Multilayer ceramic electronic component and dielectric ceramic composition

Abstract

To provide a multilayer ceramic electronic component and a dielectric ceramic composition capable of suppressing a change in electrostatic capacity due to a firing temperature.SOLUTION: A multilayer ceramic electronic component includes a plurality of internal electrode layers facing each other, a dielectric layer sandwiched between the plurality of internal electrode layers and comprising a dielectric particle 41 having a perovskite structure represented by a general formula ABO3, including a core portion 411, a shell portion 412 covering the core portion 411 and containing a rare earth element, and an oxide 42 segregated in the shell portion 412 and having a higher concentration of the rare earth element than the shell portion 412, and an external electrode electrically connected to the plurality of internal electrode layers.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In high-frequency communication systems typified by mobile phones, multilayer ceramic electronic components such as multilayer ceramic capacitors (MLCCs) are used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the use of multilayer ceramic electronic components has also expanded in electronic circuits related to human life, such as in-vehicle electronic control devices. High reliability is required, and at the same time, higher mass productivity is required from the perspective of supply volume.

[0006] For the dielectric ceramic composition used in the dielectric layer of a multilayer ceramic electronic component, a sintered body having a core-shell structure in which barium titanate forms the core part and a shell part in which various additives are solid-solved surrounds the core part is utilized. By adopting this structure, it is possible to shift to a lower temperature in the shell part the manifestation of a large capacitance near the Curie temperature where a change occurs from the ferroelectric phase of barium titanate existing near 125°C to the paraelectric phase due to the effects of various additives. Therefore, in the temperature range for practical use near room temperature, it is possible to design to increase the capacitance further.

[0007] The core-shell structure is considered to be formed by solid-soluting various additives in barium titanate. The core-shell structure is considered to be formed, for example, in a firing temperature range of 1000°C to 1400°C, by the reaction of components added as various additives with barium titanate particles as the main component. Generally, as the firing temperature increases, various additives are solid-solved and the shell part becomes thicker. Therefore, in order to keep the capacitance of the multilayer ceramic electronic component within the required range, it is necessary to precisely control the solid solution of various additives.

[0008] For example, Patent Documents 1 and 2 disclose a dielectric ceramic composition, a dielectric material, and a multilayer ceramic capacitor containing the same, which contain a barium titanate-based main component and a sub-component, and in which the relative intensity of a pyrochlore phase containing a rare earth element is controlled in XRD analysis after sintering.

[0009] In recent years, since the usage applications of dielectric ceramic compositions and multilayer ceramic electronic components have been expanding, higher mass productivity has been demanded. For this purpose, it is necessary to suppress the change in capacitance due to the firing temperature and reduce the fluctuation of capacitance due to temperature.

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide a multilayer ceramic electronic component and a dielectric ceramic composition capable of suppressing the change in capacitance due to the firing temperature.

Means for Solving the Problems

[0011] The multilayer ceramic electronic component according to the present invention includes a plurality of internal electrode layers facing each other, a core portion provided between the plurality of internal electrode layers, a shell portion covering the core portion and containing a rare earth element, and an oxide that segregates inside the shell portion and has a higher concentration of the rare earth element than the shell portion, and includes a dielectric layer containing dielectric particles having a perovskite structure represented by the general formula ABO3, and an external electrode electrically connected to the plurality of internal electrode layers.

[0012] In the above multilayer ceramic electronic component, the oxide may contain a pyrochlore phase.

[0013] In the above multilayer ceramic electronic component, barium may be included in the A site of the perovskite structure, and the element included in the B site of the perovskite structure may be at least one of titanium and zirconium.

[0014] In the above multilayer ceramic electronic component, the rare earth element may be composed of at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, and erbium.

[0015] In the above multilayer ceramic electronic component, the shell portion may have a ratio of rare earth element to titanium of 0.02 or more and less than 0.20.

[0016] In the above multilayer ceramic electronic component, the oxide may have a ratio of rare earth element to titanium of 0.20 or more.

[0017] In the above multilayer ceramic electronic component, the oxide may be encapsulated inside the shell portion.

[0018] In the above multilayer ceramic electronic component, the oxide may be in contact with a part of the core portion.

[0019] In the above multilayer ceramic electronic component, the oxide may be in contact with a part of the grain boundary of the dielectric particles.

[0020] In the above multilayer ceramic electronic component, the oxide may extend from a part of the core portion to a part of the grain boundary of the dielectric particles.

[0021] In the above multilayer ceramic electronic component, a plurality of the oxides may be present in the shell portion while being separated from each other.

[0022] In the above multilayer ceramic electronic component, a plurality of the dielectric particles are adjacent to each other via grain boundaries, and the oxide may not connect the core portions of the plurality of dielectric particles.

[0023] In the above multilayer ceramic electronic component, the oxide may not be in contact with the core portion.

[0024] In the above multilayer ceramic electronic component, the maximum particle size of the dielectric particles may be 2 μm or less.

[0025] In the above multilayer ceramic electronic component, the shell portion may contain magnesium and manganese.

[0026] The dielectric ceramic composition according to the present invention has a core portion, a shell portion covering the core portion and containing a rare earth element, and an oxide having a higher concentration of the rare earth element than the shell portion inside the shell portion, and contains dielectric particles having a perovskite structure represented by the general formula ABO3.

Advantages of the Invention

[0027] According to the present invention, it is possible to provide a multilayer ceramic electronic component and a dielectric ceramic composition capable of suppressing a change in capacitance due to a firing temperature.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0029] Hereinafter, embodiments will be described with reference to the drawings.

[0030] (First Embodiment) The dielectric ceramic composition according to the first embodiment is a polycrystalline ceramic containing crystal particles having a perovskite structure represented by the general formula ABO3, as illustrated in FIG. 1. Among these polycrystalline ceramics, at least one is a dielectric particle 41 having a core-shell structure.

[0031] The dielectric particles 41 include a substantially spherical core portion 411 and a shell portion 412 that covers and surrounds the core portion 411. The core portion 411 is a crystal portion in which the additive compound is not solid-solved or the solid-solution amount of the additive compound is small. The shell portion 412 is a crystal portion in which the additive compound is solid-solved and has an additive compound concentration higher than the additive compound concentration of the core portion 411. In the present embodiment, the shell portion 412 contains a rare earth element R. The rare earth element R is not particularly limited, and examples thereof include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), and the like. The element concentration of the rare earth element R in the shell portion 412 is higher than the element concentration of the rare earth element in the core portion 411.

[0032] In the shell portion 412, an oxide 42 in which the concentration of the rare earth element R is higher than that of the shell portion 412 is segregated. The number of the oxides 42 is not particularly limited. However, in the cross section, the cross-sectional area of the shell portion 412 is wider than the total cross-sectional area of each oxide 42.

