Multilayer ceramic electronic component and method of manufacturing the same

Abstract

To improve lifetime characteristics of a dielectric layer.SOLUTION: A multilayer ceramic electronic component comprises an element assembly formed by alternately laminating an internal electrode layer and a dielectric layer. The dielectric layer contains core shell grains each including a core part, a first shell layer which is provided around the core part, and a second shell layer which is provided around the first shell layer. A grain boundary is provided between the adjacent core shell grains. A concentration of donor elements in the first shell layer and a concentration of donor elements in the second shell layer are higher than a concentration of donor elements in the core part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Recently, progress has been made in miniaturizing and increasing the capacitance of multilayer ceramic electronic components such as multilayer ceramic capacitors. To meet this demand, there is a trend toward increasing the dielectric constant of materials forming dielectric layers. Furthermore, there is a trend toward thinner dielectric layers and an increasing number of laminated dielectric layers. Such dielectric layers are also required to be reliable. It has been known that a method of previously dissolving specific elements in raw material powder is effective, and a technology for adding donor elements has been proposed with the aim of improving life characteristics (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-139720 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, as the thickness of the dielectric layer has become smaller and the number of layers has increased, further improvements in life characteristics are being demanded.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to improve the life characteristics of a dielectric layer. [Means for solving the problem]

[0006] In order to achieve the above object, the multilayer ceramic electronic component can have an element body formed by alternately stacking internal electrode layers and dielectric layers, the dielectric layer including core-shell particles each having a core portion, a first shell layer provided around the core portion, and a second shell layer provided around the first shell layer, with grain boundaries between adjacent core-shell particles, and the concentration of the donor element in the first shell layer and the concentration of the donor element in the second shell layer each being higher than the concentration of the donor element in the core portion.

[0007] In the multilayer ceramic electronic component having the above configuration, the concentration of the donor element in the second shell layer may be higher than the concentration of the donor element in the first shell layer.

[0008] In the monolithic ceramic electronic component having the above configuration, the concentration of the donor element in the second shell layer may be in the range of 0.1 at % to 3.0 at % when BaTiO3 is taken as 100 at %.

[0009] In the monolithic ceramic electronic component having the above configuration, the concentration of the donor element in the first shell layer may be in the range of 0.01 at % to 0.5 at % when BaTiO3 is taken as 100 at %.

[0010] In the multilayer ceramic electronic component having the above configuration, the donor element contained in the second shell layer may be at least one of a V element and an Mo element.

[0011] In the multilayer ceramic electronic component having the above configuration, the grain boundaries may contain Mn elements.

[0012] Furthermore, in the monolithic ceramic electronic component having the above configuration, the concentration of the Mn element at the grain boundaries can be in the range of 0.1 at % to 3.0 at % when BaTiO3 is taken as 100 at %.

[0013] In the multilayer ceramic electronic component having the above configuration, the core-shell particles may be present in an amount of 0.01 at % or more and 99 at % or less in the dielectric layers.

[0014] In the multilayer ceramic electronic component having the above configuration, the thickness of the second shell layer may be greater than 0 nm and equal to or less than 12 nm.

[0015] Furthermore, in the multilayer ceramic electronic component having the above configuration, the first shell layer may contain a rare earth element and Mg element.

[0016] In order to achieve the above object, a method for manufacturing a multilayer ceramic electronic component can include the steps of: preparing a raw material powder containing core-shell particles each having a core portion, a first shell layer provided around the core portion, and a second shell layer provided around the first shell layer; preparing an element body having a substantially rectangular parallelepiped shape in which first internal electrode layers and second internal electrode layers are alternately stacked with a dielectric layer containing the raw material powder sandwiched therebetween; and firing the element body.

[0017] In the method for manufacturing a multilayer ceramic electronic component having the above configuration, the step of preparing the raw material powder can include a primary synthesis in which BaTiO particles are coated with a rare earth element and Mg element and then fired; a secondary synthesis in which the particles prepared by the primary synthesis are coated with a donor element and then fired; and a tertiary synthesis in which Mn element is added to the particles prepared by the secondary synthesis.

[0018] Furthermore, the method for producing a monolithic ceramic electronic component having the above-described configuration can be embodied as including a step of coating the particles produced by the secondary synthesis with Yb element.

[0019] In the method for producing a monolithic ceramic electronic component having the above configuration, at least one of Si element and BN element may be added in the step of preparing the raw material powder.

[0020] In the method for producing a monolithic ceramic electronic component having the above-described configuration, at least one of Si element and BN element may be added together with the Mn element in the tertiary synthesis.

[0021] In the method for manufacturing a monolithic ceramic electronic component having the above configuration, when the Si element is added, the amount of the Si element added can be 0.5 at % or more and 3.0 at % or less when BaTiO3 is taken as 100 at %.

[0022] In the method for manufacturing a monolithic ceramic electronic component having the above configuration, when the BN element is added, the amount of the BN element added can be 0.1 at % or more and 2.0 at % or less when BaTiO3 is taken as 100 at %.

