Rod-like barium titanate template for textured ceramic and preparation method of rod-like barium titanate template

Abstract

The invention discloses a rod-like barium titanate template for textured ceramics and a preparation method of the rod-like barium titanate template, and belongs to the technical field of preparation of ceramics and piezoelectric materials. The method comprises the following steps: dissolving an organic titanium source in an alcohol solvent to form a transparent titanium solution; under the stirring condition, an alkaline solution is slowly added into the transparent titanium solution to adjust the pH value to be alkaline, and an alkaline titanium solution is obtained; adding a barium source and a mineralizing agent into the alkaline titanium solution, and adding a morphology regulating agent to form a uniform precursor solution; placing the precursor solution in a closed reaction kettle, and carrying out a hydrothermal reaction at 180-220 DEG C; the product obtained after the hydrothermal reaction is finished is sequentially subjected to centrifugal separation, washing and drying and then calcined at the temperature of 600-900 DEG C, and the barium titanate template crystal with the rodlike morphology is obtained.The method is simple and good in repeatability, the obtained rodlike template crystal is controllable in morphology and high in orientation induction capacity, and the density and dielectric / piezoelectric performance of the textured ceramic can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of piezoelectric ceramics and materials, specifically relating to a rod-shaped barium titanate template for textured ceramics and its preparation method. Background Technology

[0002] Barium titanate (BTO) is one of the earliest discovered ferroelectric materials, possessing excellent dielectric, ferroelectric, and piezoelectric properties. It is widely used in multilayer ceramic capacitors, piezoelectric transducers, and energy harvesting devices. To further enhance the overall performance of these materials, the concept of "textured ceramics" has emerged in recent years. This involves introducing orientation template crystals to induce preferential orientation of grains along specific crystal directions in polycrystalline ceramics, thereby achieving near-single-crystal performance while maintaining the feasibility of ceramic processing.

[0003] Traditional templates are mostly sheet-like template seed crystals, such as sheet-like BTO and Bi4Ti3O. 12 Or SrTiO3 single-crystal wafers. These templates easily induce grain growth along planar directions. <001> or <111> Planar orientation growth. However, sheet templates also have significant drawbacks: strong orientation limitation, during molding and sintering, sheet crystals are prone to random stacking or overlapping, resulting in insufficient textural orientation; low template transfer efficiency, the template sheet is prone to warping or breaking during sintering, reducing the effectiveness of orientation transfer; poor process adaptability, sheet templates are large in size and thin in thickness, resulting in uneven dispersion in molding and tape casting, and it is difficult to maintain a uniform distribution.

[0004] In comparison, rod-shaped template seed crystals exhibit significant advantages in morphology, orientation control, and texture transfer: (1) Stronger controllability of three-dimensional orientation: Rod-shaped crystals are one-dimensional growth structures, and can easily achieve directional stacking and grain boundary pairing along the c-axis. During sintering, they naturally align along the long axis of the crystal, which is conducive to forming a three-dimensional texture structure. (2) More efficient diffusion at contact points: When the rod-shaped template comes into contact with the particles, due to the large curvature of the end face and the low contact energy, it can effectively reduce the grain boundary migration barrier and promote the growth of preferred crystal orientation; (3) Higher morphological stability: Rod-shaped crystals have more uniform thickness and higher mechanical strength than plate-shaped crystals. They are not easily broken or warped and maintain morphological integrity during high-temperature texturing sintering.

[0005] In the prior art, patent CN113912106A discloses a method for preparing tetragonal phase barium titanate nanoparticles. The method involves mixing a titanium source, a barium source, a mineralizing agent, and water, followed by a hydrothermal reaction to obtain a precursor. The precursor is then calcined to obtain tetragonal phase barium titanate nanoparticles. This method employs a two-step process: hydrothermal and solid-phase methods. First, nano-sized barium titanate is prepared using a hydrothermal method, followed by solid-phase calcination to improve the crystallinity of the nano-barium titanate and eliminate hydroxyl defects generated during the hydrothermal preparation process. This method primarily addresses the problems of hydroxyl defects, large and uneven particle size present in existing methods for preparing nano-barium titanate, focusing on the quality of the nano-barium titanate material itself, particularly its crystallinity, purity, and particle size distribution.

