A nano-barium calcium carbonate solid solution, its preparation method and application

Abstract

This invention provides a nano-barium calcium carbonate solid solution, its preparation method, and its application, comprising the following steps: A) mixing and dissolving an alkaline soluble barium source and an alkaline soluble calcium source in water to obtain a mixed solution; the molar ratio of Ba element in the alkaline soluble barium source to calcium element in the alkaline soluble calcium salt is (1-X):X, 0<X≤0.15; B) rapidly mixing the mixed solution with carbon dioxide in a gas-liquid mixer to generate a barium calcium carbonate slurry; C) performing solid-liquid separation on the barium calcium carbonate slurry, followed by spray drying to obtain nano-barium calcium carbonate. This invention firstly obtains a barium calcium carbonate solid solution by controlling the process conditions in the preparation method, and solves the problem of (Ba) calcium carbonate solid solution being affected by the addition of a small amount of CaCO3. 1‑x Ca x The defect of uneven Ca composition in mTiO3.

Description

Technical Field

[0001] This invention belongs to the field of capacitor material preparation technology, and particularly relates to a nano-barium calcium carbonate solid solution, its preparation method and its application in dielectric material preparation. Background Technology

[0002] Currently, the primary dielectric material for MLCC capacitors is barium titanate. MLCCs consist of a dielectric layer, inner electrode, and outer electrode. The inner electrode is made of nickel. To prevent oxidation of the nickel electrode during MLCC firing, manufacturers must fire the MLCC in a reducing atmosphere. When barium titanate is sintered in a hydrogen atmosphere, oxygen vacancies easily form, leading to lower insulation resistance and reduced reliability. Although rare-earth-doped core-shell barium titanate has been developed, the core remains barium titanate, making it a site with many oxygen vacancies during sintering. Calcium barium titanate, however, with calcium ion doping, suppresses oxygen vacancy formation, significantly improving reduction resistance, insulation resistance, and MLCC reliability. While calcium barium titanate greatly improves MLCC reliability, its lower dielectric constant necessitates a thinner dielectric layer to achieve the same capacitance. Therefore, high uniformity is required for calcium barium titanate, including both compositional and dimensional uniformity. Compositional uniformity primarily refers to the uniformity of composition between individual particles and between different particles.

[0003] Currently, barium calcium titanate products are mainly synthesized via solid-state methods, using nano-barium carbonate, calcium carbonate, and titanium dioxide as raw materials. The process involves uniform mixing or sand milling followed by calcination to prepare barium calcium titanate. As mentioned above, the most important aspect of the solid-state method is to disperse TiO2, CaCO3, and BaCO3 powders as uniformly as possible. To achieve uniform dispersion of TiO2, CaCO3, and BaCO3 powders, raw materials with a large specific surface area or dispersion media with good dispersibility are typically used. However, achieving uniform mixing of (Ca / Ba) 5% mol or even less CaCO3 and BaCO3 is more challenging, as achieving microscopic compositional uniformity is difficult. Summary of the Invention

[0004] The purpose of this invention is to provide a nano-barium calcium carbonate solid solution, its preparation method and application. The nano-barium calcium carbonate solid solution of this invention can ensure that the prepared barium calcium titanate dielectric material has good compositional uniformity.

[0005] This invention provides a method for preparing nano-barium calcium carbonate solid solution, comprising the following steps:

[0006] A) Mix and dissolve an alkaline soluble barium source and an alkaline soluble calcium source in water to obtain a mixed solution;

[0007] The molar ratio of Ba in the alkaline soluble barium source to calcium in the alkaline soluble calcium salt is (1-X):X, 0<X≤0.15;

[0008] B) The mixed solution is rapidly mixed with carbon dioxide in a gas-liquid mixer to generate barium calcium carbonate slurry;

[0009] C) The barium calcium carbonate slurry is subjected to solid-liquid separation and then spray-dried to obtain nano-barium calcium carbonate.

[0010] Preferably, the alkaline soluble barium source is barium hydroxide, and the alkaline soluble calcium source is calcium hydroxide and / or calcium oxide.

[0011] Preferably, the mass concentration of the alkaline soluble barium source in the mixed solution is ≤8%, and the mass concentration of the alkaline soluble calcium source is ≤0.18%.