[0033] The dielectric ceramic composition according to the present embodiment includes the dielectric particles 41 and the oxide 42, so that it has high insulation and can suppress fluctuations in capacitance due to the firing temperature.

[0034] For example, when observing in a field of view where 100 or more dielectric particles 41 and oxides 42 are confirmed in total in the cross section of the dielectric ceramic composition, the area ratio of the dielectric particles 41 is 95% or more and 99.95% or less, and the area ratio of the oxides 42 is 0.01% or more and 5% or less.

[0035] The crystal particles having a perovskite structure, which are the main component of the dielectric particles 41, have a unit cell as exemplified in FIG. 2. In this unit cell, there are an A site located at the lattice vertex, an O site located at the lattice face center, and a B site located within an octahedron having the O site as its vertex, respectively. In the perovskite structure, alkaline earth metals that can take divalent cations such as barium (Ba), strontium (Sr), and calcium (Ca) are coordinated at the A site, and metal atoms that can take tetravalent cations such as hafnium (Hf), zirconium (Zr), and titanium (Ti) are coordinated at the B site.

[0036] The perovskite structure allows a composition formula that deviates from the stoichiometric composition. That is, the ratio of the A-site element to the B-site element does not necessarily have to be 1:1, and defects may be generated within the range that can maintain the perovskite structure. Also, defects may be generated in oxygen. For example, when the composition formula is A α BO 3-β compositions in the range of 0.98 ≦ α ≦ 1.01 and 0 ≦ β ≦ 0.20 can be tolerated.

[0037] However, for example, when oxygen defects are generated, the resistivity may decrease, ionic conductivity may be exhibited, the electrical life may decrease when used as a multilayer ceramic capacitor, the dielectric loss may increase, and it may not be usable in practice. Therefore, for the dielectric particles 41 having a perovskite structure, if necessary, at least one of the first transition elements scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn) may be included. Thereby, it is possible to improve the resistivity, enhance the electrical long life, and reduce the dielectric loss with respect to the capacitance.

[0038] In addition, the dielectric particles 41 may contain, if necessary, at least one of yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), and silver (Ag), which are second transition elements. This makes it possible to improve the resistivity, enhance the electrical long life, and reduce the dielectric loss with respect to the capacitance.

[0039] In addition, the dielectric particles 41 may contain, if necessary, at least one of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au), which are third transition elements. This makes it possible to improve the resistivity, enhance the electrical long life, and reduce the dielectric loss with respect to the capacitance.

[0040] It is preferable that an additive containing a rare earth element R such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and holmium (Ho) is added to the dielectric ceramic composition. Also, it is preferable that an additive containing titanium is added to the dielectric ceramic composition so that the element ratio (ratio of the number of elements) of titanium to the rare earth element R is 1 or more. Compared with the case where an additive containing titanium is not added, the solid solution reaction with respect to the barium titanate crystal particles is relatively suppressed. Due to this effect, it becomes possible to suppress the change rate of the capacitance due to the change in the firing temperature while achieving firing in a shorter time and obtain high mass productivity.

[0041] Examples of the additive containing the rare earth element R include lanthanum oxide (La2O3), cerium oxide (Ce2O3), praseodymium oxide (Pr2O3), neodymium oxide (Nd2O3), promethium oxide (Pm2O3), samarium oxide (Sm2O3), europium oxide (Eu2O3), gadolinium oxide (Gd2O3), terbium oxide (Tb2O3), dysprosium oxide (Dy2O3), holmium oxide (Ho2O3), etc., which are preferred.

[0042] Examples of the additive containing titanium include titanium oxide as a preferred example, but titanium hydroxide (Ti(OH)4), titanium chloride (TiCl4), titanium carbide (TiC), titanium sulfide (TiS2), etc. can also be used.

[0043] In addition, La2Ti2O7, Ce2Ti2O7, Pr2Ti2O7, Nd2Ti2O7, Pm2Ti2O7, Sm2Ti2O7, Eu2Ti2O7, Gd2Ti2O7, Tb2Ti2O7, Dy2Ti2O7, Ho2Ti2O7, etc. can also be used as the additive containing the rare earth element R and titanium.

[0044] In the dielectric ceramic composition, in addition to the addition of the rare earth element R, it is preferable to add 0.2 mol or more and 5.0 mol or less in terms of manganese oxide (MnO) conversion with respect to 100 mol of barium titanate so that the Mn / Ti element ratio z, which is the ratio of the manganese element to the titanium content, satisfies 0.002 ≤ z ≤ 0.05.

[0045] By the way, in the core-shell structure, generally, as the firing temperature increases, more various additives dissolve in the crystal particles composed of barium titanate, and the shell part tends to become thicker. In the shell part, the large capacitance region near the Curie temperature of barium titanate, which is around 125°C, approaches room temperature. Thereby, the capacitance in the temperature range practical near room temperature changes greatly depending on the thickness of the shell part. Therefore, as an example, in order to keep the capacitance of the multilayer ceramic capacitor within the required range, it is preferable to precisely control the firing temperature.

[0046] For example, the dielectric porcelain composition according to the present embodiment is obtained by maintaining the temperature at 900°C to 1100°C and then firing at 1150°C to 1300°C, and performing a rapid temperature increase with a temperature increase rate in the firing process of 3000°C / h to 10000°C / h.

[0047] The dielectric particles 41 having a core-shell structure in which a shell portion 412 containing a rare earth element is formed have a different generation process from the conventional core-shell structure. Specifically, not only the solid solution of the rare earth element R into the crystal particles made of barium titanate, but also the added rare earth element R and titanium form a compound such as R2Ti2O7 having a pyrochlore structure or a perovskite slab structure, and then react with the surface of the barium titanate crystal particles to form the shell portion 412 in the form of a composite perovskite compound such as R(Ti,Mn)O3. Therefore, an excessive solid solution reaction into the shell portion 412 such as the rare earth element R can be suppressed, and the change rate of the capacitance due to the change in the firing temperature can be suppressed. As a trace of the generation process of such a shell portion 412, an oxide region having a higher concentration of the rare earth element R than the shell portion is generated. The generation reaction of R2Ti2O7 is carried out between 900°C and 1100°C.

[0048] In order to promote this shell generation reaction, it is desirable that the rare earth element R is an element that easily solidifies into the A site of ABO3. Specifically, it is preferably a rare earth element lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho) having a larger ionic radius than erbium (Er).

[0049] On the one hand, when using a rare earth element R (erbium, thulium, ytterbium, lutetium) with an ionic radius smaller than that of holmium, a compound R2Ti2O7 with a pyrochlore structure is formed. However, the shell formation reaction between R2Ti2O7 and barium titanate crystal particles does not proceed sufficiently, and there is a risk that the cores of multiple particles and the oxide regions will come into electrical contact. As a result, the resistivity decreases, which may render it unsuitable for use in multilayer ceramic capacitors.

