Dielectric composition and multilayer ceramic electronic component.

Abstract

To provide a dielectric composition with high fracture toughness strength and a multilayer ceramic electronic component containing the dielectric composition.SOLUTION: A dielectric composition according to the present invention includes dielectric particles containing a perovskite compound, and first segregation containing at least Ca, Al, Si, and O.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As shown in Patent Document 1, a multilayer ceramic electronic component having a ceramic layer made of a dielectric composition is known. In this multilayer ceramic electronic component, defects such as cracks and fractures may occur in the green body containing the dielectric composition. Factors causing the defects may include warping of the mounting substrate, difference in linear expansion coefficient between the ceramic layer and the internal electrode layer, or impact and stress applied to the green body from the outside. In particular, when the fracture toughness strength of the dielectric composition is low, the corners of the green body may be chipped or cracks may occur inside the green body during barrel polishing in the manufacturing process.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In view of such circumstances, the present invention has been made, and an object thereof is to provide a dielectric composition having high fracture toughness strength and a multilayer ceramic electronic component including the dielectric composition.

Means for Solving the Problems

[0005] To achieve the above object, the dielectric composition according to the present invention includes: dielectric particles containing a perovskite-type compound, and a first segregation containing at least Ca, Al, Si, and O.

[0006] In the dielectric composition of the present invention, it is considered that the bonding strength between dielectric particles is improved by having a first segregation containing a predetermined element. Further, even if a crack initiation point occurs inside the dielectric composition, it is considered that the progress of the crack can be suppressed by a predetermined first segregation. As a result, the dielectric composition of the present invention has high fracture toughness strength.

[0007] Preferably, the molar ratio (Al / (Al + Si)) in the segregation is 0.60 or more.

[0008] Preferably, the molar ratio of Al to the total of Al and Si in the first segregation (Al / (Al + Si)) is 0.55 or more and 0.75 or less.

[0009] Preferably, the perovskite compound is represented by ABO3, the A site contains Ca or / and Sr, the B site contains Zr or / and Ti, the molar ratio of Ca to 1 mol of the A site is 0.5 or more, the molar ratio of Zr to 1 mol of the B site is 0.8 or more. That is, as the perovskite compound constituting the dielectric particles, calcium zirconate, calcium strontium zirconate, etc. are preferable rather than barium titanate. By using the above perovskite compound as the main component of the dielectric composition, the effect of improving the fracture toughness strength due to the first segregation can be further enhanced.

[0010] Preferably, the molar ratio of Ca to the total of Zr and Ti in the first segregation (Ca / (Zr + Ti)) is 1.50 or more, the molar ratio (Ca / (Zr + Ti)) in the first segregation is higher than the molar ratio (Ca / (Zr + Ti)) in the dielectric particles.

[0011] Preferably, the dielectric composition further has a second segregation, the second segregation contains at least Ca, Si, and O and substantially does not contain Al.

[0012] The ratio of the total of Ca and Sr to the total of Zr and Ti in the second segregation is defined as (Ca + Sr) / (Zr + Ti), and the ratio of Si to the total of Zr and Ti in the second segregation is defined as Si / (Zr + Ti). Preferably, (Ca + Sr) / (Zr + Ti) is 1.15 or more in terms of molar ratio, and Si / (Zr + Ti) is 0.10 or more in terms of molar ratio.

[0013] Preferably, the average particle size of the first segregation is 0.10 μm or more and 2.50 μm or less.

[0014] Preferably, the content of the first segregation is 0.0005 pieces / μm 2 or more and 0.0100 pieces / μm 2 or less in the cross-section of the dielectric composition.

[0015] The multilayer ceramic electronic component including the dielectric composition of the present invention described above exhibits high durability against external stress and impact. That is, in the multilayer ceramic electronic component of the present invention, the occurrence of defects such as cracks and fractures in the body can be sufficiently suppressed.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0017] In the present embodiment, as an example of the ceramic electronic component according to the present invention, the multilayer ceramic capacitor 2 shown in FIG. 1 will be described. The multilayer ceramic capacitor 2 includes an element body 4 and a pair of external electrodes 6 formed on the outer surface of the element body 4.

[0018] The shape of the element body 4 shown in FIG. 1 is usually substantially rectangular parallelepiped, having two end faces 4a facing each other in the X-axis direction, two side faces 4b facing each other in the Y-axis direction, and two side faces 4b facing each other in the Z-axis direction. However, the shape of the element body 4 is not particularly limited and may be, for example, elliptical columnar, columnar, or other prismatic shapes. Also, the outer dimensions of the element body 4 are not particularly limited. For example, the length L0 in the X-axis direction can be 0.4 mm to 5.7 mm, the width W0 in the Y-axis direction can be 0.2 mm to 5.0 mm, and the height T0 in the Z-axis direction can be 0.2 mm to 3.0 mm. In this embodiment, the X-axis, Y-axis, and Z-axis are perpendicular to each other.

[0019] And the element body 4 has a ceramic layer 10 and an internal electrode layer 12 that are substantially parallel to the plane including the X-axis and the Y-axis. Inside the element body 4, the ceramic layer 10 and the internal electrode layer 12 are alternately laminated along the Z-axis direction. Here, "substantially parallel" means that most parts are parallel, but there may be some non-parallel parts, and the ceramic layer 10 and the internal electrode layer 12 may have some irregularities or inclinations.

[0020] The ceramic layer 10 is composed of a dielectric composition described later. And the average thickness (layer thickness) per layer of the ceramic layer 10 is not particularly limited and can be, for example, 100 μm or less, preferably 30 μm or less. Also, the number of laminated layers of the ceramic layer 10 can be determined according to the desired characteristics and is not particularly limited. For example, it can be 20 layers or more, more preferably 50 layers or more.

