JP2015006970A - Magnesium oxide, production method thereof, and stacked ceramic capacitor containing the same as additive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hexagonal-plate-like magnesium oxide having a diameter of 30-100 nm and a thickness of 5-20 nm, a production method thereof, and a stacked ceramic capacitor containing the same as an additive.SOLUTION: The magnesium oxide production method may include: adding a base to a magnesium compound aqueous solution, in which a magnesium compound is dissolved in water, and reacting it at 50-100°C to precipitate magnesium hydroxide; cleaning and drying the precipitated magnesium hydroxide; and calcining the dried magnesium hydroxide to produce magnesium oxide.

Description

  The present invention relates to magnesium oxide, a method for producing the same, and a multilayer ceramic capacitor containing the same as an additive.

  Magnesium oxide is a compound of magnesium and oxygen, and is a white powder substance, also called magnesia or magnesia, represented by the chemical formula of MgO.

  Magnesium oxide has a high melting point (2800 ° C.), excellent base resistance and electrical insulation at high temperatures, and has a high light transmittance as well as a large coefficient of thermal expansion and thermal conductivity. Due to the various properties of magnesium oxide, it has been used not only as heat-resistant structural materials such as crucibles and refractory bricks, flameproof materials, insulating materials, and light-transmitting materials, but also with various additives, catalysts, It is also used as an adsorbent, magnesia cement, and pharmaceuticals.

In particular, magnesium oxide can be used as an additive during the production of MLCC, but by forming a shell on the surface of the powder, grain growth of barium titanate (BaTiO ₃ ) and other additions during sintering It serves to prevent diffusion of the agent element into the core.

  In order to produce general industrial magnesium oxide powder, it is usually produced by reacting seawater and quicklime, followed by drying → granular → calcination, to produce initial magnesium oxide powder containing many impurities To do. Thereafter, in order to produce high-purity magnesium oxide powder, the magnesium oxide powder containing the impurities is pulverized, hydrated, magnesium hydroxide, dissolved, washed, calcined, and then subjected to high-purity oxidation. Obtain magnesium powder.

  However, since the manufacturing process as described above has to go through many stages, there is a problem that the process is complicated and acts as a factor that increases the production cost of the magnesium oxide powder. Further, the purity of magnesium oxide to be produced is 99.7% or less, and due to such a limit of purity, it is mainly applied to middle and lower crucibles.

  As a method for solving the problems in the process as described above, Patent Document 1 discloses that an electromagnetic wave plasma is generated from an electromagnetic wave plasma apparatus which is one of combustion gas phase methods, and hydroxylated by a single process. A method for producing high-purity magnesium oxide powder from magnesium has been proposed. However, although the process has been simplified, there is still a problem of cost competitiveness because there is a problem that expensive equipment, which is a feature of the gas phase method, is required.

  Further, Patent Document 2 discloses a method for producing pure magnesium oxide powder by ball milling and mixing magnesium chloride and sodium bicarbonate, followed by drying, primary heat treatment, washing unreacted material, and final heat treatment. Proposed.

  More specifically, after mixing magnesium chloride and sodium bicarbonate in a one-stage ball mill process, the wet ball mill is performed for 3 hours, and in the second stage, 80 ° C. is used to remove moisture from the mixture mixed by the wet ball mill. For 24 hours. In the three-stage primary heat treatment process, the amorphous phase Mg—O material is heat-treated at 600 to 900 ° C. for 2 hours in order to convert it into safe MgO crystals, and in the fourth stage, the residual chloride in the heat-treated product is obtained. In order to remove the sodium, washing with water and filtration are repeated four times. In the fifth stage, MgOH generated during washing with water is further oxidized and converted to magnesium oxide, and the temperature condition at this time is at least 800 ° C to 1000 ° C.

  However, the conventional method as described above has a complicated manufacturing process of 1 to 5 stages, and the amount of magnesium oxide that can be lost during ball milling, cleaning, and filtration, and the two heat treatment processes are extremely high. There are problems such as the point to be done in. As can be confirmed from the FE-SEM photograph of FIG. 1 and the XRD result of FIG. 2, the obtained magnesium oxide powder has a particle size of about 1 to 5 microns and exhibits a form of fiber aggregation.