[0023] In the method for manufacturing a multilayer ceramic electronic component having the above configuration, the raw material powder may be configured to have a perovskite structure mainly composed of a ceramic material having a perovskite structure represented by the general formula ABO3, containing at least Ba at the A site, and having an A / B ratio of 1.03 or more or 0.97 or less. 3-α (0≦α≦1: α represents the amount of deviation from the stoichiometric composition).

[0024] In the method for manufacturing a monolithic ceramic electronic component having the above-described configuration, the step of firing the element body can be performed by pressure firing.

[0025] In the method for producing a monolithic ceramic electronic component having the above configuration, the pressure firing may be carried out at a temperature of 1150°C or higher and 1400°C or lower.

[0026] In the method for producing a monolithic ceramic electronic component having the above configuration, the pressurized firing may be carried out at a pressure of 1 MPa or more and 7 MPa or less. [Effects of the Invention]

[0027] According to the present invention, the life characteristics of the dielectric layer can be improved. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view of a multilayer ceramic capacitor according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor taken along line AA′ in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor taken along line BB' in FIG. [Figure 4] FIG. 4(A) is a schematic cross-sectional view of a dielectric layer, and FIG. 4(B) is a diagram showing a schematic view of particles forming the dielectric layer in the embodiment. [Figure 5] FIG. 5 is a diagram showing a schematic view of part C in FIG. 4(B). [Figure 6] 6 is a flowchart showing an example of a method for manufacturing a multilayer ceramic capacitor according to an embodiment, and is a diagram schematically showing the state of one particle forming a dielectric layer. [Figure 7] FIG. 7 is a flowchart showing an example of a synthesis step included in the raw material powder preparation step. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of the process from primary synthesis to obtaining a ceramic sheet. [Figure 9] FIG. 9 is a graph showing the relationship between the Mn concentration at the grain boundary and the life. [Figure 10] FIG. 10 is a graph showing the relationship between the V concentration in the second shell layer and the lifetime. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings show X-axis, Y-axis, and Z-axis that are orthogonal to each other as appropriate. The X-axis, Y-axis, and Z-axis are common to all the drawings. The X-axis direction corresponds to the third direction, the Y-axis direction corresponds to the second direction, and the Z-axis direction corresponds to the first direction.

[0030] [Overall Configuration of Multilayer Ceramic Capacitor 10] 1 to 3 are diagrams showing an example of a multilayer ceramic capacitor 10 according to a first embodiment of the present invention. Fig. 1 is a perspective view of the multilayer ceramic capacitor 10. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line AA' in Fig. 1. Fig. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line BB' in Fig. 1.

[0031] The multilayer ceramic capacitor 10 includes a ceramic element body 11 having a substantially rectangular parallelepiped shape. Of the six faces of the ceramic element body 11, opposing main faces are referred to as the upper and lower faces, and the remaining four faces are referred to as side faces. Generally, the main faces have the largest area. A first external electrode 14a and a second external electrode 14b are provided on the surface of the ceramic element body 11, spaced apart from each other. In the example shown in FIGS. 1 to 3, the first external electrode 14a and the second external electrode 14b are provided on two opposing side faces (a first side face and a second side face), respectively. The first external electrode 14a extends from the first side face to four adjacent faces. The second external electrode 14b extends from the second side face to four adjacent faces. However, the first external electrode 14a and the second external electrode 14b are spaced apart from each other.

[0032] As long as the first external electrode 14a and the second external electrode 14b are spaced apart, they can be provided at any position on the surface of the ceramic body 11. For example, the first external electrode 14a and the second external electrode 14b may be provided spaced apart on the same surface of the ceramic body 11, or the first external electrode 14a and the second external electrode 14b may be provided spaced apart on two adjacent surfaces or two opposing surfaces of the ceramic body 11.

[0033] As long as the first external electrode 14a and the second external electrode 14b are spaced apart from each other, they may extend from the surface of the ceramic body 11 on which they are provided to any other surface. For example, they may extend to an adjacent surface, or may extend further from the surface on which they are provided.

[0034] The multilayer ceramic component has a first direction, which is the stacking direction; a second direction perpendicular to the stacking direction and where two opposing surfaces intersect; and a third direction perpendicular to the first direction and perpendicular to the second direction and where two opposing surfaces intersect. The first, second, and third directions are orthogonal to each other. The stacking direction can be set in any of the length, width, and height directions of the ceramic body 11.

[0035] 1 to 3, the stacking direction, i.e., the first direction, is the Z-axis direction, which is the height direction of the ceramic body 11 and the direction in which the internal electrode layers face each other. In FIGS. 1 to 3, the second direction perpendicular to the stacking direction is the X-axis direction, which is the length direction of the ceramic body 11, the direction in which the first side surface and the second side surface of the ceramic body 11 face each other, and the direction in which the first external electrode 14a and the second external electrode 14b face each other. In FIGS. 1 to 3, the third direction perpendicular to the stacking direction (first direction) and the second direction is the Y-axis direction, which is the width direction of the internal electrode layers and the direction in which two side surfaces (third and fourth side surfaces) of the four side surfaces of the ceramic body 11 other than the first and second side surfaces face each other. The X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to one another.

