A method for preparing barium titanate powder

Abstract

The application relates to the technical field of barium titanate preparation, and discloses a preparation method of barium titanate powder, which comprises the following steps: (1) adding 15% ammonia water solution into a stirring tank, weighing a certain amount of TiCl4 and slowly dropping the TiCl4 into the stirring tank, continuously stirring for 1 h, and obtaining a titanium source solution; (2) adding pure water into a heatable stirring tank, continuously stirring, weighing a certain amount of Ba(OH)2.8H2O and putting the Ba(OH)2.8H2O into the stirring tank, heating and raising the temperature to 100 DEG C and keeping for 2 h, using 15% ammonia water solution to adjust the PH to 13.5, and obtaining a barium source solution; (3) slowly adding the titanium source solution into the barium source solution, then transferring the mixed solution into a hydrothermal reaction kettle, then adding a reaction regulator into the reaction kettle, collecting the solid after multiple washing and drying, and high-temperature calcining the solid, so as to obtain the barium titanate powder; and the application has the effect of improving the tetragonal phase content of the barium titanate powder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of barium titanate preparation, and particularly relates to a preparation method of barium titanate powder. BACKGROUND

[0002] Barium titanate is a typical perovskite structure crystal, and is one of important basic raw materials of a sheet type multilayer ceramic capacitor (MLCC). With the development of the MLCC in the direction of miniaturization, thinning, high capacity and the like, higher requirements are put forward for the purity, particle size, dispersibility and the like of the barium titanate powder, and high-end nanometer barium titanate material currently still depends on import, which is a bottleneck restricting the development of high-end MLCC.

[0003] Among a plurality of synthesis methods of the barium titanate powder, the hydrothermal method for synthesizing the barium titanate powder is paid much attention due to its mild reaction condition, small size, controllable particle size, uniform composition and the like of the synthesized barium titanate. 4－ and Ba 2+ When the combination is insufficient and the dehydration is incomplete, the TiO6 octahedron free end retains a hydroxyl group, and in order to maintain electrical neutrality, the hydroxyl group defect and the barium vacancy form a barium titanate crystal defect in a 1:2 relationship, resulting in defects in the barium titanate, and the prepared barium titanate powder has low tetragonal phase purity. SUMMARY

[0004] The present application aims to provide a preparation method of barium titanate powder, which has the effect of improving the tetragonal phase content of the barium titanate powder.

[0005] The above technical purpose of the present application is realized by the following technical scheme, a preparation method of barium titanate powder, comprising the following steps:

[0006] (1) Preparation of a titanium source solution: a 15% ammonia solution is added to a stirring tank, a certain amount of TiCl4 is slowly dropped into the stirring tank, and stirring is continuously performed for 1 h to obtain a titanium source solution;

[0007] (2) Preparation of a barium source solution: pure water is added to a heatable stirring tank, stirring is continuously performed, and a certain amount of Ba(OH)2·8H2O is added to the stirring tank, heating and temperature rising are performed to 100 DEG C for 2 h, 25% ammonia solution is used to adjust the PH to 12.5 to obtain a barium source solution;

[0008] (3) Preparation of barium titanate powder: slowly add the titanium source solution to the barium source solution, continuously stir during the adding process, continuously stir for 1h after the adding is completed, then transfer the mixed solution to a hydrothermal reaction kettle, slowly stir in a closed state, and quickly heat to 80 DEG C, then stop stirring and keep warm for 2h, then add a reaction regulator to the reaction kettle, stir for 60 min, close, heat to 160 DEG C and keep warm for 12h, collect the solid after multiple washing and drying, and then high-temperature calcine the solid to obtain the barium titanate powder.

[0009] Further arrangement of the application is that the preparation method of the reaction regulator is that a certain amount of phenolic resin is added to an ethanol solution with a mass fraction of 20%, stirred and dissolved, then a proper amount of barium stearate is added, heated to 60 DEG C and stirred for 30 min to obtain the reaction regulator.