[0012] Preferably, the dissolution temperature in step A) is 0–40°C.

[0013] Preferably, the pressure of carbon dioxide in step B) is 0.2 to 1.0 MPa.

[0014] Preferably, in the rapid mixing reaction, the flow rate of carbon dioxide gas is 5 to 40 times that of the liquid flow rate.

[0015] This invention provides a nano-barium calcium carbonate solid solution prepared by the preparation method described above.

[0016] Preferably, the nano-barium calcium carbonate solid solution uses a barite (BaCO3) structure as the matrix and Ca ions as dopant, with the chemical formula (Ba... 1-x Ca x CO3, where X is the solid concentration of Ca, 0 < X ​​≤ 0.15, and the specific surface area is 10–50 m². 2 / g, the particles are short rod-shaped or needle-shaped.

[0017] This invention provides the application of the nano-barium calcium carbonate solid solution as described above in the preparation of dielectric materials.

[0018] This invention provides a barium calcium titanate powder, which is prepared by solid-phase sintering of the nano-barium calcium carbonate solid solution and a titanium source as described above. The barium calcium titanate powder particles have uniform barium and calcium composition, and the barium and calcium composition between particles is also uniform.

[0019] This invention provides a method for preparing nano-barium calcium carbonate solid solution, comprising the following steps: A) mixing and dissolving an alkaline soluble barium source and an alkaline soluble calcium source in water to obtain a mixed solution; the molar ratio of Ba element in the alkaline soluble barium source to calcium element in the alkaline soluble calcium salt is (1-X):X, 0<X≤0.15; B) rapidly mixing the mixed solution with carbon dioxide in a gas-liquid mixer to generate barium calcium carbonate slurry; C) performing solid-liquid separation on the barium calcium carbonate slurry, followed by spray drying to obtain nano-barium calcium carbonate. This invention firstly obtains barium calcium carbonate solid solution by controlling the process conditions in the preparation method, and solves the problem of (Ba) calcium carbonate solid solution being affected by the addition of a small amount of CaCO3. 1-x Ca x The defect of uneven Ca composition in mTiO3. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating the preparation process of the nano-barium calcium carbonate solid solution in an embodiment of the present invention.

[0022] Figure 2 This is a flowchart illustrating the preparation process of barium calcium titanate in the embodiments of the invention.

[0023] Figure 3 The XRD patterns of the nano-barium calcium carbonate prepared in Examples 1-4 and Comparative Examples 1-2 of this invention are shown.

[0024] Figure 4 The XRD patterns of the nano-barium calcium carbonate prepared in Example 2 and Comparative Example 3 of this invention are shown.

[0025] Figure 5 This is a SEM image of the nano-barium calcium carbonate solid solution prepared in Example 1 of this invention;

[0026] Figure 6 This is a SEM image of the nano-barium calcium carbonate solid solution prepared in Example 2 of this invention;

[0027] Figure 7 This is a SEM image of the nano-barium calcium carbonate solid solution prepared in Example 3 of this invention;

[0028] Figure 8This is a SEM image of the nano-barium calcium carbonate solid solution prepared in Example 4 of this invention;

[0029] Figure 9 This is a SEM image of barium carbonate prepared in Comparative Example 1 of the present invention.

[0030] Figure 10 This is a SEM image of the barium calcium carbonate prepared in Comparative Example 2 of the present invention.

[0031] Figure 11 This is a SEM image of the barium calcium carbonate prepared in Comparative Example 3 of the present invention.

[0032] Figure 12 This is a surface scan diagram of the composition of the product prepared in Comparative Example 4 of the present invention.

[0033] Figure 13 This is a surface scan image of the product prepared in Example 5 of the present invention.

