KR100933094B1 - Method for producing ultrafine barium titanate using solid phase reaction method - Google Patents

Abstract

The present invention relates to a method for producing BaTiO ₃ by using a solid phase reaction, and specifically, has a uniform size by heat-treating a raw material containing a seed material which is a Ba precursor, a Ti precursor, an alkali salt, and a BaTiO ₃ . The ultrafine BaTiO ₃ of submicron is produced.

The manufacturing method of the present invention has the advantage that BaTiO ₃ powder of narrow particle size distribution is prevented to prevent the formation of coarse particles, and even during low temperature heat treatment, the nucleation and growth of BaTiO ₃ is actively performed and at the same time, the particle aggregation is caused by the attraction between particles. This is advantageous in that the ultrafine BaTiO ₃ powder composed of single crystals having a single particle is manufactured in a uniform size. In addition, the average particle size can be controlled in submicron units while maintaining a narrow particle size distribution by simply controlling the heat treatment temperature or heat treatment time, and there is an advantage in that BaTiO ₃ powder having a stoichiometric ratio is manufactured. BaTiO ₃ powder has the advantage of very excellent dielectric properties and high crystallinity. In addition, the manufacturing process is simple, eco-friendly, economical manufacturing method that does not discharge the waste liquid and at the same time can be mass production, there is an advantage that BaTiO ₃ is produced in accordance with the characteristics required for BaTiO ₃ powder for MLCC or PTCR.

Barium Titanate, Solid State Reaction, Alkali Salt, Seed

Description

Fabrication Method of Barium titanate Using Solid State Reaction

The present invention relates to a method for producing barium titanate using a solid phase reaction method.

BaTiO ₃ powder is a ferroelectric with perovskite structure and is used as the main raw material of MLCC and PTCR due to its high dielectric constant, thermal stability and low price. In recent years, due to the miniaturization of components due to the thin and light miniaturization of electronic and communication devices and the high integration of electronic circuits, powders used in this field also have high crystallinity, and powders having high purity and submicron size particles are required. It is becoming.

In general, solid phase reaction method, oxalate method, hydrothermal synthesis method and the like are commercially used to prepare BaTiO ₃ powder. The solid phase reaction method is a commercially used method to produce BaTiO ₃ powder by diffusion control reaction at 900 ~ 1400 ℃ using BaCO ₃ and TiO ₂ as starting materials. This method has the advantage of low manufacturing cost, but it is not suitable for MLCC due to the disadvantage that the minimum size of the powder to be prepared is 0.5㎛ and the particle size distribution is uneven.

Oxalate salt method has the advantage of relatively simple chemical process and high yield. However, since the control of particle size is difficult and the stability of barium oxalate and titanium oxalate is high, the preparation of BaTiO ₃ powder having good crystallinity requires the heat treatment at a high temperature, thereby increasing the particle size and causing aggregation between particles.

The hydrothermal synthesis method is excellent in producing uniform and ultrafine particles compared with other manufacturing methods. It also eliminates the need for additional heat treatment and milling. However, it is expensive compared to the solid phase reaction method, the reaction time is long, it is difficult to control the concentration of titanium oxide hydrate, it is difficult to control the atomic ratio of barium and titanium, and it requires enormous waste water because 120 to 1000 moles of water are required for 1 mole of titanium. There is a drawback of poor efficiency due to processing problems.

An object of the present invention for solving the above problems is to provide a method for producing ultrafine BaTiO ₃ powder having a narrow particle size distribution (uniform particle size) and submicron size using a solid phase reaction method, excellent dielectric properties To provide a method for producing ultrafine BaTiO ₃ powder having a high crystallinity, a solid shape,

BaTiO ₃ powder production method according to the present invention is characterized in that BaTiO ₃ powder is prepared by heat-treating a raw material containing a seed material (Ba precursor, Ti precursor, alkali salt and BaTiO ₃ seed).

Preferably, the method for preparing BaTiO ₃ powder according to the present invention comprises the steps of: a) mixing a raw material containing a seed compound containing a Ba compound, a Ti compound, an alkali salt, and BaTiO ₃ , followed by heat treatment; And b) wet grinding the heat treated calcined powder after washing.