[0010] Further arrangement of the application is that the mass ratio of the phenolic resin, the ethanol and the barium stearate is 3:20:4.

[0011] Further arrangement of the application is that the adding amount of the reaction regulator in the step (3) is 15% of the volume of the titanium source solution.

[0012] Further arrangement of the application is that the molar ratio of titanium in the titanium source solution to barium in the barium source solution is 4:5, and the volume ratio of the titanium source solution to the barium source solution in the step (3) is 1:1.

[0013] Further arrangement of the application is that the temperature of the high-temperature calcination in the step (3) is 1000 DEG C, and the time is 6h.

[0014] The beneficial effects of the application are:

[0015] 1. The application adopts a hydrothermal calcination two-step method to prepare barium titanate powder, first mixes barium source and titanium source according to a certain ratio, performs hydrothermal reaction, washes, filters and dries the obtained precipitate after cooling to obtain a precursor of barium titanate powder, and finally puts the obtained barium titanate powder precursor into a heating furnace for calcination treatment, so that the defects of the powder are eliminated and the tetragonal phase content in the barium titanate powder is improved.

[0016] 2. The application adds TiCl4 in an ammonia solution, and in the reaction process, Ti 4+ First, Ti(OH)4 colloid is generated in an alkaline environment, and under the action of high temperature and pressure, the barium source (Ba 2+ ) can quickly move to the Ti-O group (Ti(OH) x 4-x) surface, i.e. the nucleation site of BaTiO3 crystal, thereby rapidly promoting the growth of crystal nucleus, so ammonia is used as the solvent of titanium source solution and the PH of barium source solution is adjusted to 12.5, under high alkalinity conditions, Ba2 + It is not easy to be substituted, and basically no barium vacancy is generated, so the crystal growth is relatively sufficient, so through the alkaline environment, not only the generation of BaTiO3 can be promoted, but also the hydroxyl defects in the synthesis process can be compensated, the internal defects of barium titanate crystal can be eliminated, and the tetragonal phase content in the barium titanate powder can be further improved.

[0017] 3、The present application adds a reaction regulator after the titanium source solution and the barium source solution react for a period of time, on the one hand, after the phenolic resin is dissolved in the ethanol solution, barium stearate is added, the long-chain alkyl and the benzene ring structure of the phenolic resin are promoted to dissolve the barium stearate through the hydrophobic interaction between them, so that the barium stearate can perform secondary barium compensation on the barium titanate particles to repair the barium vacancy defects of the barium titanate material, after the secondary barium compensation treatment, the barium vacancy defect concentration in the crystal can be reduced, the crystal structure stability can be improved, the abnormal growth of the powder due to the vacancy disappearance at high temperature can be inhibited, the charge characteristics of the particle surface can also be changed, the mutual attraction between the particles can be reduced to prevent the agglomeration from occurring; on the other hand, the free groups of the ionized phenolic resin and barium stearate and the negative charge on the surface of the barium titanate particles form a specific bond through the Ba bridge, form a protective layer on the surface of the barium titanate particles through the ion coordination combination or the hydrogen bond, the protective layer plays a role of growth inhibitor to limit the growth of the barium titanate particles at high temperature, and also plays a role of isolation between the barium titanate particles to avoid the fusion growth between the barium titanate particles at high temperature, and the protective layer can slowly decompose, carbonize and oxidize with the temperature rising in the high-temperature calcination process, without solid-phase residue; in summary, through the addition of the reaction regulator in the reaction process, not only the secondary barium compensation through the barium stearate can repair the barium vacancy defects of the barium titanate material, inhibit the abnormal growth of the particles in the subsequent calcination process, and avoid the agglomeration, but also the interaction between the phenolic resin, ethanol and barium stearate promotes the dissolution, so that the free groups after ionization can form a protective layer on the surface of the barium titanate particles to further inhibit the abnormal growth of the particles in the calcination process, avoid the agglomeration, and ensure that the barium titanate powder after high-temperature calcination has the advantages of good dispersibility, small particle size, uniform composition and high tetragonal phase content, to meet the application requirements of high-end MLCC.

