Multilayer ceramic electronic component and dielectric ceramic composition

Abstract

The present invention provides a laminated ceramic electronic component and a dielectric ceramic composition capable of suppressing a change in capacitance caused by a firing temperature. The laminated ceramic electronic component includes: a plurality of internal electrode layers facing each other; and a dielectric layer provided so as to be sandwiched between the plurality of internal electrode layers, the dielectric layer containing dielectric particles (41) having a perovskite structure represented by general formula ABO3, the dielectric particles (41) having a core part (411), a shell part (412) covering the core part (411) and containing a rare earth element, and an oxide (42) segregated inside the shell part (412), the shell part (412) containing a rare earth element, and the oxide (42) containing a rare earth element. The concentration of the rare earth element in the oxide (42) is higher than the concentration of the rare earth element in the shell part (412); and an external electrode electrically connected to the plurality of internal electrode layers.

Description

Technical Field

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

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

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-124779

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-210783

[0007] Non-Patent Documents

[0008] Non-Patent Document 1: Proceedings of the Faculty of Education, Shimane University (Natural Sciences), Vol. 36, pp. 65-69 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] In recent years, in electronic circuits related to human life such as in-vehicle electronic control devices, the use of multilayer ceramic electronic components has also been expanding. While high reliability is required, from the perspective of supply volume, higher mass productivity is required.

[0011] In the dielectric porcelain composition used in the dielectric layer of the multilayer ceramic electronic component, a sintered body having a core-shell structure in which a core portion made of barium titanate is surrounded by a shell portion in which various additives are solid-solved is used. By adopting this structure, it is possible to cause the manifestation of a large electrostatic capacitance near the Curie temperature at which barium titanate existing near 125°C changes from a ferroelectric phase to a paraelectric phase, and to shift it to a lower temperature by the effects of various additives in the shell portion. Therefore, it is possible to design for further increasing the electrostatic capacitance in a practical temperature range near room temperature.

[0012] It is considered that the core-shell structure can be formed by solid-solving various additives in barium titanate. It is considered that the core-shell structure can be formed by reacting components added as various additives in barium titanate particles as the main component in a firing temperature range of, for example, 1000°C to 1400°C. Generally, as the firing temperature increases, various additives are solid-solved and the shell portion becomes thicker. Therefore, in order to keep the electrostatic capacitance of the multilayer ceramic electronic component within the required range, it is necessary to precisely control the solid solution of various additives.

[0013] For example, Patent Documents 1 and 2 disclose a dielectric porcelain composition, a dielectric material, and a multilayer ceramic capacitor including the same, which contain a main component of barium titanate and a sub-component and can control the relative intensity of a pyrochlore phase containing a rare earth element in XRD analysis after sintering.

[0014] In recent years, the usage applications of dielectric porcelain compositions and multilayer ceramic electronic components have been expanding, and thus, higher mass productivity is required. Therefore, it is necessary to suppress the change in capacitance caused by the firing temperature and reduce the fluctuation of capacitance caused by temperature.

[0015] The present invention has been made in view of the above technical problems, and an object thereof is to provide a multilayer ceramic electronic component and a dielectric porcelain composition capable of suppressing the change in capacitance caused by the firing temperature.

[0016] Means for Solving the Technical Problems

[0017] The multilayer ceramic electronic component of the present invention includes: a plurality of internal electrode layers facing each other; a dielectric layer disposed so as to be sandwiched by the plurality of internal electrode layers, which contains dielectric particles having a perovskite structure represented by the general formula ABO3, the dielectric particles having a core portion, a shell portion, and an oxide, the shell portion covering the core portion and containing a rare earth element, the oxide segregating inside the shell portion, and the concentration of the rare earth element in the oxide being higher than the concentration of the rare earth element in the shell portion; and external electrodes electrically connected to the plurality of internal electrode layers.

[0018] In the above multilayer ceramic electronic component, the oxide may contain a pyrochlore phase.

[0019] In the above multilayer ceramic electronic component, the A-site of the perovskite structure may contain barium, and the element contained in the B-site of the perovskite structure is at least one element selected from titanium and zirconium.

[0020] In the above multilayer ceramic electronic component, the rare earth element may be composed of at least one element selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, and erbium.

[0021] In the above multilayer ceramic electronic component, the element ratio of the rare earth element in the shell portion to titanium may be 0.02 or more and less than 0.20.

[0022] In the above multilayer ceramic electronic component, the element ratio of the rare earth element in the oxide to titanium may be 0.20 or more.

[0023] In the above-described multilayer ceramic electronic component, it is possible that the oxide is enclosed inside the shell portion.

[0024] In the above-described multilayer ceramic electronic component, it is possible that the oxide contacts a part of the core portion.

[0025] In the above-described multilayer ceramic electronic component, it is possible that the oxide contacts a part of the grain boundary of the dielectric particles.

[0026] In the above-described multilayer ceramic electronic component, it is possible that the oxide extends from a part of the core portion to a part of the grain boundary of the dielectric particles.

[0027] In the above-described multilayer ceramic electronic component, it is possible that in the shell portion, a plurality of the oxides are present at intervals.

[0028] In the above-described multilayer ceramic electronic component, it is possible that a plurality of the dielectric particles are adjacent to each other across grain boundaries, and the oxide does not connect the core portions of the plurality of dielectric particles.

[0029] In the above-described multilayer ceramic electronic component, it is possible that the oxide does not contact the core portion.

[0030] In the above-described multilayer ceramic electronic component, it is possible that the maximum particle size of the dielectric particles is 2 μm or less.

[0031] In the above-described multilayer ceramic electronic component, it is possible that the shell portion contains magnesium and manganese.

[0032] The dielectric porcelain composition of the present invention contains dielectric particles having a perovskite structure represented by the general formula ABO3, the dielectric particles having a core portion, a shell portion, and an oxide, the shell portion covering the core portion and containing a rare earth element, the oxide being segregated inside the shell portion, and the concentration of the rare earth element in the oxide being higher than the concentration of the rare earth element in the shell portion.

[0033] Advantages of the Invention

[0034] By adopting the present invention, it is possible to provide a multilayer ceramic electronic component and a dielectric porcelain composition capable of suppressing changes in capacitance caused by firing temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a diagram illustrating the dielectric porcelain composition of the first embodiment.

[0036] Figure 2 is a diagram illustrating a unit cell.

[0037] Figure 3 is a diagram illustrating a method for confirming a core-shell structure.

[0038] Figure 4 (a) to (e) of FIG. are diagrams illustrating the existence form of the oxide.

[0039] Figure 5 is a partial cross-sectional perspective view of a multilayer ceramic capacitor.

[0040] Figure 6 is Figure 5 a cross-sectional view taken along line A-A of FIG.

[0041] Figure 7 is Figure 5 a cross-sectional view taken along line B-B of FIG.

