount of the first barium source to be involved in the liquid phase reaction.
Preferably, in the solid phase reaction stage, the second barium source is BaCO3、BaO、Ba(OH)2In the presence of one or more of the above, the amount of the total species of the Ba source participating in the solid-phase reaction is not changed.
The solid phase reaction is essentially the breaking and recombination of different ionic bonds at the grain interfaces of different phases. In order to make the Ba source and the Ti source diffuse better with each other, further promote the growth of tetragonal lattice structure of barium titanate, and avoid the introduction of impurity ions other than Ba and Ti ions, it is preferable that the melting point is relatively low (lower than that of TiO)2Melting point) of BaCO3、BaO、Ba(OH)2Participate in solid phase reaction. BySince 1 mole of barium ions are contained in 1 mole of the above barium source, the amount of the barium source added in the solid phase reaction stage is not changed regardless of the selected barium source.
Preferably, in the solid phase reaction stage, the ball-milled mixed powder is sintered in a uniform thin layer mode, and the mass per unit area during sintering is less than 1g/cm2The heating rate is 5-30 ℃/min, the sintering temperature is 750-950 ℃, and the heat preservation time is 1.5-4 h.
In the solid phase reaction, the volume and purity of the crystal grains are determined by the chemical reaction at the grain boundary and the degree of interdiffusion of ions. To produce BaTiO of high purity3The nanometer powder can improve the chemical reaction degree at the grain boundary at a faster temperature rising rate and limit the excessive growth of grains by controlling the sintering time. In addition, the powder is paved and sintered in a uniform thin layer mode, so that the uniform distribution of the temperature of the inner layer and the outer layer of the powder is facilitated, and the uniform distribution of the grain size of the product is realized. Therefore, in order to guarantee powder performance, reduce equipment requirements, enhance production safety and improve powder production efficiency, the heating rate is generally set to be 5-30 ℃/min, the sintering temperature is set to be 750-1050 ℃, and the heat preservation time is set to be 2 hours.
BaTiO prepared by the above procedure3The powder can realize the average grain diameter of 60-150 nm, the lattice parameter c/a ratio of 1.0045-1.01, the purity of more than 99.9 percent and the specific surface area of more than 10m2(ii)/g, particle size distribution (D50) less than 4 μm.
Example 1
At room temperature, 0.08moL of nano TiO2The powder is evenly dispersed in 15mL deionized water and is slowly and evenly stirred to prepare TiO2An aqueous dispersion.
Under the protection of nitrogen at normal pressure, 0.008moL of Ba (OH)2Adding into a three-neck round-bottom flask together with 25mL of deionized water, stirring at 100 ℃ and carrying out condensation reflux until Ba (OH)2And completely dissolving.
Adding TiO into the mixture2The aqueous dispersion was poured into the three-necked flask, and the temperature of the mixed solution was maintained at 100 ℃ and stirring was continued for 4 hours. After the reaction is finished, drying part of the reaction solution to obtain the TiO with the shell-core structure2And (3) slurry.
Mixing the above TiO with shell-core structure2Slurry and 0.072moL BaCO3Mixing the powder, and grinding and dispersing the powder with high efficiency.
Mixing the above mixture at a ratio of 0.2g/cm2The mass per unit area is spread in a muffle furnace and calcined for 2 hours at 850 ℃ according to the heating rate of 20 ℃/min to obtain BaTiO3And (3) nano powder.
Example 2
Example 2 the other procedures were in accordance with example 1, with only the amount of barium-derived material being varied, including Ba (OH)2Is 0.01moL of BaCO30.07moL of BaTiO was obtained3And (3) nano powder.
Example 3
Example 3 the other procedures were in accordance with example 1, with only the amount of barium-derived material being varied, including Ba (OH)20.02moL of BaCO30.06moL to give BaTiO3And (3) nano powder.
Example 4
Example 4 the other procedures were as in example 1 except that the amount of barium-derived material, including Ba (OH)20.04moL of BaCO30.04moL, BaTiO was obtained3And (3) nano powder.
