Ceramic electronic component and method for manufacturing the same

Abstract

To provide a ceramic electronic component capable of achieving an enhanced life even when reoxidation treatment is carried out in a strong reduction atmosphere, and a method for manufacturing the ceramic electronic component.SOLUTION: A ceramic electronic component has a laminate structure in which a dielectric layer composed mainly of ceramic having a perovskite structure represented by a general formula ABO3, and an internal electrode layer are alternately laminated one upon another. At least one of crystal particles included in the dielectric layer has a core shell structure. In the core shell structure, a variation in atomic displacement between a B site atom and an oxygen atom in a shell part is larger than a variation in atomic displacement between a B site atom and an oxygen atom in a core part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a ceramic electronic component and a method for manufacturing a ceramic electronic component. [Background technology]

[0002] In recent years, the increasing density of electronic circuits used in digital electronic devices such as mobile phones and tablet devices has led to a growing demand for miniaturized electronic components. This has led to rapid progress in miniaturization and increased capacitance of ceramic electronic components, such as multilayer ceramic capacitors, that make up these circuits. To achieve high capacitance, these electronic components utilize ceramics with a perovskite structure as the dielectric layers, while base metals and other metals are used as the internal electrode layers to reduce costs. Ceramic electronic components with this combination are fired in a reducing atmosphere to simultaneously fire the ceramic and nickel while preventing metal oxidation. However, oxygen vacancies generated in the ceramic after reduction firing have been found to reduce the lifespan of components during high-temperature load tests. To reduce the amount of oxygen vacancies, a reoxidation treatment in a low-temperature, oxidizing atmosphere is required after reduction, which is less likely to oxidize the metal.

[0003] Therefore, in order to provide the dielectric layer with high insulating properties even in a strongly reducing atmosphere, a method has been proposed in which manganese is dissolved in both the core and shell of the core-shell structure (see, for example, Patent Document 1). Also, a method has been proposed in which the life span is improved by reducing the amount of oxygen defects that move across the grain boundaries in the dielectric layer (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-330160 [Patent Document 2] Japanese Patent Publication No. 2020-184587 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to meet the recent demand for smaller size and higher capacity, thinner internal electrode layers and external electrodes are required. With such thin electrode designs, even slight surface oxidation during reoxidation treatment, which was not a problem until now, can increase the resistance of the electrodes and worsen the ESR. Therefore, it is desirable to fire the internal electrode layers and external electrodes in a strongly reducing atmosphere that does not oxidize them. However, firing in a strongly reducing atmosphere creates many oxygen vacancies in the dielectric layer, and these vacancies remain, especially in the core region where the concentration of added elements is low, even after reoxidation treatment, reducing the lifespan.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a ceramic electronic component that can achieve a long life even when subjected to reoxidation treatment in a strongly reducing atmosphere, and a method for manufacturing a ceramic electronic component. [Means for solving the problem]

[0007] The ceramic electronic component according to the present invention has a laminated structure in which dielectric layers composed mainly of a ceramic having a perovskite structure represented by the general formula ABO3 and internal electrode layers are alternately laminated, and at least one of the crystal grains contained in the dielectric layers has a core-shell structure, and in the core-shell structure, the variation in atomic displacement between B-site atoms and oxygen atoms in the shell portion is larger than the variation in atomic displacement between B-site atoms and oxygen atoms in the core portion.

[0008] In the ceramic electronic component, the amount of atomic displacement may be the distance between the position of each B-site atom and the center of gravity of four oxygen atoms nearest to each B-site atom, among atomic coordinates obtained by refining signal intensities in an aberration-corrected annular bright-field scanning transmission electron microscope image by fitting a two-dimensional Gaussian function.

[0009] In the ceramic electronic component, the variation in the atomic displacement between the B site atoms and the oxygen atoms in the shell portion may be 1.3 times or more greater than the variation in the atomic displacement between the B site atoms and the oxygen atoms in the core portion.

[0010] In the ceramic electronic component, the average value of the atomic displacement between the B-site atoms and the oxygen atoms in the shell portion may be 15 pm or more and 30 pm or less.

[0011] In the ceramic electronic component, the average value of the atomic displacement between the B-site atoms and the oxygen atoms in the core portion may be 10 pm or more and 25 pm or less.

[0012] In the ceramic electronic component, the dispersion of the atomic displacements between the B site atoms and the oxygen atoms in the shell portion is 9 pm 2 Over 40pm 2 It may be the following:

[0013] In the ceramic electronic component, the dispersion of the atomic displacements between the B site atoms and the oxygen atoms in the core portion is 5 pm 2 Ends at 4pm 2 It may be the following:

[0014] Another ceramic electronic component according to the present invention has a laminated structure in which dielectric layers composed mainly of a ceramic having a perovskite structure represented by the general formula ABO3 and internal electrode layers are alternately laminated, and at least one of the crystal grains contained in the dielectric layers has a core-shell structure, and in the core-shell structure, the direction of atomic displacement between the B-site atom and the oxygen atom in the shell portion is different from the direction of atomic displacement between the B-site atom and the oxygen atom in the core portion.

[0015] In the ceramic electronic component, the direction of the atomic displacement may be determined by: identifying four oxygen atoms closest to the B-site atom from atomic coordinates obtained by refining signal intensities in an aberration-corrected annular bright-field scanning transmission electron microscope image by fitting a two-dimensional Gaussian function; selecting first to third A-site atoms adjacent to each other in order from the four A-site atoms surrounding the B-site atom; selecting a vector of the line segment connecting the first A-site atom with the second A-site atom and the line segment connecting the second A-site atom with the third A-site atom, which are in a common direction in the core portion and the shell portion; defining the angle between the selected vector and the vector of the line segment connecting the coordinates of the position of the B-site atom with the center of gravity as the direction of individual atomic displacement between the B-site atom and the oxygen atom; and calculating the direction of each individual atomic displacement for all the B-site atoms in the image to obtain an average value.

[0016] In the ceramic electronic component, when the square root of the sum of the squares of the standard deviation of the direction of atomic displacement for each B-site atom in the core portion and the standard deviation of the direction of atomic displacement for each B-site atom in the shell portion is defined as a composite standard deviation, the direction of the atomic displacement in the shell portion may differ from the direction of atomic displacement in the core portion if the difference between the direction of atomic displacement in the core portion and the direction of atomic displacement in the shell portion is at least twice the composite standard deviation.

[0017] In the ceramic electronic component, the difference between the direction of the atomic displacement in the shell portion and the direction of the atomic displacement in the core portion may be 30° or more and 60° or less.

[0018] In the ceramic electronic component, the direction of the atomic displacement in the shell portion may be equal to or greater than 30° and equal to or less than 90°.

[0019] In the ceramic electronic component, the direction of the atomic displacement in the core portion may be equal to or greater than 0° and equal to or less than 30°.

[0020] In the ceramic electronic component, the dielectric layer may have a thickness of 0.2 μm or more and 0.4 μm or less.