[0042] Figure 8 is a diagram illustrating the process flow of a method for manufacturing a multilayer ceramic capacitor.

[0043] Figure 9 (a) and (b) of FIG. are diagrams illustrating the internal electrode formation process.

[0044] Figure 10 is a diagram illustrating the crimping process.

[0045] Figure 11 is a diagram illustrating the side edge portion.

[0046] Explanation of reference numerals

[0047] 10 stacked sheets, 11 dielectric layer, 12 internal electrode layer, 13 covering layer, 14 capacitance region, 15 end edge, 16 side edge, 20a, 20b external electrodes, 41 dielectric particles, 42 oxide, 43 crystal grains, 51 green sheet, 52 internal electrode pattern, 53 dielectric pattern, 54 covering sheet, 55 side edge portion, 100 multilayer ceramic capacitor. Detailed description of the invention

[0048] Hereinafter, embodiments will be described with reference to the drawings.

[0049] (First Embodiment)

[0050] The dielectric porcelain composition of the first embodiment, as Figure 1 illustrated, is a ceramic polycrystal containing crystal grains having a perovskite structure represented by the general formula ABO3. At least one of these ceramic polycrystals is a dielectric particle 41 having a core-shell structure.

[0051] The dielectric particle 41 includes: a core portion 411 having a substantially spherical shape; and a shell portion 412 covering the core portion 411 so as to surround the core portion 411. The core portion 411 is a crystalline portion without a solid-solution added compound or with a small solid-solution amount of the added compound. The shell portion 412 is a crystalline portion in which the added compound is solid-solved and has an added compound concentration higher than that 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 is lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), etc. The element concentration of the rare-earth element R in the shell portion 412 is greater than the element concentration of the rare-earth element in the core portion 411.

[0052] In the shell portion 412, an oxide 42 is segregated, and the concentration of the rare-earth element R in the oxide 42 is higher than the concentration of the rare-earth element R in the shell portion 412. 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 larger than the total cross-sectional area of the respective oxides 42.

[0053] The dielectric porcelain composition of the present embodiment contains the dielectric particle 41 and the oxide 42, and thus has high insulation and can suppress the variation of the capacitance caused by the firing temperature.

[0054] For example, in the cross section of the dielectric porcelain composition, when observed in a field of view where 100 or more can be confirmed in total of the dielectric particle 41 and the oxide 42, the area ratio of the dielectric particle 41 is 95% or more and 99.95% or less, and the area ratio of the oxide 42 is 0.01% or more and 5% or less.

[0055] The crystal grains having a perovskite structure as the main component of the dielectric particle 41 have Figure 2 the unit lattice as exemplified in. In this unit lattice, an A site located at the vertex of the lattice, an O site located at the face center of the lattice, and a B site located inside the octahedron with the O site as the vertex are respectively present. In the perovskite structure, the A site is occupied by an alkaline earth metal capable of acquiring a divalent cation such as barium (Ba), strontium (Sr), or calcium (Ca), and the B site is occupied by a metal atom capable of acquiring a tetravalent cation such as hafnium (Hf), zirconium (Zr), or titanium (Ti).

[0056] The perovskite structure also allows a composition formula deviating from the stoichiometric composition. That is, the ratio of the A-site element to the B-site element does not necessarily need to be 1:1, and defects can also be generated within the range capable of maintaining the perovskite structure. In addition, defects can also be generated with respect to oxygen. For example, when formed into the composition formula A α BO 3-βWhen it is possible, a composition in the range of 0.98 ≤ α ≤ 1.01 and 0 ≤ β ≤ 0.20 is allowed.

[0057] However, for example, due to the generation of oxygen defects, the resistivity decreases, ionic conductivity is exhibited, and thus, the electrical life when used as a multilayer ceramic capacitor decreases, and the dielectric loss becomes large, and there are cases where it cannot be used in practical applications. Therefore, for the dielectric particles 41 having a perovskite structure, it may contain at least one element of scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn) as a first transition element as needed. Thereby, the resistivity can be increased, the electrical life can be improved, and the dielectric loss with respect to the capacitance can be reduced.

[0058] In addition, the dielectric particles 41 may contain at least one element of yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), and silver (Ag) as a second transition element as needed. Thereby, the resistivity can be increased, the electrical life can be improved, and the dielectric loss with respect to the capacitance can be reduced.

[0059] In addition, the dielectric particles 41 may contain at least one element 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) as a third transition element as needed. Thereby, the resistivity can be increased, the electrical life can be improved, and the dielectric loss with respect to the capacitance can be reduced.

[0060] In the dielectric porcelain composition, an additive containing rare earth elements R such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), and terbium (Tb) is preferably added. In addition, in the dielectric porcelain composition, an additive containing titanium is preferably added such 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 the additive containing titanium is not added, the solid solution reaction with barium titanate grains can be relatively suppressed. By using this effect, firing can be achieved in a shorter time, and at the same time, the change rate of the capacitance caused by the change in the firing temperature can be suppressed, and high mass productivity can be obtained.

[0061] As the additive containing rare earth element R described above, 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. are preferred.

[0062] As the additive containing titanium described above, titanium oxide is a preferred example, but titanium hydroxide (Ti(OH)4), titanium chloride (TiCl4), titanium carbide (TiC), titanium sulfide (TiS2), etc. can also be used.

[0063] In addition, as the additive containing rare earth element R and titanium, La2Ti2O7, Ce2Ti2O7, Pr2Ti2O7, Nd2Ti2O7, Pm2Ti2O7, Sm2Ti2O7, Eu2Ti2O7, Gd2Ti2O7, Tb2Ti2O7, Dy2Ti2O7, Ho2Ti2O7, etc. can also be used.

[0064] In the dielectric porcelain composition, in addition to adding rare earth element R, it is preferred to add 0.2 mol or more and 5.0 mol or less in terms of manganese oxide (MnO) conversion relative to 100 mol of barium titanate so that the manganese element ratio to the titanium content, i.e., the Mn / Ti element ratio z, becomes 0.002 ≤ z ≤ 0.05.

[0065] However, in the core-shell structure, generally as the firing temperature becomes higher, there is a tendency for various additives to dissolve more in the grains composed of barium titanate, making the shell part thicker. In the shell part, the large electrostatic capacitance region near the Curie temperature of barium titanate, i.e., near 125 °C, approaches room temperature. Thus, the electrostatic capacitance in the practical temperature region near room temperature will vary significantly due to the thickness of the shell part. Therefore, as an example, in order to make the electrostatic capacitance of the multilayer ceramic capacitor within the required range, it is preferred to precisely control the firing temperature.

[0066] For example, the dielectric porcelain composition of the present embodiment can be obtained by maintaining the temperature at 900 °C to 1100 °C, then firing at 1150 °C to 1300 °C, and rapidly raising the temperature at a heating rate of 3000 °C / h to 10000 °C / h during the firing process.

