Barium calcium titanate powder, preparation method and application thereof

Abstract

The application relates to the technical field of capacitor materials, in particular to a barium calcium titanate powder, a preparation method and application thereof. The barium calcium titanate powder has a chemical formula shown in formula (I); under the condition of 25+3 DEG C, the cell volume V of the barium calcium titanate powder is measured by using XRD and satisfies formula (1). In the barium calcium titanate powder provided by the application, calcium is uniformly doped, and there are no impurities such as calcium titanate, calcium hydroxide and calcium carbonate. Compared with the prior art, the advantages of the application are that all the calcium can be solid-solved into the barium calcium titanate, and only a minimum amount of necessary calcium needs to be added, so the performance is more excellent compared with the prior art. Because all the calcium replaces calcium with a larger atomic radius, under the condition of the same amount of added calcium, the cell volume is smaller, and the crystal face interval is narrower compared with the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor materials, and in particular to barium calcium titanate powder, a preparation method and application thereof. Background Art

[0002] Currently, barium titanate is used as the main dielectric material in MLCC capacitors. However, this material suffers from insufficient reduction resistance. MLCCs consist of a dielectric layer, inner electrodes, and outer electrodes made of nickel. To prevent oxidation, manufacturers must fire MLCCs in a reducing atmosphere. However, when barium titanate-based ceramic powder is fired at high temperatures in a reducing atmosphere, oxygen atoms in the crystal lattice are easily lost, escaping into oxygen and forming oxygen vacancies, which reduces reliability.

[0003] Calcium barium titanate powder is a new type of perovskite dielectric ceramic nanopowder used as the main dielectric material in MLCC capacitors. Doping barium titanate with calcium effectively improves its reduction resistance. The introduction of calcium modifies the chemical energy of thermal transitions and inhibits the generation of oxygen vacancies, effectively improving its reduction resistance and addressing the potential reduction of BT powder.

[0004] Currently available methods for preparing barium titanate include solid-phase calcination, oxalic acid precipitation, metal alkoxide, hydrothermal, and atmospheric pressure hydrothermal, which involves a synthesis reaction between titanium and barium compounds in a strong alkaline solution. Calcium barium titanate is produced by doping barium titanate with a calcium source during its preparation.

[0005] The problem with the solid-phase firing method for preparing barium titanate is that, after mixing and dispersing barium carbonate, titanium dioxide, etc. as raw materials, the product is prepared by high-temperature firing. Although the manufacturing cost is low, due to the high-temperature firing and the large difference in particle size between the titanium source and the barium source raw materials, the solid-phase firing method is difficult to prepare products with small particle size and good particle size distribution. When preparing barium calcium titanate, in addition to the barium carbonate and titanium dioxide raw materials, calcium carbonate is added as a raw material, and barium calcium titanate is prepared by uniform mixing or sand milling and then firing. For example, the patent with publication number CN 114105190 A (Patent 1) discloses a barium calcium titanate nanocrystalline medium material and its preparation method, which is obtained by mixing titanium dioxide, barium carbonate and calcium carbonate in a stoichiometric ratio, adding water and a dispersant to obtain a slurry, and the slurry is dried, sieved, and calcined to obtain barium calcium titanate powder. Its shortcomings are: ① The solid-phase sintering method requires a relatively high temperature to sinter barium calcium titanate, so it is impossible to obtain a small-particle barium calcium titanate product; ② Due to the different primary particle sizes of titanium dioxide, barium carbonate and calcium carbonate raw materials, the particle sizes of barium carbonate and calcium carbonate are significantly higher than that of titanium dioxide. It is difficult to evenly mix the three raw materials during the sand milling process, resulting in difficulty in homogenizing the powder composition after calcination, thereby affecting the powder performance; ③ During the sintering process of barium calcium titanate, the grain growth temperatures of each component are different, and some components grow preferentially, affecting the uniformity of the synthetic components. Patent publication number CN 100373508C (Patent 2) discloses a method for producing a raw material powder for dielectric ceramics, a dielectric ceramic, and a multilayer ceramic capacitor. It states that "even if micronized barium carbonate powder and titanium dioxide powder are uniformly dispersed, barium carbonate particles tend to grow during the calcination step of synthesizing barium titanate from the barium carbonate powder and titanium dioxide. Therefore, the barium carbonate particles grow before the titanium dioxide reacts, making it difficult for the barium carbonate particles to react uniformly with the titanium dioxide." Therefore, the methods described in Patents 1 and 2 above are difficult to prepare fine-grained, uniformly calcium-doped barium calcium titanate powders, primarily due to the process characteristics of the high-temperature solid-phase method.

[0006] The oxalic acid precipitation method uses titanium, barium, and calcium sources in an oxalic acid environment to synthesize an oxalate precipitate. This is then calcined at high temperature to remove the carbonate ions, resulting in a barium calcium titanate powder. This method is problematic because the carbonate ions in the oxalate exist as impurities, increasing the barium carbonate impurity content. Furthermore, the synthesis process introduces a large number of hydroxyl defects, which form pores on the powder surface and within the powder, affecting the product's electrical properties.

[0007] The metal alkoxide method involves mixing alcoholic solutions of a barium source, a titanium source, and a calcium source, hydrolyzing and reacting to precipitate the mixture at a specific temperature to synthesize barium calcium titanate powder, which is then sintered at a high temperature to obtain a tetragonal barium calcium titanate powder. For example, patent publication number CN1338430A (Patent 3) discloses a barium titanate microparticle powder, a calcium-modified barium titanate microparticle powder, and a method for producing the same. The raw materials are an aqueous solution of barium hydroxide, an alcoholic solution of titanium alkoxide, and an alcoholic solution of calcium nitrate. The alcoholic solution of titanium alkoxide and the alcoholic solution of calcium nitrate are pre-mixed, then mixed with a barium hydroxide solution in a specific ratio to synthesize barium calcium titanate. The barium calcium titanate is then heat-treated at 950-1100°C to obtain barium calcium titanate. The advantage of this method is that it can produce small-particle barium calcium titanate powder, with a particle size range of 0.145 to 0.250 μm. However, the disadvantage is that when the alcohol solution of alkoxy titanium, the alcohol solution of calcium nitrate, and the barium hydroxide solution are mixed and reacted, calcium titanate is also produced along with barium calcium titanate. Calcium titanate exists as an impurity, affecting the electrical properties of the product. In addition, the generated calcium titanate impurities occupy a portion of the calcium. In order to ensure that the barium calcium titanate has the required reduction resistance, more calcium must be added than required, which leads to a decrease in the dielectric constant.