[0036] The ceramic body 11 has a configuration in which dielectric layers 15 containing a ceramic material that functions as a dielectric and internal electrode layers are alternately stacked. The internal electrode layers include a plurality of first internal electrode layers 12 and a plurality of second internal electrode layers 13. The first internal electrode layers 12 and the second internal electrode layers 13 are alternately stacked. Edges of the first internal electrode layers 12 are extended to the surface of the ceramic body 11 on which the first external electrode 14a is provided. Edges of the second internal electrode layers 13 are extended to the surface of the ceramic body 11 on which the second external electrode 14b is provided. Note that it is sufficient that the first internal electrode layers 12 and the second internal electrode layers 13 are exposed in different regions on the surface of the laminate and are electrically connected to different external electrodes. The different regions on the surface of the laminate may be respective surface regions on opposing surfaces of the laminate, respective surface regions on adjacent surfaces of the laminate, or different surface regions on the same surface of the laminate. As long as the different external electrodes are spaced apart, the first internal electrode layers 12 and the second internal electrode layers 13 may extend from the surfaces exposed in the surface region of the laminate to other surfaces. In the example of Figures 1 to 3, the edge of the first internal electrode layer 12 is drawn to the first side surface of the ceramic body 11 on which the first external electrode 14a is provided. The edge of the second internal electrode layer 13 is drawn to the second side surface of the ceramic body 11 on which the second external electrode 14b is provided.

[0037] As a result, the first internal electrode layer 12 is electrically connected to the first external electrode 14a, and the second internal electrode layer 13 is electrically connected to the second external electrode 14b. As a result, the multilayer ceramic capacitor 10 has a configuration in which capacitor units are stacked, i.e., a capacitance forming portion 16. In addition, in a laminate of dielectric layers 15 and internal electrode layers, the internal electrode layers are arranged as the outermost layers in the stacking direction, and the upper and lower surfaces of the laminate are covered with a cover portion 18. The cover portion 18 is mainly composed of a ceramic material.

[0038] The size of the multilayer ceramic capacitor 10 may be, 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. The size of the multilayer ceramic capacitor 10 may be, for example, length > width ≥ height, width > length ≥ height, height > length ≥ width, or height > width ≥ length.

[0039] The ceramic body 11 has a capacitance forming portion 16 which is a laminate of a dielectric layer 15, a first internal electrode layer 12 and a second internal electrode layer 13, and a protective portion 17. The protective portion 17 forms the periphery of the ceramic body 11 and has two end faces facing the X-axis direction, two side faces facing the Y-axis direction, and two main faces facing the Z-axis direction. The side faces and main faces form multiple peripheral surfaces. The end faces, side faces, and main faces are, for example, substantially flat, but may also be rounded.

[0040] The protective portion 17 includes a cover portion 18, a side margin portion 19, and an end margin portion 20. The cover portion 18 is located outside the capacitance forming portion 16 in the stacking direction, i.e., outside the capacitance forming portion 16 in the Z-axis direction in the example of FIGS. 1 to 3. The side margin portion 19 is provided outside the capacitance forming portion 16 in a direction perpendicular to the stacking direction. The side margin portion 19 is provided as a region that does not include the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are extended to the surface of the ceramic body 11 in the direction perpendicular to the stacking direction. That is, in the example of FIGS. 1 to 3, the side margin portion 19 is located outside the capacitance forming portion 16 in the Y-axis direction. The end margin portion 20 is provided outside the capacitance forming portion 16 in the direction perpendicular to the stacking direction. The end margin portions 20 are provided as regions including the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are drawn out to the surface of the ceramic body 11 in a direction perpendicular to the stacking direction. That is, the end margin portions 20 are located outside the capacitance forming portions 16 in the X-axis direction in the example of FIGS.

[0041] The side margins 19 are regions consisting only of the dielectric layers. The end margins 20 are regions including the dielectric layers and the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are drawn to the surface of the ceramic body 11.

[0042] The capacitance forming portion 16 is disposed inside the protective portion 17 and constitutes a functional portion. The capacitance forming portion 16 is formed by laminating a plurality of first internal electrode layers 12 and a plurality of second internal electrode layers 13 with dielectric layers 15 (see FIG. 2) interposed therebetween. In the example of FIGS. 1 to 3, they are laminated in the Z-axis direction. The internal electrode layers 12, 13 are both sheet-shaped extending along a plane perpendicular to the lamination direction, and are alternately arranged in the lamination direction. In the example of FIGS. 1 to 3, they are sheet-shaped extending along the XY plane, and are alternately arranged along the Z-axis direction. The configuration of the dielectric layers 15 will be described in detail later.

[0043] The first internal electrode layers 12 and the second internal electrode layers 13 are mainly composed of base metals such as nickel (Ni), copper (Cu), tin (Sn), etc., or alloys containing these. Noble metals such as platinum (Pt), palladium (Pd), silver (Ag), gold (Au), etc., or alloys containing these may also be used as the main component of the first internal electrode layers 12 and the second internal electrode layers 13. The main component of the first internal electrode layers 12 and the second internal electrode layers 13 may be the same or different.

