WO2014084428A1 - Procédé de préparation de poudre de titanate de baryum et poudre de titanate de baryum préparé selon ledit procédé - Google Patents

Procédé de préparation de poudre de titanate de baryum et poudre de titanate de baryum préparé selon ledit procédé Download PDF

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WO2014084428A1
WO2014084428A1 PCT/KR2012/010346 KR2012010346W WO2014084428A1 WO 2014084428 A1 WO2014084428 A1 WO 2014084428A1 KR 2012010346 W KR2012010346 W KR 2012010346W WO 2014084428 A1 WO2014084428 A1 WO 2014084428A1
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barium titanate
powder
bto
titanate powder
aqueous solution
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Korean (ko)
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최연규
김현
정원식
차경진
박지호
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삼성정밀화학(주)
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Definitions

  • a method for producing barium titanate powder and a barium titanate powder produced by the method are disclosed. More specifically, by including the first calcination step and the second calcination step, barium titanate by an oxalate process capable of producing fine barium titanate powder having a fine powder content, narrow particle size distribution, and high crystallinity A method for producing a powder and a barium titanate powder produced by the method are disclosed.
  • the barium titanate powder was conventionally manufactured by a solid phase reaction in which titanium dioxide (TiO 2 ) and barium carbonate (BaCO 3 ) were mixed and heat-treated at a high temperature, but recently, a small capacity of a multilayer ceramic capacitor (MLCC) has been increased.
  • High purity / composition uniformity, fine grain / particle uniformity, non-aggregation / high dispersion, etc. are required according to high dielectric constant composition, dielectric thinning and high lamination), low temperature plasticization, high frequency and high performance.
  • Various synthesis methods are used for the production of barium titanate powder. However, for mass production of barium titanate powder, a coprecipitation method, which is a kind of liquid phase method, in which barium titanate powder having a low manufacturing cost and a uniform composition can be obtained, must be used.
  • a liquid raw material containing barium (Ba) and titanium (Ti) is added to oxalic acid (H 2 C 2 O 4 ) to barium titanyl oxalate [BaTiO (C 2 O 4 ) 2 to 4H 2 O].
  • the barium titanyl oxalate was calcined at high temperature to synthesize barium titanate (BaTiO 3 ) powder having an appropriate size.
  • the barium titanate particles aggregate strongly together to form aggregates, and since these aggregates adversely affect the reliability of the electronic components, the aggregates are disaggregated to disintegrate and the final product titanium is used.
  • Barium powder is prepared (see Korean Patent Publication Nos. 2003-0015011 and 2008-0070981).
  • a large amount of fine particles are generated during the disintegration process, and high active regions (that is, regions where grain growth is likely to occur even at low temperatures) are formed, thereby causing abnormal grain growth and inorganic additives in the multilayer ceramic capacitor ( For example, rare earths, Mg, Mn, Cr, V, Y, Dy, etc.) cause excessive doping (soiling) there is a problem that causes a decrease in reliability and dielectric constant.
  • One embodiment of the present invention comprises a first calcination step and a second calcination step, by the oxalate process that can produce fine barium titanate powder having a fine powder content, narrow particle size distribution, high crystallinity
  • a method for producing barium titanate powder is provided.
  • Another embodiment of the present invention is prepared by the above production method provides a fine barium titanate powder having a fine powder content, narrow particle size distribution, high crystallinity.
  • BTO barium titanyl oxalate
  • It provides a method for producing barium titanate powder comprising the step (secondary calcination step) the second heat treatment of the BT at 820 ⁇ 890 °C.
  • the method for producing the barium titanate powder, between the BTO production step and the BTO wet grinding step, the step of ripening the produced BTO, filtering the aged BTO, and washing the filtered BTO with excess water may further comprise the step.
  • the method of manufacturing the barium titanate powder may further include obtaining a first BT powder by grinding the BT between the first calcination step and the second calcination step (BT grinding step).
  • the first BT powder may have an average particle diameter of 280 to 320nm and a fine powder content of 5 to 10% by weight (that is, a content of particles having a particle diameter of 70 nm or less).
  • the method of manufacturing the barium titanate powder may further include, after the secondary calcination step, disintegrating the secondary calcined BT to obtain a second BT powder (BT disintegration step).
