Barium titanate powder with high sphericity and a preparation method thereof

Abstract

The application belongs to the field of inorganic materials, and particularly relates to a preparation method of high-sphericity barium titanate powder. The method comprises the following steps: 1) preparing a functional template solution; 2) respectively preparing an organic titanium complex solution and a barium-containing aqueous solution as a titanium source solution and a barium source solution; 3) slowly adding the titanium source solution into the functional template solution, continuously stirring for adsorption positioning, then adding the barium source solution to adjust the pH value, and then performing homogenization stirring to obtain a precursor solution; and 4) performing hydrothermal reaction on the precursor solution, centrifuging, cleaning and drying after the hydrothermal reaction to obtain the high-sphericity barium titanate powder. The method overcomes the defects of traditional liquid-phase methods and solid-phase methods, and forms a brand-new interface limited solid-phase growth method in cooperation, so that the morphology characteristics and particle size of the barium titanate powder can be effectively controlled. The particle size uniformity of the product is high, the sphericity is much higher than that of existing industrial solutions, and the overall scheme has relatively low industrialization difficulty, which is conducive to the popularization of industrialization.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials, and specifically designs a method for preparing barium titanate powder with high sphericity. Background Technology

[0002] Barium titanate (BaTiO3), a key functional ceramic material, is hailed as the "backbone of the electronic ceramics industry" due to its excellent dielectric, ferroelectric, and piezoelectric properties. Especially in the field of multilayer ceramic capacitors (MLCCs), barium titanate powder is the core raw material that determines its performance.

[0003] As electronic components evolve towards miniaturization, high integration, and high reliability, the performance requirements for barium titanate powder are becoming increasingly stringent. Among these requirements, "high sphericity" has become one of the key indicators for evaluating the quality of high-end powders. Powders with high sphericity possess excellent flowability and dispersibility, enabling the achievement of higher packing density. This facilitates the preparation of thinner and more uniform dielectric layers, thereby improving the capacitance density, reliability, and lifespan of MLCCs.

[0004] Generally, sphericity is measured by the ratio of the major and minor axes of a particle in a two-dimensional projection image. The closer the ratio of the major and minor axes is to 1, the higher the sphericity. For example, in the industry, particles with a major-to-minor axis ratio ≤ 1.2 are often considered spherical. However, in fields with higher precision requirements, a more precise definition involves the particle's projected area (A) and perimeter (P), with sphericity Ψ = (4πA) / P. 2 For an ideal circle, Ψ=1.

[0005] Existing technologies for preparing barium titanate powder typically include high-temperature solid-state methods, high-energy ball milling / mechanical chemical methods, liquid-phase chemical methods, and gas-phase synthesis methods. However, high-temperature solid-state methods and high-energy ball milling methods cannot effectively produce barium titanate powder with high sphericity. Liquid-phase chemical methods and gas-phase synthesis methods, specifically hydrothermal methods, microemulsion methods, spray pyrolysis methods, and plasma spheroidization methods, can all relatively effectively achieve the preparation of barium titanate powder with high sphericity, typically controlling the sphericity Ψ to an extremely high level of approximately 1.05–1.07. Microemulsion methods and partial plasma spheroidization methods, in particular, can even control the sphericity to an ultra-high level of 1.00–1.03. However, all of these methods face significant industrialization challenges. It is precisely the microemulsion method and plasma spheroidization method that have currently been largely confined to the laboratory stage due to their extremely high cost and difficulty, and no feasible industrialization solutions have yet been found. Summary of the Invention

[0006] To address the problems of existing common industrial preparation methods for barium titanate powder failing to effectively produce powders with high sphericity, exhibiting poor particle size controllability and relatively limited uniformity, and having most solutions for preparing barium titanate powder with high sphericity limited to the laboratory stage and unable to be industrialized, this invention provides a method for preparing barium titanate powder with high sphericity, as well as the resulting barium titanate powder with high sphericity.