[0008] The atmospheric pressure hydrothermal method for synthesizing barium calcium titanate using a titanium source, a barium source, and a calcium source under alkaline conditions generally uses a hydrolyzate of a titanium compound, a water-soluble barium source, and a calcium source to synthesize a powder under an alkaline environment, and then sintering at a high temperature to prepare barium calcium titanate. For example, patent publication number CN100575263C (Patent 4) discloses a barium calcium titanate, a method for manufacturing the same, and a capacitor. The method comprises adding barium hydroxide and titanium dioxide to an alkaline solution containing an alkaline compound at a pH of 10 or higher and reacting to synthesize barium titanate, and then adding calcium hydroxide to react and synthesize barium calcium titanate. This method can prepare barium calcium titanate with a small particle size and relatively uniform calcium doping. In this method, the calcium source is doped after the synthesis of barium titanate. The doped calcium enters the barium titanate lattice structure to form barium calcium titanate. When the ratio of the sum of the molar amounts of calcium and barium to the molar amount of titanium reaches 1.0000, it is difficult for the remaining calcium to enter the barium calcium titanate lattice and replace the barium. They are more likely to exist on the surface of the barium calcium titanate in the form of calcium hydroxide or oxide. Although this part of calcium can be detected during component testing, it loses its due function. During long-term storage, it gradually reacts with carbon dioxide in the air to form calcium carbonate, which becomes an impurity in the barium calcium titanate and affects the electrical properties.

[0009] As is well known, the purpose of doping calcium in barium titanate is to improve the reduction resistance. However, when the amount of calcium added increases, the disadvantage of a decrease in dielectric constant occurs. In the prior synthesis technology, not all of the calcium introduced can be completely solid-solved in barium calcium titanate, and part of the calcium exists on the surface of barium calcium titanate in the form of calcium hydroxide, calcium carbonate, and calcium titanate. Therefore, in order to obtain sufficient reduction resistance, it is necessary to add more calcium than the required amount. In contrast, the advantage of the present invention is that all of the calcium can be solid-solved inside barium calcium titanate, and only the minimum necessary amount of calcium needs to be added, so the performance is more excellent than the current technology. Since all of the calcium replaces calcium with a larger atomic radius, when compared with the current technology under the same amount of calcium added, the unit cell volume becomes smaller and the crystal plane spacing becomes narrower. Summary of the Invention

[0010] In view of this, the technical problem to be solved by the present invention is to provide a barium calcium titanate powder, a preparation method thereof, and an application. In the barium calcium titanate powder provided by the present invention, calcium doping is uniform, and there are no impurities such as calcium titanate, calcium hydroxide, and calcium carbonate.

[0011] The present invention provides a barium calcium titanate powder having the chemical formula shown in formula (I):

[0012] Ba x+z Ca y TiO3 (I);

[0013] In formula (I), y is the elemental molar ratio content of Ca, 0 < y ≤ 0.15, and 0.98 ≤ x + y + z ≤ 1.015;

[0014] Under the condition of 25 ± 3 °C, the unit cell volume V of the barium calcium titanate powder measured by XRD satisfies formula (1):

[0015] V ≤ 64.3 - 6.6 × y (1);

[0016] In formula (1), 0 < y ≤ 0.15.

[0017] Preferably, the FWHM of the (110) crystal plane of the barium calcium titanate powder is ≤ 0.40 °, and the FWHM of the (111) crystal plane is ≤ 0.30 °.

[0018] The present invention also provides a preparation method for the barium calcium titanate powder described above, including the following steps:

[0019] A) Mix a part of the barium source with a strong base solution, heat the obtained mixed solution, and then mix it with the titanium source solution for reaction to obtain a product solution containing barium titanate shown in formula (II);

[0020] Ba x TiO3 Formula (II);

[0021] In formula (II), 0.85≤x<1.00;

[0022] B) mixing a product solution containing barium titanate represented by formula (II) with a calcium source and reacting the mixture to obtain a barium calcium titanate process product represented by formula (III):

[0023] Ba x Ca y TiO3 formula (III);

[0024] In formula (III), 0 <y≤0.15,0.85<x+y≤1.00;

[0025] C) reacting the barium calcium titanate process product represented by formula (III) with the remaining barium source to obtain the barium calcium titanate precursor represented by formula (I);

[0026] Ba x+z Ca y TiO3 formula (Ⅰ);

[0027] In formula (I), 0<y≤0.15,z> 0, 0.98≤x+y+z≤1.015.

[0028] Preferably, after step C), the method further comprises:

[0029] D) calcining the barium calcium titanate precursor represented by formula (I) to obtain barium calcium titanate powder having the chemical formula represented by formula (I).

[0030] Preferably, the barium source includes at least one of barium hydroxide octahydrate, barium hydroxide monohydrate, anhydrous barium hydroxide, barium chloride, barium chlorate, barium acetate, barium nitrate and barium oxide.

[0031] Preferably, in step A), the pH value of the strong alkaline solution is ≥12;

[0032] The strong base includes lithium hydroxide, sodium hydroxide, potassium hydroxide or quaternary ammonium hydroxide.

[0033] Preferably, in step A), the titanium source comprises at least one of titanium tetrachloride solution, titanium hydroxide suspension, hydrated titanium dioxide suspension, titanium oxychloride and titanium dioxide suspension;

[0034] The specific surface area of ​​the powder of the titanium dioxide suspension after drying is 50 to 200 m 2 / g, primary particle size is 8-30nm;

[0035] In the titanium dioxide suspension, the crystal form requirements of titanium dioxide include: the mass content of rutile is ≤20%, and the rest is at least one of anatase and brookite.

