Barium titanate powder and method for producing same

Abstract

Provided are: a BaTiO3 powder that has relatively uniform particle size, high circularity, and excellent crystallinity and tetragonality; and a method for producing the same. This method for producing a barium titanate (BaTiO3) powder comprises the following steps: a step for mixing a barium carbonate (BaCO3) powder with a titanium dioxide (TiO2) powder so as to obtain a first mixture that has a Ba / Ti molar ratio of 0.990 to 0.994 inclusive; a step for subjecting the first mixture to a heat treatment at a temperature of higher than 900°C but not higher 1000°C so as to obtain a first heat-treated product that contains barium titanate (BaTiO3); a step for mixing the first heat-treated product with an additional barium (Ba) source so as to obtain a second mixture that has a Ba / Ti molar ratio of 1.001 to 1.010 inclusive; and a step for subjecting the second mixture to a heat treatment at a temperature of 700°C to 900°C inclusive so as to obtain a second heat-treated product that contains barium titanate (BaTiO3).

Description

Barium Titanate Powder and Method for Producing the Same

[0001] The present invention relates to barium titanate powder and a method for producing the same.

[0002] Barium titanate (BaTiO ３ ) is a type of perovskite compound and is characterized by having a high dielectric constant. Therefore, it is used in a wide range of applications including not only dielectric elements (capacitors) and piezoelectric elements, but also optoelectronic elements, semiconductor elements and the like. In particular, BaTiO ３ is widely used as a material for dielectric ceramic layers of multilayer ceramic capacitors (MLCCs). Multilayer ceramic capacitors are characterized by being compact while having a large capacitance (electrostatic capacitance), and demand therefor has been increasing along with the miniaturization of electronic devices typified by mobile phones and the increase in operating speed of CPUs. Accordingly, development of BaTiO ３ powder as the raw material therefor has been progressing.

[0003] As methods for synthesizing BaTiO ３ powder, various methods such as a solid-phase reaction method, an oxalate method, a hydrothermal method, a sol-gel method, and an alkoxide method have been proposed. Among these, the oxalate method synthesizes barium titanyl oxalate by a liquid phase method using barium chloride, titanium tetrachloride and oxalic acid, and heat-treats the obtained barium titanyl oxalate to obtain BaTiO ３ powder. The oxalate method has drawbacks in that it is difficult to control the composition (Ba / Ti ratio), and since hydrochloric acid is produced as a by-product, it is necessary to provide expensive waste liquid treatment equipment. The hydrothermal method has a problem that special production equipment such as an autoclave is required. The sol-gel method and the alkoxide method have drawbacks in that raw materials are expensive and productivity is poor.

[0004] In contrast, in the solid-phase reaction method, barium carbonate (BaCO ３ ) and titanium oxide (TiO ２ ), which are solid raw materials, are heat-treated as a mixture to synthesize BaTiO ３ powder. This method has advantages that inexpensive and chemically stable raw materials can be used, expensive production equipment is not required, and synthesis can be performed by a simple method. Therefore, BaTiO ３Solid-phase reaction methods are widely used as a synthesis technique for powders.

[0005] BaTiO by solid-phase reaction ３ Patent Document 1 is cited as a document disclosing powder synthesis. Patent Document 1 discloses a method for producing dielectric particles, which includes the steps of: preparing a first mixed powder by mixing titanium dioxide particles and barium compound particles; a first heat treatment step of heat-treating the first mixed powder at a temperature of 500°C or higher and less than 900°C to obtain composite oxide particles consisting only of 75 to 25 mol% barium titanate phase and 25 to 75 mol% titanium oxide phase; further mixing alkaline earth compounds, etc., with the obtained composite oxide particles to prepare a second mixed powder; and a second heat treatment step of heat-treating the second mixed powder at a temperature of 850 to 1000°C (Claim 1 of Patent Document 1).

[0006] Japanese Patent Publication No. 2009-242212

[0007] BaTiO ３ Although the synthesis of powders has been done conventionally, there was room for improvement in the conventional methods. In other words, in order to improve the properties of electronic components, the raw material BaTiO ３ In some cases, it is necessary to improve the crystallinity or tetragonal properties of powders. Here, tetragonal properties refer to BaTiO ３ This is the ratio (c / a) of the lattice constant in the c-axis direction (c) to the lattice constant in the a-axis direction (a), and BaTiO ３ This is an index that indicates the degree to which a crystal belongs to a particular crystalline system (normal crystal system).

[0008] BaTiO with excellent crystallinity and tetragonal properties ３ To obtain powder by solid-phase reaction, increasing the heat treatment temperature during the reaction is effective. However, high-temperature heat treatment can easily lead to phenomena such as abnormal grain growth, resulting in a non-uniform particle size distribution. Furthermore, growth within the particles can occur unevenly, making it easy for amorphous particles to be produced. BaTiO has a non-uniform particle size distribution and a large amount of amorphous particles. ３ Powders often pose problems when trying to improve the properties of electronic components.

[0009] The present inventors have now developed a method for producing BaTiO by solid-phase reaction. ３We proceeded with the investigation of powder synthesis. As a result, we found a method in which a relatively high-temperature heat treatment (first heat treatment) is performed followed by a relatively low-temperature heat treatment (second heat treatment), and the composition of the raw material mixture (first mixture) and the intermediate product (second mixture) is controlled within a predetermined range. With this method, BaTiO has a relatively uniform particle size, high circularity (sphericity), and excellent crystallinity and tetragonal properties. ３ We have gained the insight that a powder can be obtained from this BaTiO. ３ We also gained insights into the fact that using powders makes it possible to manufacture electronic components with superior properties, such as temperature characteristics.

[0010] The present invention was completed based on these findings, and is a BaTiO2 with relatively uniform grain size, high circularity, and excellent crystallinity and tetragonal properties. ３ The objective is to provide a powder and a method for producing the same.

[0011] The present invention encompasses the following embodiments. In this specification, the expression "~" includes the numerical values ​​at both ends. That is, "X ~ Y" is synonymous with "X or more and Y or less".

[0012] According to one aspect of the present invention, barium titanate (BaTiO ３ A method for producing the powder, comprising the following steps: barium carbonate (BaCO3) ３ ) powder and titanium dioxide (TiO ２ ) A step of mixing powders to obtain a first mixture having a Ba / Ti molar ratio of 0.990 or more and 0.994 or less; The first mixture is heat-treated at a temperature of more than 900°C and less than or equal to 1000°C to obtain barium titanate (BaTiO) ３ The steps are: obtaining a first heat-treated product containing ), mixing the first heat-treated product with an additional barium (Ba) source to obtain a second mixture having a Ba / Ti molar ratio of 1.001 or more and 1.010 or less, and heat-treating the second mixture at a temperature of 700°C or more and 900°C or less to obtain barium titanate (BaTiO). ３ A method is provided which includes the step of obtaining a second heat-treated product containing ).