[0007] The main objective of this invention is: I. It can effectively control the sphericity Ψ of barium titanate powder to between 1.00 and 1.03, thus realizing the preparation of barium titanate powder with ultra-high sphericity; Second, it can effectively control the particle size and uniformity of barium titanate powder; Third, it is applicable to industrialized production and implementation.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A method for preparing barium titanate powder with high sphericity. The method includes: 1) Prepare functionalized template solutions; 2) Prepare an organic titanium complex solution and a barium-containing aqueous solution as the titanium source solution and barium source solution, respectively; 3) The titanium source solution was slowly added to the functionalized template solution, and the adsorption and localization were carried out by continuous stirring. Then, the barium source solution was added to adjust the pH value, and then the mixture was homogenized and stirred to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction. After the hydrothermal reaction was completed, the mixture was centrifuged, washed, and dried to obtain barium titanate powder with high sphericity.

[0010] As a preferred option Step 1) The functionalized template solution is an aqueous solution of a functionalized amphiphilic block copolymer; The preparation method of the functionalized amphiphilic block copolymer aqueous solution is as follows: An aqueous solution of amphiphilic block copolymer with a concentration of 0.5–1.5 wt% was prepared, and after stirring in a low-temperature water bath, a modifier was added. The reaction was continued under water bath conditions to obtain a functionalized amphiphilic block copolymer aqueous solution.

[0011] As a preferred option The amphiphilic block copolymer is a PEO-PPO-PEO block copolymer; The low-temperature water bath stirring is carried out at 40–50 °C for 45–75 min. The modifier is 3-aminopropyltriethoxysilane, and the amount of modifier used is 1-2 mL / 100 mL of an amphiphilic block copolymer aqueous solution; The stirring reaction under the water bath condition is carried out at 50-60℃ for 5-6 hours.

[0012] As a preferred option Step 2) The organic titanium complex solution is prepared by taking tetraisopropyl titanate, citric acid and anhydrous ethanol in a ratio of 1 mL: (0.3~0.5) g: 3~5 mL. Tetraisopropyl titanate and citric acid are added to anhydrous ethanol and stirred until clear to complete the preparation. Step 2) The barium-containing aqueous solution is a 0.10-0.15 mol / L barium hydroxide aqueous solution.

[0013] As a preferred option Step 3) The amount of titanium source solution used is 20-30 mL / 100 mL of functionalized template solution; Step 3) The titanium source solution is added at a rate of 3-5% VOL / min (i.e., 3-5% of the total volume of titanium source solution is added per minute). Stirring is maintained during the addition process, and stirring is continued for 50-70 minutes after the addition is completed to allow for adsorption and localization.

[0014] As a preferred option Step 3) The barium source solution is added to adjust the overall solution pH to 12-13; Step 3) involves homogenization and stirring for 1 to 3 hours.

[0015] As a preferred option Step 4) The hydrothermal reaction is controlled at a temperature of 180–200 °C and a reaction time of 12–24 h. After the hydrothermal reaction in step 4) is completed, calcination treatment can be selected. The calcination process is controlled at a calcination temperature of 500–600 °C and a calcination time of 2–4 h.

[0016] As a preferred option Step 4) The cleaning process includes cleaning with deionized water and cleaning with anhydrous ethanol.

[0017] A barium titanate powder with high sphericity, wherein the sphericity Ψ is 1.00 to 1.03.

[0018] The core of this invention lies in constructing a controllable functionalized soft template, and then using this template to achieve highly controllable growth from the outside in to prepare barium titanate powder with high sphericity. Essentially, it can be seen as an organic combination of the "liquid phase method" and the "solid phase method." While its reaction process is traditionally closer to the reaction environment of the liquid phase method, its nucleation and growth are inextricably linked to the solid phase method. This is because functionalized polymer micelles in solution are soft solid entities with a clearly defined spherical interface and stable structure, which differs from pure liquid-phase homogeneous nucleation. Therefore, it is referred to by technicians as the "interface-confined solid-phase growth method."