[0021] On the other hand, the internal electrode layer 12 is laminated between each ceramic layer 10, and the number of laminated layers is determined according to the number of laminated layers of the ceramic layer 10. And the average thickness per layer of the internal electrode layer 12 is not particularly limited and can be, for example, 3.0 μm or less. Note that the average thickness of the ceramic layer 10 and the average thickness of the internal electrode layer 12 can be calculated by observing a cross-section as shown in FIG. 1 using a metal microscope and measuring the thickness of each layer (10, 12) at at least five or more points.

[0022] Further, the internal electrode layers 12 are laminated such that one end portion thereof is alternately exposed to two end faces 4a facing each other in the X-axis direction of the element body 4. And, a pair of external electrodes 6 are respectively formed on one end face 4a of the element body 4 and are electrically connected to the exposed ends of the alternately arranged internal electrode layers 12. By forming the internal electrode layers 12 and the external electrodes 6 in this way, a capacitor circuit is constituted by the external electrodes 6 and the internal electrode layers 12. That is, the ceramic layer 10 existing within the capacitance region is sandwiched between internal electrode layers 12 having different polarities, and a voltage can be applied to the ceramic layer 10.

[0023] The internal electrode layer 12 is made of a conductive material and preferably contains Ni as a main component. Specifically, the conductive material of the internal electrode layer 12 is preferably pure Ni or a Ni-based alloy containing 85 wt% or more of Ni, and the Ni-based alloy may contain one or more elements selected from Mn, Cu, Cr, etc. Further, in addition to the above-mentioned conductive material, the internal electrode layer 12 may contain particles of a perovskite-type compound having the same composition as the main component of the ceramic layer 10 as a co-material. Furthermore, the internal electrode layer 12 may contain a trace amount (for example, about 0.1 mass% or less) of non-metallic components such as S and P, and may contain voids. In the case where a co-material, voids, etc. are contained in the internal electrode layer 12, there may be formed a discontinuous portion where no electrode (conductive material) exists in the internal electrode layer 12.

[0024] The pair of external electrodes 6 can include a fired electrode layer, a resin electrode layer, a plated electrode layer, etc., and may be constituted by a single electrode layer or may be constituted by laminating a plurality of electrode layers. For example, the external electrode 6 can have a three-layer structure of a fired electrode layer - Ni plating layer - Sn plating layer (laminated in the described order). In this case, since the Sn plating layer is located on the outermost surface of the external electrode 6, the solder wettability of the external electrode 6 becomes good.

[0025] Further, as shown in FIG. 1, the external electrode 6 integrally includes an end surface portion formed on the end surface 4a of the element body 4 in the X-axis direction and an extension portion formed at the end in the X-axis direction on the four side surfaces 4b of the element body 4. That is, the pair of external electrodes 6 are each formed so as to wrap around from the end surface 4a of the element body 4 to the side surface 4b and are insulated so as not to contact each other in the X-axis direction.

[0026] Note that the extension portion of the external electrode 6 is not essential, and the external electrode 6 may be composed of only the end surface portion. Alternatively, when the multilayer ceramic capacitor 2 is surface-mounted on a substrate, the extension portion of the external electrode 6 only needs to be formed on at least the side surface 4b facing the mounting surface of the substrate, and does not necessarily need to be formed on the side surface 4b opposite to the mounting surface.

[0027] Next, the dielectric composition of the ceramic layer 10 will be described in detail.

[0028] The dielectric composition of the ceramic layer 10 contains a perovskite-type compound represented by the general formula ABO3 as a main component. Here, the main component of the ceramic layer 10 (the main component of the dielectric composition) means a component that occupies 80 mol% or more in the ceramic layer 10. Examples of the perovskite compound include barium titanate, calcium titanate, strontium titanate, calcium zirconate, strontium zirconate, calcium strontium zirconate, and the like.

[0029] In this embodiment, the perovskite-type compound as the main component preferably satisfies the composition formula (Ca 1-α-β Sr α Ba β ) m (Zr 1-γ-δ Ti γ Hf δ )O3. In the above composition formula, the symbols α, β, γ, δ, and m each represent an element ratio.

[0030] m represents the element ratio of the A site to the B site and can be in the range of 1.0 to 1.1.

[0031] α represents the elemental ratio of Sr occupying the A site, and β represents the elemental ratio of Ba occupying the A site. In this embodiment, it is preferable that the A site is mainly composed of Ca or / and Sr. Specifically, the elemental ratio (1-α-β) of Ca in the A site is preferably 0.5 or more and 1.0 or less, more preferably 0.6 or more and 1.0 or less. α is preferably 0 or more and 0.5 or less, more preferably 0 or more and 0.4 or less. β is preferably 0 or more and 0.2 or less.

[0032] γ represents the elemental ratio of Ti occupying the B site, and δ represents the elemental ratio of Hf occupying the B site. In this embodiment, it is preferable that the B site is mainly composed of Zr. Specifically, the elemental ratio (1-γ-δ) of Zr in the B site is preferably 0.8 or more and 1.0 or less, more preferably 0.9 or more and 1.0 or less. γ is preferably 0 or more and 0.2 or less, more preferably 0 or more and 0.1 or less. Hf is usually an unavoidable impurity, and δ is preferably 0.03 or less.

[0033] Note that the elemental ratio of oxygen (O) in the above composition formula may deviate slightly from the stoichiometric composition.

[0034] In addition to the main components described above, the ceramic layer 10 may contain sub-components. Examples of the sub-components include Mn compounds, Mg compounds, Cr compounds, Ni compounds, rare earth element compounds, Si compounds, Li compounds, B compounds, V compounds, Al compounds, Ca compounds, etc. The type and combination of the sub-components, and their addition amounts are not particularly limited.