[0034] Figure 14 This is a SEM image of the barium calcium titanate prepared in Example 5 of the present invention;

[0035] Figure 15 This is a SEM image of the barium calcium titanate prepared in Example 6 of the present invention;

[0036] Figure 16 This is a SEM image of the barium calcium titanate prepared in Comparative Example 4 of this invention. Detailed Implementation

[0037] This invention provides a method for preparing nano-barium calcium carbonate solid solution, comprising the following steps:

[0038] A) Mix and dissolve an alkaline soluble barium source and an alkaline soluble calcium source in water to obtain a mixed solution;

[0039] The molar ratio of Ba in the alkaline soluble barium source to calcium in the alkaline soluble calcium salt is (1-X):X, 0<X≤0.15;

[0040] B) The mixed solution is rapidly mixed with carbon dioxide in a gas-liquid mixer to generate barium calcium carbonate slurry;

[0041] C) The barium calcium carbonate slurry is subjected to solid-liquid separation and then spray-dried to obtain nano-barium calcium carbonate.

[0042] See Figure 1 The present invention first mixes and dissolves an alkaline soluble barium source and an alkaline soluble calcium source in water to obtain a mixed solution.

[0043] In this invention, the alkaline soluble barium source is barium hydroxide, and the alkaline soluble calcium source is calcium hydroxide and / or calcium oxide. The molar ratio of Ba element in the alkaline soluble barium source to calcium element in the alkaline soluble calcium salt is (1-X):X, 0<X≤0.15. If the calcium content is too high, other phases such as BaCa(CO3)2 will be generated, resulting in uneven composition.

[0044] In this invention, 0.05≤X≤0.15, such as x being 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0045] In the mixed solution, the mass concentration of the alkaline soluble barium source is ≤8%, preferably ≤7%, more preferably ≤6%, and the mass concentration of the alkaline soluble calcium source is ≤0.18%, preferably ≤0.15%, more preferably ≤0.1%. In this invention, it is necessary to balance the dissolution concentrations of the barium source and the calcium source to ensure that the barium and calcium are fully dissolved while their molar ratio is between 0% and 15%.

[0046] After obtaining the mixed solution, this invention uses a gas-liquid mixer to rapidly mix and react the mixed solution with high-pressure carbon dioxide to generate barium calcium carbonate slurry. If a conventional slow synthesis method, such as carbon dioxide bubbling, is used to introduce carbon dioxide, larger particles can be easily generated.

[0047] In this invention, the pressure of the carbon dioxide is preferably 0.2 to 1.0 MPa, more preferably 0.4 to 0.6 MPa, such as 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, and preferably within the range of any of the above values ​​as the upper or lower limit; the flow rate of the carbon dioxide is preferably 5 to 40 times the liquid flow rate, more preferably 10 to 25 times.

[0048] After the above reaction is completed, the present invention uses a gas-liquid separator and a filter device to perform solid-liquid separation on the generated barium calcium carbonate slurry to obtain barium calcium carbonate and water.

[0049] In this invention, the above-mentioned solid-liquid separation is a commonly used separation method, such as vacuum filtration, which will not be described in detail here.

[0050] After solid-liquid separation, the solid content of the obtained product is between 8% and 15%. The present invention preferably uses spray drying to dry it.

[0051] The present invention does not impose any special limitations on the process conditions of spray drying, and commonly used spray drying methods can be used.

[0052] This invention also provides a nano-barium calcium carbonate solid solution, wherein calcium and barium exist in the form of a solid solution, rather than a mixture of calcium and barium salts. The nano-barium calcium carbonate solid solution uses a barite BaCO3 structure as a matrix and is doped with Ca ions, with the chemical formula (Ba... 1-x Ca x CO3, where X is the solid concentration of Ca, 0 < X ​​≤ 0.15, and the specific surface area is 10–50 m². 2 / g, the particles are short rod-shaped or needle-shaped. The lattice constants a and c axes of the solid solution decrease with increasing Ca doping concentration, and the cell volume also decreases with increasing Ca doping concentration.

[0053] This invention provides the application of nano-barium calcium carbonate solid solution in the preparation of dielectric materials, wherein the dielectric material is barium calcium titanate with the chemical formula (Ba... 1-x Ca x mTiO3 is prepared by solid-phase sintering of barium calcium carbonate solid solution and titanium dioxide as described above.

[0054] In this invention, X is the same as X in the nano-barium calcium carbonate solid solution mentioned above, and m is preferably 0.990 to 1.015, more preferably 0.995 to 1.010, such as 0.990, 0.995, 1.000, 1.005, 1.010, 1.015, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0055] This invention also provides the dielectric material described above and its preparation method, namely, solid-state sintering method, see [link to relevant documentation]. Figure 2 .