[0044] The dielectric layer 15 has a main phase of a ceramic material having a perovskite structure represented by the general formula ABO3, for example. The A / B ratio is 1.03 or more or 0.97 or less. The perovskite structure has an ABO that deviates from the stoichiometric composition. 3-α (0≦α≦1: α represents the amount that deviates from the stoichiometric composition; hereinafter, α will be omitted.) For example, the ceramic material in question is barium titanate (BaTiO3), calcium zirconate (CaZrO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), magnesium titanate (MgTiO3), BaTiO3, which forms a perovskite structure, 1-x-y Ca x Sr y Ti 1-z Zr z At 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 zO3 includes barium strontium titanate, barium calcium titanate, barium zirconate, barium titanate zirconate, calcium titanate zirconate, and barium calcium titanate zirconate. For example, the dielectric layer 15 contains 50 at% or more of the main component ceramic, e.g., 90 at% or more. The thickness of the dielectric layer 15 is, for example, 5.0 μm or less, 3.0 μm or less, 1.0 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or 0.2 μm or less. The thickness of the dielectric layer 15 can be measured by observing the cross section of the multilayer ceramic capacitor 10 with a scanning electron microscope (SEM), measuring the thickness at 10 points for each of 10 different dielectric layers 15, and deriving the average value of all the measurement points. The dielectric ceramics listed here are the main components of the dielectric layer 15.

[0045] The dielectric layer 15 may contain an additive. Examples of additives to the dielectric layer 15 include oxides of zirconium (Zr), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (scandium (Sc), cerium (Ce), neodymium (Nd), yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)), or oxides containing cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), or silicon (Si), or glasses containing cobalt, nickel, lithium, boron, BN (boron nitride), sodium, potassium, or silicon.

[0046] The protective portion 17 is also made of dielectric ceramics. In terms of suppressing internal stress, it is preferable that the cover portion 18 and the end margin portion 20 of the protective portion 17 have the same main component composition as the dielectric layer 15. This also improves manufacturing efficiency.

[0047] The external electrodes 14a, 14b each have a base film 21 formed to cover the lead portions of the internal electrode layers 12, 13 and part of the surface of the ceramic body, and a plating film 22 formed on the base film 21. The base film 21 is formed, for example, by firing a conductive paste or by sputtering. The plating film 22 is formed by electrolytic plating. Each film of the external electrodes 14a, 14b is formed of a metal or alloy containing, for example, nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or aluminum (Al) as a main component. Alternatively, the external electrodes 14a, 14b can be formed by printing and drying a conductive paste containing a curable resin, such as Ag, and a conductive metal.

[0048] [Detailed configuration of dielectric layer 15] Fig. 4(A) is a schematic cross-sectional view of the dielectric layer 15, and Fig. 4(B) is a diagram schematically illustrating the state of particles 151 forming the dielectric layer 15 in this embodiment. Fig. 5 is a diagram schematically illustrating the state of part C in Fig. 4. As illustrated in Fig. 4(A), the dielectric layer 15 comprises a plurality of crystal particles 150 of a main component ceramic. At least some of these crystal particles 150 are core-shell particles 151 described in Fig. 4(B).

[0049] Each core-shell particle 151 includes a core portion 151a located at the center of the particle, a first shell layer 151b provided around the core portion 151a, and a second shell layer 151c provided around the first shell layer 151b. Grain boundaries 152 are formed between adjacent core-shell particles 151. The core-shell particles 151 need only be contained at least within the dielectric layer 15. In other words, the abundance ratio of the core-shell particles 151 in the dielectric layer 15 may be from 0.01 at % to 99% but is preferably from 20 at % to 99% at %.

[0050] The core portion 151a contains a dielectric ceramic that is the main component of the dielectric layer 15.

[0051] First shell layer 151b contains Ho (holnium) as a rare earth element and Mg. The effect of first shell layer 151b containing Ho and Mg will now be briefly described, along with an outline of the mechanism.

[0052] Ho is a +3 valent element, and becomes a donor when it substitutes into the Ba (+2 valent) site of BaTiO3 as shown in formula 1. The electrons generated in the reaction shown in formula 1 move in the direction of reducing oxide ion defects in formula 2, which is the reaction formula for oxide ion defects, that is, to the left in formula 2.

number

number

[0053] It is believed that oxide ion defects are a cause of shortening the life of the multilayer ceramic capacitor 10. For this reason, it is believed that adding Ho element reduces oxide ion defects, and as a result, it is possible to suppress shortening of the life of the multilayer ceramic capacitor 10.