[0006] Therefore, developing a method for preparing barium titanate template seed crystals with controllable morphology, high purity, and strong orientation ability is an important direction for effectively improving the performance of textured ceramics. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a rod-shaped barium titanate template for textured ceramics and its preparation method, which is a simple and highly controllable method for preparing rod-shaped barium titanate templates.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a rod-shaped barium titanate template for textured ceramics, comprising the following steps: An organic titanium source is dissolved in an alcohol solvent to form a transparent titanium solution; Under stirring conditions, an alkaline solution was slowly added to the transparent titanium solution to adjust the pH value to 10-13, thus obtaining an alkaline titanium solution. A barium source and a mineralizing agent are added to an alkaline titanium solution, along with a morphology modifier, to form a homogeneous precursor solution. The precursor solution was placed in a sealed reaction vessel and subjected to a hydrothermal reaction at 180℃-220℃. The product obtained after the hydrothermal reaction was centrifuged, washed and dried, and then calcined at 600℃-900℃ to obtain barium titanate template crystals with rod-shaped morphology.

[0009] Furthermore, the organic titanium source is any one of tetrabutyl titanate, isopropoxide titanate, or acetylacetone titanate; the alcohol solvent is anhydrous ethanol or isopropanol.

[0010] Furthermore, the barium source is barium nitrate, barium acetate, or barium chloride.

[0011] Furthermore, the titanium source and barium source achieve a molar ratio of Ba to Ti of 1:1.02-1:1.05; Furthermore, the mineralizing agent is sodium hydroxide or potassium hydroxide, with a concentration of 0.1 mol / L to 2 mol / L.

[0012] Furthermore, rod-shaped crystals with a length of 2 μm and a diameter of 0.25 μm were obtained when the mineralizer concentration was 0.5 mol / L; when the concentration was increased to 1 mol / L, the aspect ratio was 15. Furthermore, the morphology modifier is at least one of polyethylene glycol, polyvinylpyrrolidone, sodium citrate or sodium acetate, and the amount used is 5-20 wt% of the total mass of the raw materials.

[0013] Furthermore, the heating rate during calcination is 8℃ / min-12℃ / min, and the calcination time is 3-5h.

[0014] Secondly, the present invention can provide a rod-shaped barium titanate template for textured ceramics, which is obtained by the above-mentioned preparation method of the rod-shaped barium titanate template for textured ceramics. The obtained rod-shaped barium titanate crystals are perovskite structure phases with crystallinity not less than 96.5%, aspect ratio of 5-20, average length of 1-5 μm, diameter of 0.1-0.5 μm, dispersibility index of 0.16-0.21, and no visible agglomerates.

[0015] Alternatively, a barium titanate bulk material can be provided, using a barium titanate rod template for textured ceramics as described above as a template.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: In a hydrothermal environment, a suitable mineralizer selectively adsorbs specific crystal planes (such as the {100} plane) of barium titanate crystals, inhibiting lateral growth while promoting one-dimensional extension in the

[001] direction, thus locking the rod-like morphology microscopically; at the same time, hydrothermal conditions accelerate the growth of Ba 2+ Ti 4+ The diffusion rate is controlled to avoid morphological distortion caused by uneven local concentration, and to promote the gradual transformation of barium titanate from an amorphous precursor into a pure perovskite phase, resulting in good crystal integrity at the microscopic level.

[0017] The method described in this invention prepares rod-shaped barium titanate templates, resulting in products with controllable morphology, high purity, and a uniform and stable reaction system. This method can achieve high aspect ratio pure perovskite phase BaTiO3 rod-shaped crystals. It can also reduce the sintering temperature by approximately 50-100°C compared to traditional sheet-like template texturing processes. The process is simple and scalable, uses commonly available reaction equipment, and the reaction conditions are easy to achieve. It does not require toxic organic solvents and has good industrialization potential. Attached Figure Description

[0018] Figure 1 To implement the SEM image of the barium titanate rod in Case 1; Figure 2 To implement the SEM image of the barium titanate rod in Case 2; Figure 3The XRD diffraction pattern of the barium titanate rod in Case 1. Detailed Implementation

[0019] To more clearly illustrate this invention, a detailed description will follow. Before beginning the description, it should be emphasized that some terms used herein are not limited to their conventional dictionary definitions, but should be understood in the context of the technical background of this invention. Inventors may reasonably define relevant terms as needed to more accurately express the content of the invention. Therefore, the following description is only provided as preferred examples of the invention to help understand the technical principles, and not as a limitation on the scope of the invention. Various equivalent substitutions or improvements can be made without departing from the basic ideas and core content of this invention.

