KR20050063273A - The preparation of barium titanate based powder with dielective composition by oxalate snythesis - Google Patents

Abstract

The present invention relates to a process for the preparation of a compound of barium titanate-based powder by the oxalate method, and more particularly of oxalic acid to a mixed aqueous solution of barium chloride (BaCl ₂ and 2H ₂ O) and titanium tetrachloride (TiCl ₄₎ (H ₂ C ₂ O ₄₎ to barium titanyl oxalate obtained precipitate in an aqueous solution _{[C (BaTiO 2 O 4)} 2 and 4H ₂ O] and then a solution ground to a specific metal-containing additive predetermined ratio by the heat treatment, the particle size distribution as compared with the conventional It is possible to maintain uniform and at the same time the stoichiometric composition of the powder (molar ratio of Ba / M / Ti), and it is possible to manufacture complex barium titanate powder with excellent reduction resistance, so that it is simple and high in productivity. The present invention relates to a method for producing a composite barium titanate-based powder that can be widely used in the manufacture of X7R laminated ceramic capacitors (MLCC), static characteristic thermistors (PTC) and piezoelectric elements.

Description

The preparation of Barium Titanate based powder with dielective composition by oxalate snythesis

The present invention relates to a process for the preparation of a compound of barium titanate-based powder by the oxalate method, and more particularly of oxalic acid to a mixed aqueous solution of barium chloride (BaCl ₂ and 2H ₂ O) and titanium tetrachloride (TiCl ₄₎ (H ₂ C ₂ O ₄₎ to barium titanyl oxalate obtained precipitate in an aqueous solution _{[C (BaTiO 2 O 4)} 2 and 4H ₂ O] and then a solution ground to a specific metal-containing additive predetermined ratio by the heat treatment, the particle size distribution as compared with the conventional It is possible to maintain uniform and at the same time the stoichiometric composition of the powder (molar ratio of Ba / M / Ti), and it is possible to manufacture complex barium titanate powder with excellent reduction resistance, so that it is simple and high in productivity. The present invention relates to a method for producing a composite barium titanate-based powder that can be widely used in the manufacture of X7R laminated ceramic capacitors (MLCC), static characteristic thermistors (PTC) and piezoelectric elements.

Barium titanate powder has been widely used as a raw material for multilayer ceramic capacitors (MLCC), static ceramic capacitors (PCT), and piezoelectric materials for X7R. Such barium titanate powder was conventionally manufactured by sintering titanium dioxide (TiO ₂ ) and barium carbonate (BaCO ₃ ) at a high temperature by a solid phase reaction, but recently miniaturization of MLCC (high dielectric constant composition, dielectric thinning and high lamination). Due to low temperature plasticization, high frequency and high performance, high purity / composition uniformity, fine grain / particle uniformity, non-aggregation / high dispersion, etc. are required. In particular, as the lamination is performed, the internal electrode is converted from Ag-Pd, which is a high-cost raw material, to Ni-based. Therefore, sintering is required in the reducing component to prevent oxidation of the Ni electrode, and the sheet thickness is increased to manufacture a high capacity MLCC. It became thin and required uniform powder of 1 micrometer or less.

However, BaTiO ₃ prepared by the conventional solid-state method is difficult to control the alkali metal (K, Na, etc.) and iron (Fe), which are fatal impurities acting in the reducing component crisis due to the limitation of the starting material used. However, it cannot be used for thinned high capacity MLCCs due to uneven particle size. Recently, the demand for liquid synthesis has increased as a method for preparing powders that can satisfy these characteristics. As the liquid phase method, for example, the coprecipitation method (oxalate method), hydrothermal synthesis method, alkoxide method and the like have been developed, and the use thereof is rapidly increasing.