[0054] Mg is a +2 valent element and dissolves in the Ti site (+4 valent) of the BaTiO3 perovskite structure, becoming an acceptor. This reaction occurs before the reaction involving the Ho element. The dissolution of the Mg element distorts the lattice of BaTiO3, facilitating the dissolution of the Ho element. Focusing on this point, in this embodiment, Mg element is added to facilitate the dissolution of the Ho element. Furthermore, when Ho (+3 valent) dissolves in the Ba (+2 valent) site, the charge difference is -1, whereas Mg (+2 valent) dissolves in the Ti (+4 valent) site, resulting in a charge difference of +2. Therefore, it is believed that adding the Mg element and dissolving it also has the effect of charge compensation.

[0055] In addition, other rare earth elements that can be used besides the Ho element include Y (yttrium), Ce (cerium), Nd (neodymium), La (lanthanum), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), and Dy (dysprosium).

[0056] The second shell layer 151c contains a V element. The second shell layer 151c may contain a Mo element instead of the V element. The V element and the Mo element are examples of donor elements. A donor element is an element that functions as a donor at the B site. The V element and the Mo element tend to segregate near the grain boundary 152, and tend to form the second shell layer 151c. It is believed that the V element and the Mo element function to reduce oxygen ion defects near the grain boundary 152. When the V element is used as the donor element, electrons are generated as shown in the following equation 3. The generated electrons cause the reaction shown in the following equation 4 to proceed to the left side.

number

number

[0057] The V element can take on various valences, but can basically function as a donor element by dissolving in the Ti site, generating mobile electrons as shown in the above equation (3). The mobile electrons can reduce oxide-ion defects by moving the oxide-ion defect generation formula shown in the above equation (4) to the left. As mentioned above, oxide-ion defects are thought to be a cause of reduced lifespan of the multilayer ceramic capacitor 10. Therefore, adding the V element, which can function as a donor element, is thought to reduce oxide-ion defects, and as a result, to suppress a reduction in lifespan of the multilayer ceramic capacitor 10.

[0058] Here, the concentration of the donor element in the second shell layer 151c can be set to 0.1 at % or more and 3.0 at % or less when BaTiO3 is taken as 100 at %. The concentration of the donor element is the concentration relative to the main component ceramic, that is, the concentration relative to BaTiO3.

[0059] The donor element may be contained in the first shell layer 151b. In this case, the concentration of the donor element in the first shell layer 151b can be 0.01 at% or more and 0.5 at% or less, where BaTiO3 is taken as 100 at%. In this case, the concentration of the donor element is also the concentration relative to the main component ceramic, i.e., the concentration relative to BaTiO3.

[0060] As described above, in the multilayer ceramic capacitor 10 of this embodiment, the concentration of the donor element in the second shell layer 151c is higher than the concentration of the donor element in the first shell layer 151b. Moreover, the concentrations of the donor element in the first shell layer 151b and the second shell layer 151c are higher than the concentration of the donor element in the core portion 151a.

[0061] The grain boundary 152 contains Mn elements. Since the grain boundary 152 contains Mn elements, positive (+) charges are likely to be formed near the grain boundary 152, as if a Schottky barrier were formed between the grain boundary 152 and the second shell layer 151c. Oxygen ion defects are repelled by such grain boundaries 152. As a result, the oxygen ion defects cannot cross the grain boundaries 152, and migration between adjacent core-shell particles 151 is suppressed. This improves the reliability of the dielectric layer 15.

[0062] Referring to FIG. 4, the thickness of the first shell layer 151b is t[151b]. The thickness t[151b] can be set appropriately within a range of 1 nm or more and 100 nm or less. The thickness of the second shell layer 151c is t[151c]. The thickness t[151c] can be set appropriately within a range greater than 0 nm and equal to or less than 12 nm. Furthermore, the thickness of the grain boundary 152 is t

[0152] . The thickness t

[0152] can be set within a range of 0.1 nm or more and 5 nm or less.

[0063] The concentration of V as a donor element in the second shell layer 151c can be 0.01% or more and 0.5% or less. Here, the V concentration is expressed in at% with respect to barium titanate (BaTiO3) forming the core portion. Note that when Mo is used instead of V, the concentration of Mo can be 0.01% or more and 0.5% or less.

[0064] The concentration of Mn element in the grain boundary 152 can be set to 0.05 at% or more and 3.0 at% or less, preferably 0.1% or more and 3.0 at% or less, when BaTiO3 is taken as 100 at%. The concentration of Mn element is expressed in at% relative to barium titanate (BaTiO3) forming the core portion 151a.

[0065] The core-shell particle 151 can be observed by mapping the element to be measured using, for example, a transmission electron microscope-energy dispersive X-ray spectroscopy (TEM-EDS). The thickness of each layer included in the core-shell particle 151 may be measured using a cross-sectional image taken by a scanning electron microscope (SEM).

[0066] Based on the TEM-EDS measurement results, it is possible to measure the thickness t[151b] of the first shell layer 151b, the thickness t[151c] of the second shell layer 151c, and the thickness t

[0152] of the grain boundary 152. In addition, based on the TEM-EDS measurement results, it is possible to measure the concentrations of V, Mo, and Mn elements.