Specifically, in step a), the Ba precursor, the Ti precursor, the alkali salt and the seed material are quantified and mixed with water, and then the raw materials are mixed and ground through a conventional wet ball mill. The dried raw material after the wet ball mill is heat-treated using a conventional heat treatment furnace to produce BaTiO ₃ powder. During heat treatment, decomposition of Ba precursor and Ti precursor, BaTiO ₃ nucleation, grain growth occurs, and BaTiO ₃ powder (calcined powder) obtained by heat treatment is caused by the attractive force between particles. Aggregation occurs between grains. To solve this problem, washing with distilled water to remove residual alkali salts in the calcined powder heat-treated as in step b), followed by wet grinding using a wet ball mill again. It is preferred that the step be performed.

The average particle size of the seed material BaTiO ₃ is 0.05㎛ ~ 0.5㎛, preferably having a monomodal particle size distribution (unimodal particle size distribution). The seed material decomposes the Ba precursor and the Ti precursor during heat treatment of the raw material and is used to facilitate the nucleation of BaTiO _3. The seed material enables the production of BaTiO ₃ even at a very low heat treatment temperature. In the conventional solid phase reaction for producing BaTiO ₃ , nucleation starts at 1100 ° C. or higher, and grain growth occurs. When seed is used according to the present invention, nucleation of BaTiO ₃ occurs at a lower temperature of 700 ° C. or higher. .

The alkali salt serves as a particle growth inhibitor, and serves to inhibit the growth of particles and the formation of aggregates due to the heat treatment at a high temperature generated in the conventional solid phase reaction method of manufacturing BaTiO ₃ powder. During the heat treatment, the alkali salts do not participate in the reaction and transform into a liquid state to enclose the BaTiO ₃ particles that have already been produced, thereby inhibiting subsequent particle growth.

These seed materials and grain growth inhibitors result in the production of ultrafine BaTiO ₃ powders of very uniform size.

By mixing the seed material and the alkali salt, the grain growth inhibitor, with a Ba precursor and a Ti precursor, by heat treatment, a narrow particle size distribution of BaTiO ₃ powder is prevented from producing coarse particles, thereby nucleating and growing BaTiO ₃ . This active and at the same time prevent the aggregation between the particles can be produced BaTiO ₃ powder consisting of a single crystal single particles. By controlling the simple heat treatment temperature or heat treatment time, the average particle size can be controlled in submicron units, and the narrow particle size distribution (ie uniform particle size) despite the change in the average size of the particles due to the change in the heat treatment temperature or heat treatment time. BaTiO ₃ powders having the same can be prepared.

To this end, the alkali salt is preferably LiCl, NaCl, KCl, LiF, NaF, KF, LiBr, NaBr, KBa, LiI, NaI, KI or a mixed salt thereof, the Ba precursor is barium carbonate (BaCO ₃ ) And the Ti precursor is titanium oxide (TiO ₂ ). In addition, the raw material preferably contains 0.3 to 0.5 mole of the alkali salt with respect to 1 mole of Ba of the Ba compound, and the raw material contains BaTiO ₃ which is the seed material with respect to 1 mole of Ba of the Ba compound. It is preferable to contain 0.05-0.15 mol.

The heat treatment is characterized in that 600 ℃ to 1200 ℃, the average particle size of BaTiO ₃ prepared by using the heat treatment temperature, heat treatment time (1 to 10 hours), or a combination thereof can be adjusted to 0.1㎛ to 0.5㎛ have.

Mixing and grinding of step a) is a wet ball mill for 20 to 50 hours by mixing a raw material having a size of less than a micron or sub-micron with 1 to 10 parts by weight of zirconia balls of 1 to 10 mm based on the weight of the raw material Preferably, the wet grinding of step b) uses a zirconia ball of 1 to 10mm size, the wet ball for 10 to 40 hours by adding 1 to 10 parts by weight of the zirconia ball based on the weight of the heat-treated calcined powder It is preferably carried out by milling.

At this time, after the heat treatment in step (a), washing with water (mixing with distilled water and then performing separation and collection by filtration) to remove alkali salts, which are particle growth inhibitors, is performed. It may be performed four times.

The manufacturing method of the present invention has the advantage that BaTiO ₃ powder of a narrow particle size distribution is prevented to prevent the formation of coarse particles, and the nucleation and growth of BaTiO ₃ is active and at the same time the aggregation between particles is prevented, so that single particles are single crystals. There is an advantage that the ultrafine BaTiO ₃ powder having a uniform size consisting of is prepared. In addition, it is possible to control the average particle size by submicron size while maintaining a narrow particle size distribution by simply controlling the heat treatment temperature or heat treatment time, there is an advantage that BaTiO ₃ powder having a stoichiometric ratio is produced, the produced BaTiO _{3 The} powder has the advantage of having excellent dielectric properties and high crystallinity.