[0013] According to another aspect of the present invention, barium titanate powder is provided, wherein the median particle circularity is 0.8 or more and 1.0 or less, the cumulative 50% diameter (Dv50) in the volume particle size distribution is 180 nm or more and 300 nm or less, the ratio of the cumulative 10% diameter (Dn10) in the number particle size distribution to Dv50 (Dn10 / Dv50) is 0.38 or more, the ratio of the BET diameter of the particles to the crystallite diameter of the barium titanate (BET diameter / crystallite diameter) is 1.20 or more and 1.50 or less, and the ratio of the lattice constant in the c-axis direction (c) to the lattice constant in the a-axis direction (a) of the barium titanate (c / a) and Dv50 satisfy the following relationship (1).

[0014]

[0015] According to yet another aspect of this embodiment, a method for manufacturing a multilayer ceramic capacitor, wherein barium titanate (BaTiO) is used in the manner described above. ３ ) Steps to produce the powder, the barium titanate (BaTiO ３ A method is provided comprising the steps of: mixing powder and solvent to produce a ceramic slurry; molding the ceramic slurry to produce a dielectric green sheet; forming a conductive pattern on the surface of the dielectric green sheet; stacking a plurality of the dielectric green sheets having conductive patterns on their surfaces to produce a green laminate; and firing the green laminate to produce a laminate.

[0016] According to yet another aspect of this embodiment, a method for manufacturing a multilayer ceramic capacitor, wherein the above-mentioned barium titanate (BaTiO) ３ ) Steps to prepare the powder, the barium titanate (BaTiO ３ A method is provided comprising the steps of: mixing powder and solvent to produce a ceramic slurry; molding the ceramic slurry to produce a dielectric green sheet; forming a conductive pattern on the surface of the dielectric green sheet; stacking a plurality of the dielectric green sheets having conductive patterns on their surfaces to produce a green laminate; and firing the green laminate to produce a laminate.

[0017] According to the present invention, BaTiO has a relatively uniform grain size, high circularity, and excellent crystallinity and tetragonal properties. ３ A powder and a method for producing the same are provided.

[0018] This is a schematic diagram showing the internal structure of a multilayer ceramic capacitor. ３ This figure shows the relationship between the cumulative 50% diameter (Dv50) of the powder and the lattice constant ratio (c / a).

[0019] Specific embodiments of the present invention (hereinafter referred to as "these embodiments") are described below. However, the present invention is not limited to the following embodiments, and various modifications are possible as long as they do not alter the essence of the invention. Furthermore, in this specification, any combination of preferred embodiments can be adopted as long as technical consistency can be maintained. For example, one of the preferred numerical ranges can be arbitrarily combined with the other.

[0020] <<1. Method for producing barium titanate powder>> Barium titanate (BaTiO) of this embodiment ３ The method for producing the powder is as follows: Barium carbonate (BaCO3) ３ ) powder and titanium dioxide (TiO ２ The first step involves mixing the powders to obtain a first mixture having a Ba / Ti molar ratio of 0.990 or more and 0.994 or less (first mixing step), and then heat-treating the obtained first mixture at a temperature of over 900°C and 1000°C or less to obtain barium titanate (BaTiO). ３ The process involves obtaining a first heat-treated product containing (first heat treatment step), mixing the obtained first heat-treated product with an additional barium (Ba) source to obtain a second mixture having a Ba / Ti molar ratio of 1.001 or more and 1.010 or less (second mixing step), and heat-treating the obtained second mixture at a temperature of 700°C or more and 900°C or less to obtain barium titanate (BaTiO). ３ This process includes a step (second heat treatment step) to obtain a second heat-treated product containing ). Details of each step are described below.

[0021] <First Mixing Process> In the first mixing process, barium carbonate (BaCO3) is used. ３ ) powder and titanium dioxide (TiO ２The powders are mixed to obtain a first mixture having a Ba / Ti molar ratio of 0.990 or more and 0.994 or less. BaCO ３ Powder and TiO ２ Each powder is the final product, BaTiO ３ These are powdered Ba and Ti raw materials. BaCO ３ Powder and TiO ２ Any known raw materials can be used as the powder. Furthermore, the particle size (specific surface area) is not limited as long as it can be mixed. However, fine BaCO3 is not suitable. ３ Powder and TiO ２ The powder is highly reactive, and the resulting BaTiO ３ It contributes to the fineness of powders. On the other hand, excessively fine raw material powders are difficult to handle. While maintaining high handlingability, BaTiO ３ From the perspective of reducing the fineness of the powder, BaCO ３ The specific surface area (SSA) of the powder is 2 m². ２ / g or more 30m ２ Preferably less than / g, and 10m ２ / g or more 30m ２ Less than / g is more preferable. Also, from a similar viewpoint, TiO ２ The specific surface area (SSA) of the powder is 20 m². ２ Preferably 30 m ２ / g or more 100m ２ A value of less than / g is more preferable.

[0022] BaCO ３ Powder and TiO ２ The powder mixing may be carried out either dry or wet. Also, when mixing, the material to be treated (BaTiO ３ Powder and TiO ２The powder may be ground. For wet mixing, known wet mixing equipment such as a ball mill, bead mill, attritor, vibratory mill, disper mill, sand grind mill, or wet jet mill may be used. As the mixed solvent, known solvents such as water, methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methyl ethyl ketone, methylene chloride, ethyl acetate, dimethylformamide, or dimethyl ether may be used. The mixed solvent may be one solvent alone or a combination of multiple solvents. For dry mixing, known dry mixing equipment such as a Henschel mixer, Nauter mixer, ribbon blender, V-type mixer, high-speed mixer, super mixer, turbosphere mixer, or jet mill may be used.