[0020] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0021] Example 1 (1) Preparation of precursor: Measure 25 mL of anhydrous ethanol into a 500 mL beaker, and add 6 mL of tetrabutyl titanate (TBOT) dropwise at a rate of 0.5 mL / min under the stirring condition of 250 r / min with a magnetic stirrer. Stir for 40 min to form a homogeneous and transparent organic titanium solution.

[0022] (2) Alkalinity control: Add 0.8 mol / L potassium hydroxide (KOH) solution dropwise at a rate of 0.2 mL / min to adjust the pH of the system to 11.5, stir for 20 min, and maintain an alkaline hydrolysis environment.

[0023] (3) Introducing barium source and mineralizing agent: Weigh 8.2g of barium acetate (Ba / Ti molar ratio 1.03) and add it to the solution. After stirring and dissolving, add 1.2g of polyvinylpyrrolidone. Polyvinylpyrrolidone accounts for 10% of the total mass of raw materials. Add 8mL of 0.8mol / L potassium hydroxide solution as mineralizing agent and continue stirring for 90min to form a stable suspension.

[0024] (4) Hydrothermal reaction: Transfer the stable suspension to a 200mL reactor, add water to 75% of the volume, seal and place in an oven, heat to 180℃ at a rate of 8℃ / min, and keep warm for 24h.

[0025] (5) Separation and calcination: After hydrothermal reaction, cool to room temperature, centrifuge at 10000 r / min for 20 min, wash with deionized water 4 times, and dry at 100℃ for 8 h; place the dried powder in a muffle furnace, heat to 750℃ at a rate of 8℃ / min, calcine for 5 h, and obtain rod-shaped BTO template seed crystals after cooling. (Ref) Figure 1 Microscopic images of rod-shaped barium titanate are provided, showing lengths of 10–18 μm, diameters of 1.0–1.5 μm, aspect ratios exceeding 10, and clear crystal faces. (Reference) Figure 3 XRD analysis showed that it was a single perovskite phase with a crystallinity of 96.5%; the dispersibility test showed that the PDI was 0.21, with no obvious agglomeration and excellent morphological stability.

[0026] Example 2 (1) Preparation of precursor: 18 mL of anhydrous ethanol was placed in a 500 mL beaker. 4.5 mL of tetrabutyl titanate was added dropwise at a rate of 0.8 mL / min under the stirring condition of 300 r / min with a magnetic stirrer. The mixture was stirred for 35 min to form a transparent and uniform organic titanium solution.

[0027] (2) Alkalinity control: Add 1.2 mol / L sodium hydroxide (NaOH) solution dropwise at a rate of 0.2 mL / min to adjust the pH of the system to 12.5, stir for 15 min to enhance the alkaline environment.

[0028] (3) Introducing barium source and mineralizing agent: Weigh 5.8g of barium nitrate (Ba / Ti molar ratio 1.03) and add it to the solution. After stirring and dissolving, add 0.8g of polyethylene glycol-4000, which accounts for 7% of the total mass of raw materials. Add 10mL of 1.2mol / L sodium hydroxide solution as mineralizing agent. The concentration of mineralizing agent is increased by 50% compared with Example 1. Stir for 70min to form a uniform suspension.

[0029] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL reactor, add water to 85% of the volume, seal and place in an oven, heat to 220℃ at a rate of 6℃ / min, and keep warm for 12h.

[0030] (5) Separation and calcination: After the reaction, the mixture was cooled to room temperature, centrifuged at 9000 r / min for 18 min, washed three times with deionized water, and dried at 90℃ for 10 h. The powder was then placed in a muffle furnace and heated to 850℃ at a rate of 12℃ / min, calcined for 3 h, and cooled to obtain rod-shaped BTO template seed crystals. (Ref) Figure 2 Microscopic images of the prepared barium titanate rods are provided in this embodiment. The length is 5~8 μm, the aspect ratio of the product is 8±2, the diameter is 0.6~1.0 μm, the aspect ratio is above 8, the rod structure is slender and uniform, the dispersion performance is excellent, there is no agglomeration, and the morphological stability is good.