In addition, the manufacturing process is simple, eco-friendly, economical manufacturing method that does not discharge the waste liquid and at the same time can be mass production, there is an advantage that BaTiO ₃ is produced in accordance with the characteristics required for BaTiO ₃ powder for MLCC or PTCR.

(Example 1)

0.1㎛ BaTiO ₃ Produce

After adding 197.3 g of barium carbonate (TERIO CORPORATION, TBSP-3000), 79.9 g of titanium oxide (TERIO CORPORATION, HP (M)), 27.3 g of barium titanate, a seed material, and 37.3 g of KCl, a growth inhibitor, were added to 1000 ml of distilled water. , Wet mixing and grinding for 40 hours at 40rpm using 2kg zirconia ball of 1 ~ 10mm size. The mixed / milled raw materials were dried at 120 ° C. for 24 hours using a dryer, and then placed in a high purity alumina crucible and heat treated at 700 ° C. for 2 hours. The synthetic (calcined) powder was sufficiently washed with distilled water, dried at 120 ° C. for 12 hours, and then added to 1000 ml of distilled water. Then, wet grinding was performed for 40 hours at 40 rpm using 1.2 kg of zirconia balls having a size of 1 to 10 mm. After drying for 12 hours at 120 ℃ to obtain an average particle size of 0.1㎛ BaTiO ₃ .

(Example 2)

0.2㎛ BaTiO ₃ Produce

An average particle size of 0.2 μm BaTiO ₃ was obtained by the same method as Example 1 except that the heat treatment temperature was performed at 800 ° C. for 2 hours, and the synthesis (calcined powder) was wet pulverized for 30 hours.

(Example 3)

0.3 μm BaTiO ₃ Produce

An average particle size of 0.3 μm BaTiO ₃ was obtained by the same method as Example 1 except that the heat treatment temperature was performed at 900 ° C. for 2 hours, and the synthesis (calcined powder) was wet milled for 20 hours.

(Example 4)

0.4 μm BaTiO ₃ Produce

An average particle size of 0.4 μm BaTiO ₃ was obtained by the same method as Example 1 except that the heat treatment temperature was performed at 1000 ° C. for 2 hours, and the synthesis (calcined powder) was wet milled for 10 hours.

In Examples 1 to 4, the ultrafine BaTiO ₃ powder having a uniform particle size was manufactured by controlling the heat treatment temperature, but the average particle size can be controlled by controlling the heat treatment time.

Particle shape, cohesion, average particle size, particle size distribution, etc. of the ultrafine BaTiO ₃ powders prepared in Examples 1 to 4 were observed and measured based on field emission scanning electron micrography (FESEM) images.

1 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 1, Figure 2 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 2, Figure 3 is an ultrafine BaTiO prepared in Example 3 ₃ is a FESEM image of the powder, Figure 4 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 4.

As can be seen in Figures 1 to 4 ultra-fine BaTiO ₃ powder prepared according to the production method of the present invention is to prevent the growth of large particles have a uniform particle size, the particle shape is close to a spherical shape, the average particle according to the heat treatment temperature It can be seen that the size is controlled to 0.1 ~ 0.4㎛.

Figure 5 shows the XRD measurement results of the ultrafine BaTiO ₃ powder prepared in Example 1 (Fig. 5 (a)) to 4 (Fig. 5 (d)), the powder prepared according to the present invention is BaTiO It can be seen that ₃ , and even though the particle size is a submicron ultrafine powder, it can be seen that Ba oxide phase, Ti oxide phase, amorphous phase and other abnormal phase material is not produced, pure crystalline ultra It can be seen that particulate BaTiO ₃ powder is prepared.