[0023] In the manufacturing method of this embodiment, the Ba / Ti molar ratio of the obtained first mixture is 0.990 or more and 0.994 or less. If the Ba / Ti molar ratio is greater than 0.994, BaCO2 in the first mixture ３ Because the quantity becomes excessively large, BaTiO ３ As the particle size of the powder becomes uneven, BaTiO ３ The roundness (sphericity) of the powder may decrease. This is because BaCO3 ３ ga TiO ２ This is because it promotes easier grain growth. BaCO3 promotes easier grain growth. ３ If a large amount is present, in the subsequent first heat treatment step, BaTiO ３ Before formation, BaCO ３ Grain growth progresses. ３ The presence of BaTiO reduces the uniformity of the distribution of Ba and Ti in the heat-treated material, resulting in BaTiO ３ This results in a non-uniform Ba / Ti ratio. In other words, in the first heat treatment step, Ba-rich BaTiO ３ Particles and Ti-rich BaTiO ３ A state in which particles are mixed is formed. Ba-rich BaTiO ３ Particles and Ti-rich BaTiO ３ Because the particles have different grain growth rates, the BaTiO synthesized in the first heat treatment step ３increases the variation in particle size, which becomes BaTiO, the final product ３ This leads to variation in particle size of the powder. In addition, the decrease in the uniformity of the distribution of Ba and Ti causes differences in growth rate among different parts even within a single particle, which results in a decrease in the circularity of the particles.

[0024] When the Ba / Ti molar ratio is less than 0.990, the TiO in the first mixture ２ becomes excessively excessive, so BaTiO ３ there is a risk that the production amount of composite oxides other than the above will increase. Such composite oxides are BaTiO ３ they remain as heterogeneous phases in the powder and may impair properties. In addition, BaTiO ３ there is a risk that physical properties such as crystallinity, tetragonality and circularity of the powder may deteriorate.

[0025] In contrast, when the Ba / Ti molar ratio of the first mixture is 0.990 or more and 0.994 or less, in combination with the effects in the subsequent steps (first heat treatment step, second mixing step, second heat treatment step), BaTiO having a relatively uniform particle size, high circularity and a low amount of heterogeneous phase can be obtained ３ it enables the synthesis of powder. From the viewpoint of further enhancing this effect, the Ba / Ti molar ratio of the first mixture is more preferably 0.990 or more and 0.992 or less. The Ba / Ti molar ratio of the first mixture is BaCO ３ powder and TiO ２ it can be controlled by adjusting the mixing ratio of the powder.

[0026] <First Heat Treatment Step> In the first heat treatment step, the first mixture is heat-treated (first heat treatment) to obtain barium titanate (BaTiO ３ ) to obtain a first heat-treated product containing. By the heat treatment, BaCO contained in the first mixture ３ carbon dioxide gas (CO ２ ) desorbs from the powder and changes to barium oxide (BaO). Then BaO reacts with TiO ２ reacts with the powder to form BaTiO ３ is formed. The first heat-treated product is BaTiO ３ , and in some cases further contains unreacted products (BaO, TiO ２ , etc.) and heterogeneous phases (BaTi ２ O５ , BaTi ４ O ９ , etc.).

[0027] In the production method of the present embodiment, the heat treatment temperature in the first heat treatment step is higher than 900°C and not higher than 1000°C. When the heat treatment temperature is higher than 1000°C, the grain growth of BaTiO ３ proceeds excessively in the first heat treatment step, making it difficult to obtain BaTiO ３ powder having a desired particle size. When the heat treatment temperature is 900°C or lower, the synthesis of BaTiO ３ becomes insufficient. Therefore, it becomes difficult to synthesize BaTiO ３ powder having high circularity (sphericity) and exhibiting excellent crystallinity and tetragonality. In addition, since synthesis does not proceed sufficiently in the first heat treatment step, the particle shape changes in subsequent steps (the second mixing step and the second heat treatment step), which also causes a problem that the variation in particle size of BaTiO ３ powder increases (the particle size becomes non-uniform). By setting the heat treatment temperature to higher than 900°C and not higher than 1000°C, it becomes possible to obtain BaTiO ３ powder having a relatively uniform particle size, high circularity, and further exhibiting excellent crystallinity and tetragonality. From the viewpoint of further enhancing the excellent effects of BaTiO ３ powder, the heat treatment temperature is more preferably 950°C or higher and 1000°C or lower. Within this temperature range, the reaction between BaCO ３ powder and TiO ２ powder proceeds more stably.

[0028] The heat treatment may be performed by a known method. A batch-type or continuous-type electric furnace or gas furnace, such as a roller hearth kiln, a rotary kiln, or a pusher furnace, can be used as the heat treatment furnace. The heat treatment time may be, for example, 10 minutes or more and 24 hours or less. The heat treatment may be performed in an air atmosphere, an inert gas atmosphere, a reduced-pressure atmosphere, a vacuum atmosphere, or a pressurized atmosphere.

[0029] <Second Mixing Step> In the second mixing step, the obtained first heat-treated product is mixed with an additional barium (Ba) source to obtain a second mixture. At this time, the Ba / Ti molar ratio of the obtained second mixture is adjusted to between 1.001 and 1.010. If the Ba / Ti molar ratio of the second mixture is less than 1.001, the composition will be excessively Ti-rich, resulting in the final product BaTiO ３ The Ba defects in the powder may increase, potentially reducing its crystallinity and tetragonal properties. Furthermore, if the Ba / Ti molar ratio of the second mixture exceeds 1.010, the composition becomes excessively Ba-rich, resulting in BaTiO2. ３ There is a risk that the amount of other complex oxides (different phases) being generated will increase.

[0030] In contrast, if the Ba / Ti molar ratio of the second mixture is between 1.001 and 1.010, then, in combination with the effects of the other steps (first mixing step, first heat treatment step, second heat treatment step), the resulting BaTiO will have high crystallinity and tetragonal properties, and a low amount of heterogeneous phases. ３ This enables the synthesis of powder. From the viewpoint of further enhancing this effect, a Ba / Ti molar ratio of 1.002 to 1.006 is more preferable for the second mixture. The Ba / Ti molar ratio of the second mixture can be controlled by adjusting the amount of additional Ba source added.

[0031] The additional Ba source is the final product, BaTiO ３ It is added for the purpose of controlling the composition of the powder. The type of Ba-containing material is not particularly limited, as long as it is suitable for this purpose. (e.g., barium carbonate (BaCO3)) ３ ) Dry powder, barium (Ba) slurry, barium nitrate (Ba(NO) ３ ) ２ ), barium hydroxide (Ba(OH) ２ Examples include barium compounds such as barium (Ba) alkoxides. Among these, Ba slurry and BaCO3 are also included. ３ At least one selected from the group consisting of dry powders is preferred, and Ba slurry is particularly preferred. Using Ba slurry achieves a more uniform mixing of the first heat-treated product and the additional Ba source. The Ba slurry is made of barium carbonate (BaCO3). ３ This is a slurry (suspension) obtained by placing the substance in an aqueous solvent and / or an organic solvent.

