Multilayer ceramic electronic component and dielectric ceramic composition

Abstract

To provide a multilayer ceramic electronic component capable of improving bias characteristics while maintaining ferroelectricity.SOLUTION: A multilayer ceramic electronic component includes: a dielectric layer that has barium titanate as a main component, and has a core portion and a shell portion covering the core portion, in which calcium is solid dissolved in the shell portion, and includes a plurality of crystal grains in which a calcium concentration in the shell portion is 10 times or more a calcium concentration in the core portion; an internal electrode that is provided with the dielectric layer interposed therebetween, and has nickel or copper as a main component; and an external electrode that is electrically connected to the internal electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic electronic component and a dielectric ceramic composition. [Background technology]

[0002] BACKGROUND ART In high-frequency communication systems, such as mobile phones, multilayer ceramic electronic components such as multi-layer ceramic capacitors (MLCCs) are used to remove noise (see, for example, Patent Documents 1 to 10). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-226263 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-284571 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-161417 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-001859 [Patent Document 5] Japanese Patent Application Publication No. 2017-028225 [Patent Document 6] Japanese Patent Application Laid-Open No. 2013-180906 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-128372 [Patent Document 8] Japanese Patent Application Publication No. 2017-014093 [Patent Document 9] Japanese Patent Application Laid-Open No. 2006-151766 [Patent Document 10] Japanese Patent Application Laid-Open No. 2013-209239 Summary of the Invention [Problem to be solved by the invention]

[0004] Multilayer ceramic electronic components are broadly divided into Class I, which uses paraelectrics as the dielectric material, and Class II, which uses ferroelectrics. Class II multilayer ceramic electronic components, also known as high-dielectric-constant types, use materials with a high relative dielectric constant of several thousand or more, such as barium titanate (BaTiO3). This makes it possible to achieve extremely high capacitance density (capacitance per unit volume), and small, high-capacity multilayer ceramic electronic components have become common. However, because Class II multilayer ceramic electronic components are ferroelectrics, they have the characteristic that when a direct current (Dc Bias) voltage is applied, the capacitance decreases in proportion to the magnitude of the voltage (Dc Bias characteristic), making them unsuitable for high-voltage applications.

[0005] In recent years, the demand for high-rated voltage and high-capacity multilayer ceramic electronic components has grown for automotive applications, making it important to improve bias characteristics. Various material modification methods have been proposed to improve the bias characteristics of Class II multilayer ceramic electronic components. The primary method involves substituting some elements during the synthesis of barium titanate to create a compound that is different from barium titanate and using this as the main phase instead of barium titanate. Examples include Ba(Ti,Zr)O3, in which part of the titanium is replaced with zirconium (see, for example, Patent Document 1), and (Ba,Ca,Sr)TiO3, in which part of the barium is replaced with calcium and strontium (see, for example, Patent Document 2). Information on similar methods, such as BaZrO3 (see, for example, Patent Document 3), has also been published. Another method reported involves incorporating trace amounts of transition elements or alkaline earth elements into barium titanate (see, for example, Patent Documents 4 and 5). Methods have also been proposed that use materials corresponding to Class II, which have physical properties that are completely different from those of barium titanate due to their crystal structure. For example, materials with a tungsten bronze structure (see, for example, Patent Document 6). There have also been many reports of materials using bismuth or lead that have excellent bias properties (see, for example, Patent Documents 7 and 8).

[0006] However, all of the element-substituted barium titanate materials (e.g., Patent Documents 1-5) achieve moderate bias characteristics by significantly reducing the ferroelectricity of barium titanate. While this minimizes the rate of change of the dielectric constant with respect to bias, the crucial problem remains that the absolute value of the dielectric constant is too low. Materials with a different crystal structure from barium titanate (e.g., Patent Document 6) have a significantly lower dielectric constant than barium titanate before bias application, and thus, even if the rate of change of the dielectric constant is small, the absolute value of the dielectric constant is small. Materials containing bismuth or lead (e.g., Patent Documents 7 and 8) have varying absolute values ​​of the dielectric constant depending on the material composition, making them promising for bias characteristics. However, they cannot be co-fired with base metal electrodes such as nickel (reduction occurs in the dielectric). Bismuth-based materials are not suitable for mass production because the range of optimal oxygen partial pressure conditions is too narrow. Furthermore, bismuth and lead have high vapor pressures and evaporate during firing, particularly in a reducing atmosphere, which significantly affects the sinterability and electrical properties, resulting in unacceptable variations in properties between individual pieces.

[0007] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a multilayer ceramic electronic component that can improve the bias characteristics while maintaining ferroelectricity. [Means for solving the problem]

[0008] The multilayer ceramic electronic component according to the present invention comprises a dielectric layer containing barium titanate as a main component, a core portion, and a shell portion covering the core portion, wherein calcium is dissolved in the shell portion and the shell portion contains a plurality of crystal grains having a calcium concentration 10 times or more that of the core portion; internal electrodes sandwiching the dielectric layer and containing nickel or copper as a main component; and external electrodes electrically connected to the internal electrodes.

[0009] In the above-described multilayer ceramic electronic component, the shell portion may contain at least one of gadolinium, dysprosium, holmium, and yttrium.

[0010] In the above-described multilayer ceramic electronic component, silicon and at least one of aluminum, magnesium, and manganese may be contained at grain boundaries or grain boundary triple junctions, which are boundaries between the plurality of crystal grains.

[0011] In the above-described monolithic ceramic electronic component, the average grain size of the plurality of crystal grains may be not less than 50 nm and not more than 400 nm.

[0012] In the above-described multilayer ceramic electronic component, the dielectric layers may include sub-crystal grains having a structure different from that of the plurality of crystal grains.

[0013] In the above-described multilayer ceramic electronic component, the shell portion may further contain strontium.

[0014] In the above-described monolithic ceramic electronic component, the shell portion may further contain strontium, and the ratio of strontium to the sum of strontium and calcium in the shell portion may be 0.2 or more and 0.4 or less.

