TWI571451B - Apparatus and method for manufacturing ti-based dielectric material - Google Patents

Description

Device and method for manufacturing titanium-based dielectric material

An embodiment of the present invention relates to an apparatus and method for fabricating a titanium-based dielectric material, and more particularly to an apparatus and method for fabricating a titanium-based dielectric material that can operate under high temperature and high pressure conditions .

As various electronic device industries have recently tended to pursue high-performance components having small, lightweight bodies, electronic components such as multilayer ceramic capacitors (MLCC) have become demanding to have small size, high performance, and light weight. Therefore, the dielectric materials used in electronic components need to be functionalized, and the electrical characteristics of such electronic components also need to be improved.

The synthesis method of the dielectric material may be a solid state method, a liquid method, or a vapor method.

The solid state method uses a method of solid phase reactants. As an example of a solid state method, KR 2004-0020252 discloses a method of synthesizing barium titanate (BaTiO ₃ ), wherein the method comprises forming a mixture by mixing barium carbonate (BaCO ₃ ) with titanium dioxide (TiO ₂ ); The mixture was calcined by increasing the temperature of the mixture to 1000 ° C or higher. The method involves calcining the mixture at a high temperature, and thus violent coalescence of the product may occur, the particle size distribution of the product may be broad, and particle refining of the product may be difficult.

The liquid method is a method using a liquid phase reactant, and the method includes a coprecipitation method and a hydrothermal synthesis method.

The general co-precipitation method involves extraction and sinking by using ammonia water and a strong alkali. Two or more phases are deposited; and the resulting precipitate is calcined at a temperature of 1000 °C. This method requires the simultaneous precipitation of two or more phases, and thus the composition of the synthesized dielectric material may be uneven due to the different extraction rates of the phases, and severe coalescence may occur during high temperature calcination.

The general hydrothermal synthesis is carried out at a temperature of from 100 ° C to 200 ° C and a pressure of from 1 bar (bar) to 15.5 bar. Also, the finally synthesized dielectric material (for example, BaTiO ₃ ) has a cubic crystal structure, and thus an additional calcination process is required to convert the cubic crystal structure into a tetragonal crystal structure. However, even after the additional calcination process, a plurality of internal pores formed by the hydroxyl group (OH ^- ) may exist in the dielectric material, and thus crystallinity may be lowered.

The vapor process is a method of synthesizing a dielectric material by spraying a liquid phase reactant for vaporization and condensation. A dielectric material (for example, BaTiO ₃ ) synthesized by using this method has a cubic crystal structure and includes a large amount of a secondary phase of barium carbonate (BaCO ₃ ).

One embodiment of the present invention provides an apparatus for making a titanium-based dielectric material that operates under conditions of high temperature and pressure.

Another embodiment of the present invention also provides a method of producing a titanium-based dielectric material by performing a reaction under high temperature and high pressure conditions.

According to an aspect of the present invention, there is provided an apparatus for manufacturing a titanium-based dielectric material, wherein the apparatus comprises a reactor, the reactor comprising a body unit, a cover unit, and a heat generating unit surrounding at least a portion of the body unit, wherein the body At least one of the unit and the cover unit comprises titanium.

The reactor can be an autoclave.

The apparatus may further include a high pressure water supply that pressurizes water and supplies pressurized water to the main unit.

The titanium-based dielectric material may be a barium titanate compound (Ca _x Sr _y Ba _1-xy TiO ₃ , 0 x 0.2,0 y 0.2,0 x+y 0.2) or lead titanate (PbTiO ₃ ).

According to another aspect of the present invention, there is provided a method of producing a titanium-based dielectric material, wherein the method comprises: introducing a reactant comprising titanium into a reactor; increasing a temperature of the reactor to a range of from 250 ° C to 400 ° C ; the pressure of the reactor increased to 39.8 bar to 400 bar range; and the temperature and pressure of the reactor is increased after a period of time t _m, wherein at least a portion of the parts defining an internal space of the reactor comprises titanium.

The reactant may further include at least one of Ba, Pb, Ca, and Sr.

This period of time t _m can range from 10 hours to 50 hours.

