Spindle structure barium tungsten copper oxide high dielectric ceramic powder and preparation method thereof
By using the gel seeding method and surfactant regulation, barium tungsten copper oxide high-dielectric ceramic powder with a spindle structure was prepared, solving the problems of uneven grain growth and low density, and achieving high dielectric properties and good temperature stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN UNIV OF TECH
- Filing Date
- 2024-05-22
- Publication Date
- 2026-07-14
AI Technical Summary
Existing high-dielectric ceramic materials suffer from uneven grain growth, low density, and high porosity during preparation, resulting in low performance and poor temperature stability, which limits their application in high-dielectric-constant materials.
A high-dielectric-content barium tungstate ceramic powder with a spindle structure was prepared by using the gel seeding method and surfactant regulation to control the nucleation and growth process. The specific steps include batching, pre-firing, granulation, pressing, debinding and sintering, and adjusting the pH value to control the dielectric properties.
High-dielectric ceramic powder with regular shape and uniform particle size was obtained. The dielectric constant increased with increasing pH value, and the dielectric loss decreased with increasing pH value. The synthesized powder has high activity and excellent performance, which solves the problems of density and stability of ceramic materials in traditional methods.
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Figure CN118598658B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of dielectric ceramic materials technology, specifically relating to high-dielectric ceramic powder of barium tungsten copper oxide with a spindle structure, and also to a method for preparing high-dielectric ceramic powder of barium tungsten copper oxide with a spindle structure. Background Technology
[0002] High-capacity electronic ceramic capacitors (MLCCs) are key components in the development of the electronic information industry. High-dielectric-constant materials are fundamental to capacitor development and are a key material in the development of new capacitor energy storage materials under the national new materials industry development plan. In circuits, they mainly play roles such as filtering, coupling, decoupling, and resonance, and are widely used in electronic circuits and electronic equipment in fields such as electronic communications, home appliances, and industrial instruments. With the development of the electronic information industry, higher requirements are placed on MLCCs, namely high reliability and large specific volume capacitance (high dielectric constant) to meet higher application requirements. In recent years, domestic and international research on high-dielectric-constant dielectric materials has largely focused on perovskite-structured barium titanate (BaxSr) materials. 1-x Ferroelectric ceramic materials such as TiO3 and lead zirconate titanate (Pb(Zr,Ti)O3) are widely used. However, their development is limited by poor thermal stability due to the ferroelectric-paraelectric phase transition at the Curie temperature. Since 2000, new high-dielectric materials such as CCTO compounds and Ba-based composite perovskite materials have attracted great attention from the scientific community. Among these materials, CCTO compounds exhibit the best performance, and high dielectric properties have also been achieved through (Nb+In) co-doping of rutile TiO2. However, both TiO2-based and CCTO-based materials suffer from problems such as unclear high dielectric constant mechanisms and high losses, which limit their applications. A novel barium tungsten copper oxide (Ba(Cu)O3) 1 / 2 W 1 / 2 The discovery of O3:BCW-based high-dielectric ceramic materials has pointed the way for improving dielectric properties and exploring the high-dielectric mechanism, enabling people to improve performance by introducing dopants and reveal the source of their high dielectric properties, thereby expanding their applications.
[0003] For ceramic materials, the chemical activity, chemical homogeneity, and grain morphology and size of ceramic powders have a significant impact on the later sintering and electrical properties of bulk ceramic samples. In recent years, there have been improvements in material preparation methods, such as the solid-state reaction method. However, when preparing barium tungstate copper tungstate ceramics using this method, the uneven grain growth, low density, and high porosity result in low performance and poor temperature stability of the high-dielectric ceramic materials. An improved method of the sol-gel method, namely the sol-seed method, decomposes the reaction process of the sol-gel method. By controlling the nucleation and growth processes, it reduces uneven nucleation and large-scale agglomeration, which helps to prepare highly active nanomaterials with controllable size and uniform morphology. Summary of the Invention
[0004] The purpose of this invention is to provide a high-dielectric ceramic powder of barium tungsten copper oxide with a spindle structure, which has a spindle structure, uniform particles, and high density.
[0005] Another objective of this invention is to provide a method for preparing barium tungsten copper oxide high-dielectric ceramic powder with a spindle structure.
[0006] The technical solution of this invention is a high-dielectric ceramic powder of barium tungsten copper oxide with a spindle structure, the molecular formula of which is Ba(Cu) 0.5 W 0.5 O3 has high dielectric properties and a spindle-shaped microstructure.