[0018] 4、The barium titanate powder prepared by the present application has good dispersibility, small particle size, uniform composition, high tetragonality, and has good application prospect. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] 1. Experimental Procedure

[0021] Example 1

[0022] (1) Preparation of titanium source solution: Add pure water to a stirring tank, weigh a certain amount of TiCl4 and slowly add it dropwise, and stir continuously for 1 hour to obtain a titanium source solution of 0.8 mol / L;

[0023] (2) Preparation of barium source solution: Add pure water to a heatable stirred tank, stir continuously, and weigh out a certain amount of Ba(OH)2·8H2O and add it to the tank. Heat the tank to 100℃ and keep it for 2 hours to obtain a 1.0 mol / L barium source solution.

[0024] (3) Preparation of reaction regulator: A certain amount of phenolic resin is added to a 20% ethanol solution and stirred to dissolve. Then, an appropriate amount of barium stearate is added, and the mixture is heated to 60°C and stirred for 30 minutes to obtain the reaction regulator. The mass ratio of phenolic resin, ethanol and barium stearate is 3:20:4.

[0025] (4) Preparation of barium titanate powder: The titanium source solution was slowly added to an equal volume of barium source solution, and the mixture was stirred continuously during the addition process. After the addition was completed, the mixture was stirred for 1 hour. Then the mixture was transferred to a hydrothermal reactor, sealed and slowly stirred, and the temperature was rapidly raised to 80°C. After stirring was stopped, the temperature was maintained for 2 hours. Then, 15% of the volume fraction of the titanium source solution was added to the reactor and stirred for 30 minutes. The reactor was sealed, heated to 160°C and maintained for 12 hours. After multiple washing and drying, the solid was collected. The solid was then calcined at 1000°C for 6 hours to obtain barium titanate powder.

[0026] It should be noted that the pressure of the hydrothermal reactor is always controlled at 1.6 to 1.7 MPa in step (4).

[0027] Example 2

[0028] (1) Preparation of titanium source solution: 15% ammonia solution was added to a stirred tank, a certain amount of TiCl4 was weighed and slowly added dropwise, and the mixture was stirred continuously for 1 hour to obtain a 0.8 mol / L titanium source solution.

[0029] (2) Preparation of barium source solution: Add pure water to a heatable stirred tank, stir continuously, and weigh out a certain amount of Ba(OH)2·8H2O and add it to the tank. Heat the tank to 100℃ and keep it for 2 hours. Adjust the pH to 12.5 using 25% ammonia solution to obtain a 1.0 mol / L barium source solution.

[0030] (3) Preparation of barium titanate powder: The titanium source solution was slowly added to an equal volume of barium source solution, and the mixture was stirred continuously during the addition process. After the addition was completed, the mixture was stirred for 1 hour. Then the mixture was transferred to a hydrothermal reactor, sealed and stirred slowly, and the temperature was rapidly increased to 80°C. After stirring was stopped and the temperature was maintained for 2 hours, the temperature was increased to 160°C and maintained for 12 hours. After multiple washing and drying, the solid was collected. The solid was then calcined at 1000°C for 6 hours to obtain barium titanate powder.

[0031] It should be noted that the pressure of the hydrothermal reactor is always controlled at 1.6 to 1.7 MPa in step (3).

[0032] Example 3

[0033] (1) Preparation of titanium source solution: 15% ammonia solution was added to a stirred tank, a certain amount of TiCl4 was weighed and slowly added dropwise, and the mixture was stirred continuously for 1 hour to obtain a 0.8 mol / L titanium source solution.

[0034] (2) Preparation of barium source solution: Add pure water to a heatable stirred tank, stir continuously, and weigh out a certain amount of Ba(OH)2·8H2O and add it to the tank. Heat the tank to 100℃ and keep it for 2 hours. Adjust the pH to 12.5 using 25% ammonia solution to obtain a 1.0 mol / L barium source solution.