100‧‧‧ manufacturing equipment

110‧‧‧Reactor

111‧‧‧Main unit

112‧‧‧ cover unit

113‧‧‧Fever unit

114‧‧‧Agitator

115‧‧‧ thermometer

116‧‧‧ fastening bolts

117‧‧‧ Pressurized water injection tube

120‧‧‧temperature controller

130‧‧‧High pressure water supply

140‧‧‧Water tank

WF‧‧‧Water supply pipeline

The above and other features and advantages of the present invention will become more apparent from the aspects of the embodiments of the invention illustrated herein Schematic diagram of a device for a titanium-based dielectric material; FIG. 2 is a scanning electron microscope (SEM) image of barium titanate particles prepared by a device for fabricating a titanium-based dielectric material according to an embodiment (Example 5) of the present invention; 3 is an SEM image of barium titanate particles prepared by a device for manufacturing a titanium-based dielectric material according to a conventional technique (Comparative Example 1); FIG. 4 is a process for producing a titanium-based medium according to an embodiment (Example 5) of the present invention. Rietveld analysis results of barium titanate particles prepared by a device of electrical material; 5 is a Rietveld analysis result of barium titanate particles prepared by a device for manufacturing a titanium-based dielectric material according to a conventional technique (Comparative Example 1); FIG. 6 is a process for producing titanium according to an embodiment (Example 5) of the present invention. Transmission electron microscope (TEM) image of barium titanate particles prepared by a device of a dielectric material; and FIG. 7 is a barium titanate prepared by a device for manufacturing a titanium-based dielectric material according to the prior art (Comparative Example 1) TEM image of the particles.

Hereinafter, an apparatus for manufacturing a titanium-based dielectric material and a method thereof according to an embodiment of the present invention will be described more fully with reference to the accompanying drawings.

1 is a schematic view of a manufacturing apparatus 100 for a titanium-based dielectric material in accordance with an embodiment of the present invention.

A manufacturing apparatus 100 for manufacturing a titanium-based dielectric material according to an embodiment of the present invention includes a reactor 110, a temperature controller 120, a high pressure water supply 130, and a water storage tank 140.

The reactor 110 includes a main body unit 111, a cover unit 112, a heat generating unit 113 surrounding at least a portion of the main body unit 111, and an agitator 114 installed in the main body unit 111.

The body unit 111 is a place where a reactant (not shown) including titanium (Ti) is added and converted into a titanium-based dielectric material.

The cover unit 112 is arranged to cover the main body unit 111 and to seal the main body unit 111. The cover unit 112 can be coupled to the body unit 111 by a fastening bolt 116. A plurality of through holes (not shown) are formed in the cover unit 112, and the agitator 114, the thermometer 115, the fastening bolts 116, and the pressurized water injection pipe 117 can be installed in the reactor 110 through the through holes.

The agitator 114 can be installed in the main body unit 111 so that the agitator 114 A portion penetrates the cover unit 112. The agitator 114 agitates the contents of the reactor 110 (not shown), such as reactants, and thus promotes heat transfer and mass transfer in the contents.

At least one of the main body unit 111, the cover unit 112, and the agitator 114 includes titanium. For example, a portion of the body unit 111 and a portion of the lid unit 112 define an interior space of the reactor 110, and a portion of the agitator 114 exposed to the interior space may include titanium. Since each portion of the reactor 110 includes titanium, each portion of the reactor 110 can have high corrosion resistance when a strong base is included in the contents of the reactor 110, and a long-term reaction process when titanium is subjected to high temperature and high pressure. The medium is corroded or melted, so that when titanium is separated from each portion of the reactor 110, the separated titanium becomes a part of the reactant including titanium, instead of becoming an impurity. Therefore, as described below, the temperature and pressure of the reactor 110 can be increased to 250 ° C to 400 ° C and 39.8 to 400 bar, respectively, and thus a titanium-based medium having a square crystal structure, high crystallinity, and high density can be obtained. Electrical material. In this regard, the titanium-based dielectric material fabricated in the manufacturing apparatus 100 does not require an additional calcination process.

A conventional manufacturing apparatus for a titanium-based dielectric material includes a stainless steel (e.g., SUS 304) autoclave and a Teflon container placed in an autoclave. The Teflon container is used to prevent the stainless steel autoclave from being corroded by a strong base (i.e., a slurry containing the reactant) having a pH of 13 or higher, but the Teflon container is thermally deformed at a temperature higher than 200 °C. Therefore, the reaction temperature of the conventional manufacturing apparatus for a titanium-based dielectric material is limited to the range of 100 ° C to 200 ° C, and the reaction pressure is limited to the saturated water vapor pressure at each reaction temperature. Therefore, a titanium-based dielectric material having a cubic crystal structure can be produced. Therefore, in order to manufacture a titanium-based dielectric material having a square crystal structure by using a conventional manufacturing apparatus for a titanium-based material, a titanium-based dielectric material having a cubic structure manufactured by a conventional manufacturing apparatus requires further calcination. And, therefore, the manufacturing process can become complicated and the manufacturing cost may increase. In addition, even when a titanium-based dielectric material having a cubic crystal structure manufactured by a conventional manufacturing apparatus is further calcined, a plurality of pores are formed due to a hydroxyl group (OH ^- ) formed by the reaction, and thus crystallinity may be lowered. .

