Electronic component

Abstract

To provide an electronic component comprising a dielectric layer in which a dielectric composition, which hardly causes structural defects such as cracks even when exposed to severe environments, is formed in layers.SOLUTION: There is provided an electronic component comprising a dielectric layer in which a dielectric composition is formed in layers and an electrode layer comprising a base metal as a main component, wherein the dielectric composition comprises, as a main component, a composite oxide represented by the general formula, AaBbC4O15+α, in which A represents a group of elements including at least barium, B represents a group of elements including at least zirconium, C represents a group of elements including at least niobium, a is 3.05 or more and b is 1.01 or more, and the dielectric composition has a main phase composed of a composite oxide, a first phase different from the main phase and containing barium, zirconium, silicon and oxygen and a second phase different from the main phase and the first phase and containing barium, silicon and oxygen.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electronic component having a dielectric layer formed of a dielectric composition in a layered form. [Background technology]

[0002] The electronic circuits or power supply circuits incorporated in electronic devices are equipped with a large number of electronic components, such as multilayer capacitors, that utilize the dielectric properties exhibited by dielectrics. Barium titanate-based dielectric compositions are widely used as the materials that make up the dielectrics of such electronic components (dielectric materials).

[0003] However, in recent years, the applications of electronic components have expanded, and there is a demand for them to function satisfactorily even in high-voltage environments. However, in such environments, the dielectric properties of barium titanate-based dielectric compositions deteriorate, making them unable to adequately cope with such environments. Therefore, there is a demand for dielectric compositions that can exhibit high dielectric properties even in such applications.

[0004] Patent Document 1 discloses a dielectric composition other than a barium titanate-based dielectric composition, which is represented by the general formula Ba6Ti2Nb8O 30 The present application discloses a dielectric composition in which Ba, Ti and Nb in a ferroelectric material represented by the formula (I) are partially substituted with other elements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-274607 Summary of the Invention [Problem to be solved by the invention]

[0006] However, dielectric compositions having a structure similar to that of the ferroelectric material described in Patent Document 1 have the problem that they are prone to structural defects such as cracks when exposed to harsh environments.

[0007] The present invention has been made in view of the above circumstances, and aims to provide an electronic component including a dielectric layer formed of a dielectric composition that is resistant to structural defects such as cracks even when exposed to a harsh environment. [Means for solving the problem]

[0008] The aspects of the present invention are as follows.

[0009] [1] An electronic component comprising a dielectric layer formed of a dielectric composition in a layered form and an electrode layer containing a base metal as a main component, The dielectric composition has the general formula A a B b C4O 15+ The composite oxide is mainly composed of a composite oxide represented by α, wherein A represents an element group containing at least barium, B represents an element group containing at least zirconium, and C represents an element group containing at least niobium, and a is 3.05 or more and b is 1.01 or more; The dielectric composition is an electronic component having a main phase composed of a composite oxide, a first phase containing barium, zirconium, silicon, and oxygen and different from the main phase, and a second phase containing barium, silicon, and oxygen and different from the main phase and the first phase.

[0010] [2] 16 μm on the cross section of the dielectric composition 2 In the area range, the ratio of the number of first phases to the number of second phases is 0.2 or more and 0.8 or less.

[0011] [3] The electronic device according to [1] or [2], wherein in the first phase, the ratio of the number of zirconium atoms to the total number of silicon and zirconium atoms is 0.25 or more and 0.45 or less.

[0012] [4] The electronic device according to any one of [1] to [3], wherein in the first phase, the ratio of the number of barium atoms to the total number of silicon and barium atoms is 0.35 or more.

[0013] [5] The electronic component according to any one of [1] to [4], wherein the average value of the area-equivalent circle diameter of the first phase is in the range of 10 nm to 200 nm.

[0014] [6] 1 μm in the cross section of the dielectric composition 2 The electronic component according to any one of [1] to [5], wherein the number of the first phases present therein is 0.1 or more and 1 or less.

[0015] [7] The electronic component according to any one of [1] to [6], wherein the first phase is crystalline.

[0016] [8] The electronic component according to [7], wherein the crystal system of the first phase is a cubic system. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a multilayer capacitor as a multilayer electronic component according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing a cross section of the dielectric composition. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below based on specific embodiments in the following order. 1. Electronic Components 1.1. Overall structure of multilayer capacitor 1.2.Dielectric Layer 1.3. Internal electrode layer 1.4.External electrode 2. Dielectric composition 2.1. Complex oxides 2.2. Phase 1 and Phase 2 2.3. Identification of the first and second phases 3. Manufacturing method of multilayer capacitors 4. Summary of this embodiment 5. Variations

[0019] (1. Electronic Components) The electronic component according to this embodiment is an electronic component having a dielectric layer exhibiting predetermined dielectric properties and electrodes. Such an electronic component may be an electronic component having a configuration in which one dielectric layer is sandwiched between electrodes, or may be a multilayer electronic component in which multiple dielectric layers are stacked with electrode layers interposed therebetween. In this embodiment, a multilayer capacitor will be described as an example of a multilayer electronic component.

[0020] (1.1. Overall structure of multilayer capacitor) FIG. 1 shows a multilayer capacitor 1 as an example of a multilayer electronic component according to this embodiment. The multilayer capacitor 1 has an element body 10 configured by alternately stacking dielectric layers 2 and internal electrode layers 3. A pair of external electrodes 4 is formed on both ends of the element body 10, and is electrically connected to the internal electrode layers 3 alternately arranged inside the element body 10. There are no particular restrictions on the shape of the element body 10, but it is usually a rectangular parallelepiped. There are also no particular restrictions on the dimensions of the element body 10, and the dimensions may be appropriate depending on the application.

[0021] (1.2. Dielectric Layer) The dielectric layer 2 is a layer of a dielectric composition described below. As a result, a multilayer capacitor including the dielectric layer 2 is less likely to suffer from structural defects such as cracks even when exposed to harsh environments.