[0031] Example 3 (1) Preparation of precursor: Measure 20 mL of anhydrous ethanol into a 500 mL beaker, and use a magnetic stirrer to add 5 mL of tetrabutyl titanate at a rate of 0.5 mL / min under stirring conditions of 300 r / min. Continue stirring for 30 min to form a uniform and transparent organic titanium solution.

[0032] (2) Alkalinity control: Keep stirring and slowly add 1 mol / L sodium hydroxide (NaOH) solution at a rate of 0.5 mL / min using a dropper. Monitor the pH value in real time with a pH meter and adjust the pH value of the system to 12.0. Continue stirring for 15 min to stabilize the hydrolysis environment.

[0033] (3) Introducing barium source and mineralizing agent: Weigh 6.1g of barium nitrate (Ba / Ti molar ratio 1.05) and add it to the solution obtained in step (2). Stir until completely dissolved, then add 1.0g of polyethylene glycol 6000, which accounts for 8% of the total mass of the raw materials. Add 5mL of 0.5mol / L sodium hydroxide solution as a mineralizing agent and continue stirring for 60min to form a uniform suspension.

[0034] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL polytetrafluoroethylene-lined reactor, add deionized water to 80% of the reactor volume, seal it and place it in an oven, heat it to 200℃ at a rate of 5℃ / min, and keep it at this temperature for 18h. Under this temperature keeping condition, the crystallinity of the crystals is the best.

[0035] (5) Separation and calcination: After the reaction is completed, the product is naturally cooled to room temperature. The product is poured into a centrifuge tube and centrifuged at 8000 r / min for 15 min. The supernatant is discarded. The precipitate is washed three times with deionized water and then washed once with anhydrous ethanol. It is then dried in an 80℃ forced-air drying oven for 12 h to obtain dried powder. The powder is placed in a corundum crucible and placed in a muffle furnace. The temperature is raised to 800℃ at a rate of 10℃ / min and calcined for 4 h. After natural cooling, rod-shaped BTO template seed crystals are obtained. The length is 10~18 μm, the diameter is 0.8~1.2 μm, the aspect ratio is more than 15, there is no obvious agglomeration, and it has excellent dispersion stability.

[0036] Example 4 (1) Preparation of precursor: Measure 20 mL of anhydrous ethanol into a 500 mL beaker, and use a magnetic stirrer to add 5 mL of tetrabutyl titanate at a rate of 0.5 mL / min under stirring conditions of 300 r / min. Continue stirring for 30 min to form a uniform and transparent organic titanium solution.

[0037] (2) Alkalinity control: Keep stirring and slowly add 1 mol / L sodium hydroxide (NaOH) solution at a rate of 0.5 mL / min using a dropper. Monitor the pH value in real time with a pH meter and adjust the pH value of the system to 12.0. Continue stirring for 15 min to stabilize the hydrolysis environment.

[0038] (3) Introducing barium source and mineralizing agent: Weigh 6.1g of barium nitrate (Ba / Ti molar ratio 1.05) and add it to the solution obtained in step (2). Stir until completely dissolved, then add 1.25g of polyvinylpyrrolidone, which accounts for 10% of the total mass of the raw materials. Add 5mL of 0.5mol / L sodium hydroxide solution as a mineralizing agent and continue stirring for 60min to form a uniform suspension.

[0039] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL polytetrafluoroethylene-lined reactor, add deionized water to 80% of the reactor volume, seal it and place it in an oven, heat it to 200℃ at a rate of 5℃ / min, and keep it at this temperature for 18h. Under this temperature keeping condition, the crystallinity of the crystals is the best.

[0040] (5) Separation and calcination: After the reaction is completed, the product is naturally cooled to room temperature. The product is poured into a centrifuge tube and centrifuged at 8000 r / min for 15 min. The supernatant is discarded. The precipitate is washed three times with deionized water and then washed once with anhydrous ethanol. It is then placed in an 80℃ forced-air drying oven and dried for 12 h to obtain dry powder. The powder is placed in a corundum crucible and placed in a muffle furnace. The temperature is raised to 700℃ at a rate of 10℃ / min and calcined for 5 h. After natural cooling, rod-shaped BTO template seed crystals are obtained. The length is 4~12 μm, the diameter is 0.2~0.6 μm, the aspect ratio is more than 20, there is no agglomeration, and it has excellent dispersion stability.