[0007] The invention is further characterized in that,
[0008] The barium tungstate copper oxide high-dielectric ceramic powder contains no impurity phases and exhibits high dielectric constant at a frequency of 10⁻⁶. 8 Below Hz, the dielectric constant increases with increasing pH value, while the dielectric loss decreases with increasing pH value.
[0009] Another technical solution of the present invention is a method for preparing barium tungsten copper oxide high-dielectric ceramic powder with a spindle structure, which is specifically implemented according to the following steps:
[0010] Step 1: Prepare precursor powder by mixing ingredients;
[0011] Step 2: Pre-calcination to obtain pre-calcined powder;
[0012] Step 3: Granulation to obtain spherical powder particles;
[0013] Step 4: Tableting;
[0014] Step 5: Remove glue;
[0015] Step 6: Sintering;
[0016] Step 7: Burning silver.
[0017] Another feature of the present invention is that,
[0018] Step 1 is as follows:
[0019] Step 1.1 Weigh the raw materials according to the molar ratio of Ba(NO3)2:Cu(NO3)2:ammonium metatungstate of 1.7-2.3:0.7-1.3:0.7-1.3, and introduce them into a beaker. At the same time, add deionized water. The molar ratio of the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2, and ammonium metatungstate to deionized water is 0.8-1.2:0.8-1.2. Heat the solution in an oil bath at 60℃-100℃ for 10-50 minutes to obtain solution A.
[0020] Step 1.2: Weigh equal amounts of surfactant and deionized water into an oil bath and maintain the oil bath at 60℃~100℃. Stir thoroughly for 20min~40min to prepare solution B.
[0021] Step 1.3: Weigh 1 / 3 to 1 / 2 of solution A and add it dropwise to solution B. Place the mixture in an oil bath at 60℃ to 100℃ and stir continuously for 40 to 80 minutes to form precursor sol seeds.
[0022] Step 1.4: Pour the remaining solution A into the oil bath from Step 1.3, maintain the oil bath at 60-100°C, and stir constantly for 20-40 minutes.
[0023] Step 1.5: Add a 0.01 mol / L ammonia solution dropwise to the product mixture from Step 1.4 and stir for 60 min to 120 min. Adjust the pH value to ensure the seeds grow evenly.
[0024] Step 1.6: After the solution in Step 1.5 forms a stable gel, age it at room temperature for 10-16 hours, then wash it with deionized water 3-5 times, dry it at 80-160℃ for 12-24 hours, and grind it to obtain the precursor powder.
[0025] In step 1.2, the molar ratio of the surfactant to the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2 and ammonium metatungstate is 0.8-1.2:0.8-1.2; the surfactant is at least one of citric acid and polyethylene glycol, and the molar ratio of citric acid to polyethylene glycol is 0-1.2:0-1.2.
[0026] In step 1.5, the reaction temperature is 20℃~40℃ in a water bath, the reaction time is 12h~24h, and the pH value is adjusted to 2-10.
[0027] Step 2 specifically involves placing the precursor powder in an alumina crucible and pre-calcining it at 750℃~1150℃ for 2~6 hours, cooling it to room temperature, and grinding it with a mortar and pestle to obtain the pre-calcined powder.
[0028] Step 3 specifically involves adding a 5wt% PVA polyvinyl alcohol solution dropwise to the pre-calcined powder, stirring thoroughly, grinding finely, drying naturally, and passing it through a 120-180 mesh sieve to form spherical powder particles.
[0029] Step 4 specifically involves placing the granulated spherical powder particles into a mold and pressing them into ceramic green bodies under a pressure of 40MPa to 80MPa.
[0030] Step 5 specifically involves placing the ceramic green body in a muffle furnace and heating it to 500-700°C at a heating rate of 1-3°C / min, holding it at that temperature for 1-4 hours, and then allowing it to cool naturally to room temperature.
[0031] Step 6 specifically involves heating the blank after debinding to 1000-1200℃ at a heating rate of 8-12℃ / min, sintering for 12-16 hours, and then cooling it naturally to room temperature with the furnace.
[0032] Step 7 specifically involves grinding, polishing, ultrasonically cleaning, and drying the sintered ceramic from step 6. Then, a silver paste with a thickness of 0.01 mm to 0.03 mm is coated on both sides of the ceramic surface. The ceramic is then placed in a resistance furnace and calcined at 650℃ to 1000℃ for 8 min to 12 min. After natural cooling to room temperature, barium tungstate high-dielectric ceramic powder is produced.
