Dielectrics, multilayer ceramic capacitors, and electronic components

Abstract

The present invention provides a dielectric material with excellent reliability, a multilayer ceramic capacitor using the dielectric material, and electronic components. [Solution] The dielectric of this technology includes dielectric particles, at least one of the dielectric particles includes a main component and a minor component, at least one of the dielectric particles is surrounded by a boundary region containing a specific element that constitutes the minor component, at least one of the dielectric particles surrounded by the boundary region has a plurality of regions with different content ratios of the minor component excluding the specific element, and of the plurality of regions, at least two of the regions have different crystal orientations.

Description

[Technical Field]

[0001] This technology relates to dielectrics, multilayer ceramic capacitors using the dielectric, and electronic components using the dielectric. [Background technology]

[0002] Electronic components used in mobile devices and automotive applications, as well as multilayer ceramic capacitors, require high reliability, and the dielectric materials used in them also require similar reliability.

[0003] Patent Document 1 discloses an invention relating to a dielectric ceramic composition and a multilayer ceramic capacitor including a dielectric layer made of the dielectric ceramic composition, wherein the dielectric ceramic composition includes a phase consisting substantially only of the main component (main component phase) and a phase in which rare earth element R is solid-dissolved (diffused) in the main component (diffusion phase), and the high-temperature load life is improved by adjusting the area ratio of the main component phase and the diffusion phase and the composition range of the diffusion phase. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-178684 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The inventors investigated a means to effectively improve high-temperature load life using an approach different from that described in Patent Document 1.

[0006] This technology was developed in view of the aforementioned problems, and its purpose is to provide a dielectric material with excellent reliability, a multilayer ceramic capacitor using the dielectric material, and electronic components. [Means for solving the problem]

[0007] The dielectric of this technology includes dielectric particles, at least one of the dielectric particles includes a main component and a minor component, at least one of the dielectric particles is surrounded by a boundary region containing a specific element constituting the minor component, at least one of the dielectric particles surrounded by the boundary region has a plurality of regions with different content ratios of the minor component excluding the specific element, and of the plurality of regions, at least two of the regions have different crystal orientations.

[0008] The multilayer ceramic capacitor of this technology includes a dielectric layer containing the dielectric described above, and electrodes. The electronic components of this technology contain the dielectric material described above. [Effects of the Invention]

[0009] The dielectric material of this technology, as well as multilayer ceramic capacitors and electronic components using it, can extend the lifespan under high-temperature loads and achieve high reliability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partial cross-sectional perspective view of a multilayer ceramic capacitor according to an embodiment of this technology. [Figure 2] This is a partially enlarged cross-sectional view of a dielectric according to an embodiment of the present technology, showing an enlarged view of a portion of the dielectric layer 2 and internal electrode layer 3 in Figure 1. [Figure 3] This is a partially enlarged cross-sectional view of dielectric particles according to an embodiment of the present technology, showing an enlarged view of area E in Figure 2. [Figure 4] This is a partially enlarged cross-sectional view of dielectric particles according to an embodiment of this technology. [Figure 5] This is a partially enlarged cross-sectional view of dielectric particles according to an embodiment of this technology. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings. Note that the present technology is not limited to the following embodiments, and various modifications can be made within the scope of the gist thereof.

[0012] [Multilayer Ceramic Capacitor 1] FIG. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 1 according to an embodiment of the present technology.

[0013] As shown in FIG. 1, the multilayer ceramic capacitor 1 has a capacitor element body 4 in which a dielectric layer 2 functioning as a dielectric and an internal electrode layer 3 are alternately laminated. The internal electrode layers 3 are laminated so as to be alternately exposed from both side surfaces of the capacitor element body 4.

[0014] As shown in FIG. 1, a pair of external electrodes 5 are formed on both end faces of the capacitor element body 4. Each external electrode 5 is electrically connected to each internal electrode layer 3 alternately exposed from both side surfaces of the capacitor element body 4, thereby constituting a capacitor circuit. The capacitor element body 4 shown in FIG. 1 is substantially rectangular parallelepiped, but the shape of the capacitor element body 4 is not particularly limited.

[0015] The material of the internal electrode layer 3 is not limited, but it has a conductive material and is composed mainly of a base metal such as Ni, Cu, Sn or a noble metal such as Pd, Ag. The internal electrode layer 3 is formed as a sintered body of a conductive paste containing a conductive material. The number of layers of the internal electrode layer 3 depends on the number of layers of the dielectric layer 2.

[0016] [Dielectric Layer 2] The number of layers of the dielectric layer 2 laminated alternately with the internal electrode layer 3 and the film thickness per layer are not particularly limited. For example, the number of layers is 1 or more, 5 or more, 20 or more, 50 or more, or 100 or more. Also, the film thickness per layer is about 100 nm or more and several tens of μm or less. FIG. 2 is a partial enlarged cross-sectional view of the dielectric layer 2 according to an embodiment of the present technology, showing a part of FIG. 1 enlarged.

[0017] As shown in FIG. 2, the dielectric layer 2 contains a plurality of dielectric particles 10. In FIG. 2, in order to emphasize the dielectric particles 10, the size of the dielectric particles 10 is shown larger with respect to the film thickness of the dielectric layer 2, and the actual ratio is not shown.