[0015] The ceramic composition of the present invention has barium titanate as its main component, a core portion, and a shell portion covering the core portion, and contains a plurality of crystal particles in which calcium is dissolved in the shell portion and the calcium concentration in the shell portion is 10 times or more the calcium concentration in the core portion. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a multilayer ceramic electronic component that can improve the bias characteristics while maintaining ferroelectricity. [Brief explanation of the drawings]

[0017] [Figure 1]1 is a schematic cross-sectional view illustrating a dielectric ceramic composition according to a first embodiment. [Figure 2] FIG. 10 is a diagram illustrating an example of a bias characteristic. [Figure 3] 10A is a diagram illustrating Case 1, and FIG. 10B is a diagram illustrating Case 2. FIG. [Figure 4] FIG. 1 is a diagram illustrating grain boundaries and triple junctions. [Figure 5] FIG. 2 is a partial cross-sectional perspective view of a multilayer ceramic capacitor. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 7] FIG. 6 is a cross-sectional view taken along line BB in FIG. 5. [Figure 8] (a) and (b) are enlarged views of the XZ cross section. [Figure 9] 1A to 1C are diagrams illustrating a flow of a method for manufacturing a multilayer ceramic capacitor. [Figure 10] 10(a) and 10(b) are diagrams illustrating an internal electrode forming step. [Figure 11] 10A to 10C are diagrams illustrating a crimping step. [Figure 12] FIG. 1 is a diagram showing an element map of Example 1-1. [Figure 13] FIG. 1 is a diagram showing an element map of Comparative Example 1-1. [Figure 14] FIG. 10 is a diagram showing an element map obtained by TEM-EDX analysis in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments will be described with reference to the drawings.

[0019] (First embodiment) FIG. 1 is a schematic cross-sectional view illustrating a dielectric ceramic composition according to the first embodiment. As illustrated in FIG. 1, the dielectric ceramic composition includes crystal grains 30 having a core-shell structure. The crystal grains 30 having a core-shell structure include a substantially spherical core portion 31 and a shell portion 32 that surrounds and covers the core portion 31. The core portion 31 is a crystalline portion in which the additive compound is not dissolved or in which the amount of the additive compound dissolved is small. The shell portion 32 is a crystalline portion in which the additive compound is dissolved and has a higher additive compound concentration than the additive compound concentration in the core portion 31. The additive compound concentration in the shell portion 32 is higher than the additive compound concentration in the core portion 31. Alternatively, the additive compound is diffused in the shell portion 32, but not in the core portion 31.

[0020] In this embodiment, the crystal particle 30 is mainly composed of barium titanate. For example, the crystal particle 30 contains 90 at % or more of barium titanate. Calcium is dissolved in the shell portion 32. The calcium concentration in the shell portion 32 is 10 times or more the calcium concentration in the core portion 31.

[0021] This configuration improves the bias characteristics without excessively lowering the dielectric constant of the dielectric ceramic composition, thereby achieving a high dielectric constant under high electric fields. In other words, the bias characteristics can be improved while maintaining ferroelectricity. For example, as illustrated in FIG. 2, while other materials (such as materials with a typical barium titanate-based phase or a typical core-shell structure) exhibit a decrease in capacitance as the applied voltage increases, the ceramic composition according to this embodiment can suppress the decrease in capacitance even when the applied voltage increases. For example, a high absolute value of the dielectric constant (e.g., 930 @ 10 V / μm) that cannot be achieved with other materials can be achieved at 10 V / μm or higher. Furthermore, at 10 V / μm, if the capacitance of the ceramic composition according to this embodiment is Cn and the capacitance of the other material is C0, then Cn / C0 ≧ 1.5. The use of base metal internal electrodes does not pose any problems.

[0022] Furthermore, it is possible to extend the material life by simultaneously incorporating a rare earth element such as holmium into the shell portion 32. In addition, since there is a high degree of freedom in the grain boundary composition, it is possible to further improve the life without deteriorating the bias characteristics (particle characteristics) by arranging aluminum, magnesium, or manganese in addition to silicon at the grain boundaries.

[0023] These features make it possible to design multilayer ceramic electronic components with base-metal internal electrodes that are ideal for applications requiring high reliability, in addition to high effective capacitance under high voltages, such as in automotive applications.

[0024] Here, the differences between the dielectric ceramic composition according to this embodiment and other materials will be explained. First, the other materials will be classified into Case 1 and Case 2. The crystal grain in FIG. 3(a) is Case 1, having a core portion 201 of barium titanate, but having a shell portion 202 in which calcium is not solid-dissolved. Typically, the main component of the additive to the shell portion 202 is magnesium. The crystal grain in FIG. 3(b) is Case 2, having a core-shell structure resulting from the solid-solution of a rare earth element in a core portion 203 mainly composed of (Ba,Ca)TiO3.

[0025] First, we will explain the problem in Case 1. In Case 1, the core part 201 is made of barium titanate, and the shell part 202 is made of Mg 2+ , Mn 2+ Ti 4+ When composed of low valent cations substituting the Ti site, the shell portion 202 4+ The shell portion 202 becomes an acceptor type shell, and oxide ion defects are generated due to the electrically neutral condition. The oxide ion defects can pin polarization, deteriorating the bias characteristics, or cause insulation degradation by migration under an electric field. On the other hand, when the shell portion 202 is V 5+ and Nb 5+ Ti 4+If the shell 202 is composed of high-valent cations substituting the sites, it becomes a donor type. In this case, oxide ion defects are not formed, but the insulating properties are reduced due to the excess electrons injected. Therefore, a design is usually made to maintain a balance of properties by arranging acceptor-type and donor-type cations in the shell in a balanced manner.

[0026] In this regard, in the ceramic composition according to the present embodiment, Ca, which is an additive element to the shell portion 32, is used. 2+ Ha, Ba 2+ Since it is a cation that substitutes the site with the same valence, it does not become either an acceptor or a donor. 2+ The ionic radius of Ba 2+ Since the ionic radius of calcium is smaller than that of BaTiO3, the volume of the crystal lattice with a perovskite structure contracts when calcium dissolves in it. This strengthens the bond between the oxide ions and cations, which has the effect of suppressing electric field migration of oxide ion defects. In other words, it is possible to achieve a high level of balance between bias characteristics, insulation properties, and reliability.

