ELECTRONIC MULTI-LAYER CERAMIC DEVICE AND CERAMIC DIELECTRIC COMPOSITION

Abstract

A multilayer ceramic electronic device comprises a dielectric layer having a dielectric grain including a core portion, a shell portion surrounding the core portion and including a rare earth element, and an oxide deposited within the shell portion and having a higher concentration of the rare earth element than the shell portion, and having a perovskite structure represented by the general formula ABO3, a plurality of inner electrode layers surrounding the dielectric layer and facing each other, and a plurality of outer electrodes, each of which is electrically coupled to each of the plurality of inner electrode layers.

Description

AREA

[0001] A particular aspect of the present disclosure relates to a multilayer ceramic electronic device and a ceramic dielectric composition. BACKGROUND

[0002] In high-frequency communication systems, such as mobile phones, multilayer ceramic electronic components, such as multilayer ceramic capacitors (MLCCs), are used to eliminate noise. SUMMARY OF THE INVENTION

[0003] According to one aspect of the embodiments, there is provided a multilayer ceramic electronic device comprising: a dielectric layer comprising a dielectric grain having a core portion, a shell portion surrounding the core portion and comprising a rare earth element, and an oxide deposited within the shell portion and having a higher concentration of the rare earth element than the shell portion, and having a perovskite structure represented by the general formula ABO3; a plurality of internal electrode layers surrounding the dielectric layer and facing each other; and a plurality of external electrodes, each of which is electrically coupled to each of the plurality of internal electrode layers.

[0004] According to another aspect of the embodiments, there is provided a ceramic dielectric composition comprising: a dielectric grain comprising a core portion, a shell portion surrounding the core portion and comprising a rare earth element, and an oxide deposited within the shell portion and having a higher concentration of the rare earth element than the shell portion, and having a perovskite structure represented by the general formula ABO3. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a ceramic dielectric composition according to a first embodiment; Fig. 2 shows a unit grid; Fig. 3 shows a method for confirming a core-shell structure; Fig. 4A to Fig. 4E show a form of oxides; Fig.5 is a perspective view of a multilayer ceramic capacitor showing a cross section of a portion of the multilayer ceramic capacitor; Fig. 6 is a cross-sectional view taken along the line AA in the Fig. 5; Fig. Figure 7 is a cross-sectional view taken along line BB in the Fig. 5; Fig. 8 shows a manufacturing process of a multilayer ceramic capacitor; Fig. 9A and Fig. 9B shows a forming process of an inner electrode; Fig. 10 shows a squeezing process; and Fig. 11 shows a case with a side margin section. DETAILED DESCRIPTION

[0005] In recent years, the use of multilayer ceramic electronic devices has expanded even in electronic circuits that affect human life, such as electronic control devices in vehicles. High reliability is required, while at the same time, higher mass production is required in terms of delivery volume.

[0006] The ceramic dielectric composition used in the dielectric layer of multilayer ceramic electronic devices utilizes a sintered body with a core-shell structure in which barium titanate is used as the core and surrounded by a shell in which various additives are dissolved as a solid solution. With this structure, the large electrostatic capacitance near the Curie temperature, which is approximately 125°C and at which barium titanate changes from the ferroelectric phase to the paraelectric phase, can be transferred to a lower temperature in the shell portion due to the effect of the various additives. Therefore, a device can be designed that can increase the electrostatic capacitance in the practical temperature range around room temperature.

[0007] The core-shell structure is believed to be formed by solid-solving various additives in barium titanate. It is believed that the core-shell structure is formed by the reaction of various additives added to the barium titanate particles, the main component, in the firing temperature range of, for example, 1000°C to 1400°C. Generally, as the firing temperature increases, the various additives are solid-solved, and the shell portion becomes thicker. Therefore, to maintain the electrostatic capacity of the multilayer ceramic electronic device within the required range, it is necessary to precisely control or adjust the solid solution formation of the various additives.

[0008] For example, Japanese Patent Application Publication No. 2016-124779 and Japanese Patent Application Publication No. 2011-210783 disclose a ceramic dielectric composition, a dielectric material, and a multilayer ceramic capacitor containing the same, which contain a barium titanate-based main component and a minor component, and in which the relative intensity of the pyrochlore phase containing rare earth elements is controlled in an X-ray diffraction (XRD) analysis after sintering.

[0009] In recent years, the applications of ceramic dielectric compositions and multilayer ceramic electronic devices have expanded, requiring higher mass productivity. To this end, it is necessary to prevent changes in electrostatic capacity due to firing temperature and reduce fluctuations in electrostatic capacity due to temperature.

[0010] An exemplary embodiment will be described below with reference to the accompanying drawings.

[0011] (First Embodiment) A ceramic dielectric composition according to a first embodiment is a polycrystalline ceramic body comprising crystal grains having a perovskite structure represented by the general formula ABO3 as described in Fig. 1. At least one of these polycrystalline ceramic grains is a dielectric grain 41 having a core-shell structure.

[0012] The dielectric grain 41 has a roughly spherical core portion 411 and a shell portion 412 surrounding and covering the core portion 411. The core portion 411 is a crystalline portion in which the additional compound is not dissolved or in which the amount of dissolved additional compound is small. The shell portion 412 is a crystalline portion in which the additional compound is dissolved and has a higher concentration of the additional compound than the concentration of the additional compound of the core portion 411. In this embodiment, the shell portion 412 contains a rare earth element R. The rare earth element R is not specifically limited but may be lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), or the like.The element concentration of the rare earth element R in the cladding portion 412 is greater than the element concentration of the rare earth element in the core portion 411.

[0013] In the cladding portion 412, oxides 42 having a higher concentration of the rare earth element R are deposited than in the shell portion 412. The number of oxides 42 is not specifically limited. However, in a cross-sectional view, the cross-sectional area of the cladding portion 412 is larger than the total cross-sectional area of the oxides 42.

[0014] The ceramic dielectric composition of this embodiment contains the dielectric grain 41 and the oxide 42 and, as a result, has very good insulating properties and can prevent variations in electrostatic capacity with respect to the firing temperature.

[0015] For example, when a cross section of the ceramic dielectric composition is examined in a region where a total of 100 or more of the dielectric grains 41 and the oxides 42 can be confirmed, the area ratio of the dielectric grains 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.

[0016] Crystal grains with a perovskite structure, which are the main component of the dielectric grains 41, have a unit cell as shown in the Fig.2. This unit cell has an A position located at the vertex of the lattice, an O position located at the face center of the lattice, and a B position located within an octahedron with the O position as the vertex. In the perovskite structure, alkaline earth metals that can provide divalent cations, such as barium (Ba), strontium (Sr), or calcium (Ca), are located at the A position, and hafnium (Hf), zirconium (Zr), or titanium (Ti), which can provide tetravalent cations, are located at the B position.