[0041] Example 5 (1) Preparation of precursor: Measure 20 mL of isopropanol into a 500 mL beaker, and use a magnetic stirrer to add 5 mL of isopropanol titanate at a rate of 0.2 mL / min under stirring conditions of 300 r / min. Continue stirring for 30 min to form a uniform and transparent organic titanium solution.

[0042] (2) Alkalinity control: Keep stirring and slowly add 0.1 mol / L sodium hydroxide (NaOH) solution dropwise at a rate of 0.3 mL / min using a dropper. Monitor the pH value in real time with a pH meter and adjust the pH value of the system to 10.0. Continue stirring for 15 min to stabilize the hydrolysis environment.

[0043] (3) Introducing barium source and mineralizing agent: Weigh 6.1g of barium nitrate (Ba / Ti molar ratio 1.04) and add it to the solution obtained in step (2). Stir until completely dissolved, then add 2.5g of polyethylene glycol 6000, which accounts for 20% of the total mass of raw materials. Add 5mL of 0.5mol / L sodium hydroxide solution as a mineralizing agent and continue stirring for 60min to form a uniform suspension.

[0044] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL polytetrafluoroethylene-lined reactor, add deionized water to 80% of the reactor volume, seal it and place it in an oven, heat it to 200℃ at a rate of 5℃ / min, and keep it at this temperature for 18h. Under this temperature keeping condition, the crystallinity of the crystals is the best.

[0045] (5) Separation and calcination: After the reaction is completed, the product is naturally cooled to room temperature. The product is poured into a centrifuge tube and centrifuged at 8000 r / min for 15 min. The supernatant is discarded. The precipitate is washed three times with deionized water and then washed once with anhydrous ethanol. It is then placed in an 80℃ drying oven and dried for 12 h to obtain dry powder. The powder is placed in a corundum crucible and placed in a muffle furnace. The temperature is increased to 900℃ at a rate of 10℃ / min and calcined for 2 h. After natural cooling, rod-shaped BTO template seed crystals are obtained with a length of 14~21 μm, a diameter of 1~1.6 μm, an aspect ratio of more than 15, and no obvious agglomeration.

[0046] Example 6 (1) Preparation of precursor: Measure 20 mL of anhydrous ethanol into a 500 mL beaker, and add 5 mL of isopropoxide titanate dropwise at a rate of 0.25 mL / min with a magnetic stirrer at a speed of 300 r / min. Continue stirring for 30 min to form a uniform and transparent organic titanium solution.

[0047] (2) Alkalinity control: Keep stirring and slowly add 2 mol / L sodium hydroxide (NaOH) solution at a rate of 0.4 mL / min using a dropper. Monitor the pH value in real time with a pH meter and adjust the pH value of the system to 13.0. Continue stirring for 15 min to stabilize the hydrolysis environment.

[0048] (3) Introducing barium source and mineralizing agent: Weigh 6.1g of barium nitrate (Ba / Ti molar ratio 1.04) and add it to the solution obtained in step (2). Stir until completely dissolved, then add 0.625g of polyethylene glycol 6000, which accounts for 5% of the total mass of the raw materials. Add 5mL of 2mol / L sodium hydroxide solution as a mineralizing agent and continue stirring for 60min to form a uniform suspension.

[0049] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL polytetrafluoroethylene-lined reactor, add deionized water to 80% of the reactor volume, seal it and place it in an oven, heat it to 200℃ at a rate of 5℃ / min, and keep it at this temperature for 18h. Under this temperature keeping condition, the crystallinity of the crystals is the best.

[0050] (5) Separation and calcination: After the reaction is completed, the product is naturally cooled to room temperature. The product is poured into a centrifuge tube and centrifuged at 8000 r / min for 15 min. The supernatant is discarded. The precipitate is washed three times with deionized water and then washed once with anhydrous ethanol. It is then placed in an 80℃ drying oven and dried for 12 h to obtain dry powder. The powder is placed in a corundum crucible and placed in a muffle furnace. The temperature is increased to 900℃ at a rate of 10℃ / min and calcined for 3 h. After natural cooling, rod-shaped BTO template seed crystals are obtained with a length of 11~17 μm, a diameter of 0.8~1.6 μm, an aspect ratio of more than 10, and no obvious agglomeration.