[0021] In the ceramic electronic component, the dielectric layer may have an average crystal grain size of 80 nm or more and 200 nm or less.

[0022] In the ceramic electronic component, the internal electrode layers may have a thickness of 0.2 μm or more and 0.8 μm or less.

[0023] The ceramic electronic component may have an outer size of 0201 or larger and 0402 or smaller.

[0024] In the ceramic electronic component, the main component of the dielectric layer may be selected from at least one of barium titanate, strontium titanate, calcium titanate, magnesium titanate, barium strontium titanate, barium calcium titanate, calcium zirconate, barium zirconate, calcium titanate zirconate, and barium calcium titanate zirconate.

[0025] In the ceramic electronic component, the dielectric layer may be mainly composed of barium calcium titanate zirconate.

[0026] In the ceramic electronic component, the laminated structure may have a substantially rectangular parallelepiped shape, the internal electrode layers may be formed so as to be exposed on at least one of two opposing end faces of the substantially rectangular parallelepiped shape, a pair of external electrodes may be formed on the two end faces, and the external electrodes may include base layers formed on the two end faces and containing Cu as a main component, and a plating layer formed on the base layer.

[0027] In the ceramic electronic component, the laminated structure may have a substantially rectangular parallelepiped shape, the internal electrode layers may be formed so as to be exposed on at least one of two opposing end faces of the substantially rectangular parallelepiped shape, a pair of external electrodes may be formed on the two end faces, and the external electrodes may include base layers formed on the two end faces and containing Ni as a main component, and may include plating layers formed on the base layers.

[0028] In the ceramic electronic component, the external electrode may further include a conductive resin layer provided between the base layer and the plating layer.

[0029] A method for producing a ceramic electronic component according to the present invention includes the steps of: obtaining a ceramic laminate by stacking a plurality of lamination units, each having an internal electrode layer pattern, on a dielectric layer green sheet containing a ceramic raw material powder having a perovskite structure represented by the general formula ABO3 and ball-milled in an aqueous acetic acid solution; and firing the ceramic laminate; wherein, in crystal particles having a core-shell structure contained in the dielectric layer after firing, the variation in atomic displacement between B-site atoms and oxygen atoms in the shell portion is made larger than the variation in atomic displacement between B-site atoms and oxygen atoms in the core portion.

[0030] Another method for manufacturing a ceramic electronic component according to the present invention is characterized by comprising the steps of: obtaining a ceramic laminate by stacking a plurality of lamination units, each having an internal electrode layer pattern, on a dielectric layer green sheet containing a ceramic raw material powder having a perovskite structure represented by the general formula ABO3; obtaining a fired body by firing the ceramic laminate; and applying pressure to the fired body and subjecting it to heat treatment, thereby making the direction of atomic displacement between the B-site atom and the oxygen atom in the shell portion different from the direction of atomic displacement between the B-site atom and the oxygen atom in the core portion in crystal particles having a core-shell structure contained in the fired dielectric layer. [Effects of the Invention]

[0031] According to the present invention, it is possible to provide a ceramic electronic component that can achieve a long life even when subjected to reoxidation treatment in a strongly reducing atmosphere, and a method for manufacturing a ceramic electronic component. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 2 is a partial cross-sectional perspective view of a multilayer ceramic capacitor. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Figure 4] 1(a) and 1(b) are cross-sectional views of an external electrode. [Figure 5] FIG. 2(a) is a diagram illustrating an example of a core-shell structure, and FIG. 2(b) is a schematic cross-sectional view of a dielectric layer. [Figure 6] This is a Cs-corrected ABF-STEM image obtained from the shell. [Figure 7] FIG. 10 illustrates the calculation of interatomic displacements. [Figure 8] 1A to 1C are diagrams illustrating a flow of a method for manufacturing a multilayer ceramic capacitor. [Figure 9] FIG. 10 is a diagram illustrating the calculation of the direction of interatomic displacement. [Figure 10] 1A to 1C are diagrams illustrating a flow of a method for manufacturing a multilayer ceramic capacitor. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, embodiments will be described with reference to the drawings.

[0034] (First embodiment) FIG. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 100 in accordance with the first embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a cross-sectional view taken along line BB in FIG. 1. As illustrated in FIGS. 1 to 3, the multilayer ceramic capacitor 100 includes a laminated chip 10 having a substantially rectangular parallelepiped shape and external electrodes 20a, 20b provided on two opposing end faces of the laminated chip 10. Of the four faces of the laminated chip 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 of the laminated chip 10 in the stacking direction. However, the external electrodes 20a, 20b are spaced apart from each other.

[0035] The multilayer chip 10 has a laminated structure 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 on the end face of the multilayer chip 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 material of the cover layers 13 may have the same primary ceramic material as that of the dielectric layers 11.

[0036] The size of the multilayer ceramic capacitor 100 may be, for example, an 0201 shape (length 0.25 mm, width 0.125 mm, height 0.125 mm), an 0402 shape (length 0.4 mm, width 0.2 mm, height 0.2 mm), an 0603 shape (length 0.6 mm, width 0.3 mm, height 0.3 mm), a 1005 shape (length 1.0 mm, width 0.5 mm, height 0.5 mm), a 3216 shape (length 3.2 mm, width 1.6 mm, height 1.6 mm), or a 4532 shape (length 4.5 mm, width 3.2 mm, height 2.5 mm), but is not limited to these sizes. For example, the multilayer ceramic capacitor 100 may have a size larger than the 0201 shape and smaller than the 0402 shape.

[0037] The internal electrode layers 12 are mainly composed of base metals such as Ni (nickel), Cu (copper), and Sn (tin). Precious metals such as Pt (platinum), Pd (palladium), Ag (silver), and Au (gold), or alloys containing these metals, may also be used as the internal electrode layers 12. The thickness of each internal electrode layer 12 is, for example, 0.2 μm to 0.8 μm, 0.8 μm to 1.5 μm, or 1.5 μm to 4.0 μm. The thickness of each internal electrode layer 12 can be measured by mechanically polishing the cross section of the multilayer ceramic capacitor, for example, as shown in FIG. 2, and then averaging the thicknesses at 10 locations on an image taken with a microscope such as a scanning transmission electron microscope.

[0038] The dielectric layer 11 has a main phase made of a ceramic material having a perovskite structure represented by the general formula ABO3. 3-α For example, the ceramic material includes BaTiO3 (barium titanate), CaZrO3 (calcium zirconate), CaTiO3 (calcium titanate), SrTiO3 (strontium titanate), MgTiO3 (magnesium titanate), BaTiO3 (barium titanate) which forms a perovskite structure, 1-x-y Ca x Sr y Ti 1-z Zr zAt least one of the following can be selected and used: O3 (0≦x≦1, 0≦y≦1, 0≦z≦1). 1-x-y Ca x Sr y Ti 1-z Zr z O3 is barium strontium titanate, barium calcium titanate, barium zirconate, calcium titanate zirconate, barium calcium titanate zirconate, etc. The thickness of each dielectric layer 11 is, for example, 0.2 μm to 0.4 μm, or 0.4 μm to 1.0 μm, or 1.0 μm to 10 μm. The thickness of each dielectric layer 11 can be measured by mechanically polishing the cross section of the multilayer ceramic capacitor, for example, as shown in FIG. 2, and then averaging the thicknesses at 10 locations on an image taken with a microscope such as a scanning transmission electron microscope.

