Preparation method and application of barium calcium titanate powder

Abstract

The present invention relates to the field of inorganic functional materials, and provides a preparation method and application of barium calcium titanate powder. The preparation method of the barium calcium titanate powder comprises the following steps: preparing a barium solution, weighing a certain amount of calcium source and adding it to the barium solution, weighing a certain amount of titanium dioxide powder and slowly adding it to the mixed solution, dripping a mineralizer into the mixed solution, adjusting the pH value of the solution, transferring the mixed solution to a reactor for hydrothermal reaction, cooling to room temperature after the reaction, opening the reactor, washing, filtering and drying the hydrothermal reaction product with deionized water and acetic acid solution, and obtaining white barium calcium titanate powder. The present invention adopts the above-mentioned hydrothermal preparation method, and the raw materials are easy to obtain, the preparation cost is low, the tetragonality is high, the crystallinity is good, there is no impurity phase, and the particle size is small. The barium calcium titanate powder synthesized by the present invention can meet the demand of the electronic ceramic industry for high-quality barium calcium titanate, and can be applied to multilayer ceramic capacitors (MLCC).

Description

Technical Field

[0001] The invention belongs to the field of inorganic functional materials, and specifically relates to a preparation method of calcium barium titanate powder and application thereof. Background Art

[0002] With the development of the 5G era, multilayer ceramic capacitors (MLCC), known as "industrial rice", are one of the most important electronic components. Their usage is increasing day by day. In order to meet the development of MLCC miniaturization and high-temperature applications, higher requirements are put forward for MLCC design. Barium titanate (BaTiO3) is the main base material of MLCC ceramics. In order to meet the needs of MLCC, the performance of BaTiO3 is usually improved by doping. Among them, Ca-doped BaTiO3-based (BaTiO3) 1-X Ca x TiO3, BCT) is one of the base materials of X8R high temperature MLCC. With the increasing demand for miniaturization and high temperature application of MLCC devices, the demand for high-purity ultrafine powder raw materials is also increasing. Therefore, it is very important to prepare Ca-doped BaTiO3 powder with high tetragonality, good crystallinity, no impurities, small particle size and no agglomeration.

[0003] The traditional method for preparing Ca-doped BaTiO3 powder is the solid phase method. However, the powder prepared by the solid phase method has large particle size, serious agglomeration, and a large number of impurities, which are not suitable for use in MLCC. Therefore, it is still very challenging to synthesize a Ca-doped BaTiO3 powder that can meet the needs of MLCC. Due to the needs of MLCC, it is urgent to develop and synthesize Ca-doped BaTiO3 powder (barium calcium titanate powder) with advantages such as high tetragonality, high crystallinity, and small particle size. Summary of the invention

[0004] In order to solve the problems of poor tetragonality, low crystallinity and large particle size of Ca-doped BaTiO3 powder in the prior art, the present invention provides a method for preparing barium calcium titanate powder.

[0005] The preparation method of the barium calcium titanate powder comprises the following steps:

[0006] S1: Preparation of barium calcium titanate precursor: prepare a barium solution with a barium source concentration of 1-4 mol / L, weigh the calcium source and the titanium source according to the molar ratio of the barium source, calcium source and titanium source (Ba+Ca) / Ti≥1, and add them to the barium solution.

[0007] S2: Hydrothermal synthesis: transfer the calcium barium titanate precursor to a reactor, add a mineralizer with a concentration of ≥0.5 mol / L, adjust the pH of the mixed solution to ≥12, control the filling rate of the reactor to 60%-70%, and carry out hydrothermal reaction at a temperature of 180-240°C for 24-48h. After the reaction is completed, cool to room temperature, open the reactor, and obtain a calcium barium titanate suspension.

[0008] S3: acid-washing and water-washing the barium calcium titanate suspension, drying the washed product in an oven, grinding it, and sieving it to obtain the barium calcium titanate powder.

[0009] Furthermore, the barium source is one or more of barium hydroxide octahydrate, barium chloride dihydrate, barium acetate and barium nitrate.

[0010] Furthermore, the calcium source is one of calcium oxide, calcium chloride, calcium acetate and calcium hydroxide, and the doping amount of the calcium source ranges from 1.5% to 12%.

[0011] Furthermore, the titanium source is a powder with a uniform particle size of any value between 10 nm and 100 nm, and the titanium source is one or more of anatase and rutile crystal forms.