[0051] Example 7 (1) Preparation of precursor: Measure 20 mL of isopropanol into a 500 mL beaker, and use a magnetic stirrer to add 5 mL of acetylacetone titanate at a rate of 0.3 mL / min under stirring conditions of 300 r / min. Continue stirring for 30 min to form a uniform and transparent organic titanium solution.

[0052] (2) Alkalinity control: Keep stirring and slowly add 2 mol / L sodium hydroxide (NaOH) solution dropwise at a rate of 0.4 mL / min using a dropper. Monitor the pH value in real time with a pH meter and adjust the pH value of the system to 12.5. Continue stirring for 15 min to stabilize the hydrolysis environment.

[0053] (3) Introduce barium source and mineralizing agent: Weigh 6.1g of barium nitrate (Ba / Ti molar ratio 1.04) and add it to the solution obtained in step (2). Stir until completely dissolved, then add 1.0g of sodium citrate, which accounts for 8% of the total mass of the raw materials. Add 5mL of 2mol / L sodium hydroxide solution as mineralizing agent and continue stirring for 60min to form a uniform suspension.

[0054] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL polytetrafluoroethylene-lined reactor, add deionized water to 80% of the reactor volume, seal it and place it in an oven, heat it to 200℃ at a rate of 5℃ / min, and keep it at this temperature for 18h. Under this temperature keeping condition, the crystallinity of the crystals is the best.

[0055] (5) Separation and calcination: After the reaction is completed, the product is naturally cooled to room temperature. The product is poured into a centrifuge tube and centrifuged at 8000 r / min for 15 min. The supernatant is discarded. The precipitate is washed three times with deionized water and then washed once with anhydrous ethanol. It is then placed in an 80℃ forced-air drying oven and dried for 12 h to obtain dry powder. The powder is placed in a corundum crucible and placed in a muffle furnace. The temperature is raised to 700℃ at a rate of 10℃ / min and calcined for 2 h. After natural cooling, rod-shaped BTO template seed crystals are obtained. The length is 5~7 μm, the diameter is 0.2~0.5 μm, the aspect ratio is more than 15, and there is no obvious agglomeration.

[0056] Example 8 (1) Preparation of precursor: Measure 20 mL of isopropanol into a 500 mL beaker, and use a magnetic stirrer to add 5 mL of acetylacetone titanate at a rate of 0.35 mL / min under stirring conditions of 300 r / min. Continue stirring for 30 min to form a uniform and transparent organic titanium solution.

[0057] (2) Alkalinity control: Keep stirring and slowly add 0.1 mol / L sodium hydroxide (NaOH) solution dropwise at a rate of 0.35 mL / min using a dropper. Monitor the pH value in real time with a pH meter and adjust the pH value of the system to 12.0. Continue stirring for 15 min to stabilize the hydrolysis environment.

[0058] (3) Introduce barium source and mineralizing agent: Weigh 6.1g of barium nitrate (Ba / Ti molar ratio 1.04) and add it to the solution obtained in step (2). Stir until completely dissolved, then add 1.0g of sodium acetate, which accounts for 8% of the total mass of the raw materials. Add 5mL of 2mol / L sodium hydroxide solution as mineralizing agent and continue stirring for 60min to form a uniform suspension.

[0059] (4) Hydrothermal reaction: Transfer the uniform suspension to a 200mL polytetrafluoroethylene-lined reactor, add deionized water to 80% of the reactor volume, seal it and place it in an oven, heat it to 200℃ at a rate of 5℃ / min, and keep it at this temperature for 18h. Under this temperature keeping condition, the crystallinity of the crystals is the best.

[0060] (5) Separation and calcination: After the reaction is completed, the product is naturally cooled to room temperature. The product is poured into a centrifuge tube and centrifuged at 8000 r / min for 15 min. The supernatant is discarded. The precipitate is washed three times with deionized water and then washed once with anhydrous ethanol. It is then placed in an 80℃ drying oven and dried for 12 h to obtain dry powder. The powder is placed in a corundum crucible and placed in a muffle furnace. The temperature is raised to 600℃ at a rate of 10℃ / min and calcined for 2 h. After natural cooling, rod-shaped BTO template seed crystals are obtained with a length of 3.5~4.9 μm, a diameter of 0.1~0.4 μm, an aspect ratio of more than 10, and no obvious agglomeration.