[0017] The perovskite structure also allows for a composition formula that deviates from the stoichiometric composition. That is, the ratio of the element at position A to the element at position B does not necessarily have to be 1:1, and defects can be created within a range where the perovskite structure can be maintained. Furthermore, defects can also be created with respect to oxygen. For example, if the composition formula is A α BO 3-β compositions in the ranges of 0.98 ≤ α ≤ 1.01 and 0 ≤ β ≤ 0.20 are permitted.

[0018] However, due to the generation of oxygen vacancies, for example, the resistivity decreases and ionic conductivity occurs, which reduces the electrical lifetime when used as a multilayer ceramic capacitor and increases the dielectric loss. For this reason, the dielectric grain 41 having a perovskite structure may contain 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), or zinc (Zn). This enables the improvement of the resistivity, the increase of the electrical lifetime, and the reduction of the dielectric loss due to electrostatic capacitance.

[0019] The dielectric grain 41 may also contain at least one of the second transition elements yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), or silver (Ag). This can improve resistivity, increase electrical lifetime, and reduce dielectric loss relative to electrostatic capacitance.

[0020] The dielectric grain 41 may also contain at least one of the third transition elements 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), or gold (Au). This can improve resistivity, increase electrical lifetime, and reduce dielectric loss relative to electrostatic capacitance.

[0021] 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), or holmium (Ho), is preferably added to the ceramic dielectric composition. An additive containing titanium is also preferably added to the ceramic dielectric composition 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 a case where an additive containing titanium is not added, the solid solution reaction with barium titanate crystal particles is relatively reduced. This effect enables firing to be achieved in a shorter time while reducing the rate of change in electrostatic capacity due to changes in firing temperature, and maintaining high mass productivity.

[0022] Preferred additives containing the above 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) or holmium oxide (Ho2O3).

[0023] Preferred additives containing the above-mentioned titanium include titanium oxide, but titanium hydroxide (Ti(OH)4), titanium chloride (TiCl4), titanium carbide (TiC), and titanium sulfide (TiS2) or the like may also be used.

[0024] The additional material containing the rare earth element R and titanium is e.g. La2Ti2O7, Ce2Ti2O7, Pr2Tb2O7, Nd2Ti2O7, Pm2Ti2O7, Sm2Ti2O7, Eu2Ti2O7, Gd2Ti2O7, Tb2Ti2O7, Dy2Ti2O7 or Ho2Ti2O7.

[0025] In addition to adding the rare earth element R to the ceramic dielectric composition, it is preferable to add 0.2 mol or more and 5.0 mol or less of manganese oxide (MnO) to 100 mol of barium titanate so that the Mn / Ti element ratio z, which is the ratio of the number of the element manganese to the number of the element titanium, is 0.002 ≦ z ≦ 0.05.

[0026] Generally, in a core-shell structure, with increasing sintering temperature, various additives tend to dissolve in larger amounts in the crystal grains made of barium titanate, resulting in a thicker shell. In the shell portion, the region of large electrostatic capacitance approaches room temperature near 125°C, which is close to the Curie temperature of barium titanate. As a result, the electrostatic capacitance in the practical temperature range near room temperature varies greatly depending on the thickness of the shell portion. Therefore, for example, to maintain the electrostatic capacitance of a multilayer ceramic capacitor within a desired range, it is preferable to precisely control the sintering temperature.

[0027] For example, the ceramic dielectric composition according to this embodiment can be obtained by maintaining the temperature at 900 °C to 1100 °C, then firing at 1150 °C to 1300 °C, and rapidly increasing the temperature during the firing process at a rate of 3000 °C / hour to 10000 °C / hour.

[0028] The dielectric grains 41 having a core-shell structure in which the shell portion 412 containing a rare earth element is formed are formed by a process different from that of conventional core-shell structures. Specifically, not only is the rare earth element R introduced as a solid solution into the crystal grains made of barium titanate, but the added rare earth element R and titanium form compounds such as R2Ti2O7, which is a compound having a pyrochlore structure or a perovskite plate structure, and then react with the surface of the barium titanate crystal grains to form the shell portion 412 in the form of a perovskite mixed compound such as R(Ti,Mn)O3. This prevents excessive solid solution reaction of the rare earth element R in the shell portion 412 and reduces the rate of change in electrostatic capacitance due to changes in firing temperature.As an indication of the process of forming the shell portion 412, an oxide region is formed with a higher concentration of the rare earth element R than in the shell portion. The reaction of forming R2Ti2O7 takes place between 900°C and 1100°C.

[0029] To promote this shell formation reaction, it is preferable that the rare earth element R be an element that readily solidifies at the A position of ABO3. Specifically, it is preferable that the rare earth element R be, for example, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), or holmium (Ho), which has a larger ionic radius than erbium (Er).

[0030] On the other hand, if a rare earth element R (erbium, thulium, ytterbium, ruthenium) is used, which has an ionic radius smaller than that of holmium, a compound with a pyrochlore structure R2Ti2O7 is produced. However, the shell formation reaction between R2Ti2O7 and the barium titanate crystal grains does not proceed sufficiently, and there is a risk that the nuclei of several grains may come into electrical contact with the oxide region. As a result, the resistivity decreases, and the compound may become unsuitable for use in multilayer ceramic capacitors.

[0031] According to Yukikuni Akishige and Misako Kamata, "Crystal Chemistry of A2B2O7 Type Oxide Ferroelectrics with Perovskite-related Layered Structure," Memoirs of the Faculty of Education, Shimane University, Natural Science, the smaller the ionic radius of the rare earth element R in R2Ti2O7, the more stable the pyrochlore structure becomes. Therefore, to promote the shell generation reaction, it is preferable to use a rare earth element with a larger ionic radius than erbium (Er), such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), or holmium (Ho).

[0032] In the shell portion 412, the further added magnesium can react on the surface of the barium titanate crystal grains to produce a perovskite mixed compound such as R(Mg,Ti,Mn)O3.

[0033] The perovskite mixed compound, considered as R(Ti,Mn)O3 or R(Mg,Ti,Mn)O3, can react with the surrounding barium titanate crystal grain, which is the main component, to generate (R,Ba)(Ti,Mn)O3 or (R,Ba)(Mg,Ti,Mn)O3 as the shell portion 412.

[0034] For example, the core portion 411 in the core-shell structure is predominantly composed of crystal grains made of barium titanate, but may also contain an added rare earth element, manganese, magnesium, or the like. However, it is sufficient that the shell portion 412 contains relatively more of the rare earth element, manganese, magnesium, or the like than the core portion 411.

[0035] In particular, a crystal grain having a core-shell structure in which a shell containing a rare earth element and manganese is formed with a crystal grain made of barium titanate as a main component can contain a relatively large amount of the rare earth element or manganese compared to the element ratio to titanium in the center at any point within a range of 10% of the diameter of the crystal grain from the surface of the center.The presence of such crystal grains having a core-shell structure not only prevents the change in electrostatic capacitance held by the polycrystalline body constituting the ceramic dielectric composition due to changes in firing temperature, but also prevents the movement of oxygen vacancies at the grain boundaries and within the shell portion, thereby preventing a reduction in resistivity and improving electrical durability.