  Another method for synthesizing magnesium oxide is an airgel (AP-MgO) method (Chem. Mater. 1991, 3, 175-181). A white sol is produced by adding magnesium methylate and water to a methanol / toluene solution and reacting overnight while gradually hydrolyzing at room temperature (see FIG. 3). The resulting product is injected with nitrogen gas in an autoclave and then left at 265 ° C. It is estimated that the gel structure is protected by the interaction between the hydrolyzed hydroxy group (OH group) and the toluene solvent.

  Among the methods for synthesizing magnesium oxide metal powder, the liquid phase method has various advantages. However, the production method using an organic solvent such as toluene and ethylene glycol has problems of toxicity and environmental pollution given to workers and researchers who handle materials, despite the many advantages of the liquid phase method.

Korean Registered Patent No. 0727239 Korean Published Patent No. 2010-0119670

Chem. Mater. 1991, 3, 175-181

  As described above, the conventional method for producing magnesium oxide not only goes through a very complicated process, but the process is difficult because most of it is performed at high temperature, and expensive equipment is required. There were great difficulties to apply.

  Accordingly, an object of the present invention is to provide a method for producing magnesium oxide at a low temperature in a short time by a relatively simple process in which the reaction is carried out in an aqueous system.

  Another object of the present invention is to provide magnesium oxide produced by the above method and having hexagonal plate-like particles.

  Still another object of the present invention is to provide a multilayer ceramic capacitor containing the magnesium oxide as an additive of a dielectric layer.

  Magnesium oxide according to one embodiment of the present invention has a hexagonal plate shape with a diameter of 30 to 100 nm and a thickness of 5 to 20 nm.

  Also, the method for producing magnesium oxide of the present invention comprises adding a base to a magnesium compound aqueous solution in which a magnesium compound is dissolved in water and reacting at 50 to 100 ° C. to precipitate magnesium hydroxide, The step of washing and drying magnesium hydroxide and the step of producing magnesium oxide by calcining the dried magnesium hydroxide can be included.

  The reaction between the magnesium compound and the base can be performed at atmospheric pressure.

  The reaction between the magnesium compound and the base can be performed by an aerosol synthesis method.

  The magnesium compound may be one or more selected from the group consisting of magnesium nitrate, magnesium chloride, magnesium sulfide, and magnesium acetate.

  The base may be one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

  The base content with respect to the magnesium compound is preferably in a weight ratio of 1: 1 to 1: 5.

  The concentration of the magnesium compound aqueous solution is preferably 0.1 to 1% by weight.

  For washing the magnesium hydroxide, at least one selected from water, methanol, ethanol, n-propanol, and isopropanol can be used.

  The magnesium hydroxide can be dried at 80 to 100 ° C. for 2 to 6 hours.

  The calcination of the magnesium hydroxide can be performed at 400 to 500 ° C. for 2 to 4 hours.

  In addition, the present invention can provide a multilayer ceramic capacitor containing the hexagonal plate-like magnesium oxide as an additive of a dielectric layer.

  According to the present invention, hexagonal plate-like magnesium oxide having a diameter of 30 to 100 nm and a constant thickness can be produced by an aerosol synthesis method.

  In addition, according to the present invention, since the reaction is performed at a temperature lower than that of the conventional aerosol synthesis method, the process efficiency is high, and magnesium oxide can be produced by reacting in an aqueous system without using an organic solvent.

  By including the magnesium oxide of the present invention as an additive in the dielectric layer of the multilayer ceramic capacitor, a shell is effectively formed on the surface of the barium titanate core powder, and the titanium during sintering It is possible to effectively prevent grain growth of barium acid and diffusion of other additive elements into the core.

3 is an FE-SEM photograph and XRD data of magnesium oxide produced by Patent Document 2. FIG. 3 is an FE-SEM photograph and XRD data of magnesium oxide produced by Patent Document 2. FIG. 2 is an SEM photograph of magnesium oxide produced according to Non-Patent Document 1. 1 is a schematic diagram of a process for producing magnesium oxide according to the present invention. 2 is an FE-SEM photograph of magnesium hydroxide obtained after drying in Example 1. FIG. 2 is an FE-SEM photograph of magnesium hydroxide obtained after drying in Example 1. FIG. 2 is an FE-SEM photograph of magnesium oxide obtained after calcination in Example 1. FIG. 2 is an FE-SEM photograph of magnesium oxide obtained after calcination in Example 2. FIG. It is XRD data of the magnesium hydroxide before calcination of Example 1, and the magnesium oxide after calcination.