  • the barium titanate powder may have a fine powder content of 3.5 wt% or less (that is, a content of particles having a particle diameter of 70 nm or less).
  • the fine powder content, narrow particle size distribution, high crystallinity Fine barium titanate powder can be obtained.
  • FIG. 1 is a flowchart illustrating a step-by-step method for producing a barium titanate powder according to an embodiment of the present invention.
  • FIG. 2 shows a series of processes in which barium titanyl oxalate is converted to barium titanate.
  • FIG 3 is a view showing a phenomenon occurring in the barium titanate in the second calcination step and / or disintegration step.
  • FIG. 4 is a SEM photograph prepared in Example 2 to illustrate necking phenomenon between barium titanate particles after the first calcination step and before the BT grinding step.
  • FIG. 5 is a SEM photograph of the barium titanate powder prepared in Example 2.
  • FIG. 6 is a SEM photograph of the barium titanate powder prepared in Comparative Example 1.
  • Figure 7 is a graph showing the particle size distribution of the barium titanate powder prepared in Example 2 and Comparative Example 1.
  • FIG. 1 is a flowchart illustrating a step-by-step method for producing a barium titanate powder according to an embodiment of the present invention.
  • a barium chloride (BaCl 2 ) aqueous solution and a titanium tetrachloride (TiCl 4 ) aqueous solution are prepared (a raw material aqueous solution preparation step).
  • Aqueous solution of barium chloride is usually used by dissolving BaCl 2 ⁇ 2H 2 O in water, and its concentration range may be 0.2 ⁇ 2.0 mol / L.
  • concentration of the barium chloride aqueous solution is within the above range, the productivity of barium titanate (BT) to be described later is high compared to the volume of the barium chloride aqueous solution, and barium chloride is not precipitated.
  • Titanium tetrachloride aqueous solution is usually used by diluting a high concentration of titanium tetrachloride solution, the concentration range may be 0.2 ⁇ 2.0 mol / L.
  • concentration of the titanium tetrachloride aqueous solution is within the above range, the productivity of BT relative to the volume of the titanium tetrachloride aqueous solution is high, and titanium tetrachloride is not precipitated.
  • a mixed aqueous solution of the aqueous barium chloride solution and titanium tetrachloride solution or each of these aqueous solutions is added (for example, dropwise) to the aqueous solution of oxalic acid (H 2 C 2 O 4 ) using a high-speed jet nozzle to add barium titanyl oxal.
  • a rate [BaTiO (C 2 O 4 ) 2. 4H 2 O] (hereinafter referred to simply as BTO) is generated (BTO generation step, S1).
  • the oxalic acid aqueous solution may be used in an amount larger than the barium chloride aqueous solution or titanium tetrachloride aqueous solution.
  • the concentration range of the oxalic acid aqueous solution may be 0.2 ⁇ 5.0 mol / L.
  • the productivity of BT relative to the volume of the oxalic acid aqueous solution is high, and oxalic acid may be completely dissolved in water.
  • the temperature of the oxalic acid aqueous solution may be maintained at 20 ⁇ 100 °C, for example, 50 ⁇ 90 °C.
  • the aqueous solution of the barium chloride solution and the titanium tetrachloride solution in the form of a mixed solution or separately sprayed onto the oxalic acid solution may be added dropwise for 1 to 3 hours. This dropping time can be achieved by adjusting the injection speed of the nozzle.
  • the injection nozzle may use a hydraulic or two-fluid nozzle depending on the flow of the fluid, and the use of the hydraulic nozzle may be more advantageous in terms of convenience or in obtaining a uniform precipitate.
  • As the hydraulic nozzle a full cone, a hollow cone, a flat, or the like may be used.
  • the produced BTO may be aged, filtered, and washed with water (S2). It may be advantageous in terms of productivity that the aging time is 0.5 to 2 hours.
  • filtration means the process of separating only solid-state BTO from the BTO containing slurry using a centrifugal separator specifically. Thereafter, the filtered BTO may be washed with excess water until the pH of the washing liquid is neutral.
  • the wet grinding means a method in which BTO is mixed with a predetermined medium and put into a wet grinding machine such as a beads mill, a ball mill, an attrition mill, and the like.