[0027] Next, we will explain the issues surrounding Case 2. Because the original particles are not barium titanate but (Ba,Ca)TiO3, the core portion 203 is (Ba,Ca)TiO3. When rare earth elements or other elements are dissolved from outside the particles, a calcium-containing shell portion 204 is formed. However, because the core portion 203 is (Ba,Ca)TiO3, it requires more energy to reverse polarization than BaTiO3. Therefore, the dielectric constant is inherently low, and multilayer ceramic electronic components with a smaller capacitance can only be designed compared to the present embodiment, which has a high-dielectric-constant BaTiO3 core. Structurally, Case 2 is completely different from the ceramic composition of the present embodiment. This is because, in a structure with a (Ba,Ca)TiO3 core, the calcium concentrations in the core and shell are essentially equal, and the core and shell are not differentiated by calcium concentration.

[0028] Patent Document 9 also discloses a structure in which calcium diffuses from the exterior to the interior of BaTiO3 by adding CaZrO3 (or CaO and ZrO2). This document states that, in order to achieve temperature characteristics within the X8R range, the thickness of the calcium diffusion region must be within 10% to 30% of the particle diameter at D50%. This document also claims to improve the "Dc bias characteristics." However, the phenomenon referred to as "Dc bias characteristics" in this document refers to the "change in the dielectric constant over time under a Dc electric field." This is different from the Bias characteristic described in this specification, which is the phenomenon in which the dielectric constant decreases due to the application of an external Dc electric field (nonlinear dielectric constant characteristics). The former "change in the dielectric constant over time under a Dc electric field" is generally referred to as the "Dc aging characteristic" or "Dc bias aging characteristic." The present embodiment improves the DcBias characteristic, a "static characteristic," rather than "aging," and the target effect is completely different from that of the literature. The present embodiment also differs in that it does not limit the thickness of the shell portion 32, but rather prefers a thickness distribution. While the literature specifies the inclusion of "at least one element selected from Sc, Er, Tm, Yb, and Lu" as a rare earth element, these rare earth elements are not required for the ceramic composition of the present embodiment. Patent Document 10 lists Ca as one of the shell constituent elements, with the requirement that Tb and Yb be included (the example shows only an Mg shell). However, like Patent Document 9, this is designed to ensure the temperature characteristics of X8R, and does not improve the bias characteristics. In particular, Tb and Yb do not provide the bias improvement effect of the ceramic composition of the present embodiment.

[0029] The calcium concentrations in the core region 31 and the shell region 32 can be measured by the following method. First, elemental mapping of calcium is performed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray spectroscopy (EDX) detector. With this structure, a clear contrast is obtained between the core region 31 at the center of the particle, where almost no calcium is detected, and the shell region 32, where a large amount of calcium is detected (see, for example, Figures 12 and 14). By quantitatively analyzing the centers of the thus-distinguished core region 31 and shell region 32 using EDX, the calcium concentration in each region can be determined. This is performed for 10 particles, and the average calcium concentration in each region of the core region 31 and shell region 32 is calculated. If the average calcium concentration in the shell region 32 is 10 times or more higher than that of the core region 31, this structure is determined.

[0030] The calcium concentration in the shell portion 32 is preferably 20 times or more, and more preferably 40 times or more, the calcium concentration in the core portion 31 .

[0031] In the crystal particles 30, the amount of calcium relative to 100 mol of barium titanate is preferably 1.0 mol to 5.0 mol, more preferably 1.6 mol to 4.5 mol, and even more preferably 2.0 mol to 4.0 mol.

[0032] From the viewpoint of extending the material life, the shell portion 32 of the ceramic composition according to this embodiment preferably contains a rare earth element. For example, the shell portion 32 preferably contains at least one of gadolinium, dysprosium, holmium, and yttrium. In the shell portion 32, the amount of these rare earth elements is preferably 0.5 mol% to 2.0 mol%, more preferably 0.8 mol% to 1.5 mol%, and even more preferably 1.0 mol% to 1.2 mol%, relative to 100 mol of barium titanate.

[0033] To ensure reliability, it is preferable that an additive element be present at the grain boundary of the crystal grain 30. For example, as illustrated in FIG. 4, it is preferable that silicon be present at the grain boundary 33 or grain boundary triple junction 34 between the crystal grain 30 and another crystal grain. Furthermore, it is preferable that at least one of aluminum, magnesium, and manganese be present at the grain boundary 33 or grain boundary triple junction 34. The grain boundary 33 is the boundary between two crystal grains. The grain boundary triple junction 34 is the boundary between three or more crystal grains.

[0034] In the magnetic composition according to this embodiment, the amount of silicon is preferably 0.5 mol to 3.0 mol per 100 mol of barium titanate. The total amount of grain boundary components other than silicon (one or more of aluminum, magnesium, and manganese) is preferably 1.0 mol to 5.0 mol, more preferably 1.5 mol to 4.0 mol, and even more preferably 2.0 mol to 3.0 mol.

[0035] From the viewpoint of maintaining the core-shell structure, it is preferable to set a lower limit to the average particle size of the crystal particles. In this embodiment, when a plurality of crystal particles 30 are sintered together in the ceramic composition, the average particle size of the plurality of crystal particles 30 is preferably 50 nm or more, more preferably 80 nm or more, and even more preferably 100 nm or more.

[0036] On the other hand, from the viewpoint of ensuring sinterability, it is preferable to set an upper limit to the average particle size of the crystal particles. In this embodiment, when a plurality of crystal particles 30 are sintered to each other in the ceramic composition, the average particle size of the plurality of crystal particles 30 is preferably 400 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less.

[0037] The average grain size of the crystal grains 30 in the ceramic composition can be measured by the following method. First, the cross section is photographed using a SEM (scanning electron microscope), and the maximum horizontal distance between each grain and the electrode surface is measured. This is done for 100 grains, and the average value is calculated.

[0038] Furthermore, the ceramic composition according to this embodiment preferably contains sub-crystal grains having a structure different from that of the crystal grains 30. For example, as illustrated in Fig. 4, the ceramic composition according to this embodiment preferably contains sub-crystal grains 35. Note that the sub-crystal grains 35 have a structure different from that of the crystal grains 30 in that, when calcium element mapping is performed by TEM-EDX, core portions 31, which are regions with almost no calcium, are not observed, and the sub-crystal grains 35 have a smaller particle size than the average particle size.