[0032] The mixing of the first heat-treated material and the additional Ba source may be carried out either dry or wet. However, it is preferable to use a wet method, which allows for more uniform mixing. Wet mixing can be carried out using known wet mixing equipment such as a ball mill, bead mill, attritor, vibratory mill, sand grind mill, or wet jet mill. As the mixed solvent, known solvents such as water, methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methyl ethyl ketone, methylene chloride, ethyl acetate, dimethylformamide, and dimethyl ether may be used. Furthermore, when using a Ba slurry as the additional Ba source, it is desirable that the mixed solvent is compatible with the dispersion medium of the Ba slurry. The mixed solvent may be a single solvent or a combination of multiple solvents. The materials to be treated (first heat-treated material and additional Ba source) may be pulverized during mixing.

[0033] <Second Heat Treatment Step> In the second heat treatment step, the obtained second mixture is heat-treated (second heat treatment) to obtain BaTiO ３ A second heat-treated product containing is obtained. The second heat treatment yields a second mixture containing BaTiO ３ The proportion increases. That is, the second mixture subjected to the second heat treatment contains the first heat-treated product and an additional Ba source. As mentioned above, the first heat-treated product is BaTiO ３ It also contains unreacted products (BaO, TiO ２ etc.) or different phases (BaTi ２ O ５ , BaTi ４ O ９ It may include (etc.). Therefore, when the second mixture is subjected to high-temperature heat treatment, the reaction proceeds between the additional Ba source, unreacted products, and other phases to form BaTiO ３ The proportion (degree of synthesis) of [the element] increases.

[0034] In the manufacturing method of this embodiment, the heat treatment temperature in the second heat treatment step is 700°C or higher and 900°C or lower. If the heat treatment temperature is below 700°C, the reaction of the second mixture (first mixture and additional Ba source) will be insufficient. Specifically, the migration of the additional Ba source to the Ba defects will not proceed smoothly, and as a result, the final product BaTiO ３The crystallinity of the powder decreases. Also, if the heat treatment temperature exceeds 900°C, BaTiO ３ Particle growth proceeds excessively. Therefore, BaTiO ３ The circularity of the powder decreases, and there is a risk that the uniformity of the particle size will be impaired. By setting the heat treatment temperature to 700°C to 900°C, a BaTiO with relatively uniform particle size, high circularity, and excellent crystallinity can be obtained. ３ It becomes possible to obtain powder. BaTiO ３ From the viewpoint of further enhancing the excellent effects of the powder, a heat treatment temperature of 700°C to 750°C is more preferable.

[0035] In this way, the barium titanate (BaTiO) of this embodiment ３ ) Powder can be obtained. That is, the second heat-treated product obtained in the second heat treatment step can be used as is. ３ It can be used as a powder. Alternatively, if necessary, the second heat-treated product can be subjected to post-treatment such as crushing, classification, or washing, and the resulting processed product can be converted into BaTiO ３ It may also be used as a powder.

[0036] The manufacturing method of this embodiment involves a solid-phase reaction using BaTiO ３ The synthesis of the powder is characterized by performing a relatively high-temperature heat treatment (first heat treatment) followed by a relatively low-temperature heat treatment (second heat treatment), and by controlling the composition of the raw material mixture (first mixture) and the intermediate product (second mixture) within a predetermined range. Through this process, BaTiO has a relatively uniform particle size, high circularity (sphericity), and excellent crystallinity and tetragonal properties. ３ Powder can be obtained.

[0037] As will be described later, circularity is measured using a scanning electron microscope (SEM) with BaTiO ３ Crystallinity is determined by observing the powder and analyzing the resulting particle projection image. Crystallinity is determined by comparing the crystallite size and the BET size. Furthermore, tetragonal properties are determined by X-ray diffraction of BaTiO ３ BaTiO contained in the powder ３The lattice constant in the a-axis direction (a) and the lattice constant in the c-axis direction (c) of the crystal are determined by X-ray diffraction and compared. In this case, the larger the lattice constant ratio (c / a), the better the tetragonal properties are judged to be.

[0038] The BaTiO of this embodiment ３ The powder has various advantageous features. For example, the BaTiO of this embodiment ３ Due to its high particle roundness (sphericity) and excellent tetragonal crystallinity, the powder is less prone to particle fracture such as cracking and chipping during processing in the manufacturing of electronic components. This is because the high particle roundness (sphericity) means there are fewer protrusions on the particle surface that can be the starting point for defect generation. Furthermore, its excellent tetragonal crystallinity results in relatively high particle hardness. And BaTiO has a low risk of particle fracture. ３ By using powder, it becomes possible to manufacture electronic components with excellent properties, such as multilayer ceramic capacitors (MLCCs) that have superior capacitance-temperature characteristics.

[0039] In contrast, conventional solid-phase reaction methods use BaTiO, which has high particle circularity and excellent tetragonal crystallinity. ３ Obtaining the powder was difficult. Therefore, there were limitations in preventing particle fracture. When particle fracture occurs, excessively fine particles are generated. Because these particles have a large surface area and high reactivity, they exert a large sintering driving force. Therefore, they are prone to causing abnormal grain growth that leads to performance degradation during heat treatment processes (such as firing processes) in the manufacturing of electronic components. In addition, because of their high reactivity, they are prone to causing undesirable reactions with other components. For example, BaTiO ３ When manufacturing multilayer ceramic capacitors using powder, fine particles generated by particle breakage may excessively react with additive components such as rare earth elements during the firing process, degrading the capacitance-temperature characteristics of the capacitor. Furthermore, these fine particles may cause abnormal grain growth during the firing process, leading to a decrease in the reliability of the capacitor. Additionally, BaTiO ３ When preparing a slurry by suspending powder in a solvent, there is a problem in that excessively fine particles can increase the viscosity of the slurry, making the manufacturing process difficult.

[0040] Note that BaTiO ３The presence of Ba defects in the powder lowers the lattice constant ratio (c / a). Therefore, even with conventional methods, BaTiO ３ By increasing the Ba / Ti ratio of the powder, the lattice constant ratio (c / a) can be increased, and as a result, it is possible to improve the tetragonal properties. However, simply increasing the Ba / Ti ratio is not sufficient. ３ The particle roundness (sphericity) of the powder tends to decrease. Therefore, it has been difficult to achieve both high particle roundness and excellent tetragonal properties using conventional methods.