[0036] Preferably, the calcium source includes at least one of calcium hydroxide powder, calcium chloride powder, and calcium oxide powder.

[0037] The present invention also provides a dielectric material, and the raw materials for preparing the dielectric material include the calcium barium titanate powder described above or the calcium barium titanate powder prepared by the preparation method described above.

[0038] The present invention also provides a ceramic capacitor, and the raw materials for preparing the ceramic capacitor include the calcium barium titanate powder described above or the calcium barium titanate powder prepared by the preparation method described above.

[0039] The present invention also provides a slurry, and the raw materials for preparing the slurry include the calcium barium titanate powder described above or the calcium barium titanate powder prepared by the preparation method described above.

[0040] The present invention also provides a green sheet, and the raw materials for preparing the green sheet include the calcium barium titanate powder described above or the calcium barium titanate powder prepared by the preparation method described above.

[0041] The present invention provides a calcium barium titanate powder having a chemical formula shown in formula (I):

[0042] Ba x+z Ca y TiO3 (I);

[0043] In formula (I), y is the elemental molar ratio content of Ca, 0 < y ≤ 0.15, and 0.98 ≤ x + y + z ≤ 1.015;

[0044] Under the condition of 25 ± 3 °C, the unit cell volume V of the calcium barium titanate powder measured by XRD satisfies formula (1):

[0045] V ≤ 64.3 - 6.6 × y (1);

[0046] In formula (1), 0 < y ≤ 0.15.

[0047] In the calcium barium titanate powder provided by the present invention, calcium doping is uniform, and there are no impurities such as calcium titanate, calcium hydroxide, and calcium carbonate. Compared with the prior art, the advantage of the present invention is that all calcium can be solid-solved into the calcium barium titanate, and only the least amount of necessary calcium needs to be added. Therefore, the performance is more excellent compared with the current technology. Because all calcium replaces calcium with a larger atomic radius, when comparing with the current technology under the same addition amount of calcium, the unit cell volume becomes smaller and the crystal plane spacing becomes narrower. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the XRD pattern of the calcium barium titanate precursor prepared in Example 1 of the present invention;

[0049] Figure 2 TEM-EDS elemental mapping of the calcium barium titanate precursor prepared in Example 1 of the present invention;

[0050] Figure 3 XRD pattern of the calcium barium titanate powder 1-1 in Example 1;

[0051] Figure 4 TEM-EDS elemental mapping of the calcium barium titanate powder 1-1 in Example 1;

[0052] Figure 5 SEM image of the calcium barium titanate powder 1-1 in Example 1;

[0053] Figure 6 XRD pattern of the calcium barium titanate precursor in Comparative Example 1;

[0054] Figure 7 XRD pattern of the calcium barium titanate precursor in Comparative Example 3;

[0055] Figure 8 XRD pattern of the calcium barium titanate precursor in Comparative Example 4;

[0056] Figure 9 XRD pattern of the calcium barium titanate precursor in Comparative Example 5. Detailed implementation manners

[0057] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0058] Strong dielectrics of barium titanate will undergo phase transitions at temperatures close to room temperature below 130 °C. Therefore, the lattice constant will fluctuate greatly at temperatures close to room temperature. Therefore, the unit cell volume V, which is an important condition of the present invention, needs to be measured at a certain range of temperatures.

[0059] The present invention provides a calcium barium titanate powder having the chemical formula shown in Formula (I): [[ID=四十一]]

[0060] Ba x+z Ca y TiO3 (I);

[0061] In Formula (I), y is the doping concentration of Ca, that is, the elemental molar ratio content, 0 < y ≤ 0.15, and 0.98 ≤ x + y + z ≤ 1.015; [[ID=五十一]]

[0062] Under the condition of 25±3°C, the unit cell volume V of the calcium barium titanate powder measured by XRD satisfies formula (1):

[0063] V≤64.3 - 6.6×y (1);

[0064] In formula (1), y is the doping concentration of Ca, that is, the elemental molar ratio content, 0 < y ≤ 0.15; the unit of V is ų.

[0065] In certain embodiments of the present invention, in formula (I), z > 0.

[0066] In certain embodiments of the present invention, x = 0.9445, y = 0.0503, z = 0.0112, x + y + z = 1.0055; in certain embodiments of the present invention, x = 0.9464, y = 0.0504, z = 0.0082, x + y + z = 1.0050; in certain embodiments of the present invention, x + z = 0.9948, y = 0.0103; in certain embodiments of the present invention, x + z = 0.9754, y = 0.0300; in certain embodiments of the present invention, x + z = 0.9549, y = 0.0503; in certain embodiments of the present invention, x + z = 0.9048, y = 0.1004; in certain embodiments of the present invention, x + z = 0.8550, y = 0.1509.

[0067] In certain embodiments of the present invention, V = 63.59 ų, 63.96 ų, 63.95 ų, 64.22 ų, 64.07 ų, 63.61 ų or 63.29 ų.

[0068] In certain embodiments of the present invention, the FWHM of the (110) crystal plane of the calcium barium titanate powder ≤ 0.40°, and the FWHM of the (111) crystal plane ≤ 0.30°. In certain embodiments, the FWHM of the (110) crystal plane of the calcium barium titanate powder is 0.300°, 0.267°, 0.260°, 0.235°, 0.247°, 0.324° or 0.379°; the FWHM of the (111) crystal plane is 0.245°, 0.201°, 0.198°, 0.192°, 0.193°, 0.2°, 0.254° or 0.289°.

[0069] In certain embodiments of the present invention, the particle size of the calcium barium titanate powder is 50 - 250 nm.