[0036] The average grain size of the dielectric grains 41 in the ceramic dielectric composition is within the range of 50 nm to 500 nm, and large grains of 3 μm or more are not maintained in the range where they are electrically utilized as a dielectric. For example, in the ceramic dielectric composition, the maximum grain size of the dielectric grains 41 is preferably 2 μm or less. Moreover, considering the general ceramic properties that the distribution of the grain size and composition of the contained crystal grains is within a relatively narrow range, if it can be confirmed that the dielectric grains 41 have a core-shell structure, it can be considered that the presence of many dielectric grains 41 with a similar structure has a beneficial effect on the electrical durability of the ceramic dielectric composition.

[0037] The grain size of the dielectric grains 41 can be measured by the following procedure. The ceramic dielectric composition including the dielectric grains 41 is cut or polished to expose an inspection surface. This exposure method is not particularly limited, and a method of cutting or polishing the element can be used. Finally, to fully examine the internal ceramic structure, it is preferable to 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 material such as platinum or osmium on the inspection surface, the surface is examined with a scanning electron microscope (SEM), and a photograph of the dielectric grains 41 is taken.Next, a plurality of parallel straight lines are drawn in the photograph, and the length of each line segment intersected at the circumference of each dielectric grain 41 (the distance between two points where each straight line intersects the circumference of the dielectric grain 41) is used as the grain diameter (grain size) of the dielectric grains 41. In this method, the grain size of the dielectric grains 41 is measured for 400 or more grains, and the average of the results is used as the average grain size of the dielectric grains 41. In addition, when the outline of the dielectric grains 41 is difficult to discern in the exposed ceramic, it is advisable to perform heat treatment (thermal etching) for about 5 minutes on the exposed ceramic at a temperature about 50°C lower than the firing temperature before the deposition of platinum or osmium.Instead of this heat treatment, chemical etching can also be carried out using hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid or a mixture of these acids at a suitable concentration for etching.

[0038] The presence of dielectric grains 41 with a core-shell structure in the ceramic dielectric composition can be confirmed by the following procedure. It should be noted that the following procedure explains the case where gadolinium is used as the rare earth element as an example.

[0039] First, a sample is cut out of the ceramic dielectric composition for confirmation examination using a transmission electron microscope (TEM). This cutting can be performed using a focused ion beam (FIB) device or the like.

[0040] Then, the cut-out sample is examined for TEM examination using a TEM equipped with an energy dispersive X-ray spectrometer (EDS) or a wavelength dispersive X-ray spectrometer (WDS) to determine the crystal grain to be measured and to identify the outer peripheral shape of the grain.

[0041] Next, as stated in the Fig. 3, the longest line segment connecting any two points located on the outer circumference of the crystal grain to be measured is determined, and the length L of the line segment is measured. This length L is then considered the diameter of the crystal grain to be measured. The center point M of the line segment is also determined from the obtained length of the line segment.

[0042] Composition analysis is performed by EDS or WDS for any point C on the circumference within a range of 10% of the crystal grain diameter, i.e., 10L / 100, from both ends of the line segment to calculate the element abundance ratio between the analyzed element and titanium. In composition analysis, for example, in EDS measurement, the element abundance ratio can be determined by the intensity of the titanium K-line relative to the barium K-line or L-line, the calcium K-line, the gadolinium L-line, the manganese K-line, and the magnesium K-line. Specifically, based on these intensities, a correction (ZAF correction) is performed that takes into account the atomic number effect, the absorption effect, and the fluorescence excitation effect, and the ratio of each element relative to the content of the element titanium is calculated, which is the ratio of each element to titanium in the shell portion 412.A composition analysis is also performed in the same manner for the midpoint M of the line segment and the ratio is calculated, which is the ratio of each element to titanium in the core section 411.

[0043] Next, the ratio of each element to titanium in the shell portion 412 is compared with the ratio of each element to titanium in the core portion 411. If the ratio in the shell portion 412 is higher than that in the core portion 411, it is determined that the measured dielectric grain 41 has a core-shell structure.

[0044] As described above, the ceramic dielectric composition contains, in addition to the dielectric grains 41, at least one oxide having a higher concentration of the rare earth element R than the shell portion 412 than the oxide 42. The element ratio of the rare earth element R in the oxide 42 is higher by 0.20 or more than the B position of the perovskite constituting the dielectric grains 41.

[0045] The oxide 42 is, for example, an oxide in which barium derived from barium titanate is dispersed in a compound having a pyrochlore structure. As described above, since the shell portion 412 in the form of a perovskite mixed compound, which is assumed to be R(Ti,Mn)O3, R(Mg,Ti,Mn)O3, (R,Ba)(Ti,Mn)O3, (R,Ba)(Mg,Ti,Mn)O3, or the like, is formed from an intermediate such as R2Ti2O7, the oxide 42 in the ceramic dielectric composition according to this embodiment is a secondarily generated oxide. By intentionally depositing the oxide 42, the dielectric grains 41 can be obtained and the change in electrostatic capacitance caused by the change in firing temperature can be prevented, whereby high mass productivity can be achieved, for example, for a multilayer ceramic capacitor which is required to have high mass productivity.

[0046] The fact that the ceramic dielectric 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 that used to confirm the presence of the dielectric grains 41 having the core-shell structure as described above.

[0047] When the element ratio of the rare earth element R to the B position of the perovskite constituting the dielectric grain obtained by the above method is higher by 0.20 or more, it is determined that the crystal grain is the oxide 42. In this case, when an SEM is used for observation, the oxide 42 is characterized in that it is found to have a relatively high brightness and is brighter than the shell portion 412 when observed by a backscattered electron image (BSE image).

[0048] It should be noted that as stated in the Fig. 4A, the oxide 42 may be enclosed within the shell portion 412. In particular, the oxide 42 is not in contact with the core portion 411 and is not in contact with the grain boundary of the dielectric grain 41. Alternatively, as shown in the Fig. 4B, 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 cladding portion 412. Alternatively, as shown in Fig. 4C, the oxide 42 may be in contact with a portion of the grain boundary of the dielectric grain 41.

[0049] Alternatively, as described in the Fig. 4D, 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 boundary of the dielectric grain 41. Furthermore, as shown in Fig. 4A to Fig.4D, a plurality of oxides 42 are spaced apart from each other in the shell portion 412. It should be noted that, as shown in the Fig. 4E, the oxide 42 may be formed over a plurality of the adjacent dielectric grains 41 across the grain boundary, but the oxide 42 is present such that it does not connect the core portions 411 of the plurality of dielectric grains 41. The oxides 42 having the shapes shown in Fig. 4A to Fig. 4E may be mixed.

[0050] Furthermore, as stated in the Fig.1, the ceramic dielectric composition may contain a crystal grain 43 having a composition or crystal structure different from that of the dielectric grains 41 and the oxide 42. The ceramic dielectric composition may also contain crystal grains or glass particles containing silicon. This allows the ceramic dielectric composition to be sufficiently densified by firing at 1300°C or less.