[0018] [Dielectric particles 10] FIG. 3 is an enlarged cross-sectional view of the dielectric particle 10 extracted from the portion E shown in FIG. 2.

[0019] The dielectric particle 10 includes a main component and a sub-component. The dielectric particle 10 has a boundary region 11 surrounding the outer periphery, and the boundary region 11 contains a specific element constituting the sub-component. The "boundary region 11" may be referred to as a boundary layer or a boundary phase. The main component of the dielectric particle 10 means a component that occupies 70 mol% or more of the dielectric particle, and the sub-component of the dielectric particle 10 means a component other than the main component of the dielectric particle. Alternatively, the main component refers to the component constituting the core 12.

[0020] The boundary region 11 is defined to define the boundary between adjacent dielectric particles 10 and does not specify the thickness. In the present technology, it is sufficient to define the boundary region 11 by including a specific element constituting the sub-component. For example, it is not necessary to be able to observe the boundary between the boundary region 11 and the region inside it, and a region containing more specific elements than other regions can be arbitrarily defined by elemental analysis or the like and regarded as the boundary region 11. The term "surrounding the outer periphery" means that even if the result of elemental analysis or the like shows that the boundary region 11 does not completely surround the outer periphery of the dielectric particle 10 without gaps, a configuration in which the boundary region 11 is provided intermittently and the like is also included. For example, by complementing the gaps between regions containing more of the specifically detected elements than other regions, the complemented region may also be defined as the boundary region 11. For example, although not limited, the ratio of the region defined by complementation in the boundary region 11 may be 45% or less, or may be 30% or less.

[0021] Adjacent dielectric particles 10 may be in contact or separated, and as shown in Figure 2, a segregation phase 20 may be interposed between the dielectric particles 10. The segregation phase 20 is excluded from the dielectric particles 10 in this embodiment.

[0022] When the dielectric particles 10 have a core-shell structure, the boundary region 11 is located on the outermost surface of the shell 13, not at the boundary 14 between the core 12 and the shell 13. A grain boundary exists between adjacent dielectric particles 10. When the dielectric particles 10 have a core-shell structure, a grain boundary is formed between the shells 13 of adjacent dielectric particles 10. This grain boundary can be considered as the boundary region 11.

[0023] Elemental analysis can identify, or at least estimate, the boundary region 11. For example, the boundary region 11 can be obtained by acquiring elemental mapping images using energy-dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS) and confirming the contrast of the elemental mapping images. Alternatively, in addition to acquiring elemental mapping images, line analysis can be performed to identify the locations where there are differences in the content ratio of specific elements, thereby obtaining the boundary region 11.

[0024] At least one of the dielectric particles 10 enclosed by the boundary region 11 has multiple regions with different content ratios of minor components excluding the specified element. "Content ratio" refers to the ratio when the main component and minor components together are considered to be 100 mol%. The minor components include the specified element and elements other than the specified element. The content ratio of minor components excluding the specified element may change in steps from the outside to the inside of the boundary region 11, or it may change gradually. Multiple regions with different content ratios of minor components can be arbitrarily defined. For example, in cases where the particles can be divided into multiple regions based on clear differences in content ratios by elemental analysis, or when the content ratios change gradually, the boundaries between the regions can be arbitrarily determined based on predetermined content ratios.

[0025] Furthermore, among these multiple regions with different ratios of minor components, there are at least two regions whose crystal orientations are different from each other.

[0026] We will explain the case where the dielectric particles 10 have a core-shell structure as an example, in regions where the crystal orientations are different from each other.

[0027] As shown in Figure 3, the dielectric particle 10 is composed of a core 12 located in the center of the particle and a shell 13 that surrounds all or part of the core 12. When the shell 13 covers part of the core 12, the coverage rate may be 50% or more, preferably 70% or more, and more preferably 90% or more, although this is not particularly limited. In the dielectric particle 10 shown in Figure 3, the entire outer circumference of the core 12 is covered by the shell 13. The core 12 and the shell 13 are in contact. The core 12 is a crystalline portion that is substantially composed of the main component, with no sub-components in solid solution, or with a small amount of sub-components in solid solution. The shell 13 has sub-components in solid solution, and the content ratio of sub-components, excluding specific elements, is higher than that of the core 12. As shown in Figure 3, the dielectric particle 10 is composed of one core 12 and a shell 13 surrounding the core 12, or it may be composed of, for example, multiple cores 12 and a shell 13 that continuously surrounds these cores 12.

[0028] When the dielectric particle 10 has a core-shell structure, the content ratio of minor components, excluding specific elements, differs between the core 12 and the shell 13. Therefore, in a core-shell structure, the "multiple regions with different content ratios of minor components, excluding specific elements" can be considered as the core 12 and the shell 13. Furthermore, the crystal orientation of the core 12 and the crystal orientation of the shell 13 are different from each other.