[0039] Furthermore, when the ceramic composition according to this embodiment has a structure in which multiple crystal grains 30 are sintered, it is preferable that the width of the shell portion 32 of each crystal grain 30 be distributed. For example, it is preferable that the width of the shell portion 32 be large in some crystal grains 30 and small in other crystal grains 30. In this case, the electric field strength required to reverse the polarization of the crystal grains 30 is distributed, thereby easing the decrease in capacitance with increasing Bias. This makes it possible to design a high relative permittivity over a wide electric field range. For example, for multiple crystal grains 30, the difference between the minimum and maximum widths of each shell portion 32 is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. The width of the shell portion 32 can be determined by observing the cross section with a TEM and performing line analysis of the calcium and silicon concentrations from the core center to the grain boundary, passing through the center of the particle. An electron beam is scanned from the center of the core portion 31 toward the grain boundary, and the point at which the calcium concentration at the core center becomes 10 times higher is defined as the boundary between the core portion 31 and the shell portion 32. The electron beam is then scanned from the shell portion 32 toward the grain boundary, and the point where the silicon concentration is detected to be 10 times higher than that in the shell portion 32 is defined as the boundary between the shell portion 32 and the grain boundary. Since silicon is an element that does not dissolve in the main phase, the actual silicon concentration distribution is usually such that it is detected at the grain boundary below the detection limit in the shell portion 32. The distance between the core portion / shell portion boundary and the shell portion / grain boundary boundary (including the boundary point) thus determined is defined as the width of the shell portion 32.

[0040] Moreover, from the viewpoint of further improving the bias characteristics, the crystal particles according to this embodiment preferably contain strontium in the shell portion 32.

[0041] Furthermore, by adding strontium so that the atomic concentration ratio of strontium to the sum of strontium and calcium is 0.2 or more, the bias characteristics are significantly improved. However, as the amount of strontium added increases, the capacitance-temperature characteristics deteriorate. Therefore, it is preferable to set the atomic concentration ratio of strontium to the sum of strontium and calcium to 0.4 or less. In this case, the capacitance-temperature characteristics can be made to comply with EIA standard X7T.

[0042] (Second embodiment) FIG. 5 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 100 in accordance with the second embodiment. FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. FIG. 7 is a cross-sectional view taken along line BB in FIG. 5. As illustrated in FIGS. 5 to 7, the multilayer ceramic capacitor 100 comprises an element body 10 having a substantially rectangular parallelepiped shape, and external electrodes 20a, 20b provided on two opposing end faces of the element body 10. Of the four faces of the element body 10 other than the two end faces, the two faces other than the top and bottom faces in the stacking direction are referred to as side faces. The external electrodes 20a, 20b extend on the top, bottom and two side faces in the stacking direction of the element body 10. However, the external electrodes 20a, 20b are spaced apart from each other.

[0043] 5 to 7, the Z-axis direction (first direction) is the stacking direction, and is the direction in which the internal electrode layers face each other. The X-axis direction (second direction) is the length direction of the element body 10, and is the direction in which the two end faces of the element body 10 face each other, and is the direction in which the external electrodes 20a and 20b face each other. The Y-axis direction (third direction) is the width direction of the internal electrode layers, and is the direction in which the two side faces other than the two end faces of the four side faces of the element body 10 face each other. The X-axis direction, Y-axis direction, and Z-axis direction are perpendicular to each other.

[0044] The element body 10 has a configuration in which dielectric layers 11 containing a ceramic material that functions as a dielectric and internal electrode layers 12 are alternately stacked. The edges of each internal electrode layer 12 are alternately exposed to the end face of the element body 10 where the external electrode 20a is provided and the end face where the external electrode 20b is provided. As a result, each internal electrode layer 12 is alternately electrically connected to the external electrode 20a and the external electrode 20b. As a result, the multilayer ceramic capacitor 100 has a configuration in which multiple dielectric layers 11 are stacked with the internal electrode layers 12 interposed therebetween. In addition, in the laminate of the dielectric layers 11 and the internal electrode layers 12, the internal electrode layer 12 is arranged as the outermost layer in the stacking direction, and the upper and lower surfaces of the laminate are covered with cover layers 13. The cover layers 13 are primarily composed of a ceramic material. For example, the cover layers 13 may have the same or different composition as the dielectric layers 11. Note that the configurations are not limited to those shown in FIGS. 5 to 7, as long as the internal electrode layers 12 are exposed on two different surfaces and are electrically connected to different external electrodes.

[0045] The size of the multilayer ceramic capacitor 100 is, for example, 0.25 mm in length, 0.125 mm in width, and 0.125 mm in height, or 0.4 mm in length, 0.2 mm in width, and 0.2 mm in height, or 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, or 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height, or 3.2 mm in length, 1.6 mm in width, and 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width, and 2.5 mm in height, but is not limited to these sizes.

[0046] The internal electrode layers 12 are mainly composed of base metals such as nickel (Ni), copper (Cu), tin (Sn), or alloys containing these. The internal electrode layers 12 may also be made of precious metals such as platinum (Pt), palladium (Pd), silver (Ag), or gold (Au), or alloys containing these. The average thickness of each internal electrode layer 12 in the Z-axis direction is, for example, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less. The thickness of the internal electrode layers 12 can be measured by observing a cross section of the multilayer ceramic capacitor 100 with a scanning electron microscope (SEM), measuring the thickness at 10 points for each of 10 different internal electrode layers 12, and calculating the average value of all the measurement points.

[0047] The dielectric layers 11 are made of the ceramic composition according to the first embodiment. The thickness of the dielectric layers 11 is, for example, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less. The thickness of the dielectric layers 11 can be measured by observing a cross section of the multilayer ceramic capacitor 100 with a scanning electron microscope (SEM), measuring the thickness at 10 points for each of 10 different dielectric layers 11, and deriving the average value of all the measurement points.

[0048] An additive may be added to the dielectric layer 11. Examples of additives to the dielectric layer 11 include oxides of zirconium (Zr), hafnium (Hf), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)), oxides containing cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), or silicon (Si), or glasses containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon.

[0049] 6, the region where the internal electrode layer 12 connected to the external electrode 20a and the internal electrode layer 12 connected to the external electrode 20b face each other is a region where capacitance is generated in the multilayer ceramic capacitor 100. Therefore, this region where capacitance is generated is referred to as a capacitance portion 14. In other words, the capacitance portion 14 is a region where adjacent internal electrode layers 12 connected to different external electrodes face each other.