[0051] The crystal grain 43 may be a crystal grain or a glass grain such as silicate (SiO2), enstatite (MgSiO3), barium magnesium silicate (BaMgSiO4), or fresnoite (Ba2TiSi2O8).

[0052] Further examples of the crystal grain 43 may be a secondary compound originating from added substances or electrodes, such as geikierite (MgTiO3), manganese nickel oxide ((Mn,Ni)O) or pyrophanite (MnTiO3).

[0053] Furthermore, a heterophase 44 having a different composition or crystal structure from that of the dielectric grain 41, the oxide 42, and the crystal grain 43 may be included in the ceramic dielectric composition.

[0054] A more suitable example of heterophase 44 is a mixed oxide based on barium titanate, such as Ba4Ti 11 O 26 , which is a monoclinic crystal system with the space group C2 / m and lattice constants a = 15.160 Å, b = 3.893 Å, c = 9.093 Å, and β = 98.6°. This is due to the fact that the barium titanate-based mixed oxide has a barium to titanium ratio relatively close to 3 and can be easily deposited intentionally without the use of a large amount of an additive containing titanium as the main component. Regarding information on the crystal phase of Ba4Ti 11 O 26As a suitable example, reference can be made to PDF-01-083-1459 in the “Powder Diffraction File” (PDF) published by ICDD (International Centre for Diffraction Data; Pennsylvania, USA).

[0055] As a more suitable example of heterophase 44, it is preferred that magnesium, manganese or nickel be dissolved as a solid solution in Ba4Ti 11 O 26 and occupies the vacancies or serves as a replacement for part of the titanium. Ba4Ti 11 O 26 exhibits a crystal structure in which vacancies occur at some of the titanium positions. Therefore, titanium is likely to change from a tetravalent cation to a trivalent cation at the vacancies, and as a result, the resistivity is likely to decrease. To complement this, it is effective to include at least one of magnesium, manganese, and nickel in the alloy as a solid solution.

[0056] (Second Embodiment) In a second embodiment, a multilayer ceramic capacitor 100 using the ceramic dielectric composition of the first embodiment will be described.

[0057] The Fig. 5 shows a perspective view of the multilayer ceramic capacitor 100, in which a cross section of a part of the multilayer ceramic capacitor 100 is shown. Fig. 6 is a cross-sectional view taken along the line AA in the Fig. 5. The Fig. Figure 7 is a cross-sectional view taken along line BB in the Fig. 5. As it is in Fig. 5 to Fig.As shown in Figure 7, the multilayer ceramic capacitor 100 includes a multilayer chip 10 having a rectangular parallelepiped shape and external electrodes 20a and 20b provided opposite each other on two end surfaces of the multilayer chip 10, respectively. Of four surfaces other than the two end surfaces of the multilayer chip 10, two surfaces other than the upper surface and the lower surface in the stacking direction are referred to as side surfaces. Each of the external electrodes 20a and 20b extends to the upper surface and the lower surface in the stacking direction and the two side surfaces of the multilayer chip 10. However, the external electrodes 20a and 20b are spaced apart from each other.

[0058] The multilayer chip 10 has a structure in which dielectric layers 11 containing the ceramic dielectric composition and internal electrode layers 12 composed predominantly of a base metal are alternately stacked. In other words, the multilayer chip 10 includes the internal electrode layers 12 facing each other and the dielectric layers 11 disposed between the internal electrode layers 12. The edges in the direction in which each internal electrode layer 12 extends are alternately exposed at a first end surface provided with the external electrode 20a of the multilayer chip 10 and a second end surface provided with the external electrode 20b. Consequently, the internal electrode layers 12 are alternately electrically connected to the external electrode 20a and the external electrode 20b.Accordingly, 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 the multilayer structure of the dielectric layers 11 and the internal electrode layers 12, the outermost layers in the stacking direction are the internal electrode layers 12, and cap layers 13 cover the upper and lower surfaces of the multilayer structure. The cap layer 13 is predominantly composed of a ceramic material. For example, the main component of the cap layer 13 may be the same as the main component of the dielectric layer 11, or it may be different from the main component of the dielectric layer 11.

[0059] For example, the multilayer ceramic capacitor 100 may have a length of 0.25 mm, a width of 0.125 mm, and a height of 0.125 mm. The multilayer ceramic capacitor 100 may have a length of 0.4 mm, a width of 0.2 mm, and a height of 0.2 mm. The multilayer ceramic capacitor 100 may have a length of 0.6 mm, a width of 0.3 mm, and a height of 0.3 mm. The multilayer ceramic capacitor 100 may have a length of 1.0 mm, a width of 0.5 mm, and a height of 0.5 mm. The multilayer ceramic capacitor 100 may have a length of 3.2 mm, a width of 1.6 mm, and a height of 1.6 mm. The multilayer ceramic capacitor 100 can have a length of 4.5 mm, a width of 3.2 mm, and a height of 2.5 mm. However, the multilayer ceramic is not limited to these sizes.

[0060] The inner electrode layer 12 is predominantly composed of a base metal, such as nickel (Ni), copper (Cu), or tin (Sn). The inner electrode layer 12 may be composed of a noble metal, such as platinum (Pt), palladium (Pd), silver (Ag), or gold (Au), or an alloy comprising one or more thereof.

[0061] As it is in the Fig. As shown in Fig. 6, the portion where the inner electrode layer 12 connected to the outer electrode 20a faces the inner electrode layer 12 connected to the outer electrode 20b is a portion where capacitance is generated in the multilayer ceramic capacitor 100. Therefore, this portion is referred to as a capacitance portion 14. That is, the capacitance portion 14 is a portion where two adjacent inner electrode layers 12 connected to different outer electrodes face each other.

[0062] The portion where the inner electrode layers 12 connected to the outer electrode 20a face each other without interposing the inner electrode layer 12 connected to the outer electrode 20b is called an end edge portion 15. The portion where the inner electrode layers 12 connected to the outer electrode 20b face each other without interposing the inner electrode layer 12 connected to the outer electrode 20a is another end edge portion 15. That is, the end edge portion 15 is a portion where the inner electrode layers 12 connected to one of the outer electrodes face each other without interposing the inner electrode layer 12 connected to the other of the outer electrodes. The end edge portion 15 is a portion where no capacitance is generated.

[0063] As it is in the Fig. As shown in FIG. 7, in the multilayer chip 10, a portion from one of the two side surfaces of the multilayer chip 10 to lateral side edges of the internal electrode layers 12 is referred to as a side edge portion 16. That is, each of the side edge portions 16 is a portion covering the lateral side edges, extending to one of the side surfaces of the multilayer structure, of the stacked internal electrode layers 12. The side edge portion 16 is a portion where no capacitance is generated.

[0064] In the multilayer ceramic capacitor 100 according to this embodiment, at least a portion of the dielectric layer 11 in the capacitance section 14 includes the dielectric grain 41 and the oxide 42 formed in the Fig.1. This can prevent changes in electrostatic capacity due to firing temperature and improve insulating properties in a wide range of firing atmospheres, thereby achieving high mass productivity.