[0041] Furthermore, the BaTiO of this embodiment ３ The powder has a relatively uniform particle size. Here, uniform particle size means that there is little variation in the particle size of the particles contained in the powder, that is, the width of the particle size distribution is narrow (sharp). Furthermore, the BaTiO of this embodiment ３ The powder exhibits excellent crystallinity. These characteristics contribute to improving the performance of electronic components. For example, thinning the dielectric ceramic layer is effective in manufacturing small, high-capacity multilayer ceramic capacitors. Furthermore, when fabricating the thinned dielectric ceramic layer, the raw material BaTiO ３ Powders require both fineness and uniform particle size. Powders with uneven particle size contain excessively fine particles, which makes them prone to abnormal grain growth during the firing process in the manufacturing of multilayer ceramic capacitors, leading to a degradation of reliability. ３ The powder is required to have high crystallinity. This is because powders with low crystallinity are highly reactive and may react excessively with additive components such as rare earth elements during the firing process, potentially degrading the capacitance temperature characteristics of the capacitor. In this respect, the BaTiO of this embodiment... ３ Using powder makes it possible to manufacture multilayer ceramic capacitors with excellent reliability and capacitance-temperature characteristics.

[0042] <<2. Barium titanate powder>> Barium titanate (BaTiO) of this embodiment ３ The powder has high roundness (sphericity). Specifically, the median particle roundness is preferably 0.8 or more and 1.0 or less. The median particle roundness can be determined by observation using a scanning electron microscope (SEM). Specifically, BaTiO３ The powder is observed using SEM to determine the projected area and perimeter of a single primary particle constituting the powder, and the circularity is calculated according to equation (2) below. The same procedure is performed for multiple particles to determine the circularity of each particle. The obtained circularity data are sorted in ascending order, and the value in the middle is determined as the median circularity.

[0043]

[0044] Although particles have a three-dimensional shape, in this embodiment, since the particle shape is determined based on a two-dimensional particle projection image obtained by SEM observation, "circularity" is used as an index of particle sphericity.

[0045] The BaTiO of this embodiment ３ The powder has a moderately fine and relatively uniform particle size. Specifically, the cumulative 50% diameter (Dv50) in the volume particle size distribution is preferably 180 nm to 300 nm. Furthermore, the ratio of the cumulative 10% diameter (Dn10) in the number particle size distribution to Dv50 (Dn10 / Dv50) is preferably 0.38 or higher, more preferably 0.42 or higher. There is no particular upper limit to the ratio (Dn10 / Dv50). However, if the particle size is excessively uniform, when the powder is molded to produce a molded body, the particle packing density may not increase, and the density of the molded body may decrease. From the viewpoint of avoiding such problems, the ratio (Dn10 / Dv50) may be 0.60 or lower.

[0046] The BaTiO of this embodiment ３ The powder exhibits relatively good crystallinity. Here, crystallinity is defined as BaTiO ３ The crystallite size of the powder can be evaluated by comparing its BET size. In other words, when the crystallite size is relatively large compared to the BET size, it can be judged that the crystallinity is superior.

[0047] Specifically, BaTiO ３ BaTiO contained in the powder ３The ratio of the BET diameter (specific surface area diameter) of the particles to the crystallite diameter of the crystal (BET diameter / crystallite diameter) is preferably 1.20 or more and 1.50 or less. The crystallite diameter is determined by analysis using powder X-ray diffraction (XRD). The BET diameter is BaTiO ３ It can be determined by measuring the specific surface area (SSA) of the powder. That is, assuming that the particles constituting the powder are spherical, the specific surface area (SSA) data and BaTiO ３ The BET diameter is calculated using the specific gravity (6.02).

[0048] The BaTiO of this embodiment ３ The powder exhibits excellent tetragonal properties in relation to particle size. Here, tetragonal properties are defined as BaTiO ３ BaTiO contained in the powder ３ The lattice constant in the a-axis direction (a) and the lattice constant in the c-axis direction (c) of the crystal are determined by X-ray diffraction and compared. A larger lattice constant ratio (c / a) indicates superior tetragonality. Specifically, the BaTiO that constitutes the powder... ３ The ratio (c / a) of the lattice constant in the c-axis direction to the lattice constant in the a-axis direction (a) of the crystal, and Dv50 satisfy the following relationship (1).

[0049]

[0050] The BaTiO of this embodiment ３ It is desirable that the composition (Ba / Ti molar ratio) of the powder be controlled within a predetermined range. Specifically, the Ba / Ti molar ratio is preferably 1.001 or more and 1.010 or less, and more preferably 1.002 or more and 1.006 or less.

[0051] The BaTiO of this embodiment ３ The powder is particularly suitable as a raw material for the dielectric ceramic layer of a multilayer ceramic capacitor (MLCC). In this embodiment, BaTiO ３ By using powder, it becomes possible to manufacture small, high-capacity multilayer ceramic capacitors with particularly excellent properties, such as temperature characteristics.

[0052] Figure 1 schematically shows the internal structure of a multilayer ceramic capacitor. The multilayer ceramic capacitor (1) has a laminate (4) which is made up of a plurality of stacked dielectric ceramic layers (2) and a plurality of internal electrode layers (3) extending between the dielectric ceramic layers (2) in an alternating stacked state. A pair of external electrodes (5) that function as terminal electrodes are provided at both ends of the laminate (4). Adjacent internal electrode layers (3) are electrically connected to one and the other of the pair of external electrodes (5) so that they are electrically separated from each other.

[0053] When a voltage is applied between one external electrode (5) and the other, a potential difference is generated between the internal electrodes (3) connected to each external electrode (5). As a result, capacitance is generated in the dielectric ceramic layer (3) sandwiched between the internal electrode layers (3), and the multilayer ceramic capacitor functions as a capacitive element (dielectric element).

[0054] However, the BaTiO of this embodiment ３ The powder is not limited to applications in the manufacture of multilayer ceramic capacitors. It goes without saying that it is also applicable to other known applications such as dielectric elements, piezoelectric elements, optoelectronic elements, and / or semiconductor elements.

[0055] <<3. Method for Manufacturing Multilayer Ceramic Capacitors>> This embodiment also covers a method for manufacturing multilayer ceramic capacitors. This manufacturing method involves using the method described above to produce barium titanate (BaTiO ３ ) A process to produce the powder (main component powder synthesis process), and the obtained barium titanate (BaTiO ３ The process comprises the steps of: mixing powder and solvent to produce a ceramic slurry (slurry preparation step); molding the obtained ceramic slurry to produce a dielectric green sheet (sheet formation step); forming a conductive pattern on the surface of the dielectric green sheet (conductive pattern formation step); stacking a plurality of dielectric sheets with conductive patterns on their surfaces to produce a green laminate (lamination step); and firing the green laminate to produce a laminate (firing step). The process may also include a step of forming external electrodes on the end faces of the laminate (external electrode formation step).