[0067] The dielectric particle 41 having a core-shell structure with a shell portion 412 containing a rare-earth element formed thereon has a production process different from that of the conventional core-shell structure. Specifically, not only is the rare-earth element R dissolved in the crystal grains composed of barium titanate, but after the added rare-earth element R forms a compound R2Ti2O7 having a pyrochlore structure or a perovskite plate structure with titanium, it reacts with the surface of the barium titanate crystal grains to form a shell portion 412 in the form of a composite perovskite compound such as R(Ti,Mn)O3. Therefore, the excessive solid solution reaction of the rare-earth element R or the like in the shell portion 412 can be suppressed, and the change rate of the electrostatic capacitance caused by the change in the firing temperature can be suppressed. As a trace of the production process of such a shell portion 412, an oxide region having a higher concentration of the rare-earth element R than that of the shell is generated. In addition, the formation reaction of R2Ti2O7 proceeds between 900 °C and 1100 °C.

[0068] In order to promote the shell formation reaction, the rare-earth element R is preferably an element that is easily dissolved in the A site of ABO3. Specifically, rare-earth elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and holmium (Ho) having an ionic radius larger than that of erbium (Er) are preferred.

[0069] On the other hand, when a rare-earth element R (erbium, thulium, ytterbium, ruthenium) having an ionic radius smaller than that of holmium is used, although a compound R2Ti2O7 having a pyrochlore structure is formed, R2Ti2O7 cannot sufficiently undergo a shell formation reaction with the barium titanate crystal grains, and there is a possibility that the cores of multiple particles are in electrical contact with the oxide region. As a result, the resistivity decreases, and it may not be suitable for use in multilayer ceramic capacitors.

[0070] In addition, 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, rare-earth elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and holmium (Ho) having an ionic radius larger than that of erbium (Er) are preferably used.

[0071] In the shell portion 412, further added magnesium can react on the surface of the barium titanate crystal grains to form a shell portion of a composite perovskite compound such as R(Mg,Ti,Mn)O3.

[0072] Moreover, the composite perovskite compound considered to be R(Ti,Mn)O3 or R(Mg,Ti,Mn)O3 can react with the surrounding barium titanate crystal grains as the main component to form (R,Ba)(Ti,Mn)O3 or (R,Ba)(Mg,Ti,Mn)O3 as the shell portion 412.

[0073] For example, the core portion 411 in the core-shell structure mainly consists of crystal grains composed of barium titanate, but may also contain added rare earth elements, manganese, magnesium, etc. However, for example, as long as the shell portion 412 contains relatively more rare earth elements, manganese, magnesium, etc. in the additive compared to the core portion 411.

[0074] More specifically, for crystal grains having a core-shell structure with a core mainly composed of crystal grains composed of barium titanate and a shell containing rare earth elements and manganese, at any point within a range of 10% of the diameter of the crystal grain from the surface towards the central portion, it is sufficient if the rare earth elements or manganese are relatively more contained compared to the elemental ratio of rare earth elements or manganese to titanium in the central portion. Due to the presence of such crystal grains having a core-shell structure, the polycrystals constituting the dielectric porcelain composition can not only suppress the change amplitude of the held electrostatic capacitance caused by the change in the firing temperature, but also suppress the movement of oxygen defects within the grain boundaries and the shell portion, suppress the decrease in resistivity, and thereby improve the electrical life.

[0075] In addition, the average particle diameter of the dielectric particles 41 in the dielectric porcelain composition is in the range of 50 nm to 500 nm, and no giant particles of 3 μm or more are retained at the portion electrically utilized as a dielectric. For example, in the dielectric porcelain composition, the maximum particle diameter of the dielectric particles 41 is preferably 2 μm or less. Moreover, from the perspective of the general ceramic property that the particle diameter and composition distribution of the contained crystal grains are 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 due to the presence of a plurality of dielectric particles 41 having the same structure, it can have a good influence on the electrical life of the dielectric porcelain composition.

[0076] The particle size of the dielectric particles 41 can be measured according to the following steps. By means of cutting or grinding, the observation surface of the dielectric porcelain composition having the dielectric particles 41 is exposed. The exposure method is not particularly limited, and methods such as using a cutting or grinding element can be adopted. At this time, in order to fully observe the internal ceramic structure, it is preferable to finally use diamond paste with a particle size of 2 μm or less to obtain a smoothness that can be judged as a mirror surface. Next, after evaporating a conductive substance such as platinum or osmium on the observation surface, observation is carried out using 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 obtained by intercepting each straight line by the periphery of each dielectric particle 41 (the distance between the two points where each straight line intersects the periphery of the dielectric particle 41) is used as the particle size (grain size) of the dielectric particle 41. Using this method, the particle size of the dielectric particles 41 is measured for 400 or more particles, and the average value of the obtained results is used as the average particle size of the dielectric particles 41. In addition, when it is difficult to see the outline of the dielectric particles 41 in the exposed ceramic, before the evaporation of platinum or osmium, etc., the exposed ceramic can 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, chemical etching can also be carried out using hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, etc. or an acid obtained by mixing them at a concentration suitable for etching.

[0077] Here, the fact that there are dielectric particles 41 having a core-shell structure in the dielectric porcelain composition can be confirmed by the following steps. In addition, in the following steps, as an example, the case of using gadolinium as a rare earth element is described.

[0078] First, a specimen for transmission electron microscope (TEM: Transmission Electron Microscope) observation is cut out from the dielectric porcelain composition to be confirmed. This cutting can be carried out by means of a focused ion beam (FIB) device or the like.

[0079] Next, the cut TEM observation specimen is observed using a TEM equipped with an energy dispersive X-ray spectrometer (EDS: Energy Dispersive X-ray Spectrometry) or a wavelength dispersive X-ray spectrometer (WDS: Wavelength Dispersive X-ray Spectrometry) to determine the crystal grains to be measured and the outer peripheral shape of the particles.

[0080] Next, as Figure 3As illustrated, the line segment with the maximum length among the line segments connecting any two points on the outer periphery of the grain to be measured is determined, and the length L of this line segment is measured. Then, this length L is taken as the diameter of the grain to be measured. In addition, the midpoint M of this line segment is determined based on the obtained length of the line segment.

[0081] For any C point on the outer periphery within a length range that is 10% of the diameter of the grain, i.e., 10L / 100, from both ends of the above line segment, composition analysis is performed using EDS or WDS, and the elemental abundance ratio of the element to be analyzed to titanium is calculated. In the composition analysis, for example, in EDS measurement, simply speaking, it can be determined based on the K-line intensity of titanium relative to 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 of magnesium. More specifically, based on their intensities, corrections considering the atomic number effect, absorption effect, and fluorescence excitation effect (ZAF correction) are made, and the ratio of each element content relative to titanium is calculated, which is taken as the ratio of each element in the shell part 412 to titanium. In addition, for the midpoint M of the above line segment, composition analysis is also performed in the same way to calculate the ratio, which is taken as the ratio of each element in the core part 411 to titanium.