[0035] Note that the component composition of the ceramic layer 10 may be analyzed by, for example, inductively coupled plasma optical emission spectrometry (ICP), laser ablation ICP mass spectrometry (LA-ICP-MS), X-ray fluorescence analysis (XRF), energy-dispersive X-ray analysis (EDX), or an electron probe microanalyzer (EPMA) equipped with a wavelength-dispersive X-ray spectrometer (WDS).

[0036] The ceramic layer 10 containing the above components has a microstructure as shown in FIG. 2. The ceramic layer 10 includes dielectric particles 20 as a matrix phase, segregation phases (21, 22) having predetermined characteristics, and grain boundaries 23 located between the dielectric particles 20.

[0037] The dielectric particles 20 are composed of the main component (perovskite-type compound) of the ceramic layer 10 described above. When the ceramic layer 10 contains a sub-component, the sub-component may be dissolved in the dielectric particles 20 in addition to the main component. Further, the dielectric particles 20 may have a core-shell structure by dissolving the sub-component. The average particle diameter of the dielectric particles 20 can be 1 μm or less, and preferably 0.20 μm to 2.00 μm.

[0038] Note that the average particle diameter of the dielectric particles 20 can be measured by observing a cross-section of the ceramic layer 10 as shown in FIG. 2 using a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), etc., and performing image analysis on the obtained cross-sectional photograph. For example, the average particle diameter of the dielectric particles 20 may be calculated by measuring the equivalent circle diameters of at least five or more dielectric particles 20.

[0039] As shown in FIG. 2, the ceramic layer 10 of the present embodiment contains a first segregation 21. The first segregation 21 is a phase of a complex oxide containing at least Ca, Al, Si, and O (oxygen). In addition to the above elements, the first segregation 21 may contain constituent elements of the ceramic layer 10 (elements such as Sr, Ba, Zr, Ti, Hf contained in the main component, sub-component elements, etc.). By having the first segregation 21 containing Ca, Al, Si, and O (oxygen) in the dielectric composition, the fracture toughness strength of the dielectric composition is improved, and the occurrence of defects such as cracks and fractures in the ceramic layer 10 can be suppressed.

[0040] The first segregation 21 can be identified by using a combination of mapping analysis and point analysis with SEM-EDX or SEM-WDS. For example, in the cross-section of the element body 4 as shown in FIG. 2, mapping analysis is performed, and from the Al mapping image and the Si mapping image, the region where Al and Si are segregated overlappingly is identified. Here, the "region where Al and Si are segregated overlappingly" means a region where the Al concentration is higher than that of the dielectric particles 20 and the Si concentration is also high, and it can be visually identified by overlapping the Al and Si mapping images.

[0041] After identifying the "region where Al and Si are segregated overlappingly", point analysis is performed in the identified region to investigate whether Ca is contained in the identified region. Ca is an element constituting the main component of the ceramic layer 10, and in the point analysis of the identified region, it is affected by the dielectric particles 20 existing around the identified region. Therefore, when investigating whether Ca is contained in the identified region by EDX, the molar ratio of Ca to the total of Zr and Ti (Ca / (Zr + Ti)) is measured. Specifically, Ca / (Zr + Ti) in the identified region and Ca / (Zr + Ti) in the dielectric particles 20 are measured and compared. If the Ca / (Zr + Ti) in the identified region is higher than that in the dielectric particles 20, it can be determined that Ca is contained in the identified region, and it can be determined that the identified region is the first segregation 21 in the present embodiment.

[0042] Note that when performing component analysis with higher resolution than SEM using STEM, TEM, etc., there is a possibility of identifying the composition of the segregation phase without being affected by the dielectric particles 20 existing around the segregation phase.

[0043] The first segregation 21 identified by SEM-EDX or the like preferably has a predetermined element ratio. Specifically, in the first segregation 21, the molar ratio of Al to the total of Al and Si (Al / (Al + Si)) is preferably 0.55 or more and 0.75 or less. When the total content of elements excluding oxygen contained in the first segregation 21 is 100 mol, the sum of the contents of Al and Si is at least 20 mol% or more, and preferably 30 mol% or more. Further, Ca / (Zr + Ti) in the first segregation 21 is more preferably 1.50 or more, and even more preferably 2.00 or more. Since Zr and Ti may not be substantially contained in the first segregation 21, the upper limit value of Ca / (Zr + Ti) in the first segregation 21 is not particularly limited.

[0044] When the first segregation 21 satisfies the above-mentioned predetermined element ratio, the fracture toughness strength of the dielectric composition is further improved.

[0045] The detailed composition of the first segregation 21 is not particularly limited, but the crystal system of the first segregation 21 is preferably a tetragonal system. Examples of the tetragonal composite oxide containing Ca, Al, and Si include Ca2Al(AlSiO7). Since the first segregation 21 is a tetragonal composite oxide, the fracture toughness strength of the dielectric composition is further improved.

[0046] The average particle size of the first segregation 21 can be 4.0 μm or less, preferably in the range of 0.10 μm or more and 2.50 μm or less, and more preferably in the range of 0.10 μm or more and 1.0 μm or less. Further, the average particle size of the first segregation 21 is preferably in the range of 0.1 times to 0.9 times the average particle size of the dielectric particles 20. The average particle size of the first segregation 21 may be calculated by measuring the equivalent circle diameter of the identified segregation by image analysis after identifying at least five or more first segregations 21 by EDX or WDS.

[0047] Further, in the present embodiment, the content rate of the first segregation 21 in the dielectric composition (that is, the ceramic layer 10) is defined as the number N1 of the first segregations contained in the unit cross-sectional area of the dielectric composition (unit: pieces / μm2 ) is defined as follows. The number N1 is 0.0004 particles / μm 2 or more, and can be 0.0005 particles / μm 2 or more and 0.0100 particles / μm 2 or less, and preferably within the range of 0.0007 particles / μm 2 or more and 0.0050 particles / μm 2 or less is more preferable. The number N1 is obtained by observing the cross-section of the ceramic layer 10 as shown in Fig. 2 in a plurality of fields by SEM or STEM, and measuring the number of the first segregations 21 present in at least a total cross-section of 1000μm 2 or more.