[0050] The region where the internal electrode layers 12 connected to the external electrode 20a face each other without an internal electrode layer 12 connected to the external electrode 20b interposed therebetween is called the end margin 15. The region where the internal electrode layers 12 connected to the external electrode 20b face each other without an internal electrode layer 12 connected to the external electrode 20a interposed therebetween is also the end margin 15. In other words, the end margin 15 is the region where the internal electrode layers 12 connected to the same external electrode face each other without an internal electrode layer 12 connected to a different external electrode interposed therebetween. The end margin 15 is a region where no capacitance is generated.

[0051] 7, in the element body 10, the side margins 16 are regions provided so as to cover the ends (ends in the Y-axis direction) of two side surfaces of the dielectric layers 11 and the internal electrode layers 12. In other words, the side margins 16 are regions provided outside the capacitive section 14 in the Y-axis direction. The side margins 16 are also regions that do not generate capacitance.

[0052] FIG. 8(a) is an enlarged cross-sectional view of the external electrode 20a and its vicinity. FIG. 8(b) is an enlarged cross-sectional view of the external electrode 20b and its vicinity. Hatching is omitted in FIGS. 8(a) and 8(b). As illustrated in FIGS. 8(a) and 8(b), the external electrodes 20a and 20b have a structure in which a plating layer 22 is provided on an underlayer 21. The underlayer 21 is primarily composed of nickel, copper, or the like. The underlayer 21 may contain ceramic particles or a glass component as an additional material. The plating layer 22 is primarily composed of a metal such as nickel, copper, aluminum, zinc, or tin, or an alloy of two or more of these metals. The plating layer 22 may be a plating layer of a single metal component, or multiple plating layers of different metal components. For example, the plating layer 22 has a structure in which a first plating layer 23, a second plating layer 24, and a third plating layer 25 are formed in this order from the underlayer 21 side. The first plating layer 23 is, for example, a copper plating layer. The second plating layer 24 is, for example, a nickel plating layer, and the third plating layer 25 is, for example, a tin plating layer.

[0053] In the multilayer ceramic capacitor 100, since the dielectric layers 11 contain the ceramic composition according to the first embodiment, it is possible to improve the bias characteristics while maintaining the ferroelectricity.

[0054] Next, a description will be given of a method for manufacturing the multilayer ceramic capacitor 100. FIG.

[0055] (Dispersion process of shell components) The shell component to be added to the shell portion 32 is dispersed in zirconia beads and ethanol. The shell component is a material containing calcium, such as CaCO3. The shell component may also contain a rare earth element such as Ho2O3. The liquid from which the zirconia beads are separated after dispersion is designated as Liquid A.

[0056] (Dispersion process of grain boundary components) Next, the grain boundary components are dispersed in zirconia beads and ethanol. The grain boundary components are, for example, silicon-containing materials such as SiO2. The grain boundary components may also contain MnCO3, MgO, Al2O3, etc. After dispersion, the liquid from which the zirconia beads are separated is designated as Liquid B.

[0057] (Mixing process) Next, barium titanate powder is mixed with Liquid A, and toluene and a dispersant are added, followed by dispersion with zirconia beads. For example, the barium titanate is dispersed until the D50% particle diameter of its particle size distribution becomes the primary diameter. After dispersion, the liquid from which the zirconia beads are separated is called Liquid C.

[0058] (stirring process) Combine solution B and solution C in a tank and mix using a propeller.

[0059] (Ultrasonic dispersion process) Next, an organic binder such as polyvinyl butyral (PVB) is mixed with the liquid obtained in the stirring process, and ultrasonic waves are applied to turn it into an organic slurry.

[0060] (Coating process) Next, the obtained organic slurry is used to coat a ceramic green sheet 51 on a substrate by, for example, a die coater method or a doctor blade method, and then dried. The substrate is, for example, a polyethylene terephthalate (PET) film. Figures illustrating the coating process are omitted.

[0061] (Internal electrode formation process) Next, as shown in FIG. 10(a), a metal conductive paste containing an organic binder for forming internal electrodes is printed on the surface of the ceramic green sheet 51 by screen printing, gravure printing, or the like, to form an internal electrode pattern 52 that alternately leads to a pair of external electrodes with opposite polarities. Ceramic particles are added to the metal conductive paste as a co-material. The main component of the ceramic particles is not particularly limited, but is preferably the same as the main ceramic component of the dielectric layer 11. For example, barium calcium titanate with an average particle diameter of 50 nm or less may be uniformly dispersed.

[0062] Next, a binder such as an ethyl cellulose-based binder and an organic solvent such as a terpineol-based binder are added to the dielectric ceramic composition obtained in the raw material powder preparation step, and the mixture is kneaded in a roll mill to obtain a dielectric pattern paste for the reverse pattern layer. As illustrated in Figure 10(a), a dielectric pattern paste is printed on a ceramic green sheet 51 in the peripheral area where the internal electrode pattern 52 is not printed, thereby arranging the dielectric pattern 53 and filling in the gap with the internal electrode pattern 52. The ceramic green sheet 51 on which the internal electrode pattern 52 and the dielectric pattern 53 are printed is called a lamination unit.

[0063] 10(b), the lamination units are laminated so that the internal electrode layers 12 and the dielectric layers 11 are alternately arranged, and so that the edges of the internal electrode layers 12 are alternately exposed at both longitudinal end faces of the dielectric layers 11 and alternately drawn out to a pair of external electrodes 20a, 20b having opposite polarities. For example, the number of laminated layers of the internal electrode pattern 52 is set to 100 to 1000.

[0064] (Crimping process) As shown in Fig. 11, a predetermined number of cover sheets 54 (for example, 2 to 10 layers) are laminated on the top and bottom of a laminate in which lamination units are stacked, and then thermocompression bonded. As an example of the ceramic material for the cover sheets 54, the above-mentioned dielectric ceramic composition can be used. Thereafter, the laminate is cut to a predetermined chip size (for example, 1.0 mm x 0.5 mm).