[0082] Next, the ratio of each element in the shell part 412 to titanium is compared with the ratio of each element in the core part 411 to titanium. If the ratio of the shell part 412 is higher than that of the core part 411, it is determined that the dielectric particle 41 to be measured has a core-shell structure.

[0083] As described above, in addition to the dielectric particle 41, the dielectric porcelain composition further retains at least one oxide in which the concentration of the rare earth element R is higher than that of the shell part 412 as the oxide 42. The elemental ratio of the rare earth element R in the oxide 42 is 0.20 or more higher than that of the B-site of the perovskite constituting the dielectric particle 41.

[0084] The oxide 42 is, for example, an oxide formed by the diffusion of barium from barium titanate in a pyrochlore structure compound. As described above, in the dielectric porcelain composition of the present embodiment, the oxide 42 forms the shell part 412 in the form of a complex 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, and thus becomes a secondarily generated oxide. By intentionally precipitating the oxide 42, dielectric particles 41 can be obtained. As an example, in a multilayer ceramic capacitor that requires high mass productivity, the variation range of the capacitance caused by the change in the firing temperature can be suppressed, and high mass productivity can be achieved.

[0085] Here, the fact that the dielectric porcelain 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 for confirming the presence of the dielectric particles 41 having a core-shell structure described above.

[0086] When the element ratio of the rare earth element R is 0.20 or more higher with respect to the B site of the perovskite constituting the dielectric particles obtained by the above method, it is determined that the crystal grain is the oxide 42. At this time, when observing using SEM, in the observation based on the reflected electron image (BSE image: Back Scattered Electron Image), it is characterized in that the oxide 42 is relatively brighter and looks brighter than the shell portion 412.

[0087] In addition, it may be that, as exemplified in (a) of Figure 4 , the oxide 42 is enclosed inside the shell portion 412. Specifically, the oxide 42 does not contact the core portion 411 and does not contact the grain boundary of the dielectric particles 41. Or, it may be that, as exemplified in (b) of Figure 4 , the oxide 42 contacts a part of the core portion 411 at the interface between the core portion 411 and the shell portion 412. Or, it may be that, as exemplified in (c) of Figure 4 , the oxide 42 contacts a part of the grain boundary of the dielectric particles 41. Or, it may be that, as shown in (d) of Figure 4 , the oxide 42 extends 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 boundary of the dielectric particles 41. In addition, it may be that, as exemplified in (a) to Figure 4 of Figure 4 , in the shell portion 412, a plurality of oxides 42 are present at intervals from each other. Further, it may be that, as exemplified in (e) of Figure 4 , the oxide 42 is formed across a plurality of dielectric particles 41 adjacent to the grain boundary, but the oxide 42 exists in such a manner that it does not connect the core portions 411 of the plurality of dielectric particles 41. Figure 4 The oxides 42 in the forms described in (a) to Figure 4 of (e) may be mixed and present.

[0088] In addition, as exemplified in Figure 1 , the dielectric porcelain composition may also contain crystal grains 43 having a composition or crystal structure different from those of the dielectric particles 41 and the oxide 42. In addition, the dielectric porcelain composition may also contain crystal grains containing silicon or glass particles. Thereby, the dielectric porcelain composition can be fired at 1300 °C or lower to be sufficiently densified.

[0089] As the crystal grains 43, crystal grains or glass particles such as silicate (SiO2), enstatite (MgSiO3), barium magnesium silicate (BaMgSiO4), barium titanium silicate (Ba2TiSi2O8), etc. can generally be cited.

[0090] In addition, as the crystal grains 43, substances added or by-products from the electrodes such as perovskite (MgTiO3), manganese nickel oxide ((Mn, Ni)O), and red manganese titanate (MnTiO3) can be cited.

[0091] Moreover, a heterogeneous phase 44 having a composition or crystal structure different from that of the dielectric particles 41, the oxide 42, and the crystal grains 43 may also be contained.

[0092] As a more preferable example of the heterogeneous phase 44, preferably, a barium titanate-based composite oxide having a monoclinic crystal system, represented by the space group C2 / m, and a lattice constant of 11 O 26 β = 98.6° is taken as an example. This is because, in this barium titanate-based composite oxide, the ratio of barium to titanium is relatively close to 3, and it is easy to intentionally precipitate it even without using a large amount of additives mainly composed of titanium. In addition, for the crystal phase information of Ba4Ti O 11 O 26 , refer to PDF-01-083-1459 in the PDF (Powder Diffraction File) published by ICDD (International Centre for Diffraction Data; Pennsylvania, USA).

[0093] As a more preferable example of the heterogeneous phase 44, preferably, with respect to Ba4Ti 11 O 26 , magnesium, manganese, and nickel are solid-solved to occupy its defect sites exclusively, or a part of titanium is replaced. Ba4Ti 11 O 26 becomes a crystal structure with defects generated at a part 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 is easily reduced. To supplement this, it is effective to solid-solve at least one of magnesium, manganese, and nickel.

[0094] (Second Embodiment)

[0095] In the second embodiment, the multilayer ceramic capacitor 100 using the dielectric porcelain composition of the first embodiment will be described.

[0096] Figure 5 is a partial cross-sectional perspective view of the multilayer ceramic capacitor 100.Figure 6 is Figure 5 a sectional view taken along line A-A of Figure 7 is Figure 5 a sectional view taken along line B-B of Figures 5 to 7 As illustrated, the multilayer ceramic capacitor 100 includes: a multilayer chip 10 having a substantially rectangular parallelepiped shape; and external electrodes 20a and 20b provided on any two opposite end faces of the multilayer chip 10. In addition, among the four faces other than the two end faces of the multilayer chip 10, the two faces other than the upper surface and the lower surface in the stacking direction are referred to as side faces. The external electrodes 20a and 20b extend to the upper surface, the lower surface, and the 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.

[0097] The multilayer chip 10 has a structure in which dielectric layers 11 containing a dielectric porcelain composition and internal electrode layers 12 containing a base metal material are alternately stacked. The end edges of the respective internal electrode layers 12 are alternately exposed on the end face of the multilayer chip 10 provided with the external electrode 20a and the end face of the multilayer chip 10 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 with the internal electrode layers 12 interposed therebetween. In addition, in the laminate of the dielectric layer 11 and the internal electrode layer 12, an internal electrode layer 12 is disposed on the outermost layer in the stacking direction, and the upper surface and the lower surface of the laminate are covered with a covering layer 13. The covering layer 13 is mainly composed of a ceramic material. For example, the material of the covering layer 13 is the same as the main component of the ceramic material of the dielectric layer 11.