[0065] Next, a manufacturing method of the multilayer ceramic capacitors 100 will be described. Fig. 8 shows a manufacturing process of the multilayer ceramic capacitor 100.

[0066] (Method for Producing a Raw Material Powder) The ceramic dielectric composition for forming the dielectric layer 11 is prepared. Generally, an A-position element and a B-position element are incorporated into the dielectric layer 11 in a sintered phase of grains of ABO3. For example, barium titanate is a tetragonal compound having a perovskite structure and has a high dielectric constant. Generally, barium titanate is obtained by reacting a titanium material such as titanium dioxide with a barium material such as barium carbonate and synthesizing barium titanate. Various methods can be used as the synthesis method for the ceramic that patterns the dielectric layer 11. For example, a solid-phase method, a sol-gel method, a hydrothermal method, or the like can be used. Embodiments can utilize any of these methods.

[0067] An additive compound can be appropriately added to the resulting barium titanate powder. As an example, the additive of the ceramic dielectric composition of the first embodiment is used. Optionally, an oxide or glass containing Zr (zirconium), V (vanadium), Cr (chromium), Co (cobalt), Ni (nickel), Li (lithium), B (boron), Na (sodium), K (potassium) can also be used.

[0068] For example, a compound containing an additive compound is wet-mixed with barium titanate powder, and then dried and pulverized to produce a ceramic material in which the barium titanate powder and the additive compound are mixed. For example, the ceramic material obtained as described above may be optionally pulverized to adjust the particle size, or it may be subjected to a classification process to adjust the particle size. Specifically, the ceramic material may be mixed with beads having a diameter of 0.1 mm to 3 mm, such as yttrium-stabilized zirconia, alumina, or silicon nitride, and stirred for 10 to 100 hours to adjust the particle size. The above process yields the ceramic dielectric composition.

[0069] (Forming a Dielectric Green Sheet) Next, a binder such as a polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the resulting dielectric material and wet-mixed. Using the resulting slurry, a ceramic green sheet 51 is formed on a base material by, for example, a die coating method or a doctor blade method, and then dried. The base material is, for example, a PET (polyethylene terephthalate) film. Figures related to the formation of the dielectric green sheet are omitted.

[0070] (Forming an internal electrode structure) Next, as shown in the Fig.As shown in Figure 9A, a conductive metal paste containing an organic binder is printed on the surface of the ceramic green sheet 51 by screen printing, gravure printing, or the like to form internal electrodes. Internal electrode patterns 52 are alternately arranged on a pair of external electrodes. Ceramic particles are added to the conductive metal paste as a co-material. Although the main component of the ceramic particles is not specifically limited, it is preferably the same as the main component of the ceramic of the dielectric layer 11. For example, barium calcium titanate with an average particle size of 50 nm or less can be uniformly dispersed.

[0071] Next, a binder such as ethyl cellulose and an organic solvent such as terpineol are added to the ceramic dielectric composition obtained in the process for preparing the raw material powder, and the mixture is kneaded in a roll mill to form a dielectric pattern paste for the reverse pattern layer. As described in the Fig. As shown in Figure 9A, a dielectric pattern 53 is disposed on the ceramic green sheet 51 by printing a dielectric pattern paste in the peripheral region where the internal electrode pattern 52 is not printed, and a gap is filled with the internal electrode pattern 52. The ceramic green sheet 51 on which the internal electrode pattern 52 and the dielectric pattern 53 are printed is referred to as a stacked unit.

[0072] Afterwards, as stated in the Fig.9B, the inner electrode layers 12 and the dielectric layers 11 are alternately arranged, and the inner electrode layers 12 have edges on both longitudinal end surfaces of the dielectric layers 11. The stacking units are stacked so that they are alternately exposed and alternately led out to a pair of outer electrodes 20a and 20b with different polarities. For example, the number of stacked layers of the inner electrode structure 52 is set to 100 to 1000 layers.

[0073] (squeezing process) As it is in the Fig. 10, a predetermined number (for example, 2 to 10 layers) of cover layers 54 are stacked on the top and bottom of the multi-layer body in which the stacking units are stacked, and bonded by thermocompression. The ceramic dielectric composition described above can be used as an example of the ceramic material for the cover layer 54. The multilayer body is then cut into a predetermined chip size (e.g., 1.0 mm x 0.5 mm).

[0074] (Firing process) After the thus obtained ceramic multilayer body is freed from the binder in an N2 atmosphere, air atmosphere or the like, a metal paste, which becomes the base layer of the external electrodes 20a and 20b, is applied by a dipping method, and the ceramic multilayer body is fired in a reducing atmosphere at an oxygen partial pressure of 10 -10 up to 10 -7 atm, 800 °C to 1100 °C, and fired at 1150 °C to 1300 °C for 10 minutes to 2 hours. In this way, the multilayer ceramic capacitor 100 is obtained.

[0075] (Re-oxidation treatment process) After that, a re-oxidation treatment can be carried out at 600 °C to 1000 °C in an N2 gas atmosphere.

[0076] (Plating Process) Next, a metal coating such as Cu, Ni, Sn, etc., is applied to the base layer of the external electrodes 20a and 20b by plating. Through the above steps, the multilayer ceramic capacitor 100 is completed.

[0077] The side edge portion can be applied to the side surface of the ceramic multilayer body or by coating. In particular, as described in Fig.As shown in Fig. 11, the ceramic multilayer body is obtained by alternately stacking the ceramic green sheets 51 and the internal electrode patterns 52 having the same width as the ceramic green sheets 51. Next, a layer formed of the dielectric pattern paste may be attached as a side edge portion 55 to the side surface of the ceramic multilayer body.

[0078] According to the manufacturing method of this embodiment, the added rare earth element R and titanium are heated for 10 minutes to 1 hour in a reducing atmosphere with an oxygen partial pressure of 10 -10 up to 10 -7atm at 800 to 1100 °C, and then the added rare earth element R and titanium generate R2Ti2O7, which is a compound with a pyrochlore structure or a perovskite plate structure. When the temperature is then increased to 1100 °C to 1300 °C, the R2Ti2O7 reacts with the surface of the barium titanate crystal grains and generates the shell portion 412 in the form of a perovskite mixed compound, such as R(Ti, Mn)O3. Since the dielectric grain 41 and the oxide 42, which are present in the Fig. 1 are formed in at least a portion of the dielectric layer 11 in the capacitance section 14, a change in electrostatic capacitance due to the firing temperature can be prevented. As a result, high mass productivity can be achieved.

[0079] The firing temperature dependence (Δε / °C) of the relative dielectric constant due to the change in firing temperature of the multilayer ceramic capacitor 100 is determined by the following method. First, the electrostatic capacitance Cp (nF) and the direct current I (nA) of the multilayer ceramic capacitor 100 subjected to the firing process, the re-oxidation process, and the plating process are measured. Next, the capacitance portion 14 of the multilayer ceramic capacitor 100 is cut or polished by cutting or polishing the cross section of line AA and the cross section of line BB shown in the Fig. 6 and Fig. 7, and the effective area of the inner electrode layer is calculated in a state where a smoothness that can be judged as a mirror surface is obtained using a diamond paste of 2 μm or less.