[0039] 2, 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 region 14. In other words, the capacitance region 14 is a region where adjacent internal electrode layers 12 connected to different external electrodes face each other.

[0040] 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.

[0041] 3, in the laminated chip 10, the regions extending from the two side surfaces of the laminated chip 10 to the internal electrode layers 12 are referred to as side margins 16. In other words, the side margins 16 are regions provided so as to cover the ends of the multiple internal electrode layers 12 stacked in the above-mentioned laminated structure, which extend to the two side surfaces. The side margins 16 are also regions that do not generate electrical capacitance.

[0042] 4(a) is a cross-sectional view of the external electrode 20b, and is a partial cross-sectional view taken along line AA in FIG. 1. Note that hatching representing the cross section is omitted in FIG. 4(a). As illustrated in FIG. 4(a), the external electrode 20b has a structure in which a first plating layer 22 such as Cu, a conductive resin layer 23, a second plating layer 24 such as Ni, and a third plating layer 25 such as Sn are formed on an underlayer 21. The underlayer 21, the first plating layer 22, the conductive resin layer 23, the second plating layer 24, and the third plating layer 25 extend from both end faces of the laminated chip 10 to the four side faces.

[0043] The base layer 21 is primarily composed of a metal such as Cu, Ni, aluminum (Al), or zinc (Zn), and may also contain a glass component for densifying the base layer 21 or a co-material for controlling the sinterability of the base layer 21. The base layer 21, which contains a large amount of these ceramic components, has good adhesion to the dielectric layer 11 and cover layer 13, which are primarily composed of ceramic materials. The conductive resin layer 23 is a resin layer containing a metal component such as Ag. The conductive resin layer 23 is more flexible than a dense metal layer, allowing it to relieve thermal stress and improve the reliability of the multilayer ceramic capacitor 100. The first plating layer 22 is provided to improve adhesion between the base layer 21 and the conductive resin layer 23. The external electrode 20a also has a laminated structure similar to that of the external electrode 20b.

[0044] 4(b), the first plating layer 22 does not necessarily have to be provided, and the conductive resin layer 23 does not necessarily have to be provided.

[0045] In this embodiment, the perovskite structure represented by the general formula ABO3 that the main component ceramic of the dielectric layer 11 has is an ABO3 that deviates from the stoichiometric composition. 3-α The A site and the B site each represent a crystallographically independent occupied site. For example, in barium titanate, the A site is occupied by barium and the B site is occupied by titanium. At least some of the crystal grains contained in the dielectric layer 11 have a core-shell structure.

[0046] As illustrated in Figure 5(a), the core-shell particle 30 comprises 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.

[0047] Fig. 5(b) is a schematic cross-sectional view of the dielectric layer 11. As illustrated in Fig. 5(b), the dielectric layer 11 includes a plurality of crystal grains 17 of the main component ceramic. At least some of these crystal grains 17 are the core-shell grains 30 described in Fig. 5(a).

[0048] The life of the multilayer ceramic capacitor 100 is believed to be caused by the diffusion and deposition of oxygen vacancies in the ceramic, the main component of the dielectric layer 11. In particular, the core region 31, which has a low concentration of additive elements, is expected to have a high oxygen vacancy concentration after a weak oxidation treatment. Suppressing this oxygen vacancy diffusion from the core region 31 is believed to improve the life of the multilayer ceramic capacitor 100. In this embodiment, the ceramic crystal grains contained in the dielectric layer 11 have a core-shell structure, and the variation in atomic displacement between the B-site atoms and oxygen atoms in the shell region 32 is increased, resulting in the inclusion of areas with large atomic displacement. In areas with large atomic displacement, the movement of oxygen atoms between lattice positions is suppressed, thereby inhibiting the movement of oxygen vacancies. The inhibition of oxygen vacancy diffusion in the shell region 32 suppresses the diffusion of oxygen vacancies from the core region 31 and between the crystal grains covered by the shell region 32. As a result, the life of the multilayer ceramic capacitor 100, which is believed to be due to the diffusion and deposition of oxygen vacancies, is improved. From the above, it is possible to achieve a long life even when reoxidation treatment is carried out in a strongly reducing atmosphere.

[0049] Specifically, the variation in atomic displacement between the B-site atoms and oxygen atoms in the shell portion 32 is made larger than the variation in atomic displacement between the B-site atoms and oxygen atoms in the core portion 31. However, simply increasing the atomic displacement may increase the piezoelectricity of the dielectric material, which may cause acoustic noise. Therefore, in this embodiment, attention is focused on the variation in atomic displacement, and both areas with large atomic displacement and areas with small atomic displacement are included.

[0050] The variation in the atomic displacement between the B-site atom and the oxygen atom can be determined, for example, from the positions of the B-site atom and the oxygen atom in an aberration-corrected annular bright-field transmission scanning electron microscope (Cs-corrected ABF-STEM) image. For example, a multilayer ceramic capacitor 100 is thinned to a thickness of 40 nm or less using an ion milling system, and then the damaged surface layer is removed using a low-acceleration-voltage ion milling system. This thinned sample is then imaged using a Cs-corrected ABF-STEM. To identify the atomic positions, the image is captured with a resolution of 0.01 nm or less per pixel, including at least 200 B-site atoms. For example, when using a JEOL JEM-ARM200F NEOARM with a magnification of 20 M and a resolution of 1024 x 1024, this condition is met (resolution of 0.0083 nm / pixel, including 394 B-site atoms).

[0051] Figure 6 is a Cs-corrected ABF-STEM image actually obtained from the shell portion 32. A-site atoms 41, B-site atoms 42, and oxygen atoms 43 are confirmed.

[0052] To determine the positions of the B-site atoms 42 and oxygen atoms 43 more accurately in the obtained image, the signal intensities in the image are fitted with two-dimensional Gaussian functions for each of the A-site atoms 41, B-site atoms 42, and oxygen atoms 43 in the image, and the signal intensities and atomic positions are refined. Because the intensity of the oxygen atoms 43 is weak and their position is difficult to pinpoint, the following procedure is used for refinement. First, the signal intensity and position of each A-site atom 41 are refined (if there are 100 A-site atoms 41, prepare 100 two-dimensional Gaussian functions and refine the intensity and position for each A-site atom 41 in the image). This results in two-dimensional Gaussian functions for each A-site atom 41, and these intensities are subtracted from the image. This results in an image without the signal intensity of the A-site atoms 41. Next, the signal intensity and position of each B-site atom 42 are refined in the same way and subtracted from the image. Finally, the intensities and positions of the oxygen atoms 43 in the remaining images are refined in the same way to obtain the positions of the oxygen atoms 43. The procedure from imaging to refinement is carried out on a computer, and interatomic displacements are calculated based on the obtained coordinates of each B-site atom 42 and each oxygen atom 43.