[0048] When the average particle size and the content rate of the first segregation 21 satisfy the above-mentioned preferred ranges, the fracture toughness strength of the dielectric composition is further improved, and a high relative dielectric constant can be obtained.

[0049] In addition to the first segregation 21, it is preferable that the ceramic layer 10 of the present embodiment has a second segregation 22 having predetermined characteristics. This second segregation 22 is a phase of a complex oxide containing at least Ca, Si, and O (oxygen). Further, unlike the first segregation 21, the second segregation 22 does not substantially contain Al. Specifically, "not substantially containing Al" means that Al / (Al + Si) in the second segregation 22 is 0.10 or less.

[0050] Regarding the second segregation 22 as well, similar to the first segregation 21, it can be specified by using a combination of mapping analysis and point analysis by SEM-EDX or SEM-WDS. In the analysis of the second segregation 22, a "region where Si is segregated" is specified from the mapping image of Si. The region where Si is segregated means a region having a higher Si concentration than the dielectric particles 20, and can be visually specified from the mapping image of Si.

[0051] After identifying the region where Si is segregated, point analysis is performed in the identified region to measure the Al content and Ca / (Zr + Ti). When Al / (Al + Si) in the identified region is 0.10 or less and Ca / (Zr + Ti) in the identified region is higher than that of the dielectric particles 20, it can be determined that the identified region contains Ca and Si and substantially no Al. Therefore, the second segregation 22 contained in the ceramic layer 10 can be identified by the above method.

[0052] Regarding the second segregation 22, component analysis may also be performed using STEM, TEM, etc., which have higher resolution than SEM. In that case, it may be possible to identify the composition of the second segregation 22 without being affected by the dielectric particles 20 present around the second segregation 22.

[0053] The second segregation 22 preferably has a predetermined element ratio. Specifically, the ratio of the total of Ca and Sr to the total of Zr and Ti in the second segregation 22 is defined as (Ca + Sr) / (Zr + Ti), and the ratio of Si to the total of Zr and Ti in the second segregation 22 is defined as Si / (Zr + Ti). The (Ca + Sr) / (Zr + Ti) of the second segregation 22 is preferably 1.15 or more, more preferably 1.39 or more in terms of molar ratio. In addition, the Si / (Zr + Ti) of the second segregation 22 is preferably 0.10 or more, more preferably 0.20 or more in terms of molar ratio. Since Zr and Ti may not be substantially contained in the second segregation 22, the upper limits of both (Ca + Sr) / (Zr + Ti) and Si / (Zr + Ti) are not particularly limited.

[0054] The detailed composition of the second segregation 22 is not particularly limited, but the crystal system of the second segregation 22 is preferably orthorhombic. Examples of orthorhombic composite oxides containing Ca and Si include Ca2SiO4.

[0055] When the second segregation 22 having the above-described predetermined characteristics is contained in the dielectric composition together with the first segregation 21, the fracture toughness strength of the dielectric composition is further improved.

[0056] In addition, the average particle size of the second segregation 22 can be 4.0 μm or less, and is preferably 0.1 μm to 2.5 μm. The average particle size of the second segregation 22 may be measured in the same manner as the average particle size of the first segregation 21. That is, after identifying at least five or more second segregations 22 by the above method, the average particle size may be calculated by measuring the equivalent circle diameter of these second segregations 22 by image analysis.

[0057] Further, the content rate of the second segregation 22 in the dielectric composition (that is, the ceramic layer 10) is defined by the number N2 (unit: pieces / μm 2 ) of the second segregations 22 contained in the unit cross-sectional area of the dielectric composition, and this number N2 may be measured in the same manner as the number N1. In the present embodiment, it is preferable to determine the content rate (number N2) of the second segregation 22 in consideration of the content rate (number N1) of the first segregation 21. Specifically, the ratio (N2 / N1) of N2 to N1 can be within the range of 0.2 to 5.0, and is preferably within the range of 0.5 to 2.0.

[0058] As described above, the ceramic layer 10 (dielectric composition) of the present embodiment contains predetermined segregation phases (21, 22), and the fracture toughness strength of the element body 4 can be improved by the segregation phases. In addition, other segregation phases, voids, etc. may exist in the ceramic layer 10 in addition to the above-described segregation phases (21, 22). Further, the grain boundary 23 existing between the dielectric particles 20 is composed of the constituent elements of the main component and the sub-component elements, and other segregation phases may exist in the grain boundary 23.

[0059] Next, an example of a method for manufacturing the multilayer ceramic capacitor 2 shown in FIG. 1 will be described.

[0060] First, the manufacturing process of the element body 4 will be described. In the manufacturing process of the element body 4, a dielectric paste that becomes the ceramic layer 10 after firing and an internal electrode paste that becomes the internal electrode layer 12 after firing are prepared.

[0061] The dielectric paste is manufactured using the powder of the perovskite-type compound (hereinafter referred to as the main component powder), which is the main component of the dielectric composition, and the powder for the first segregation that becomes the first segregation 21 after firing. The main component powder can be manufactured by a solid-phase method, a hydrothermal synthesis method, a sol-gel method, or the like. For example, in the solid-phase method, starting materials such as CaCO3 powder, SrCO3 powder, ZrO2 powder, and TiO2 powder are uniformly mixed by means such as wet mixing and then calcined to obtain the main component powder. At this time, the calcined main component powder may be appropriately subjected to treatments such as pulverization and classification.