[0061] Based on the above embodiments, the present invention can also provide a rod-shaped barium titanate template for textured ceramics obtained by the method of any of the above embodiments. Furthermore, a barium titanate bulk material is also provided, prepared using the rod-shaped barium titanate template for textured ceramics obtained by the method of any of the above embodiments.

[0062] In summary, the present invention provides a rod-shaped barium titanate template for textured ceramics and its preparation method. The method involves dissolving an organic titanium source in an alcohol solvent to form a transparent titanium solution; under stirring conditions, a basic solution is slowly added to the transparent titanium solution to adjust the pH to alkaline, resulting in a basic titanium solution; a barium source and a mineralizing agent are added to the basic titanium solution, along with a morphology modifier, to form a uniform precursor solution; the precursor solution is placed in a sealed reactor and subjected to a hydrothermal reaction at 180℃-220℃; after the hydrothermal reaction, the resulting product is sequentially centrifuged, washed, and dried, and then calcined at 600℃-900℃ to obtain barium titanate template crystals with a rod-shaped morphology. The method is simple, reproducible, and the resulting rod-shaped template crystals have controllable morphology and strong orientation induction ability, which can significantly improve the density and dielectric / piezoelectric properties of textured ceramics.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a rod-shaped barium titanate template for textured ceramics, characterized in that, Includes the following steps: An organic titanium source is dissolved in an alcohol solvent to form a transparent titanium solution; Under stirring conditions, an alkaline solution was slowly added to the transparent titanium solution to adjust the pH value to 10-13, thus obtaining an alkaline titanium solution. A barium source and a mineralizing agent are added to an alkaline titanium solution, along with a morphology modifier, to form a homogeneous precursor solution. The precursor solution was placed in a sealed reaction vessel and subjected to a hydrothermal reaction at 180℃-220℃. The product obtained after the hydrothermal reaction was centrifuged, washed and dried, and then calcined at 600℃-900℃ to obtain barium titanate template crystals with rod-shaped morphology.

2. The method for preparing rod-shaped barium titanate templates for textured ceramics according to claim 1, characterized in that, The organic titanium source is any one of tetrabutyl titanate, isopropoxide titanate, or acetylacetone titanate; the alcohol solvent is anhydrous ethanol or isopropanol.

3. The method for preparing rod-shaped barium titanate templates for textured ceramics according to claim 1, characterized in that, The barium source is barium nitrate, barium acetate, or barium chloride.

4. The method for preparing a rod-shaped barium titanate template for textured ceramics according to claim 1, characterized in that, Titanium and barium sources were used to achieve a molar ratio of Ba to Ti of 1:1.02-1:1.

05.

5. The method for preparing a rod-shaped barium titanate template for textured ceramics according to claim 1, characterized in that, The mineralizing agent is sodium hydroxide or potassium hydroxide, with a concentration of 0.1 mol / L to 2 mol / L.

6. The method for preparing a rod-shaped barium titanate template for textured ceramics according to claim 1, characterized in that, Rod-shaped crystals with a length of 2 μm and a diameter of 0.25 μm were obtained when the mineralizer concentration was 0.5 mol / L; when the concentration was increased to 1 mol / L, the aspect ratio was 15.

7. The method for preparing a rod-shaped barium titanate template for textured ceramics according to claim 1, characterized in that, The morphology modifier is at least one of polyethylene glycol, polyvinylpyrrolidone, sodium citrate or sodium acetate, and the amount used is 5-20 wt% of the total mass of the raw materials.

8. The method for preparing a rod-shaped barium titanate template for textured ceramics according to claim 1, characterized in that, The heating rate during calcination is 8℃ / min-12℃ / min, and the calcination time is 3-5h.

9. A rod-shaped barium titanate template for textured ceramics, characterized in that, The barium titanate template for textured ceramics is prepared by any one of claims 1-8. The resulting barium titanate crystals are perovskite structure phases with a crystallinity of not less than 96.5%, an aspect ratio of 5-20, an average length of 1-5 μm, a diameter of 0.1-0.5 μm, a dispersibility index of 0.16-0.21, and no visible agglomerates.

10. A bulk barium titanate material, characterized in that, The barium titanate rod template for textured ceramics as described in claim 9 is used as the template.

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