[0033] The beneficial effects of this invention are:
[0034] The spindle-structured barium tungsten copper oxide high-dielectric ceramic powder of the present invention has a regular shape, good uniformity, high activity of the synthesized powder, and uniform particle size.
[0035] The present invention discloses a method for preparing barium tungsten copper oxide (BCW) high-dielectric ceramic powder with a spindle structure. This method employs a gel seeding process, using surfactants and pH adjustments to obtain BCW ceramic powders of different sizes and controllable morphologies. Compared to barium tungsten copper oxide ceramics prepared by traditional solid-state methods, the BCW ceramic powder prepared by the present invention exhibits lower synthesis and sintering temperatures, better temperature stability, better uniformity, higher activity, more complete reaction, higher dielectric constant, lower dielectric loss, and superior performance. Attached Figure Description
[0036] Figure 1 These are XRD patterns of barium tungsten copper oxide high-dielectric ceramic powders prepared in Examples 1-3 of the preparation method of barium tungsten copper oxide high-dielectric ceramic powder with spindle structure of the present invention.
[0037] Figure 2a , Figure 2b , Figure 2c These are SEM images of the barium tungstate high-dielectric ceramic powders prepared in Examples 1, 2, and 3 of this invention;
[0038] Figure 3 These are the XRD patterns of the barium tungsten copper oxide high-dielectric ceramic powders prepared in Examples 3-6 of this invention;
[0039] Figure 4a This is a SEM image of the barium tungsten copper oxide high-dielectric ceramic powder prepared in Example 4 of this invention;
[0040] Figure 4b This is a SEM image of the barium tungsten copper oxide high-dielectric ceramic powder prepared in Example 5 of this invention;
[0041] Figure 4cThis is a SEM image of the barium tungsten copper oxide high-dielectric ceramic powder prepared in Example 3 of this invention;
[0042] Figure 4d This is a SEM image of the barium tungstate high-dielectric ceramic powder prepared in Example 6 of this invention;
[0043] Figure 5a SEM image of barium tungsten copper oxide high-dielectric ceramic powder prepared in Example 4 of this invention;
[0044] Figure 5b This is a SEM image of the barium tungsten copper oxide high-dielectric ceramic powder prepared in Example 5 of this invention;
[0045] Figure 5c This is a SEM image of the barium tungsten copper oxide high-dielectric ceramic powder prepared in Example 3 of this invention;
[0046] Figure 5d This is a SEM image of the barium tungstate high-dielectric ceramic powder prepared in Example 6 of this invention;
[0047] Figure 6a , Figure 6b This is a dielectric property diagram of barium tungstate ceramic materials prepared at different pH values using the method of this invention. Detailed Implementation
[0048] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0049] The present invention relates to a spindle-structured barium tungsten copper oxide high-dielectric ceramic powder. This barium tungsten copper oxide high-dielectric ceramic powder possesses high dielectric properties and a spindle-shaped microstructure with regular shape and uniform particle size. Furthermore, the barium tungsten copper oxide high-dielectric ceramic powder contains no impurity phases and exhibits high dielectric properties at a frequency of 10⁻⁶. 8 Below Hz, the dielectric constant increases with increasing pH value, while the dielectric loss decreases with increasing pH value, resulting in relatively high activity of the synthesized powder.
[0050] The preparation method of the spindle-structured barium tungsten copper oxide high-dielectric ceramic powder of the present invention is specifically implemented according to the following steps:
[0051] Step 1: Prepare precursor powder by mixing ingredients;
[0052] 1) Weigh the raw materials according to the molar ratio of Ba(NO3)2:Cu(NO3)2:ammonium metatungstate of (1.7~2.3):(0.7~1.3):(0.7~1.3), and introduce Ba... 2+ Cu 2+ W 6+The elements were placed in a beaker, and deionized water was added at the same time. The molar ratio of the total amount of the three raw materials, Ba(NO3)2, Cu(NO3)2, and ammonium metatungstate, to the deionized water was (0.8~1.2):(0.8~1.2). The mixture was placed in an oil bath at 60~100℃ for 10~50 minutes to obtain solution A.
[0053] 2) Re-adjust the molar ratio of surfactant to the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2, and ammonium metatungstate to (0.8~1.2):(0.8~1.2); weigh the surfactant and add it to the oil bath, mix it evenly, then weigh an equal amount of deionized water to the surfactant and add it to the oil bath. Keep the oil bath at 60~100℃ for 20~40 minutes to prepare solution B.