[0035] (3) Preparation of reaction regulator: A certain amount of phenolic resin is added to a 20% ethanol solution and stirred to dissolve. Then, an appropriate amount of barium stearate is added, and the mixture is heated to 60°C and stirred for 30 minutes to obtain the reaction regulator. The mass ratio of phenolic resin, ethanol and barium stearate is 3:20:4.

[0036] (4) Preparation of barium titanate powder: The titanium source solution was slowly added to an equal volume of barium source solution, and the mixture was stirred continuously during the addition process. After the addition was completed, the mixture was stirred for 1 hour. Then the mixture was transferred to a hydrothermal reactor, sealed and slowly stirred, and the temperature was rapidly raised to 80°C. After stirring was stopped, the temperature was maintained for 2 hours. Then, 15% of the volume fraction of the titanium source solution was added to the reactor and stirred for 30 minutes. The reactor was sealed, heated to 160°C and maintained for 12 hours. After multiple washing and drying, the solid was collected. The solid was then calcined at 1000°C for 6 hours to obtain barium titanate powder.

[0037] It should be noted that the pressure of the hydrothermal reactor is always controlled at 1.6 to 1.7 MPa in step (4).

[0038] Comparative Example 1

[0039] (1) Preparation of titanium source solution: Add pure water to a stirring tank, weigh a certain amount of TiCl4 and slowly add it dropwise, and stir continuously for 1 hour to obtain a titanium source solution of 0.8 mol / L;

[0040] (2) Preparation of barium source solution: Add pure water to a heatable stirred tank, stir continuously, and weigh out a certain amount of Ba(OH)2·8H2O and add it to the tank. Heat the tank to 100℃ and keep it for 2 hours to obtain a 1.0 mol / L barium source solution.

[0041] (3) Preparation of barium titanate powder: The titanium source solution was slowly added to an equal volume of barium source solution, and the mixture was stirred continuously during the addition process. After the addition was completed, the mixture was stirred for 1 hour. Then the mixture was transferred to a hydrothermal reactor, sealed and slowly stirred, and the temperature was rapidly raised to 80°C. After stirring was stopped and the temperature was maintained for 2 hours, a reaction regulator of 15% of the volume fraction of the titanium source solution was added to the reactor, stirred for 30 minutes, sealed, heated to 160°C and maintained for 12 hours. After multiple washing and drying, barium titanate powder was collected.

[0042] It should be noted that the pressure of the hydrothermal reactor is always controlled at 1.6 to 1.7 MPa in step (3).

[0043] 2. Characterization methods for barium titanate powder

[0044] (1) Morphology and microstructure characterization

[0045] The surface morphology and particle size of the powder generated by the reaction were characterized by field emission scanning electron microscopy (SEM). Then, the average size D of the particles in the SEM images was calculated by statistical analysis using ImageJ software. SEM .

[0046] (2) Specific surface area (S) measurement

[0047] The specific surface area of ​​the powder is measured using a specific surface area and pore size analyzer, and then the agglomeration coefficient (AF) of the powder is calculated.

[0048] (3) Particle size distribution measurement

[0049] The particle size distribution of barium titanate powder was characterized using a laser particle size and potential analyzer, and then the particle size distribution non-uniformity coefficient (MD) was calculated.

[0050] (4) Barium titanate lattice constant and tetragonality value (c / a)

[0051] X-ray powder diffraction (XRD) can be used to characterize whether the synthesized barium titanate powder is a pure phase, and then the tetragonal phase content of BaTiO3 crystals can be calculated.