On the other hand, since the sintering is performed in the reducing component crisis, the degradation of the MLCC and the reduction of the resistivity occur due to the oxygen deficiency of barium titanate (BaTiO ₃ ), which is used as the main raw material. To prevent this, oxides such as manganese (Mn), yttrium (Y), calcium (Ca), zirconium (Zr), holmium (Ho) and magnesium (Mg) are used as additives, but the fundamental oxygen defect of BaTiO ₃ It is not removed.

For this reason, instead of using BaTiO ₃ as the main raw material of MLCC, a method of applying BaMTiO ₃ has been attempted. At this time, the metal (M) is manganese (Mn), magnesium (Mg), calcium (Ca), zirconium (Zr), yttrium (Y), holmium (Ho), dysprosium (Dy), erbium (Er), ytterbium (Yb) ), Hafnium (Hf), lead (Pb), strontium (Sr), niobium (Nb), tantalum (Ta) and the like. Looking at the literature applying BaMTiO ₃ , Japanese Patent Laid-Open No. 2003-165768 proposes a highly reliable dielectric composition by applying (Ba _1-x Ca _x ) _m TiO ₃ , and recently proposed Korean Patent Application No. 2002-0079433 In this paper, Ba (Ti _x Zr _1-x ) O ₃ is used to improve the dielectric life of MLCC.

However, since all of them use BaMTiO ₃ manufactured by a solid-state method that is large in size, non-uniform, and not easy to control impurities, it is difficult to apply them to a Ni electrode MLCC in an actual industrial field. In addition, the liquid crystal manufacturing method of three-component or more, such as BaMTiO _{3 that} is commonly used in the past, the raw material price is high, it is difficult to implement a certain molar ratio reproducibly in mass production, and the crystallinity is low, so it is difficult to implement characteristics Only small quantities are applied to special products and are not commonly used.

Accordingly, the present inventors have tried to prepare a three-component or more complex barium titanate powder having a uniform particle size distribution and easy to implement characteristics, and as a result, an aqueous solution of barium chloride (BaCl ₂ ㆍ 2H ₂ O) and titanium tetrachloride (TiCl ₄ ) Oxal which is heat-treated after mixing and grinding a barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ ㆍ 4H ₂ O] obtained by precipitation in an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) at a predetermined ratio. When the rate method is used, the present inventors have found that a composite barium titanate-based powder having excellent stoichiometry (molar ratio of Ba / M / Ti) and particle size and excellent reduction resistance can be obtained.

Accordingly, the present invention is characterized by providing a composite barium titanate-based powder having not only optimum physical properties but also excellent productivity and process freedom.

In the present invention, a mixed solution of barium chloride (BaCl ₂ ) and titanium tetrachloride (TiCl ₄ ) is added dropwise to an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) to add barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ ㆍ 4H ₂ O) preparing a slurry;

Preparing a composite titaniumyl oxalate powder by wet grinding the mixed barium titanyl oxalate slurry with a metal-containing additive in a form selected from oxides, chlorides and nitrides and drying the slurry;

Pyrolysing the prepared composite titanyl oxalate powder to prepare a composite barium titanate-based (BaMTiO ₃ ) powder; And

Characterized in that the method for producing a composite barium titanate-based powder represented by the following formula comprising the step of regrinding the composite barium titanate-based powder.

[Formula]

(Ba _1-x M _x ) _m (Ti _1-y M _y ) _n O ₃

In the above formula, 0.005 <x + y <0.05 and m / n> 0.98.

The present invention will be described in more detail as follows.

The present invention relates to a method for producing a three-component or more complex barium titanate-based powder using an oxalate method, wherein an aqueous solution of barium chloride (BaCl ₂ ㆍ 2H ₂ O) and titanium tetrachloride (TiCl ₄ ) is used for oxalic acid (H ₂ C ₂ O). ₄ ) A process in which barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ ㆍ 4H ₂ O] obtained by precipitation in an aqueous solution and a specific metal-containing additive are added at a predetermined ratio, mixed and pulverized, followed by heat treatment. It is the biggest feature that it is possible to obtain a composite barium titanate-based powder having excellent stoichiometric composition (molar ratio of Ba / M / Ti) and uniformity of particles and at the same time having excellent reduction resistance.