[0070] The present invention also provides a preparation method of the calcium barium titanate powder described above, including the following steps:

[0071] A) mixing a portion of a barium source with a strong base solution, heating the resulting mixed solution, and then mixing with a titanium source solution to react to obtain a product solution containing barium titanate represented by formula (II);

[0072] Ba x TiO3 formula (II);

[0073] In formula (II), 0.85≤x<1.00;

[0074] B) mixing a product solution containing barium titanate represented by formula (II) with a calcium source and reacting the mixture to obtain a barium calcium titanate process product represented by formula (III):

[0075] Ba x Ca y TiO3 formula (III);

[0076] In formula (III), 0 <y≤0.15,0.85<x+y≤1.00;

[0077] C) reacting the barium calcium titanate process product represented by formula (III) with the remaining barium source to obtain the barium calcium titanate precursor represented by formula (I);

[0078] Ba x+z Ca y TiO3 formula (Ⅰ);

[0079] In formula (I), 0<y≤0.15,z> 0, 0.98≤x+y+z≤1.015.

[0080] In step A):

[0081] Mixing a portion of the barium source with a strong base solution, heating the resulting mixed solution, and then mixing it with a titanium source solution to react to obtain a product solution containing barium titanate represented by formula (II);

[0082] Ba x TiO3 formula (II);

[0083] In formula (II), 0.85≤x<1.00; preferably, 0.90≤x<1.00.

[0084] In certain embodiments of the present invention, the barium source includes at least one of barium hydroxide octahydrate, barium hydroxide monohydrate, anhydrous barium hydroxide, barium chloride, barium chlorate, barium acetate, barium nitrate, and barium oxide.

[0085] In certain embodiments of the present invention, the strong base solution is a soluble alkaline catalyst, and the pH value of the strong base solution is ≥12, preferably ≥13, and specifically 14. The strong base includes lithium hydroxide, sodium hydroxide, potassium hydroxide, or quaternary ammonium hydroxide.

[0086] In certain embodiments of the present invention, before mixing the portion of the barium source with the strong base solution, the method further comprises:

[0087] Heat the strong base solution to ≥80°C and keep it warm for ≥10 minutes. In some embodiments of the present invention, the strong base is heated to 80-90°C, specifically 88°C or 90°C.

[0088] In some embodiments of the present invention, mixing a portion of the barium source with the strong alkaline solution includes dissolving a portion of the barium source in the strong alkaline solution.

[0089] In certain embodiments of the present invention, a barium source is mixed with a strong base solution, and the resulting mixed solution is heated to a reaction temperature.

[0090] In certain embodiments of the present invention, the titanium source comprises at least one of a titanium tetrachloride solution, a titanium hydroxide suspension, a hydrated titanium dioxide suspension, a titanium oxychloride, and a titanium dioxide suspension. In certain embodiments, the titanium source is a titanium dioxide suspension. The specific surface area of ​​the powder of the titanium dioxide suspension after drying is 50 to 200 m 2 / g, specifically, 150m 2 / g、146m 2 / g; the primary particle size is 8 to 30 nm, specifically, it can be 10 nm. In the titanium dioxide suspension, the crystal form requirements of titanium dioxide include: the mass content of rutile ≤ 20%, specifically, it can be 9.2% or 7.82%; the rest is at least one of anatase and brookite. In certain embodiments, the crystal form of the titanium dioxide powder includes: rutile with a mass content of 9.2%, brookite with a mass content of 62.83%, and anatase with a mass content of 27.97%. In certain embodiments, the crystal form of the titanium dioxide powder includes: rutile with a mass content of 7.82%, brookite with a mass content of 66.84%, and anatase with a mass content of 25.34%.

[0091] In certain embodiments of the present invention, the method for preparing the titanium dioxide suspension comprises:

[0092] Titanium dioxide suspension is obtained by hydrolyzing titanium tetrachloride solution.

[0093] In certain embodiments of the present invention, the concentration of the titanium tetrachloride solution is 0.4 mol / L. The hydrolysis temperature is 104°C.

[0094] Specifically, after the hydrolysis, the process further includes cooling to room temperature, removing impurities, and concentrating to obtain a titanium dioxide suspension. The cooling rate is 2°C / min. The impurity removal method can include anion exchange resin, electrodialysis, high-purity water cleaning, etc. Specifically, anion exchange resin is used for impurity removal, and the ratio of the anion exchange resin to the cooled solution is 1403g:1L. When the pH value of the solution reaches 3.6, impurity removal is stopped. The concentration can be achieved using a hollow fiber membrane concentration system, a ceramic membrane concentration system, a centrifugal system, etc. The mass concentration of the titanium dioxide suspension is 15.68%.

[0095] In certain embodiments of the present invention, the method for preparing the titanium dioxide suspension comprises:

[0096] Titanium dioxide powder is dispersed in water to prepare a titanium dioxide suspension.

[0097] Specifically, the method comprises: mixing titanium dioxide powder, water and a dispersant, and then performing sand milling to disperse the obtained liquid to obtain a titanium dioxide dispersion, namely a titanium dioxide suspension, which is uniform and stable.

[0098] In certain embodiments of the present invention, the solid content of the mixed liquid is 8 wt% to 28 wt%, and the content of the dispersant in the liquid is 1 wt% to 3 wt%. Specifically, the solid content of the mixed liquid is 20 wt%, and the content of the dispersant in the liquid is 2 wt%.

[0099] The specific surface area of ​​the titanium dioxide powder is 50 to 200 m 2 / g, specifically, 150m 2 / g; the primary particle size of the titanium dioxide powder is 8 to 30 nm, specifically, 10 nm.

[0100] The titanium dioxide powder has crystal form requirements including: a rutile content of ≤20% by weight, specifically 9.2% by weight; the remainder being at least one of anatase and brookite. In certain embodiments, the titanium dioxide powder comprises: 9.2% by weight rutile, 62.83% by weight brookite, and 27.97% by weight anatase.

[0101] In certain embodiments of the present invention, the dispersant includes at least one of sodium hexametaphosphate, ammonium hexametaphosphate, sodium polybenzoate, and polycarboxylate ammonium salt dispersants.

[0102] In certain embodiments of the present invention, the reaction temperature is 90-110° C., the pressure is normal pressure, and the reaction time is 1-2 h. In certain embodiments, the reaction temperature is 105° C., and the reaction time is 1.5 h.