[0080] The effective area S is calculated according to S = L × W × (N - 1) from the length L and the number of layers N of the inner electrode layer 12 in the capacity section 14 in the Fig. 6 and the width W of the inner electrode layer 12 in the capacity section 14 in the Fig. 7 calculated.

[0081] Each thickness of the dielectric layers 11 is also measured, and the average thickness "t" is calculated. In this case, the relative dielectric constant "ε" can be calculated according to ε = (Cp × t / S) / ε0 and the dielectric constant of a vacuum: ε0 = 8.8542 × 10 -12 F / m can be calculated.

[0082] Furthermore, the specific DC resistance ρ (Ω cm) can be calculated according to ρ = (V / I) × (S / t), where V (V) is the DC voltage during the measurement.

[0083] Regarding the electrostatic capacitance Cp, it is generally preferable to measure it using an LCR meter. During the measurement, it is necessary to determine the measurement frequency and the measurement voltage, and it is preferable to determine the measurement voltage as a measurement electric field, which depends on the thickness of the dielectric layer 11. In this embodiment, the electrostatic capacitance Cp can be measured at a room temperature of 25°C with a measurement frequency of 1 kHz and a measurement electric field of 0.5 Vrms / µm, that is, 1 Vrms when the thickness of the dielectric layer 11 is 2 µm.

[0084] The direct current I is generally preferably measured using an insulation resistance meter. When performing the measurement, it is necessary to determine the measurement voltage, and it is preferable to determine it as a measurement electric field, which depends on the thickness of the dielectric layer 11. In this embodiment, the multilayer ceramic capacitor 100 is kept in a thermostatted chamber at 150°C for 30 minutes, insulation from the environment is ensured by using ceramic insulators or the like, and a measurement electric field of 30 V / µm (for example, 60 V for 30 seconds when the thickness of the dielectric layer 11 is 2 µm) is applied through wires connected from the thermostatted chamber to the external electrodes 20a and 20b. The direct current I is measured, and the direct current resistivity ρ can be calculated.It should be noted that unless otherwise specified, the measurement is performed according to Japan Industrial Standards C5101-22:2021, Fixed capacitors for electronic equipment - Part 22: Type-specific general rules - Fixed multilayer ceramic capacitors for surface mount type 2.

[0085] Next, the DC resistivity "ρ" of the multilayer ceramic capacitor obtained at each firing temperature is measured, and the firing temperature that maintains the highest resistivity is determined as the optimal firing temperature. Generally, if the firing temperature is too low, the density becomes too low and the resistivity becomes low. If the firing temperature is too high, the ceramic grains become large and the number of grain boundaries decreases, resulting in a decrease in the resistivity.

[0086] Next, the relative permittivity "ε" of the multilayer ceramic capacitor obtained at the firing temperature that maintains the highest resistivity and the relative permittivity of the multilayer ceramic capacitor obtained by firing at firing temperatures of -20°C and +20°C from the firing temperature that maintains the highest resistivity are used to determine the slope of a straight line using the least squares method. Furthermore, the value is used to determine the firing temperature dependence of the relative permittivity (Δε / °C), which is used as an index of high mass productivity.

[0087] It is preferred that the DC resistivity measured at 150 °C is 1.0 × 10 8 Ω · cm or more. Because it is 1.0 × 10 8Ω cm or more, the multilayer ceramic capacitor 100 using the ceramic dielectric composition of this embodiment can have sufficient resistance.

[0088] The specific DC resistance measured at 150 °C is more preferably 1.0 × 10 10 Ω · cm or more. Because it is 1.0 × 10 10 Ω cm or more, the multilayer ceramic capacitor 100 using the ceramic dielectric composition of this embodiment not only has sufficient resistance, but also it becomes easier to make the dielectric layer thinner and increase the number of stacked inner electrode layers.

[0089] It is preferable that Δε / °C is 10 or less. When it is 10 or less, firing can be achieved in a shorter time while preventing changes in electrostatic capacitance due to changes in firing temperature, and high mass productivity of the multilayer ceramic capacitor 100 using the ceramic dielectric composition of this embodiment can be achieved.

[0090] It is preferable that the relative dielectric constant “ε” is 2000 or more. Even if the DC resistivity measured at 150 °C is 2.0 × 10 8Ω cm or more and the firing temperature dependence on the dielectric constant Δε / °C is 12 or less, if “ε” is small, the result is that the electrostatic capacitance Cp will have an insufficient value and the characteristics will not be suitable for the application of the multilayer ceramic capacitor 100 using the ceramic dielectric composition.

[0091] It should be noted that in the above embodiments, a multilayer ceramic capacitor has been described as an example of a multilayer ceramic electronic component, but this is not limiting. For example, other multilayer ceramic electronic components, such as varistors and thermistors, may also be used. [Examples]

[0092] (Example 1) A barium titanate (BaTiO3) powder having an average particle size of 200 nm was prepared, and 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 100 mol of the barium titanate powder to obtain a ceramic dielectric composition.

[0093] The ceramic dielectric composition was mixed with ethanol, toluene, and PVB (polyvinyl butyral) resin to form a dielectric slurry. This slurry was formed into a ceramic green sheet using a die coater. After drying, a nickel paste was printed onto the ceramic green sheet to form an internal electrode structure. The resulting stacked units were stacked, and the top and bottom surfaces were pressed with layers of thickly stacked ceramic green sheets that did not form an internal electrode structure, and then cut into small pieces. Next, a nickel paste was applied to the two end surfaces as a conductive paste for the external electrodes and degreased in nitrogen gas.The degreased small pieces were fired and sintered in a reducing atmosphere in which the oxygen partial pressure was adjusted to prevent nickel oxidation, thus producing a multilayer ceramic capacitor. Firing was carried out by holding the temperature at 1000 °C for 10 minutes and then at 1240 °C for 10 minutes.

[0094] The size of the produced multilayer ceramic capacitor was a 1005 shape (1.0 mm × 1.0 mm × 0.5 mm). Then, a re-oxidation process was performed at 950 °C. Then, a plating process was performed to form a Cu-plated layer, a Ni-plated layer, and an Sn-plated 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.

[0095] (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 ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1220°C for 10 minutes. The other conditions were the same as those in Example 1.

[0096] (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 ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1230°C for 10 minutes. The other conditions were the same as those in Example 1.

[0097] (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 ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1230°C for 10 minutes. The other conditions were the same as those in Example 1.

[0098] (Example 5) In 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 ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1240°C for 10 minutes. The other conditions were the same as those in Example 1.

[0099] (Example 6) 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 ceramic dielectric composition. The firing temperature was maintained at 1000 °C for 10 minutes and then at 1240 °C for 10 minutes. The other conditions were identical to those in Example 1.

[0100] (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 ceramic dielectric composition. The firing temperature was maintained at 1000 °C for 10 minutes and then at 1250 °C for 10 minutes. The other conditions were identical to those in Example 1.