[0056] Existing technologies use three raw materials: TiO2, CaCO3, and BaCO3. CaCO3 and BaCO3 are added separately, leading to microscopic inhomogeneity of the CaCO3 and BaCO3 particles during sand milling. Furthermore, differences in particle size distribution may exist when selecting materials, resulting in uneven composition between particles during the synthesis of nano-barium calcium titanate. This leads to variations in reduction resistance among particles, affecting product reliability. The different distributions of CaCO3 and BaCO3 make it difficult to homogenize the powder particles during calcination, resulting in different grain growth temperatures for each component and preferential growth of certain components, thus widening the particle size distribution of the product.

[0057] This invention prepares a nano-barium calcium carbonate solid solution and then uses a solid-state sintering method with titanium dioxide to obtain a barium calcium titanate dielectric material, thereby solving the problem of (Ba) dielectric material caused by the addition of a small amount of CaCO3. 1-x Ca x The problem of uneven Ca composition in mTiO3.

[0058] In this invention, titanium dioxide and the nano-barium calcium carbonate solid solution prepared above are mixed with deionized water and ground with a grinding ball to obtain a slurry. The grinding should be carried out to disperse and mix the raw materials as much as possible to ensure uniform mixing.

[0059] In this invention, the titanium dioxide is preferably nano-titanium dioxide powder, and the specific surface area is preferably ≥15m². 2 / g, with the crystal form as uniform as possible. The smaller the particle size, the more it helps in mixing the raw materials and reducing the firing temperature.

[0060] In this invention, the grinding speed is preferably 5 to 15 m / s; the diameter of the grinding ball is preferably 0.1 to 0.3 mm.

[0061] After obtaining the ground slurry, the present invention dries the slurry, preferably by a rapid drying method, such as spray drying, fluidized bed drying, or disc drying.

[0062] The present invention preferably involves calcining the dried powder. The calcination can be carried out using conventional calcination methods, but the reaction atmosphere should ensure that CO2 is fully discharged during the reaction process. Specifically, methods such as vacuuming and gas replacement can be used.

[0063] In this invention, the firing temperature is preferably 900-1050°C, more preferably 950-980°C, and the firing holding time is preferably 1-2 hours.

[0064] The method for preparing barium calcium titanate dielectric materials using nano-barium calcium carbonate solid solution in this invention can prepare barium calcium titanate powder with a particle size of 100 nm or larger. For barium calcium titanate with a particle size of less than 300 nm, the effect of this invention on compositional uniformity is particularly outstanding. This is because products with small particle sizes require lower firing temperatures and shorter firing times. At lower temperatures, the diffusion of Ba and Ca ions is slower. If conventional raw materials such as TiO2, CaCO3, and BaCO3 are used for conventional firing, the compositional inhomogeneity will be particularly obvious. However, in this invention, the (Ba... 1-x Ca x CO3 breaks down this barrier, allowing for a more uniform distribution of Ba and Ca ions in small-particle barium calcium titanate, no longer limited by firing temperature or particle size.

[0065] This invention provides a method for preparing nano-barium calcium carbonate solid solution, comprising the following steps: A) mixing and dissolving a soluble barium source and a soluble calcium source in water to obtain a mixed solution; the molar ratio of Ba element in the soluble barium source to calcium element in the soluble calcium salt is (1-X):X, 0<X≤0.15; B) rapidly mixing the mixed solution with carbon dioxide in a gas-liquid mixer to generate a barium calcium carbonate slurry; C) performing solid-liquid separation on the barium calcium carbonate slurry, followed by spray drying to obtain nano-barium calcium carbonate. This invention firstly obtains a barium calcium carbonate solid solution by controlling the process conditions in the preparation method, and solves the problem of (Ba) content being reduced due to the addition of a small amount of CaCO3 in the preparation of the barium calcium carbonate solid solution. 1- x Ca x The defect of uneven Ca composition in mTiO3.