[0050] According to Non-Patent Document 1, the smaller the ionic radius of the rare earth element R in R2Ti2O7, the more stable the pyrochlore structure. Therefore, in order to promote the shell formation reaction, it is preferable to use lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), which are rare earth elements with an ionic radius larger than that of erbium (Er).

[0051] In the shell portion 412, the added magnesium may react on the surface of the barium titanate crystal particles and may be formed as a shell portion of a composite perovskite compound such as R(Mg,Ti,Mn)O3.

[0052] And the composite perovskite compound considered to be R(Ti,Mn)O3 or R(Mg,Ti,Mn)O3 may be formed as the shell portion 412 as (R,Ba)(Ti,Mn)O3 or (R,Ba)(Mg,Ti,Mn)O3 by reaction with the surrounding barium titanate crystal particles as the main component.

[0053] For example, the core portion 411 in the core-shell structure is mainly composed of crystal particles made of barium titanate, but may contain added rare earth elements, manganese, magnesium, etc. However, for example, as long as the shell portion 412 contains relatively more of the additives such as rare earth elements, manganese, and magnesium than the core portion 411.

[0054] More specifically, crystal particles having a core-shell structure in which a shell containing rare earth elements and manganese is formed with crystal particles composed of barium titanate as the main component may contain relatively more at any point in the range where the distance from the surface to the central part is 10% of the diameter of the corresponding crystal particles, as compared with the elemental ratio of the rare earth elements or manganese to titanium in the central part. The presence of such crystal particles having a core-shell structure not only suppresses the change range of the capacitance retained due to the change in the firing temperature in the polycrystals constituting the dielectric ceramic composition, but also suppresses the movement of oxygen defects inside the grain boundaries and the shell part, suppresses the decrease in resistivity, and makes it possible to improve the electrical life.

[0055] In addition, the average particle diameter of the dielectric particles 41 in the dielectric ceramic composition is in the range of 50 nm to 500 nm, and does not hold particles as large as 3 μm or more in the part that electrically utilizes the dielectric. For example, in the dielectric ceramic composition, the maximum particle diameter of the dielectric particles 41 is preferably 2 μm or less. And, from the viewpoint of the general characteristics of ceramics that the distribution of the particle diameter and composition of the contained crystal particles is within a relatively narrow range, if it can be confirmed that the dielectric particles 41 have a core-shell structure, it can be said that the presence of a large number of dielectric particles 41 having the same structure has a favorable effect on the electrical life of the dielectric magnetic composition.

[0056] The particle size of the dielectric particles 41 can be measured by the following procedure. A dielectric ceramic composition containing the dielectric particles 41 is cut or polished to expose an observation surface. This exposure method is not particularly limited, and methods such as cutting or polishing the element can be adopted. At this time, in order to sufficiently observe the internal ceramic structure, it is preferable to finally use a diamond paste of 2 μm or less to obtain a smoothness that can be judged as a mirror surface. Next, after depositing a conductive substance such as platinum or osmium on the observation surface, it is observed with a scanning electron microscope (SEM: Scanning Electron Microscope), and a photograph of the dielectric particles 41 is taken. Next, a plurality of straight lines parallel to each other are drawn in the taken photograph, and the length of the line segment cut at the periphery of each dielectric particle 41 (the distance between two points where each straight line intersects the periphery of the dielectric particle 41) is taken as the particle size (particle size) of the dielectric particles 41. By this method, the particle size of the dielectric particles 41 is measured for 400 or more particles, and the average of the obtained results is taken as the average particle size of the dielectric particles 41. Also, in the exposed ceramics, when the contour of the dielectric particles 41 is difficult to see, prior to the deposition of platinum or osmium, etc., the exposed ceramics may be heat-treated (thermal etching) at a temperature about 50 °C lower than the firing temperature for about 5 minutes. Instead of this heat treatment, it is also possible to chemically etch using hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, etc., or a mixed acid thereof at an appropriate concentration for etching.

[0057] Here, the presence of dielectric particles 41 having a core-shell structure in the dielectric ceramic composition can be confirmed by the following procedure. In the following procedure, the case where gadolinium is used as a rare earth element is described as an example.

[0058] First, a sample for transmission electron microscope (TEM: Transmission Electron Microscope) observation is cut out from the dielectric ceramic composition to be confirmed. This cutting can be performed by a focused ion beam (FIB) apparatus or the like.

[0059] Next, the cut sample for TEM observation is observed with a TEM equipped with an energy dispersive X-ray spectrometer (EDS) or a wavelength dispersive X-ray spectrometer (WDS) to determine the crystal particles to be measured and identify the outer peripheral shape of the particles.

[0060] Next, as illustrated in FIG. 3, among the line segments connecting any two points located on the outer periphery of the crystal particles to be measured, the one with the maximum length is determined, and the length L of this line segment is measured. Then, this length L is taken as the diameter of the crystal particles to be measured. Also, from the length of the obtained line segment, the midpoint M of the line segment is determined.

[0061] For any point C on the outer periphery within a range where the distances from both ends of the above line segment are 10% of the diameter of the crystal particle, i.e., a length of 10L / 100, a composition analysis is performed by EDS or WDS to calculate the elemental abundance ratio between the corresponding element to be analyzed and titanium. In the composition analysis, for example, in EDS measurement, it can be specified simply by the K-line or L-line of barium, the K-line of calcium, the L-line of gadolinium, the K-line of manganese, and the K-line intensity of titanium relative to the K-line of magnesium. More specifically, from these intensities, a correction (ZAF correction) considering the atomic number effect, absorption effect, and fluorescence excitation effect is performed to calculate the respective ratios to the elemental content of titanium, and this is taken as the ratio of each element to titanium in the shell part 412. Also, for the midpoint M of the above line segment, a composition analysis is similarly performed to calculate the ratio, and this is taken as the ratio of each element to titanium in the core part 411.

[0062] Next, the ratio of each element to titanium in the shell part 412 is compared with the ratio of each element to titanium in the core part 411, and if the shell part 412 is higher than the core part 411, it is determined that the dielectric particle 41 to be measured has a core-shell structure.

[0063] As described above, in addition to the dielectric particles 41, the dielectric ceramic composition holds at least one oxide as the oxide 42 having a higher concentration of the rare earth element R than the shell portion 412. The element ratio of the rare earth element R with respect to the B site of the perovskite constituting the dielectric particles 41 is 0.20 or more higher in the oxide 42.