[0056] <Main component powder synthesis process> In the main component powder synthesis process, barium titanate (BaTiO) is synthesized using the method described above. ３ ) Powder is prepared (synthesized). That is, the following steps: barium carbonate (BaCO3) ３ ) powder and titanium dioxide (TiO ２ The first step involves mixing the powders to obtain a first mixture having a Ba / Ti molar ratio of 0.990 or more and 0.994 or less (first mixing step), and then heat-treating the obtained first mixture at a temperature of over 900°C and 1000°C or less to obtain barium titanate (BaTiO). ３ The process involves obtaining a first heat-treated product containing (first heat treatment step), mixing the obtained first heat-treated product with an additional barium (Ba) source to obtain a second mixture having a Ba / Ti molar ratio of 1.001 or more and 1.010 or less (second mixing step), and heat-treating the obtained second mixture at a temperature of 700°C or more and 900°C or less to obtain barium titanate (BaTiO). ３ A method comprising the step of obtaining a second heat-treated product containing (second heat treatment step) BaTiO ３ The powder is synthesized.

[0057] <Slurry Preparation Process> In the slurry preparation process, the obtained barium titanate (BaTiO) ３ A ceramic slurry is prepared by mixing the powder and the solvent. Organic solvents such as ethanol can be used as the solvent. The mixing and slurrying of the main component powder and the solvent can be carried out using known mixing and dispersion equipment such as a ball mill. In addition to the main component powder and the solvent, other components such as auxiliary component powders, organic binders, dispersants, and / or plasticizers may be added. Known raw material powders containing components such as magnesium (Mg), rare earth elements (Re), silicon (Si), manganese (Mn), and / or barium (Ba) can be used as auxiliary component powders. Known binder components such as polyvinyl butyral resin can be used as organic binders.

[0058] <Sheet Forming Process> In the sheet forming process, the obtained ceramic slurry is molded to produce a dielectric green sheet. Molding can be performed using known methods such as the doctor blade method or the lip method, in which the ceramic slurry is applied to and dried on a PET film. The fabricated dielectric green sheet then undergoes a subsequent firing process to become the dielectric ceramic layer of a multilayer ceramic capacitor.

[0059] <Conductive Pattern Formation Process> In the conductive pattern formation process, a conductive pattern is formed on the surface of the dielectric green sheet. Specifically, a conductive paste containing conductive metal powder such as nickel (Ni) powder is printed onto the surface of the dielectric green sheet to form a predetermined pattern. Printing can be done using known methods such as screen printing or gravure printing. The formed conductive pattern becomes the internal electrode layer of the multilayer ceramic capacitor after a subsequent firing process.

[0060] <Lamination Process> In the lamination process, a green laminate is created by laminating multiple dielectric green sheets, each having a conductive pattern on its surface. The number of dielectric green sheets to be laminated can be adjusted according to the number of dielectric layers in the multilayer ceramic capacitor to be manufactured. The green laminate may also have dielectric green sheets without conductive patterns on its upper and lower parts. During lamination, pressure may be applied to the entire green laminate to compress each layer constituting the laminate. Alternatively, the compressed laminate may be cut to create individual pieces of green laminate.

[0061] <Firing Process> In the firing process, the green laminate is fired to produce the laminate. The firing can be carried out by known methods. For example, the green laminate may be heated in a nitrogen (N2) atmosphere at a temperature of about 350°C to burn off organic components such as organic binders, and then fired at a temperature of about 1200°C. -9 ~10 -12 Alternatively, a hydrogen (H2)-nitrogen (N2)-water (H2O) gas with an oxygen partial pressure of approximately MPa may be introduced into the furnace, and calcination may be performed in a reducing atmosphere.

[0062] <External Electrode Formation Process> External electrodes may be formed on the end face of the obtained laminate. The external electrodes may be formed, for example, by applying a conductive paste to the end face where the internal electrode layer of the laminate is exposed and then baking it. The baking process electrically connects the internal electrode layer and the external electrodes. Alternatively, a plating layer may be provided on top of the baked conductive paste layer. Or, conductive paste may be applied to the end face of the green laminate obtained in the lamination process. In this case, by firing the green laminate to which the conductive paste has been applied, it becomes possible to form the laminate and external electrodes of the multilayer ceramic capacitor simultaneously.

[0063] In this way, the multilayer ceramic capacitor of this embodiment can be obtained.

[0064] The present invention will be described in more detail using the following examples. However, the present invention is not limited to the following examples.

[0065] (1) Production of barium titanate powder [Examples 1-3 and Comparative Examples 2-4] In Examples 1-3 and Comparative Examples 2-4, barium carbonate (BaCO3) was used. ３ ) powder, titanium dioxide (TiO ２ Using barium titanate (BaTiO) powder and an additional Ba source (Ba slurry or dry Ba carbonate powder) as raw materials, the process involves a first mixing step, a first heat treatment step, a second mixing step, and a second heat treatment step to produce barium titanate (BaTiO) ３ ) powder was synthesized. Furthermore, barium carbonate (BaCO3) was used as the Ba slurry. ３ A slurry was prepared by adding ) to toluene.

[0066] First, the specific surface area is 30 m². ２ / g BaCO ３ Powder with a specific surface area of ​​30 m² ２ / g of TiO ２ The powder is zirconia (ZrO ２ The mixture was wet-mixed in ekinen® using a ball mill equipped with media, and then dried to obtain a mixed powder (first mixture) (first mixing step). At this time, the Ba / Ti molar ratio of the first mixture was set to the values ​​shown in Table 1 below, using BaCO ３ Powder and TiO ２ The amount of powder used was adjusted.

[0067] The obtained first mixture was heat-treated in an air atmosphere using an electric furnace (batch furnace), and then allowed to cool naturally to obtain a heat-treated product (first heat-treated product) (first heat treatment step). In this process, the heat treatment (first heat treatment) was performed for 1 hour at the temperatures shown in Table 1 below.

[0068] Next, an additional Ba source is added to the obtained first heat-treated product, and ZrO ２ The mixture was wet-mixed and dispersed in ekinen® using a ball mill equipped with media, and then dried to obtain a dried powder (second mixture) (second mixing step). In this process, the materials shown in Table 1 below (Ba slurry or dried Ba carbonate powder) were used as the additional Ba source. The amount of the additional Ba source was adjusted so that the Ba / Ti molar ratio of the second mixture was the value shown in Table 1 below.