[0053] The interatomic displacements can be calculated, for example, using the method illustrated in Figure 7. First, the four oxygen atoms 43 closest to a B-site atom 42 in the image are identified. Next, the center of gravity 44 of these four oxygen atoms 43 is calculated. The coordinates of the position of each B-site atom 42 and the center of gravity of the oxygen atom 43 are calculated, and the difference between the two positions is defined as the atomic displacement 45 between the B-site atom 42 and the oxygen atom 43. This atomic displacement 45 is calculated for all B-site atoms 42 in the image, and the variance is calculated, which can be defined as the variation in the atomic displacement 45 between the B-site atom 42 and the oxygen atom 43. The number of data points used to calculate the variation in atomic displacement 45 needs to be 25 or more, extracted from a single captured image. If it is difficult to distinguish the A-site atoms 41 and B-site atoms 42 in the Cs-corrected ABF-STEM image, they can also be distinguished from aberration-corrected annular dark-field transmission scanning electron microscope images or aberration-corrected transmission scanning electron microscope-EDS element map images acquired simultaneously. The oxygen atom 43 has a clearly lower signal intensity than the A-site atom 41 and the B-site atom 42, and can therefore be easily distinguished.

[0054] For example, the variation in atomic displacement 45 between B-site atom 42 and oxygen atom 43 in shell portion 32 is preferably 1.3 times or more, more preferably 1.5 times or more, and even more preferably 2 times or more, of the variation in atomic displacement 45 between B-site atom 42 and oxygen atom 43 in core portion 31.

[0055] In the image, the average value of atomic displacement 45 between B-site atoms 42 and oxygen atoms 43 in the shell portion 32 is, for example, 15 pm to 20 pm, 20 pm to 25 pm, or 25 pm to 30 pm. The average value of atomic displacement 45 between B-site atoms 42 and oxygen atoms 43 in the core portion 31 is, for example, 10 pm to 15 pm, 15 pm to 20 pm, or 20 pm to 25 pm.

[0056] In this image, the dispersion of the atomic displacement 45 between the B-site atom 42 and the oxygen atom 43 in the shell portion 32 is, for example, 9 pm 2over 15pm 2 Below 3pm 2 over 25pm 2 Below 25pm 2 Over 40pm 2 The dispersion of the atomic displacement 45 between the B-site atoms 42 and the oxygen atoms 43 in the core 31 is, for example, 5 pm 2 Over 8pm 2 Below 8pm 2 More than 12pm 2 Below 12pm 2 Ends at 4pm 2 The following is the result.

[0057] If the average grain size of the crystal grains 17 in the dielectric layer 11 is large, the number of core-shell particles 30 interposed between the two internal electrode layers 12 will decrease, which may result in a decrease in the reliability of the multilayer ceramic capacitor 100. Therefore, it is preferable to set an upper limit on the average grain size of the crystal grains 17. For example, the average grain size of the crystal grains 17 is preferably 200 nm or less, more preferably 180 nm or less, and even more preferably 150 nm or less.

[0058] On the other hand, if the average grain size of the crystal grains 17 in the dielectric layer 11 is small, the dielectric constant of the dielectric may decrease, or a core-shell structure may not be formed, resulting in failure to achieve the desired performance. Therefore, it is preferable to set a lower limit for the average grain size of the crystal grains 17. For example, the average grain size of the crystal grains 17 is preferably 80 nm or more, more preferably 100 nm or more, and even more preferably 120 nm or more. The grain size of the crystal grains can be measured, for example, by mechanically polishing a cross section of a multilayer ceramic capacitor followed by mechanical-chemical polishing, and then obtaining the average long diameter of 20 particles from an image taken with a microscope such as a scanning transmission electron microscope.

[0059] Next, a description will be given of a method for manufacturing the multilayer ceramic capacitor 100. FIG.

[0060] (raw powder production process) First, a dielectric material for forming the dielectric layer 11 is prepared. The A-site elements and B-site elements contained in the dielectric layer 11 are typically contained in the dielectric layer 11 in the form of a sintered compact of ABO3 particles. For example, BaTiO3 is a tetragonal compound with a perovskite structure and exhibits a high dielectric constant. This BaTiO3 can generally be obtained by synthesizing barium titanate by reacting a titanium raw material such as titanium dioxide with a barium raw material such as barium carbonate. Various methods have been known for synthesizing the ceramic that is the main component of the dielectric layer 11, including the solid-phase method, the sol-gel method, and the hydrothermal method. Any of these methods can be used in this embodiment.

[0061] The resulting ceramic raw powder is ball-milled in an acetic acid solution and then washed with pure water. This method fixes dislocations caused by ball milling at high temperatures due to hydrogen and barium vacancies created by the acid, and oxygen atoms displace from the strain around the dislocations. This effect is not achieved by simply stirring the powder in acid or by ball milling in a neutral solution; it is the result of a combination of chemical defects (including interstitial and substitutional dissolved hydrogen atoms) created by the acid and the physical energy of the ball mill. Acetic acid is particularly easy to control because it is a weaker acid than strong acids such as hydrochloric acid, sulfuric acid, and nitric acid. Strong acids not only introduce defects but also dissolve barium titanate. Furthermore, using acetic acid avoids the generation of chlorine, sulfur, and ammonia, which are generated by residues from treatments with hydrochloric, sulfuric, and nitric acid, thereby preventing degradation of the properties of multilayer ceramic capacitors and the deterioration of the electric furnace used during sintering.

[0062] The ceramic raw material powder obtained by acetic acid treatment is then mixed with a specific additive compound depending on the purpose, such as oxides of magnesium (Mg), manganese (Mn), 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)), or oxides or glasses of cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), and silicon (Si).

[0063] For example, a ceramic material is prepared by wet-mixing a ceramic raw material powder with a compound containing an additive compound, followed by drying and pulverization. For example, the ceramic material obtained as described above may be pulverized as necessary to adjust the particle size, or may be combined with a classification process to adjust the particle size. A dielectric material is obtained by the above process.

[0064] (Lamination process) Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the obtained dielectric material and wet mixed. Using the obtained slurry, a dielectric green sheet having a thickness of, for example, 0.5 μm or more is coated on a substrate by, for example, a die coater method or a doctor blade method, and then dried.

[0065] Next, a metal conductive paste containing an organic binder for forming internal electrodes is printed on the surface of the dielectric green sheet by screen printing, gravure printing, or the like to form an internal electrode layer pattern 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 it is preferably the same as the main ceramic component of the dielectric layer 11. For example, BaTiO3 with an average particle diameter of 50 nm or less may be uniformly dispersed.