[0019] In this preparation process, the first step is to select amphiphilic block copolymers, especially the three block copolymers F127, F68 and P123 that have been effectively verified by experiments in this invention, to fully dissolve them and form spherical micelles with hydrophobic PPO as the core and hydrophilic PEO as the crown. In this process, the selection and concentration of block copolymers will affect the micelle morphology and micelle size. In order to effectively form spherical micelles at the nanoscale to microscale, the concentration of amphiphilic block copolymers needs to be controlled at 0.5 to 1.5 wt%. Too low a concentration will easily lead to a small number of micelles and instability, while too high a concentration will easily lead to changes in micelle morphology and the formation of liquid crystal phase.

[0020] Subsequently, this invention first functionalizes the micelles using 3-aminopropyltriethoxysilane (APTES). The ethoxy group (-OC2H5) slowly hydrolyzes to generate silanol groups (-SiOH). These silanol groups interact with the polar region (PEO crown) of the polymer micelles via hydrogen bonding, and can also undergo condensation or interact with titanium species, thus stably anchoring to the micelle surface. This effectively "installs" probes for the directional adsorption of titanium on the template, forming "functionalized polymer micelles" with a surface rich in amino and siloxane groups. These micelles serve as soft templates for confined reactions, and their surface amino groups preferentially and directionally adsorb titanium species from the solution through electrostatic interactions.

[0021] Then, specific titanium and barium sources were introduced. Tetraisopropyl titanate (TTIP) used in this invention is a commonly used titanium source, but it undergoes violent hydrolysis in water to form TiO2 precipitate, which is difficult to control. Citric acid (CA) is used as a complexing agent, as the carboxyl and hydroxyl groups in CA can react with TiO2. 4+ Forming stable water-soluble complexes (such as [Ti(C6H4O7)3) 8-(or similar structures), which effectively inhibits the premature hydrolysis of TTIP and ensures that the titanium source can exist stably at the molecular level in the ethanol-water mixture system. This is a prerequisite for achieving subsequent controllable adsorption and uniform reaction. Using a 0.10-0.15 mol / L barium hydroxide aqueous solution, barium hydroxide is soluble and provides abundant barium ions and hydroxide ions. Under high pH conditions, barium hydroxide exists stably and will not decompose.

[0022] Adding the titanium source slowly to the template solution, rather than in the reverse order, is the core operation for controlling the nucleation site. This involves functionalizing the amino groups (-NH2 / -NH3) on the micelle surface. + In high-pH precursor environments, they are positively charged or have strong coordination abilities, while titanium citrate complexes and / or titanate species (such as [TiO(OH)3]) released / transformed at high pH are... - Or [Ti(OH)6] 2- The titanium species, either negatively charged or possessing coordination sites, preferentially and directionally adsorb onto the surface of the micelle template through electrostatic or coordination interactions. After continuous stirring for 50–70 minutes, adsorption equilibrium is reached. Then, a barium source solution is added and adjusted to a strongly alkaline environment. Under this environment, the titanium species adsorbed on the template rapidly react with barium and hydroxide ions in the solution, generating amorphous or extremely fine barium titanate (BaTiO3) primary particles, which are then "anchored" to the template surface. This anchoring process is not only the nucleation process for primary particle formation but also crucial for the "confined growth" in this invention, because the titanium species are adsorbed at the crown of the spherical micelles and are first exposed to barium and hydroxide ions. The outermost titanium species are the ones that react and nucleate. This allows, under suitable stirring conditions, the crystal nuclei to first grow slowly and adhere to the canopy with the same curvature as the surface of the spherical micelles, forming a locally continuous but overall discontinuous "shell." The preferential formation of this "shell" effectively ensures its spherical growth trend and creates a confined growth space. At this point, the crystal nucleus is anchored on the canopy surface, and its growth direction is restricted by the spherical contour of the micelles, allowing it to grow only in a direction parallel to the micelle surface, avoiding deviation from the spherical shape, thus initially forming a "spherical crystallization layer." However, it is important to avoid a completely enclosed shell, which would result in the formation of a composite sphere of titanium species and organic polymers encapsulated by a barium titanate shell, rather than the target barium titanate spherical powder.

