Dielectric composition and electronic component

Abstract

The invention provides a dielectric composition which maintains high relative dielectric constant and has excellent high-temperature load service life and reliability, and an electronic component comprising the dielectric composition. The present invention relates to a dielectric composition and a method for manufacturing the same. RA1 represents the concentration of the first rare earth element at the center of a specific main phase particle having a particle diameter equal to or greater than the average particle diameter (D50) of the main phase particles observed in the cross section, and RA2 represents the concentration of the first rare earth element at the center of a triple-point segregation substance; when the concentration of the second rare earth element at the center of the specific main phase particles is represented by RB1 and the concentration of the second rare earth element at the center of the triple-point segregation substance is represented by RB2, RA2 / RA1 is 1.0 to 2.5, and RB2 / RB1 is 3.0 to 9.0 (preferably 5.0 to 7.0).

Description

Technical Field

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

[0002] With the electrification of vehicles and the like, there is a demand for a dielectric composition used in multilayer ceramic capacitors to have a large capacitance and high reliability. As a general technique for achieving a large capacitance, there has been developed a technique of thinning the interlayer thickness of a dielectric layer and increasing the relative dielectric constant of a dielectric material (for example, Patent Document 1 below).

[0003] In order to increase the relative dielectric constant, the crystal grain size is usually increased. However, when the crystal grain size is increased, in the case where the interlayer of the dielectric layer is thin, the number of particles between layers may decrease, resulting in a significant reduction in reliability. On the contrary, in order to ensure high reliability, the crystal grain size needs to be reduced. However, in this case, there is a tendency for the relative dielectric constant to decrease and it is difficult to cope with a large capacitance.

[0004] When fine dielectric powder is used for thinning, when grain growth occurs during sintering to increase the relative dielectric constant, it is difficult to stably control the specified grain size. Even if the target grain size is achieved, the deviation of the grain size is large, resulting in a reduction in reliability. In addition, for example, a dielectric composition used in an electronic component for vehicle-mounted applications and the like is required to have excellent high-temperature load life.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 6091760 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a dielectric composition having an excellent high-temperature load life and reliability while maintaining a high relative dielectric constant, and an electronic component having the dielectric composition.

[0010] Technical Solution for Solving the Technical Problem

[0011] In order to achieve the above object, one aspect of the present invention provides a dielectric composition having a main component represented by ABO3, a first rare earth element, and a second rare earth element.

[0012] The first rare earth element is one or more selected from Dy, Tb, Gd, and Eu.

[0013] The second rare earth element is one or more selected from Y, Yb, and Ho.

[0014] In the cross-section of the dielectric porcelain composition, main phase particles and triple-point segregates surrounded by three or more of the main phase particles are observed.

[0015] When the concentration of the first rare earth element at the center of a specific main phase particle having a particle size equal to or greater than the average particle size (D50) of the main phase particles observed in the cross-section is set as RA1, the concentration of the first rare earth element at the center of the triple-point segregate is set as RA2, the concentration of the second rare earth element at the center of the specific main phase particle is set as RB1, and the concentration of the second rare earth element at the center of the triple-point segregate is set as RB2,

[0016] RA2 / RA1 is 1.0 or more and 2.5 or less (preferably 1.2 or more and 2.5 or less), and RB2 / RB1 is 3.0 or more and 9.0 or less (preferably 5.0 or more and 7.5 or less).

[0017] In-depth research was conducted on the dielectric composition, and as a result, it was found that by setting RA2 / RA1 and RB2 / RB1 to a specified ratio, a dielectric composition having excellent high-temperature load life and reliability while maintaining a high relative dielectric constant can be achieved, thus completing the present invention. By setting RA2 / RA1 and RB2 / RB1 to a specified ratio, a dielectric composition having excellent high-temperature load life and reliability while maintaining a high relative dielectric constant can be achieved.

[0018] Preferably, the average particle size (D50) of the main phase particles is 190 nm or more and 600 nm or less, more preferably 200 nm or more and 500 nm or less. By setting within such a range, it is easy to obtain a dielectric composition having excellent high-temperature load life and reliability while maintaining a high relative dielectric constant.

[0019] Preferably, the ratio (D100 / D50) of the maximum particle size (D100) of the main phase particles to the average particle size (D50) of the main phase particles is 1.8 or less, more preferably 1.4 or less. By setting within such a range, it is easy to obtain a dielectric composition having excellent high-temperature load life and reliability while maintaining a high relative dielectric constant.

[0020] An electronic component according to one aspect of the present invention has the dielectric composition described in any one of the above. In addition, an electronic component according to other aspects of the present invention has a dielectric layer composed of the dielectric composition described in any one of the above. The thickness of the dielectric layer may also be 2 μm or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic cross-sectional view of a multilayer ceramic capacitor as an example of an electronic component according to an embodiment of the present invention.

[0022] Figure 2 It is Figure 1 An enlarged schematic cross-sectional view of the main part of the dielectric layer shown. Detailed implementation mode

[0023] Hereinafter, the embodiments will be described.