[0065] (Firing process) The ceramic laminate thus obtained is subjected to binder removal treatment in an N2 atmosphere, air atmosphere, or the like, and then a metal paste that will become the base layer of the external electrodes 20a, 20b is applied by dipping, and the metal paste is then applied under an oxygen partial pressure of 10 -10 ~10 -7 The mixture is then fired in a reducing atmosphere at 1100 to 1300° C. for 10 minutes to 2 hours at 1 atm. In this way, the multilayer ceramic capacitor 100 is obtained.

[0066] (Reoxidation treatment process) Thereafter, a re-oxidation treatment may be performed at 600°C to 1000°C in an N2 gas atmosphere.

[0067] (Plating process) Thereafter, the underlying layers of the external electrodes 20a, 20b are plated with a metal coating of Cu, Ni, Sn, etc. Through the above steps, the multilayer ceramic capacitor 100 is completed.

[0068] According to the manufacturing method of this embodiment, the dispersion process of the shell component and the dispersion process of the grain boundary component are carried out independently. This prevents the grain boundary component from dissolving in barium titanate during firing. As a result, it is possible to produce the magnetic composition described in FIG.

[0069] Furthermore, the median diameter of barium titanate and the dispersion of the shell component (liquid A) can be adjusted independently. This allows the width of the shell portion 32 after sintering to be controlled, and the width of the shell portion 32 of each crystal particle 30 can be distributed. For example, the width of the shell portion 32 can be increased in some crystal particles 30 and decreased in other crystal particles 30. In this case, the electric field strength required to reverse the polarization of the crystal particles 30 can be distributed, resulting in a gradual decrease in capacitance with increasing bias. This makes it possible to design a high relative permittivity over a wide electric field range.

[0070] In the above embodiments, a multilayer ceramic capacitor has been described as an example of a multilayer ceramic electronic component, but the present invention is not limited to this. For example, other multilayer ceramic electronic components such as a varistor or a thermistor may also be used. [Example]

[0071] The multilayer ceramic capacitor according to the embodiment was fabricated and its characteristics were examined.

[0072] (Example 1-1) First, the shell components, CaCO3 and Ho2O3, were weighed out so that they would be 2.0 mol and 0.5 mol, respectively, per 100 mol of BaTiO3, and dispersed in zirconia beads and ethanol to produce Solution A. Similarly, the grain boundary components (SiO2, MnCO3, MgO, Al2O3) were weighed out so that they would be 1.0 mol, 0.5 mol, 0.5 mol, and 0.5 mol, respectively, per 100 mol of BaTiO3, and dispersed in zirconia beads and ethanol. The slurry was then separated from the zirconia beads to produce Solution B.

[0073] Next, BaTiO3 powder with an average particle size of 150 nm was mixed with Liquid A, toluene, and a dispersant, and dispersed using zirconia beads. Dispersion was stopped when the median diameter of the BaTiO3 particle size distribution reached 150 nm. The dispersed slurry was passed through a filter to separate the zirconia beads, and then mixed with Liquid C, which had been prepared in advance, in a tank and stirred. PVB resin was then added as a binder, and ultrasonic dispersion was carried out.

[0074] The slurry thus prepared was applied to a PET film using a die coater to form a 4.0 μm thick ceramic green sheet. After drying, the ceramic green sheet was printed with nickel paste to form an internal electrode pattern. 11 layers of the printed ceramic green sheets were stacked, with the positive and negative electrode patterns alternately arranged. Above and below the stacking direction, 400 μm thick sheets with the same composition as the ceramic green sheet were stacked as cover sheets and thermocompression bonded. The plate-shaped compact thus prepared was cut into individual pieces (chips).

[0075] After cutting, nickel paste was dipped into the two opposing surfaces of the chip, where the internal electrode pattern lead-out portions were exposed, to form terminal electrodes. The resulting chip was debindered by heating it to 800°C at 100°C / h in a reducing atmosphere using a N2-H2-H2O gas mixture. The heating rate was then increased to 6000°C / h, the temperature was raised to 1250°C, held for 1 minute, and then cooled to room temperature. The sintered chip was then reoxidized at 800°C in a dry N2 atmosphere. This resulted in a sample with an external dimension of 1.0mm x 0.5mm x 0.5mm, containing a total of 10 effective dielectrics. The average dielectric thickness per layer after sintering was 3.0μm.

[0076] (Example 1-2) In Example 1-2, the same amount of Dy2O3 was used in place of Ho2O3 as the shell component, and the other conditions were the same as in Example 1-1.

[0077] (Examples 1-3) In Example 1-3, the same amount of Gd2O3 was used in place of Ho2O3 as the shell component, and the other conditions were the same as in Example 1-1.

[0078] (Examples 1-4) In Example 1-4, the same amount of Y2O3 was used in place of Ho2O3 as the shell component, and the other conditions were the same as in Example 1-1.

[0079] (Examples 1-5) In Example 1-5, both Ho2O3 and Dy2O3 were used instead of Ho2O3 as the shell component. The total amount of Ho2O3 and Dy2O3 was the same as when Ho2O3 was used alone in Example 1-1, and the mol% of Ho2O3 and Dy2O3 were the same. Other conditions were the same as in Example 1-1.

[0080] (Examples 1 to 6) In Example 1-6, both Ho2O3 and Gd2O3 were used instead of Ho2O3 as the shell component. The total amount of Ho2O3 and Gd2O3 was the same as when Ho2O3 was used alone in Example 1-1, and the mol% of Ho2O3 and Gd2O3 were the same. Other conditions were the same as in Example 1-1.

[0081] (Comparative Example 1-1) The materials and compounding ratios used for the ceramic green sheets were the same as in Example 1-1, but all raw materials were dispersed together with zirconia beads, a solvent, and a dispersant, and a binder was added to create an organic slurry. The standard heating rate of 300°C / h was also used for firing after binder removal. Other conditions were the same as in Example 1-1.

[0082] (Comparative Example 1-2) In Comparative Example 1-2, the same amount of Tb2O3 was used in place of Ho2O3 as the shell component, and the other conditions were the same as in Example 1-1.

[0083] (Comparative Examples 1-3) In Comparative Example 1-3, the shell component Ho2O3 was replaced with the same amount of Yb2O3, and the other conditions were the same as in Example 1-1.