[0064] The oxide 42 is, for example, an oxide in which barium derived from barium titanate has diffused into a compound having a pyrochlore structure. As described above, in the dielectric ceramic composition according to the present embodiment, the oxide 42 is considered to be a composite perovskite compound such as R(Ti,Mn)O3, R(Mg,Ti,Mn)O3, (R,Ba)(Ti,Mn)O3, (R,Ba)(Mg,Ti,Mn)O3, etc. via an intermediate product such as R2Ti2O7 to form the shell portion 412, and thus is a secondarily generated oxide. By intentionally depositing the oxide 42, dielectric particles 41 can be obtained, and in a multilayer ceramic capacitor where high productivity is required as an example, the change width of the capacitance due to the change in the firing temperature can be suppressed, and high productivity can be obtained.

[0065] Here, the fact that the dielectric ceramic composition contains the oxide 42 having a higher concentration of the rare earth element R than the shell portion 412 can be confirmed by the same method as the method used to confirm the existence of the dielectric particles 41 having the core - shell structure.

[0066] When the element ratio of the rare earth element R with respect to the B site of the perovskite constituting the dielectric particles obtained by the above method is 0.20 or more higher, it is determined that the crystal particles are the oxide 42. At this time, when SEM is used during observation, in the observation by the back scattered electron image (BSE image), the oxide 42 is characterized by being relatively bright and being observed brightly with respect to the shell portion 412.

[0067] Note that, as illustrated in FIG. 4(a), the oxide 42 may be encapsulated inside the shell portion 412. Specifically, the oxide 42 is not in contact with the core portion 411 and is also not in contact with the grain boundaries of the dielectric particles 41. Alternatively, as illustrated in FIG. 4(b), the oxide 42 may be in contact with a part of the core portion 411 at the interface between the core portion 411 and the shell portion 412. Alternatively, as illustrated in FIG. 4(c), the oxide 42 may be in contact with a part of the grain boundaries of the dielectric particles 41. Alternatively, as illustrated in FIG. 4(d), the oxide 42 may extend from a part of the core portion 411 at the interface between the core portion 411 and the shell portion 412 to a part of the grain boundaries of the dielectric particles 41. Further, as illustrated in FIGS. 4(a) to 4(d), in the shell portion 412, a plurality of oxides 42 may be spaced apart from each other. Note that, as illustrated in FIG. 4(e), the oxide 42 may be formed across a plurality of adjacent dielectric particles 41 via grain boundaries, but the oxide 42 is present so as not to connect the core portions 411 of the plurality of dielectric particles 41. The oxides 42 in the forms described in FIGS. 4(a) to 4(e) may be mixed.

[0068] Furthermore, as illustrated in FIG. 1, the dielectric porcelain composition may contain crystal particles 43 having a composition or crystal structure different from those of the dielectric particles 41 and the oxide 42. Also, the dielectric porcelain composition may include crystal particles or glass particles containing silicon. This enables the dielectric porcelain composition to be fired at 1300° C. or lower and sufficiently densified.

[0069] Examples of the crystal particles 43 generally include crystal particles or glass particles such as silicate (SiO2), enstatite (MgSiO3), barium magnesium silicate (BaMgSiO4), and fresnoite (Ba2TiSi2O8).

[0070] In addition, examples of the crystal particles 43 include by-products derived from added substances such as geikielite (MgTiO3), manganese nickel oxide ((Mn,Ni)O), and pyrophanite (MnTiO3), or by-products generated from electrodes.

[0071] Furthermore, the dielectric particles 41, the oxide 42, and the crystal particles 43 may contain a different phase 44 having a different composition or crystal structure.

[0072] A more preferable example of the different phase 44 is barium titanate-based composite oxide represented by Ba4Ti 11 O 26 which is monoclinic, space group C2 / m, lattice constants a = 15.160 Å, b = 3.893 Å, c = 9.093 Å, and β = 98.6°. The barium titanate-based composite oxide is preferable because the ratio of barium to titanium is relatively close to 3 and it is easy to intentionally precipitate without using an additive mainly composed of a large amount of titanium. Note that the crystal phase information of Ba4Ti 11 O 26 was referred to PDF-01-083-1459 in the PDF (Powder Diffraction File) issued by ICDD (International Centre for Diffraction Data; Pennsylvania, USA).

[0073] A further preferable example of the different phase 44 is that magnesium, manganese, and nickel are dissolved in Ba4Ti 11 O 26 to occupy its defect sites or to substitute for some of the titanium. Ba4Ti 11 O 26 has a crystal structure with defects in some of the titanium sites. Therefore, at the defect positions, titanium easily changes from a tetravalent cation to a trivalent cation, and as a result, the resistivity easily decreases. It is effective that at least one of magnesium, manganese, and nickel is dissolved to complement this.

[0074] (Second Embodiment) In the second embodiment, the multilayer ceramic capacitor 100 using the dielectric ceramic composition according to the first embodiment will be described.

[0075] FIG. 5 is a partial cross-sectional perspective view of the multilayer ceramic capacitor 100. FIG. 6 is a cross-sectional view taken along line A-A of FIG. 5. FIG. 7 is a cross-sectional view taken along line B-B of FIG. 5. As illustrated in FIGS. 5 to 7, the multilayer ceramic capacitor 100 includes a multilayer chip 10 having a substantially rectangular parallelepiped shape, and external electrodes 20a and 20b provided on two opposing end faces of the multilayer chip 10. Among the four faces of the multilayer chip 10 other than the two end faces, the two faces other than the upper and lower faces in the stacking direction are referred to as side faces. The external electrodes 20a and 20b extend on the upper face, lower face, and two side faces of the multilayer chip 10 in the stacking direction. However, the external electrodes 20a and 20b are spaced apart from each other.

[0076] The multilayer chip 10 has a structure in which a dielectric layer 11 containing a dielectric ceramic composition and an internal electrode layer 12 containing a base metal material are alternately stacked. The edges of each internal electrode layer 12 are alternately exposed on the end face provided with the external electrode 20a of the multilayer chip 10 and the end face provided with the external electrode 20b. Thereby, each internal electrode layer 12 is alternately electrically connected to the external electrode 20a and the external electrode 20b. As a result, the multilayer ceramic capacitor 100 has a structure in which a plurality of dielectric layers 11 are stacked via the internal electrode layer 12. Further, in the laminate of the dielectric layer 11 and the internal electrode layer 12, the internal electrode layer 12 is disposed in the outermost layer in the stacking direction, and the upper and lower faces of the laminate are covered with a cover layer 13. The cover layer 13 is mainly composed of a ceramic material. For example, the material of the cover layer 13 has the same main component as the dielectric layer 11 and the ceramic material.

[0077] The size of the multilayer ceramic capacitor 100 is, for example, a length of 0.25 mm, a width of 0.125 mm, and a height of 0.125 mm, or a length of 0.4 mm, a width of 0.2 mm, and a height of 0.2 mm, or a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm, or a length of 1.0 mm, a width of 0.5 mm, and a height of 0.5 mm, or a length of 3.2 mm, a width of 1.6 mm, and a height of 1.6 mm, or a length of 4.5 mm, a width of 3.2 mm, and a height of 2.5 mm, but is not limited to these sizes.