[0029] The dielectric particle 10 shown in Figure 4 is composed of a core 12 and a shell 13 that surrounds the core 12, similar to Figure 3. However, in Figure 4, the shell 13 is composed of multiple layers: a first shell 13a and a second shell 13b. The first shell 13a is formed to surround the core 12, and the second shell 13b is formed to surround the first shell 13a. The first shell 13a is formed on the inside, in contact with the core 12, and the second shell 13b is formed on the outermost surface side of the shell 13, in contact with the surface of the first shell 13a. The first shell 13a and the second shell 13b are multiple regions with different content ratios of minor components, excluding specific elements. In Figure 4, the multiple regions with different content ratios of minor components, excluding specific elements, consist of three layers: core 12, first shell 13a, and second shell 13b. The crystal orientations of at least one or both of the core 12 and first shell 13a, and the first shell 13a and second shell 13b, which are in contact with each other, are different. The shell 13 can consist of three or more layers. When the shell 13 is composed of multiple layers with different content ratios of minor components, it is preferable that each of the multiple shells 13 is formed to cover the surface of the core 12. This increases the contact area (boundary area) of each shell 13. Since the film thickness of the shell 13 is quite thin, even if the boundary 15 between the first shell 13a and the second shell 13b cannot be clearly determined by elemental analysis, the boundary 15 can be arbitrarily defined based on the results of elemental analysis, etc.

[0030] Furthermore, if, for example, the content ratio of a specific element constituting a minor component is too low, and it is not possible to clearly detect all or part of the boundary region 11 of the dielectric particle 10, and the outer contour of the dielectric particle 10 cannot be clearly captured, then, as shown in Figure 5, for example, if there exists a region C (for example, corresponding to a shell) on a line segment L connecting regions A and B (for example, corresponding to a core) that are substantially composed of the main component, and where the content ratio of the minor component is higher than that of regions A and B, and where the crystal orientation is different from that of regions A and B, then it can be estimated that there is one or more dielectric particles 10 surrounded by boundary regions containing the specific element constituting the minor component, and it can be determined that the dielectric particle 10 has multiple regions with different content ratios of minor components excluding the specific element, and that among the multiple regions, it includes at least two regions with different crystal orientations. Here, the crystal orientations of all regions on line segment L do not need to be different from those of regions A and B; it is sufficient that the crystal orientations of at least some regions on line segment L are different from those of regions A and B.

[0031] Furthermore, because the content ratio of specific elements constituting the minor components is small, and it is difficult to identify the boundary region 11, we attempted to identify the dielectric particles 10 using the method shown in Figure 5. However, if, for example, region A is difficult to identify, it becomes difficult to identify the dielectric particles 10 using the method shown in Figure 5. Even in this case, for example, if a part of the grain boundary can be observed, that area can be considered as the boundary region 11, and regions B and C with different content ratios of minor components as shown in Figure 5 can be identified. By demonstrating that the crystal orientations of regions B and C are different, the dielectric particles 10 can also be identified.

[0032] [Regarding secondary components] The elements constituting the minor components are described below. While not limited to these, the minor components include Si and elements other than Si. Si appears as a specific element in the boundary region 11. Therefore, the boundary region 11 surrounding the dielectric particle 10 can be defined by the detection of Si. The detection of elements other than Si in the boundary region 11 is not excluded. A "specific element" means an element that is detected in greater quantities in the boundary region 11 compared to the interior of the dielectric particle 10, or an element that can be targeted for detection in identifying the boundary region 11. Therefore, by targeting Si for detection, the boundary region 11 can be easily identified. Si may also be detected as an oxide. The presence of Si in the boundary region 11 suggests that the material has been sintered well, and therefore, the insulation resistance can be increased, resulting in excellent insulation properties.

[0033] The minor components also include elements other than Si, and at least two regions with different crystal orientations have different proportions of minor components containing elements other than Si. That is, Si can be used to define the boundary region 11 of the dielectric particles 10, and elements other than Si can be used to define regions with different proportions of minor components.

[0034] The elements other than Si in the minor components are not limited, but include, for example, at least one element from among Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. For example, there are multiple regions with different concentrations of rare earth elements other than Si.

[0035] At least two regions with different content ratios of minor components (excluding specific elements) and different crystal orientations are in contact. "Contact" means contact across a surface, not just a point. By stacking at least two regions with different crystal orientations, the contact area can be increased. For example, in the core 12 and shell 13 described in Figure 3, and in the inner first shell 13a and outer second shell 13b described in Figure 4, at least two regions with different crystal orientations are stacked, allowing for contact over a wide area. Even if it is not possible or difficult to observe whether or not contact is occurring, if regions with different content ratios of minor components exist and the effects of this technology are achieved, those regions can be considered to be in contact.