[0098] The dimensions of the multilayer ceramic capacitor 100 are, 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 are not limited to these dimensions.

[0099] The internal electrode layer 12 is mainly composed of a base metal such as nickel (Ni), copper (Cu), or tin (Sn). As the internal electrode layer 12, a noble metal such as platinum (Pt), palladium (Pd), silver (Ag), or gold (Au) or an alloy containing them may also be used.

[0100] As Figure 6As illustrated, 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 in the multilayer ceramic capacitor 100. Therefore, this capacitance-generating region 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.

[0101] The region where the internal electrode layers 12 connected to the external electrode 20a do not face each other across the region where the internal electrode layer 12 connected to the external electrode 20b is located is referred to as the end edge 15. In addition, the region where the internal electrode layers 12 connected to the external electrode 20b do not face each other across the region where the internal electrode layer 12 connected to the external electrode 20a is located is also the end edge 15. That is, the end edge 15 is the region where the internal electrode layers 12 connected to the same external electrode do not face each other across the region where the internal electrode layer 12 connected to a different external electrode is located. The end edge 15 is a region where no capacitance is generated.

[0102] As Figure 7 illustrated, in the laminate sheet 10, the region from both side surfaces of the laminate sheet 10 to the internal electrode layer 12 is referred to as the side edge 16. That is, the side edge 16 is a region provided in such a manner as to cover the end portions of the plurality of internal electrode layers 12 laminated in the above-described laminated structure and extending to both side surfaces. The side edge 16 is also a region where no capacitance is generated.

[0103] In the multilayer ceramic capacitor 100 of the present embodiment, at least a part of the dielectric layer 11 in the capacitance region 14 contains Figure 1 the dielectric particles 41 illustrated in [ ], and contains the oxide 42. Thereby, it is possible to suppress the change in capacitance caused by the firing temperature, and it is possible to improve the insulation property in a wide firing atmosphere. As a result, high mass productivity can be obtained.

[0104] Next, a method for manufacturing the multilayer ceramic capacitor 100 will be described. Figure 8 is a diagram illustrating the flow of a method for manufacturing the multilayer ceramic capacitor 100.

[0105] (Raw material powder production process)

[0106] First, prepare a dielectric porcelain composition for forming the dielectric layer 11. The A-site element and 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 with a perovskite structure that belongs to the tetragonal system near room temperature and exhibits a high relative dielectric constant. This barium titanate can usually be synthesized by reacting a titanium raw material such as titanium dioxide with 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 methods have been known in the past. For example, the solid-phase method, sol-gel method, hydrothermal method, etc. are known. In the present embodiment, any of these methods can be adopted.

[0107] Add a prescribed additive to the barium titanate powder obtained by the above method. As an example, additives within the range shown in the example of the dielectric porcelain composition of the first embodiment can be 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) can be used.

[0108] For example, a compound containing an additive compound is wet-mixed with the barium titanate powder, and then dried and pulverized to prepare a ceramic material in which the barium titanate powder and the additive compound are mixed. For example, for the ceramic material obtained as described above, the particle size can be adjusted by performing a pulverization treatment as needed, or by combining with a classification treatment. Specifically, the particle size can be adjusted by stirring the ceramic material together with beads made of yttrium-stabilized zirconia, alumina, or silicon nitride with a diameter of 0.1 mm to 3 mm for 10 hours to 100 hours. Through the above procedures, a dielectric porcelain composition is obtained.

[0109] (Coating process)

[0110] Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol and 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, for example, by a die coating method or a doctor blade method, and dried. The substrate is, for example, a polyethylene terephthalate (PET) film. The figure illustrating the coating process is omitted.

[0111] (Internal electrode formation process)

[0112] Next, as Figure 9As exemplified in (a) of , a metal conductive paste for forming an internal electrode containing an organic binder is printed on the surface of the green ceramic sheet 51 by screen printing, gravure printing, etc., thereby disposing an internal electrode pattern 52 that is alternately led out to a pair of external electrodes with different polarities. Ceramic particles are added as a co-material to the metal conductive paste. The main component of the ceramic particles is not particularly limited, and is preferably the same as the main component ceramic of the dielectric layer 11. For example, calcium barium titanate with an average particle size of 50 nm or less can be uniformly dispersed.

[0113] Next, in the dielectric porcelain composition obtained in the raw material powder manufacturing process, a binder such as ethyl cellulose and an organic solvent such as terpineol are added, and kneaded with a roll mill to obtain a dielectric pattern paste for the anti-pattern layer. As Figure 9 As exemplified in (a) of , on the green ceramic sheet 51, the dielectric pattern paste is printed in the peripheral area where the internal electrode pattern 52 is not printed to dispose a dielectric pattern 53, filling the step difference with the internal electrode pattern 52. The green ceramic sheet 51 printed with the internal electrode pattern 52 and the dielectric pattern 53 is called a stack unit.

[0114] After that, as Figure 9 As exemplified in (b) of , the stack units are stacked in such a way that the internal electrode layer 12 and the dielectric layer 11 are interleaved, and the end edges of the internal electrode layer 12 are alternately exposed on both end faces in the length direction of the dielectric layer 11 and are alternately led out to a pair of external electrodes 20a, 20b with different polarities. For example, the number of stacked internal electrode patterns 52 is 100 to 1000 layers.

[0115] (Pressing process)

[0116] As Figure 10 As exemplified in , cover sheets 54 are stacked on the top and bottom of the laminate obtained by stacking the stack units in a specified number (e.g., 2 to 10 layers) and hot-pressed. As the ceramic material of the cover sheet 54, as an example, the above-mentioned dielectric porcelain composition can be used. Then, it is cut into a specified chip size (e.g., 1.0 mm × 0.5 mm).

[0117] (Firing process)

[0118] After subjecting the ceramic laminate obtained as described above to a debinding treatment in an N2 atmosphere, an air atmosphere, etc., a metal paste that becomes the base layer of the external electrodes 20a, 20b is applied by an impregnation method, and the oxygen partial pressure is 10 -10 ~10 -7In a reducing atmosphere of 1 atm, it is held at 800 °C to 1100 °C for 10 minutes to 1 hour and then fired at 1150 to 1300 °C for 10 minutes to 2 hours. Through this, the multilayer ceramic capacitor 100 is obtained.

[0119] (Re-oxidation treatment process)

[0120] After that, re-oxidation treatment can be performed at 600 °C to 1000 °C in an N2 gas atmosphere.

[0121] (Plating treatment process)

[0122] After that, on the base layers of the external electrodes 20a and 20b, metal coatings such as Cu, Ni, and Sn are applied by plating treatment. Through the above processes, the multilayer ceramic capacitor 100 is completed.