[0054] The surfactant is at least one of citric acid and polyethylene glycol, and the molar ratio of citric acid to polyethylene glycol is (0-1.2):(0-1.2).
[0055] 3) Weigh 1 / 3 to 1 / 2 of solution A and slowly add it to solution B at a rate of 20 to 30 drops / minute. Place the solution in an oil bath at 60 to 100°C and stir continuously for 40 to 80 minutes to form precursor sol seeds.
[0056] 4) Pour the remaining solution A into the precursor sol seed from step 3), maintain the oil bath at 60-100°C, and stir constantly for 20-40 minutes.
[0057] 5) Slowly add a 0.01 mol / L ammonia solution dropwise to the product mixture in step 4), react in a water bath at 20–40°C for 12–24 hours, and stir continuously for 60–120 minutes to adjust the pH value so that the seeds grow evenly.
[0058] 6) After the solution in step 5) forms a stable gel, age it at room temperature for 10 to 16 hours, then wash it 3 to 5 times with 50 ml of deionized water, dry it at 80 to 160°C for 12 to 24 hours, and grind it to obtain the precursor powder.
[0059] Step 2: Pre-calcination to obtain pre-calcined powder;
[0060] The precursor powder is placed in an alumina crucible and pre-calcined at 750–1150°C for 2–6 hours. After cooling to room temperature, it is ground with a mortar and pestle to obtain the pre-calcined powder.
[0061] Step 3: Granulation to obtain spherical powder particles;
[0062] Add 5wt% PVA polyvinyl alcohol solution dropwise to the pre-calcined powder in small amounts several times, stir thoroughly, grind finely, dry naturally, and pass through a 120-180 mesh sieve to make spherical powder particles.
[0063] Step 4: Tableting;
[0064] The granulated spherical powder particles are placed in a mold with a diameter of 11.5 mm and pressed into a ceramic green body with a thickness of 1 mm. The pressing pressure is 40 MPa to 80 MPa.
[0065] Step 5: Remove glue;
[0066] The ceramic green body is placed in a muffle furnace and heated to 500-700℃ at a heating rate of 1-3℃ / min, held at that temperature for 1-4 hours, and then naturally cooled to room temperature.
[0067] Step 6: Sintering;
[0068] After the binder is removed, the blank is heated to 1000-1200℃ at a heating rate of 8-12℃ / min, sintered for 12-16 hours, and then cooled naturally to room temperature with the furnace.
[0069] Step 7: Burning silver.
[0070] The sintered ceramic from step 6 is ground, polished, ultrasonically cleaned, and dried. The surface of the sintered ceramic is ground and cleaned with alcohol. A silver paste with a thickness of 0.01 mm to 0.03 mm is coated on both sides of the ceramic surface. The ceramic is then placed in a resistance furnace and calcined at 650℃ to 1000℃ for 8 min to 12 min. After natural cooling to room temperature, barium tungstate copper oxide high dielectric ceramic powder is produced. The sintering temperature is relatively low.
[0071] The present invention discloses a method for preparing barium tungsten copper oxide high-dielectric ceramic powder with a spindle structure. The method employs a gel seeding method and obtains BCW ceramic powders with controllable size and morphology by adjusting the surfactant and pH value. The powder can be sintered into ceramic at relatively low synthesis and sintering temperatures. The synthesized powder has high activity and excellent dielectric properties. This method solves the problems of uneven grain growth, low density, and high porosity in the preparation of barium tungsten copper oxide ceramics by existing solid-state reaction methods, which lead to low performance and poor temperature stability of high-dielectric ceramic materials.
[0072] Example 1
[0073] The spindle-structured barium tungsten copper oxide high-dielectric ceramic powder of the present invention has the molecular formula Ba(Cu) 0.5 W 0.5 O3, the raw materials used and its preparation method are as follows:
[0074] 1. Prepare precursor powder by mixing ingredients;
[0075] (1) Weigh the raw materials according to the molar ratio of Ba(NO3)2:Cu(NO3)2:ammonium metatungstate of 2:1:1, put them into a beaker, and add deionized water in equal amounts according to the total amount of the three raw materials. Heat the mixture in an oil bath at 80°C for 30 minutes to prepare solution A.