[0022] The thickness of each dielectric layer 2 (interlayer thickness) is not particularly limited and can be set arbitrarily depending on the desired characteristics, application, etc. Usually, the interlayer thickness is preferably 20 μm or less, more preferably 10 μm or less. The number of laminated layers of the dielectric layers 2 can also be set arbitrarily. For example, in the case of a multilayer capacitor used for characteristic evaluation, the number of laminated layers may be on the order of several layers. On the other hand, in the case of a multilayer capacitor to be incorporated into a specific product, the number of laminated layers may be, for example, 20 or more.

[0023] (1.3. Internal electrode layer) 1, in this embodiment, the internal electrode layers 3 are stacked so that their ends are exposed on a pair of opposing surfaces of the element body 10. Specifically, the internal electrode layers 3 are arranged so that the ends of every other layer are exposed on the same surface of the pair of opposing surfaces of the element body 10.

[0024] The internal electrode layers 3 are made of a conductive material. In this embodiment, the main component of the internal electrode layers 3 is a base metal. The base metal is not particularly limited, and a conductive material known as a base metal, such as nickel (Ni), a Ni-based alloy, copper (Cu), or a Cu-based alloy, may be used. Note that Ni, a Ni-based alloy, Cu, or a Cu-based alloy may contain various trace components such as P in an amount of about 0.1 mass % or less. The internal electrode layers 3 may also be formed using a commercially available electrode paste. The thickness of the internal electrode layers 3 may be determined appropriately depending on the application, etc.

[0025] (1.4.External electrode) The external electrodes 4 are made of a conductive material. Known conductive materials such as nickel (Ni), copper (Cu), tin (Sn), silver (Ag), palladium (Pd), platinum (Pt), gold (Au), alloys of these, conductive resins, etc. may be used as the external electrodes 4. The thickness of the external electrodes 4 may be determined appropriately depending on the application, etc.

[0026] (2. Dielectric Composition) In this embodiment, the dielectric composition constituting the dielectric layer contains a composite oxide containing at least barium (Ba), zirconium (Zr), and niobium (Nb) as a main component. The composite oxide preferably accounts for 80% by mass or more, and more preferably 90% by mass or more, of the dielectric composition (100% by mass). Furthermore, the composite oxide preferably has a tungsten bronze structure.

[0027] (2.1. Complex oxides) The elements other than oxygen contained in the composite oxide are divided into three element groups ("A", "B", and "C"). In this embodiment, the composite oxide has the general formula A a B b C4O 15+A general formula is a generalized chemical formula expressed using element symbols and the ratio of the number of atoms thereof, and is expressed using symbols indicating a specific group of elements and the ratio of the element symbols and the number of atoms thereof.

[0028] "A" is a group of elements that includes at least barium (Ba), and in this embodiment, is preferably a group of elements consisting of divalent elements that occupy the gaps between oxygen octahedra in the tungsten bronze structure. "B" is a group of elements that includes at least zirconium (Zr), and in this embodiment, is preferably a group of elements consisting of tetravalent elements that form oxygen octahedra in the tungsten bronze structure. "C" is a group of elements that includes at least niobium (Nb), and in this embodiment, is preferably a group of elements consisting of pentavalent elements that form oxygen octahedra in the tungsten bronze structure. Furthermore, "a" in the above general formula indicates the atomic ratio of "A" when four atoms of the element that makes up "C" in the general formula are contained, and "b" in the above general formula indicates the atomic ratio of "B" when four atoms of the element that makes up "C" in the general formula are contained.

[0029] In this embodiment, "a" is 3.05 or more. Furthermore, "a" is preferably 3.10 or more. The upper limit of "a" is set within a range in which the effects of the present invention can be obtained. For example, "a" may be 3.50 or less, or 3.30 or less.

[0030] In this embodiment, "b" is 1.01 or more. Furthermore, "b" is preferably 1.05 or more. The upper limit of "b" is set within a range in which the effects of the present invention can be obtained. For example, "b" may be 1.50 or less, or 1.30 or less.

[0031] The above composite oxides have a stoichiometric composition of the general formula A3B1C4O 15In the composite oxide represented by the formula (1), "A" and "B" are contained in excess of "C" at a predetermined ratio. As a result, the composite oxide can exhibit high resistivity even when fired in a reducing atmosphere, and can prevent the dielectric composition from becoming a semiconductor or a conductor. In other words, even when a base metal that oxidizes when fired in an oxidizing atmosphere is used as the conductive material for the electrode, an electronic device having a dielectric composition containing the composite oxide as a main component can exhibit sufficient dielectric properties.

[0032] In this composite oxide, the amount of oxygen (O) may vary depending on the composition ratio of "A," "B," and "C," oxygen defects, etc. Therefore, in this embodiment, 15 The deviation of oxygen from the stoichiometric ratio is represented by "α". The range of "α" is, for example, about -1 or more and 1 or less. That is, in the general formula A a B b C4O 15+ In terms of α, "15+α" is within the range of 14 or greater and 16 or less.

[0033] In this embodiment, "A" may be Ba alone or may contain an element other than Ba. The element other than Ba ​​may be at least one selected from the divalent elements Ca and Sr. When the composite oxide contains Mg, a divalent element, the ionic radius of "A" is larger than that of "B" or "C," and therefore Mg, which has a smaller ionic radius, is included in "B" or "C." When Mg is included in "B" or "C," Mg is divalent and has a smaller valence than the elements included in "B" and "C," so it acts as an acceptor. As a result, the reduction resistance of the composite oxide can be maintained.

[0034] On the other hand, when "A" contains a divalent element other than Ba, the ratio of the total number of atoms constituting "A" to the total number of divalent elements other than Ba ​​is preferably 0.20 or less, and more preferably 0.10 or less, when the total number of atoms constituting "A" is 1.