[0066] Thereafter, the dielectric green sheets on which the internal electrode layer patterns are printed are punched out to a predetermined size, and the punched dielectric green sheets are stacked, with the base material peeled off, by a predetermined number of layers (for example, 100 to 1000 layers) so that the internal electrode layers 12 and the dielectric layers 11 alternate, 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 are alternately drawn out to a pair of external electrodes 20a, 20b of opposite polarity. Cover sheets for forming cover layers 13 are pressure-bonded to the top and bottom of the stacked dielectric green sheets, and the sheets are cut to a predetermined chip size (for example, 1.0 mm x 0.5 mm).

[0067] (Firing process) The ceramic laminate thus obtained was subjected to binder removal treatment in an N2 atmosphere, and then a metal paste that would become the base layer of the external electrodes 20a, 20b was applied by dipping. -12 MPa~10 -9 The mixture is fired in a reducing atmosphere at 1160°C to 1280°C under a pressure of MPa for 5 to 10 minutes.

[0068] (Reoxidation treatment process) In order to return oxygen to the barium titanate, which is the partially reduced main phase of the dielectric layer 11 fired in a reducing atmosphere, heat treatment may be performed in a mixed gas of N2 and water vapor at about 1000°C or in the air at 500°C to 700°C, to a temperature that does not oxidize the internal electrode layer 12. This process is called a reoxidation treatment process.

[0069] (Plating process) Thereafter, a metal coating of Cu, Ni, Sn, or the like is formed on the base layers of the external electrodes 20a, 20b by plating. In the case of the configuration shown in Fig. 4(a), a conductive resin layer 23 is also formed. Through the above steps, the multilayer ceramic capacitor 100 is completed.

[0070] In the manufacturing method according to this embodiment, the processing of the ceramic raw material powder is adjusted so that, after firing, the variation in the amount of atomic displacement between the B-site atoms and oxygen atoms in the shell portion 32 is greater than the variation in the amount of atomic displacement between the B-site atoms and oxygen atoms in the core portion 31. For example, the acetic acid concentration of the acetic acid aqueous solution, the temperature of the acetic acid aqueous solution, the time of the acetic acid treatment, etc. are adjusted. Alternatively, the size of the Zr balls used in ball milling, the time of ball milling, etc. are adjusted.

[0071] (Second embodiment) In the second embodiment, the ceramic crystal grains contained in the dielectric layer 11 have a core-shell structure, and the direction of atomic displacement between the B-site atoms 42 and oxygen atoms 43 in the shell portion 32 is different from the direction of atomic displacement between the B-site atoms 42 and oxygen atoms 43 in the core portion 31. This structure suppresses the diffusion of oxygen vacancies in the core portion 31 into the shell portion 32, thereby inhibiting the movement of oxygen vacancies. The inhibition of oxygen vacancy diffusion in the shell portion 32 suppresses the diffusion of oxygen vacancies from the core portion 31 and the diffusion of oxygen vacancies between the crystal grains covered by the shell portion 32. As a result, the life of the multilayer ceramic capacitor 100, which is believed to be due to the diffusion and accumulation of oxygen vacancies, is improved. From the above, a long life can be achieved even when reoxidation treatment is performed in a strongly reducing atmosphere.

[0072] The direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 can be determined, for example, from the positions of the A-site atom 41, the B-site atom 42, and the oxygen atom 43 in an aberration-corrected annular bright-field transmission scanning electron microscope (Cs-corrected ABF-STEM) image. For example, a multilayer ceramic capacitor 100 is thinned to a thickness of 40 nm or less using an ion milling device, and then the damaged surface layer is removed using a low-acceleration-voltage ion milling device. This thinned sample is then imaged using a Cs-corrected ABF-STEM. To identify the atomic positions, the image is captured with a resolution of 0.01 nm or less per pixel, so that 200 or more B-site atoms 42 are included. For example, when using a JEOL JEM-ARM200F NEOARM, this condition is met when capturing images at a magnification of 20 M and a resolution of 1024 × 1024 (resolution of 0.0083 nm / pixel, including 394 B-site atoms 42).

[0073] To determine the positions of the A-site atoms 41, B-site atoms 42, and oxygen atoms 43 more accurately in the obtained image, the signal intensities in the image are fitted with a two-dimensional Gaussian function for each of the A-site atoms 41, B-site atoms 42, and oxygen atoms 43 in the image, and the signal intensities and atomic positions are refined. Because the intensity of the oxygen atoms 43 is weak and their positions are difficult to pinpoint, the following procedure is used to refine them. First, the signal intensity and position of each A-site atom 41 are refined (if there are 100 A-site atoms 41, prepare 100 two-dimensional Gaussian functions and refine the intensity and position for each A-site atom 41 in the image). This results in two-dimensional Gaussian functions for each A-site atom 41, and these intensities are subtracted from the image. This results in an image without the signal intensity of the A-site atoms 41. Next, the signal intensity and position of each B-site atom 42 are similarly refined and subtracted from the image. Finally, the intensities and positions of the oxygen atoms 43 in the remaining images are refined in the same way to obtain the positions of the oxygen atoms 43. The procedure from imaging to refinement is carried out on a computer, and the directions of the interatomic displacements are calculated based on the obtained coordinates of each B-site atom 42 and each oxygen atom 43.

[0074] The direction of the interatomic displacement can be calculated, for example, by the method illustrated in FIG. 9. First, the four oxygen atoms 43 closest to a certain B-site atom 42 in the image are identified. Next, the center of gravity 44 of these four oxygen atoms 43 is calculated. Next, a vector of a line segment connecting the coordinates of the position of the B-site atom 42 and the center of gravity 44 of the oxygen atom 43 is calculated (hereinafter referred to as a B-O vector 46). Next, a vector that serves as a reference for the direction of this B-O vector 46 is calculated. Of the four A-site atoms 41 surrounding the B-site atom 42, three adjacent ones are selected and designated as A-site atom 41_1 (first A-site atom), A-site atom 41_2 (second A-site atom), and A-site atom 41_3 (third A-site atom). The vector of the line segment connecting the A-site atom 41_1 and the A-site atom 41_2 and the vector of the line segment connecting the A-site atom 41_2 and the A-site atom 41_3 are calculated. One of these two vectors is selected (hereinafter referred to as an A-A vector 47). Although the result will be the same regardless of which vector is selected, a vector in a common direction is selected for the core portion 31 and the shell portion 32. The angle 48 formed by the B-O vector 46 and the A-A vector 47 is calculated, and this is defined as the direction of individual atomic displacement between the B-site atoms 42 and the oxygen atoms 43. The directions of these individual atomic displacements are calculated for all B-site atoms 42 in the image, and the average is calculated and defined as the direction of atomic displacement between the B-site atoms 42 and the oxygen atoms 43. Next, the standard deviation of the atomic displacement directions of each B-site atom 42 is calculated for each of the core portion 31 and the shell portion 32. The square root of the sum of the squares of the standard deviation of the core portion 31 and the standard deviation of the shell portion 32 is defined as the combined standard deviation of the atomic displacement directions. When the difference between the direction of atomic displacement in the core portion 31 and the direction of atomic displacement in the shell portion 32 is equal to or greater than twice the composite standard deviation, it can be defined that the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 in the shell portion 32 is different from the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 in the core portion 31. Note that when it is difficult to distinguish the A-site atom 41 and the B-site atom 42 in the Cs-corrected ABF-STEM image, they may be distinguished from an aberration-corrected annular dark-field transmission scanning electron microscope image or an aberration-corrected transmission scanning electron microscope-EDS element map image acquired at the same time.The oxygen atom 43 has a clearly lower signal intensity than the A-site atom 41 and the B-site atom 42, and can therefore be easily distinguished.