[0062] Regarding the powder for the first segregation, it can be obtained by mixing a compound powder containing Ca (for example, CaCO3 powder), a compound powder containing Al (for example, Al2O3 powder), and a compound powder containing Si (for example, SiO2 powder) at a predetermined ratio and then subjecting them to a calcination treatment. When preparing the powder for the first segregation, it is preferable to appropriately perform a pulverization treatment or the like to control the particle size of the first segregation 21.

[0063] When forming the second segregation 22 in the ceramic layer 10, a powder for the second segregation may be prepared. This powder for the second segregation can also be manufactured, like the powder for the first segregation, by subjecting a compound powder containing Ca and a compound powder containing Si to a calcination treatment. Also, regarding the second segregation 22, there may be cases where it can be formed by the blending ratio of the sub-component raw materials without preparing the powder for the second segregation.

[0064] The dielectric paste is obtained by kneading the above-mentioned main component powder and the powder for the first segregation in addition to an organic vehicle. Here, the organic vehicle is a binder dissolved in an organic solvent. The binder to be used is not particularly limited, and for example, it may be appropriately selected from various binders such as polyvinyl butyral, acrylic, and ethyl cellulose. Also, the organic solvent to be used is not particularly limited, and for example, it may be appropriately selected from various organic solvents such as methyl ethyl ketone, methanol, ethanol, acetone, toluene, terpineol, and butyl carbitol.

[0065] Note that although the above dielectric paste is an organic-based paint, the dielectric paste may also be an aqueous paint obtained by kneading a mixed powder and an aqueous vehicle. In this case, the aqueous vehicle is prepared by dissolving a water-soluble binder, a dispersant, etc. in water. The water-soluble binder to be used is not particularly limited, and for example, polyvinyl alcohol, a water-soluble acrylic resin, a water-soluble polyvinyl butyral resin, etc. can be used. At this time, powders for secondary segregation, sub-component raw materials, etc. are also appropriately added. Further, the dielectric paste may contain additives selected from the above powders for secondary segregation, various dispersants, plasticizers, dielectrics, sub-component compounds, glass frit, etc. as necessary.

[0066] On the other hand, the internal electrode paste may be prepared by kneading a conductive material such as pure Ni powder or Ni alloy powder, or various oxides, organometallic compounds, resinate, etc. that become the above-mentioned Ni or Ni alloy after firing, together with the organic vehicle as described above. At this time, the main component powder contained in the dielectric paste may be added to the internal electrode paste as a co-material. The co-material has the effect of suppressing the sintering of the conductive powder during the firing process.

[0067] Next, a ceramic green sheet is obtained by forming the dielectric paste into a sheet by a method such as the doctor blade method. Then, the internal electrode paste is applied in a predetermined pattern on this ceramic green sheet by various printing methods such as screen printing or a transfer method. Further, after laminating the green sheets with the internal electrode patterns over a plurality of layers, a mother laminate is obtained by pressing in the lamination direction. Note that at this time, the ceramic green sheet and the internal electrode pattern are laminated so that the ceramic green sheet is positioned on the upper and lower surfaces in the lamination direction of the mother laminate.

[0068] The mother laminate obtained by the above process is cut into a predetermined size by dicing or die cutting to obtain a plurality of green chips. The green chips may be solidified and dried, if necessary, to remove a plasticizer or the like, and may be barrel polished using a horizontal centrifugal barrel machine or the like after the solidification and drying. In barrel polishing, the green chips are put into a barrel container together with media and a polishing liquid, and rotational motion, vibration, or the like is applied to the barrel container. By this barrel polishing, unnecessary portions such as burrs generated during cutting are polished, and rounded corners (corner R) are formed at the corners of the green chips. The green chips after barrel polishing are washed with a cleaning liquid such as water and dried. Note that this barrel polishing may be performed after firing of the green chips.

[0069] Next, the green chips obtained above are subjected to a debinding process and a firing process to obtain the element body 4.

[0070] The conditions for the debinding process may be appropriately determined according to the main component composition of the ceramic layer 10 and the main component composition of the internal electrode layer 12, and are not particularly limited. For example, the heating rate is preferably 5 to 300 °C / hour, the holding temperature is preferably 180 to 400 °C, and the temperature holding time is preferably 0.5 to 24 hours. Also, the debinding atmosphere is air or a reducing atmosphere.

[0071] The conditions for the firing process may be appropriately determined according to the main component composition of the ceramic layer 10 and the main component composition of the internal electrode layer 12, and are not particularly limited. For example, the holding temperature during firing is preferably 1200 to 1350 °C, more preferably 1220 to 1300 °C, and the holding time thereof is preferably 0.5 to 8 hours, more preferably 1 to 3 hours. Also, the firing atmosphere is preferably a reducing atmosphere, and as the atmosphere gas, for example, a mixed gas of N2 and H2 humidified can be used. Further, when the internal electrode layer 12 is made of a base metal such as Ni or a Ni alloy, the oxygen partial pressure in the firing atmosphere is preferably 1.0×10 -14 ~1.0×10 -10 MPa.

[0072] After the firing process, annealing may be performed as necessary. Annealing is a process for re-oxidizing the ceramic layer 10, and when the firing process is carried out in a reducing atmosphere, it is preferable to perform annealing. The conditions of the annealing treatment may be appropriately determined according to the main component composition of the ceramic layer 10 and the like, and are not particularly limited. For example, the holding temperature is preferably 950 to 1150 °C, the temperature holding time is preferably 0 to 20 hours, and the heating rate and the cooling rate are preferably 50 to 500 °C / hour. Also, it is preferable to use humidified N2 gas or the like as the atmosphere gas, and the oxygen partial pressure in the annealing atmosphere is 1.0×10 -9 ~1.0×10 -5 MPa.