[0076] (2) Weigh polyethylene glycol according to the molar ratio of the total amount of polyethylene glycol and the three raw materials Ba(NO3)2, Cu(NO3)2 and ammonium metatungstate being 1:1. Add an equal amount of deionized water to polyethylene glycol and keep the oil bath at 80°C. Stir thoroughly for 30 minutes to prepare solution B.
[0077] (3) Add half of solution A slowly to solution B at a rate of 25 drops / minute, place in an oil bath at 80°C, and stir continuously for 60 minutes to form precursor sol seeds;
[0078] (4) Pour the remaining solution A into solution (3), maintain the oil bath at 80°C, and stir constantly for 30 minutes.
[0079] (5) Slowly add 0.01 mol / L ammonia solution dropwise to the solution in (4), adjust the pH to 8, and stir continuously for 90 min. The reaction temperature is 30℃ in a water bath, and the reaction time is 24 hours to ensure uniform seed growth;
[0080] (6) After the above solution forms a stable gel, it is aged at room temperature for 12 hours, then washed 4 times, dried at 120℃ for 24 hours, and ground to obtain the precursor powder.
[0081] 2. Pre-firing
[0082] The precursor powder placed in an alumina crucible was pre-calcined at 950°C for 4 hours, cooled to room temperature, and ground with a mortar and pestle to obtain the pre-calcined powder.
[0083] 3. Granulation
[0084] After passing through a 20-mesh sieve in step 2, add 5 wt.% PVA in small amounts several times for granulation, stir thoroughly, grind finely, dry naturally, and pass through a 160-mesh sieve to make spherical powder.
[0085] 4. Tableting
[0086] The granulated spherical powder particles are placed into a stainless steel mold with a diameter of 11.5 mm and pressed into a ceramic green body with a thickness of 1 mm using a pressure of 60 MPa.
[0087] 5. Degumming
[0088] A 1mm thick ceramic green body was placed in an alumina sealed sagger and heated to 600℃ at a heating rate of 2℃ / min. The temperature was held for 2 hours and then allowed to cool naturally to room temperature.
[0089] 6. Sintering
[0090] After debinding, the blank is heated to 1160℃ at a heating rate of 10℃ / min and sintered for 15 hours. Then it is cooled naturally to room temperature with the furnace.
[0091] 7. Burning silver
[0092] The sintered ceramic sheets were ground, polished, ultrasonically cleaned with alcohol, dried at 70°C, coated with a 0.02mm thick layer of silver paste on both sides, and calcined in a resistance furnace at 850°C for 10 minutes. After natural cooling to room temperature, barium tungsten copper oxide high-dielectric ceramic powder was produced. The SEM image of the barium tungsten copper oxide high-dielectric ceramic powder is shown below. Figure 2a As shown.
[0093] Example 2
[0094] The difference from Example 1 is as follows:
[0095] In step 1(2), citric acid is weighed according to the molar ratio of citric acid and the three raw materials Ba(NO3)2, Cu(NO3)2 and ammonium metatungstate in a 1:1 ratio. It is then added to an equal amount of deionized water and kept in an oil bath at 80°C. The mixture is stirred thoroughly for 30 minutes to prepare solution B.
[0096] The other steps are the same as in Example 1, to prepare barium tungstate copper oxide high-dielectric ceramic powder. The SEM image of the barium tungstate copper oxide high-dielectric ceramic powder is shown below. Figure 2b As shown.
[0097] Example 3
[0098] The difference from Example 1 is as follows:
[0099] In step 1(2), polyethylene glycol and citric acid are weighed according to the molar ratio of the total amount of polyethylene glycol and citric acid to the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2 and ammonium metatungstate, which is 1:1. The molar ratio of polyethylene glycol and citric acid is 1:1. Deionized water of the same amount as the total amount of polyethylene glycol and citric acid is added to maintain the oil bath at 80°C and the mixture is stirred for 30 minutes to prepare a 0.001 mol / L citric acid and polyethylene glycol mixed solution B.
[0100] The other steps are the same as in Example 1, to prepare barium tungsten copper oxide high-dielectric ceramic powder. The SEM image of the barium tungsten copper oxide high-dielectric ceramic powder is shown below. Figure 2c As shown.
[0101] Example 4
[0102] The preparation method of the spindle-structured barium tungsten copper oxide high-dielectric ceramic powder of the present invention comprises the following steps:
[0103] 1. Prepare precursor powder by mixing ingredients;
[0104] (1) Weigh the raw materials according to the molar ratio of Ba(NO3)2:Cu(NO3)2:ammonium metatungstate of 2.3:0.7:0.7, put them into a beaker, and add deionized water in equal amounts according to the total amount of the three raw materials. Heat the oil bath at 100°C for 10 minutes to prepare solution A.