[0035] "B" may be Zr alone, or may contain Mg, a tetravalent element other than Zr. Examples of the tetravalent element other than Zr include at least one selected from Ti and Hf. When "B" contains a tetravalent element other than Zr, the ratio of the total number of atoms constituting "B" to the total number of atoms of the tetravalent elements other than Zr is preferably 0.25 or less, and more preferably 0.125 or less.

[0036] "C" may be Nb alone, or may contain Mg or a pentavalent element other than Nb. An example of a pentavalent element other than Nb is Ta. When "C" contains a pentavalent element other than Nb, the ratio of the total number of atoms constituting "C" to the total number of atoms of the pentavalent elements other than Nb is preferably 0.10 or less.

[0037] (2.2. First and Second Phases) FIG. 2 shows a cross section of the dielectric composition. As shown in FIG. 2, the dielectric composition 2 includes a main phase 20 and grain boundaries 30 present between the main phases 20. The main phase 20 is a particle (main component particle) composed of the above-mentioned composite oxide, which is the main component. The average particle size of the main component particle is, for example, within a range of 0.01 to 2 μm. The grain boundary 30 is a region containing components other than the main component, components diffused from the main component, etc. The grain boundary 30 includes a region (two-particle grain boundary) 31 present between two adjacent main phases, a region (grain boundary triple junction) 32 present between three or more main phases, etc. In this embodiment, the grain boundary 30 includes a first phase 41 different from the main phase 20 and a second phase 42 different from the main phase 20 and the first phase 41. The first phase 41 and the second phase 42 are mainly present at the grain boundary triple junction.

[0038] The first phase contains barium (Ba), zirconium (Zr), silicon (Si), and oxygen (O), which form a composite oxide (Ba-Zr-Si-O) in this embodiment. The presence of the first phase at the grain boundaries controls the grain growth of the main component particles and can suppress the progression of cracks at the grain boundaries.

[0039] On the other hand, the second phase contains barium (Ba), silicon (Si), and oxygen (O), which in this embodiment form a composite oxide (Ba-Si-O). The second phase can promote sintering of the dielectric composition and improve the density of the dielectric composition. As a result, cracks are less likely to occur.

[0040] Therefore, the presence of both the first phase and the second phase in the dielectric composition makes it difficult for cracks to occur even in harsh environments, and even if cracks do occur, their progression is sufficiently suppressed. As a result, the occurrence of structural defects such as cracks is suppressed in electronic components having a dielectric layer made of the dielectric composition, and the reliability of the electronic components is improved.

[0041] 2, the first phase 41 and the second phase 42 are scattered among the main phase 20. Regarding the state of existence of the first phase and the second phase, in this embodiment, the first phase and the second phase are scattered among the main phase 20 within 16 μm on the cross section of the dielectric composition. 2 In this area range, the ratio of the number of first phases to the number of second phases (number of first phases / number of second phases) is preferably 0.2 or more and 0.8 or less. The first phases tend to be less likely to form in the dielectric composition than the second phases. Therefore, by increasing the number ratio of the first phases, cracks are less likely to occur and the progression of cracks can be further suppressed. However, if the number ratio of the first phases is too high, resistivity tends to decrease. Therefore, the upper limit of the number ratio of the first phases may be set from the perspective of resistivity. The ratio of the number of first phases to the number of second phases may be 0.25 or more, or 0.29 or more. Furthermore, the ratio of the number of first phases to the number of second phases may be 0.75 or less, or 0.74 or less.

[0042] Furthermore, the first phase is formed in a unit area (1 μm 2 ) may be present in an amount of 0.1 to 1 per 1 μm. This can further suppress the progression of cracks. 2The number of the first phases per unit area may be 0.12 or more and 0.2 or less.

[0043] Furthermore, when the diameter of a circle having the same area as the area of ​​the first phase is defined as the equivalent-area circle diameter of the first phase, the average value of the equivalent-area circle diameter may be in the range of 10 nm to 200 nm. This can further suppress the progression of cracks. The average value of the equivalent-area circle diameter may be in the range of 15 nm to 190 nm.

[0044] In the first phase, the ratio of the number of Zr atoms to the total number of Si and Zr atoms (hereinafter, sometimes referred to as Zr / (Si+Zr)) may be 0.25 or more and 0.45 or less. In Ba-Zr-Si-O, when Zr / (Si+Zr) is within the above range, the progression of cracks can be further suppressed. Zr / (Si+Zr) may be 0.35 or more and 0.43 or less.

[0045] In addition, in the first phase, the ratio of the number of Ba atoms to the total number of Si and Ba atoms (hereinafter, sometimes referred to as Ba / (Si+Ba)) may be 0.35 or more. In Ba-Zr-Si-O, when Ba / (Si+Ba) is within the above range, the progression of cracks can be further suppressed. Note that the above ratio is less than 1.

[0046] The composite oxide constituting the first phase, i.e., Ba-Zr-Si-O, may be crystalline or amorphous. In this embodiment, Ba-Zr-Si-O is preferably crystalline, and its crystal system is preferably cubic. This further suppresses crack propagation.

[0047] 2.3. Identification of the First and Second Phases In the dielectric composition, a known method can be used to identify the main phase, the first phase, and the second phase.