[0069] The obtained second mixture was heat-treated in an air atmosphere using an electric furnace, and then allowed to cool naturally to obtain a heat-treated product (second heat-treated product) (second heat treatment step). In this case, the heat treatment (second heat treatment) was carried out for 8 hours at the temperatures shown in Table 1 below. The obtained second heat-treated product was then treated with barium titanate (BaTiO2). ３ ) It was evaluated as a powder.

[0070] The Ba / Ti molar ratio of the mixtures (first mixture and second mixture) was determined by X-ray fluorescence analysis (XRF). Specifically, the composition of each mixture was examined using XRF, and the Ba / Ti molar ratio of the mixture was calculated based on the obtained analytical results.

[0071] [Comparative Example 1] In Comparative Example 1, BaCO2 ３ Powder and TiO ２ Using powder as a raw material, mixing and heat treatment are performed once each to produce BaTiO ３ The powder was synthesized.

[0072] First, the specific surface area is 30 m². ２ / g BaCO ３ Powder with a specific surface area of ​​30 m² ２ / g of TiO ２ The powder is ZrO ２The mixture was obtained by wet mixing in ekinen® using a ball mill equipped with media, followed by drying. At this time, the Ba / Ti molar ratio of the mixture (final mixture) was set to the values ​​shown in Table 1 below, using BaCO3. ３ Powder and TiO ２ The amount of powder used was adjusted.

[0073] The resulting mixture was heat-treated in an air atmosphere using an electric furnace (batch furnace), and then allowed to cool naturally to obtain the heat-treated product (final heat-treated product). During this process, the heat treatment was carried out for 1 hour at the temperatures shown in Table 1 below. The resulting heat-treated product was then processed using BaTiO2. ３ It was evaluated as a powder.

[0074] [Comparative Example 5] In Comparative Example 5, BaTiO was synthesized by hydrothermal synthesis. ３ The powder was synthesized. Specifically, barium hydroxide and titanium dioxide were reacted hydrothermally under high temperature and pressure (150-250°C) and then dried.

[0075]

[0076] (2) Evaluation: The BaTiO obtained in Examples 1 to 3 and Comparative Examples 1 to 5 ３ The various properties of the powder were evaluated using the following procedure.

[0077] <Specific surface area> Gas (N) measured by the single-point BET method ２ The specific surface area (SSA) was measured after adsorption. Furthermore, assuming that each particle is spherical, the obtained data and BaTiO ３ The BET diameter was calculated based on the specific gravity (6.02).

[0078] <XRD> BaTiO ３ The powder was analyzed by powder X-ray diffraction (XRD). The sample used for XRD analysis was BaTiO ３ The sample was prepared by leveling and molding the powder. XRD analysis was performed under the following conditions.

[0079] - Radiation source: CuKα - Background correction: Yes - Integration time: 1.0 s / step - X-ray output intensity: 1.6 kW - Step width: 0.01° / step

[0080] Then, the crystallite size is determined from the obtained XRD profile, and the ratio (BET size / crystallite size) is calculated as BaTiO ３ This was calculated as an indicator of the crystallinity of the powder.

[0081] Also, BaTiO ３ The lattice constants in the a-axis direction (a) and the c-axis direction (c) of the crystal were determined, and the lattice constant ratio (c / a) was calculated as an indicator of tetragonal structure. Then, the BaTiO obtained using the method described later was calculated. ３ Using the cumulative 50% diameter (Dv50) and lattice constant ratio (c / a) of the powder, BaTiO ３ The tetragonal properties of the powder were evaluated and determined according to the following criteria.

[0082] - Excellent tetragonal properties (○): c / a > 0.0000025 × Dv50 + 1.00925 - Poor tetragonal properties (×): c / a ≤ 0.0000025 × Dv50 + 1.00925

[0083] <Particle size (Dn10, Dv50) and circularity> BaTiO ３ The powder was observed using a scanning electron microscope (SEM), and the resulting SEM images were analyzed to determine the particle size of the primary particles constituting the powder. The SEM observation was performed at a magnification of 30,000x. During the image analysis, more than 300 particles were extracted, and the particle size of each particle was determined. Based on the obtained particle sizes, the particle size distribution based on the number of particles was determined, and the cumulative 10% from the finest particle side was defined as Dn10. Furthermore, the volume of each particle was calculated from the particle size to a spherical value, and based on the obtained volume, the particle size distribution based on volume was determined. The cumulative 50% diameter from the finest particle side was defined as Dv50.

[0084] Furthermore, the circularity of the primary particles constituting the powder was investigated by image analysis of the obtained SEM images. Specifically, more than 300 particles were extracted, and the projected area and perimeter of each particle were determined. Then, the circularity of each particle was calculated based on equation (2) below, and the median value was determined.

[0085]

[0086] <Capacitor Characteristics (MTTF)> BaTiO ３ Multilayer ceramic capacitors were fabricated using powder and their characteristics were evaluated. First, BaTiO３ Add a predetermined amount of MgO and Dy to the powder as an additive. ２ O ３ SiO ２ MnCO ３ BaCO ３ Adding, and further using polyvinyl butyral resin as an organic binder, ethanol as an organic solvent, and partially stabilized ZrO ２ The material was placed in a PVC pot along with the media (2 mm in diameter), mixed, and crushed to form a slurry.

[0087] The obtained slurry was formed into a sheet using the doctor blade method, and then punched out to a predetermined size to obtain a rectangular green sheet. The thickness of the green sheet was adjusted to 1 μm after firing. Next, a conductive paste with Ni powder as the conductive component was screen printed onto the obtained green sheet to form a conductive paste layer (internal electrode pattern) that would become the internal electrode layer after firing.

[0088] Then, a laminated block was fabricated by laminating green sheets with internal electrode patterns formed on them, and further laminating green sheets without internal electrode patterns as outer layers on both the upper and lower sides, and then pressing them together. The unfired laminate obtained by cutting this laminated block to the predetermined dimensions was heat-treated in air (350°C, 3 hours) to remove the binder, and then 10 －１０ MPa H ２ -N ２ -H ２ The laminate (ceramic laminate) was fired at 1200°C for 2 hours in a reducing atmosphere consisting of oxygen gas.