[0123] The side edge portions can be pasted or coated on the side surfaces of the above-mentioned laminated portions. Specifically, as Figure 11 illustrated, by alternately laminating the ceramic green sheet 51 and the internal electrode pattern 52 having the same width as the ceramic green sheet 51, a laminated portion is obtained. Then, a sheet formed of a dielectric pattern paste is pasted on the side surface of the laminated portion as the side edge portion 55.

[0124] According to the manufacturing method of the present embodiment, in a reducing atmosphere with an oxygen partial pressure of 10 -10 to 10 -7 atm, it is held at 800 to 1100 °C for 10 minutes to 1 hour. Thus, the added rare earth element R and titanium form a compound R2Ti2O7 having a pyrochlore structure or a perovskite-type structure. After that, when the temperature is raised to 1100 °C to 1300 °C, it reacts with the surface of the barium titanate grains and forms a shell portion 412 in the form of a composite perovskite compound such as R(Ti, Mn)O3. It is possible to form at least a part of the dielectric layer 11 in the capacitance region 14 Figure 1 illustrated dielectric particles 41, and oxides 42 can be included. Therefore, it is possible to suppress the change in capacitance caused by the firing temperature. As a result, high mass productivity can be obtained.

[0125] The firing temperature dependence (Δε / °C) of the relative dielectric constant caused by the change in the firing temperature of the multilayer ceramic capacitor 100 can be determined by the following method. First, the capacitance Cp (nF) and the direct current I (nA) of the multilayer ceramic capacitor 100 that has undergone the firing process, the re-oxidation treatment process, and the plating treatment process are measured. Then, for this multilayer ceramic capacitor 100, for Figure 6 and Figure 7For the cross-sections along line A-A and line B-B illustrated in [the relevant figure], the capacitance region 14 is exposed by means such as cutting or grinding. When a smoothness that can be judged as mirror-like is obtained using diamond paste of 2 μm or less in the end, the effective area of the internal electrode layer is calculated.

[0126] The effective area S is based on Figure 6 the length L and the number of layers N of the internal electrode layer 12 in the capacitance region 14 in [the relevant figure], and Figure 7 the width W of the internal electrode layer 12 in the capacitance region 14 in [the relevant figure], and is calculated as S = L × W × (N - 1).

[0127] In addition, at this time, the thicknesses of the dielectric layers 11 are also measured respectively, and the average thickness t is calculated. At this time, the relative dielectric constant ε can be calculated as ε = (Cp × t / S) / ε0, where the dielectric constant of vacuum: ε0 = 8.8542×10 -12 F / m.

[0128] In addition, for the DC resistivity ρ (Ω·cm), when the DC voltage during measurement is V (V), it can be calculated as ρ = (V / I) × (S / t).

[0129] Regarding the capacitance Cp, it is usually preferably measured using an LCR meter. During measurement, it is necessary to determine its measurement frequency and measurement voltage. 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, the measurement frequency can be set to 1 kHz, and when the measurement electric field is 0.5 Vrms / μm, that is, when the thickness of the dielectric layer 11 is 2 μm, it is set to 1 Vrms, and the capacitance Cp is measured.

[0130] And regarding the DC current I, it is usually preferably measured using an insulation resistance meter. During measurement, it is necessary to determine the measurement voltage, and it is preferably determined as a measurement electric field depending on the thickness of the dielectric layer 11. In this embodiment, in a thermostat at 150°C, the multilayer ceramic capacitor 100 is held for 30 minutes, and insulation from the surroundings is ensured using a ceramic insulator or the like. Through the wires connected from the thermostat to the external electrodes 20a and 20b, a measurement electric field of 30 V / μm is applied (for example, when the thickness of the dielectric layer 11 is 2 μm, 60 V is applied for 30 seconds), and the DC current I is measured to calculate the DC resistivity ρ. In addition, regarding the measurement, unless otherwise specified, it is carried out in accordance with Japanese Industrial Standard C5101-22:2021, Fixed capacitors for electronic equipment - Part 22: General rules by type - Fixed multilayer ceramic surface mount capacitors, type 2.

[0131] Next, the multilayer ceramic capacitors with the DC resistivity ρ obtained at each firing temperature are measured, and the firing temperature that maintains the highest resistivity is taken as the optimum firing temperature. Generally, when the firing temperature is too low, it becomes low density and low resistivity, and when the firing temperature is too high, the ceramic particles become larger and the number of grain boundaries becomes smaller, so that a decrease in resistivity occurs.

[0132] Next, based on the relative dielectric constant ε of the multilayer ceramic capacitor obtained at the firing temperature that maintains the highest resistivity and the firing temperature that maintains its highest resistivity, and based on the relative dielectric constants of the multilayer ceramic capacitors fired at the firing temperatures of -20°C and +20°C, using these firing temperatures and relative dielectric constants, the slope of the straight line is obtained by the least squares method, and its value is determined as the firing temperature dependence (Δε / °C) of the relative dielectric constant, as an index of high mass productivity.

[0133] The DC resistivity measured at 150°C is preferably 1.0×10 8 Ω·cm or more. By being 1.0×10 8 Ω·cm or more, in the multilayer ceramic capacitor 100 using the dielectric porcelain composition of the present embodiment, sufficient resistance can be obtained.

[0134] The DC resistivity measured at 150°C is more preferably 1.0×10 10 Ω·cm or more. This is because, by being 1.0×10 10 Ω·cm or more, in the multilayer ceramic capacitor 100 using the dielectric porcelain composition of the present embodiment, not only sufficient resistance is obtained, but also the thickness can be more easily designed thinner, and the number of internal electrodes to be laminated can be increased.

[0135] Δε / °C is preferably 10 or less. When it becomes 10 or less, in the multilayer ceramic capacitor 100 using the dielectric porcelain composition of the present embodiment, firing can be performed in a shorter time, and at the same time, changes in capacitance due to changes in firing temperature can be suppressed, and high mass productivity can be obtained.

[0136] The relative dielectric constant ε is preferably 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 Δε / °C of the relative dielectric constant is 12 or less, if ε is small, as a result, the capacitance Cp will also become an insufficient value, and it will also become a characteristic unsuitable for the use of the multilayer ceramic capacitor 100 using the dielectric porcelain composition.

[0137] In addition, in each of the above-described embodiments, a multilayer ceramic capacitor has been described as an example of the multilayer ceramic electronic component, but the present invention is not limited thereto. For example, other multilayer ceramic electronic components such as varistors or thermistors may also be used.

[0138] [Examples]

[0139] (Example 1)

[0140] Prepare barium titanate (BaTiO3) powder with an average particle size of 200 nm. To 100 mol of the barium titanate powder, add 0.75 mol of Gd2O3, add 1.50 mol of TiO2, add 1.00 mol of MnCO3, add 1.00 mol of SiO2, and add 0.50 mol of MgO to obtain a dielectric porcelain composition.