[0048] In this embodiment, first, in a cross-sectional image of a dielectric composition obtained by a scanning transmission electron microscope (STEM) or a scanning electron microscope (SEM), the main phase can be distinguished from the first and second phases based on the difference in contrast in the STEM dark-field image. Next, the first and second phases can be identified by mapping analysis using energy dispersive X-ray spectroscopy (EDS) or wavelength dispersive X-ray spectroscopy (WDS). For example, a mapping analysis is performed on a cross-section of a dielectric composition 2 as shown in FIG. 2 to obtain a mapping image of each element constituting the dielectric composition. In the mapping image, the atomic ratio of a predetermined element in a region corresponding to each pixel can be identified based on the brightness level of each pixel. For example, in the mapping image, a region where the atomic ratios of both Si and Zr are high can be determined as the first phase, and a region where the atomic ratio of Si is high and the atomic ratio of Zr is low can be determined as the second phase. Specifically, a region where the atomic ratio of Si to Ba, Zr, Nb, and Si is 0.1 or more and the atomic ratio of Zr is 0.05 or more is determined to be the first phase. A region where the atomic ratio of Si to Ba, Zr, Nb, and Si is 0.1 or more and the atomic ratio of Zr is less than 0.05 is determined to be the second phase. The main phase, first phase, and second phase may each be identified by mapping analysis.

[0049] The ratio of the number of second phases to the number of first phases is 16 μm 2 The number of the first phases and the number of the second phases identified as above can be calculated by counting the number of the first phases and the number of the second phases in an area range of 16 μm Therefore, when identifying the first phase and the second phase, the above analysis is performed in an area range of 16 μm 2 It is preferable to carry out the process for an area of ​​.

[0050] In addition, 1 μm of the first phase identified as above 2 The number of hits can also be calculated. Furthermore, by calculating the area of ​​the first phase identified as described above, the area-equivalent circle diameter can be calculated. The area of ​​the first phase can be calculated by image processing.

[0051] The "Zr / (Si + Zr)" and "Ba / (Si + Ba)" in the first phase (Ba-Zr-Si-O) described above can be calculated by performing point analysis by EDS or WDS on the first phase identified as described above. Specifically, point analysis is performed on Ba, Zr, and Si in each of three or more first phases, and the average of the measured atomic ratios of Ba, Zr, and Si is taken as the atomic ratio of Ba, Zr, and Si in the first phase. "Zr / (Si + Zr)" is calculated from the obtained atomic ratios of Zr and Si, and "Ba / (Si + Ba)" is calculated from the obtained atomic ratios of Ba and Si.

[0052] In this embodiment, the crystallinity of the first phase (Ba-Zr-Si-O) is determined by whether or not Kikuchi lines resulting from an electron beam incident on the first phase are observed using a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM). If Kikuchi lines are observed, the first phase is determined to be crystalline. If the first phase is crystalline, the crystal system of the first phase can be identified by electron beam diffraction or the like.

[0053] (3. Manufacturing method of multilayer capacitor) Next, an example of a method for manufacturing the multilayer capacitor 1 shown in FIG. 1 will be described below.

[0054] The multilayer capacitor 1 according to this embodiment can be manufactured by a known method similar to that used for conventional multilayer capacitors. An example of such a known method is a method in which a green chip is produced using a paste containing raw materials for a dielectric composition, and then fired to manufacture a multilayer capacitor. The manufacturing method will now be described in detail.

[0055] First, starting materials for the dielectric composition are prepared. As the starting materials, oxides of the elements contained in the dielectric composition can be used. Also, various compounds that become components constituting the dielectric composition upon firing can be used. Examples of various compounds include carbonates, oxalates, nitrates, hydroxides, and organometallic compounds. These starting materials may be in the form of solids or liquids. In this embodiment, the starting materials are preferably in the form of powders.

[0056] In this embodiment, it is preferable to use the above starting materials to obtain the raw materials for forming the main phase, the raw materials for forming the first phase, and the raw materials for forming the second phase.

[0057] The raw material for forming the main phase can be obtained as a calcined powder for the main phase, for example, as follows. a B b C4O 15+ The starting materials are weighed in predetermined proportions so as to obtain a composite oxide composition represented by α, and then wet-mixed for a predetermined time using a ball mill or the like to obtain a mixed powder. The obtained mixed powder is dried and then heat-treated in air at a temperature in the range of 700 to 1300°C to obtain a calcined powder for the main phase. After the heat treatment, wet-pulverization may be performed for a predetermined time using a ball mill or the like to adjust the particle size of the calcined powder for the main phase. This calcined powder for the main phase is a powder represented by the general formula A a B b C4O 15+ It is a powder of a composite oxide represented by α.

[0058] The raw materials for forming the first phase can be obtained as a calcined powder for the first phase, for example, as follows. First, the starting materials are weighed in a predetermined ratio so as to obtain the above-mentioned Ba-Zr-Si-O, and then wet-mixed using a ball mill or the like for a predetermined time to obtain a mixed powder. The obtained mixed powder is dried and then heat-treated in air at a temperature range of 700 to 1300°C to obtain a calcined powder for the first phase. After the heat treatment, the particle size of the calcined powder for the first phase may be adjusted by wet-pulverizing using a ball mill or the like for a predetermined time. This calcined powder for the first phase is a powder of the composite oxide Ba-Zr-Si-O. "Zr / (Si+Zr)" and "Ba / (Si+Ba)" can be controlled by changing the ratio of the raw materials containing Ba, the raw materials containing Zr, and the raw materials containing Si.

[0059] The raw materials for forming the second phase can be obtained as a calcined powder for the second phase, for example, as follows. First, the starting materials are weighed in a predetermined ratio so as to obtain the above-mentioned Ba-Si-O, and then wet-mixed using a ball mill or the like for a predetermined time to obtain a mixed powder. The obtained mixed powder is dried and then heat-treated in air at a temperature in the range of 700 to 1100°C to obtain a calcined powder for the second phase. After the heat treatment, the particle size of the calcined powder for the second phase may be adjusted by wet-pulverizing using a ball mill or the like for a predetermined time. This calcined powder for the second phase is a powder of the composite oxide Ba-Si-O.