  Hereinafter, the present invention will be described in more detail as follows.

  The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the invention. As used herein, the singular form may include the plural form unless the context clearly dictates otherwise. Also, as used herein, “comprise” and / or “comprising” includes the stated shapes, numbers, steps, actions, members, elements, and / or combinations thereof. It does not exclude the presence or addition of one or more other shapes, numbers, actions, members, elements, and / or combinations thereof.

  The present invention relates to hexagonal plate-like magnesium oxide that can be used as an additive constituting a shell with a dielectric layer, a method for manufacturing the same, and a multilayer ceramic capacitor including the same.

  The present invention solves the problem that the manufacturing process is difficult and complicated when producing magnesium oxide using the conventional liquid phase method or aerosol method, and reacts in an aqueous system using water as a solvent. In addition, it is possible to provide a method for producing magnesium oxide that not only has a lower reaction temperature than conventional processes but also has a relatively short reaction time.

  The method for producing magnesium oxide according to the present invention as described above may include a synthesis-washing-drying-calcination step as illustrated in FIG.

  In the synthesis stage, a magnesium compound aqueous solution in which a magnesium compound is dissolved in water is produced, and a base is added and reacted to precipitate magnesium hydroxide.

  Dissolving the magnesium compound in water can be easily performed within a few minutes only by stirring without raising the temperature. At this time, it is preferable to add the base after completely dissolving the magnesium compound. If the base is added in a state where the magnesium compound is not completely dissolved, care must be taken because the resulting particles may be synthesized non-uniformly.

  The magnesium compound is preferably 0.1 to 1% by weight in aqueous solution in terms of maintaining the particle shape.

  The magnesium compound may be one or more selected from the group consisting of magnesium nitrate, magnesium chloride, magnesium sulfide, and magnesium acetate.

  In addition, the base according to the present invention is not added after being dissolved in water, but a powdered base is added to an aqueous solution in which the magnesium compound is dissolved. As the base according to the present invention, one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate can be preferably used.

  Also, according to the present invention, the reaction between the magnesium compound and the base does not require a specific gas atmosphere, and can be performed under atmospheric pressure conditions. Further, the reaction can be performed at 50 to 100 ° C., which is much lower than the temperature of the conventional aerosol synthesis method, and the reaction time can be carried out under a relatively short time of 1 to 2 hours.

  When the reaction temperature is less than 50 ° C., there is a problem that the particle shape is non-uniform even when nuclei are generated, and when it exceeds 100 ° C., there is a problem in process cost, which is not preferable.

  Therefore, the method of the present invention is simplified in process as compared with the conventional aerosol synthesis method, and the reaction time and temperature can be effectively reduced, so that the process efficiency and cost can be improved.

  In the present invention, the size of magnesium oxide can be controlled by adjusting the base content relative to the magnesium compound. In order to control the diameter of the magnesium oxide of the present invention to 30 to 100 nm, the content of the base with respect to the magnesium compound is preferably 1: 1 to 1: 5 by weight.

  Next, the magnesium hydroxide obtained as a precipitate in the synthesis step is washed and dried. The washing is easily carried out at about 2000 to 4000 rpm for several minutes using a centrifugal separator, and the solid is easily separated, and the separated solid is washed with a solvent.

  As the solvent, water, methanol, ethanol, n-propanol, or isopropanol can be used. The washing is preferably repeated twice or more using the washing solvent. The washing process is a process performed to minimize the aggregation of the precipitated magnesium hydroxide, and it is preferable that the washing is performed continuously using water and an organic solvent.

  A process of sufficiently drying the washed magnesium hydroxide is necessary, and in the present invention, it is preferably performed at 80 to 100 ° C. for 2 to 6 hours. If the drying is not performed sufficiently, the particles aggregate with each other, which is not preferable.

  Finally, magnesium oxide is obtained by calcining the dried magnesium hydroxide. Conventionally, the calcination was performed at 800 to 1000 ° C., but in the present invention, it can be performed at 400 to 500 ° C., which is a relatively low temperature, for 2 to 4 hours.

  When calcined in the calcining temperature range, the magnesium oxide having a hexagonal plate-like particle form according to the present invention can be produced.