[0067] [Method of manufacturing the multilayer ceramic capacitor 10] Next, a description will be given of a method for manufacturing the multilayer ceramic capacitor 10. Fig. 6 is a diagram illustrating a flow of the method for manufacturing the multilayer ceramic capacitor 10. The raw material powder preparation process in step S01 includes primary synthesis (step S11), secondary synthesis (step S12), and tertiary synthesis (step S13) shown in Fig. 7.

[0068] (Step S01: Raw material powder preparation process) A dielectric material for forming the dielectric layer 15 is prepared. This dielectric material is prepared prior to fabrication of the ceramic multilayer chip C. The A-site elements and B-site elements contained in the dielectric layer 15 are typically contained in the dielectric layer 15 in the form of a sintered compact of ABO3 particles. For example, barium titanate is a tetragonal compound with a perovskite structure and exhibits a high relative dielectric constant. This barium titanate 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 15, including the solid-phase method, the sol-gel method, and the hydrothermal method. Any of these methods can be used in this embodiment.

[0069] The resulting ceramic raw material powder is then mixed with a predetermined additive compound depending on the intended purpose, such as oxides of zirconium (Zr), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (scandium (Sc), cerium (Ce), neodymium (Nd), 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.

[0070] For example, a ceramic material is prepared by wet-mixing a compound containing an additive compound with a ceramic raw material powder, 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. The dielectric material is obtained through the above steps. The obtained dielectric material mainly forms the core portion 151a.

[0071] <Step S11: Primary synthesis> The obtained dielectric material is coated with at least Mg (magnesium) and Ho (holmium), a rare earth element, and then fired (see FIG. 8(a)). This results in a first intermediate particle in which a layer containing Ho and Mg elements in BaTiO3 as the main component and forming the first shell layer 151b is formed around the BaTiO3 that forms the core portion 151a. Here, firing is performed under atmospheric pressure, in an environment of 900 to 1000°C for 1 to 4 hours. The coating can be performed by, for example, a coprecipitation method, but is not limited to this, and any conventionally known method can be used as appropriate.

[0072] <Step S12: Secondary Synthesis> The first intermediate particles obtained by the primary synthesis are coated with V element as a donor element and then fired (see (b) in FIG. 8). This results in second intermediate particles in which a layer containing V element in BaTiO3 and forming the second shell layer 151c is formed around the first intermediate particles obtained by the primary synthesis. Mo element may be used for coating instead of V element. Here, firing is performed under atmospheric pressure, in an environment of 900 to 1000°C for 1 to 4 hours. Note that coating can be performed by, for example, coprecipitation, but is not limited to this and any conventionally known method can be used as appropriate.

[0073] <Step S13: Third-order synthesis> At least Mn element, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the second intermediate particles obtained by secondary synthesis, and the mixture is wet-mixed to obtain a slurry (see (c) in FIG. 8). In this example, Mn element is added as a Mn compound. When obtaining the slurry, in addition to these, predetermined additive compounds are added depending on the purpose. Examples of additive compounds include oxides of Nb (niobium), Ta (tantalum), W (tungsten), Cr (chromium), rare earth elements (Y (yttrium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), and Tm (thulium), as well as Co (cobalt), Ni, Li (lithium), B (boron), Na (sodium), and K (potassium). In addition, in the tertiary synthesis, elements selected from Ba, Ti, Zr, etc., which are the component elements that make up the main components of dielectric materials, can also be added as appropriate.

[0074] After the secondary synthesis, the periphery of the first intermediate may be coated with, for example, Yb (ytterbium) elements. By coating with Yb elements, it is possible to prevent the second shell layer 151c and the grain boundary 152 from intermixing in the firing step (step S3) described later. Instead of Yb elements, Er (erbium) elements may be coated.

[0075] Alternatively, Si and BN (boron nitride) may be added at, for example, 2 at% or more to lower the sintering temperature in the sintering step (step S3). The addition of Si and BN can be performed at the same time as the tertiary synthesis, i.e., at the same time as the addition of the Mn compound, as shown in FIG. 8 (c). Lowering the sintering temperature suppresses element diffusion and prevents the first shell layer 151b, the second shell layer 151c, and the grain boundary 152 from intermingling. This phenomenon is believed to be due to a decrease in the diffusion coefficient caused by a decrease in the sintering temperature, but a detailed description thereof will be omitted. It is sufficient to add at least one of Si and BN. This is because the sintering temperature can be lowered whether both Si and BN are added or whether either one is added alone. When Si is added, the amount of Si added can be 0.5 at% or more and 3.0 at% or less. When BN element is added, the amount of BN element added can be 0.1 at % or more and 2.0 at % or less.

[0076] (Step S02: Lamination process) Next, the dielectric material obtained in the tertiary synthesis is wet-mixed with a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer. The resulting slurry is used to coat a dielectric green sheet (ceramic sheet) on a substrate using, for example, a die coater or doctor blade method, and then dried (see (d) in Figure 8).

[0077] 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 arrange a pattern for the internal electrode layer. Ceramic particles may or may not be added to the metal conductive paste as a co-material. When ceramic particles are added as a co-material, the main component of the ceramic particles is not particularly limited, but is preferably the same as the main component ceramic of the dielectric layer 15.