[0060] Next, a paste for producing a green chip is prepared. The obtained calcined powder for the main phase, the calcined powder for the first phase, and the calcined powder for the second phase are mixed in a predetermined ratio to obtain a raw material powder for the dielectric composition. In this manner, in this embodiment, the complex oxides constituting the first and second phases are formed in advance, and then mixed with the complex oxide constituting the main phase and fired as described below to obtain the dielectric composition. In contrast, even if a compound of an element contained in the complex oxide constituting the first and / or second phase (e.g., silicon oxide, zirconium oxide, barium carbonate, etc.) is mixed with the complex oxide constituting the main phase and fired, a dielectric composition having both the first and second phases cannot be obtained.

[0061] In this embodiment, the amount of calcined powder for the first phase added to 100 parts by mass of calcined powder for the main phase is preferably 0.1 parts by mass or more and 2 parts by mass or less, and the amount of calcined powder for the second phase added to 100 parts by mass of calcined powder for the main phase is preferably 0.2 parts by mass or more and 4 parts by mass or less. By adjusting the amount of calcined powder for the first phase, the amount of calcined powder for the second phase added, the particle size of the calcined powder for the first phase, and the particle size of the calcined powder for the second phase, the ratio of the number of first phases to the number of second phases, 1 μm 2 The number of first phases present in the sintered body and the equivalent circle diameter of the first phases can be controlled.

[0062] A binder and a solvent are further added to the obtained mixed powder, and the mixture is kneaded to form a paint to prepare a dielectric layer paste. Known binders and solvents may be used. The dielectric layer paste may also contain additives such as a plasticizer and a dispersant, as necessary.

[0063] The internal electrode layer paste is obtained by kneading the above-mentioned raw materials of the conductive material, a binder, and a solvent. Known binders and solvents may be used. The internal electrode layer paste may contain additives such as co-materials and plasticizers as necessary.

[0064] The external electrode paste can be prepared in the same manner as the internal electrode layer paste.

[0065] Using each of the obtained pastes, green sheets and internal electrode patterns are formed, which are then laminated and cut to obtain green chips.

[0066] The obtained green chip is subjected to a binder removal treatment as needed. The binder removal treatment conditions may be known conditions, and for example, the holding temperature is preferably 200 to 350°C.

[0067] After the binder removal process, the green chip is fired to obtain the element body. In this embodiment, since the composite oxide constituting the main phase has the above-mentioned composition, firing can be performed in a reducing atmosphere (reducing firing). Other firing conditions may be known conditions, and for example, the holding temperature is preferably 1200 to 1450°C.

[0068] After firing, the obtained element body is subjected to a reoxidation treatment (annealing) as necessary. The annealing conditions may be well-known conditions, for example, the oxygen partial pressure during annealing is preferably higher than the oxygen partial pressure during firing, and the holding temperature is preferably 1150°C or less.

[0069] The dielectric layer of the element body obtained as described above is a layer of the above-mentioned dielectric composition. The end faces of this element body are polished, and an external electrode paste is applied and baked to form the external electrodes 4. Then, if necessary, a coating layer is formed on the surface of the external electrodes 4 by plating or the like.

[0070] In this manner, a multilayer capacitor as an example of an electronic component according to this embodiment is manufactured.

[0071] (4. Summary of this embodiment) In this embodiment, the dielectric layer provided in the electronic component is a compound represented by the general formula A a B b C4O 15+ The dielectric composition is composed of a dielectric composition containing, as a main component, a complex oxide represented by the formula (α). This dielectric composition has a main phase composed of the complex oxide and grain boundaries existing between the main phases. The grain boundaries include at least a first phase composed of a complex oxide containing barium, zirconium, and silicon (Ba-Zr-Si-O) and a second phase composed of a complex oxide containing barium and silicon (Ba-Si-O).

[0072] The second phase promotes sintering of the complex oxide constituting the main phase, thereby improving the density of the resulting dielectric composition and, as a result, suppressing the occurrence of cracks. The first phase, by being present at grain boundaries, controls the grain growth of the main phase and, even if cracks do occur, can suppress their progression.

[0073] Therefore, the presence of both the first phase and the second phase in the dielectric composition makes it difficult for cracks to occur, and even if cracks do occur, their progression can be suppressed, thereby ensuring sufficient reliability of the electronic component.

[0074] Moreover, general formula A a B b C4O 15+ In the composite oxide represented by α, by setting "a" to 3.05 or more and "b" to 1.01 or more, the composite oxide is provided with reduction resistance. As a result, even when an electrode pattern mainly composed of a base metal and the raw materials of the dielectric composition are subjected to reduction firing, the resistivity of the resulting dielectric composition can be maintained high (preventing the dielectric composition from becoming a semiconductor or conductor), and the dielectric properties expected of an insulator can be fully exhibited. Furthermore, since the electrode layer can be composed of a base metal, electronic components can be obtained at low cost.

[0075] (5. Modifications) In the above-described embodiment, the case where the electronic component according to the present embodiment is a multilayer capacitor has been described. However, the electronic component according to the present embodiment may be an electronic component other than a multilayer capacitor as long as it has the dielectric composition described above.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified in various ways within the scope of the present invention. [Example]

[0077] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0078] (Experiment 1) First, powders of barium carbonate (BaCO3), zirconium oxide (ZrO2), niobium oxide (Nb2O5), and silicon oxide (SiO2) were prepared as starting materials for the dielectric composition.

[0079] (Sample No. 1) The prepared starting materials were weighed so that the molar ratio of BaCO3, ZrO2, and Nb2O5 was BaCO3:ZrO2:Nb2O5 = 3.1:1.1:2. The weighed powders were wet-mixed in a ball mill using ion-exchanged water as a dispersion medium for 16 hours, and the mixture was dried to obtain a mixed powder. The resulting mixed powder was then heat-treated in air at a holding temperature of 900°C for 2 hours. The heat-treated powder was then placed in a ball mill together with 2mm diameter stabilized zirconia media and ion-exchanged water and wet-milled for 16 hours to obtain a calcined powder. The resulting calcined powder mainly constitutes the main phase (complex oxide) in the dielectric composition. This calcined powder was used as the main phase calcined powder.