[0066] To further illustrate the present invention, the following detailed description of a nano-barium calcium carbonate solid solution, its preparation method, and its application is provided in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0067] Example 1

[0068] (1) Weigh 982.4 g of Ba(OH)2·8H2O powder and 3.6 g of CaO powder in a mol ratio of 3.11:0.06. Weigh 20 kg of deionized water and control the water temperature at 30±2℃. Add the weighed Ba(OH)2·8H2O powder and CaO powder to the deionized water and stir in a sealed container for 30 min until completely dissolved.

[0069] (2) The mixed solution from step (1) is rapidly mixed with carbon dioxide at 0.4 MPa in a gas-liquid mixer at a gas-liquid flow rate ratio of 15:1. The pH of the solution after the mixing reaction is 8, and barium calcium carbonate is generated after the reaction is complete.

[0070] (3) The slurry after the reaction in step (2) is filtered until the solid content is 10%, and then spray-dried to obtain barium calcium carbonate solid solution powder.

[0071] (4) The powder from step (3) was subjected to XRD, XRF, specific surface area, and SEM tests. The results were as follows:

[0072] Example 2

[0073] (1) Weigh 1015.8 g of Ba(OH)2·8H2O powder and 9.6 g of CaO powder in a mol ratio of 3.22:0.17. Weigh 20 kg of deionized water and control the water temperature at 30±2℃. Add the weighed Ba(OH)2·8H2O powder and CaO powder to the deionized water and stir in a sealed container for 30 min until completely dissolved.

[0074] (2) The mixed solution from step (1) is rapidly mixed with carbon dioxide at 0.4 MPa in a gas-liquid mixer at a gas-liquid flow rate ratio of 15:1. The pH of the solution after the mixing reaction is 8, and barium calcium carbonate is generated after the reaction is complete.

[0075] (3) The slurry after the reaction in step (2) is filtered until the solid content is 10%, and then spray-dried to obtain barium calcium carbonate solid solution powder.

[0076] (4) The powder from step (3) was subjected to XRD, XRF, specific surface area, and SEM tests. The results were as follows:

[0077] Example 3

[0078] (1) Weigh 250.6 g of Ba(OH)₂·8H₂O powder and 5.0 g of CaO powder in a mol ratio of 0.79:0.09. Weigh 10 kg of deionized water and control the water temperature at 30±2℃. Add the weighed Ba(OH)₂·8H₂O powder and CaO powder to the deionized water and stir in a sealed container for 30 min until completely dissolved.

[0079] (2) The mixed solution from step (1) is rapidly mixed with carbon dioxide at 0.6 MPa in a gas-liquid mixer at a gas-liquid flow rate ratio of 25:1. The pH of the solution after the mixing reaction is 8, and barium calcium carbonate is generated after the reaction is complete.

[0080] (3) The slurry after the reaction in step (2) is filtered until the solid content is 10%, and then spray-dried to obtain barium calcium carbonate solid solution powder.

[0081] (4) The powder from step (3) was subjected to XRD, XRF, specific surface area, and SEM tests. The results were as follows:

[0082] Example 4

[0083] (1) Weigh 220.9 g of Ba(OH)₂·8H₂O powder and 7.0 g of CaO powder respectively in a mol ratio of 0.700:0.124. Weigh 10 kg of deionized water and control the water temperature at 30±2℃. Add the weighed Ba(OH)₂·8H₂O powder and CaO powder to the deionized water and stir in a sealed container for 30 min until completely dissolved.

[0084] (2) The mixed solution from step (1) is rapidly mixed with carbon dioxide at 0.4 MPa in a gas-liquid mixer at a gas-liquid flow rate ratio of 15:1. The pH of the solution after the mixing reaction is 8, and barium calcium carbonate is generated after the reaction is complete.

[0085] (3) The slurry after the reaction in step (2) is filtered until the solid content is 10%, and then spray-dried to obtain barium calcium carbonate solid solution powder.

[0086] (4) The powder from step (3) was subjected to XRD, XRF, specific surface area, and SEM tests. The results were as follows:

[0087] Comparative Example 1

[0088] (1) Weigh 500g of Ba(OH)2·8H2O powder and 10kg of deionized water, keeping the water temperature at 30±2℃. Add the weighed Ba(OH)2·8H2O powder into the deionized water and stir in a sealed container for 30min until completely dissolved.