[0073] In the above debinding treatment, firing treatment, and annealing treatment, in order to humidify N2 gas, mixed gas, etc., for example, a wetter or the like may be used. In this case, the water temperature is preferably about 5 to 75 °C. Also, the debinding treatment, firing treatment, and annealing treatment may be carried out continuously or independently.

[0074] Next, a pair of external electrodes 6 are formed on the outer surface of the element body 4 obtained above. The method of forming the external electrode 6 is not particularly limited. For example, when a fired electrode is formed as the external electrode 6, a conductive paste containing glass frit is applied to the end face of the element body 4 by the dipping method, and then the element body 4 may be heated at a predetermined temperature. Also, when a resin electrode is formed as the external electrode 6, a conductive paste containing a thermosetting resin is applied to the end face of the element body 4, and then the element body 4 may be heated at a temperature at which the thermosetting resin cures. Further, after forming a fired electrode or a resin electrode by the above method, sputtering, vapor deposition, electroplating, or electroless plating may be performed to form an external electrode 6 having a multilayer structure.

[0075] Through the above steps, a multilayer ceramic capacitor 2 having external electrodes 6 is obtained.

[0076] (Summary of Embodiment) The multilayer ceramic capacitor 2 according to this embodiment has an element body 4 in which ceramic layers 10 made of a predetermined dielectric composition and internal electrode layers 12 are alternately laminated. The dielectric composition of the ceramic layer 10 has dielectric particles 20 containing a perovskite-type compound and a first segregation 21 containing at least Ca, Al, Si, and O.

[0077] Since the dielectric composition of the ceramic layer 10 has the above characteristics, the fracture toughness strength is improved. The reason for the improvement in the fracture toughness strength is not necessarily clear, but it is considered to be due to the improvement in the bonding strength between the dielectric particles by the first segregation 21 containing a predetermined element. Also, even if a crack initiation point occurs inside the dielectric composition, it is considered that the progress of the crack can be suppressed by the first segregation 21. In the multilayer ceramic capacitor 2 of this embodiment, since the ceramic layer 10 is made of a dielectric composition having a high fracture toughness strength, the occurrence of defects such as cracks and cracks in the element body 4 can be sufficiently suppressed. Also, the multilayer ceramic capacitor 2 exhibits high durability against external stress and impact.

[0078] In particular, by controlling the element ratios (Al / (Al + Si), Ca / (Zr + Ti)), average particle size, and content rate (number N1) in the first segregation 21 within a predetermined range, the fracture toughness strength of the dielectric composition can be further improved, and a high relative permittivity can be obtained.

[0079] Also, the ceramic layer 10 (dielectric composition) contains a second segregation 22 that contains at least Ca, Si, and O and substantially does not contain Al. By this second segregation 22, the fracture toughness strength of the dielectric composition can be further improved.

[0080] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

[0081] For example, in the present embodiment, the multilayer ceramic capacitor 2 is exemplified as the multilayer ceramic electronic component. However, the multilayer ceramic electronic component of the present invention may be, for example, a bandpass filter, a multilayer three-terminal filter, a thermistor, a varistor, or the like.

[0082] In the present embodiment, the ceramic layer 10 and the internal electrode layer 12 are laminated in the Z-axis direction. However, the lamination direction may be the X-axis direction or the Y-axis direction. In that case, the external electrode 6 may be formed in accordance with the exposed surface of the internal electrode layer 12. Further, the internal electrode layer 12 may be drawn out to the outer surface of the element body 4 via the through-hole electrode. In this case, the through-hole electrode and the external electrode 6 are electrically joined.

Example

[0083] Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

[0084] (Experiment 1) In Experiment 1, capacitor samples according to Examples 1 and 2 and Comparative Examples 1 to 4 were produced by the following procedure.

[0085] Example 1 First, the main component powder, which is a raw material of the dielectric paste, and the first segregation powder were prepared. Specifically, the main component powder was (Ca 0.7 Sr 0.3 )(Zr 0.96 Ti 0.04 )O3 powder produced by the solid-phase method. On the other hand, the first segregation powder was obtained by wet-mixing CaCO3 powder, Al2O3 powder, and SiO2 powder in a predetermined ratio, calcining them, and then pulverizing them with a ball mill.

[0086] Next, a dielectric paste was obtained by kneading the main component powder, the first segregation powder, an organic vehicle, and an auxiliary component powder (MnCO3 powder). Also, a paste for the internal electrode was obtained by kneading Ni powder and an organic vehicle.

[0087] Next, a green chip was manufactured by the sheet method using the above dielectric paste and internal electrode paste. Then, the green chip was subjected to a debinding process, a firing process, and an annealing process to obtain an element body 4 having dimensions of L0×W0×T0 = 3.25 mm×1.75 mm×1.75 mm. Further, in the obtained element body 4, the number of stacked ceramic layers 10 sandwiched between the internal electrode layers 12 was set to 250, the average thickness of the ceramic layer 10 was set to 2.5 μm, and the average thickness of the internal electrode layer 12 was set to 1.1 μm. Through the above steps, a capacitor sample according to Example 1 was obtained.

[0088] Example 2 In Example 2, barium titanate powder (BaTiO3 powder) manufactured by the hydrothermal synthesis method was used as the main component powder added to the dielectric paste. The experimental conditions of Example 2 were the same as those of Example 1 except that the main component of the ceramic layer 10 was changed to BaTiO3, and a capacitor sample according to Example 2 was obtained.

[0089] Comparative Example 1 In Comparative Example 1, a dielectric paste was prepared without using the first segregation powder. That is, the dielectric paste in Comparative Example 1 was prepared by mixing a main component powder composed of (Ca 0.7 Sr 0.3 )(Zr 0.096 Ti 0.04 )O3, a sub-component powder (the same sub-component as in Example 1), and an organic vehicle. The experimental conditions other than the above in Comparative Example 1 were the same as those in Example 1, and a capacitor sample according to Comparative Example 1 was obtained.