[0103] In step B):

[0104] The product solution containing barium titanate represented by formula (II) is mixed with a calcium source and reacted to obtain a barium calcium titanate process product represented by formula (III):

[0105] Ba x Ca y TiO3 formula (III);

[0106] In formula (III), 0 <y≤0.15,0.85<x+y≤1.00。

[0107] In some embodiments of the present invention, x=0.9445, y=0.0500, x+y=0.9945. In some embodiments of the present invention, x=0.9464, y=0.0500, x+y=0.9964.

[0108] In certain embodiments of the present invention, the calcium source includes at least one of calcium hydroxide powder, calcium chloride powder, and calcium oxide powder.

[0109] In certain embodiments of the present invention, the reaction temperature is 90-110° C., the pressure is normal pressure, and the reaction time is 4-12 h. In certain embodiments, the reaction temperature is 105° C. and the reaction time is 8 h.

[0110] In certain embodiments of the present invention, after the reaction, the process further comprises: sampling and testing to obtain the elemental molar ratios of Ba / Ti and Ca / Ti, thereby obtaining the barium calcium titanate process product represented by formula (III).

[0111] In step C):

[0112] reacting the barium calcium titanate process product represented by formula (III) with the remaining barium source to obtain the barium calcium titanate precursor represented by formula (I);

[0113] Ba x+z Ca y TiO3 formula (Ⅰ);

[0114] In formula (I), 0<y≤0.15,z> 0, 0.98≤x+y+z≤1.015.

[0115] In some embodiments of the present invention, x = 0.9445, y = 0.0503, z = 0.0112, x + y + z = 1.0055. In some embodiments of the present invention, x = 0.9464, y = 0.0504, z = 0.0082, x + y + z = 1.0050.

[0116] In certain embodiments of the present invention, the reaction temperature is 90-110° C., the pressure is normal pressure, and the reaction time is 1-2 h. In certain embodiments, the reaction temperature is 105° C. and the reaction time is 1 h.

[0117] In certain embodiments of the present invention, after the reaction is completed, the process further comprises: allowing the slurry to settle after the reaction, washing, filtering and drying to obtain a barium calcium titanate precursor represented by formula (I).

[0118] The cleaning agent includes an alcohol, such as ethanol or ethylene glycol, to remove alkaline substances and impurities during the reaction, thereby obtaining a high-purity barium calcium titanate powder. The mass ratio of the detergent to the precipitate is 1.5 to 6:1, and more specifically, 5:1.

[0119] The filtering and drying methods may be plate and frame filter pressing + drying; centrifugal filtration + drying; flash drying; spray drying; three-in-one equipment for cleaning, filtering and drying, etc.

[0120] In certain embodiments of the present invention, the drying temperature is 150-300°C, specifically, 200°C.

[0121] In certain embodiments of the present invention, after drying, the method further comprises: crushing through a 100-mesh sieve.

[0122] In certain embodiments of the present invention, after the reaction, the process further comprises: sampling and testing to obtain the elemental molar ratios of Ba / Ti and Ca / Ti, thereby obtaining the barium calcium titanate precursor represented by formula (I).

[0123] In certain embodiments of the present invention, after step C), the method further comprises:

[0124] D) calcining the barium calcium titanate precursor represented by formula (I) to obtain barium calcium titanate powder having the chemical formula represented by formula (I).

[0125] In step D):

[0126] The barium calcium titanate precursor represented by formula (I) is calcined to obtain barium calcium titanate powder having the chemical formula represented by formula (I).

[0127] Specifically, the barium calcium titanate precursor represented by formula (I) is heated to a sintering temperature and sintered to obtain barium calcium titanate powder having the chemical formula represented by formula (I).

[0128] In certain embodiments of the present invention, the heating rate is 8 to 12°C / min, specifically, 10°C / min; the sintering temperature is 600 to 1200°C, specifically, 960°C or 1010°C; the sintering time is 1.5 to 2.5h, specifically, 2h.

[0129] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0130] The invention provides a novel preparation method of barium calcium titanate powder. The prepared barium calcium titanate powder is uniformly doped with calcium and is free of impurities such as calcium titanate, calcium hydroxide and calcium carbonate.

[0131] The present invention also provides a dielectric material, wherein the raw materials for preparing the dielectric material include the barium calcium titanate powder described above or the barium calcium titanate powder prepared by the preparation method described above.

[0132] The present invention also provides a ceramic capacitor, wherein the raw materials for preparing the ceramic capacitor include the barium calcium titanate powder described above or the barium calcium titanate powder prepared by the preparation method described above.

[0133] The present invention also provides a slurry, wherein the raw materials for preparing the slurry include the barium calcium titanate powder described above or the barium calcium titanate powder prepared by the preparation method described above.

[0134] The present invention also provides an original sheet, wherein the raw materials for preparing the original sheet include the barium calcium titanate powder described above or the barium calcium titanate powder prepared by the preparation method described above.

[0135] In order to further illustrate the present invention, the barium calcium titanate powder, its preparation method and application provided by the present invention are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0136] Example 1:

[0137] Take specific surface area = 150m 2 / g, titanium dioxide powder (rutile content of 9.2% by mass) with a primary particle size of 10nm was mixed with water and a polycarboxylate ammonium salt dispersant to obtain a slurry with a solid content of 20wt% and a dispersant content of 2wt%. Sand milling was performed, and the solid content of the powder during sand milling was designed to be 20wt% and the dispersant content was 2wt%. After sand milling, a uniform and stable titanium dioxide suspension was obtained. The specific surface area and crystal form of the titanium dioxide powder in the titanium dioxide suspension were tested and shown in Table 1:

[0138] Table 1 Detection results of titanium dioxide powder in titanium dioxide suspension in Example 1

[0139] <![CDATA[Specific surface area [m 2 / g]]]> Brookite [wt%] Anatase [wt%] Rutile [wt%] 150 62.83 27.97 9.20

[0140] 1.5 L of 2 mol / L sodium hydroxide solution (pH 14) was prepared, and the electric heating mantle was heated to 88° C. and kept warm for 10 minutes. 445.3 g of barium hydroxide octahydrate powder was added and stirred for dissolution for 10 minutes. The obtained mixed solution was then heated to 105° C., and 584.7 g of the titanium dioxide suspension was added. The mixture was reacted at normal pressure and 105° C. for 1.5 hours. After the reaction was completed, a product solution of barium titanate represented by formula (II) (wherein x = 0.9445) was obtained. 5.83 g of calcium hydroxide powder was added, and the mixture was continued to react at normal pressure and 105° C. for 8 hours. The sampling test results showed that Ba / Ti = 0.9445 and Ca / Ti = 0.0500, i.e., a product of formula Ba was obtained. 0.9445 Ca 0.0500 TiO3 (where x = 0.9445 and y = 0.0500) is a barium calcium titanate process suspension.