[0084] Cross sections of the fired samples of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 were analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray spectroscopy (EDX) detector. Figure 12 shows an elemental map of Example 1-1, and Figure 13 shows an elemental map of Comparative Example 1-1. It can be seen that in Example 1-1, the BaTiO particles form a core-shell structure in which a central BaTiO core remains and the outer region is covered with a shell of calcium and holmium. Quantitative EDX analysis of the calcium content in the core and shell revealed that the calcium content in the core was either completely undetectable or extremely low, approaching the detection limit. Meanwhile, the calcium concentration in the shell relative to the titanium in the matrix was 2.0 mol% or higher, confirming a calcium concentration difference of at least 100 times between the core and shell. On the other hand, looking at the element map of Comparative Example 1-1, it can be seen that calcium and holmium segregated as a phase different from BaTiO3, and a core-shell structure could not be formed.

[0085] The capacitance of these samples was measured using an LCR meter under conditions of a DC voltage of 10 V / μm, 1 kHz, and 0.5 Vrms. The dielectric constant of the dielectric layer was calculated from the effective area, number of layers, dielectric thickness, and vacuum permittivity of the internal electrode layers. The dielectric constants of Example 1-1 and Comparative Example 1-1 at an applied voltage of 10 V / μm were 800 and 630, respectively. These results confirmed that Example 1-1 achieved superior bias characteristics compared to Comparative Example 1-1. While the mechanism behind the improvement in bias characteristics due to the calcium-containing shell has not yet been fully identified, it is believed that the calcium-containing shell introduced a distribution in the electric field (coercive field) required for polarization reversal, which changed the voltage dependence of the polarization reversal response to an external voltage (the dielectric constant is the coefficient of this response). Furthermore, the calcium-containing shell contracted the crystal lattice, applying stress to the BaTiO3 core, which may have affected the stability of the ferroelectric domains. Since these two effects are theoretically independent, they likely act simultaneously.

[0086] In Examples 1-2 to 1-6, a shell portion containing calcium was formed as a solid solution, and the dielectric constant was comparable to that of holmium alone. Consequently, Example 1-1, which contained only holmium, exhibited the best characteristics. On the other hand, when the rare earth was replaced with terbium (Comparative Example 1-2) or ytterbium (Comparative Example 1-3), a shell portion containing calcium was not formed as a solid solution, and calcium segregated, as in Comparative Example 1-1, despite being fabricated using the same process as Examples 1-1 to 1-6. The dielectric constant under an applied voltage of 10 V / μm was also worse than that of Comparative Example 1-1. From these results, it is concluded that terbium and ytterbium are unsuitable as shell components.

[0087] Example 2 In Example 2, the starting particle size of BaTiO3 in Example 1-1 was changed from 150 nm to 250 nm. As the grain boundary components, MnCO3 was not used, but three types of SiO2, MgO, and Al2O3 were used. Other conditions were the same as in Example 1-1.

[0088] (Comparative Example 2) In Comparative Example 2, the starting particle size of BaTiO3 in Comparative Example 1-1 was changed from 150 nm to 250 nm. As the grain boundary components, MnCO3 was not used, but three types of SiO2, MgO, and Al2O3 were used. Other conditions were the same as in Comparative Example 1-1.

[0089] The samples of Example 2 and Comparative Example 2 had dielectric constants of 750 and 500 at 10 V / μm, respectively. These results confirmed that Example 2 could increase the dielectric constant under a high electric field even when the BaTiO3 particle size was different. This indicates that the use of the ceramic composition according to the embodiment makes it possible to design multilayer ceramic electronic components with high effective capacitance under high voltage. Figure 14 shows an elemental map obtained by TEM-EDX analysis of Example 2. Here, grain boundary elements were also added in addition to the core-shell elements. Similar to Example 1-1, a core-shell structure with a shell containing calcium and holmium in solid solution was confirmed, despite the different particle sizes. The calcium concentration in the shell was confirmed to be more than 10 times that of the core. Additionally, the formation of grain boundaries with localized magnesium, aluminum, and silicon was confirmed. Thus, by designing the grain boundaries to spread uniformly, the shell components (calcium and rare earth elements) were distributed throughout each particle, resulting in the formation of a macroscopically uniform shell.

[0090] (Comparative Example 3-1) In Comparative Example 3-1, the starting particle size of BaTiO3 in Comparative Example 1-1 was changed from 150 nm to 30 nm, and the other conditions were the same as those in Comparative Example 1-1.

[0091] (Comparative Example 3-2) In Comparative Example 3-2, the starting particle size of BaTiO3 in Example 1-1 was changed from 150 nm to 30 nm, and the other conditions were the same as in Example 1-1.

[0092] In both Comparative Examples 3-1 and 3-2, the BaTiO3 particles grew abnormally during sintering, making them unsuitable for electrical property evaluation (the minimum level of insulation could not be ensured), and therefore the dielectric constant could not be measured. These results demonstrate that it is preferable to set a lower limit on the starting particle size of BaTiO3.

[0093] Comparative Example 4 In Comparative Example 4, the starting particle size of BaTiO3 in Comparative Example 1-1 was changed from 150 nm to 50 nm, and the other conditions were the same as those in Comparative Example 1-1.

[0094] Example 4 In Example 4, the starting particle size of BaTiO3 in Example 1-1 was changed from 150 nm to 50 nm, and the other conditions were the same as in Example 1-1.

[0095] The samples of Example 4 and Comparative Example 4 had a relative dielectric constant at 10 V / μm of 930 and 450, respectively. These results confirmed that Example 4 could increase the relative dielectric constant under a high electric field.

[0096] (Comparative Example 5) In Comparative Example 5, the starting particle size of BaTiO3 in Comparative Example 1-1 was changed from 150 nm to 100 nm, and the other conditions were the same as those in Comparative Example 1-1.

[0097] Example 5 In Example 5, the starting particle size of BaTiO3 in Example 1-1 was changed from 150 nm to 100 nm, and the other conditions were the same as in Example 1-1.

[0098] The samples of Example 5 and Comparative Example 5 had a relative dielectric constant at 10 V / μm of 880 and 480, respectively. These results confirmed that Example 5 could increase the relative dielectric constant under a high electric field.

[0099] (Comparative Example 6) In Comparative Example 6, the starting particle size of BaTiO3 in Comparative Example 1-1 was changed from 150 nm to 400 nm, and the other conditions were the same as those in Comparative Example 1-1.