[0023] Based on this, further hydrothermal treatment causes the PPO core of the micelles to swell, and the gaps between the molecular chains to expand significantly from the initial state, providing space for the crystal nuclei to grow inward. Simultaneously, a small amount of unadsorbed Ti in the solution... 4+ with Ba 2+Driven by continuous diffusion into the micelle region to replenish the reaction raw materials, the BaTiO3 crystal nuclei in the canopy undergo "bidirectional growth": on the one hand, they grow outwards, but the growth rate is extremely slow due to the concentration of surrounding raw materials, especially titanium ions; on the other hand, they grow inwards, with the swollen PPO interstitial spaces providing channels for nuclei growth, and the Ti surrounding the core... 4+ with Ba 2+ The concentration is much higher than on the outside, and the growth rate is extremely fast, becoming the main growth direction, thus effectively ensuring the formation of the target barium titanate spherical powder particles. As the hydrothermal reaction continues, BaTiO3 nuclei grow and overlap, gradually filling the canopy and swollen core space of the micelles—from the canopy to the core, the growth and filling of the nuclei occur simultaneously, eventually completely filling the internal space of the entire micelle. Because the spherical outline of the micelles always plays a "confining constraint" role on the growth of the nuclei, the nuclei cannot break through the spherical boundary of the micelles to grow. Therefore, the BaTiO3 particles after filling can completely replicate the spherical morphology of the micelles.

[0024] Then, through separation and cleaning, residual ionic impurities and organic residues can be effectively removed to obtain the target barium titanate spherical particles. However, calcination can be performed in conjunction with this process. Calcination can remove residual organic residues more thoroughly and effectively improve the crystallinity of the product. The main purpose is to optimize the crystallinity of the product. However, attention must be paid to the calcination temperature and duration to avoid sintering and agglomeration, which would damage the spherical morphology.

[0025] The beneficial effects of this invention are: This invention overcomes the shortcomings of traditional liquid-phase and solid-phase methods, and the two work together to form a novel interface-confined solid-phase growth method. This method can effectively control the morphology and particle size of barium titanate powder, and the product has high particle size uniformity and sphericity far exceeding that of existing industrial solutions. Moreover, the overall solution is relatively easy to industrialize, which is conducive to its industrial promotion. Attached Figure Description

[0026] Figure 1 This is a set of SEM characterization results of the products from Example 1, Comparative Examples 1-3, and Examples 5-6. Detailed Implementation

[0027] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0028] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0029] Example 1 A barium titanate powder with high sphericity is prepared by the following method: 1) Dissolve 0.5 wt% F127 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) in water bath at 40 ℃ for 60 min. Then add 3-aminopropyltriethoxysilane at a ratio of 1 mL per 100 mL of F127 aqueous solution and continue stirring at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5. Then, the mixture was homogenized and stirred for 2 h to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0030] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0031]

[0032] The characterization results above show that the product obtained in this example has extremely high sphericity and exhibits good particle size uniformity and good dielectric properties. Furthermore, the density of the product was measured and calculated using the water displacement method, and the results show that the density of the product in this example is approximately 5.93 g / cm³. 3The density is close to that of barium titanate, indicating that the overall powder particles have a high density, and the solid particles required for the target are obtained.

[0033] Example 2 Based on the product of Example 1, it was calcined at 600 °C for 3 h in air to obtain the product. The product of this example was characterized in the same way as that of Example 1, and the characterization results are shown in the table below.

[0034]

[0035] Comparing the data in the table above with that in Example 1, it is clear that calcination treatment has little effect on the particle size and uniformity of the product, with almost no change. However, the sphericity is slightly worse. In terms of dielectric properties, the dielectric properties of the product after calcination treatment can be significantly optimized.