[0024] As Figure 1 shown, the multilayer ceramic capacitor 1 as an example of the electronic component of the present embodiment has an element body 10 having a structure in which dielectric layers 2 and internal electrode layers 3 are alternately laminated. A pair of external electrodes 4 electrically connected to the internal electrode layers 3 alternately arranged inside the element body 10 are formed at both ends of the element body 10. The shape of the element body 10 is not particularly limited and is usually in the shape of a rectangular parallelepiped. In addition, the size of the element body 10 is not particularly limited as long as it is set to an appropriate size according to the use.

[0025] The thickness (interlayer thickness) of each layer of the dielectric layer 2 is not particularly limited and can be arbitrarily set according to desired characteristics, uses, etc. Generally, the thickness of the dielectric layer 2 can be 20 μm or less, can be 10 μm or less, or can be 5 μm or less. In the present embodiment, even if it is 2 μm or less or 1 μm or less, it has good characteristics.

[0026] In addition, the number of laminated dielectric layers 2 is not particularly limited. In the multilayer ceramic capacitor of the present embodiment, for example, it can be 10 or more, can be 100 or more, or can be 200 or more.

[0027] In the present embodiment, the internal electrode layers 3 are laminated in such a manner that their respective ends are alternately exposed on the surfaces of the opposite two end faces of the element body 10. There is no particular limitation on the conductive material contained in the internal electrode layer 3. Examples of noble metals used as the conductive material include Pd, Pt, and Ag-Pd alloys. Examples of base metals used as the conductive material include Ni, Ni alloys, Cu, and Cu alloys. In addition, various trace components such as P and / or S in an amount of 0.1 mass% or less may be contained in Ni, Ni alloys, Cu, or Cu alloys.

[0028] In addition, a commercially available electrode paste can also be used to form the internal electrode layer 3. The thickness of the internal electrode layer 3 can be appropriately determined according to uses, etc.

[0029] There is no particular limitation on the conductive material contained in the external electrode 4. Any known conductive material such as Ni, Cu, Sn, Ag, Pd, Pt, Au, or their alloys, or conductive resins can be used. Regarding the thickness of the external electrode 4, it can be appropriately determined according to the use and the like.

[0030] The dielectric layer 2 is composed of the dielectric composition of the present embodiment. The dielectric composition of the present embodiment has a main component and a sub-component having a perovskite-type crystal structure represented by ABO3.

[0031] In the perovskite-type crystal structure represented by ABO3, A is one or more selected from barium (Ba), strontium (Sr), and calcium (Ca), and may also be one or more selected from Ba and Sr. Relative to A, 80 mol% or more of Ba may be contained, or 90 mol% or more of Ba may be contained. A may also be only Ba.

[0032] B is one or more selected from titanium (Ti) and zirconium (Zr), hafnium (Hf) may be contained, and it may also be one or more selected from Ti and Zr. B may contain 70 mol% or more of Ti, may contain 80 mol% or more of Ti, or may be only Ti.

[0033] When A is one or more selected from Ba, Sr, and Ca and B is one or more selected from Ti and Zr, the composition of the main component is specifically described as {{Ba 1-x-y Ca x Sr y}O} u (Ti 1-z Zr z ) v O2.

[0034] x is preferably 0 ≤ x ≤ 0.10, more preferably 0 ≤ x ≤ 0.05. y is preferably 0 ≤ y ≤ 0.10, more preferably 0 ≤ y ≤ 0.05. z is preferably 0 ≤ z ≤ 0.30, more preferably 0 ≤ z ≤ 0.15. u / v is preferably 0.997 ≤ u / v ≤ 1.010, more preferably 0.998 ≤ u / v ≤ 1.005. If u / v is too high, it is likely to cause insufficient sintering, and the relative dielectric constant and reliability of the dielectric composition tend to decrease. If u / v is too low, it is likely to cause deterioration of firing stability, and the temperature characteristics and reliability of the dielectric composition tend to decrease.

[0035] The sub-components have at least a first rare earth element RA and a second rare earth element RB, and preferably have one or more of silicon (Si), magnesium (Mg), manganese (Mn), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), iron (Fe), tungsten (W), molybdenum (Mo), lithium (Li), aluminum (Al), germanium (Ge), boron (B), barium (Ba), calcium (Ca), strontium (Sr), etc.

[0036] In the dielectric composition, relative to the main component, the content C of RA RA is not particularly limited, and in terms of conversion to RA2O3, it is preferably 0.1 mol% or more and 2.0 mol% or less, more preferably 0.2 mol% or more and 0.6 mol% or less. For the content C of RB RB is not particularly limited, and in terms of conversion to RB2O3, it is 0.1 mol% or more and 2.0 mol% or less, more preferably 0.2 mol% or more and 0.6 mol% or less. The content of Si is not particularly limited, and in terms of conversion to SiO2, it can be 0.1 mol% or more and 3.0 mol% or less. When the sub-component elements other than the rare earth elements and silicon are set as M, the content of M can also be 0.01 mol% or more and 1.0 mol% or less in terms of conversion to MO.