[0105] (2) Weigh polyethylene glycol and citric acid according to the molar ratio of the total amount of polyethylene glycol and citric acid to the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2 and ammonium metatungstate, which is 1.2:0.8. The molar ratio of polyethylene glycol and citric acid is 1:1. Add an equal amount of deionized water to maintain the oil bath at 100°C and stir thoroughly for 20 minutes to prepare solution B.
[0106] (3) Add 1 / 3 of solution A slowly to solution B at a rate of 20 drops / minute, place in an oil bath at 100°C, and stir continuously for 40 minutes to form precursor sol seeds;
[0107] (4) Pour the remaining solution A into solution (3), keep the oil bath at 100°C and stir constantly for 20 minutes.
[0108] (5) Slowly add 0.01 mol / L ammonia solution dropwise to the solution in (4), adjust the pH to 2, and stir continuously for 60 min. The reaction temperature is 40℃ in a water bath, and the reaction time is 12 hours to ensure uniform seed growth;
[0109] (6) After the above solution forms a stable gel, it is aged at room temperature for 16 hours, then washed 3 times, dried at 160℃ for 12 hours, and ground to obtain the precursor powder.
[0110] 2. Pre-firing
[0111] The precursor powder placed in an alumina crucible was pre-calcined at 1150°C for 2 hours, cooled to room temperature, and ground with a mortar and pestle to obtain the pre-calcined powder.
[0112] 3. Granulation
[0113] After passing through a 20-mesh sieve in step 2, add 5wt% PVA in small amounts several times for granulation, stir thoroughly, grind finely, dry naturally, and pass through a 180-mesh sieve to make spherical powder.
[0114] 4. Tableting
[0115] The granulated spherical powder particles are placed into a stainless steel mold with a diameter of 11.5 mm and pressed into a ceramic green body with a thickness of 1 mm using a pressure of 80 MPa.
[0116] 5. Degumming
[0117] A 1mm round ceramic green body was placed in an alumina sealed sagger and heated to 500℃ at a rate of 1℃ / min. The temperature was held for 4 hours and then allowed to cool naturally to room temperature.
[0118] 6. Sintering
[0119] After debinding, the blank is heated to 1000℃ at a heating rate of 8℃ / min and sintered for 16 hours. Then it is cooled naturally to room temperature with the furnace.
[0120] 7. Burning silver
[0121] The sintered ceramic sheets are ground, polished, ultrasonically cleaned with alcohol, dried at 70°C, coated with silver paste with a thickness of 0.03mm on both sides, placed in a resistance furnace and calcined at 650°C for 12 minutes, and then naturally cooled to room temperature to produce barium tungstate high dielectric ceramic powder.
[0122] Example 5
[0123] The preparation method of the spindle-structured barium tungsten copper oxide high-dielectric ceramic powder of the present invention comprises the following steps:
[0124] 1. Prepare precursor powder by mixing ingredients;
[0125] (1) Weigh the raw materials according to the molar ratio of Ba(NO3)2:Cu(NO3)2:ammonium metatungstate of 1.7:1.3:1.3, put them into a beaker, and add deionized water in equal amounts according to the total amount of the three raw materials. Heat the mixture in an oil bath at 60°C for 50 minutes to prepare solution A.
[0126] (2) Weigh polyethylene glycol and citric acid according to the molar ratio of the total amount of polyethylene glycol and citric acid to the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2 and ammonium metatungstate, which is 0.8:1.2. The molar ratio of polyethylene glycol and citric acid is 1:1. Add an equal amount of deionized water and keep the oil bath at 60°C. Stir thoroughly for 40 minutes to prepare solution B.
[0127] (3) Add 1 / 3 of solution A slowly to solution B at a rate of 30 drops / minute, place in an oil bath at 60°C, and stir continuously for 40 minutes to form precursor sol seeds;
[0128] (4) Pour the remaining solution A into solution (3), keep the oil bath at 60°C and stir constantly for 80 minutes;
[0129] (5) Slowly add 0.01 mol / L ammonia solution dropwise to the solution in (4), adjust the pH to 6, and stir continuously for 120 min. The reaction temperature is 20℃ in a water bath, and the reaction time is 18 hours to ensure uniform seed growth;
[0130] (6) After the above solution forms a stable gel, it is aged at room temperature for 10 hours, then washed 5 times, dried at 80°C for 18 hours, and ground to obtain the precursor powder.