[0089] (2) The mixed solution from step (1) is rapidly mixed with carbon dioxide at 0.4 MPa in a gas-liquid mixer at a gas-liquid flow rate ratio of 15:1. The pH of the solution after the mixing reaction is 8, and barium carbonate is generated after the reaction is complete.

[0090] (3) The slurry after the reaction in step (2) is filtered until the solid content is 10%, and then spray-dried to obtain barium carbonate powder.

[0091] (4) The powder from step (3) was subjected to XRD, XRF, specific surface area and SEM tests.

[0092] Comparative Example 2

[0093] The preparation was carried out according to the method of Example 1, except that Ba(OH)2·8H2O powder and CaO powder were weighed at a mol ratio of 311.818 with a calcium content of 20%.

[0094] The powder obtained in Comparative Example 2 was subjected to XRD, XRF, specific surface area, and SEM tests.

[0095] Comparative Example 3

[0096] The preparation was carried out according to the method of Example 3, except that carbon dioxide was introduced in step (2) using a conventional bubbling method. The bubbling flow rate was 2 L / min until the pH of the mixed reaction solution was 8, indicating that the reaction was complete and barium carbonate was formed. The remaining steps were the same as in Example 3.

[0097] The test results of the barium calcium carbonate powders obtained in Examples 1-4 and Comparative Example 1 are summarized as follows:

[0098] As can be seen from the results in Table 1, the lattice constant and cell volume gradually decrease with increasing calcium content during the reaction. This is because the radius of calcium ions is smaller than that of barium ions; when calcium ions replace barium ions to form a solid solution, the lattice undergoes distortion and contraction. Figure 3 It can also be seen that the addition of calcium did not form a second phase, but rather entered the crystal lattice in the form of a solid solution. The addition of calcium caused the diffraction peaks to shift to higher angles. From Figures 4-7 It can be seen that the barium calcium carbonate solid solution consists of needle-shaped or short rod-shaped nanoparticles with a short axis diameter of about 20-60 nm.

[0099] Table 1. Detection results of barium calcium carbonate

[0100]

[0101] As can be seen from Table 1 and the SEM images, both the bubbling method and the fast reaction method, which use completely dissolved barium and calcium sources and have a slower reaction rate, result in a reduction in the unit cell volume during synthesis and can both form solid solutions. However, the particles prepared by the bubbling method are relatively coarse.

[0102] The XRD pattern revealed that when the Ca content reached 20% mol, a second phase (BaCa)CO3 appeared in the XRD, resulting in uneven composition.

[0103] Example 5: Preparation of barium calcium titanate

[0104] (1) The nano-barium calcium carbonate powder from Example 2 was mixed with a specific surface area of ​​30m³. 2 / g nano titanium dioxide powder, according to (Ba 1-x Ca x ) m Weigh the TiO3 molar ratio, m = 1.005. Mix the weighed powder with deionized water to make the solid content 50%, and add 2% of the powder content of dispersant. Stir and slurry for 10 minutes.

[0105] (2) The slurry from step (1) is placed in a vertical sand mill for grinding. The grinding balls are 0.3mm zirconia balls, the linear speed is 6m / s, and the grinding time is 120min.

[0106] (3) Dry the slurry ground in step (2) at 150°C and then mechanically crush it.

[0107] (4) The powder from step (3) was calcined at 950°C in a ventilated muffle furnace with a heating rate controlled at 10°C / min and a holding time of 4 hours in the high-temperature section. The calcined powder was then simply dispersed and subjected to XRD, XRF, specific surface area, and SEM tests.

[0108] Example 6: Preparation of barium calcium titanate

[0109] (1) The nano-barium calcium carbonate powder from Example 3 was mixed with a specific surface area of ​​30m³. 2 / g nano titanium dioxide powder, according to (Ba 1-x Ca x ) m Weigh the TiO3 molar ratio, m = 1.000. Mix the weighed powder with deionized water to make the solid content 50%, and add 2% of the powder content of dispersant. Stir and slurry for 10 minutes.