[0141] The remaining barium hydroxide octahydrate, weighing 4.7 g, was added and the reaction was continued at normal pressure and 105°C for 1 hour to complete the reaction. The mixture was allowed to settle and the supernatant was poured out. After washing with ethanol 5 times the mass of barium calcium titanate, the mixture was filtered to form a powder cake, dried at 200°C, and crushed through a 100-mesh sieve to obtain a powder. The composition test results showed that Ba / Ti = 0.9552 and Ca / Ti = 0.0503, i.e., the formula Ba was obtained. 0.9552 Ca 0.0503 A barium calcium titanate precursor represented by TiO3 (wherein x=0.9445, y=0.0503, z=0.0112) wherein z>0, x+y+z=1.0055, satisfies the requirements of formula (I).

[0142] Figure 1 The XRD pattern of the barium calcium titanate precursor prepared in Example 1 of the present invention is as follows: Figure 1 As shown, the sample contains only barium calcium titanate without impurities such as calcium titanate, calcium hydroxide or calcium carbonate. Figure 2 TEM-EDS element mapping diagram of the barium calcium titanate precursor prepared in Example 1 of the present invention, Figure 2 It can be judged that the calcium doping is uniform.

[0143] The obtained precursor was heat-treated: the temperature was increased at a rate of 10°C / min, and the heat treatment was performed at 960°C for 2h to obtain barium calcium titanate powder 1-1; the temperature was increased at a rate of 10°C / min, and the heat treatment was performed at 1010°C for 2h to obtain barium calcium titanate powder 1-2.

[0144] The test results in Table 2 were obtained through X-ray fluorescence spectroscopy analysis, specific surface area detector, X-ray diffractometer, etc.:

[0145] Table 2 Test results of barium calcium titanate powder obtained in Example 1

[0146]

[0147] In Table 2, D (specific surface area) is a particle size value calculated based on the barium calcium titanate particles being spheres.

[0148] Figure 3 The XRD pattern of barium calcium titanate powder 1-1 in Example 1 is as follows: Figure 3 As shown, the sample contains only barium calcium titanate without impurities such as calcium titanate, calcium hydroxide or calcium carbonate. Figure 4 TEM-EDS element mapping diagram of barium calcium titanate powder 1-1 in Example 1, Figure 4 It can be judged that the calcium doping is uniform. Figure 5 This is the SEM image of the barium calcium titanate powder 1-1 in Example 1. Figure 5 It can be seen that the particle size distribution of the barium calcium titanate powder prepared in the present invention is relatively uniform.

[0149] Example 2:

[0150] 5 L of a 0.4 mol / L titanium tetrachloride solution was poured into a four-necked flat-bottom flask, heated to 104°C, and hydrolyzed at 104°C for 60 min. The solution was then cooled to room temperature at a rate of 2°C / min. An anion exchange resin was used to remove impurities from the resulting solution. The ratio of the anion exchange resin to the solution was 1403 g:1 L. When the pH value of the solution reached 3.6, the impurity removal was stopped. The solution was then concentrated using a hollow fiber membrane to obtain a titanium dioxide suspension with a mass concentration of 15.68%. The specific surface area and crystal form of the titanium dioxide were shown in Table 3:

[0151] Table 3 Specific surface area and crystal form test results of titanium dioxide in Example 2

[0152] <![CDATA[Specific surface area [m 2 / g]]]> Brookite [wt%] Anatase [wt%] Rutile [wt%] 146 66.84 25.34 7.82

[0153] 1.5 L of 2 mol / L sodium hydroxide solution (pH 14) was prepared, and the electric heating mantle was heated to 90° C. and kept warm for 10 minutes. 445.3 g of barium hydroxide octahydrate powder was added and stirred for dissolution for 10 minutes. The obtained mixed solution was then heated to 105° C., and 745.8 g of the titanium dioxide suspension was added. The mixture was reacted at normal pressure and 105° C. for 1.5 hours. After the reaction was completed, a product solution of barium titanate represented by formula (II) (wherein x = 0.9464) was obtained. 5.83 g of calcium hydroxide powder was then added, and the reaction was continued for 8 hours. The sampling test results showed that Ba / Ti = 0.9464 and Ca / Ti = 0.0500, i.e., a product of formula Ba was obtained. 0.9464 Ca 0.0500TiO3 (where x = 0.9464, y = 0.0500) is a barium calcium titanate process suspension.

[0154] The remaining barium hydroxide octahydrate, weighing 4.7 g, was added and the reaction was continued at normal pressure and 105°C for 1 hour to complete the reaction. The mixture was allowed to settle and the supernatant was poured out. After washing with ethanol 5 times the mass of barium calcium titanate, the mixture was filtered to form a powder cake, dried at 200°C, and crushed through a 100-mesh sieve to obtain a powder. The composition test results showed that Ba / Ti=0.9546 and Ca / Ti=0.0504, i.e., the formula Ba was obtained. 0.9546 Ca 0.0504 A barium calcium titanate precursor is shown as TiO3 (where x = 0.9464, y = 0.0504, and z = 0.0082). In this precursor, z > 0 and x + y + z = 1.0050, satisfying the requirements of formula (I). X-ray diffractometry revealed that the sample contained only barium calcium titanate, with no impurities such as calcium titanate, calcium hydroxide, or calcium carbonate. TEM-EDS elemental mapping confirmed uniform calcium doping.

[0155] The obtained precursor was heat-treated at a heating rate of 10° C. / min and a temperature of 1010° C. for 2 h to obtain the barium calcium titanate powder of Example 2.