[0012] Furthermore, the mineralizer is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water, and the molar concentration of the mineralizer is greater than 1 mol / L.

[0013] Furthermore, the washing method is suction washing or centrifugal washing.

[0014] Furthermore, the washed product is placed in an oven at 60-80°C for 12-24 h.

[0015] An object of the present invention is to provide a barium calcium titanate powder, wherein the barium calcium titanate powder is prepared according to any of the above methods for preparing barium calcium titanate powder.

[0016] An object of the present invention is to provide an application of barium calcium titanate powder in multilayer ceramic capacitors in electronic components.

[0017] The present invention adopts a preparation method of barium calcium titanate powder to prepare Ca-doped BaTiO3 powder, the raw materials are easily available, the preparation cost is low, the reaction is sufficient, the operation is simple, the product has high tetragonality, good crystallinity, no impurities, small particle size, uniform distribution, and an average particle size of about 150 nm. Combining the above advantages, the barium calcium titanate powder synthesized by the present invention can meet the demand of the electronic ceramic industry for high-quality barium calcium titanate, and can be suitable for multilayer ceramic capacitors (MLCC). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a flow chart of the preparation method of barium calcium titanate powder provided by the present invention;

[0019] Figure 2 is a SEM image of barium calcium titanate powder prepared in Example 1 of the present invention;

[0020] Figure 3 is a particle size distribution diagram of barium calcium titanate powder prepared in Example 1 of the present invention;

[0021] Figure 4 is a SEM image of barium calcium titanate powder prepared in Comparative Example 1 of the present invention;

[0022] Figure 5 is a SEM image of barium calcium titanate powder prepared in Comparative Example 2 of the present invention;

[0023] Figure 6 1 is a SEM image of the barium calcium titanate powder prepared in Example 1 of the present invention and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings, but they should not be construed as limiting the applicable scope of the present invention.

[0025] The preparation method of barium calcium titanate powder comprises the following steps:

[0026] S1: Preparation of barium calcium titanate precursor: prepare a barium solution with a barium source concentration of 1-4 mol / L, weigh the calcium source and the titanium source according to the molar ratio of the barium source, calcium source and titanium source (Ba+Ca) / Ti≥1, and add them to the barium solution.

[0027] S2: Hydrothermal reaction synthesis: The barium calcium titanate precursor is transferred to a reactor, a mineralizer with a concentration greater than or equal to 0.5 mol / L is added, the pH of the mixed solution is adjusted to approximately 12, the filling rate of the reactor is controlled to be 60%-70%, and a hydrothermal reaction is carried out at a temperature of 180-240°C for 24-48 h. After the reaction is completed, the mixture is cooled to room temperature, and the reactor is opened to obtain a barium calcium titanate suspension.

[0028] S3: washing and drying: the barium calcium titanate suspension is acid-washed and water-washed, and the washed product is dried in an oven, ground, and sieved to obtain the barium calcium titanate powder.

[0029] In the prior art, the Ca-doped BaTiO3 powder prepared by the solid phase method has a large particle size, a serious agglomeration phenomenon, and a large number of impurities, and is not suitable for use in MLCC. The present invention prepares Ca-doped BaTiO3 powder by a hydrothermal method. In this reaction, the reaction is at the molecular level, which avoids agglomeration during the reaction and can effectively reduce the particle size of the Ca-doped BaTiO3 powder. At the same time, the raw materials are easy to obtain, the preparation cost is low, the method is simple, the operation is simple, the reaction is sufficient, the product has high tetragonality, good crystallinity, no impurities, small particle size, uniform distribution, and an average particle size of about 150 nm. The barium calcium titanate powder synthesized by the present invention can meet the demand of the electronic ceramic industry for high-quality barium calcium titanate, and can be applied to multilayer ceramic capacitors (MLCC).

[0030] Optionally, the barium source is one or more of barium hydroxide octahydrate, barium chloride dihydrate, barium acetate and barium nitrate.

[0031] Optionally, the calcium source is one or more of calcium oxide, calcium chloride, calcium acetate and calcium hydroxide, and the doping amount of the calcium source ranges from 1.5% to 12%.

[0032] Optionally, the titanium source is a powder with a uniform particle size of any value between 10 nm and 100 nm, and the titanium source is one or more of anatase and rutile crystal forms.