[0100] Example 6 In Example 6, the starting particle size of BaTiO3 in Example 1-1 was changed from 150 nm to 400 nm, and the other conditions were the same as in Example 1-1.

[0101] The samples of Example 6 and Comparative Example 6 had a relative dielectric constant at 10 V / μm of 700 and 350, respectively. These results confirmed that Example 6 could increase the relative dielectric constant under a high electric field.

[0102] (Comparative Example 7-1) In Comparative Example 7-1, the starting particle size of BaTiO3 in Comparative Example 1-1 was changed from 150 nm to 500 nm, and the other conditions were the same as those in Comparative Example 1-1.

[0103] (Comparative Example 7-2) In Comparative Example 7-2, the starting particle size of BaTiO3 in Example 1-1 was changed from 150 nm to 500 nm, and the other conditions were the same as in Example 1-1.

[0104] In Comparative Examples 7-1 and 7-2, the electrical properties could not be evaluated because the powder was not sufficiently densified even when the firing temperature was increased to 1300°C. These results show that it is preferable to set an upper limit on the starting particle size of BaTiO3.

[0105] The results are shown in Table 1. [Table 1]

[0106] Example 8-1 In Example 8-1, the grain boundary component was one type, SiO2, and the other conditions were the same as in Example 1-1.

[0107] (Example 8-2) In Example 8-2, the grain boundary components were two types, SiO2 and Al2O3, and the other conditions were the same as in Example 1-1.

[0108] (Example 8-3) In Example 8-3, the grain boundary components were two types, SiO2 and MgO, and the other conditions were the same as in Example 1-1.

[0109] (Example 8-4) In Example 8-4, the grain boundary components were two types, SiO2 and MnCO3, and the other conditions were the same as in Example 1-1.

[0110] The average lifespan (h@150°C, 50V / μm) was measured for the samples of Comparative Example 1-1, Example 1-1, and Examples 8-1 to 8-4. The average lifespan was measured as the average time until a short circuit failure occurred under the conditions of 150°C and 50V / μm.

[0111] The results are shown in Table 2. Table 2 also shows the results of Example 1-1 and Comparative Example 1-1. In all of Examples 8-1 to 8-4, a shell portion containing dissolved calcium was formed, and the calcium concentration in the shell portion was 10 times or more that in the core portion. In all of Examples 8-1 to 8-4, the bias characteristics (dielectric constant under a high electric field) were good. The average life was better in Examples 8-2 to 8-4 and Example 1-1 than in Example 8-1. These results showed that it is preferable to use two or more types of grain boundary components. Furthermore, since Example 1-1 was better than Examples 8-2 to 8-4, it was found that it is preferable to use three or more types of grain boundary components. [Table 2]

[0112] (Example 9-1) In Example 9-1, part of the calcium in the shell was replaced with strontium. In the shell, the ratio of strontium to the sum of strontium and calcium (Sr / (Ca+Sr)) was 0.2. Other conditions were the same as in Example 2.

[0113] (Example 9-2) In Example 9-2, part of the calcium in the shell was replaced with strontium. In the shell, the ratio of strontium to the sum of strontium and calcium (Sr / (Ca+Sr)) was 0.4. Other conditions were the same as in Example 2.

[0114] (Example 9-3) In Example 9-3, part of the calcium in the shell was replaced with strontium. In the shell, the ratio of strontium to the sum of strontium and calcium (Sr / (Ca+Sr)) was 0.6. Other conditions were the same as in Example 2.

[0115] (Example 9-4) In Example 9-4, part of the calcium in the shell was replaced with strontium. In the shell, the ratio of strontium to the sum of strontium and calcium (Sr / (Ca+Sr)) was 0.8. Other conditions were the same as in Example 2.

[0116] The results are shown in Table 3. We also investigated whether the capacitance-temperature characteristics satisfied X7T. The results in Table 3 show that the larger the Sr / (Ca+Sr), the higher the relative dielectric constant at 10 V / μm. On the other hand, if Sr / (Ca+Sr) is too large, the EIA standard X7T may not be satisfied, so it is preferable that Sr / (Ca+Sr) is 0.4 or less. [Table 3]

[0117] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0118] 10 Base 11 Dielectric layer 12 Internal electrode layer 13 Cover Layer 14 Capacity part 15 End Margin 16 Side Margin 20a,20b external electrode 30 Crystalline Particles 31 Core 32 Shell part 33 Grain boundaries 34 Grain boundary triple point 35 Sub-crystal particles 51 Ceramic green sheet 52 Internal electrode pattern 53 Dielectric Pattern 54 Cover Sheet 100 Multilayer ceramic capacitors

Claims

1. a dielectric layer containing a plurality of crystal particles whose main component is barium titanate, the layer having a core portion and a shell portion covering the core portion, calcium dissolved in the shell portion, and the calcium concentration in the shell portion being 10 times or more the calcium concentration in the core portion; internal electrodes, each of which is provided with the dielectric layer sandwiched therebetween and which are mainly composed of nickel or copper; and external electrodes electrically connected to the internal electrodes.

2. 2. The multilayer ceramic electronic component according to claim 1, wherein the shell portion contains at least one of gadolinium, dysprosium, holmium, and yttrium.

3. 2. The multilayer ceramic electronic component according to claim 1, wherein silicon and at least one of aluminum, magnesium, and manganese are contained at grain boundaries or grain boundary triple junctions, which are boundaries between the plurality of crystal grains.

4. 2. The multilayer ceramic electronic component according to claim 1, wherein the average grain size of the plurality of crystal grains is 50 nm or more and 400 nm or less.

5. 2. The multilayer ceramic electronic component according to claim 1, wherein the dielectric layers include sub-crystal grains having a structure different from that of the plurality of crystal grains.

6. The multilayer ceramic electronic component according to claim 1 , wherein the shell portion further contains strontium.

7. the shell portion further contains strontium; 2. The multilayer ceramic electronic component according to claim 1, wherein a ratio of strontium to the sum of strontium and calcium in said shell portion is 0.2 or more and 0.4 or less.

8. A dielectric ceramic composition comprising a core portion and a shell portion covering said core portion, said core portion being mainly composed of barium titanate, said core portion being solid-dissolved with calcium, and said shell ...

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