Referring to the method for producing a composite barium titanate-based powder according to the present invention in more detail as follows.

First, a mixed solution of barium chloride (BaCl ₂ ) and titanium tetrachloride (TiCl ₄ ) is added dropwise to an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) to add barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ ㆍ 4H ₂ O ) Is precipitated, aged, washed with water and filtered to prepare a slurry of barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O).

The aqueous barium chloride solution is used by dissolving BaCl ₂ · 2H ₂ O in water, the preferred concentration range is 0.2 to 2.0 mol / l. The titanium tetrachloride aqueous solution is usually used by diluting the TiCl ₄ solution, the preferred concentration range is 0.2 to 2.0 mol / L. The barium chloride solution and the titanium tetrachloride solution are preferably mixed well so that the barium: titanium element maintains a molar ratio of 1: 1 to 1.5, and more preferably, it is controlled to react to be 1: 1 to 1.1. It is advantageous. It is preferable to use the said oxalic acid aqueous solution which has a density | concentration of 0.2-5.0 mol / L. The reaction temperature of oxalic acid during the reaction is preferably maintained at 50 ~ 90 ℃.

The aging time of 0.5 to 2 hours is advantageous in terms of production unit production during production, and then washed with excess water until the pH of the washing solution is neutral to the barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ 4H ₂ O, BTO) slurry is obtained.

Next, the prepared barium titanyl oxalate slurry is first pulverized, a mixed wet pulverization is performed by adding a metal-containing additive, and then dried to prepare a composite titanyl oxalate powder.

The BTO slurry is first pulverized through a mixing grinder to sufficiently reduce the particle size so that the D ₅₀ is 1 µm or less, and then wet grinding is performed by adding a metal-containing additive.

The metal-containing additive may be used one or two or more compounds in the form selected from oxides, chlorides and nitrides, it is preferable to mix the barium: metal element to maintain a molar ratio of 1: 0.005 to 0.05 and economically advantageous Do.

When the molar ratio of the metal-containing additive added during the mixing exceeds 0.05, the partial large grain growth cannot be controlled in a subsequent pyrolysis process, thereby obtaining a uniform particle size distribution and flattening due to excessive additives during the MLCC manufacturing. Difficult to obtain temperature characteristics. When the molar ratio is less than 0.005, it is difficult to diffuse the additive components, and thus it is difficult to obtain desired reduction resistant powder.

The metal is, for example, manganese (Mn), magnesium (Mg), calcium (Ca), zirconium (Zr), yttrium (Y), holmium (Ho), digprosium (Dy), erbium (Er), ytterbium ( One or two or more selected from Yb), hafnium (Hf), lead (Pb), strontium (Sr), niobium (Nb), and tantalum (Ta) may be used.

In the mixing, a wet mill such as a planetary mill, a ball mill, a beads mill, or the like is used. In the wet milling, the solvent may be deionized water, and the amount of BTO 1 is used. 1-10 weight part is preferable with respect to weight part. The wet grinding time depends on the mixing amount, preferably 10 to 300 minutes. It is preferable to limit the average particle diameter of barium titanyl oxalate after pulverization to 0.1 to 5 탆 in terms of keeping the stoichiometric composition constant.

The drying may be carried out using an oven, a fluidized bed dryer, a spray-dry, or the like under normal conditions.

Next, the composite titanyl oxalate powder is thermally decomposed to prepare a composite barium titanate-based (BaMTiO ₃ ) powder. At this time, it is preferable to make the heating rate about 0.5-10 degreeC / min at the time of thermal decomposition, and to set the holding temperature as 700-1200 degreeC. The reason for limiting the heating rate and the holding temperature is to prevent the excessive growth and to have a uniform particle size distribution.