[0075] From the viewpoint of suppressing oxygen vacancy diffusion in the shell portion 32, the difference in the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 in the shell portion 32 and the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 in the core portion 31 in the image is preferably 30° or more, more preferably 40° or more, and even more preferably 44° or more.

[0076] From the viewpoint of dielectric polarization of the material, in the image, the difference between the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 of the shell portion 32 and the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 of the core portion 31 is preferably 60° or less, more preferably 50° or less, and even more preferably 46° or less.

[0077] In the image, the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 of the shell portion 32 is, for example, 30° to 90°, 40° to 80°, or 45° to 60°. In the image, the direction of atomic displacement between the B-site atom 42 and the oxygen atom 43 of the core portion 31 is, for example, 0° to 30°, 10° to 27°, or 15° to 20°.

[0078] If the average grain size of the crystal grains 17 in the dielectric layer 11 is large, the number of core-shell particles 30 interposed between the two internal electrode layers 12 will decrease, which may result in a decrease in the reliability of the multilayer ceramic capacitor 100. Therefore, it is preferable to set an upper limit on the average grain size of the crystal grains 17. For example, the average grain size of the crystal grains 17 is preferably 200 nm or less, more preferably 180 nm or less, and even more preferably 150 nm or less.

[0079] On the other hand, if the average grain size of the crystal grains 17 in the dielectric layer 11 is small, the dielectric constant of the dielectric may decrease, or a core-shell structure may not be formed, resulting in failure to achieve the desired performance. Therefore, it is preferable to set a lower limit for the average grain size of the crystal grains 17. For example, the average grain size of the crystal grains 17 is preferably 80 nm or more, more preferably 100 nm or more, and even more preferably 120 nm or more. The grain size of the crystal grains can be measured, for example, by mechanically polishing a cross section of a multilayer ceramic capacitor followed by mechanical-chemical polishing, and then obtaining the average long diameter of 20 particles from an image taken with a microscope such as a scanning transmission electron microscope.

[0080] The configuration according to this embodiment can be obtained, for example, by performing a pressurized heat treatment between the reoxidation treatment step and the plating treatment step of the manufacturing method described in FIG. 8, as illustrated in FIG. 10. For example, the sintered body is heated to 1000°C in a hot press in the same atmosphere as the reoxidation treatment, then heat-treated under a pressure of 100 MPa for two hours, and then cooled to room temperature and depressurized. This method allows atoms to diffuse at high temperatures, fixing their atomic positions as the temperature drops. The depressurization of the fixed structure created by the pressure causes distortion in the dielectric layer 11. This distortion applies stress to the crystals in the shell portion 32, resulting in a change in the direction of atomic displacement between the B-site atoms 42 and the oxygen atoms 43 in the shell portion 32. Note that the acetic acid treatment described in the first embodiment may be omitted in this embodiment. [Example]

[0081] The multilayer ceramic capacitor according to the first embodiment was fabricated and its characteristics were investigated.

[0082] Example 1 Barium titanate powder, whose surface had been previously lattice-defect induced with an acetic acid solution, was used as the dielectric material. Specifically, the raw powder was ball-milled at 80°C using 3 mm diameter Zr balls with a weight twice the powder weight in an acetic acid solution with a 0.2 mol% acetic acid concentration for 1 hour, followed by three washes with pure water. The temperature in the ball mill was raised using a heat gun and maintained at an appropriate value by monitoring with a non-contact thermometer. This raw powder was mixed with additive powders of BaCO3, Ho2O3, MnCO3, MgO, and SiO2 in a pot mill, and a binder was added to form a paste. This paste was applied to a PET film to form a dielectric green sheet. Dielectric green sheets printed with internal electrode layer patterns, primarily composed of Ni, were stacked and pressed together, followed by application of external electrodes, firing, and heat treatment to produce multilayer ceramic capacitors.

[0083] Example 2 In Example 2, a multilayer ceramic capacitor was produced under the same conditions as in Example 1, except that the acetic acid concentration in the acetic acid aqueous solution was set to 0.1 mol %.

[0084] (Comparative Example 1) In Comparative Example 1, the barium titanate was not treated with an aqueous acetic acid solution, and other conditions were the same as in Example 1 to produce a multilayer ceramic capacitor.

[0085] For the multilayer ceramic capacitors of Examples 1 and 2 and Comparative Example 1, the variation in atomic displacement between B-site atoms and oxygen atoms was measured in the core and shell portions of the core-shell particles contained in the dielectric layers. The variation was determined from the positions of B-site atoms and oxygen atoms in aberration-corrected annular bright-field transmission scanning electron microscope (Cs-corrected ABF-STEM) images. Specifically, the multilayer ceramic capacitor was thinned to a thickness of 40 nm or less using an ion milling device, and then the damaged layer on the surface was removed using a low-accelerating-voltage ion milling device. This thinned sample was then imaged using a Cs-corrected ABF-STEM. To identify the atomic positions, the image was taken with a resolution of 0.01 nm or less per pixel, with at least 200 B-site atoms included. This condition was met by taking images at a magnification of 20M and a resolution of 1024 × 1024 using a JEM-ARM200F NEOARM manufactured by JEOL Ltd. (resolution 0.0083 nm / pix, 394 B-site atoms were included).

[0086] To determine the positions of the B-site and oxygen atoms in the image more accurately, the signal intensities in the image were fitted with two-dimensional Gaussian functions for each of the A-site, B-site, and oxygen atoms, respectively, and the signal intensities and atomic positions were refined. First, the signal intensity and position of each A-site atom were refined. This resulted in two-dimensional Gaussian functions for each A-site atom, and these intensities were subtracted from the image. This resulted in an image without the signal intensity of the A-site atoms. Next, the signal intensity and position of each B-site atom were similarly refined from this image and subtracted from the image. Finally, the intensities and positions of the oxygen atoms in the remaining image were similarly refined to obtain the positions of the oxygen atoms. The entire procedure from imaging to refinement was performed on a computer, and the interatomic displacements were calculated based on the obtained coordinates of each B-site atom and each oxygen atom. The interatomic displacements were calculated using the method shown in Figure 7.