In general, a titanium-based dielectric material having a square crystal structure is a ferroelectric, and a titanium-based dielectric material having a cubic crystal structure is a paraelectric. Therefore, the titanium-based dielectric material used in the multilayer ceramic capacitor with the electrostatic charge accumulation function needs to have a square crystal structure ("Introduction to Ceramics", WD Kingery et al., Sakae Press, p. 436 (Introduction to Ceramics, WDKingery, Et al., Bando publication, pp. 436)).

The heat generating unit 113 is disposed to surround at least a portion of the body unit 111 to supply heat to the body unit 111 and increase the temperature of the reactor 110.

Reactor 110 can be an autoclave, but is not limited to an autoclave. As used herein, the term "autoclave" refers to a heat resistant and pressure resistant container that can perform chemical treatments (such as synthesis, decomposition, sublimation, extraction, etc.) under high temperature and pressure conditions. The temperature and pressure in the vessel can be maintained in the range of 250 ° C to 400 ° C and in the range of 39.8 to 400 bar, respectively.

The temperature controller 120 controls the temperature of the heat generating unit 113. In particular, the temperature controller 120 may heat or stop heating the firing unit 113 to compensate for the actual temperature of the reactor 110 as measured by the thermometer 115 and the predetermined target temperature of the reactor 110 (eg, 250 ° C to 400 ° C). The difference is thus controlled by the temperature of the reactor 110.

The high pressure water supplier 130 pressurizes water and supplies pressurized water to the main body unit 111 through the water supply line WF. The high pressure water supply 130 can include a high pressure metering pump (not shown). The high pressure water supply 130 may not be included in the manufacturing apparatus 100.

The water storage tank 140 is in communication with the high pressure water supply 130 to supply water to the high pressure water supply 130. In detail, the high pressure water supply 130 draws up the water filled in the water storage tank 140. The water filled in the water storage tank 140 may be pure water.

The titanium-based dielectric material produced by the manufacturing apparatus 100 for a titanium-based dielectric material may have a square crystal structure.

The titanium-based dielectric material may be a barium titanate-based compound (Ca _x Sr _y Ba _1-xy TiO ₃ , 0 x 0.2,0 y 0.2,0 x+y 0.2) or lead titanate (PbTiO ₃ ), but is not limited to the two.

A method of fabricating a titanium-based dielectric material in accordance with an embodiment of the present invention will hereinafter be described in detail.

The manufacturing method of the titanium-based material comprises: introducing a reactant (S1) including titanium into a reactor equipped with a stirrer, increasing the temperature of the reactor to a range of 250 ° C to 400 ° C (S2), and bringing the pressure of the reactor Increasing to a range of 39.8 bar to 400 bar (S3), maintaining the increased temperature and pressure for a period of time t _m (S4), and agitating the reactor with a stirrer in at least one of the four aforementioned steps (S5).

The reactor and agitator can be the same or similar to reactor 110 and agitator 114 of Figure 1, respectively.

At least one of the agitator and portions defining the interior space of the reactor (i.e., the inner wall, ceiling, and bottom of the reactor) comprises titanium. In this regard, even when the agitator and the portions defining the internal space of the reactor are deformed after a long period of time at a high temperature and a high pressure, and thus titanium can be separated from the agitator and portions defining the internal space of the reactor and mixed to The titanium being mixed is still used as a reactant rather than an impurity in the contents of the reactor.

In step S1, the reactants are mixed with water (for example pure water) and used in the form of a slurry. Therefore, the product produced in the reactor (for example, a titanium-based dielectric material) can be obtained in the form of a slurry. The reactant may further include at least one of Ba, Pb, Ca, and Sr. In particular, the reactants may include titanium isopropoxide (Ti[OCH(CH ₃ ) ₂ ] ₄ ), titanium tetrachloride (TiCl ₄ ), titanium oxychloride (TiOCl ₂ ), titanium dioxide (TiO ₂ ) or more. A mixture of each of them comes as a source of titanium. Further, the reactant may include barium hydroxide (Ba(OH) ₂ .8H ₂ O), lead hydroxide (Pb(OH) ₂ ), calcium hydroxide (Ca(OH) ₂ ), barium hydroxide (Sr(OH) ₂ ) or a mixture of the above, as an additional component.