[0156] The test results in Table 4 were obtained through X-ray fluorescence spectroscopy analysis, specific surface area detector, X-ray diffractometer, etc.:

[0157] Table 4 Test results of barium calcium titanate powder obtained in Example 2

[0158]

[0159]

[0160] In Table 4, D (specific surface area) is a particle size value calculated based on the barium calcium titanate particles being spheres.

[0161] The samples of Example 2 were subjected to X-ray diffraction testing and TEM-EDS element mapping testing. The X-ray diffraction spectra showed that both samples contained only barium calcium titanate, without impurities such as calcium titanate, calcium hydroxide or calcium carbonate. The TEM-EDS element mapping test results showed that the calcium doping in both samples was uniform.

[0162] Example 3:

[0163] Barium calcium titanate precursors 3-1, 3-2, 3-3, 3-4, and 3-5 were synthesized using the same synthesis method as in Example 2 with different calcium doping concentrations, and their corresponding y values ​​were 1.0%, 3.0%, 5.0%, 10.0%, and 15.0%, respectively. Each precursor was then heat treated at a heating rate of 10°C / min, a heat treatment temperature of 1000°C, and a heat treatment time of 2 hours to obtain barium calcium titanate powders 3-1, 3-2, 3-3, 3-4, and 3-5.

[0164] The test results in Table 5 were obtained through X-ray fluorescence spectroscopy analysis, specific surface area detector, X-ray diffractometer, etc.:

[0165] Table 5 Test results of barium calcium titanate powder obtained in Example 3

[0166]

[0167]

[0168] In Table 5, D (specific surface area) is a particle size value calculated based on the barium calcium titanate particles being spheres.

[0169] X-ray diffraction and TEM-EDS element mapping tests were performed on the five samples in Example 3. The X-ray diffraction spectra showed that the five samples contained only barium calcium titanate, without impurities such as calcium titanate, calcium hydroxide, or calcium carbonate. The TEM-EDS element mapping test results showed that the Ca doping in the five samples was uniform.

[0170] Comparative Example 1:

[0171] 5 L of a 1.2 mol / L TiCl4 solution was poured into a four-necked flat-bottom flask, heated to 104°C, and hydrolyzed at 104°C for 60 min. The solution was then cooled to room temperature at a rate of 2°C / min. An anion exchange resin was used to remove impurities from the resulting solution. The ratio of the anion exchange resin to the solution was 4210 g:1 L. When the pH value of the solution reached 3.5, the impurity removal was stopped. The solution was then concentrated using a hollow fiber membrane to obtain a titanium dioxide suspension with a mass concentration of 15.02%. The specific surface area and crystal form of the titanium dioxide were shown in Table 6:

[0172] Table 6 Specific surface area and crystal form test results of titanium dioxide in Comparative Example 1

[0173] <![CDATA[Specific surface area [m 2 / g]]]> Brookite [wt%] Anatase [wt%] Rutile [wt%] 93 53.24 20.45 26.31

[0174] Then, barium calcium titanate was synthesized according to the same steps as in Example 2 to obtain Ba 0.9560 Ca 0.0503The barium calcium titanate precursor represented by TiO3 (wherein x=0.9451, y=0.0503, z=0.0109) meets the requirements of formula (I).

[0175] Figure 6 The XRD pattern of the barium calcium titanate precursor of Comparative Example 1 is shown in FIG. Figure 6 As shown in the figure, in addition to containing barium calcium titanate, characteristic peaks of calcium titanate appear near 33° and 47.5° in 2θ, indicating that calcium titanate impurities are produced in this sample.

[0176] Comparative Example 2:

[0177] A titanium dioxide suspension was prepared using the method in Example 2 to obtain a titanium dioxide suspension with a mass concentration of 15.3%, and then barium calcium titanate was synthesized. Unlike Example 2, in Comparative Example 2, all the barium source was added in step A) to synthesize barium titanate, and in step B)) a calcium source was added to react to obtain Ba 0.9562 Ca 0.0504 A barium calcium titanate precursor represented by TiO3 (where x = 0.9562, y = 0.0504, and z = 0) was prepared. Because the entire barium source was used in the synthesis in step A), step C was eliminated. Testing of the barium calcium titanate precursor revealed that the X-ray diffraction spectrum revealed that the sample contained only barium calcium titanate, with no impurities such as calcium titanate, calcium hydroxide, or calcium carbonate.

[0178] The precursor obtained in Comparative Example 2 was heat treated in the same manner as in Example 2. The test results shown in Table 7 were obtained through X-ray fluorescence spectrometry analysis, specific surface area detector, and X-ray diffractometer.

[0179] Table 7 Test results of barium calcium titanate powder obtained in Comparative Example 2

[0180]

[0181] In Table 7, D (specific surface area) is a particle size value calculated based on the barium calcium titanate particles being spheres.

[0182] The unit cell volume V=64.03 Å3, which is higher than that of the sample in Example 2 and does not meet the unit cell volume requirement of claim 2. This indicates that part of the calcium in the barium calcium titanate prepared by this feeding method does not enter the barium titanate lattice. Although this part of calcium can be detected during component testing, when prepared into MLCC components, this part of calcium will not have the ability to improve the reduction resistance, but will reduce the dielectric constant.

[0183] Comparative Example 3

[0184] A titanium dioxide suspension was prepared using the method in Example 2 to obtain a titanium dioxide suspension with a mass concentration of 15.3%, and then barium calcium titanate was synthesized. The difference from Example 2 is that in step A), the barium source and the calcium source were added simultaneously to synthesize barium calcium titanate, eliminating steps B) and C). After synthesis, the formula Ba 0.9557 Ca 0.0502 Barium calcium titanate precursor represented by TiO3 (where x=0.9557, y=0.0502, z=0).

[0185] Figure 7 The XRD pattern of the barium calcium titanate precursor of Comparative Example 3 is shown in FIG. Figure 7 As shown, in addition to the characteristic peaks of barium calcium titanate, it also contains characteristic peaks of calcium titanate impurities, indicating that when the barium source and calcium source are fed into the synthesis at the same time, the calcium source also reacts with titanium dioxide to generate calcium titanate impurities while synthesizing barium calcium titanate.