[0078] The internal electrode layer 12 is mainly composed of base metals such as nickel (Ni), copper (Cu), and tin (Sn). As the internal electrode layer 12, noble metals such as platinum (Pt), palladium (Pd), silver (Ag), and gold (Au), or alloys containing these may be used.

[0079] As illustrated in FIG. 6, in the laminated ceramic capacitor 100, the region where the internal electrode layer 12 connected to the external electrode 20a and the internal electrode layer 12 connected to the external electrode 20b face each other is the region where capacitance is generated. Therefore, the region where such capacitance is generated is referred to as the capacitance region 14. That is, the capacitance region 14 is the region where adjacent internal electrode layers 12 connected to different external electrodes face each other.

[0080] The region where the internal electrode layers 12 connected to the external electrode 20a face each other without passing through the internal electrode layer 12 connected to the external electrode 20b is referred to as the end margin 15. Also, the region where the internal electrode layers 12 connected to the external electrode 20b face each other without passing through the internal electrode layer 12 connected to the external electrode 20a is also the end margin 15. That is, the end margin 15 is the region where the internal electrode layers 12 connected to the same external electrode face each other without passing through the internal electrode layer 12 connected to a different external electrode. The end margin 15 is a region where no capacitance is generated.

[0081] As illustrated in FIG. 7, in the laminated chip 10, the region from the two side surfaces of the laminated chip 10 to the internal electrode layer 12 is referred to as the side margin 16. That is, the side margin 16 is the region provided so as to cover the ends where the plurality of internal electrode layers 12 laminated in the above-described laminated structure extend to the two side surfaces. The side margin 16 is also a region where no capacitance is generated.

[0082] In the laminated ceramic capacitor 100 according to the present embodiment, at least a part of the dielectric layer 11 in the capacitance region 14 contains the dielectric particles 41 illustrated in FIG. 1 and also contains the oxide 42. Thereby, the change in capacitance due to the firing temperature can be suppressed, and the insulation property can be enhanced in a wide firing atmosphere. As a result, high mass productivity can be obtained.

[0083] Next, a method for manufacturing the multilayer ceramic capacitor 100 will be described. FIG. 8 is a diagram illustrating the flow of the method for manufacturing the multilayer ceramic capacitor 100.

[0084] (Raw material powder preparation step) First, a dielectric ceramic composition for forming the dielectric layer 11 is prepared. The A-site element and the B-site element contained in the dielectric layer 11 are usually contained in the dielectric layer 11 in the form of a sintered body of ABO3 particles. For example, barium titanate is a compound belonging to the tetragonal system near room temperature having a perovskite structure and exhibits a high relative dielectric constant. This barium titanate can generally be synthesized by reacting a titanium raw material such as titanium dioxide, a barium raw material such as barium carbonate, and a calcium raw material such as calcium carbonate. As methods for synthesizing barium titanate, which is the main component of the dielectric layer 11, various conventional methods are known, for example, the solid-phase method, the sol-gel method, the hydrothermal method, etc. In the present embodiment, any of these can be employed.

[0085] A predetermined additive is added to the barium titanate powder obtained by the above method. As an example, additives within the range shown in the example of the dielectric ceramic composition according to the first embodiment are used. If necessary, oxides or glasses containing zirconium (Zr), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K) may also be used.

[0086] For example, a compound containing an additive compound is wet-mixed with barium titanate powder, dried, and pulverized to prepare a barium titanate powder and a ceramic material in which the additive compound is mixed. For example, with respect to the ceramic material obtained as described above, the particle size may be adjusted by pulverization treatment as necessary, or the particle size may be adjusted by combining with a classification treatment. Specifically, together with the ceramic material, beads with a diameter of 0.1 mm to 3 mm made of yttrium-stabilized zirconia, alumina, silicon nitride, etc. are subjected to a stirring treatment for 10 hours to 100 hours to adjust the particle size. Through the above steps, a dielectric porcelain composition is obtained.

[0087] (Coating process) Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the obtained dielectric porcelain composition and wet-mixed. Using the obtained slurry, a ceramic green sheet 51 is coated on a substrate by, for example, the die coater method or the doctor blade method and dried. The substrate is, for example, a polyethylene terephthalate (PET) film. The figure illustrating the coating process is omitted.

[0088] (Internal electrode formation process) Next, as illustrated in FIG. 9(a), an internal electrode pattern 52 that is alternately drawn out to a pair of external electrodes with different polarities is arranged by printing a metal conductive paste for forming an internal electrode containing an organic binder on the surface of the ceramic green sheet 51 by screen printing, gravure printing, etc. Ceramic particles are added to the metal conductive paste as a co-material. The main component of the ceramic particles is not particularly limited, but it is preferably the same as the ceramic that is the main component of the dielectric layer 11. For example, barium calcium titanate with an average particle size of 50 nm or less may be uniformly dispersed.

[0089] Next, a binder such as ethyl cellulose and an organic solvent such as terpineol are added to the dielectric ceramic composition obtained in the raw material powder preparation step, and kneaded with a roll mill to obtain a dielectric pattern paste for the reverse pattern layer. As illustrated in Fig. 9(a), on the ceramic green sheet 51, the dielectric pattern 53 is arranged by printing the dielectric pattern paste in the peripheral region where the internal electrode pattern 52 is not printed, and the step with the internal electrode pattern 52 is filled. The ceramic green sheet 51 on which the internal electrode pattern 52 and the dielectric pattern 53 are printed is referred to as a lamination unit.

[0090] After that, as illustrated in Fig. 9(b), the lamination units are laminated such that the internal electrode layer 12 and the dielectric layer 11 are alternately arranged, and the edges of the internal electrode layer 12 are alternately exposed at both end faces in the length direction of the dielectric layer 11 and drawn out to a pair of external electrodes 20a and 20b having different polarities alternately. For example, the number of laminated internal electrode patterns 52 is set to 100 to 1000 layers.

[0091] (Pressing process) As illustrated in Fig. 10, a cover sheet 54 is laminated on the top and bottom of the laminate in which the lamination units are laminated by a predetermined number (for example, 2 to 10 layers) and thermocompression bonded. As an example of the ceramic material of the cover sheet 54, the above-described dielectric ceramic composition can be used. Then, it is cut into a predetermined chip size (for example, 1.0 mm × 0.5 mm).

[0092] (Firing process) The ceramic laminate thus obtained is debound in an N2 atmosphere, an air atmosphere, etc., and then a metal paste serving as an underlayer for the external electrodes 20a and 20b is applied by a dipping method, and the oxygen partial pressure is 10 -10 ~10 -7 atm. After being kept at 800°C to 1100°C for 10 minutes to 1 hour in a reducing atmosphere, it is fired at 1150 to 1300°C for 10 minutes to 2 hours. In this way, the multilayer ceramic capacitor 100 is obtained.