[0078] After peeling the dielectric green sheets from the substrate, the dielectric green sheets are alternately stacked so that the internal electrode layers 12, 13 and the dielectric layers 15 alternate, and so that the edges of the internal electrode layers 12, 13 are alternately exposed at both longitudinal end faces of the dielectric layer 15 and alternately drawn out to pairs of external electrodes 14a, 14b with opposite polarities. For example, the total number of layers is 100 to 500. A ceramic laminate is then obtained by pressure-bonding multiple cover sheets, which become the cover portion 18, to the top and bottom of the laminate of the stacked dielectric green sheets. The obtained ceramic laminate is then cut to a predetermined chip size (for example, a chip size taking into account shrinkage due to firing when the dimensions of the multilayer ceramic capacitor 10 are 0.6 mm × 0.3 mm × 0.3 mm).

[0079] (Step S03: Firing process) In step S03, the green ceramic body obtained in step S02 is fired to produce the ceramic body 11 of the multilayer ceramic capacitor 10 shown in FIG. 1. The firing temperature in step S03 can be determined based on the sintering temperature of the green ceramic body. Firing can be performed by a conventionally known method, for example, in a reducing atmosphere or a low-oxygen partial pressure atmosphere. For example, firing can be performed in a reducing atmosphere or a low-oxygen partial pressure atmosphere. -5 ~10 -8 The mixture can be fired in a reducing atmosphere at 1100 to 1300°C for 10 minutes to 2 hours.

[0080] In this embodiment, pressure firing can be used. Specifically, the firing in this embodiment is performed at 1150°C to 1400°C and 1 MPa to 7 MPa. Pressurization during firing is expected to suppress grain growth of BaTiO3 particles and to suppress mixing of elements between the first shell layer 151b, the second shell layer 151c, and the grain boundary 152. Note that in the firing process, for example, the molded body obtained as described above is subjected to a binder removal treatment in an N2 atmosphere, and then a metal paste that will serve as a base for the external electrodes 14a, 14b is applied by a dipping method, and the molded body is fired in an N2 atmosphere under an oxygen partial pressure of 10 -5 ~10 -8Alternatively, the mixture may be fired in a reducing atmosphere at 1100 to 1300° C. atm for 10 minutes to 2 hours.

[0081] (Step S04: Reoxidation treatment process) Thereafter, a re-oxidation treatment may be performed at 600°C to 1000°C in an N2 gas atmosphere.

[0082] (Step S05: External electrode formation process) Thereafter, the base film 21 is formed. The base film 21 is formed by applying unfired electrode material to the end faces 11a, side faces 11b, and main faces 11c. The application method is, for example, a dipping method, but other conventionally known methods such as printing and sputtering, or a combination of these, may also be used. Next, the unfired electrode material is baked. The baking can be performed, for example, in a reducing atmosphere or a low oxygen partial pressure atmosphere. After the base film 21 is formed, electroplating is performed by immersing the substrate in a plating solution that forms the plating film 22. This forms the plating film 22, and the external electrodes 14a, 14b.

[0083] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0084] In this manner, the multilayer ceramic capacitor 10 shown in FIGS. 1 to 3 is manufactured.

[0085] The multilayer ceramic capacitor 10 of this embodiment includes a dielectric layer 15. The dielectric layer 15 includes a core-shell particle 151, which includes a core portion 151a, a first shell layer 151b provided around the core portion 151a, and a second shell layer 151c provided around the first shell layer 151b. The dielectric layer 15 also includes a grain boundary 152 between adjacent core-shell particles 151. This can improve the life characteristics of the dielectric layer 15.

[0086] In the multilayer ceramic capacitor 10, the second shell layer 151c contains V or Mo, which serves as a donor element, and thus the life characteristics of the dielectric layer 15 can be improved effectively.

[0087] In the multilayer ceramic capacitor 10, the grain boundaries 152 contain Mn elements, so that the life characteristics of the dielectric layers 15 can be effectively improved.

[0088] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. [Example]

[0089] Next, the results of HALT (Highly Accelerated Life Test) tests on examples will be described. The examples correspond to the multilayer ceramic capacitor 10 of the embodiment and have the following dimensions. The thickness of each layer was measured using cross-sectional images taken by SEM.

[0090] The test conditions for the HALT test are shown below. HALT tests were conducted to confirm the effect of adding Mn element and to confirm the effect of adding V element. The test conditions for each are shown below. Test conditions: HALT test for Mn element Furnace temperature 125℃ Current voltage 50 V / μm HALT testing for V elements Furnace temperature 125℃ Current voltage 30 V / μm Lifespan judgment: The time (minutes: median) until the current value exceeds the threshold is defined as the lifespan. Test object dimensions: 0603 (length x width x height = 0.6 mm x 0.3 mm x 0.3 mm)

[0091] 9 shows the relationship between the concentration of Mn element and the life (min) of the multilayer ceramic capacitor of the example. It was confirmed that the higher the concentration of Mn element in the grain boundary 152, the longer the life of the multilayer ceramic capacitor.