[0052] 3. Experimental Results

[0053] Table 1

[0054] [00000D SEM ]]> AF MD c / a Example 1 145 1.25 0.45 1.0094 Example 2 342 1.65 0.63 1.0065 Example 3 132 1.10 0.41 1.0108 Comparative Example 1 125 1.24 0.56 1.0044

[0055] A comparison of Example 3 and Comparative Example 1 shows that the tetragonal phase content of the powder increased from 1.0044 to 1.0108, while the inhomogeneity coefficient MD decreased from 0.56 to 0.41 and the agglomeration coefficient AF decreased from 1.24 to 1.10. This indicates that by adjusting the alkaline environment of the titanium source solution and the barium source solution, and adding a reaction regulator, the barium titanate powder can be calcined at high temperature to significantly increase the tetragonal phase content without significantly increasing the powder particle size, while reducing the inhomogeneity coefficient and agglomeration coefficient. This results in barium titanate powder with good dispersibility, small particle size, uniform composition, and high tetragonal phase content, meeting the application requirements of high-end MLCCs.

[0056] A comparison of Examples 1 and 3 shows that the tetragonal phase content of the powder obtained by reacting titanium source solution and barium source solution in an alkaline environment is significantly increased, while the non-uniformity coefficient MD and agglomeration coefficient AF are reduced. This indicates that the alkaline environment can not only promote the formation of BaTiO3, but also compensate for the hydroxyl defects in the synthesis process, eliminate internal defects in barium titanate crystals, and further increase the tetragonal phase content in barium titanate powder.

[0057] A comparison of Examples 2 and 3 shows that adding a reaction regulator during the hydrothermal reaction of barium titanate can significantly reduce the particle size of the obtained barium titanate powder while increasing the content of the tetragonal phase. This indicates that adding the reaction regulator can perform secondary barium replenishment and form a protective layer on the surface of the barium titanate particles, thereby improving the stability of the crystal structure, inhibiting the abnormal particle growth caused by the disappearance of vacancies at high temperatures, and acting as an isolation agent between particles to prevent the fusion and growth of barium titanate particles at high temperatures. This avoids the problems of poor dispersibility, significant increase in particle size, and severe agglomeration caused by high-temperature calcination, resulting in barium titanate powder with high tetragonal phase content, good dispersibility, and uniform composition.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing barium titanate powder, characterized in that, Includes the following steps: (1) Preparation of titanium source solution: Add 15% ammonia solution to a stirring tank, weigh a certain amount of TiCl4 and slowly add it dropwise, and stir continuously for 1 hour to obtain titanium source solution; (2) Preparation of barium source solution: Add pure water to a heatable stirred tank, stir continuously and weigh a certain amount of Ba(OH)2·8H2O into it, heat and raise the temperature to 100℃ and keep it for 2h, and adjust the pH to 12.5 with 25% ammonia solution to obtain barium source solution; (3) Preparation of barium titanate powder: The titanium source solution is slowly added to the barium source solution, and the mixture is stirred continuously during the addition process. After the addition is completed, the mixture is stirred for 1 hour. Then the mixture is transferred to a hydrothermal reactor, sealed and stirred slowly, and the temperature is rapidly raised to 80°C. Then the stirring is stopped and the temperature is maintained for 2 hours. Then the reaction regulator is added to the reactor, stirred for 60 minutes, sealed, heated to 160°C and maintained for 12 hours. After multiple washing and drying, the solid is collected and then the solid is calcined at high temperature to obtain the barium titanate powder. The reaction regulator is prepared by adding a certain amount of phenolic resin to a 20% ethanol solution, stirring to dissolve, then adding an appropriate amount of barium stearate, heating to 60°C and stirring for 30 minutes to obtain the reaction regulator. The mass ratio of the phenolic resin, the ethanol, and the barium stearate is 3:20:

4.

2. The method for preparing barium titanate powder according to claim 1, characterized in that: In step (3), the amount of reaction regulator added is 15% of the volume of the titanium source solution.

3. The method for preparing barium titanate powder according to claim 1, characterized in that: The molar ratio of titanium in the titanium source solution to barium in the barium source solution is 4:5, and the volume ratio of the titanium source solution to the barium source solution in step (3) is 1:

1.

4. The method for preparing barium titanate powder according to claim 1, characterized in that: The high-temperature calcination in step (3) is carried out at a temperature of 1000℃ for 6 hours.