[0090] Comparative Example 2 In Comparative Example 2, SiO2 powder was added to the dielectric paste without using the first segregation powder. That is, the dielectric paste in Comparative Example 2 was (Ca 0.7 Sr 0.3 )(Zr 0.96 Ti 0.04)A main component powder composed of O3, SiO2 powder, a sub-component powder (the same sub-components as in Example 1), and an organic vehicle were mixed to prepare it. The experimental conditions other than the above in Comparative Example 2 were the same as those in Example 1, and a capacitor sample according to Comparative Example 2 was obtained.

[0091] Comparative Example 3 In Comparative Example 3, a composite oxide powder obtained by mixing and calcining Al2O3 powder and SiO2 powder without using the first segregation powder was prepared. In Comparative Example 3, this Al-Si-O-based composite oxide powder, (Ca 0.7 Sr 0.3 )(Zr 0.96 Ti 0.04 )O3 main component powder, a sub-component powder (the same sub-components as in Example 1), and an organic vehicle were mixed to prepare a dielectric paste. The experimental conditions other than the above in Comparative Example 3 were the same as those in Example 1, and a capacitor sample according to Comparative Example 3 was obtained.

[0092] Comparative Example 4 In Comparative Example 4, similar to Example 2, barium titanate powder (BaTiO3 powder) produced by the hydrothermal synthesis method was prepared as the main component powder to be added to the dielectric paste. Also, in Comparative Example 4, a composite oxide powder obtained by mixing and calcining Al2O3 powder and SiO2 powder without using the first segregation powder was prepared. The dielectric paste of Comparative Example 4 was prepared by mixing a main component powder composed of BaTiO3, an Al-Si-O-based composite oxide powder, a sub-component powder (the same sub-components as in Example 1), and an organic vehicle. The experimental conditions other than the above in Comparative Example 4 were the same as those in Example 1, and a capacitor sample according to Comparative Example 4 was obtained.

[0093] The following evaluations were performed on the capacitor samples according to each example and each comparative example of Experiment 1.

[0094] Analysis of segregation In Experiment 1, the cross-section of each capacitor sample was observed by SEM, and at that time, mapping analysis and point analysis by EDX were performed to identify the constituent elements of the segregation phase present inside the ceramic layer 10. The measurement results in each example and each comparative example are shown in Table 1.

[0095] Barrel polishing test In Experiment 1, in order to evaluate the fracture toughness strength of the dielectric composition constituting the ceramic layer 10, a barrel polishing test was carried out. Specifically, the fired element body, mullite balls as media, SiC abrasive, and water were put into a barrel tank, and the barrel tank was rotatably arranged on the circumference of a turret board. Then, by rotating the turret board, each barrel tank was rotated in the direction opposite to the revolution of the turret board. That is, the barrel tank was made to perform planetary rotation. At this time, the test was carried out under two conditions: polishing time: 2 hours and polishing time: 8 hours. After drying the element body taken out from the barrel tank, the appearance of the element body was inspected using a stereomicroscope. The number of samples with defects such as cracks and chipping at the corners in the element body was counted.

[0096] The barrel polishing test was carried out for each example and each comparative example, respectively, on 100 samples under the condition of a polishing time of 2 hours and 100 samples under the condition of a polishing time of 8 hours, and the defective occurrence rate was measured. When the defective occurrence rate under the condition of a polishing time of 2 hours was 0%, the fracture toughness strength was judged to be "sufficient (qualified)", and when the defective occurrence rate under the condition of a polishing time of 8 hours was 0%, the fracture toughness strength was judged to be "better". The test results in each example and each comparative example are shown in Table 1.

[0097]

Table 1

[0098] As shown in Table 1, in Example 1 where the first segregation 21 of the Ca-Si-Al-O system exists, the defect occurrence rate in the barrel polishing test could be reduced compared to Comparative Examples 1 to 3. Similarly, in Example 2 where the first segregation 21 of the Ca-Si-Al-O system exists, the defect occurrence rate in the barrel polishing test could be reduced compared to Comparative Example 4. From these results, it was found that by including the first segregation 21 of the Ca-Si-Al-O system in the dielectric composition (ceramic layer), the fracture toughness strength of the dielectric composition can be increased, and defects in the capacitor sample due to external impact can be suppressed.

[0099] Also, as shown in Table 1, the defect occurrence rate under the condition of a polishing time of 8 h was lower in Example 1 than in Example 2. From this result, it was found that by forming the first segregation 21 with respect to the main component of the calcium zirconate system, the fracture toughness strength of the dielectric composition can be further improved.

[0100] Experiment 2 In Experiment 2, capacitor samples of Examples 10 to 16 with different element ratios (Al / (Al + Si) and Ca / (Zr + Ti)) of the first segregation 21 were prepared. The element ratio of the first segregation 21 was controlled by adjusting the mixing ratio of the starting materials (CaCO3 powder, Al2O3 powder, SiO2 powder) during the production of the powder for the first segregation. Also, the element ratios of the first segregation 21 in each of Examples 10 to 16 were measured by SEM-EDX. The experimental conditions other than those described above in Experiment 2 were the same as those in Example 1 of Experiment 1. The evaluation results of Examples 10 to 16 in Experiment 2 are shown in Table 2.

[0101]

Table 2

[0102] From the evaluation results of Examples 10 to 14 shown in Table 2, it was found that the Al / (Al + Si) of the first segregation 21 is preferably in the range of 0.55 or more and 0.75 or less. Also, from the evaluation results of Examples 15 and 16 shown in Table 2, it was found that the Ca / (Zr + Ti) of the first segregation 21 is preferably 1.50 or more.