[0087] The lifespans of the multilayer ceramic capacitors of Examples 1 and 2 and Comparative Example 1 were confirmed by a HALT test (Highly Accelerated Limit Test). Specifically, the mean time to failure (MTTF) was measured using 30 multilayer ceramic capacitors under the condition of continuously applying DC 100 V (50 V / μm) in an environment of 150°C. If the mean time to failure was less than 5000 minutes, the multilayer ceramic capacitor was judged to not satisfy the predetermined performance (NG). If the mean time to failure was 5000 minutes or more, the multilayer ceramic capacitor was judged to satisfy the predetermined performance (OK).

[0088] The results are shown in Table 1. As shown in Table 1, in Examples 1 and 2, the HALT test was judged to be OK. This is thought to be because, in the core-shell structure, the variation (dispersion) in the amount of atomic displacement between the B-site atom and the oxygen atom in the shell portion was larger than the variation (dispersion) in the amount of displacement between the B-site atom and the oxygen atom in the core portion. On the other hand, in Comparative Example 1, the HALT test was judged to be NG. This is thought to be because, in the core-shell structure, the variation in the amount of atomic displacement between the B-site atom and the oxygen atom in the shell portion was not larger than the variation in the amount of displacement between the B-site atom and the oxygen atom in the core portion. [Table 1]

[0089] Next, a multilayer ceramic capacitor according to the second embodiment was fabricated and its characteristics were examined.

[0090] Example 3 First, the raw material powder BaTiO3 was mixed with additive powders of BaCO3, Ho2O3, MnCO3, MgO, and SiO2 in a pot mill, and a binder was added to form a paste. This paste was applied to a PET film to form a dielectric green sheet. The dielectric green sheets, printed with an internal electrode layer pattern primarily composed of Ni, were stacked and pressed together, followed by application of external electrodes, firing, and heat treatment to produce a multilayer ceramic capacitor. After re-oxidation, the mixture was heated to 1000°C in a hot press in the same atmosphere as during re-oxidation, and then heat-treated at 100 MPa for two hours. The mixture was then cooled to room temperature and the pressure was released.

[0091] Example 4 In Example 4, we used BaTiO3 raw powder, the surface of which had been previously etched with an acetic acid solution, and hot-pressed. Specifically, the raw powder was ball-milled in an acetic acid solution with a 0.2 mol% acetic acid concentration for one hour using Zr balls with a diameter of 3 mm and a weight twice the powder weight, followed by three washes with pure water. The acetic acid-treated BaTiO3 was mixed with additive powders of BaCO3, Ho2O3, MnCO3, MgO, and SiO2 in a pot mill, and a binder was added to form a paste. This paste was applied to a PET film to form a dielectric green sheet. Dielectric green sheets printed with internal electrode layer patterns, primarily consisting of Ni, were laminated and pressed together, followed by application of external electrodes, firing, and heat treatment to produce multilayer ceramic capacitors. After reoxidation, the mixture was heated to 1000°C in a hot press in the same atmosphere as the reoxidation, and then heat-treated at 100 MPa for two hours. The mixture was then cooled to room temperature and depressurized.

[0092] (Comparative Example 2) In Comparative Example 2, the pressure weight was 0 MPa in the heat treatment after reoxidation, and no pressure was applied. The other conditions were the same as in Example 3.

[0093] The directions of atomic displacement between B-site atoms and oxygen atoms were measured in the core and shell portions of the core-shell particles contained in the dielectric layers of the multilayer ceramic capacitors of Examples 3 and 4 and Comparative Example 2. The positions of the A-site atoms, B-site atoms, and oxygen atoms were measured using the same procedures as in Examples 1 and 2 and Comparative Example 1. The directions of atomic displacement were calculated using the method shown in Figure 9.

[0094] The results are shown in Table 2. In Example 3, the acetic acid treatment was not performed, and therefore the acetic acid concentration was 0 mol%. In Example 3, the direction (average) of atomic displacement between the B-site atom and the oxygen atom in the core portion was 19°, and the direction (average) of atomic displacement between the B-site atom and the oxygen atom in the shell portion was 59°. The standard deviation of the direction of atomic displacement in the core portion was 7°, and the standard deviation of the direction of atomic displacement in the shell portion was 10°. The composite standard deviation × 2 was 24°. The difference between the direction (average) of atomic displacement in the shell portion and the direction (average) of atomic displacement in the core portion was larger than the composite standard deviation × 2. In Example 4, the direction (average) of atomic displacement between the B-site atom and the oxygen atom in the core portion was 26°, and the direction (average) of atomic displacement between the B-site atom and the oxygen atom in the shell portion was 78°. The standard deviation of the direction of atomic displacement in the core portion was 6°, and the standard deviation of the direction of atomic displacement in the shell portion was 5°. The composite standard deviation × 2 was 16°. The difference between the direction of atomic displacement (average value) in the shell portion and the direction of atomic displacement (average value) in the core portion was larger than twice the composite standard deviation. In Comparative Example 2, the direction of atomic displacement (average value) between the B site atoms and oxygen atoms in the core portion was 20°, and the direction of atomic displacement (average value) between the B site and oxygen atoms in the shell portion was 35°. The standard deviation of the direction of atomic displacement in the core portion was 7°, and the standard deviation of the direction of atomic displacement in the shell portion was 5°. The composite standard deviation x 2 was 17°. The difference between the direction of atomic displacement (average value) in the shell portion and the direction of atomic displacement (average value) in the core portion was not larger than twice the composite standard deviation. [Table 2]

[0095] The lifespans of the multilayer ceramic capacitors of Examples 3 and 4 and Comparative Example 2 were confirmed by a HALT test using the same procedures as in Examples 1 and 2 and Comparative Example 1. The results of Examples 3 and 4 and Comparative Example 2 are shown in Table 2. As shown in Table 2, the HALT test was judged to be OK for Examples 3 and 4. This is thought to be because, in the core-shell structure, the difference between the direction (average value) of atomic displacement in the shell portion and the direction (average value) of atomic displacement in the core portion was larger than twice the composite standard deviation. On the other hand, the HALT test was judged to be NG for Comparative Example 2. This is thought to be because, in the core-shell structure, the difference between the direction (average value) of atomic displacement in the shell portion and the direction (average value) of atomic displacement in the core portion was not larger than twice the composite standard deviation.

[0096] 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]

[0097] 10 stacked chips 11 Dielectric layer 12 Internal electrode layer 13 Cover Layer 14 capacity area 15 End Margin 16 Side Margin 17 Crystalline particles 20a,20b external electrode 30 Core-shell particles 31 Core 32 Shell part 41 A-site atoms 42 B-site atoms 43 oxygen atoms 44 Center of gravity 45 Atomic Displacement 46 BO Vector 47 AA Vector 48 angle 100 Multilayer ceramic capacitors

Claims

1. General formula ABO ３ The laminated structure is formed by alternately laminating dielectric layers and internal electrode layers, the dielectric layers being mainly composed of a ceramic having a perovskite structure represented by the formula: At least one of the crystal grains contained in the dielectric layer has a core-shell structure, a core-shell structure in which the variation in atomic displacement between the B-site atoms and the oxygen atoms in the shell portion is greater than the variation in atomic displacement between the B-site atoms and the oxygen atoms in the core portion.