[0089] A conductive paste for forming external electrodes was applied to both ends of the fired laminate and baked, and then Ni and Sn were electroplated to form external electrodes that were electrically connected to the internal electrodes. A multilayer ceramic capacitor was fabricated in this manner. The fabricated multilayer ceramic capacitor had dimensions of length (L): 1.6 mm, width (W): 0.8 mm, and thickness (T): 0.8 mm, with an element thickness (thickness of the dielectric ceramic layer) of 1 μm and 320 layers of dielectric ceramic layers.

[0090] TC characteristic tests were performed on three multilayer ceramic capacitors prepared in each example and comparative example. The TC characteristic tests were conducted in a temperature range of -55 to 125°C under conditions of 25°C reference, 1kHz, and AC 0.5V, and the capacitance at -55°C (C(-55°C)), 25°C (C(25°C)), and 125°C (C(125°C)) was measured.

[0091] Based on the obtained data, ΔCAP(-55°C) and ΔCAP(125°C) were determined according to equations (3) and (4) below. Note that ΔCAP(-55°C) is the capacity temperature characteristic at -55°C (based on 25°C), and ΔCAP(125°C) is the capacity temperature characteristic at 125°C (based on 25°C).

[0092]

[0093] (3) Evaluation results <Powder properties> BaTiO of Examples 1-3 and Comparative Examples 1-5 ３ The physical properties of the powder are shown in Table 2 below. Also, BaTiO ３ Figure 2 shows the relationship between the cumulative 50% diameter (Dv50) of the powder and the lattice constant ratio (c / a).

[0094] Comparative Example 1 BaTiO ３ The powder was found to have a small lattice constant ratio (c / a) in relation to particle size, indicating poor tetragonality. Furthermore, the Dn10 / Dv50 ratio was small, resulting in non-uniform particle size. Comparative Example 2 exhibited poor tetragonality and relatively small circularity. Comparative Examples 3 and 4 also showed poor tetragonality. Comparative Example 5 had a very large Dn10 / Dv50 ratio. The particle size was excessively uniform, potentially leading to a decrease in particle packing density when molded.

[0095] In contrast, the BaTiO of Examples 1-3 ３ The powder exhibited high circularity and excellent tetragonal crystallinity. Furthermore, the BET diameter / crystallite diameter was within the desired range, indicating excellent crystallinity. Additionally, Dv50 and Dn10 / Dv50 were within the desired range, confirming appropriate particle size and uniformity.

[0096]

[0097] <Capacitor Characteristics> BaTiO of Example 1 and Comparative Example 1 ３ Table 3 below shows the capacitance-temperature characteristics (ΔCAP) of multilayer ceramic capacitors (MLCCs) fabricated using powder.

[0098] The capacitor in Example 1 had a larger ΔCAP at low temperatures (-55°C) compared to Comparative Example 1. Therefore, it was found to have a larger capacitance at low temperatures. Furthermore, the capacitor in Example 1 also had a larger ΔCAP at high temperatures (125°C) compared to Comparative Example 1 (although the absolute value was smaller). Therefore, it was found that the capacitance decrease at high temperatures was suppressed. From these results, it was confirmed that the capacitor in Example 1 has superior capacitance-temperature characteristics compared to Comparative Example 1.

[0099]

[0100] Based on the above results, according to this embodiment, BaTiO has a relatively uniform grain size, high circularity, and exhibits excellent crystallinity and tetragonal properties. ３ It is understood that a powder and a method for producing the same are provided.

[0101] 1. Multilayer ceramic capacitor 2. Dielectric ceramic layer 3. Internal electrode layer 4. Laminate 5. External electrode

Claims

1. Barium titanate (BaTiO) ３ A method for producing the powder, comprising the following steps: barium carbonate (BaCO3) ３ ) powder and titanium dioxide (TiO ２ ) A step of mixing powders to obtain a first mixture having a Ba / Ti molar ratio of 0.990 or more and 0.994 or less; The first mixture is heat-treated at a temperature of more than 900°C and less than or equal to 1000°C to obtain barium titanate (BaTiO) ３ The steps are: obtaining a first heat-treated product containing ), mixing the first heat-treated product with an additional barium (Ba) source to obtain a second mixture having a Ba / Ti molar ratio of 1.001 or more and 1.010 or less, and heat-treating the second mixture at a temperature of 700°C or more and 900°C or less to obtain barium titanate (BaTiO). ３ A method comprising the step of obtaining a second heat-treated product containing ).

2. The method according to claim 1, wherein in the step of obtaining the second mixture, the first heat-treated product and the additional barium source are mixed by a wet method.

3. The method according to claim 1 or 2, wherein the barium titanate powder has a cumulative 50% diameter (Dv50) in its volume particle size distribution of 180 nm or more and 300 nm or less.

4. The additional barium source is a barium (Ba) slurry and barium carbonate (BaCO3). ３ The method according to any one of claims 1 to 3, wherein the dry powder is at least one selected from the group consisting of dry powders.

5. Barium titanate powder having a median particle circularity of 0.8 or more and 1.0 or less, a cumulative 50% diameter (Dv50) in the volume particle size distribution of 180 nm or more and 300 nm or less, and a ratio of the cumulative 10% diameter (Dn10) in the number particle size distribution to Dv50 (Dn10 / Dv50) of 0.38 or more, a ratio of the BET diameter of the particles to the crystallite diameter of the barium titanate (BET diameter / crystallite diameter) of 1.20 or more and 1.50 or less, and the relationship between the ratio of the lattice constant in the c-axis direction (c) to the lattice constant in the a-axis direction (a) of the barium titanate (c / a) and Dv50 satisfying the following equation (1).

6. A method for manufacturing a multilayer ceramic capacitor, wherein the method is described in any one of claims 1 to 4, and the material is barium titanate (BaTiO ３ ) Steps to produce the powder, the barium titanate (BaTiO ３ A method comprising the steps of: mixing powder and solvent to produce a ceramic slurry; molding the ceramic slurry to produce a dielectric green sheet; forming a conductive pattern on the surface of the dielectric green sheet; stacking a plurality of the dielectric green sheets having conductive patterns on their surfaces to produce a green laminate; and firing the green laminate to produce a laminate.

7. A method for producing a multilayer ceramic capacitor, comprising the barium titanate (BaTiO ３ ) powder according to claim 5, comprising the steps of: preparing said barium titanate (BaTiO ３ ) powder and a solvent to produce a ceramic slurry; molding said ceramic slurry to produce a dielectric green sheet; forming a conductive pattern on a surface of said dielectric green sheet; laminating a plurality of said dielectric green sheets each having a conductive pattern provided on a surface thereof to produce a green laminate, and firing said green laminate to produce a laminate.

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