[0110] (2) The slurry from step (1) is placed in a vertical sand mill for grinding. The grinding balls are 0.3mm zirconia balls, the linear speed is 6m / s, and the grinding time is 120min.

[0111] (3) Dry the slurry ground in step (2) at 150°C and then mechanically crush it.

[0112] (4) The powder from step (3) was calcined at 970°C in a ventilated muffle furnace with a heating rate of 10°C / min and a holding time of 4 hours in the high-temperature section. The calcined powder was then simply dispersed and subjected to XRD, XRF, specific surface area, and SEM tests.

[0113] Comparative Example 4

[0114] (1) A surface area of ​​10m 2 / g of barium carbonate and a specific surface area of ​​7m² 2 / g of calcium carbonate powder and a specific surface area of ​​30m² 2 / g nano titanium dioxide powder, according to (Ba 0.95 Ca 0.05 ) m Weigh the TiO3 molar ratio, m = 1.000. Mix the weighed powder with deionized water to make the solid content 50%, and add 2% of the powder content of dispersant. Stir and slurry for 10 minutes.

[0115] (2) The slurry from step (1) is placed in a vertical sand mill for grinding. The grinding balls are 0.3mm zirconia balls, the linear speed is 6m / s, and the grinding time is 120min.

[0116] (3) The slurry ground in step (2) was dried at 150°C and then mechanically crushed. The crushed powder after drying was subjected to EDS composition distribution analysis.

[0117] (4) The powder from step (3) was calcined at 970°C in a ventilated muffle furnace with a heating rate of 10°C / min and a holding time of 4 hours in the high-temperature section. The calcined powder was then simply dispersed and subjected to XRD, XRF, specific surface area, and SEM tests.

[0118] The test results of the barium calcium titanate powder obtained in Examples 5 and 6 and Comparative Example 4 are summarized as follows:

[0119] The elemental distribution of the dried and crushed powders in Example 5 and Comparative Example 4 was analyzed using EDS surface scanning, such as... Figure 11 Comparative Example 4 shows uneven distribution of barium and calcium at the microscopic level, with localized calcium segregation found. Figure 12 The calcium and barium distributions in Example 5 are both very uniform.

[0120] The powder test results after calcination of Examples 5, 6 and Comparative Examples 4-6 are shown in Table 2. Examples 5 and 6 both achieved good crystallinity and uniformity.

[0121] Table 2. Detection results of calcined powder from Examples 5-6 and Comparative Example 4.

[0122]

[0123] Note that in Table 2, "c / a" is the ratio of the length of the c-axis to the length of the a-axis, which is the lattice constant.

[0124] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nano-barium calcium carbonate solid solution, comprising the following steps: A) Mix and dissolve an alkaline soluble barium source and an alkaline soluble calcium source in water to obtain a mixed solution; The molar ratio of Ba in the alkaline soluble barium source to calcium in the alkaline soluble calcium salt is (1-X):X, 0<X≤0.15; B) The mixed solution is rapidly mixed with carbon dioxide in a gas-liquid mixer to generate barium calcium carbonate slurry; C) The barium calcium carbonate slurry is subjected to solid-liquid separation and then spray-dried to obtain nano-barium calcium carbonate.

2. The preparation method according to claim 1, characterized in that, The alkaline soluble barium source is barium hydroxide, and the alkaline soluble calcium source is calcium hydroxide and / or calcium oxide.

3. The preparation method according to claim 1, characterized in that, The mass concentration of alkaline soluble barium source in the mixed solution is ≤8%, and the mass concentration of alkaline soluble calcium source is ≤0.18%.

4. The preparation method according to claim 1, characterized in that, The dissolution temperature in step A) is 0~40℃.

5. The preparation method according to claim 1, characterized in that, The pressure of carbon dioxide in step B) is 0.2~1.0 MPa.

6. The preparation method according to claim 5, characterized in that, In the rapid mixing reaction, the flow rate of carbon dioxide gas is 5 to 40 times that of the liquid flow rate.

7. A method for preparing barium calcium titanate powder, comprising preparing a nano-barium calcium carbonate solid solution obtained by the method for preparing nano-barium calcium carbonate solid solution according to any one of claims 1 to 6 and a titanium source by solid-phase sintering.

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