In step S2, as the temperature of the reactor increases, the water in the contents of the reactor evaporates, and thus the pressure of the reactor increases to the saturated water vapor pressure at the final temperature of the reactor. When the temperature of the reactor is lower than 250 ° C, the synthesized titanium-based dielectric material has a cubic crystal structure. When the temperature of the reactor is higher than 400 ° C, the airtightness of the reactor is lowered, and the reactor can be excessively corroded.

In step S3, the pressure of the reactor may be the saturated water vapor pressure at each reaction temperature, or may be increased to be higher than the saturated water vapor pressure by introducing pressurized water into the pressurized steam pressure reactor. pressure. When the pressure of the reactor is lower than 39.8 bar, the size of the pores in the synthetic titanium-based dielectric material may increase, and thus the degree of crystallinity may decrease. When the pressure of the reactor is higher than 400 bar, the reactor can be excessively corroded and the service life of the reactor may be shortened.

In step S4, the reactants are converted to a titanium based dielectric material. The period of time t _m can be from 10 hours to 50 hours. When the period of time t _{m is} less than 10 hours, the crystallinity of the synthesized titanium-based dielectric material is lowered. When the period of time t _m exceeds 50 hours, the particle distribution of the synthesized titanium-based dielectric material is not uniform.

When the reactor temperature, the reactor pressure, and the period of time t _{m are} within the above range (ie, the temperature range in step S2 and step S4, the pressure range in step S3 and step S4, and the holding time in step S4), A titanium-based dielectric material having high crystallinity and high density is obtained. In particular, the titanium-based dielectric material ultimately produced in step S4 may have a tetragonal crystal structure.

Step S5 can be performed simultaneously with at least one of steps S1 to S4. In step S5, heat transfer and mass transfer in the contents of the reactor are promoted so that almost the same degree of reaction can occur almost anywhere in the reactor, and thus the product can be homogeneous.

The invention is described in more detail below with reference to the following examples, but these examples are for illustrative purposes only and are not intended to limit the scope of the invention.

Instance Comparative Example 1 and Comparative Example 2 and Examples 1 to 9

Excess pure water was added to titanium isopropoxide to hydrolyze titanium isopropoxide. HNO _{3 was} added to the hydrolyzate of titanium isopropoxide, and it was heat-treated at 60 ° C for 10 hours to obtain a 1.2 M TiO ₂ sol. Will Ba(OH) ₂ . 8H ₂ O was added to the TiO ₂ sol to obtain a Ba/Ti molar ratio of 1.05, and it was heat-treated at a temperature of 100 ° C for 10 hours to obtain a BaTiO ₃ slurry. The BaTiO ₃ slurry was filtered and concentrated to give a concentration twice as high as the concentration before filtration. Subsequently, a concentrated BaTiO ₃ slurry is introduced into the apparatus for manufacturing a titanium-based dielectric material of FIG. 1 and subjected to heat treatment under various conditions, including the reaction temperature, reaction time, and reaction time detailed in Table 1 below. Reaction pressure. Thus, barium titanate (BaTiO ₃ )) was obtained. The reaction pressure itself is the saturated water vapor pressure at the corresponding reaction temperature, or is supplied to the reactor (autoclave, internal manufacturing) by a high pressure water supply (high pressure metering pump, LabAlliance, CP-24). Pure water is set to a pressure higher than the saturated water vapor pressure at the corresponding reaction temperature.

Evaluation example

The average diameter, crystal structure, crystallinity (c/a) and size of the pores of each barium titanate prepared in Comparative Example 1 and Comparative Example 2 and Examples 1 to 9 were measured, and the results are shown in Table 2 below. Out.

An image of barium titanate was obtained by using a scanning electron microscope (SEM, JEOL, JSM-7400F), and then in a scanning electron microscope image by using an image analysis program (Image-pro Plus version 4.5) The long axis and the minor axis of the barium titanate particles contained are averaged to obtain an average diameter of barium titanate. In this case, the amount of the barium titanate particles measured is 800 or more. Further, under the analysis conditions including a 2θ of 10° to 150°, a scan rate of 0.125°, a current of 200 mA, and a measurement voltage of 40 kV, by using an X-ray diffraction detector (XRD; Rigaku, D/Max 2000 series) analyzed barium titanate, and then used the Rietan-2000 software to analyze the X-ray diffraction detector spectrum obtained by the Rietveld method to obtain barium titanate. Crystallinity (c/a). Further, the crystal structure was determined by the peak shape at the point where the 2θ of the Rietveld analysis was 44 to 46 (for example, the P _t peak of Fig. 4 and the P _c peak of Fig. 5). In particular, it is concluded that when the peak is clearly divided into two peaks (such as the P _t peak in Figure 4), barium titanate has a tetragonal crystal structure, and when the peak is a peak (as shown in Fig. 5) peak P _c), the barium titanate having a cubic crystal structure (H.Xu and L.Gao, the material of Letters 58 (2004), pp. 1582 (H.Xu and L.Gao, materials Letters 58 (2004), Pp 1582)). Further, the size of the pores of the barium titanate was determined by measuring the pores of all the individual particles in the barium titanate image obtained by a transmission electron microscope (TEM, Hitachi, CM200).