[0080] Next, the prepared starting materials were weighed so that the molar ratio of BaCO3, ZrO2, and SiO2 was BaCO3:ZrO2:SiO2 = 1.86:0.54:1. The weighed powders were wet-mixed in a ball mill using ion-exchanged water as a dispersion medium for 16 hours, and the mixture was dried to obtain a mixed powder. The resulting mixed powder was then heat-treated in air at 900°C for 2 hours. The heat-treated powder was then placed in a ball mill together with 2mm diameter stabilized zirconia media and ion-exchanged water and wet-milled for 16 hours to obtain a calcined powder. The resulting calcined powder was a composite oxide powder containing Ba, Zr, and Si (Ba-Zr-Si-O powder), and mainly constituted a first phase different from the main phase in the dielectric composition. This calcined powder was designated as the calcined powder for the first phase.

[0081] Next, the prepared starting materials were weighed so that the molar ratio of BaCO3 and SiO2 was BaCO3:SiO2 = 0.6:0.4. The weighed powders were wet-mixed in a ball mill using ion-exchanged water as a dispersion medium for 16 hours, and the mixture was dried to obtain a mixed powder. The resulting mixed powder was then heat-treated in air at a holding temperature of 900°C for 2 hours. The heat-treated powder was then placed in a ball mill together with 2 mm diameter stabilized zirconia media and ion-exchanged water and wet-pulverized for 16 hours to obtain a calcined powder. The obtained calcined powder was a composite oxide powder containing Ba and Si (Ba-Si-O powder), which mainly constitutes a second phase different from the main phase and the first phase in the dielectric composition. This calcined powder was used as the calcined powder for the second phase.

[0082] The calcined powder for the main phase, the calcined powder for the first phase, and the calcined powder for the second phase obtained above were mixed to obtain a raw material powder for the dielectric composition. The amount of the calcined powder for the first phase added to 100 parts by mass of the calcined powder for the main phase was 1.0 part by mass, and the amount of the calcined powder for the second phase added to 100 parts by mass of the calcined powder for the main phase was 1.8 parts by mass. The average particle size of the calcined powder for the first phase was 0.05 μm, and the average particle size of the calcined powder for the second phase was 0.05 μm.

[0083] The obtained raw material powder of the dielectric composition was mixed with a binder and a solvent to prepare a paste. The obtained paste was used to form a green sheet that would become a dielectric layer, and a paste containing nickel (Ni) powder as a conductive material was printed on top of it to form an internal electrode pattern that would become an internal electrode layer. These were then stacked and pressure-bonded to form a green laminate. Furthermore, the green laminate was cut into a predetermined shape to obtain a green chip.

[0084] The obtained green chip was subjected to a binder removal treatment, fired in a reducing atmosphere, and then annealed to obtain a sintered body (element body) in which internal electrode layers and dielectric layers formed of layers of dielectric composition were laminated and integrated. The firing conditions were a temperature rise rate of 200°C / h, a holding temperature of 1320°C, and a holding time of 2 hours. The atmospheric gas was a mixed gas of nitrogen and hydrogen (hydrogen concentration 3%) humidified to a dew point of 20°C. The annealing conditions were a holding temperature of 1050°C, and a holding time of 2 hours. The atmospheric gas was nitrogen gas humidified to a dew point of 20°C. Next, the obtained element body was subjected to the following characteristic evaluations.

[0085] (crack rate) To evaluate the durability of the element body against cracks, a pressure cooker test (PCT) was conducted. In the PCT, the element body sample was heated at a temperature of 121°C, a relative humidity of 95%, and an atmospheric pressure of 2.026 x 10 5 The element was exposed to an environment of 20 Pa for 24 hours. After the test, the appearance of the element body sample was observed under a stereomicroscope to evaluate whether or not cracks had occurred in the element body. PCT was performed on 20 element body samples, and samples in which cracks occurred in one or less of the 20 were judged to be good. It is more preferable if no cracks occurred in any of the 20 samples. The results are shown in Table 1.

[0086] After polishing the obtained element body, an electrode paste containing Cu powder, binder, and solvent was applied to the end faces where the internal electrode layers were exposed, and after drying, sintering was performed to form external electrodes, thereby obtaining a multilayer capacitor sample. In the multilayer capacitor sample, the dielectric layer thickness was 5 μm, the internal electrode layer thickness was 1.2 μm, and the number of dielectric layers sandwiched between the internal electrode layers was four. The obtained multilayer capacitor sample was evaluated for the presence or absence of a first phase and a second phase in the dielectric composition.

[0087] A part of the cross section of the dielectric layer of the obtained multilayer capacitor was thinned using a focused ion beam (FIB) processing device to prepare a sample. The prepared sample was observed using a scanning transmission electron microscope (STEM). The observation field was 4 μm × 4 μm, and the field area was 16 μm. 2 The main phase was distinguished from other regions by contrast in the observation field. Next, energy dispersive X-ray spectroscopy (EDS) was used to obtain mapping images of barium (Ba), zirconium (Zr), niobium (Nb), and silicon (Si) in the observation field.

[0088] From each mapping image of Ba, Zr, and Si, in the region other than the main phase, the region where Ba, Zr, and Si were observed in large amounts was determined to be a phase containing Ba, Zr, Si, and O (first phase), and the region where Ba and Si were observed in large amounts and Zr was observed in small amounts was determined to be a phase containing Ba, Si, and O (second phase). In sample number 1, the main phase, the first phase, and the second phase were observed.

[0089] The obtained multilayer capacitor samples were subjected to the following characteristic evaluations.