[0033] Optionally, the mineralizer is one or more of sodium hydroxide, potassium hydroxide, and ammonia water, the molar concentration of the mineralizer is greater than 1 mol / L, and the amount of the mineralizer is used to adjust the pH of the solution to ≥12.

[0034] Optionally, the washing method is suction washing or centrifugal washing.

[0035] Further, the washed product is placed in an oven at 60-80° C. and dried for 12-24 h.

[0036] The present invention provides a barium calcium titanate powder, which is prepared according to any of the above methods for preparing barium calcium titanate powder.

[0037] The invention provides an application of calcium barium titanate powder in a multilayer ceramic capacitor in an electronic component.

[0038] Example 1

[0039] The present invention adopts the above-mentioned hydrothermal preparation process of barium calcium titanate powder, which comprises the following steps:

[0040] (1) Preparation of barium precursor: Add 11.58 g of barium hydroxide octahydrate into a beaker containing 50 ml of deionized water and heat in a water bath at 85 °C while stirring until the barium hydroxide octahydrate is completely dissolved in the water.

[0041] (2) Preparation of calcium source: According to (Ba+Ca) / Ti=2, weigh 0.445 g of calcium chloride, add it to the barium solution, and stir until it becomes solid.

[0042] (3) Preparation of titanium precursor: After the solution is cooled to room temperature, 1.6 g of 20 nm anatase titanium dioxide is added to the mixed solution of barium and calcium while stirring until the titanium dioxide powder is completely mixed in the solution.

[0043] (4) Synthesis: The mixed solution of barium, calcium and titanium was completely transferred to a 50 ml hydrothermal reactor, and a certain amount of NaOH solution was added to adjust the pH of the mixed solution to ≥ 12. The filling rate of the reactor was 70%, and the hydrothermal reaction was carried out at a temperature of 240 °C for 36 h. After cooling to room temperature, the reactor was opened to obtain a solution of barium calcium titanate.

[0044] (5) Washing: The hydrothermally synthesized barium calcium titanate solution was filtered and washed several times with 50%wt acetic acid and deionized water until the conductivity of the filtrate was 40 µs / cm.

[0045] (6) Drying: The washed product was placed in a glass container and dried in a forced air oven at 80°C for 12 hours. Then, the powder was ground with a mortar and sieved to obtain barium calcium titanate powder. The molecular formula of the barium calcium titanate powder is Ba 0.97 Ca 0.03 TiO3, in which the calcium doping amount is 3%.

[0046] Example 1 The scanning electron microscope (SEM) image and particle size distribution of barium calcium titanate are as follows: Figure 2 , 3 As shown, the average particle size of the sample is about 150nm, the particle size distribution is uniform, the morphology is smooth, and there are no abnormally large particles. Example 1 The X-ray diffraction (XRD) spectrum of barium calcium titanate is shown in Figure x, without other impurities, and at the characteristic peak 2θ=44-46 。 There are obvious split peaks at , which correspond to the (002) and (200) crystal planes of tetragonal barium titanate, c / a=1.0075.

[0047] Example 2

[0048] The present invention adopts the above-mentioned hydrothermal preparation process of barium calcium titanate powder, which comprises the following steps:

[0049] (1) Preparation of barium precursor: Add 9.6 g of barium chloride dihydrate into a beaker containing 50 ml of deionized water and heat in a water bath at 85 °C while stirring until the barium hydroxide octahydrate is completely dissolved in the water.

[0050] (2) Preparation of calcium source: According to (Ba+Ca) / Ti=1, weigh 0.126 g of calcium oxide, add it to the barium solution, and stir until it becomes solid.

[0051] (3) Preparation of titanium precursor: After the solution is cooled to room temperature, 3.2 g of 60 nm anatase titanium dioxide is added to the mixed solution of barium and calcium while stirring until the titanium dioxide powder is completely mixed in the solution.

[0052] (4) Synthesis: The mixed solution of barium, calcium and titanium was completely transferred to a 50 ml hydrothermal reactor, and a certain amount of NaOH solution was added to adjust the pH of the mixed solution to ≥ 12. The filling rate of the reactor was 70%, and the hydrothermal reaction was carried out at 240 °C for 20 h. After cooling to room temperature, the reactor was opened to obtain a solution of barium calcium titanate.