  • the medium means an organic medium such as alcohol or water such as deionized water, and the use of an organic medium is advantageous in terms of crushing efficiency or particle size, but has a disadvantage of increasing cost. This simplifies the process and has the advantage of reducing costs.
  • water When water is used as the medium, its amount may be 1 to 10 parts by weight based on 1 part by weight of BTO.
  • the viscosity is moderate, so that grinding is easy, and the productivity of BTO is high relative to the volume of water.
  • Grinding time needs to be appropriately controlled due to the difference in grinding force depending on the grinding facility, it may be 10 ⁇ 300 minutes when using a bead mill.
  • the particle size of the final product BT powder can be properly adjusted.
  • Nitrogen-containing additives such as ammonia can be added during this wet grinding process, which can solve the problem of acidification of the mixture before and after grinding, high viscosity of the slurry after grinding, and reduction of the dielectric properties of the powder due to the presence of chlorine ions in the produced BTO. have.
  • the wet milled BTO is dried at a temperature of 400 ° C. or lower to remove the used medium (BTO drying step, S4).
  • BTO drying step, S4 As a result, dried BTO powder is obtained.
  • the drying temperature should be above the boiling point of the medium in order to evaporate and remove the medium used.
  • the BTO powder is charged into a heating furnace, and then subjected to a first heat treatment at 920 to 950 ° C. to produce barium titanate (BT) (first calcination step, S5).
  • first calcination step S5
  • the primary heat treatment temperature is out of the above range
  • barium titanate having a target particle size ie, an average particle diameter of 280 to 320 nm
  • impurities including water and / or carbon may be removed.
  • the temperature increase rate from the drying temperature of the BTO drying step (S4) to the first heat treatment temperature of the first calcination step (S5) may be 0.5 ⁇ 10 °C / min, for example 1 ⁇ 5 °C / min.
  • the productivity of BT is high, the temperature distribution is uniform, and the particle size of the BT powder is uniform.
  • the BT and the tens to hundreds of nm size BT through the process as shown in the following reaction scheme 2 to 4 by removing the excess carbon dioxide and water present in the crystal water of the BTO crystals Get powder.
  • Sagger or Tray may be used as a heating furnace for heat treatment of the dried BTO powder.
  • Sagger means a refractory soil container.
  • the sagger may be, for example, a cuboid shaped container having a square bottom surface.
  • the first BT powder is pulverized through the first calcination step S5 to obtain a first BT powder (BT crushing step S6).
  • this BT grinding step (S6) may be omitted.
  • the BT grinding step S6 may be performed by wet grinding using a mill such as a beads mill, an attention mill, and a ball mill with a predetermined medium, It may also be performed by dry grinding using friction between the raw materials or friction with the pulverizer without using a medium such as a jet mill and a disk mill.
  • the BT grinding step S6 is for separating (ie, breaking) large BT particles into small BT particles. In the BT grinding step (S6), the destruction of the particles is caused to generate a large amount of fine powder, thereby widening the particle size distribution and lowering the crystallinity.
  • the BT grinding step (S6) is performed by wet grinding
  • the wet milled BT is dried at a temperature of 400 ° C. or less to remove the used medium (first BT drying step, S7).
  • a dried first BT powder is obtained.
  • the first BT powder may have an average particle diameter of 280 ⁇ 320nm and the fine powder content of 5 ⁇ 10% by weight.
  • the average particle diameter of the first BT powder has a close correlation with the primary heat treatment temperature of the first calcination step (S5), and accordingly sets a target average particle diameter of the first BT powder first, and then the target average.
  • the primary heat treatment temperature may be determined to achieve a particle diameter.
  • the BT grinding step (S6) is performed by dry grinding
  • the first BT drying step (S7) can be omitted.
  • FIG. 2 shows a series of processes in which barium titanyl oxalate (BTO) is converted to barium titanate (BT).
  • BTO barium titanyl oxalate
  • BT barium titanate
  • BTO is thermally decomposed to generate barium titanate particles BT1
  • barium titanate particles barium titanate particles are removed from the BTO while impurities (water vapor and / or carbon dioxide) are removed).
  • An oxygen deficient layer ('VL' in FIG. 3) is formed in BT1).
  • the barium titanate particles BT1 are grain-grown and selectively necked to form aggregates and barium titanate particles BT2 having a larger particle size than these and optionally aggregated.