The atomic ratio of Ba: Ti in the ultrafine BaTiO ₃ powders prepared in Examples 1 to 4 was dissolved in distilled water by decomposing a predetermined amount of BaTiO ₃ powder into a solution containing sulfuric acid, ammonium sulfate, and nitric acid to form a precipitate. The amount of barium was determined by measuring the weight of the barium sulfate by oxidizing it with heat, decomposing a certain amount of BaTiO ₃ powder into a solution containing sulfuric acid, ammonium sulfate, and nitric acid, and then dissolving it in water to form a precipitate. Again, sulfuric acid and hydrochloric acid were added, and titanium was reduced with aluminum, and the precipitate was titrated with ammonium thiocyanate solution to determine the amount of titanium.

The specific surface area of the ultrafine BaTiO ₃ powders prepared in Examples 1 to 4 was measured by BET, and the prepared BaTiO ₃ powders were formed into a molded body using a mold, followed by sintering at 1250 ° C. for 2 hours, followed by sintering density. The sintering properties of the powders were measured by measuring the dielectric properties, and the dielectric properties were measured at 1.0V and 1 하여 using an LCR meter (MIT model, model name 9216A).

Table 1 below shows the characteristics of the ultrafine BaTiO ₃ powder prepared in Examples 1 to 4.

Table 1

As can be seen from Table 1, it can be seen that the ultrafine BaTiO ₃ powder prepared according to the present invention has a stoichiometric ratio Ba: Ti within a measurement error range, and has excellent sintering characteristics and a high dielectric constant. Able to know.

The ultrafine BaTiO ₃ powder prepared according to the present invention is an ultrafine powder of uniform size with a narrow particle size distribution, its shape is close to a spherical shape, the particle size can be controlled in the submicron unit, and the sintering property is good and the dielectric constant is high. It can be seen that the highly crystalline ultra-fine BaTiO ₃ having a, satisfying all the properties required for BaTiO ₃ powder for MLCC or PTCR.

In the present invention as described above has been described by specific embodiments and limited embodiments and drawings, but this is only provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments, the present invention Those skilled in the art can make various modifications and variations from this description.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

1 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 1,

2 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 2,

3 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 3,

4 is a FESEM image of the ultrafine BaTiO ₃ powder prepared in Example 4,

Figure 5 shows the XRD measurement results of the ultrafine BaTiO ₃ powder prepared in Example 1 (Fig. 5 (a)) to 4 (Fig. 5 (b)).

Claims (11)

A method for producing BaTiO ₃ powder prepared by heat-treating a raw material containing a Ba precursor, a Ti precursor, an alkali salt, and a BaTiO ₃ seed material. The method of claim 1, The manufacturing method of the BaTiO ₃ powder a) mixing and grinding the raw materials, and then performing heat treatment; And b) washing the heat treated calcined powder and then wet grinding; Method for producing a BaTiO ₃ powder prepared including. The method of claim 2, The alkali salt is LiCl, NaCl, KCl, LiF, NaF, KF, LiBr, NaBr, KBa, LiI, NaI, KI or a method for producing BaTiO ₃ powder, characterized in that a mixed salt thereof. The method of claim 3, wherein The seed material BaTiO ₃ is an average particle size of 0.1㎛ ~ 0.5㎛, BaTiO ₃ powder manufacturing method, characterized in that it has a unimodal particle size distribution (unimodal particle size distribution). The method according to any one of claims 1 to 4, The Ba precursor is barium carbonate (BaCO ₃ ), the Ti precursor is a method of producing BaTiO ₃ powder, characterized in that the titanium oxide (TiO ₂ ). The method of claim 5, Ba: Ti molar ratio of the Ba precursor and the Ti precursor is a method of producing a BaTiO ₃ powder, characterized in that 1: 1. The method of claim 5, The raw material is a method for producing BaTiO ₃ powder, characterized in that it contains 0.3 to 0.5 mol of the alkali salt with respect to 1 mol of Ba of the Ba precursor. The method of claim 5, The raw material is a method for producing BaTiO ₃ powder, characterized in that it contains 0.05 to 0.15 mol of BaTiO _{3 as the} seed material with respect to 1 mol of Ba of the Ba precursor. The method of claim 1, The heat treatment is a method for producing BaTiO ₃ powder, characterized in that 600 ℃ to 1200 ℃. The method of claim 2, The wet grinding of step b) is carried out by wet ball milling for 10 to 40 hours using zirconia balls having a size of 1 to 10 mm and adding 1 to 10 parts by weight of the zirconia balls based on the weight of the calcined powder. Method for producing a BaTiO ₃ powder, characterized in that. BaTiO ₃ powder prepared using the method of any one of claims 1 to 4.

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