[0186] Comparative Example 4

[0187] A titanium dioxide suspension was prepared using the method in Example 2 to obtain a titanium dioxide suspension with a mass concentration of 16.5%, and then barium calcium titanate was synthesized. Unlike Example 2, the molar concentration of the sodium hydroxide solution is lower. When preparing the sodium hydroxide solution, a pH meter was used to monitor the pH value, and the pH of the prepared sodium hydroxide solution was adjusted to 10.9, and then the synthesis was carried out. After the synthesis, it was confirmed by testing that Ba / Ti=0.9549, Ca / Ti=0.0503, and the formula Ba was obtained. 0.9549 Ca 0.0503 TiO3 is a barium calcium titanate precursor. Figure 8 The XRD pattern of the barium calcium titanate precursor of Comparative Example 4 is as follows: Figure 8 As shown, in addition to the characteristic peak of calcium barium titanate, it also contains characteristic peaks of impurities such as calcium titanate and barium carbonate.

[0188] Comparative Example 5

[0189] The titanium dioxide suspension was prepared using the method in Example 2 to obtain a titanium dioxide suspension with a mass concentration of 16.5%, and then barium calcium titanate was synthesized. Unlike Example 2, the calcium doping concentration was increased in Comparative Example 5. By increasing the amount of calcium source, the calcium doping concentration reached 20%, and the formula Ba was obtained. 0.8045 Ca 0.2012 TiO3 is a barium calcium titanate precursor. Figure 9 The XRD pattern of the barium calcium titanate precursor of Comparative Example 5 is as follows: Figure 9 As shown, in addition to the characteristic peaks of barium calcium titanate, there are also impurity peaks of calcium hydroxide, indicating that the input amount of calcium source has exceeded the solid solubility limit, and the excess part remains in the solution in the form of calcium hydroxide.

[0190] The above embodiments are intended only to facilitate understanding of the methods and core concepts of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is intended to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A calcium barium titanate powder having the chemical formula shown in formula (I): Ba x+z Approx. y TiO3(Ⅰ); In formula (I), y is the molar ratio content of Ca element, where 0 < y ≤ 0.15, and 0.98 ≤ x + y + z ≤ 1.015; Under the condition of 25 ± 3 °C, the unit cell volume V of the calcium barium titanate powder measured by XRD satisfies formula (1): V ≤ 64.3 - 6.6 × y (1); In formula (1), 0 < y ≤ 0.

15.

2. The barium calcium titanate powder according to claim 1, characterized in that The FWHM of the (110) crystal plane of the calcium barium titanate powder is ≤ 0.40°, and the FWHM of the (111) crystal plane is ≤ 0.30°.

3. The preparation method of the calcium barium titanate powder according to claim 1 or 2, comprising the following steps: A) Mix a part of the barium source with a strong alkali solution, heat the obtained mixed solution, then mix it with the titanium source solution, and react to obtain a product solution containing barium titanate shown in formula (II); Ba x TiO3 formula (Ⅱ); In formula (II), 0.85 ≤ x < 1.00; B) Mix the product solution containing barium titanate shown in formula (II) with a calcium source and react to obtain a calcium barium titanate intermediate shown in formula (III): Ba x Ca y TiO3 formula (III); In formula (III), 0 < y ≤ 0.15, 0.85 < x + y ≤ 1.00; C) React the calcium barium titanate intermediate shown in formula (III) with the remaining barium source, and after the reaction, obtain a calcium barium titanate precursor shown in formula (I); Ba x+z Ca y TiO3 formula (Ⅰ); In formula (I), 0 < y ≤ 0.15, z > , 0.98 ≤ x + y + z ≤ 1.

015.

4. The preparation method according to claim 3, characterized in that After step C), it further includes: D) Bake the calcium barium titanate precursor shown in formula (I) to obtain a calcium barium titanate powder having the chemical formula shown in formula (I).

5. The preparation method according to claim 3, characterized in that The barium source includes at least one of barium hydroxide octahydrate, barium hydroxide monohydrate, anhydrous barium hydroxide, barium chloride, barium chlorate, barium acetate, barium nitrate, and barium oxide.

6. The preparation method according to claim 3, characterized in that In step A), the pH value of the strong alkali solution is ≥ 12; The strong alkali includes lithium hydroxide, sodium hydroxide, potassium hydroxide, or quaternary ammonium base.

7. The preparation method according to claim 3, characterized in that In step A), the titanium source includes at least one of titanium tetrachloride solution, titanium hydroxide suspension, hydrated titanium dioxide suspension, titanium oxychloride, and titanium dioxide suspension; The specific surface area of ​​the powder of the titanium dioxide suspension after drying is 50 to 200 m 2 / g, primary particle size is 8-30nm; In the titanium dioxide suspension, the crystal form requirements of titanium dioxide include: the mass content of rutile is ≤ 20%, and the rest is at least one of anatase and brookite.

8. The preparation method according to claim 3, characterized in that The calcium source includes at least one of calcium hydroxide powder, calcium chloride powder, and calcium oxide powder.

9. A dielectric material, characterized in that The preparation raw material of the dielectric material includes the calcium barium titanate powder according to any one of claims 1 to 2 or the calcium barium titanate powder prepared by the preparation method according to any one of claims 3 to 8.

10. A ceramic capacitor, characterized in that: The preparation raw material of the ceramic capacitor includes the calcium barium titanate powder according to any one of claims 1 to 2 or the calcium barium titanate powder prepared by the preparation method according to any one of claims 3 to 8.

11. A slurry, characterized in that: The preparation raw material of the slurry includes the calcium barium titanate powder according to any one of claims 1 to 2 or the calcium barium titanate powder prepared by the preparation method according to any one of claims 3 to 8.

12. An original sheet, characterized in that: The preparation raw material of the green sheet includes the calcium barium titanate powder according to any one of claims 1 to 2 or the calcium barium titanate powder prepared by the preparation method according to any one of claims 3 to 8.

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