[0053] (5) Washing: The hydrothermally synthesized barium calcium titanate solution was filtered and washed several times with 50%wt acetic acid and deionized water until the conductivity of the filtrate was 40 µs / cm.

[0054] (6) Drying: The washed product was placed in a glass container and dried in a forced air oven at 80°C for 12 hours. Then, the powder was ground with a mortar and sieved to obtain barium calcium titanate powder. The molecular formula of the barium calcium titanate powder is Ba 0.97 Ca 0.03 TiO3, in which the calcium doping amount is 3%.

[0055] Comparative Example 1

[0056] According to Example 1, other conditions remain unchanged, and the hydrothermal reaction temperature is changed to 180°C. The XRD pattern obtained in Comparative Example 1 shows that at the characteristic peak 2θ=44-46 。 The SEM image of Comparative Example 1 shows that the barium calcium titanate has obvious agglomeration phenomenon, the crystal form is incomplete, and the particle size distribution is very uneven.

[0057] Comparative Example 2

[0058] According to Example 2, other conditions remain unchanged, except that the doping amount of calcium in the hydrothermal reaction is 10%, and the molecular formula of the barium calcium titanate powder is Ba 0.9 Ca 0.1 TiO3. The XRD pattern obtained in Comparative Example 2 shows that the characteristic peak 2θ=44-46。 The SEM image of Comparative Example 1 shows that the barium calcium titanate has serious agglomeration phenomenon and the particle size distribution is very uneven.

[0059] In summary, the present invention adopts the above-mentioned hydrothermal preparation process of barium calcium titanate powder to successfully prepare barium calcium titanate powder with high tetragonality, small particle size, uniform particles, and an average particle size of about 150nm, providing a new solution for the production of small particle size and high tetragonality barium calcium titanate. The barium calcium titanate powder synthesized by the present invention can meet the demand of the electronic ceramic industry for high-quality barium calcium titanate and can be applied to multilayer ceramic capacitors (MLCC).

[0060] Final note: Although the embodiments describe the present invention in detail, the embodiments are only used to illustrate the preferred embodiments of the present invention rather than to limit the present invention. Any changes made using the contents of the present invention description and drawings, or directly or indirectly applied to other technical fields, are within the scope of patent protection of the present invention.

Claims

1. A method for preparing barium calcium titanate powder, characterized in that: The following steps are involved: S1: Preparation of barium calcium titanate precursor: prepare a barium solution with a barium source concentration of 1-4 mol / L, weigh the calcium source and the titanium source according to the molar ratio of the barium source, calcium source and titanium source (Ba+Ca) / Ti≥1, and add them to the barium solution; S2: Hydrothermal synthesis: the barium calcium titanate precursor is transferred to a reactor, a mineralizer with a concentration of ≥0.5 mol / L is added, the pH of the mixed solution is adjusted to ≥12, the filling rate of the reactor is controlled to be 60%-70%, and the hydrothermal reaction is carried out at 240°C for 24-48h. After the reaction is completed, the mixture is cooled to room temperature, and the reactor is opened to obtain a barium calcium titanate suspension; S3: acid-washing and water-washing the barium calcium titanate suspension, drying the washed product in an oven, grinding it, and sieving it to obtain the barium calcium titanate powder. Wherein, the calcium source is one or more of calcium oxide, calcium chloride, calcium acetate and calcium hydroxide, and the doping amount of the calcium source is in the range of 1.5%-3%; The titanium source is titanium dioxide in the form of powder with a uniform particle size of any value between 10 nm and 100 nm, and the titanium source is one or more of anatase and rutile crystal forms; The mineralizer is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water, and the molar concentration of the mineralizer is greater than 1 mol / L.

2. The method for preparing barium calcium titanate powder according to claim 1, characterized in that: The barium source is one or more of barium hydroxide octahydrate, barium chloride dihydrate, barium acetate and barium nitrate.

3. The method for preparing barium calcium titanate powder according to claim 1, characterized in that: The washing method is suction washing or centrifugal washing.

4. The method for preparing barium calcium titanate powder according to claim 1, characterized in that: The washed product was placed in an oven at 60-80 °C and dried for 12-24 h.

5. A barium calcium titanate powder, characterized in that: The barium calcium titanate powder is prepared according to the preparation method of any one of claims 1 to 4.

6. Use of the barium calcium titanate powder as claimed in claim 5 in multilayer ceramic capacitors in electronic components.

Images