  • the oxygen depletion layer has a high activity against grain growth, and when the barium titanate particles (BT1) are used in the dielectric layer of the multilayer capacitor, abnormal grain growth may occur during chip firing. Also referred to. Accordingly, the barium titanate particles BT1 have a large amount of grain growth in the oxygen deficient layer and a small amount of grain growth in the remaining portions, resulting in an overall nonuniform grain growth (this is called abnormal grain growth). Is converted to). Thereafter, the barium titanate particles BT2 are necked to each other to form the aforementioned aggregate.
  • the agglomerates are separated into smaller barium titanate particles BT3 in the BT milling step S6 to form fine powder FP, wherein the oxygen depletion layer contained in the barium titanate particles BT3 is external. Is exposed.
  • barium titanate powder (BT3 + FP) having a high fine powder content is obtained.
  • the "fine powder content” refers to the content of fine particles having a particle diameter of 70 nm or less contained in the barium titanate (BT) powder.
  • the first BT powder is heat-treated at 820 ⁇ 890 °C secondary (second calcination step, S8). If the secondary heat treatment temperature is less than 820 ° C., there is almost no secondary heat treatment effect. If the secondary heat treatment temperature is higher than 890 ° C., the fine powder content in the final BT powder after disintegration is high and the crystallinity is also low.
  • the temperature increase rate from the drying temperature of the first BT drying step S7 to the secondary heat treatment temperature of the second calcination step S8 may be 0.5 to 10 ° C./min, for example, 1 to 5 ° C./min. have.
  • BT disintegration step S9 disintegration of the BT passed through the second calcination step (S8) to obtain a second BT powder.
  • disintegration means simply breaking the necking of particles without breaking the particles
  • crushing means breaking one particle and separating it into two or more pieces.
  • this BT disintegration step S9 may be omitted.
  • the BT pulverization step S9 may be performed by wet pulverization using a pulverizer such as a beads mill, an attention mill, and a ball mill together with a predetermined medium. It may also be carried out by dry pulverization using friction between the raw materials or friction with the crusher without using a medium such as a jet mill and a disk mill.
  • the BT disintegration step (S9) is for solving the aggregation between the particles of the BT powder.
  • the BT disintegration step (S9) if the equipment having a high disintegration efficiency is used, particle breakage is caused and a large amount of fine powder is generated, which may result in a narrow particle size distribution and a decrease in crystallinity. It is desirable to lower the breaking strength to break only the necking of the particles without breaking the particles themselves.
  • the wet disintegration BT is dried at a temperature of 350 ° C. or less to remove the used medium (second BT drying step, S10). .
  • the second BT powder may have a fine powder content of 3.5% by weight or less.
  • the second BT drying step S10 may be omitted.
  • the barium titanate particles BT3 that is, BaTiO
  • the barium titanate particles BT4 in which abnormal grain growth is suppressed are formed by removing the oxygen depletion layer VL.
  • the fine powders FP are recombined or redoped with the barium titanate particles BT4 to form barium titanate particles BT5 having a low fine content.
  • the recombination or redistribution may be performed by rearranging the fines FP after migration to the barium titanate particles BT4.
  • the BTO slurry prepared above was filtered with a centrifugal separator and washed with excess water so that the pH of the washing solution was 6 or more to obtain BTO.
  • BTO 50 kg of the BTO, 250 kg of deionized water, and 0.5 kg of 29% by volume ammonia water (8. 4 mol parts relative to 100 mol parts of BTO) were added to a mixing tank and stirred to form a slurry. At this time, the pH of the slurry was 9.3. Thereafter, the BTO was wet milled with a 20 L horizontal beads mill (medium: deionized water) such that the maximum particle size was 5 ⁇ m or less. After grinding, the slurry had a pH of 5.1 and a viscosity of 1800 cP. Thus obtained BTO slurry was dried in an oven at a temperature of 200 °C for 12 hours to prepare a BTO powder.
  • the target average particle diameter of the BT produced after the first calcination was set to 300 nm, and the first heat treatment was performed at 950 ° C. for 2 hours.
  • BT-A powder was obtained.
  • the BT-A powder was wet pulverized for 30 minutes at a speed of 5 m / s (ie, 1500 rpm) with a 20 L horizontal beads mill (medium: deionized water).