[0036] In this technology, although not limited to it, at least one of the dielectric particles 10 has a core-shell structure. However, depending on the observed cross-section, even if a dielectric particle 10 has a core-shell structure, there may be dielectric particles 10 in which only the shell 13 is visible, or the boundary region 11 between contacting dielectric particles 10 cannot be clearly defined by elemental analysis. In other words, not all dielectric particles that have all of the following characteristics appear in the observed cross-section: surrounded by a boundary region containing specific elements that constitute the subcomponents, having multiple regions with different subcomponent content ratios, and containing at least two regions with different crystal orientations. Furthermore, there are dielectric particles 10 that do not have a core-shell structure at all, and dielectric particles 10 whose subcomponent content ratios and crystal orientations cannot be properly analyzed. Therefore, it is stipulated that it is sufficient for at least one dielectric particle 10 to be observed. Even if it is not possible to clearly observe that a dielectric particle 10 is surrounded by a boundary region 11, for example, the observation method described in Figure 5 can be used to determine that the dielectric particle 10 has multiple regions with different subcomponent content ratios, and that among these multiple regions, at least two regions have different crystal orientations.

[0037] The crystalline structure of the dielectric particles 10 in this technology includes, for example, a region having a perovskite-type structure. In this technology, ceramic materials having a perovskite structure can be included as the main component. Examples of ceramic materials having a perovskite structure include BaTiO3 (barium titanate), as well as (Ba,Ca)TiO3, (Ba,Ca)(Ti,Zr)O3, (Sr,Ca)(Ti,Zr)O3, (Ba,Sr,Ca)(Ti,Zr)O3, BaZrO3, and CaZrO3.

[0038] In one embodiment of this technology, the main component of the dielectric particle 10 is general formula A m It is represented as BO3. Here, A is one element selected from Ca, Sr, and Ba or a combination thereof, B is one element selected from Ti and Zr or a combination thereof, and m is between 0.9 and 1.4. For example, if the dielectric particle 10 has a perovskite structure, the ratio of A to B may deviate from the stoichiometric composition. Note that the main component of the dielectric particle 10 is given by the general formula A. m Even when represented as BO3, the main component of the dielectric particle 10 does not necessarily have to have a perovskite structure; for example, it may have an ilmenite structure, and furthermore, the ratio of A to B may deviate from the stoichiometric composition. As described above, higher reliability can be obtained by specifically defining the minor components, the main components, or both the minor and main components. While it is desirable that the dielectric particles 10 consist only of the main and minor components, they may also contain trace amounts of components other than the main and minor components, i.e., impurities. The content ratio of impurities is not particularly limited, but it should be smaller than the main and minor components, for example, 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less relative to the total dielectric particles.

[0039] While not limited to these, the boundary between at least two regions with different crystal orientations includes a curve. Here, the lines appearing in the cross-sectional views shown in Figures 3 to 5 represent the appearance of a plane as a line when a three-dimensional dielectric particle 10 is cut. A "curve" is a line that is not a straight line, and includes curved lines and lines that are straight but bent midway. In the core-shell structure shown in Figures 3 to 5, the boundary 14 between the core 12 and the shell 13, and the boundary 15 between the first shell 13a and the second shell 13b appear as curves.

[0040] Thus, if the boundary between at least two regions with different crystal orientations contains a curve, the two regions can be considered not to be twinned. Generally, the twinning interface is a straight line. Therefore, the boundary between at least two regions with different crystal orientations in this technology is not a twinning interface.

[0041] Observation using a high-resolution transmission electron microscope (HR-TEM), or crystal orientation analysis by electron diffraction using a transmission electron microscope (TEM), allows observation of at least two regions with different crystal orientations. While there are several methods classified as electron diffraction, any method that can appropriately analyze the crystal orientation of the target region may be selected. For example, nanobeam electron diffraction (NBED) or limited-field electron diffraction (SAED) may be used. Alternatively, an orientation map may be obtained using electron backscatter diffraction (EBSD). Furthermore, depending on the size of the dielectric particles 10, a scanning electron microscope (SEM) may be used instead of a TEM, and methods such as EBSD can be employed.

[0042] For example, the dielectric layer 2 can be cut at an arbitrary position, the cut cross-section can be observed with a scanning transmission electron microscope (STEM), and elemental mapping can be obtained using EDS. This allows us to obtain the boundary region 11 of the dielectric particles 10, and if the dielectric particles 10 have a core-shell structure, we can distinguish between the core 12 and the shell 13.

[0043] Furthermore, observation using HR-TEM or crystal orientation analysis by electron diffraction can reveal, for example, that the crystal orientation of the core 12 and the crystal orientation of the shell 13 are different from each other. For example, using the EBSD orientation map, it can be observed that the crystal orientations of the core 12 and the shell 13 are different, as shown in the schematic diagram in Figure 3.

[0044] The region containing the dielectric particle 10 and its crystal structure can be confirmed during the crystal orientation analysis described above. While known methods can be used to identify the crystal structure, for example, the electron diffraction pattern of the crystal structure assumed from the principal components can be simulated beforehand and then compared with the electron diffraction pattern actually obtained by NBED or SAED to identify the crystal structure of the relevant region. Alternatively, instead of obtaining an electron diffraction pattern, a pseudo-electron diffraction pattern can be obtained by performing a fast Fourier transform on part or all of the lattice image obtained by HR-TEM observation.