[0093] (Re-oxidation treatment process) After that, re-oxidation treatment may be performed at 600°C to 1000°C in an N2 gas atmosphere.

[0094] (Plating process) After that, on the base layers of the external electrodes 20a and 20b, a metal coating such as Cu, Ni, Sn, etc. is formed by plating. Through the above steps, the multilayer ceramic capacitor 100 is completed.

[0095] The side margin portion may be attached or applied to the side surface of the above-mentioned laminated portion. Specifically, as illustrated in FIG. 11, a ceramic green sheet 51 and an internal electrode pattern 52 having the same width as the ceramic green sheet 51 are alternately laminated to obtain a laminated portion. Next, a sheet formed of a dielectric pattern paste may be attached as the side margin portion 55 to the side surface of the laminated portion.

[0096] According to the manufacturing method according to the present embodiment, the rare earth element R and titanium added by keeping at 800 to 1100°C for 10 minutes to 1 hour in a reducing atmosphere with an oxygen partial pressure of 10 -10 ~10 -7 atm form R2Ti2O7, which is a compound having a pyrochlore structure or a perovskite slab structure. After that, when the temperature is raised to 1100°C to 1300°C, it reacts with the surface of the barium titanate crystal particles and is formed as a shell portion 412 in the form of a composite perovskite compound such as R(Ti,Mn)O3. Since at least a part of the dielectric layer 11 in the capacitance region 14 is formed with the dielectric particles 41 illustrated in FIG. 1 and can contain the oxide 42, the change in capacitance due to the firing temperature can be suppressed. As a result, high mass productivity can be obtained.

[0097] Regarding the firing temperature dependence (Δε / °C) of the relative permittivity due to the change in the firing temperature of the multilayer ceramic capacitor 100, it is determined by the following method. First, for the multilayer ceramic capacitor 100 that has undergone the firing process, the reoxidation treatment process, and the plating process, the capacitance Cp (nF) and the direct current I (nA) are measured. Next, for the multilayer ceramic capacitor 100, for the A-A line cross-section and the B-B line cross-section illustrated in FIGS. 6 and 7, the capacitance region 14 is exposed by a method such as cutting or polishing, and finally, using a diamond paste or the like with a particle size of 2 μm or less, the effective area of the internal electrode layer is calculated in a state where a smoothness that can be judged as a mirror surface is obtained.

[0098] The effective area S is calculated according to S = L×W×(N - 1) from the length L of the internal electrode layer 12 in the capacitance region 14 in FIG. 6, the number of layers N, and the width W of the internal electrode layer 12 in the capacitance region 14 in FIG. 7.

[0099] Also, at this time, the thickness of each dielectric layer 11 is measured, and the average thickness t is calculated. At this time, the relative permittivity ε can be calculated according to ε = (Cp×t / S) / ε0, where the permittivity of vacuum: ε0 = 8.8542×10 -12 F / m.

[0100] Also, the DC resistivity ρ (Ω·cm) can be calculated according to ρ = (V / I)×(S / t) when the DC voltage at the time of measurement is V (V).

[0101] Regarding the capacitance Cp, generally, it is preferably measured using an LCR meter. When measuring, it is necessary to determine the measurement frequency and the measurement voltage, but the measurement voltage is preferably determined as a measurement electric field depending on the thickness of the dielectric layer 11. In this embodiment, at room temperature of 25°C, with the measurement frequency being 1 kHz and the measurement electric field being 0.5 Vrms / μm, that is, when the thickness of the dielectric layer 11 is 2 μm, it is 1 Vrms, and the capacitance Cp can be measured.

[0102] Regarding the direct current I, it is generally preferable to measure it using an insulation resistance meter. When measuring, it is necessary to determine the measurement voltage, but it is preferably determined as the measurement electric field depending on the thickness of the dielectric layer 11. In the present embodiment, the multilayer ceramic capacitor 100 is held in a thermostat at 150°C for 30 minutes, and insulation from the surroundings is ensured using an insulator made of ceramics or the like. Then, a measurement electric field of 30 V / μm (for example, when the thickness of the dielectric layer 11 is 2 μm, 60 V for 30 seconds) is applied through the electric wires connected to the external electrodes 20a and 20b from the thermostat, and the direct current I is measured to calculate the direct current resistivity ρ. Regarding the measurement, unless otherwise specified, the measurement shall be performed in accordance with Japanese Industrial Standard C5101-22:2021, Fixed capacitors for electronic equipment - Part 22: Generic specification by type - Fixed multilayer ceramic capacitors for surface mounting, type 2.

[0103] Next, the direct current resistivity ρ is measured for the multilayer ceramic capacitors obtained for each firing temperature, and the firing temperature that retains the highest resistivity is defined as the optimal firing temperature. Generally, if the firing temperature is too low, the density becomes low and the resistivity becomes low. If the firing temperature is too high, the ceramic particles become large and the number of grain boundaries decreases, resulting in a decrease in resistivity.

[0104] Next, from the relative permittivity ε of the multilayer ceramic capacitor obtained at the firing temperature that retains the highest resistivity, and from the relative permittivities of the multilayer ceramic capacitors fired at the firing temperatures of -20°C and +20°C from the firing temperature that retains the highest resistivity, the slope of the straight line is obtained by the least squares method based on these firing temperatures and relative permittivities, and that value is determined as the temperature dependence of the relative permittivity (Δε / °C), which is used as an index of high mass productivity.

[0105] The direct current resistivity measured at 150°C is preferably 1.0×10 8 Ω·cm or more. By achieving 1.0×10 8 Ω·cm or more, the multilayer ceramic capacitor 100 using the dielectric ceramic composition of the present embodiment can have sufficient resistance.

[0106] The DC resistivity measured at 150 °C is preferably 1.0×10 10 Ω·cm or more. By achieving 1.0×10 10 Ω·cm or more, the multilayer ceramic capacitor 100 using the dielectric ceramic composition of the present embodiment not only has sufficient resistance, but also becomes easier to design a thinner thickness and increase the number of internal electrodes to be laminated.

[0107] Δε / °C is preferably 10 or less. When it is 10 or less, in the multilayer ceramic capacitor 100 using the dielectric ceramic composition of the present embodiment, it is possible to suppress the change in capacitance due to the change in firing temperature while achieving firing in a shorter time, and obtain high mass productivity.

[0108] The relative permittivity ε is desirably 2000 or more. Even if the DC resistivity measured at 150 °C is 2.0×10 8 Ω·cm or more and the firing temperature dependence of the relative permittivity Δη / °C is 12 or less, if ε is small, the resulting capacitance Cp will be an insufficient value, which is an inappropriate characteristic for the use of the multilayer ceramic capacitor 100 using the dielectric ceramic composition.