[0101] (Example 8) 0.75 mol Gd2Ti2O7, 1.00 mol MnCO3, 1.00 mol SiO2 and 0.50 mol MgO were added to 100 mol barium titanate powder, so that a

[0102] Ceramic dielectric composition was obtained. The firing temperature was maintained at 1240 °C for 10 minutes. The other conditions were identical to those in Example 1.

[0103] (Example 9) In Example 9, 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 100 mol of barium titanate powder to obtain a ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1270°C for 10 minutes. The other conditions were the same as those in Example 1.

[0104] (Example 10) In Example 10, 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 100 mol of barium titanate powder to obtain a ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1270°C for 10 minutes. The other conditions were the same as those in Example 1.

[0105] (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 ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1260°C for 10 minutes. The other conditions were identical to those in Example 1.

[0106] (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 ceramic dielectric composition. Firing was performed by holding the temperature at 1000°C for 10 minutes and then at 1250°C for 10 minutes. The other conditions were the same as those in Example 1.

[0107] For each of the multilayer ceramic capacitors of Examples 1 to 10 and Comparative Examples 1 and 2, the electrostatic capacitance Cp was measured at room temperature (25 °C) at 1 kHz and 1 Vrms using an LCR meter, and the direct current "I" was measured at 150 °C when 60 V was applied for 30 seconds using an insulation resistance meter. In addition, the cross sections of lines AA and BB in the Fig.5 to calculate the effective area "S" of the inner electrode layer and the average thickness "t" of the dielectric layer. The relative dielectric constant "ε" and the specific resistance "ρ" were calculated from the effective area "S" and the average thickness "t". The specific resistance "ρ" of each of the multilayer ceramic capacitors of Examples 1 to 10 and Comparative Examples 1 and 2 was then compared, and the relative dielectric constants of the multilayer ceramic capacitors fired at temperatures of -20°C and +20°C were compared with the multilayer ceramic capacitor obtained at the firing temperature with the highest specific resistance.The slope of the straight line was determined using the least squares method based on these firing temperatures and the relative dielectric constants and defined as the firing temperature dependence of the relative dielectric constant (Δε / °C).

[0108] Furthermore, a conductive material made of osmium was deposited onto the exposed dielectric layer by vapor deposition, and the crystal grains present in the dielectric layer were photographed by SEM. The average grain size of the crystal grains forming the dielectric layer was then 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.

[0109] Furthermore, during the SEM examination of the multilayer ceramic capacitor, the presence of oxide 42 in the BSE image was confirmed by the brightness difference.

[0110] Then, for each multilayer ceramic capacitor, to confirm the composition of the shell portion and the core portion of the crystal grains in the dielectric layer and oxide 42, samples were cut out for EDS examination by TEM and FIB, and the presence of the core-shell structure was confirmed by the EDS composition evaluation method. The core portion was defined as a portion with an R / Ti element ratio of less than 0.02, and the shell portion was defined as a portion with an R / Ti element ratio of 0.02 or more and less than 0.20. In addition, the element ratio of the rare earth element R to titanium was also confirmed for oxide 42, and it was confirmed that the R / Ti element ratio met the requirement of 0.20 or more.

[0111] Furthermore, for each multilayer ceramic capacitor, the cap layer, end edge, side edge, and external electrodes not present in the capacitance section were polished or cut to separate them, and the dielectric layer forming the capacitance section was pulverized to obtain a powder. The diffraction line profile of the powder was measured by an X-ray diffraction (XRD) device using Cu-Kα radiation to confirm the presence of oxide 42, which was identified as R2Ti2O7.

[0112] Table 1 summarizes the amounts of additives added in Comparative Examples 1 and 2 and Examples 1 to 10. Table 2 summarizes the firing temperatures, average grain diameters, ε, Δε / °C, and specific resistance at 150 °C in Comparative Examples 1 and 2 and Examples 1 to 10. The evaluation was performed as follows. A sample in which Δε / °C was 10 or less and the specific resistance was 1.0 × 10 9 A sample whose Δε / °C was 10 or less was rated as good "Δ". A sample whose Δε / °C was more than 10 was rated as good "Δ". [Table 1] Amount added to 100 mol BaTiO3 (mol) La2O3 Pr2O3 Nd2O3 Eu2O3 Gd2O3 Dy2O3 Ho2O3 Er2O3 Yb2O3 Gd2Ti2O7 TiO2 MnCO3 SiO2 MgO Comparison example 1 0,00 0,00 0,00 0,00 0,75 0,00 0,00 0,00 0,00 0,00 0,00 1,00 1,00 0,50 Comparison example 2 0,00 0,00 0,00 0,00 0,75 0,00 0,00 0,00 0,00 0,00 0,75 1,00 1,00 0,50 Example 1 0,00 0,00 0,00 0,00 0,75 0,00 0,00 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 2 0,75 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 3 0,00 0,75 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 4 0,00 0,00 0,75 0,00 0,00 0,00 0,00 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 5 0,00 0,00 0,00 0,75 0,00 0,00 0,00 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 6 0,00 0,00 0,00 0,00 0,00 0,75 0,00 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 7 0,00 0,00 0,00 0,00 0,00 0,00 0,75 0,00 0,00 0,00 1,50 1,00 1,00 0,50 Example 8 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,75 0,00 1,00 1,00 0,50 Example 9 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,75 0,00 0,00 1,50 1,00 1,00 0,50 Example 10 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,00 0,75 0,00 1,50 1,00 1,00 0,50 [Table 2] Firing temperature (°C) Average grain size (nm) ε Δε / °C Specific resistance (Ω cm) assessment Comparison example 1 1260 550 4500 15,5 1,9 × 10 8 × Comparison example 2 1250 410 3900 10,2 1,9 × 10 8 × Example 1 1240 270 3320 6,1 2,6 × 10 10 ◯ Example 2 1220 260 2270 2,5 1,9 × 10 8 ◯ Example 3 1230 280 2470 2,7 5,2 × 10 8 ◯ Example 4 1230 280 2630 4,8 2,3 × 10 9 ◯ Example 5 1240 270 3080 5,1 3,9 × 10 10 ◯ Example 6 1240 280 3150 6,8 1,9 × 10 10 ◯ Example 7 1250 260 3020 5,5 5,6 × 10 9 ◯ Example 8 1240 270 3330 5,3 3,7 × 10 10 ◯ Example 9 1270 250 2200 2,7 5,1 × 10 5 Δ Example 10 1270 240 2150 2,3 5,1 × 10 5 Δ

[0113] Comparative Examples 1 and 2 were comparative examples in which gadolinium was included as the rare earth element. In Comparative Examples 1 and 2, gadolinium was included as the rare earth element, so the average grain size was 550 nm and 410 nm, respectively, and the specific resistance at 150 °C was 1.9 × 10 8 Ω cm, and sufficient resistivity could be maintained. However, because there was insufficient TiO2 added, the value of Δε / °C was greater than 10, and it was not possible to obtain the preferred value of 10 or less.