[0090] (resistivity) The insulation resistance of the multilayer capacitor sample was measured at a reference temperature (25°C) using a digital resistance meter (R8340 manufactured by ADVANTEST). The resistivity was calculated from the measured insulation resistance, the electrode area, and the thickness of the dielectric layer. A higher resistivity is preferable, and in this example, the resistivity was 5.0 × 10 8 A sample with a resistivity of 1.0×10 (Ω·m) or more was judged to be good. 9 The results are shown in Table 1.

[0091] (Sample No. 2) An element body and a multilayer capacitor sample were prepared in the same manner as sample No. 1, except that the calcined powder for the first phase and the calcined powder for the second phase were not blended and the calcined powder for the main phase was used as the raw material powder for the dielectric composition. The prepared element body and multilayer capacitor samples were evaluated in the same manner as sample No. 1. The results are shown in Table 1.

[0092] (Sample No. 3) An element body and a multilayer capacitor sample were prepared in the same manner as sample No. 1, except that the calcined powder for the first phase and the calcined powder for the second phase were not mixed, and a powder obtained by mixing silicon oxide powder with the calcined powder for the main phase was used as the raw material powder for the dielectric composition. The amount of silicon oxide powder added was 2 parts by mass per 100 parts by mass of the calcined powder for the main phase. The prepared element body and multilayer capacitor samples were evaluated in the same manner as sample No. 1. The results are shown in Table 1.

[0093] (Sample No. 4) An element body and a multilayer capacitor sample were prepared in the same manner as sample No. 1, except that the calcined powder for the first and second phases was not mixed, and instead a powder prepared by mixing zirconium oxide powder with the calcined powder for the main phase was used as the raw material powder for the dielectric composition. The amount of zirconium oxide powder added per 100 parts by mass of the calcined powder for the main phase was 0.3 parts by mass. The prepared element body and multilayer capacitor samples were evaluated in the same manner as sample No. 1. The results are shown in Table 1. In sample No. 4, no first or second phase was observed, but a phase containing zirconium and oxygen was observed.

[0094] (Sample No. 5) The element body and multilayer capacitor samples were prepared in the same manner as sample number 1, except that the calcined powder for the second phase was not blended, and the powder obtained by blending the calcined powder for the first phase with the calcined powder for the main phase was used as the raw material powder for the dielectric composition. The amount of the calcined powder for the first phase added to 100 parts by mass of the calcined powder for the main phase was 0.5 parts by mass. The prepared element body and multilayer capacitor samples were evaluated in the same manner as sample number 1. The results are shown in Table 1.

[0095] (Sample No. 6) An element body and a multilayer capacitor sample were prepared in the same manner as sample No. 1, except that the calcined powder for the first phase was not blended, and the calcined powder for the second phase was blended with the calcined powder for the main phase, and this was used as the raw powder for the dielectric composition. The amount of calcined powder for the second phase added to 100 parts by mass of the calcined powder for the main phase was 1.8 parts by mass. The prepared element body and multilayer capacitor samples were evaluated in the same manner as sample No. 1. The results are shown in Table 1. In sample No. 6, no first or second phase was observed, but a phase containing barium, zirconium, and oxygen was observed.

[0096] (Sample No. 7) The element body and multilayer capacitor samples were prepared in the same manner as Sample No. 1, except that the calcined powder for the first and second phases was not blended, and instead, the calcined powder of zirconium oxide powder and silicon oxide powder was blended with the calcined powder for the main phase to form the raw powder for the dielectric composition. The calcined powder of zirconium oxide powder and silicon oxide powder (Zr-Si-O powder) was prepared in the same manner as the calcined powder for the second phase, except that the molar ratio of ZrO2 to SiO2 was weighed out so that ZrO2:SiO2 was 1:1. The amount of Zr-Si-O powder added per 100 parts by mass of the calcined powder for the main phase was 2 parts by mass. The fabricated element body and multilayer capacitor samples were evaluated in the same manner as Sample No. 1. The results are shown in Table 1.

[0097] (Sample No. 8) A green chip was obtained in the same manner as in Experiment 1, except that platinum (Pt) was used instead of nickel as the conductive material. The obtained green chip was fired in air at a holding temperature of 1320°C for 2 hours instead of firing and annealing in a reducing atmosphere, and an element body and a multilayer capacitor sample were fabricated in the same manner as in Sample No. 1. The fabricated element body and multilayer capacitor sample were evaluated in the same manner as in Sample No. 1. The results are shown in Table 1.

[0098] [Table 1]

[0099] From Table 1, it was confirmed that when both the first phase and the second phase were present, both the crack rate and resistivity were good.

[0100] (Experiment 2) For sample numbers 11 to 14, the amount of calcined powder for the first phase and the amount of calcined powder for the second phase added per 100 mass parts of calcined powder for the main phase were changed, and the ratio of the amount of calcined powder for the first phase to the amount of calcined powder for the second phase added was changed. Except for this, the element body and the multilayer capacitor samples were prepared in the same manner as sample number 1.

[0101] For sample numbers 1 and 11 to 14, the number of first phases and second phases observed in each observation field was counted, and the number of first phases and second phases in each observation field was calculated. The ratio of the number of first phases to the number of second phases was calculated from the average value of the calculated numbers of first phases and second phases. The results are shown in Table 2.

[0102] [Table 2]

[0103] From Table 2, it was confirmed that when the ratio of the number of first phases to the number of second phases was within the above-mentioned range, both the crack rate and resistivity were good.

[0104] (Experiment 3) For samples 21 and 22, the element body and multilayer capacitor samples were prepared using the same method as for sample 1, except that the molar ratio of ZrO2 and SiO2 was changed in the calcined powder for the first phase. For samples 1, 21, and 22, the first phase was identified using the same method as in Experiment 1, and point analysis was performed on each of the five identified first phases using EDS using STEM. From the obtained point analysis results, the atomic ratio of Zr and Si was obtained, and Zr / (Si+Zr) was calculated. The results are shown in Table 3.