[0109] In each of the above embodiments, a multilayer ceramic capacitor has been described as an example of a multilayer ceramic electronic component, but it is not limited thereto. For example, other multilayer ceramic electronic components such as varistors and thermistors may be used.

Examples

[0110] (Example 1) Barium titanate (BaTiO3) powder with an average particle size of 200 nm was prepared. To 100 mol of the barium titanate powder, 0.75 mol of Gd2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to obtain a dielectric ceramic composition.

[0111] The dielectric ceramic composition was mixed with ethanol, toluene, and PVB (polyvinyl butyral) resin to prepare a dielectric slurry. This slurry was formed into a ceramic green sheet using a die coater. After drying this ceramic green sheet, nickel paste was printed to form an internal electrode pattern. The obtained laminated units were laminated, and on the top and bottom, they were pressure-bonded with thickly stacked layers of ceramic green sheets without an internal electrode pattern formed thereon, and then cut into small pieces. Thereafter, Ni paste was dipped on both end faces as a conductive paste for the external electrodes, and degreasing was performed in nitrogen gas. The small pieces after degreasing were fired and sintered in a reducing atmosphere controlled to have an oxygen partial pressure at which nickel does not oxidize to fabricate a multilayer ceramic capacitor. The firing was carried out by maintaining the temperature at 1000°C for 10 minutes and then at 1240°C for 10 minutes.

[0112] The size of the fabricated multilayer ceramic capacitor was in the 1005 form (1.0 mm × 1.0 mm × 0.5 mm). Thereafter, a reoxidation treatment was performed at 950°C. Thereafter, plating was carried out to form a Cu plating layer, a Ni plating layer, and a Sn plating layer on the surface of the base layer, and a multilayer ceramic capacitor was obtained. The average thickness of the dielectric layer 11 was 2.0 μm.

[0113] (Example 2) In Example 2, 0.75 mol of La2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric ceramic composition. The firing was carried out by maintaining the temperature at 1000°C for 10 minutes and then at 1220°C for 10 minutes. Other conditions were the same as those in Example 1.

[0114] (Example 3) In Example 3, 0.75 mol of Pr2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1230 °C for 10 minutes. Other conditions were the same as in Example 1.

[0115] (Example 4) In Example 4, 0.75 mol of Nd2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1230 °C for 10 minutes. Other conditions were the same as in Example 1.

[0116] (Example 5) 0.75 mol of Eu2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1240 °C for 10 minutes. Other conditions were the same as in Example 1.

[0117] (Example 6) 0.75 mol of Dy2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1240 °C for 10 minutes. Other conditions were the same as in Example 1.

[0118] (Example 7) To 100 mol of barium titanate powder, 0.75 mol of Ho2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1250 °C for 10 minutes. Other conditions were the same as in Example 1.

[0119] (Example 8) To 100 mol of barium titanate powder, 0.75 mol of Gd2Ti2O7, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1240 °C for 10 minutes. Other conditions were the same as in Example 1.

[0120] (Example 9) In Example 9, to 100 mol of barium titanate powder, 0.75 mol of Er2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1270 °C for 10 minutes. Other conditions were the same as in Example 1.

[0121] (Example 10) In Example 10, to 100 mol of barium titanate powder, 0.75 mol of Yb2O3, 1.50 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to obtain a dielectric porcelain composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1270 °C for 10 minutes. Other conditions were the same as in Example 1.

[0122] (Comparative Example 1) In Comparative Example 1, 0.75 mol of Gd2O3, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric ceramic composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1260 °C for 10 minutes. Other conditions were the same as those in Example 1.

[0123] (Comparative Example 2) In Comparative Example 2, 0.75 mol of Gd2O3, 0.75 mol of TiO2, 1.00 mol of MnCO3, 1.00 mol of SiO2, and 0.50 mol of MgO were added to 100 mol of barium titanate powder to obtain a dielectric ceramic composition. The firing was carried out by maintaining the temperature at 1000 °C for 10 minutes and then at 1250 °C for 10 minutes. Other conditions were the same as those in Example 1.

[0124] For each of the multilayer ceramic capacitors of Examples 1 to 10 and Comparative Examples 1 to 2, the capacitance Cp at room temperature (25 °C) at 1 kHz and 1 Vrms was measured using an LCR meter, and the DC current I at 150 °C when 60 V was applied for 30 seconds was measured using an insulation resistance meter. Also, the cross-sections along the A-A line and B-B line in Fig. 5 were exposed to calculate the effective area S of the internal electrode layer and the average thickness t of the dielectric layer. From the effective area S and the average thickness t, the relative permittivity ε and the resistivity ρ were calculated. Then, the resistivities ρ of the multilayer ceramic capacitors of Examples 1 to 10 and Comparative Examples 1 to 2 were compared, and referring to the relative permittivity of the multilayer ceramic capacitor obtained at the firing temperature with the highest resistivity, the slope of the straight line was obtained by the least squares method based on these firing temperatures and the relative permittivity, and the temperature dependence of the relative permittivity (Δε / °C) was defined.

[0125] Furthermore, a conductive substance of osmium was vapor-deposited on the exposed dielectric layer, and photographs of the crystal particles present in the dielectric layer were taken by SEM observation. Then, the average particle diameter of the crystal particles constituting the dielectric layer was calculated. The average particle diameter was 270 nm in Example 1, 260 nm in Example 2, 280 nm in Example 3, 280 nm in Example 4, 270 nm in Example 5, 280 nm in Example 6, 260 nm in Example 7, 270 nm in Example 8, 250 nm in Example 9, 240 nm in Example 10, 550 nm in Comparative Example 1, and 410 nm in Comparative Example 2.

[0126] In addition, when observing the laminated ceramic capacitor by SEM, in the BSE image, whether the oxide 42 was present was confirmed by the difference in its luminance.

[0127] Then, for each laminated ceramic capacitor, in order to confirm the composition of the shell part and the core part in the crystal particles of the dielectric layer and the oxide 42, a sample for EDS observation by TEM was cut out by FIB, and it was confirmed whether it had a core-shell structure by the method of composition evaluation by EDS. The element ratio of R / Ti less than 0.02 was defined as the core part, and the element ratio of 0.02 or more and less than 0.20 was defined as the shell part. Also, for the oxide 42, the element ratio of the rare earth element R to titanium was confirmed, and it was confirmed whether the element ratio of R / Ti satisfied 0.20 or more.

[0128] Also, for each laminated ceramic capacitor, after separating the cover layer, the end margin, the side margin, and the external electrode, which are outside the capacitance region, by polishing or cutting, for the powder obtained by pulverizing the dielectric layer constituting the capacitance region, the diffraction line profile was measured with an X-ray diffractometer (XRD) using Cu-Kα rays, and it was confirmed whether the oxide 42 that could be identified as R2Ti2O7 was present.