[0036] Based on the actual use of barium titanate powder, it is often required to undergo calcination in applications such as the preparation of MLCC ceramics. Therefore, this process can be omitted in the actual preparation of barium titanate powder to reduce industrialization costs.

[0037] Example 3 A barium titanate powder with high sphericity is prepared by the following method: 1) Dissolve F127 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) in an aqueous solution with a concentration of 1.0 wt% by stirring in a water bath at 40 ℃ for 60 min. Then add 3-aminopropyltriethoxysilane at a ratio of 1 mL per 100 mL of F127 aqueous solution and continue stirring at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5. Then, the mixture was homogenized and stirred for 2 h to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0038] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0039]

[0040] Based on the characterization results above, compared to Example 1, the product in this example exhibits a larger particle size, but other properties are essentially the same as in Example 1. Regarding density, the product in this example shows a slight decrease, approximately 5.91 g / cm³. 3 .

[0041] Example 4 A barium titanate powder with high sphericity is prepared by the following method: 1) A 1.5 wt% aqueous solution of F127 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) was dissolved by stirring in a water bath at 40 ℃ for 60 min. Then, 3-aminopropyltriethoxysilane was added at a ratio of 1 mL per 100 mL of F127 aqueous solution. The reaction was continued at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5. Then, the mixture was homogenized and stirred for 2 h to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0042] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0043]

[0044] Based on the characterization results above, compared to Example 1, the product in this example exhibits a larger particle size, while its density shows a significant decrease, approximately 5.82 g / cm³. 3 This is mainly because as the particle size increases, the difficulty of forming a densely packed core during the actual particle nucleation and growth process also increases, which significantly affects the dielectric properties of the product.

[0045] Furthermore, a comparison of Examples 1 and 3-4 clearly shows that the sphericity decreases slightly with increasing block copolymer concentration. This is mainly because the concentration of the block copolymer itself affects the micelle morphology, thus requiring strict control of the concentration.

[0046] Comparative Example 1 A barium titanate powder with high sphericity is prepared by the following method: 1) Dissolve 0.5 wt% F127 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) in water bath at 40 ℃ for 60 min. Then add 3-aminopropyltriethoxysilane at a ratio of 1 mL per 100 mL of F127 aqueous solution and continue stirring at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) Mix the titanium source solution and the functionalized template solution directly at a ratio of 25 mL: 100 mL, immediately add the barium source solution to adjust the pH value to about 12.5, and then homogenize and stir for 3 h to obtain the precursor solution; 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0047] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0048]

[0049] The characterization results show that the sample obtained in this example has a significantly increased particle size and a surge in the coefficient of variation, while its sphericity decreases. Although it still maintains relatively good nodal performance, the sphericity is clearly far inferior to that of Example 1. This is mainly because direct mixing of the titanium source solution and the functionalized template solution easily leads to local enrichment and uneven distribution of titanium species, resulting in growth rate differences between regions and local areas during the subsequent conversion to barium titanate. Although the soft template still has a certain confinement effect, it is far less than expected.

[0050] Comparative Example 2 A barium titanate powder with high sphericity is prepared by the following method: 1) Dissolve 0.5 wt% F127 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) in water bath at 40 ℃ for 60 min. Then add 3-aminopropyltriethoxysilane at a ratio of 1 mL per 100 mL of F127 aqueous solution and continue stirring at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5 to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0051] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0052]

[0053] Based on the characterization results above, the particle size and overall coefficient of variation in this example are relatively closer to those of Example 1, but the sphericity and dielectric properties are inferior to those of Comparative Example 1. This is because, after adding the barium source solution, hydrothermal treatment was performed directly. Although the main growth initiation point was still at the crown of the spherical micelles, the growth anisotropy decreased, which led to an increase in the outward growth rate. Furthermore, the "confined hard shell" could not be formed in time, resulting in a significant decrease in sphericity and a decrease in the degree of internal densification.