Finally, the composite barium titanate-based powder obtained above is subjected to a process for regrinding through a grinder. In this case, as a grinder, a dry grinder such as a sprayer, a jet mill, etc., as well as a wet grinder such as a planetary mill, a ball mill, and a beads mill may be used. However, when a wet grinder is used, drying is required in an oven, a fluid bed dryer, a spray-dry, or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Example 1 Preparation of Manganese Barium Titanium Powder

After preparing and measuring TiCl ₄ solution and BaCl ₂ having a purity of 99.9% or more, it was added dropwise to an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) and barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ · 4H ₂ O, below A slurry was prepared by precipitating 'BTO'. The BTO slurry prepared above was aged, filtered and washed to reduce the particle size by first mixing and grinding with a mixed wet mill, and then added with manganese (Mn) in a 0.03 molar ratio to barium as a metal-containing additive for 30 minutes with a mixed wet mill. While uniformly mixed and dried to prepare a composite titanyl oxalate powder. The prepared titanium titanyl oxalate powder was pyrolyzed at a heating rate of 0.5 ° C./min, a holding temperature of 1000 ° C., and a holding time of 3 hours, and then pulverized to prepare manganese barium titanate powder.

The powder characteristics of the obtained barium manganese titanate powder were measured, and the results are shown in Table 1 below. FIG. 1 is a SEM photograph of the barium manganese titanate powder, FIG. 2 is a particle size distribution diagram of barium manganese titanate powder, and XRD analysis data of manganese barium titanate powder is shown.

Example 2 Preparation of Yttria Barium Titanium Powder

Example 1, but the reaction was carried out using yttrium (Y) as a metal-containing additive to prepare a yttria barium titanate powder.

The powder characteristics of the yttria barium titanate powder obtained above were measured, and the results are shown in Table 1 below.

Example 3 Preparation of Manganese Barium Titanium Powder

In the same manner as in Example 1, but the reaction of manganese (Mn) with a metal-containing additive using a 0.015 molar ratio to barium to prepare a yttria barium titanate powder.

The powder characteristics of the yttria barium titanate powder obtained above were measured, and the results are shown in Table 1 below.

Comparative Example 1: Preparation of manganese barium titanate powder by solid phase method

After preparing and measuring TiO ₂ and BaCO ₃ having a purity of 99.9% or more, 0.03 molar ratio of Mn was added in the form of oxide to barium as an additive, and mixed and wet pulverized with a mixed grinder. At this time, the grinding time was 60 minutes. The pulverized powder was dried and thermally decomposed at a heating rate of 0.5 ° C./min, a holding temperature of 1000 ° C., and a holding time of 3 hours, and then pulverized to prepare manganese barium titanate powder.

The powder characteristics of the obtained barium manganese titanate powder were measured, and the results are shown in Table 1 below. FIG. 1 is a SEM photograph of the barium manganese titanate powder, FIG. 2 is a particle size distribution diagram of barium manganese titanate powder, and XRD analysis data of manganese barium titanate powder is shown.

Comparative Example 2

Manganese titanate powder was prepared in the same manner as in Comparative Example 1 except that manganese (Mn) was used as a metal-containing additive in a molar ratio of 0.015 to barium. The powder characteristics of the barium manganese titanate powder obtained above were measured, and the results are shown in Table 1 below.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Metal-containing additives Mn Y Mn Mn Mn BET 4.356 4.015 4.772 5.612 5.783 PSA (μm) D ₁₀ 0.513 0.603 0.371 0.587 0.460 D ₅₀ 1.010 1.224 0.715 1.484 1.024 D ₁₀₀ 3.01 3.20 3.25 23.44 25.13 XRD Heterogeneity not found Heterogeneity not found Heterogeneity not found Heterogeneity not found Heterogeneity not found

As shown in Table 1, Examples 1 to 3 according to the present invention have a fine and uniform particle distribution, whereas Comparative Examples 1 to 2 using the solid phase method tend to have a particle size as large as about 8 times. It was. It can also be seen that the BET indicating the adsorption amount also proves the above fact.