[0103] Experiment 3 In Experiment 3, capacitor samples of Examples 20 to 24 with different average particle sizes of the first segregation 21 and capacitor samples of Examples 25 to 28 with different contents (number N1) of the first segregation 21 were prepared. The average particle size of the first segregation 21 was controlled by the grinding conditions when grinding the powder for the first segregation with a ball mill. The content of the first segregation 21 was controlled by the mixing ratio of the powder for the first segregation in the dielectric paste. Also, the average particle size and the content of the first segregation 21 were measured by the method shown in the embodiment using SEM-EDX. The experimental conditions other than those described above in Experiment 3 were the same as those in Example 1 of Experiment 1.

[0104] In Experiment 3, a fired electrode layer containing Cu, a Ni plating layer, and a Sn plating layer were formed on the outer surface of the element body in the described order. Then, the relative dielectric constant of the capacitor samples in each example was measured. The relative dielectric constant was calculated by measuring the capacitance using an LCR meter (manufactured by KEYSIGT TECHNOLOGIES: E4981A capacitance meter). Specifically, in the measurement of the capacitance, the measurement temperature was set to 20°C, and a signal with a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms was input to the capacitor sample. Then, the relative dielectric constant (unitless) was calculated based on the thickness of the dielectric layer, the effective electrode area, and the measured capacitance. The above measurements were performed on 10 samples for each example, and the average value was calculated. A relative dielectric constant of 30 or more was judged to be good. The evaluation results of Examples 20 to 28 in Experiment 3 are shown in Table 3.

[0105]

Table 3

[0106] From the evaluation results of Examples 20 to 24 shown in Table 3, it was found that the average particle size of the first segregation 21 is preferably 0.10 μm or more and 2.50 μm or less. Also, from the evaluation results of Examples 25 to 28 shown in Table 3, the content (number N1) of the first segregation 21 is 0.0005 pieces / μm 20.0100 pieces / μm or less 2 It was found that it is preferably the following.

[0107] Experiment 4 In Experiment 4, the second segregation powder obtained by mixing and calcining CaCO3 powder and SiO2 powder was prepared. Then, this second segregation powder was added to the dielectric paste together with the first segregation powder to obtain capacitor samples according to Examples 31 and 32. The experimental conditions other than those described above in Experiment 4 were the same as those in Example 22 of Experiment 3.

[0108] In Experiment 4, the polishing time in the barrel polishing test was extended compared to Experiments 1 to 3, and the test was also carried out under the condition of a polishing time of 16 hours. When the defective rate at a polishing time of 16 hours was 0%, the fracture toughness strength was judged to be "particularly good". The evaluation results of Examples 31 and 32 in Experiment 4 are shown in Table 4. In Table 4, the evaluation results of Example 22 of Experiment 3 without the second segregation 22 are also shown together with the results of Examples 31 and 32 including the second segregation 22.

[0109]

Table 4

[0110] From the evaluation results shown in Table 4, it was found that the fracture toughness strength was further improved by the dielectric composition having a Ca-Si-O-based second segregation 22 that does not contain Al in addition to the first segregation 21. Also, in the second segregation 22, it was found that (Ca + Sr) / (Zr + Ti) is preferably 1.15 or more and (Ca + Sr) / (Zr + Ti) is 0.10 or more. In Examples 31 and 32, Al / (Al + Si) of the second segregation 22 was less than 0.10 in both cases, and Al was not substantially contained in the second segregation 22.

Explanation of symbols

[0111] 2... Multilayer ceramic capacitor 4... Element body 4a... End face 4b … Side 10 … Ceramic layer 12 … Internal electrode layer 20 … Dielectric particles 21 … First segregation 22 … Second segregation 23 … Grain boundary 6 … External electrode

Claims

1. A dielectric composition having dielectric particles containing a perovskite compound and a first segregation containing at least Ca, Al, Si, and O, wherein the perovskite compound is represented by ABO3, the A site contains Ca and / or Sr, and the B site contains Zr and / or Ti, the molar ratio of Ca to 1 mol of the A site is 0.5 or more, and the molar ratio of Zr to 1 mol of the B site is 0.8 or more.

2. The dielectric composition according to claim 1, wherein in the first segregation, the molar ratio of Al to the total of Al and Si (Al / (Al + Si)) is 0.55 or more and 0.75 or less.

3. The dielectric composition according to claim 1 or 2, wherein in the first segregation, the molar ratio of Ca to the total of Zr and Ti (Ca / (Zr + Ti)) is 1.50 or more, and the molar ratio (Ca / (Zr + Ti)) in the first segregation is higher than the molar ratio (Ca / (Zr + Ti)) in the dielectric particles.

4. The dielectric composition according to any one of claims 1 to 3, wherein the dielectric composition further has a second segregation, and the second segregation contains at least Ca, Si, and O and substantially does not contain Al.

5. A dielectric composition having dielectric particles containing a perovskite compound and a first segregation containing at least Ca, Al, Si, and O, wherein the dielectric composition further has a second segregation, and the second segregation contains at least Ca, Si, and O and substantially does not contain Al.

6. In the second segregation, the ratio of the total of Ca and Sr to the total of Zr and Ti is defined as (Ca + Sr) / (Zr + Ti), and the ratio of Si to the total of Zr and Ti in the second segregation is defined as Si / (Zr + Ti), and the dielectric composition according to claim 4 or 5, wherein (Ca + Sr) / (Zr + Ti) is 1.15 or more in terms of molar ratio and Si / (Zr + Ti) is 0.10 or more in terms of molar ratio.

7. The dielectric composition according to any one of claims 1 to 6, wherein the average particle diameter of the first segregation is 0.10 μm or more and 2.50 μm or less.

8.

9. The content of the first segregation is 0.0005 pieces / μm 2 or more and 0.0100 pieces / μm 2 or less, and the dielectric composition according to any one of claims 1 to 7. A multilayer ceramic electronic component containing the dielectric composition according to any one of claims 1 to 8. ​

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