[0141] Mix the dielectric porcelain composition with ethanol, toluene, and PVB (polyvinyl butyral) resin to prepare a dielectric slurry. Form the slurry into a ceramic green sheet using a doctor blade coater. After drying the ceramic green sheet, print a nickel paste to form an internal electrode pattern. Stack the obtained stacked unit layers, press-bond the layers obtained by thickly stacking the ceramic green sheets without forming an internal electrode pattern on the top and bottom, and cut them into small pieces. Then, dip the two end faces in a Ni paste as a conductive paste for the external electrode, and degrease in nitrogen. Sinter the degreased small pieces in a reducing atmosphere with an oxygen partial pressure controlled so that nickel does not oxidize to fabricate a multilayer ceramic capacitor. The firing is maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1240 °C for 10 minutes.

[0142] The fabricated multilayer ceramic capacitor has a size of 1005 (1.0 mm × 1.0 mm × 0.5 mm). Then, perform a re-oxidation treatment at 950 °C. Then, perform a plating treatment to form a Cu plating layer, a Ni plating layer, and a Sn plating layer on the surface of the base layer to obtain a multilayer ceramic capacitor. The average thickness of the dielectric layer 11 is 2.0 μm.

[0143] (Example 2)

[0144] In Example 2, to 100 mol of the barium titanate powder, add 0.75 mol of La2O3, add 1.50 mol of TiO2, add 1.00 mol of MnCO3, add 1.00 mol of SiO2, and add 0.50 mol of MgO to obtain a dielectric porcelain composition. The firing is maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1220 °C for 10 minutes. Other conditions are the same as those in Example 1.

[0145] (Example 3)

[0146] In Example 3, with respect to 100 mol of barium titanate powder, 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 obtain a dielectric porcelain composition. The firing was maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1230 °C for 10 minutes. Other conditions were the same as in Example 1.

[0147] (Example 4)

[0148] In Example 4, with respect to 100 mol of barium titanate powder, 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 obtain a dielectric porcelain composition. The firing was maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1230 °C for 10 minutes. Other conditions were the same as in Example 1.

[0149] (Example 5)

[0150] With respect to 100 mol of barium titanate powder, 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 obtain a dielectric porcelain composition. The firing was maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1240 °C for 10 minutes. Other conditions were the same as in Example 1.

[0151] (Example 6)

[0152] With respect to 100 mol of barium titanate powder, 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 obtain a dielectric porcelain composition. The firing was maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1240 °C for 10 minutes. Other conditions were the same as in Example 1.

[0153] (Example 7)

[0154] With respect 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 maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1250 °C for 10 minutes. Other conditions were the same as in Example 1.

[0155] (Example 8)

[0156] With respect to 100 mol of barium titanate powder, 0.75 mol of Gd2Ti2O7 is added, 1.00 mol of MnCO3 is added, 1.00 mol of SiO2 is added, and 0.50 mol of MgO is added to obtain a dielectric porcelain composition. The firing is maintained at a temperature of 1240 °C for 10 minutes. Other conditions are the same as in Example 1.

[0157] (Example 9)

[0158] In Example 9, with respect to 100 mol of barium titanate powder, 0.75 mol of Er2O3 is added, 1.50 mol of TiO2 is added, 1.00 mol of MnCO3 is added, 1.00 mol of SiO2 is added, and 0.50 mol of MgO is added to obtain a dielectric porcelain composition. The firing is maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1270 °C for 10 minutes. Other conditions are the same as in Example 1.

[0159] (Example 10)

[0160] In Example 10, with respect to 100 mol of barium titanate powder, 0.75 mol of Yb2O3 is added, 1.50 mol of TiO2 is added, 1.00 mol of MnCO3 is added, 1.00 mol of SiO2 is added, and 0.50 mol of MgO is added to obtain a dielectric porcelain composition. The firing is maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1270 °C for 10 minutes. Other conditions are the same as in Example 1.

[0161] (Comparative Example 1)

[0162] In Comparative Example 1, with respect to 100 mol of barium titanate powder, 0.75 mol of Gd2O3 is added, 1.00 mol of MnCO3 is added, 1.00 mol of SiO2 is added, and 0.50 mol of MgO is added to obtain a dielectric porcelain composition. The firing is maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1260 °C for 10 minutes. Other conditions are the same as in Example 1.

[0163] (Comparative Example 2)

[0164] In Comparative Example 2, with respect to 100 mol of barium titanate powder, 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 obtain a dielectric porcelain composition. The firing was maintained at a temperature of 1000 °C for 10 minutes and at a temperature of 1250 °C for 10 minutes. Other conditions were the same as in Example 1.

[0165] For each of the multilayer ceramic capacitors of Examples 1 to 10 and Comparative Examples 1 to 2, the capacitance Cp at 1 kHz, 1 Vrms, and room temperature (25 °C) 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. In addition, Figure 5 the cross-sections of line A-A and line B-B were exposed, and the effective area S of the internal electrode layer and the average thickness t of the dielectric layer were calculated. The relative dielectric constant ε and the resistivity ρ were calculated based on the effective area S and the average thickness t. 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 dielectric constants of the multilayer ceramic capacitors obtained by firing the multilayer ceramic capacitors at the firing temperature with the highest resistivity at -20 °C and +20 °C, based on these firing temperatures and relative dielectric constants, the slope of the straight line was obtained by the least squares method and defined as the firing temperature dependence (Δε / °C) of the relative dielectric constant.

[0166] Furthermore, a conductive substance of osmium was vapor-deposited on the exposed dielectric layer, and photographs of the crystal grains present in the dielectric layer were taken by SEM observation. Then, the average grain size of the crystal grains constituting the dielectric layer was calculated. The average grain size 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.

[0167] In addition, when observing the multilayer ceramic capacitor by SEM, in the BSE image, the presence of the oxide 42 was confirmed based on the difference in brightness.

[0168] Then, for each multilayer ceramic capacitor, in order to confirm the shell part and the core part in the crystal grains of the dielectric layer and the composition of the oxide 42, a sample for EDS observation by TEM was cut out using FIB, and the confirmation of whether there is a core-shell structure was carried out by the method of composition evaluation using EDS. The part with an R / Ti element ratio less than 0.02 was regarded as the core part, and the part with an R / Ti element ratio of 0.02 or more and less than 0.20 was regarded as the shell part. In addition, for the oxide 42, the element ratio of the rare earth element R to titanium was also confirmed to confirm whether the R / Ti element ratio was 0.20 or more.

[0169] In addition, for each multilayer ceramic capacitor, after separating the cover layer, end edge, side edge, and external electrode outside the capacitance region by grinding or cutting, for the powder obtained by pulverizing the dielectric layer constituting the capacitance region, the diffraction line profile was measured using an X-ray diffractometer (XRD) using Cu-Kα rays to confirm whether there was an oxide 42 that could be identified by R2Ti2O7.