Example 5
Example 5 the other procedures were identical to those of example 1, except that the amount of barium-derived material, including Ba (OH)20.06moL of BaCO30.02moL to obtain BaTiO3And (3) nano powder.
Example 6
Example 6 the other procedures were identical to those of example 1, except that the amount of barium-derived material, including Ba (OH)2Is 0.072moL, BaCO30.008 moL% to obtain BaTiO3And (3) nano powder.
The reaction conditions in examples 1 to 6 are shown in Table 1, and BaTiO synthesized3The performance parameters of the nanopowder are shown in Table 2, and the synthesized part of BaTiO3The XRD pattern of the nano powder is shown in figures 1-4, and the SEM picture is shown in figures 7-10.
In order to prove that the preparation method of the nano powder provided by the invention is superior to the traditional solid phase method or liquid phase method in the aspects of particle size control and lattice parameter regulation, the same experimental parameters are selected, and the design comparative examples 1 and 2 are prepared by the solid phase method and the liquid phase method.
Comparative example 1
Adding 0.08moL of TiO2Mixing the powder with 0.08moL of BaCO3Mixing the powder, and grinding and dispersing the powder with high efficiency.
Mixing the above mixture at a ratio of 0.2g/cm2The mass per unit area is spread in a muffle furnace and calcined for 2 hours at 850 ℃ according to the heating rate of 20 ℃/min to obtain BaTiO3And (3) powder.
Comparative example 2
At room temperature, 0.08moL of nano TiO2The powder is evenly dispersed in 15mL deionized water and is slowly and evenly stirred to prepare TiO2An aqueous dispersion.
Adding 0.08moL of Ba (OH) under the protection of nitrogen at normal pressure2Adding into a three-neck round-bottom flask together with 25mL of deionized water, stirring at 100 ℃ and carrying out condensation reflux until Ba (OH)2And completely dissolving.
Adding TiO into the mixture2The aqueous dispersion was poured into the three-necked flask, and the temperature of the mixed solution was maintained at 100 ℃ and stirring was continued for 4 hours. After the reaction is finished, drying the reaction solution to obtain BaTiO3And (3) powder.
BaTiO synthesized according to comparative examples 1 to 23The performance parameters of the nanopowder are shown in Table 3, and the synthesized BaTiO3The XRD pattern and SEM picture of the nano powder are shown in figures 5-6 and 11-12 respectively. BaTiO formation in comparison with the examples3Powder of BaTiO produced by solid phase reaction (comparative example 1) at the same temperature or time3The powder has relatively large grain diameter, serious agglomeration and incomplete reaction (a small amount of unreacted TiO still exists in the product)2) And the like, BaTiO formed by the liquid phase reaction (comparative example 2)3The powder has the problems of serious agglomeration, relatively low lattice parameter c/a ratio and the like. The comparison also shows that the nano powder preparation method provided by the invention can be used for preparing nano powder at a reaction temperature or reaction time lower than that of the traditional solid phase method or liquid phase methodUnder the condition of (1), the proportion of the first barium source and the second barium source in the liquid phase reaction stage and the solid phase reaction stage is changed to regulate and control TiO2The thickness of the intermediate powder shell layer is further reduced, so that BaTiO is further reduced3The grain diameter of the nano powder and the c/a ratio of the lattice parameter are improved.
TABLE 1 reaction conditions of examples 1 to 6
TABLE 2 BaTiO synthesized by examples 1-63Performance parameters of nanopowders
Examples
Average particle diameter (nm)
Lattice constant ratio (c/a)
1
126.2
1.0085
2
131.9
1.0092
3
145.4
1.01
4
81.9
1.0074
5
70.7
1.0065
6
69.2
1.0045
TABLE 3 BaTiO synthesized by comparative examples 1-23Performance parameters of nanopowders
Comparative example
Average particle diameter (nm)
Lattice constant ratio (c/a)
1
162.5
1.0031
2
130.8
1.0019
While the invention has been shown and described with reference to certain embodiments, those skilled in the art will understand that: various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
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