[0131] 2. Pre-firing
[0132] The precursor powder placed in an alumina crucible was pre-calcined at 750°C for 6 hours, cooled to room temperature, and ground with a mortar and pestle to obtain the pre-calcined powder.
[0133] 3. Granulation
[0134] After passing through a 20-mesh sieve in step 2, add 5wt% PVA in small amounts several times for granulation, stir thoroughly, grind finely, dry naturally, and pass through a 120-mesh sieve to make spherical powder.
[0135] 4. Tableting
[0136] The granulated spherical powder particles are placed into a stainless steel mold with a diameter of 11.5 mm and pressed into a ceramic green body with a thickness of 1 mm using a pressure of 40 MPa.
[0137] 5. Degumming
[0138] A 1mm round ceramic green body was placed in an alumina sealed sagger and heated to 700℃ at a heating rate of 3℃ / min. It was held at that temperature for 1 hour and then allowed to cool naturally to room temperature.
[0139] 6. Sintering
[0140] After debinding, the blank is heated to 1200℃ at a heating rate of 12℃ / min and sintered for 12 hours. Then it is cooled naturally to room temperature with the furnace.
[0141] 7. Burning silver
[0142] The sintered ceramic sheets are ground, polished, ultrasonically cleaned with alcohol, dried at 70°C, coated with silver paste with a thickness of 0.01 on both sides, placed in a resistance furnace and calcined at 1000°C for 8 minutes, and then naturally cooled to room temperature to produce barium tungstate high dielectric ceramic powder.
[0143] Example 6
[0144] The difference from Example 4 is as follows:
[0145] In step 1 (5) of this embodiment, a 0.01 mol / L ammonia solution is slowly added dropwise to the solution in (4) to adjust the pH to 10, while continuously stirring. The reaction temperature is 30°C in a water bath, and the reaction time is 24 hours to ensure uniform seed growth.
[0146] The other steps are the same as in Example 4, and barium tungstate high dielectric ceramic powder is prepared.
[0147] Figure 1 These are the XRD patterns of the barium tungsten copper oxide high-dielectric ceramic powders prepared in Examples 1-3. It can be seen that a pure perovskite-like structure was obtained in all cases, with no impurity second phase present. From... Figure 2a , Figure 2b , Figure 2c It can be seen that after pre-firing the ceramic precursor powders in Examples 1-3, barium tungsten copper oxide powders with different morphologies can be obtained, most of which exhibit a spindle-shaped morphology. In Example 3, the surfactant was introduced by the combined use of polyethylene glycol and citric acid, resulting in a more regular morphology. The SEM images of the prepared barium tungsten copper oxide high-dielectric ceramic powder are shown below. Figure 2c As shown, small and uniform spindle fibers aggregate to form a tree-like structure.
[0148] In Example 3, the pH value was 8; in Example 4, the pH value was 2; in Example 5, the pH value was 6; and in Example 6, the pH value was 10. SEM images of the barium tungsten copper oxide high-dielectric ceramic powders prepared in Examples 3-6 are shown below. Figure 4a , Figure 4b , Figure 4c , Figure 4d As shown, it can be seen that with the gradual increase of pH value, the microstructure of barium tungstate copper exhibits an increasingly obvious spindle-shaped morphology, and the ceramic powder particles show a trend of increasing size. From Figure 5a , Figure 5b , Figure 5c , Figure 5d It can be seen that the ceramic samples obtained at different pH values all exhibited no pores and had relatively high density. From... Figure 6a and Figure 6b It is evident that the ceramic materials prepared in Examples 3-6 all exhibit high dielectric properties at room temperature. Figure 6a It can be seen that at a frequency of 10 8 Below Hz, the dielectric constant increases with increasing pH value, from Figure 6b It can be seen that at a frequency of 10 8 Below Hz, dielectric loss decreases as pH increases.