The SEM images of the barium titanate prepared in Example 5 and Comparative Example 1 are shown in Figs. 2 and 3, respectively. Further, the results of Rietveld analysis of the barium titanate prepared in Example 5 and Comparative Example 1 are shown in Figs. 4 and 5, respectively. Further, the TEM images of the barium titanate prepared in Example 5 and Comparative Example 1 are shown in Figs. 6 and 7, respectively.

Referring to Table 2, the barium titanate prepared in Examples 1 to 9 had a tetragonal crystal structure, and the barium titanate prepared in Comparative Example 1 and Comparative Example 2 had a cubic crystal structure. In addition, the barium titanate prepared in Examples 1 to 9 had higher crystallinity and a smaller pore size than the barium titanate prepared in Comparative Example 1 and Comparative Example 2. According to the results of Table 2, it was confirmed that the barium titanate prepared in Examples 1 to 9 had better dielectric properties and higher crystallization than the barium titanate prepared in Comparative Example 1 and Comparative Example 2. Degree and higher density.

Further, referring to FIGS. 2 and 3 and FIGS. 6 and 7, the barium titanate prepared in Example 5 had a smaller average diameter than the barium titanate prepared in Comparative Example 1.

According to an embodiment of the present invention, an apparatus for manufacturing a titanium-based dielectric material and a method thereof are provided to obtain a nanometer size (for example, 0.02 μm to 0.5 μm) having a high crystallinity and a low impurity content and having a narrow particle size distribution. Titanium based dielectric material.

Further, according to the apparatus for manufacturing a titanium-based dielectric material and the method thereof, a titanium-based dielectric material having a high crystal square structure can be obtained without a separate honing process.

Although the present invention has been particularly shown and described with reference to the exemplary embodiments of the present invention, it will be understood by those skilled in the art Make a variety of changes in form and detail.

100‧‧‧ manufacturing equipment

110‧‧‧Reactor

111‧‧‧Main unit

112‧‧‧ cover unit

113‧‧‧Fever unit

114‧‧‧Agitator

115‧‧‧ thermometer

116‧‧‧ fastening bolts

117‧‧‧ Pressurized water injection tube

120‧‧‧temperature controller

130‧‧‧High pressure water supply

140‧‧‧Water tank

WF‧‧‧Water supply pipeline

Claims (6)

An apparatus for manufacturing a titanium-based dielectric material, the apparatus comprising a reactor comprising a body unit, a cover unit, a heat generating unit surrounding at least a portion of the body unit, and a high pressure water supply for pressurizing water The pressurized water is supplied to the body unit, wherein at least one of the body unit and the cover unit comprises titanium. The apparatus for producing a titanium-based dielectric material according to claim 1, wherein the reactor is an autoclave. The apparatus for producing a titanium-based dielectric material according to claim 1, wherein the titanium-based dielectric material is a barium titanate compound (Ca _x Sr _y Ba _1-xy TiO ₃ , 0 x 0.2,0 y 0.2,0 x+y 0.2) or lead titanate (PbTiO ₃ ). A method of producing a titanium-based dielectric material, the method comprising: introducing a reactant comprising titanium into a reactor; increasing the temperature of the reactor to a range of from 250 ° C to 400 ° C; increasing the pressure of the reactor a range of from 39.8 to 400 bar; and maintaining the increased temperature and pressure for from 10 hours to 50 hours; at least a portion of the portions defining one of the interior spaces of the reactor comprising titanium. The method of producing a titanium-based dielectric material according to claim 4, wherein the reactant further comprises at least one of Ba, Pb, Ca, and Sr. The method for producing a titanium-based dielectric material according to claim 4, wherein the titanium-based dielectric material is a barium titanate compound (Ca _x Sr _y Ba _1-xy TiO ₃ , 0 x 0.2,0 y 0.2,0 x+y 0.2) or lead titanate (PbTiO ₃ ).