Comparing the SEM photograph of FIG. 1, the particle size distribution diagram of FIG. 2, and the XRD data of FIG. 3 comparing each data of Example 1 (a) according to the present invention and Comparative Example 1 (b) performed by the conventional solid-state method, The composite barium titanate powder carried out by the present invention shows that the particle size distribution is very uniform and excellent powder with little spherical fine powder.

Accordingly, the present invention, as shown above, is not only uniform in particle size distribution but also easy to maintain the stoichiometric composition even during scale-up, and thus is an advantageous method for commercialization. In addition, it is an economical synthesis method with much higher productivity in terms of raw materials and processes than the conventional liquid phase method of BaMTiO ₃ or higher.

As described above, the method for producing a composite barium titanate-based powder according to the present invention includes barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ obtained by precipitating an aqueous solution of barium chloride and titanium tetrachloride in an oxalic acid solution by an oxalate method. ㆍ 4H ₂ O] and specific metal-containing additives are mixed and pulverized and then heat treated to produce composite barium titanate-based powders with high purity and composition uniformity. By this improved method, there is an effect that can be widely used as a raw material such as small size and high capacity X7R multilayer ceramic capacitor (MLCC), static characteristic thermistor (PTC) and piezoelectric material.

Figure 1 a) shows a SEM picture of barium manganese titanate prepared in Example 1 according to the present invention, b) shows a SEM picture of barium manganese titanate prepared by a conventional solid phase method in Comparative Example 1.

Figure 2 a) shows a particle size distribution of the barium manganese titanate prepared in Example 1 according to the present invention, b) shows a particle size distribution of the manganese barium titanate prepared by a conventional solid-phase method in Comparative Example 1 will be.

Figure 3 a) shows the XRD data of barium manganese titanate prepared in Example 1 according to the present invention, b) shows the XRD data of manganese barium titanate prepared by a conventional solid phase method in Comparative Example 1.

4 is a schematic view showing a manufacturing process diagram of the present invention.

Claims (6)

A mixed solution of barium chloride (BaCl ₂ ) and titanium tetrachloride (TiCl ₄ ) was added dropwise to an aqueous solution of oxalic acid (H ₂ C ₂ O ₄ ) to slurry barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O). Preparing a; Preparing a composite titaniumyl oxalate powder by wet grinding the mixed barium titanyl oxalate slurry with a metal-containing additive in a form selected from oxides, chlorides and nitrides and drying the slurry; Pyrolysing the prepared composite titanyl oxalate powder to prepare a composite barium titanate-based (BaMTiO ₃ ) powder; And Regrinding the composite barium titanate-based powder Method for producing a composite barium titanate-based powder represented by the following formula comprising a. [Formula] (Ba _1-x M _x ) _m (Ti _1-y M _y ) _n O ₃ In the above formula, 0.005 <x + y <0.05 and m / n> 0.98. The method of claim 1, wherein the metal-containing additive is manganese (Mn), magnesium (Mg), calcium (Ca), zirconium (Zr), yttrium (Y), holmium (Ho), digprosium (Dy), erbium ( Oxides, chlorides and nitrides containing one or two or more metals selected from Er), ytterbium (Yb), hafnium (Hf), lead (Pb), strontium (Sr), niobium (Nb), and tantalum (Ta) Method for producing a composite barium titanate-based powder, characterized in that. The method for producing a composite barium titanate powder according to claim 1, wherein the composite barium titanate (BaMTiO ₃ ) powder has a molar ratio of barium (Ba): metal (M) 1: 0.005 to 0.05. The method of claim 1, wherein the mixed wet grinding is performed for 10 to 300 minutes. The method of claim 1, wherein the pyrolysis is performed under a condition that a heating rate is 0.5 to 10 ° C / min and a holding temperature is 700 to 1200 ° C. The method of claim 1, wherein the composite barium titanate-based (BaMTiO ₃ ) powder has a perovskite structure.