Claims
1. A method for preparing barium tungstate copper oxide high-dielectric ceramics, characterized in that, The specific steps are as follows: Step 1: Prepare precursor powder by mixing ingredients; Step 2: Pre-calcination to obtain pre-calcined powder; Step 3: Granulation to obtain spherical powder particles; Step 4: Tableting; Step 5: Remove glue; Step 6: Sintering; Step 7: Burning silver; The pre-calcined powder has the molecular formula Ba(Cu) 0.5 W 0.5 O3 has high dielectric properties and a spindle-shaped microstructure. The barium tungstate copper oxide high-dielectric ceramic contains no impurity phases and exhibits high dielectric constant at a frequency of 10. 8 Below Hz, the dielectric constant increases with increasing pH value, while the dielectric loss decreases with increasing pH value; Step 1 specifically includes: Step 1.1 Weigh the raw materials according to the molar ratio of Ba(NO3)2:Cu(NO3)2:ammonium metatungstate of 1.7~2.3:0.7~1.3:0.7~1.3, and introduce them into a beaker. At the same time, add deionized water. The molar ratio of the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2, and ammonium metatungstate to deionized water is 0.8~1.2:0.8~1.
2. Heat the solution in an oil bath at 60℃~100℃ for 10min~50min to obtain solution A. Step 1.2: Weigh equal amounts of surfactant and deionized water into an oil bath and maintain the oil bath at 60℃~100℃. Stir thoroughly for 20min~40min to prepare solution B. The surfactant is at least one of citric acid and polyethylene glycol; Step 1.3: Weigh 1 / 3 to 1 / 2 of solution A and add it dropwise to solution B. Place the solution in an oil bath at 60℃ to 100℃ and stir continuously for 40 to 80 minutes to form precursor sol seeds. Step 1.4: Pour the remaining solution A into the oil bath from Step 1.3, maintain the oil bath at 60-100°C, and stir constantly for 20-40 minutes. Step 1.5: Add 0.01 mol / L ammonia solution dropwise to the product mixture solution from Step 1.4 and stir for 60 min to 120 min. Adjust the pH value to 2-10 to ensure uniform seed growth. Step 1.6: After the solution in Step 1.5 forms a stable gel, age it at room temperature for 10-16 hours, then wash it 3-5 times with deionized water, dry it at 80-160℃ for 12-24 hours, and grind it to obtain the precursor powder.
2. The method for preparing barium tungsten copper oxide high-dielectric ceramic according to claim 1, characterized in that, In step 1.2, the molar ratio of the surfactant to the total amount of the three raw materials Ba(NO3)2, Cu(NO3)2, and ammonium metatungstate is 0.8~1.2:0.8~1.2; the molar ratio of citric acid to polyethylene glycol is 0~1.2:0~1.
2.
3. The method for preparing barium tungsten copper oxide high-dielectric ceramic according to claim 1, characterized in that, In step 1.5, the reaction temperature is 20℃~40℃ in a water bath, and the reaction time is 12h~24h.
4. The method for preparing barium tungstate copper oxide high-dielectric ceramic according to claim 1, characterized in that, Step 2 specifically involves placing the precursor powder in an alumina crucible, pre-calcining it at 750℃~1150℃ for 2~6 hours, cooling it to room temperature, and grinding it with a mortar and pestle to obtain the pre-calcined powder.
5. The method for preparing barium tungsten copper oxide high-dielectric ceramic according to claim 1, characterized in that, Step 3 specifically involves adding a 5wt% PVA polyvinyl alcohol solution dropwise to the pre-calcined powder, stirring thoroughly, grinding finely, drying naturally, and passing it through a 120-180 mesh sieve to form spherical powder particles.
6. The method for preparing barium tungsten copper oxide high-dielectric ceramic according to claim 1, characterized in that, Step 4 specifically involves placing the granulated spherical powder particles into a mold and pressing them into ceramic green bodies under a pressure of 40 MPa to 80 MPa. Step 5 specifically involves placing the ceramic green body in a muffle furnace, heating it to 500-700°C at a heating rate of 1-3°C / min, holding it at that temperature for 1-4 hours, and then allowing it to cool naturally to room temperature.
7. The method for preparing barium tungsten copper oxide high-dielectric ceramic according to claim 1, characterized in that, Step 6 specifically involves heating the blank after debinding to 1000-1200℃ at a heating rate of 8-12℃ / min, sintering for 12-16 hours, and then cooling it naturally to room temperature with the furnace. Step 7 specifically involves grinding, polishing, ultrasonically cleaning, and drying the sintered ceramic from step 6, coating both sides of the ceramic surface with a silver paste thickness of 0.01mm to 0.03mm, placing it in a resistance furnace, calcining it at 650℃ to 1000℃ for 8 to 12 minutes, and then naturally cooling it to room temperature to produce barium tungstate high-dielectric ceramic powder.