[0054] Comparative Example 3 A barium titanate powder with high sphericity is prepared by the following method: 1) Dissolve 0.5 wt% F127 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) in water bath at 40 ℃ for 60 min. Then add 3-aminopropyltriethoxysilane at a ratio of 1 mL per 100 mL of F127 aqueous solution and continue stirring at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5. Then, the mixture was homogenized and stirred for 5 h to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0055] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0056]

[0057] Based on the above characterization results, Comparative Example 3 exhibits a microstructure most similar to that of Example 1, and is even more... Figure 1 The SEM characterization images shown include the products of Example 1, Comparative Examples 1-3, and the products of subsequent Examples 5 and 6. From... Figure 1 It is evident that the product of Comparative Example 3 has the highest sphericity, but its overall dielectric properties are severely reduced. This is mainly due to the excessively long period of homogenization and stirring, which leads to an excessive reaction between the adsorbed titanium species and the barium source solution, resulting in a completely sealed shell. The interior cannot be further effectively converted into barium titanate, and the residual polymer is encapsulated inside, making it difficult to remove, thus forming dopant.

[0058] Example 5 A barium titanate powder with high sphericity is prepared by the following method: 1) Dissolve F68 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) in an aqueous solution with a concentration of 0.5 wt% by stirring in a water bath at 40 ℃ for 60 min. Then add 3-aminopropyltriethoxysilane at a ratio of 1 mL per 100 mL of F68 aqueous solution and continue stirring at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5. Then, the mixture was homogenized and stirred for 2 h to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0059] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0060]

[0061] The characterization results above show that the product in this example also exhibits extremely high sphericity and particle size uniformity. However, compared to Example 1, the particle size is slightly reduced after using the F68 triblock copolymer in this example. It is evident that different triblock copolymers can produce significantly different actual preparation effects; for example, some amphiphilic block copolymers cannot form spherical micelles and therefore cannot be used in this invention.

[0062] Example 6 A barium titanate powder with high sphericity is prepared by the following method: 1) A 0.5 wt% aqueous solution of P123 (a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, PEO-PPO-PEO) was stirred in a water bath at 40 ℃ for 60 min to fully dissolve it. Then, 3-aminopropyltriethoxysilane was added at a ratio of 1 mL per 100 mL of P123 aqueous solution. The reaction was continued at 55 ℃ for 6 h to obtain the functionalized template solution. 2) Take tetraisopropyl titanate, citric acid and anhydrous ethanol according to the ratio of 1 mL: 0.4 g: 4 mL. Add tetraisopropyl titanate and citric acid to anhydrous ethanol and stir until clear to obtain an organic titanium complex solution, which is used as the titanium source solution. Use 0.15 mol / L barium hydroxide aqueous solution as the barium source solution. 3) The titanium source solution was slowly added to the functionalized template solution at a ratio of 25 mL: 100 mL. The addition rate of the titanium source solution was 3% VOL / min. After stirring continuously for 60 min for adsorption and localization, the barium source solution was added to adjust the pH value to about 12.5. Then, the mixture was homogenized and stirred for 2 h to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction at 200 °C for 18 h. After the hydrothermal reaction was completed, the solid product was obtained by centrifugation. The solid product was ultrasonically cleaned three times each with deionized water and anhydrous ethanol, and then vacuum dried at 80 °C to obtain barium titanate powder with high sphericity.

[0063] The product obtained in this example was characterized, mainly by using dynamic light scattering (DLS) to characterize the particle size and uniformity (coefficient of variation, CV), using electron microscopy to calculate the sphericity (Ψ), and using an LCR meter (1 kHz to press the powder into a Φ10 mm × 2 mm disc coated with silver as a standard sample) to characterize the room temperature dielectric constant (εr) and dielectric loss (tanδ). The characterization results are shown in the table below.