[0170] The addition amounts of the additives in Comparative Examples 1 to 2 and Examples 1 to 10 are summarized in Table 1. The firing temperatures, average particle sizes, ε, Δε / °C, and resistivity at 150°C in Comparative Examples 1 to 2 and Examples 1 to 10 are summarized in Table 2. As the judgment of whether it is qualified, the case where Δε / °C is 10 or less and the resistivity is 1.0×10 9 Ω·cm or more was judged as qualified "○", the case where Δε / °C was 10 or less was judged as "△", and the case where it was not satisfied was judged as unqualified "×".

[0171] [Table 1]

[0172]

[0173] [Table 2]

[0174]

[0175] Comparative Examples 1 and 2 are comparative examples in the case of containing gadolinium as the rare earth element. In Comparative Examples 1 and 2, since gadolinium was contained as the rare earth element, the average particle sizes became 550 nm and 410 nm. As a result, the resistivity at 150°C became 1.9×10 8 Ω·cm, and a sufficient resistivity could be maintained. However, because the addition amount of TiO2 was not sufficient, the value of Δε / °C was greater than 10, and a preferable value of 10 or less could not be obtained.

[0176] In Examples 1 to 7, 9, and 10, with respect to 100 mol of BaTiO3, the addition amount of added TiO2 was 1.5 mol, and 0.75 mol of lanthanum, praseodymium, neodymium, europium, gadolinium, dysprosium, holmium, erbium, and ytterbium were added as rare earth elements, respectively. In Example 8, with respect to 100 mol of BaTiO3, 0.75 mol of Gd2Ti2O7 was added. In the case of this composition, the value of Δε / °C was 10 or less. For example, even when using a firing furnace larger than the existing one to improve production efficiency, the dielectric constant obtained with respect to the temperature distribution in the furnace, that is, the value of the electrostatic capacitance Cp as a multilayer ceramic capacitor, does not have a large distribution. Therefore, even in firing carried out at a high heating rate in a short time, a larger quantity can be produced. In addition, when the rare earth element is europium, gadolinium, dysprosium, or holmium, ε is 3000 or more. In addition, the average particle size is also 500 nm or less, and the resistivity is also 1.0×10 9 Ω·cm or more.

[0177] In order to investigate the mechanism of the dielectric layer in detail, using STEM-EDS, for the multilayer ceramic capacitors obtained in Comparative Examples 1 and 2 and Examples 1 to 10 above, it was investigated whether there is a core-shell structure, whether there is Oxide 42, 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 the rare earth element R to Ti is in the range of 0.40≤w. The results are summarized in Table 3.

[0178] [Table 3]

[0179]

[0180] In Comparative Examples 1 and 2, the addition amount of TiO2 was insufficient. Therefore, in the SEM-BSE image, the presence of Oxide 42, which has a relatively high brightness and looks brighter compared to the main grains composed of barium titanate, could not be confirmed.

[0181] On the other hand, in Examples 1 to 10, the element ratio w of the rare earth element R to Ti in Oxide 42 was in the range of 0.2≤w, whereby the presence of Oxide 42 was also clarified. In addition, in Examples 1 to 8, Oxide 42 did not contact the nuclei of multiple particles. Moreover, as shown in Table 1, the value of Δε / °C was 10 or less, and the resistivity was also 1.0×10 8Above Ω·cm, and having a size with an average particle diameter of 500 nm or less and a dielectric constant ε of 2000 or more. Therefore, for example, even when using a firing furnace larger than the existing one to improve production efficiency, the relative dielectric constant obtained with respect to the temperature distribution in the furnace, that is, the value of the electrostatic capacitance Cp as a multilayer ceramic capacitor, does not have a large distribution. Therefore, even when firing is performed in a short time by rapid heating, a larger quantity can be produced, and sufficient reliability can be obtained.

[0182] Above, the embodiments of the present invention have been described in detail, but the present invention is not limited to these specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. A multilayer ceramic electronic component, characterized in that, having: a plurality of internal electrode layers facing each other; a dielectric layer disposed so as to be sandwiched between the plurality of internal electrode layers, the dielectric layer including dielectric particles having a perovskite structure represented by the general formula ABO3, the dielectric particles having a core portion, a shell portion, and an oxide, the shell portion covering the core portion and containing a rare earth element, the oxide segregating inside the shell portion, and the concentration of the rare earth element in the oxide being higher than the concentration of the rare earth element in the shell portion; and external electrodes electrically connected to the plurality of internal electrode layers.

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

3. The multilayer ceramic electronic component according to claim 1 or 2, wherein: the A site of the perovskite structure contains barium, and the element contained in the B site of the perovskite structure is at least one element of titanium and zirconium.

4. The multilayer ceramic electronic component according to any one of claims 1 to 3, wherein: the rare earth element is composed of at least one element selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, and erbium.

5. The multilayer ceramic electronic component according to any one of claims 1 to 4, wherein: the element ratio of the rare earth element in the shell portion to titanium is 0.02 or more and less than 0.

20.

6. The multilayer ceramic electronic component according to any one of claims 1 to 5, wherein: the element ratio of the rare earth element in the oxide to titanium is 0.20 or more.

7. The multilayer ceramic electronic component according to any one of claims 1 to 6, wherein: the oxide is enclosed inside the shell portion.

8. The multilayer ceramic electronic component according to any one of claims 1 to 7, wherein: the oxide contacts a part of the core portion.

9. The multilayer ceramic electronic component according to any one of claims 1 to 8, wherein: the oxide contacts a part of the grain boundary of the dielectric particles.

10. The multilayer ceramic electronic component according to any one of claims 1 to 9, wherein: the oxide extends from a part of the core portion to a part of the grain boundary of the dielectric particles.

11. The multilayer ceramic electronic component according to any one of claims 1 to 10, wherein: in the shell portion, a plurality of the oxides are present at intervals.

12. The multilayer ceramic electronic component according to any one of claims 1 to 11, wherein: the plurality of dielectric particles are adjacent to each other across grain boundaries, and the oxide does not connect the core portions of the plurality of dielectric particles.

13. The multilayer ceramic electronic component according to any one of claims 1 to 12, wherein: the oxide does not contact the core portion.

14. The multilayer ceramic electronic component according to any one of claims 1 to 13, wherein: the maximum particle size of the dielectric particles is 2 μm or less.

15. The multilayer ceramic electronic component according to any one of claims 1 to 14, wherein: the shell portion contains magnesium and manganese.

16. A dielectric porcelain composition, characterized in that: it contains dielectric particles having a perovskite structure represented by the general formula ABO3, the dielectric particles having a core portion, a shell portion and an oxide, the shell portion covering the core portion and containing a rare earth element, the oxide segregating inside the shell portion, and the concentration of the rare earth element in the oxide being higher than the concentration of the rare earth element in the shell portion.

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