  • the BT slurry formed after pulverization was dried for 24 hours at 150 °C oven. As a result, a first BT powder was obtained.
  • the second heat treatment was performed for 2 hours while changing the heat treatment temperature in the temperature range of 820 ⁇ 920 °C according to each Example and Comparative Example.
  • BT-B powder was obtained.
  • the BT-B powder was wet pulverized at a circumferential speed of 5 m / s (ie, 1500 rpm) with a 20 L horizontal beads mill (medium: deionized water).
  • the wet disintegration was terminated when the D 50 of the barium titanate measured by the particle size analyzer (Malvern, mastersizer-2000) reached 0.85 to 0.87 ⁇ m.
  • the BT slurry formed after the wet disintegration was dried for 24 hours at 150 °C oven.
  • a second BT powder was obtained.
  • the second calcination and subsequent steps were omitted.
  • the presence of the average particle diameter, average necking angle and derivative is calculated or observed by using an image analysis program (Image Pro Plus ver 4.5) after taking a scanning electron microscope (SEM) photograph 50,000 times using a Jeol JSM-7400F. It was. In this case, the number of BT-B particles measured was 800 or more. In calculating the average particle diameter, the particle diameter of each BT-B particle was calculated by the average of the long axis and the short axis of each BT-B particle.
  • the d-spacing values of the a-axis and the c-axis of the crystal lattice were obtained.
  • the half width was obtained by precise analysis of the (111) plane and the (222) plane in the same manner as the crystallinity measuring method. However, 2 ⁇ regions of the (111) plane and the (222) plane were 38 to 40 degrees (°) and 83 to 84 degrees (°), respectively.
  • the specific surface area was analyzed using a specific surface area meter (Mountech, Macsorb HM-1220).
  • Example 2 a SEM photograph of the BT-B powder prepared in Example 2 was taken and shown in FIG. Referring to FIG. 4, it can be seen that two barium titanate particles of the BT-B powder prepared in Example 2 are necked to each other.
  • the necking angle is represented by theta ( ⁇ ), and it can be seen from Table 1 that the value is 87 degrees (°).
  • the barium titanate (BT-B) powder prepared in Examples 1 to 4 has a smaller average particle diameter and average necking angle than the barium titanate (BT-B) powder prepared in Comparative Examples 2 to 4.
  • the degree of abnormal grain growth appeared to be small.
  • the specific surface area and the half width decreased generally as the secondary calcination temperature increased, and the derivative did not exist when the secondary calcination temperature was above 840 °C.
  • D50 and fine powder content was calculated by using an image analysis program (ImagePro Plus ver 4.5) after scanning electron microscopy (SEM) of 50,000 times using a Jeol JSM-7400F.
  • the number of the measured second BT particles was 800 or more.
  • the particle diameter of each second BT particle was calculated as an average of the long axis and the short axis of each second BT particle.
  • D50 refers to the particle size of the particles corresponding to 50% of the total number of particles when the measured particles are arranged in order from smallest to largest.
  • the fine powder content refers to the percentage of the area occupied by the fine powder having a particle size of less than 70nm of the total area occupied by all the BT particles in the SEM image.
  • the barium titanate powder prepared in Examples 1 to 4 has a smaller D50 or the same as the barium titanate powder prepared in Comparative Examples 1 to 4 (second BT powder).
  • the specific surface area and half width are small, the crystallinity is high, and the fine powder content is low.
  • the fine powder content, narrow particle size distribution, high crystallinity Fine barium titanate powder can be obtained.

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Abstract

L'invention concerne un procédé de préparation de poudre de titanate de baryum et une poudre de titanate de baryum préparé selon ledit procédé. Ledit procédé de préparation de poudre de titanate de baryum comprend une étape de calcination primaire et une étape de calcination secondaire, préparant ainsi une poudre de titanate de baryum ayant une teneur faible en particules fines, une répartition granulométrique fine et des propriétés cristallines élevées.
PCT/KR2012/010346 2012-11-30 2012-11-30 Procédé de préparation de poudre de titanate de baryum et poudre de titanate de baryum préparé selon ledit procédé WO2014084428A1 (fr)

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KR10-2012-0138469 2012-11-30

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