[0105] [Table 3]

[0106] From Table 3, it was confirmed that when Zr / (Si+Zr) is within the above range, the crack rate is good.

[0107] (Experiment 4) For samples 31 and 32, the element body and multilayer capacitor samples were prepared using the same method as for sample 1, except that the molar ratio of BaCO3 and SiO2 was changed in the calcined powder for the first phase. For samples 1, 31, and 32, the first phase was identified using the same method as in Experiment 1, and point analysis was performed on each of the five identified first phases using EDS using STEM. From the point analysis results, the atomic ratio of Ba and Si was obtained, and Ba / (Si+Ba) was calculated. The results are shown in Table 4.

[0108] [Table 4]

[0109] From Table 4, it was confirmed that when Ba / (Si+Ba) is within the above range, the crack rate is good.

[0110] (Experiment 5) For sample numbers 41 to 44, element bodies and multilayer capacitor samples were prepared using the same method as sample number 1, except that the particle size of the calcined powder for the first phase was changed. For sample numbers 1 and 41 to 44, the first phase was identified using the same method as in Experiment 1, and the area of ​​the first phase was calculated using image processing. From the calculated area, the equivalent area circle diameter was calculated, and the average value was calculated to obtain the average equivalent area circle diameter. The results are shown in Table 5.

[0111] [Table 5]

[0112] From Table 5, it was confirmed that when the area circle equivalent diameter of the first phase is within the above-mentioned range, the crack rate is good.

[0113] (Experiment 6) For sample numbers 51 and 52, the amount of calcined powder for the first phase added to 100 parts by mass of the calcined powder for the main phase was changed, but samples of the element body and the multilayer capacitor were prepared in the same manner as for sample number 1. For sample numbers 1, 51, and 52, the first phase was identified in the same manner as in experiment 1, and the first phase was measured by 1 μm 2 The number of first phases in the sample was calculated. The results are shown in Table 6.

[0114] [Table 6]

[0115] From Table 6, 1 μm 2 It was confirmed that when the number of the first phases in the sample was within the above-mentioned range, the crack rate was good.

[0116] (Experiment 7) For sample No. 61, the element body and multilayer capacitor sample were prepared using the same method as for sample No. 1, except that when preparing the calcined powder for the first phase, the prepared starting materials were weighed so that the molar ratio of BaCO3, ZrO2, and SiO2 was BaCO3:ZrO2:SiO2 = 1:1:3. For samples Nos. 1 and 61, the first phase was identified using the same method as in Experiment 1, and the presence or absence of Kikuchi lines in the first phase was evaluated using STEM. Kikuchi lines were observed in both samples Nos. 1 and 61. Therefore, the first phases of sample Nos. 1 and 61 were crystalline. Furthermore, the crystal systems of the first phases of sample Nos. 1 and 61 were evaluated using electron diffraction. The results are shown in Table 5.

[0117] [Table 7]

[0118] From Table 7, it was confirmed that when the crystal system of the first phase is a cubic system, the crack rate is good.

[0119] (Experiment 8) For sample numbers 71 and 72, the element body and multilayer capacitor samples were prepared by the same method as for sample number 1, except that barium titanate (sample number 71) and calcium zirconate (sample number 72) were used as the calcined powder for the main phase. For sample numbers 71 and 72, the first and second phases were identified by the same method as in Experiment 1. Both samples contained both the first and second phases.

[0120] Next, for samples 1, 71, and 72, the capacitance was measured using a digital LCR meter (Hewlett-Packard, 4284A) at room temperature of 25°C, a frequency of 1 kHz, and an input signal level (measurement voltage) of 1.0 Vrms while applying a DC bias with a field strength of 15 V / μm. The relative dielectric constant when the DC bias was applied was calculated from the measured capacitance, the effective electrode area, the inter-electrode distance, and the dielectric constant of vacuum. The results are shown in Table 8.

[0121] [Table 8]

[0122] From Table 8, it was confirmed that when the main phase is a composite oxide having a perovskite structure of barium titanate and calcium zirconate, the relative dielectric constant is low when a DC bias is applied. [Explanation of symbols]

[0123] 1... Multilayer capacitor 10... Element body 2... Dielectric layer (dielectric composition) 20…Main phase 41...First Phase 42...Second Phase 3… Internal electrode layer 4... External electrode

Claims

1. An electronic component comprising a dielectric layer in which a dielectric composition is formed in a layered form, and an electrode layer containing a base metal as a main component, The dielectric composition is represented by the general formula A a B b C 4 O 15+ a, wherein A represents an element group containing at least barium, B represents an element group containing at least zirconium, C represents an element group containing at least niobium, a is 3.05 or more, and b is 1.01 or more, The dielectric composition has a main phase composed of the composite oxide, a first phase containing barium, zirconium, silicon and oxygen and different from the main phase, and a second phase containing barium, silicon and oxygen and different from the main phase and the first phase.

2. 16 μm on the cross section of the dielectric composition 2 2. The electronic component according to claim 1, wherein the ratio of the number of the first phases to the number of the second phases is 0.2 or more and 0.8 or less in an area range of 0.2 to 0.

8.

3. 3. The electronic component according to claim 1, wherein in the first phase, the ratio of the number of zirconium atoms to the total number of silicon and zirconium atoms is 0.25 or more and 0.45 or less.

4. 3. The electronic component according to claim 1, wherein in the first phase, the ratio of the number of barium atoms to the total number of silicon and barium atoms is 0.35 or more.

5. 3. The electronic component according to claim 1, wherein the average equivalent circle diameter of the first phase is in the range of 10 nm to 200 nm.

6. In the cross section of the dielectric composition, 2 3. The electronic component according to claim 1, wherein the number of the first phases present therein is 0.1 or more and 1 or less.

7. 3. The electronic component according to claim 1, wherein the first phase is crystalline.

8. 8. The electronic component according to claim 7, wherein the crystal system of the first phase is a cubic system.

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