2. 2. The ceramic electronic component according to claim 1, wherein the atomic displacement is a distance between the position of each B-site atom and the center of gravity of four oxygen atoms nearest to each B-site atom, among atomic coordinates refined by fitting a two-dimensional Gaussian function to signal intensities in an aberration-corrected annular bright-field scanning transmission electron microscope image.

3. 3. The ceramic electronic component according to claim 1, wherein a variation in the atomic displacement between the B site atoms and the oxygen atoms in the shell portion is 1.3 times or more larger than a variation in the atomic displacement between the B site atoms and the oxygen atoms in the core portion.

4. 4. The ceramic electronic component according to claim 1, wherein an average value of the atomic displacement between the B-site atoms and the oxygen atoms in the shell portion is 15 pm or more and 30 pm or less.

5. 5. The ceramic electronic component according to claim 1, wherein an average value of atomic displacements between the B-site atoms and the oxygen atoms in the core region is 10 pm or more and 25 pm or less.

6. The dispersion of the atomic displacement between the B site atoms and the oxygen atoms in the shell portion is 9 pm ２ Ends 40pm ２ 6. The ceramic electronic component according to claim 1, wherein:

7. The dispersion of the atomic displacement between the B site atoms and the oxygen atoms in the core portion is 5 pm ２ Ends at 16pm ２ 7. The ceramic electronic component according to claim 1, wherein:

8. General formula ABO ３ The laminated structure is formed by alternately laminating dielectric layers and internal electrode layers, the dielectric layers being mainly composed of a ceramic having a perovskite structure represented by the formula: At least one of the crystal grains contained in the dielectric layer has a core-shell structure, A ceramic electronic component characterized in that, in the core-shell structure, the direction of atomic displacement between the B-site atom and the oxygen atom in the shell portion is different from the direction of atomic displacement between the B-site atom and the oxygen atom in the core portion.

9. 9. The ceramic electronic component according to claim 8, wherein the direction of atomic displacement is determined by: identifying four oxygen atoms closest to the B-site atom from atomic coordinates refined by fitting a two-dimensional Gaussian function to signal intensities in an aberration-corrected annular bright-field scanning transmission electron microscope image; determining a vector of a line segment connecting the center of gravity of the four oxygen atoms to the coordinates of the position of the B-site atom; selecting first to third A-site atoms adjacent to each other from four A-site atoms surrounding the B-site atom; selecting a vector common to the core portion and the shell portion from the vector of the line segment connecting the first A-site atom with the second A-site atom and the vector of the line segment connecting the second A-site atom with the third A-site atom; determining the angle between the selected vector and the vector of the line segment connecting the coordinates of the position of the B-site atom with the center of gravity as the direction of individual atomic displacement between the B-site atom and the oxygen atom; and averaging the directions of the individual atomic displacements for all the B-site atoms in the image.

10. 10. The ceramic electronic component according to claim 9, wherein, when the square root of the sum of the squares of the standard deviation of the direction of atomic displacement for each B-site atom in the core portion and the standard deviation of the direction of atomic displacement for each B-site atom in the shell portion is defined as a composite standard deviation, if the difference between the direction of atomic displacement in the core portion and the direction of atomic displacement in the shell portion is twice or more of the composite standard deviation, the direction of atomic displacement in the shell portion differs from the direction of atomic displacement in the core portion.

11. 11. The ceramic electronic component according to claim 9, wherein a difference between the direction of the atomic displacement in the shell portion and the direction of the atomic displacement in the core portion is 30° or more and 60° or less.

12. 12. The ceramic electronic component according to claim 8, wherein the direction of the atomic displacement in the shell portion is equal to or greater than 30 degrees and equal to or less than 90 degrees.

13. 13. The ceramic electronic component according to claim 8, wherein the direction of the atomic displacement in the core portion is equal to or greater than 0° and equal to or less than 30°.

14. 14. The multilayer ceramic electronic component according to claim 1, wherein the dielectric layers have a thickness of 0.2 μm or more and 0.4 μm or less.

15. 15. The ceramic electronic component according to claim 1, wherein an average value of the crystal grain size of the dielectric layer is 80 nm or more and 200 nm or less.

16. 16. The ceramic electronic component according to claim 1, wherein the internal electrode layers have a thickness of 0.2 μm or more and 0.8 μm or less.

17. 17. The ceramic electronic component according to claim 1, wherein an outer size is equal to or larger than 0201 shape and equal to or smaller than 0402 shape.

18. 18. The ceramic electronic component according to claim 1, wherein a main component of the dielectric layer is selected from at least one of barium titanate, strontium titanate, calcium titanate, magnesium titanate, barium strontium titanate, barium calcium titanate, calcium zirconate, barium zirconate, calcium titanate zirconate, and barium calcium titanate zirconate.

19. 19. The ceramic electronic component according to claim 1, wherein the dielectric layer comprises a main component of barium calcium zirconate titanate.

20. The laminated structure has a substantially rectangular parallelepiped shape, the internal electrode layers are formed so as to be exposed on at least one of two opposing end faces of the substantially rectangular parallelepiped shape, A pair of external electrodes is formed on the two end surfaces, 20. The ceramic electronic component according to claim 1, wherein the external electrodes include a base layer formed on the two end faces and containing Cu as a main component, and a plating layer formed on the base layer.

21. The laminated structure has a substantially rectangular parallelepiped shape, the internal electrode layers are formed so as to be exposed on at least one of two opposing end faces of the substantially rectangular parallelepiped shape, A pair of external electrodes is formed on the two end surfaces, 20. The ceramic electronic component according to claim 1, wherein the external electrodes include a base layer formed on the two end faces and containing Ni as a main component, and a plating layer formed on the base layer.

22. 22. The ceramic electronic component according to claim 20, wherein the external electrodes further comprise a conductive resin layer provided between the underlayer and the plating layer.

23. General formula ABO ３ a step of obtaining a ceramic laminate by laminating a plurality of lamination units, each having an internal electrode layer pattern, on a dielectric layer green sheet containing a ceramic raw material powder ball-milled in an aqueous acetic acid solution, the lamination units having a perovskite structure represented by the formula (I) and firing the ceramic laminate. A method for manufacturing a ceramic electronic component, characterized in that, in crystal particles having a core-shell structure contained in a dielectric layer after firing, the variation in atomic displacement between B-site atoms and oxygen atoms in the shell portion is made larger than the variation in atomic displacement between B-site atoms and oxygen atoms in the core portion.

Images