  The magnesium oxide finally manufactured by the above process may have a hexagonal plate shape with a diameter of 30 to 100 nm and a thickness of 5 to 20 nm.

  In addition, the present invention can provide a multilayer ceramic capacitor containing the hexagonal plate-like magnesium oxide as an additive of a dielectric layer.

The magnesium oxide is a substance that is added to barium titanate used as a base material of the dielectric layer and constitutes a shell that covers the barium titanate (BaTiO ₃ ) core, and the particles of the barium titanate during sintering. It serves to prevent growth and diffusion of other additive elements into the core.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The following examples are only for illustrating the present invention, and the scope of the present invention should not be construed as being limited by these examples. Further, in the following examples, specific compounds were used as examples. However, it is obvious to those skilled in the art that even when these equivalents are used, the same and similar effects can be obtained. .

[Examples 1-2]
Magnesium chloride hydrate was dissolved in water to prepare a 0.3 wt% magnesium chloride hydrate aqueous solution, sodium hydroxide was added, and the mixture was reacted at 80 ° C. for 2 hours. The content of sodium hydroxide with respect to the magnesium chloride hydrate was set to a weight ratio of 1: 1 and 1: 5, respectively.

  Magnesium hydroxide was precipitated by the reaction. The reaction solution was placed in a centrifuge and centrifuged four times at a speed of 4000 rpm.

  The centrifuged upper layer solution was removed, and the resulting magnesium hydroxide precipitate was washed twice with water and ethanol, respectively.

  The washed magnesium hydroxide was completely dried at 80 ° C. for 6 hours and then calcined at 400 ° C. for 2 hours to obtain magnesium oxide.

[Experimental example 1: FE-SEM structure confirmation]
The structures of magnesium hydroxide obtained after drying in Examples 1 and 2 and magnesium oxide obtained after calcination were confirmed by FE-SEM, and the results are shown in FIGS.

  Referring to FIGS. 5 and 6 showing FE-SEM photographs of magnesium hydroxide obtained after drying in Examples 1 and 2, it can be seen that the particles have hexagonal plate-like particles.

  Further, referring to FIG. 7 and FIG. 8 showing FE-SEM photographs of magnesium oxide obtained after calcining in Examples 1 and 2, it has hexagonal plate-like particles, and has a diameter of 30 to 100 nm and It can be seen that it has a constant thickness of about 5-20 nm.

[Experimental example 2: XRD measurement]
Whether or not the magnesium hydroxide before calcination in Example 1 was converted to magnesium oxide after calcination was confirmed by XRD measurement, and the results are shown in FIG.

  As shown in the results of FIG. 9, when calcined at 400 ° C. for 2 hours, the peak due to magnesium hydroxide decreases and the peak due to magnesium oxide increases.

Claims (12)

  Hexagonal plate-like magnesium oxide having a diameter of 30 to 100 nm and a thickness of 5 to 20 nm. Adding a base to a magnesium compound aqueous solution in which the magnesium compound is dissolved in water and reacting at 50 to 100 ° C. to precipitate magnesium hydroxide;
Washing and drying the precipitated magnesium hydroxide;
A step of producing magnesium oxide by calcining the dried magnesium hydroxide, and a method for producing hexagonal plate-like magnesium oxide.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the reaction between the magnesium compound and the base is carried out at atmospheric pressure.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the reaction between the magnesium compound and the base is performed by an aerosol synthesis method.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the magnesium compound is at least one selected from the group consisting of magnesium nitrate, magnesium chloride, magnesium sulfide, and magnesium acetate.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the base is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the content of the base with respect to the magnesium compound is in a weight ratio of 1: 1 to 1: 5.   The manufacturing method of the hexagonal plate-shaped magnesium oxide of Claim 2 whose density | concentration of the said magnesium compound aqueous solution is 0.1 to 1 weight%.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein at least one selected from water, methanol, ethanol, n-propanol, and isopropanol is used for washing the magnesium hydroxide.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the magnesium hydroxide is dried at 80 to 100 ° C for 2 to 6 hours.   The method for producing hexagonal plate-like magnesium oxide according to claim 2, wherein the calcination of the magnesium hydroxide is performed at 400 to 500 ° C. for 2 to 4 hours.   A multilayer ceramic capacitor comprising the magnesium oxide according to claim 1 as an additive for a dielectric layer.

Images