[0045] [Regarding the effects] According to this technology, at least one of the dielectric particles 10 contained in the dielectric layer 2 is surrounded by a boundary region 11 containing a specific element that constitutes a minor component, and has multiple regions with different content ratios of minor components excluding the specific element, and among these multiple regions, at least two regions have different crystal orientations. This allows oxygen vacancies to be trapped by disrupting the atomic arrangement at the boundary of regions with different crystal orientations, thereby extending the high-temperature load life and achieving high reliability. The difference in crystal orientation between the at least two regions with different crystal orientations is not particularly limited, but may be 5° or more, 10° or more, or 15° or more.

[0046] In this technology, at least two regions with different crystal orientations are in contact, allowing for more effective trapping of oxygen vacancies and higher reliability. For example, as shown in Figure 3, the dielectric particle 10 has a core 12 consisting of a continuous region with a constant crystal orientation and a shell 13 consisting of a continuous region with a constant crystal orientation, where the core 12 and shell 13 have different crystal orientations. The core 12 and shell 13 are in contact at a surface. Alternatively, as shown in Figure 4, the shell 13 has a first shell 13a consisting of a continuous region with a constant crystal orientation and a second shell 13b consisting of a continuous region with a constant crystal orientation, where the crystal orientations of the first shell 13a and the second shell 13b are different. The first shell 13a is formed on the inside, close to the core 12, and the second shell 13b is on the outside of the shell 13 and is in surface contact with the first shell 13a.

[0047] It is possible that no dielectric particles 10 satisfying the configuration of this technology may be found in the observed cross-section. In such cases, it is necessary to consider whether observation is possible in a different cross-section. It is desirable that multiple dielectric particles 10 satisfying the configuration of this technology be confirmed in the observed cross-section, but one is sufficient. However, it is desirable that at least one dielectric particle 10 satisfying the configuration of this technology be observed in each of the multiple cross-sections. As mentioned above, methods such as HRTEM and electron diffraction are used to determine the crystal orientation, but these methods can only determine the crystal orientation of particles whose low-index plane is facing the observation direction. Therefore, if even one dielectric particle 10 satisfying the configuration of this technology is confirmed, it can be inferred that a certain amount of dielectric particles 10 satisfying the configuration of this technology are also included among the particles whose crystal orientation could not be determined. Furthermore, when a voltage is applied to electronic components and multilayer ceramic capacitors at high temperatures, oxygen vacancies contained in the dielectric move from the positive electrode side to the negative electrode side and accumulate, reducing the insulating properties and leading to failure. Therefore, if the movement of oxygen vacancies can be inhibited at some point along their migration path, the high-temperature load life can be improved. Thus, even if only a portion of the dielectric particles 10 satisfy the configuration of this technology, it will still have the effect of improving the high-temperature load life.

[0048] In this technology, the boundary between at least two regions with different crystal orientations is not a twinning interface. For example, the boundary 14 between the core 12 and the shell 13 shown in Figure 3 is a curved surface and not a twinning interface. Alternatively, the boundary 15 between the first shell 13a and the second shell 13b shown in Figure 4 is a curved surface and not a twinning interface. Because the boundary between at least two regions with different crystal orientations is not a twinning interface with minimal atomic arrangement disorder, oxygen vacancies can be strongly trapped, resulting in high reliability.

[0049] In this technology, the dielectric particles 10 include, but are not limited to, minor components, which include Si and at least one element from among Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. The boundary region 11 surrounds the dielectric particles 10 with Si as the specified element, and at least two regions with different crystal orientations have different content ratios of minor components, which include at least one element other than Si from among Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements. Thus, the boundary region 11 can be identified, or at least estimated, by detecting Si through elemental analysis. By detecting Si, excellent sinterability and high insulation resistance can be obtained. Furthermore, by using the concentration of an element other than Si used to define the boundary region 11 as a standard, multiple regions with different content ratios of minor components can be appropriately and easily selected. In this technology, at least two regions with different crystal orientations may have lattice defects such as plane defects between them.

[0050] [Manufacturing method for multilayer ceramic capacitors] Below, a representative example of a manufacturing method for the multilayer ceramic capacitor 1 shown in Figure 1 will be described. The multilayer ceramic capacitor 1 of this embodiment can be manufactured by creating a green chip using a paste printing method or a sheet method, firing it, and then forming a pair of external electrodes 5 on the resulting element body 4.

[0051] First, the main component raw materials and the secondary component raw materials are prepared as dielectric materials. These raw materials can be oxides or mixtures thereof of the above-mentioned components, or composite oxides. Alternatively, various compounds that become oxides or composite oxides of the above-mentioned components upon firing, such as carbonates, oxalates, nitrates, hydroxides, organometallic compounds, etc., can be appropriately selected and mixed for use.

[0052] Next, the main component raw materials are wet-mixed using a ball mill or the like, and the resulting mixed powder is dried and then calcined under predetermined conditions to obtain the main component powder. The mixing of the raw materials is not particularly limited, but they are thoroughly mixed by a wet method for about 20 hours and then dried. The calcination conditions are not particularly limited, but the calcination temperature is 900°C to 1350°C, preferably 1000°C to 1350°C, the holding time is preferably 1 to 10 hours, the heating rate to the calcination temperature is about 10°C / hour to 2000°C / hour, and the cooling rate after the holding time is 200°C / hour or more, preferably 300°C / hour or more, more preferably 400°C / hour or more. The main component powder after calcination may be pulverized using a ball mill or the like as needed. Alternatively, instead of obtaining the main component powder from the main component raw materials by the above process, a predetermined commercially available product may be used as the main component powder.