[0092] 10 shows the relationship between the concentration of V element and the life (min) of the multilayer ceramic capacitor of the example. It was confirmed that the higher the concentration of V element in the second shell layer 151c, the longer the life of the multilayer ceramic capacitor.

[0093] In the above embodiment, the multilayer ceramic capacitor 10 has been described as an example of a multilayer ceramic electronic component, but the present invention is applicable to all multilayer ceramic electronic components in which dielectric layers and internal electrodes are stacked. Examples of such multilayer ceramic electronic components include chip varistors, chip thermistors, and multilayer inductors. [Explanation of symbols]

[0094] 10...Multilayer ceramic capacitor 11...Ceramic body 12,13…Internal electrode 14a,14b...External electrode 21...Base film 22...Plating film 150…particles 151...core-shell particles 151a...Core section 151b...First shell layer 151c...Second shell layer 152...Grain boundary

Claims

1. The element body is formed by alternately laminating internal electrode layers and dielectric layers, the dielectric layer includes a core-shell particle having a core portion, a first shell layer provided around the core portion, and a second shell layer provided around the first shell layer; having grain boundaries between adjacent core-shell particles; a concentration of the donor element in the first shell layer and a concentration of the donor element in the second shell layer are each higher than a concentration of the donor element in the core portion; Multilayer ceramic electronic components.

2. the concentration of the donor element in the second shell layer is higher than the concentration of the donor element in the first shell layer; The multilayer ceramic electronic component according to claim 1 .

3. The concentration of the donor element in the second shell layer is BaTiO ３ is 100 at%, it is 0.1 at% or more and 3.0 at% or less, The multilayer ceramic electronic component according to claim 1 .

4. The concentration of the donor element in the first shell layer is BaTiO ３ is 100 at%, it is 0.01 at% or more and 0.5 at% or less, The multilayer ceramic electronic component according to claim 1 .

5. the donor element contained in the second shell layer is at least one of a V element and a Mo element; The multilayer ceramic electronic component according to claim 1 .

6. The grain boundaries contain Mn elements. The multilayer ceramic electronic component according to claim 1 .

7. The concentration of the Mn element at the grain boundary is BaTiO ３ is 100 at%, it is 0.05 at% or more and 3.0 at% or less, The multilayer ceramic electronic component according to claim 6.

8. the core-shell particles have an abundance ratio in the dielectric layer of 0.01 at% or more and 99 at% or less; The multilayer ceramic electronic component according to claim 1 .

9. The thickness of the second shell layer is greater than 0 nm and less than 12 nm. The multilayer ceramic electronic component according to claim 1 .

10. the first shell layer contains a rare earth element and an Mg element; The multilayer ceramic electronic component according to claim 1 .

11. a step of preparing a raw material powder including core-shell particles each having a core portion, a first shell layer provided around the core portion, and a second shell layer provided around the first shell layer; a step of producing an element body having a substantially rectangular parallelepiped shape in which first internal electrode layers and second internal electrode layers are alternately stacked with dielectric layers containing the raw material powder sandwiched therebetween; firing the element body; A method for manufacturing a multilayer ceramic electronic component comprising:

12. The step of preparing the raw material powder is ３ a primary synthesis in which particles are coated with rare earth elements and Mg elements and then calcined; a secondary synthesis in which the particles produced by the primary synthesis are coated with a donor element and then sintered; a tertiary synthesis in which Mn element is added to the particles produced by the secondary synthesis; The method for producing a multilayer ceramic electronic component according to claim 11, comprising:

13. coating the particles produced by the secondary synthesis with Yb element; The method for producing a multilayer ceramic electronic component according to claim 12.

14. In the step of preparing the raw material powder, at least one of Si element and BN element is added. The method for producing a multilayer ceramic electronic component according to claim 11.

15. At least one of Si element and BN element is added together with the Mn element in the tertiary synthesis. The method for producing a multilayer ceramic electronic component according to claim 12.

16. When the Si element is added, the amount of the Si element added is BaTiO ３ is 100 at%, it is 0.5 at% or more and 3.0 at% or less, The method for manufacturing a multilayer ceramic electronic component according to claim 14 or 15.

17. When the BN element is added, the amount of the BN element added is BaTiO ３ is 100 at%, it is 0.1 at% or more and 2.0 at% or less, The method for manufacturing a multilayer ceramic electronic component according to claim 14 or 15.

18. The raw material powder has the general formula ABO ３ The ceramic material has a perovskite structure represented by the formula (1), which is a perovskite structure containing at least Ba at the A site, and has an A / B ratio of 1.03 or more or 0.97 or less. The method for producing a multilayer ceramic electronic component according to claim 11.

19. The step of firing the element body is pressure firing. The method for producing a multilayer ceramic electronic component according to claim 11.

20. The pressure firing is carried out at 1150°C or higher and 1400°C or lower. The method for producing a multilayer ceramic electronic component according to claim 19.

21. The pressure firing is carried out at 1 MPa or more and 7 MPa or less. The method for producing a multilayer ceramic electronic component according to claim 19.

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