[0114] In Examples 1 to 7, 9, and 10, the amount of TiO2 added was 1.5 mol per 100 mol of BaTiO3, and lanthanum, praseodymium, neodymium, europium, gadolinium, dysprosium, holmium, erbium, and ytterbium were added as the rare earth element at 0.75 mol each. In Example 8, 0.75 mol of Gd2Ti2O7 was added to 100 mol of BaTiO3. In this composition, the value of Δε / °C was 10 or less. For example, even when a larger sintering furnace than the one at hand was used to increase productivity, the dielectric constant obtained with respect to the temperature distribution in the furnace, that is, the value of the electrostatic capacitance Cp for a multilayer ceramic capacitor, did not exhibit a large distribution. Therefore, even with sintering, mass production is possible in a short time due to a rapid temperature rise. Furthermore, when the rare earth element was europium, gadolinium, dysprosium, or holmium, "ε" was 3000 or more.In addition, the average grain size was 500 nm or less and the resistivity was 1.0 × 10. 9 Ω · cm or more.

[0115] To investigate the mechanism of the dielectric layer in detail, the following STEM-EDS investigations were conducted on the multilayer ceramic capacitors obtained by Comparative Examples 1 and 2 and Examples 1 to 10: whether a core-shell structure exists, whether the oxide 42 is present, whether the element ratio "v" of Ba to Ti in the 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. [Table 3] Shell section Core section Presence of oxide 42 Contact between nuclei and the oxide 42 Oxide 42 R / Ti Mn / Ti R / Ti Mn / Ti R / Ti Comparison example 1 0,061 0,020 0,006 0,001 None - - Comparison example 2 0,082 0,021 0,005 0,003 None - - Example 1 0,101 0,017 0,003 0,003 Is available None 0,91 Example 2 0,085 0,022 0,008 0,002 Is available None 0,37 Example 3 0,097 0,018 0,007 0,004 Is available None 0,45 Example 4 0,102 0,025 0,007 0,002 Is available None 0,61 Example 5 0,117 0,012 0,003 0,001 Is available None 0,85 Example 6 0,098 0,016 0,004 0,002 Is available None 0,87 Example 7 0,081 0,021 0,003 0,004 Is available None 0,91 Example 8 0,092 0,017 0,003 0,002 Is available None 0,94 Example 9 0,079 0,018 0,002 0,001 Is available contact 0,97 Example 10 0,072 0,015 0,004 0,002 Is available contact 0,95

[0116] In Comparative Examples 1 and 2, the amount of TiO2 added was insufficient, so the presence of oxide 42, which is visible as bright and relatively bright compared with the main crystal grains formed of barium titanate in the SEM-BSE image, could not be confirmed.

[0117] On the other hand, in Examples 1 to 10, the element ratio "w" of the rare earth element R to Ti in the oxide 42 was in the range of 0.2 ≦ w, so the presence of the oxide 42 was also evident. Furthermore, in Examples 1 to 8, the oxide 42 was not in contact with the grain nuclei. Furthermore, as shown in Table 1, the value of Δε / °C was 10 or less, and the resistivity was 1.0 × 10 8Ω cm or more, the average grain diameter was 500 nm or less, and the dielectric constant was ε > 2000 or more. Therefore, even when a kiln larger than an existing kiln was used to increase productivity, the dielectric constant obtained with respect to the temperature distribution in the kiln, that is, the value of the electrostatic capacitance Cp of the multilayer ceramic capacitor, did not exhibit a large distribution. Therefore, even when firing in a short time, a rapid temperature rise can enable mass production and maintain sufficient reliability.

[0118] Although the embodiments of the present invention have been described in detail, it should be noted that the present invention is susceptible to various changes, substitutions and alterations without departing from the spirit and scope of the invention. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Yukikuni AKISHIGE and Misako KAMATA, “Crystal Chemistry of A2B2O7 Type Oxide Ferroelectrics with Perovskite-related Layered Structure”, Memoirs of the Faculty of Education, Shimane University, Natural science

[0031] Japan Industrial Standards C5101-22:2021

[0084]

Claims

[1] Electronic multilayer ceramic device comprising: a dielectric layer comprising a dielectric grain including a core portion, a shell portion surrounding the core portion and comprising a rare earth element, and an oxide deposited within the shell portion and having a higher concentration of the rare earth element than the shell portion, and having a perovskite structure represented by the general formula ABO3; a plurality of inner electrode layers surrounding the dielectric layer and facing each other; and a plurality of outer electrodes, each of which is electrically coupled to each of the plurality of inner electrode layers. [2] The multilayer ceramic electronic device according to claim 1, wherein the oxide comprises a pyrochlore phase. [3] Electronic multilayer ceramic device according to claim 1 or 2, wherein an A-position of the perovskite structure comprises barium, and wherein an element included in a B position of the perovskite structure is at least one of titanium or zirconium. [4] The multilayer ceramic electronic device according to any one of claims 1 to 3, wherein the rare earth element is at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium or erbium. [5] The multilayer ceramic electronic device according to any one of claims 1 to 4, wherein an element ratio of the rare earth element to titanium in the shell portion is 0.02 or more and less than 0.

20. [6] The multilayer ceramic electronic device according to any one of claims 1 to 5, wherein an element ratio of the rare earth element to titanium in the oxide is 0.20 or more. [7] The multilayer ceramic electronic device according to any one of claims 1 to 6, wherein the oxide is enclosed in the shell portion. [8] The multilayer ceramic electronic device according to any one of claims 1 to 7, wherein the oxide is in contact with a part of the core portion. [9] The multilayer ceramic electronic device according to any one of claims 1 to 8, wherein the oxide is in contact with a part of a grain boundary of the dielectric grain. [10] A multilayer ceramic electronic device according to any one of claims 1 to 9, wherein the oxide extends from a part of the core portion to a part of a grain boundary of the dielectric grain. [11] The multilayer ceramic electronic device according to any one of claims 1 to 10, wherein the shell portion comprises two or more of the oxide spaced apart from each other. [12] Electronic multilayer ceramic device according to one of claims 1 to 11, wherein the dielectric layer comprises two or more of the dielectric grains adjacent to each other by a grain boundary, and wherein the oxide does not interconnect core portions of the two or more of the dielectric grain. [13] The multilayer ceramic electronic device according to any one of claims 1 to 12, wherein the oxide is not in contact with the core portion. [14] Electronic multilayer ceramic device according to one of claims 1 to 13, wherein the dielectric layer comprises two or more of the dielectric grain, and wherein a maximum grain diameter of two or more of the dielectric grain is 2 µm or less. [15] The multilayer ceramic electronic device according to any one of claims 1 to 14, wherein the shell portion comprises magnesium and manganese. [16] Ceramic dielectric composition comprising: a dielectric grain comprising a core portion, a shell portion surrounding the core portion and comprising a rare earth element, and an oxide deposited within the shell portion and having a higher concentration of the rare earth element than the shell portion, and having a perovskite structure represented by the general formula ABO3.

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