[0053] Next, the main component powder, the secondary component raw materials, and additional main component raw materials as needed are wet-mixed using a mixer such as a ball mill to obtain dielectric raw materials. Furthermore, the dielectric raw materials are made into a paint to prepare a paste for the dielectric layer. The dielectric layer paste may be an organic paint made by kneading the dielectric raw materials with an organic vehicle, or it may be a water-based paint.

[0054] An organic vehicle is a binder dissolved in an organic solvent. The binder used in the organic vehicle is not particularly limited and can be appropriately selected from various common binders such as ethylcellulose and polyvinyl butyral. The organic solvent used is also not particularly limited and can be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene, depending on the method of use, such as printing or sheet processing.

[0055] The paste for the internal electrode layer is prepared by kneading a conductive material made of the various conductive metals and alloys described above, or various oxides, organometallic compounds, resinates, etc. that become the conductive material after firing, with the organic vehicle described above. The paste for the internal electrode layer may also contain a co-material. The co-material is not particularly limited, but it is preferable that it has a composition similar to that of the main component.

[0056] Next, using the pastes described above, green chips that will become the element body 4 after firing are manufactured. Green chips can be manufactured using various printing methods or sheet manufacturing methods.

[0057] For example, when manufacturing green chips using the sheet method, first, a dielectric paste is applied to a carrier film such as PET to form a sheet, which is then dried as needed to obtain a green sheet. Then, a paste for internal electrodes is applied to the green sheet in a predetermined pattern using various printing methods such as screen printing. After laminating multiple layers, a mother laminate is obtained by pressing in the lamination direction. At this time, the green sheets are laminated so that only dielectric layers are located on the top and bottom surfaces of the mother laminate in the lamination direction. Finally, the mother laminate obtained in the above process is cut by dicing or press cutting to obtain multiple green chips.

[0058] Next, the green chips are subjected to a binder removal treatment. The conditions for the binder removal treatment are preferably a heating rate of 5°C / hour to 300°C / hour, a holding temperature of preferably 180°C to 900°C, and a temperature holding time of preferably 0.5 hours to 48 hours. The atmosphere for the binder removal treatment is either an air atmosphere or a reducing atmosphere.

[0059] After binder removal, the green chips are fired. The atmosphere during green chip firing should be appropriately determined according to the type of conductive material in the paste for the internal electrode layer, but when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen partial pressure in the firing atmosphere should be 10 -14 MPa~10 -10It is preferable to use MPa. If the oxygen partial pressure is below the above range, the conductive material in the internal electrode layer may undergo abnormal sintering and break. Also, if the oxygen partial pressure exceeds the above range, the internal electrode layer tends to oxidize.

[0060] Furthermore, the holding temperature during firing is preferably 1000°C to 1400°C, more preferably 1100°C to 1360°C. If the holding temperature is below the above range, densification will be insufficient, and if it exceeds the range, abnormal sintering of the internal electrode layer may cause breakage of the electrodes, deterioration of the capacitance temperature characteristics due to diffusion of the internal electrode layer constituent material, and reduction of the dielectric ceramic composition.

[0061] Other firing conditions include a heating rate of preferably 50°C / hour to 2000°C / hour, more preferably 200°C / hour to 300°C / hour, a temperature holding time of preferably 0.5 hours to 8 hours, more preferably 1 hour to 3 hours, and a cooling rate of preferably 50°C / hour to 2000°C / hour, more preferably 200°C / hour to 300°C / hour. Furthermore, a reducing atmosphere is preferred for the firing atmosphere, and as the atmosphere gas, for example, a humidified mixture of N2 and H2 can be used.

[0062] After firing in a reducing atmosphere, it is preferable to anneal the capacitor element body. Annealing is a process to re-oxidize the dielectric layer, which significantly extends the lifespan and improves reliability.

[0063] The partial pressure of oxygen in the annealing atmosphere is 10 -9 MPa~10 -5 It is preferable to use MPa. If the oxygen partial pressure is below the above range, re-oxidation of the dielectric layer is difficult, and if it exceeds the above range, oxidation of the internal electrode layer tends to progress.

[0064] The holding temperature during annealing is preferably 1100°C or lower, and particularly preferably between 500°C and 1100°C. If the holding temperature is below this range, the oxidation of the dielectric layer will be insufficient, resulting in low insulation resistance and a shortened high-temperature load life. On the other hand, if the holding temperature exceeds this range, not only will the internal electrode layer oxidize and the capacitance decrease, but the internal electrode layer will also react with the dielectric substrate, leading to deterioration of capacitance-temperature characteristics, a decrease in insulation resistance, and a shortened high-temperature load life. Note that annealing may consist only of a heating process and a cooling process. That is, the temperature holding time may be zero. In this case, the holding temperature is synonymous with the maximum temperature.