[0129] Table 1 summarizes the addition amounts of additives in Comparative Examples 1-2 and Examples 1-10. Table 2 summarizes the firing temperatures, average particle diameters, ε, Δε / °C, and resistivity at 150°C in Comparative Examples 1-2 and Examples 1-10. For pass / fail determination, those satisfying Δε / °C ≤ 10 and resistivity ≥ 1.0×10 9 Ω·cm are rated as pass "○", those satisfying Δε / °C ≤ 10 are rated as "△", and those not satisfying are rated as fail "×".

Table 1

Table 2

[0130] Comparative Examples 1 and 2 are comparative examples where gadolinium is contained as a rare earth element. In Comparative Examples 1 and 2, since gadolinium is contained as a rare earth element, the average particle diameters are 550 nm and 410 nm, respectively, resulting in a resistivity at 150°C of 1.9×10 8 Ω·cm, and sufficient resistivity could be maintained. However, since they did not have a sufficient TiO2 addition amount, the value of Δε / °C became greater than 10, and a preferable value of 10 or less could not be obtained.

[0131] In Examples 1 to 7, 9, and 10, 1.5 mol of TiO2 was added per 100 mol of BaTiO3, and 0.75 mol each of lanthanum, praseodymium, neodymium, europium, gadolinium, dysprosium, holmium, erbium, and ytterbium was added as rare earth elements. In Example 8, 0.75 mol of Gd2Ti2O7 was added per 100 mol of BaTiO3. In this composition, the value of Δε / °C was 10 or less. For example, even when a firing furnace larger than the existing one was used to increase the productivity efficiency, the dielectric constant obtained with respect to the temperature distribution in the furnace, that is, the value of the capacitance Cp of the multilayer ceramic capacitor did not have a large distribution. Therefore, even in firing in a short time by rapid temperature increase, mass production can be made possible. Also, in the case of europium, gadolinium, dysprosium, and holmium as rare earth elements, ε was 3000 or more. The average particle diameter was also 500 nm or less, and the resistivity was 1.0×10 9 Ω·cm or more.

[0132] To investigate the mechanism of the dielectric layer in detail, an investigation was conducted on the multilayer ceramic capacitors obtained in Comparative Examples 1 and 2 and Examples 1 to 10 by STEM-EDS as to whether a core-shell structure exists, whether oxide 42 exists, and whether the element ratio v of Ba to Ti in oxide 42 is in the range of v≤0.70 and whether the element ratio w of rare earth element R to Ti is in the range of 0.40≤w. The results are summarized in Table 3.

Table 3

[0133] In Comparative Examples 1 and 2, since the amount of TiO2 added was insufficient, the presence of oxide 42, which was relatively high in luminance and brightly observed with respect to the main crystal particles composed of barium titanate, could not be confirmed in the SEM-BSE image.

[0134] On the other hand, in Examples 1 to 10, the elemental ratio w of the rare earth element R to Ti in the oxide 42 was in the range of 0.2 ≦ w, and the presence of the oxide 42 was also apparent. Further, in Examples 1 to 8, the oxide 42 did not contact the cores of a plurality of particles. Furthermore, as shown in Table 1, the value of Δε / °C was 10 or less, the resistivity was 1.0×10 8 Ω·cm or more, and its average particle diameter was 500 nm or less, and it had a dielectric constant of ε>2000 or more. Therefore, for example, even when a firing furnace larger than the existing firing furnace is used to increase the productivity efficiency, the relative dielectric constant obtained with respect to the temperature distribution in the furnace, that is, the value of the capacitance Cp as a multilayer ceramic capacitor does not have a large distribution. For this reason, even in firing in a short time by rapid temperature increase, mass production can be made possible, and sufficient reliability can be obtained.

[0135] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Description of Reference Numerals

[0136] 10 Multilayer chip 11 Dielectric layer 12 Internal electrode layer 13 Cover layer 14 Capacitance region 15 End margin 16 Side margin 20a, 20b External electrode 41 Dielectric particles 42 Oxide 43 Crystal particles 51 Ceramic green sheet 52 Internal electrode pattern 53 Dielectric pattern 54 Cover sheet 55 Side margin portion 100 Multilayer ceramic capacitor

Claims

1. A multilayer ceramic electronic component having a plurality of internal electrode layers facing each other, Provided between the plurality of internal electrode layers, it has a core part, a shell part covering the core part and containing a rare earth element, and an oxide that segregates inside the shell part and has a higher concentration of the rare earth element than the shell part, and has a general formula ABO ３ A dielectric layer containing dielectric particles having a perovskite structure represented by and an external electrode electrically connected to the plurality of internal electrode layers.

2. The multilayer ceramic electronic component according to claim 1, wherein the oxide contains a pyrochlore phase.

3. The multilayer ceramic electronic component according to claim 1, wherein barium is included in the A site of the perovskite structure, and at least one of titanium and zirconium is included in the B site of the perovskite structure.

4. The multilayer ceramic electronic component according to claim 1, wherein the rare earth element consists of at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, and erbium.

5. The multilayer ceramic electronic component according to claim 1, wherein the shell part has a rare earth element ratio to titanium of 0.02 or more and less than 0.

20.

6. The multilayer ceramic electronic component according to claim 1, wherein the oxide has a rare earth element ratio to titanium of 0.20 or more.

7. The multilayer ceramic electronic component according to claim 1, wherein the oxide is encapsulated inside the shell part.

8. The multilayer ceramic electronic component according to claim 1, wherein the oxide is in contact with a part of the core part.

9. The multilayer ceramic electronic component according to claim 1, wherein the oxide is in contact with a part of the grain boundary of the dielectric particles.

10. The multilayer ceramic electronic component according to claim 1, wherein the oxide extends from a part of the core part to a part of the grain boundary of the dielectric particles.

11. The multilayer ceramic electronic component according to claim 1, wherein a plurality of the oxides exist separately from each other in the shell part.

12. The multilayer ceramic electronic component according to claim 1, wherein a plurality of the dielectric particles are adjacent to each other through grain boundaries, and the oxide does not connect the core parts of the plurality of dielectric particles.

13. The multilayer ceramic electronic component according to claim 1, wherein the oxide is not in contact with the core part.

14. The multilayer ceramic electronic component according to claim 1, wherein the maximum particle size of the dielectric particles is 2 μm or less.

15. The multilayer ceramic electronic component according to claim 1, wherein the shell part contains magnesium and manganese.

16. A core part, a shell part covering the core part and containing a rare earth element, and an oxide having a higher concentration of the rare earth element than the shell part inside the shell part, and having a general formula ABO ３ A dielectric ceramic composition containing dielectric particles having a perovskite structure represented by

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