[0064]

[0065] Based on the characterization results above, the low-concentration P123 amphiphilic block copolymer used in this example showed a significant decrease in sphericity and dielectric properties compared to the products of Examples 1 and 5. This is mainly due to the short PPO chain and long PEO chain, which easily forms micelles of other shapes, such as rod-shaped or worm-shaped. Therefore, in multiple experiments, it was shown that P123 can only achieve the preparation of spherical barium titanate powder under low concentration (0.5wt%) conditions. For other amphiphilic block copolymers, it is necessary to explore the conditions for forming spherical micelles in greater depth. However, these conditions can usually be determined within a few experiments without additional creative effort, so they should also be included in the scope of protection of this invention.

Claims

1. A method for preparing barium titanate powder with high sphericity, characterized in that, The method includes: 1) Prepare functionalized template solutions; 2) Prepare an organic titanium complex solution and a barium-containing aqueous solution as the titanium source solution and barium source solution, respectively; 3) The titanium source solution was slowly added to the functionalized template solution, and the adsorption and localization were carried out by continuous stirring. Then, the barium source solution was added to adjust the pH value, and then the mixture was homogenized and stirred to obtain the precursor solution. 4) The precursor fluid was subjected to a hydrothermal reaction. After the hydrothermal reaction was completed, the mixture was centrifuged, washed, and dried to obtain barium titanate powder with high sphericity. Step 1) The functionalized template solution is an aqueous solution of a functionalized amphiphilic block copolymer; The preparation method of the functionalized amphiphilic block copolymer aqueous solution is as follows: An aqueous solution of amphiphilic block copolymer with a concentration of 0.5–1.5 wt% was prepared, and after stirring in a low-temperature water bath, a modifier was added. The reaction was continued under water bath conditions to obtain a functionalized aqueous solution of amphiphilic block copolymer. The amphiphilic block copolymer is a PEO-PPO-PEO block copolymer; The PEO-PPO-PEO block copolymer is F127, F68, or P123, wherein the aqueous solution concentration of the amphiphilic block copolymer prepared with F127 is 0.5–1.5 wt%, and the aqueous solution concentration of the amphiphilic block copolymer prepared with F68 and P123 is 0.5 wt%. The low-temperature water bath stirring is carried out at 40–50 °C for 45–75 min; The modifier is 3-aminopropyltriethoxysilane, and the amount of modifier used is 1-2 mL / 100 mL of an amphiphilic block copolymer aqueous solution; The stirring reaction under the water bath condition is carried out at 50-60℃ for 5-6 hours. Step 3) The amount of titanium source solution used is 20-30 mL / 100 mL of functionalized template solution; Step 3) The titanium source solution is added at a rate of 3-5% VOL / min, and stirring is maintained during the addition process. After the addition is completed, stirring is continued for 50-70 min to allow for adsorption and localization. Step 3) involves homogenization and stirring for 1–3 hours.

2. The method for preparing barium titanate powder with high sphericity according to claim 1, characterized in that, Step 2) The organic titanium complex solution is prepared by taking tetraisopropyl titanate, citric acid and anhydrous ethanol in a ratio of 1 mL: (0.3~0.5) g: 3~5 mL. Tetraisopropyl titanate and citric acid are added to anhydrous ethanol and stirred until clear to complete the preparation. Step 2) The barium-containing aqueous solution is a 0.10-0.15 mol / L barium hydroxide aqueous solution.

3. The method for preparing barium titanate powder with high sphericity according to claim 1, characterized in that, Step 3) The barium source solution is added to adjust the overall solution pH to 12-13.

4. The method for preparing barium titanate powder with high sphericity according to claim 1, characterized in that, Step 4) The hydrothermal reaction is controlled at a temperature of 180–200 °C and a reaction time of 12–24 h. Step 4) involves calcination after the hydrothermal reaction is completed. The calcination treatment is controlled at a calcination temperature of 500–600 °C and a calcination time of 2–4 h.

5. A method for preparing barium titanate powder with high sphericity according to claim 1 or 4, characterized in that, Step 4) The cleaning process includes cleaning with deionized water and cleaning with anhydrous ethanol.

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