[0065] Other annealing conditions include a temperature holding time of preferably 0 to 20 hours, more preferably 2 to 10 hours, and a cooling rate of preferably 50°C / hour to 500°C / hour, more preferably 100°C / hour to 300°C / hour. Furthermore, it is preferable to use, for example, N2 or N2+H2O gas as the annealing atmosphere gas.

[0066] Furthermore, the debinding process, firing, and annealing may be performed consecutively or independently.

[0067] The element body 4 is obtained by firing and annealing through the process described above. The element body 4 obtained as described above is then subjected to end-face polishing, for example by barrel polishing or sandblasting, and an external electrode paste is applied and fired to form the external electrode 5. Then, if necessary, a coating layer is formed on the surface of the external electrode 5 by plating or the like.

[0068] The multilayer ceramic capacitors of this embodiment, manufactured in this manner, are mounted on printed circuit boards or the like by soldering and used in various electronic devices.

[0069] In this technology, the main component powder is pre-treated before mixing it with the secondary component raw materials. The pre-treatment is performed to form at least two regions with different ratios of secondary components so that their crystal orientations are different from each other. The method of pre-treatment is not limited as long as it is possible to make the crystal orientations different.

[0070] In this technology, pulsed laser irradiation can be used as an example of pretreatment. Specifically, a pulsed laser is irradiated onto the main component powder. This allows the surface of the main component powder to be instantaneously dissolved and solidified. At this time, it is assumed that the surface of the main component powder is amorphous. By mixing the pretreated main component powder with the secondary component raw material and performing firing, a region with a high content of secondary components is formed on the surface of the main component powder. Because the surface of the main component powder has an amorphous structure, the region with a high content of secondary components can be formed with a different crystal orientation from the interior of the main component powder.

[0071] Any method other than pulsed laser irradiation is acceptable, as long as it applies energy to the surface of the main component powder, for example, by causing a phase change or altering the surface state.

[0072] In this technology, the dielectric can be applied to the multilayer ceramic capacitor 1 shown in Figure 1, but it is not limited to this and may be applied to other electronic components. For example, the electronic components related to this technology may be filters, diplexers, resonators, oscillators, antennas, etc., in addition to capacitors. [Examples]

[0073] The details of this technology will be described in more detail below with reference to the examples and comparative examples. However, this technology is not limited to the examples described below.

[0074] <Manufacturing conditions common to the examples and comparative examples> Barium carbonate (BaCO3), calcium carbonate (CaCO3), strontium carbonate (SrCO3), titanium dioxide (TiO2), and zirconium oxide (ZrO2) were prepared as the main component raw materials for the main component powder. Oxides of Si, Mg, Al, V, Mn, Nb, Mo, Y, Gd, Tb, Dy, Ho, and Yb were prepared as auxiliary raw materials.

[0075] The main component raw materials were weighed so that the composition of the main components after calcination would be as shown in Table 1. After weighing, each raw material was mixed. Mixing was performed by wet mixing and stirring in a ball mill. The mixture after wet mixing and stirring was dried. After drying, it was calcined in air at 1100°C to 1300°C, and then wet-ground in a ball mill to obtain the main component powder.

[0076] Next, the main component powder and secondary component raw materials were weighed so that the composition after firing would be as shown in Table 1. Here, the metal ion concentration of each secondary component was set to 0.1 mol% to 1.0 mol% relative to the main component. The weighed main component powder and secondary component raw materials were mixed with an organic vehicle to form a paste, which was used to obtain a dielectric layer paste. Using the dielectric layer paste, a green sheet was formed on a PET film. Then, using a paste for the internal electrode layer obtained by mixing Ni powder and an organic vehicle, the internal electrode layer was printed on this sheet in a predetermined pattern. After that, the sheet was peeled from the PET film to produce a green sheet with an internal electrode layer. Next, multiple green sheets with internal electrode layers were laminated and pressure-bonded to obtain a green laminate. On the top and bottom surfaces of the green laminate in the lamination direction, a protective green sheet without the printed internal electrode layer was laminated. By cutting this green laminate to a predetermined size, green chips were obtained.

[0077] Next, the obtained green chip was subjected to debinding, firing, and annealing to obtain a sintered body serving as the element body. After polishing the end face of the obtained sintered body by sandblasting, an In-Ga alloy was applied to form an external electrode. Here, the conditions for the debinding process were a heating rate of 30 °C / hour, a holding temperature of 260 °C, a temperature holding time of 8 hours, and an atmosphere of air. The firing conditions were a holding temperature of 1200 °C to 1300 °C, a temperature holding time of 2 hours, a cooling rate of 300 °C / hour or more, a humidified N2 + H2 mixed gas as the atmosphere gas, and an oxygen partial pressure of 1.0×10 -13 MPa to 1.0×10 -12 MPa. The annealing conditions were a holding temperature of 1050 °C, a holding time of 2 hours, a humidified N2 gas as the atmosphere gas, and an oxygen partial pressure of 1.0×10 -9 MPa or more. The average dimensions of the obtained element body were 2.0 mm × 1.2 mm × 0.6 mm, the number of stacked dielectric layers sandwiched between the internal electrode layers was 5, the average thickness of the dielectric layer was 5 μm, and the average thickness of the internal electrode layer was 1.5 μm.

[0078] <Measurement of High-Temperature Load Life> For the capacitor sample obtained above, the application state of the DC voltage was maintained under an electric field of 50 V / μm at 200 °C, and the high-temperature load life was evaluated by measuring the insulation degradation time of the capacitor sample. In this example, the time until the insulation resistance dropped by one digit from the start of voltage application was defined as the failure time.

[0079] In this experiment, the above evaluation was performed on 20 capacitor samples, and the mean time to failure was calculated by Weibull analysis.

[0080] The cross-section of the dielectric layer 2 along the stacking direction of the capacitor sample was polished, and a thin section sample with a thickness of approximately 50 nm was prepared using focused ion beam (FIB). A scanning transmission electron microscope (STEM) was used to observe a region of 1 μm to 5 μm square at an acceleration voltage of 200 kV. An elemental map of Si and other minor components was then obtained using the attached EDS device, confirming the existence of dielectric particles 10 surrounded by boundary regions containing Si, and having multiple regions with different content ratios of minor components other than Si. The crystal structure and crystal orientation were then identified and evaluated for each of the multiple regions with different content ratios of minor components using electron diffraction.

[0081] <Differences in manufacturing conditions between the examples and comparative examples> In the example, pulsed laser irradiation was performed as a pretreatment of the main component powder, but in the comparative example, pulsed laser irradiation was not performed.

[0082] While not limited to pulsed lasers, this experiment used an Nd:YAG laser with a wavelength of 1064 nm. The laser output was set to 1 W and the pulse frequency to 1000 Hz. Table 1 below shows the evaluation results of the mean failure time for Examples 1 to 14 and Comparative Examples 1 to 14.

[0083] [Table 1]

[0084] In Table 1, examples and comparative examples with matching sample numbers correspond to each other (i.e., for example, Example 1 corresponds to Comparative Example 1, Example 2 corresponds to Comparative Example 2, etc.), and the mean failure time for each example was obtained with the mean failure time of the corresponding comparative example set to 100.

[0085] Table 1, which shows the "presence or absence of regions with different crystal orientations," indicates the results of observing whether at least one dielectric particle observed in each sample had a different crystal orientation in a region with a different content ratio of subcomponents other than Si, as determined by electron diffraction. The "presence or absence of regions with different crystal orientations" tended to correlate with the mean time of failure. In other words, it was found that there was a clear difference in mean time of failure between the examples and the comparative examples. This suggests that in the examples, the surface of the main component powder becomes amorphous during the manufacturing process, and regions with a high content ratio of subcomponents are formed, having a different crystal orientation from the interior of the main component powder. Furthermore, all regions with different crystal orientations observed in the examples had a perovskite-type structure. In addition, it was observed that the boundaries of the regions with different crystal orientations observed in the examples were curved, not twinning interfaces. [Explanation of symbols]

[0086] 1... Multilayer ceramic capacitor, 2... Dielectric layer, 3... Internal electrode layer, 4... Capacitor element body, 5... External electrode, 10... Dielectric particles, 11... Boundary region, 12... Core, 13... Shell, 13a... First shell, 13b... Second shell, 14... Boundary, 15... Boundary, 20... Segregation phase.

Claims

1. Contains dielectric particles, At least one of the dielectric particles comprises a main component and a minor component, At least one of the dielectric particles is surrounded by a boundary region containing a specific element that constitutes the subcomponent, A dielectric in which at least one of the dielectric particles surrounded by the boundary region has a plurality of regions with different content ratios of the minor components excluding the specific element, and of the plurality of regions, at least two of the regions have different crystal orientations.

2. The aforementioned minor component includes Si and elements other than Si. The boundary region surrounds at least one of the dielectric particles with Si as the specific element. The dielectric according to claim 1, wherein at least two of the regions having different crystal orientations have different content ratios of the subcomponents containing elements other than Si.

3. The dielectric according to claim 2, wherein the aforementioned minor component comprises Si and at least one element selected from Mg, Al, V, Cr, Mn, Nb, Mo, Sn, Hf, Ta, W, and rare earth elements.

4. The dielectric according to claim 1 or claim 2, wherein at least two of the regions having different crystal orientations are in contact with each other.

5. At least one of the dielectric particles has a core-shell structure having a core and a shell that surrounds and covers the core. The dielectric according to claim 1 or claim 2, wherein at least the crystal orientation of the core and the crystal orientation of the shell are different from each other.

6. The dielectric according to claim 1 or claim 2, wherein at least one of the dielectric particles includes a region having a perovskite-type structure.

7. At least one main component of the dielectric particle is general formula A ｍ BO ３ It is represented as, A is one element selected from Ca, Sr, and Ba, or a combination thereof. B is one element selected from Ti and Zr, or a combination thereof. The dielectric according to claim 1 or claim 2, wherein m is 0.9 or more and 1.4 or less.

8. A dielectric layer comprising the dielectric described in claim 1 or claim 2, Electrodes and, including, Multilayer ceramic capacitor.

9. A dielectric material comprising the dielectric material described in claim 1 or claim 2, Electronic components.

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