[0037] As the first rare earth element RA among the rare earth elements contained in the dielectric composition, it contains one or more selected from gadolinium (Gd), terbium (Tb), dysprosium (Dy), and europium (Eu). In addition, as the second rare earth element RB among the rare earth elements contained in the dielectric composition, it contains at least one selected from yttrium (Y), ytterbium (Yb), and holmium (Ho). In addition, other sub-component elements may also be contained in the dielectric composition, and these elements may also be contained in the form of oxides.

[0038] RA corresponds to an element in the rare earth elements with a smaller difference in ionic radius from the A-site atoms than RB. RA is preferably one or more selected from Dy, Gd, and Tb, more preferably one or more selected from Dy and Gd, and further preferably RA is Dy. RB corresponds to an element in the rare earth elements with a larger difference in ionic radius from the A-site atoms than RA. RB is preferably one or more selected from Y, Yb, and Ho, more preferably one or more selected from Y and Yb, and further preferably RB is Y. By having RA and RB as the above rare earth elements, the temperature characteristics and high-temperature load life are easily improved, and the reliability is also improved.

[0039] As Figure 2 shown, the dielectric layer 2 of the present embodiment is composed of the above dielectric composition and has main phase particles (crystal particles) 2a, 2b, and triple-point segregates 2c.

[0040] The main phase particles 2a and 2b of the present embodiment contain, as a main component, a compound represented by ABO3 and having a perovskite-type crystal structure. In addition, the main component of the main phase particles 2a and 2b is a component that accounts for 80 mass parts or more, preferably 90 mass parts or more, relative to 100 mass parts of the main phase particles. In addition, the main phase particles 2a and 2b may also contain sub-components other than the above-mentioned main component.

[0041] Preferably, all the particles in the observed range of the main phase particles 2a and 2b are main phase particles in which at least a part of the sub-components are completely solid-solved in the main component (hereinafter, sometimes referred to as completely solid-solved main phase particles), but they may also be particles containing a core-shell structure at least in part. The ratio of the completely solid-solved main phase particles to the main phase particles 2a and 2b is not particularly limited, and is preferably 90% or more on a number basis.

[0042] Regarding Figure 2 The composition of the triple-point segregation 2c shown is not particularly limited. The triple-point segregation 2c contains RA and RB, and may also contain at least one or more of Si, Mg, and other sub-components as needed.

[0043] Hereinafter, in the dielectric composition constituting Figure 2 the dielectric layer 2 of the present embodiment shown, the relationship between the main phase particles 2a and 2b and the triple-point segregation 2c will be described.

[0044] The main phase particle 2a is a specific main phase particle having a particle size equal to or larger than the average particle size (for example, median particle size D50) of the particle sizes of the main phase particles 2a and 2b observed in the cross-section within the specified range of the dielectric layer 2, and the main phase particle 2b is other main phase particles other than the specific main phase particle 2a.

[0045] The specified observation range of the cross-section of the dielectric layer 2 for calculating the average particle size (D50) is an observation range in which at least 500 or more main phase particles 2a and 2b can be observed (the cross-section itself may also be cross-sections of multiple parts). In the observation range of this cross-section, when the area of the dielectric layer 2 is set to 100%, the total area of the observed main phase particles 2a and 2b is preferably in the range of 95.0% or more, and the total area of the observed triple-point segregation 2c is preferably in the range of 0.1 to 5.0%. In addition, in the same observation range, the total number of the triple-point segregation 2c is preferably in the range of 0.2 to 20.0% relative to the total number of the main phase particles 2a and 2b.

[0046] Regarding the discrimination, particle size, number, area, etc. of the main phase particles 2a and 2b and the triple-point segregation 2c, for example, they can be measured as follows.

[0047] First, the particle sizes of the main phase particles 2a and 2b can be obtained, for example, by performing image analysis on an SEM (scanning electron microscope) image of the cross-section of the dielectric layer 2 as shown in Figure 2 . For at least 500 or more main phase particles 2a and 2b, the area of each particle is measured. Then, the measured area is converted into the Heywood diameter (equivalent circular diameter), and further converted into the equivalent spherical diameter to obtain the particle size distribution. Based on the obtained particle size distribution, the median value (for example, the particle size of the 250th out of 500) is set as D50, and the maximum value (for example, the particle size of the 500th out of 500) is set as D100.

[0048] From the viewpoint of increasing the relative dielectric constant, D50 is preferably 190 nm or more, more preferably 200 nm or more. From the viewpoint of increasing the high-temperature load life, it can be preferably 600 nm or less, more preferably 500 nm or less. In addition, the ratio of D100 to D50 (D100 / D50) can be preferably 1.8 or less, and more preferably 1.4 or less. When within such a range, the high-temperature load life is improved.

[0049] In the present embodiment, using STEM (scanning transmission electron microscope), by comparing the mapping image obtained by STEM-EDS in the cross-section of the dielectric layer 2 with the reflected electron image obtained by STEM, particles with a higher concentration ratio of A-site and B-site in ABO3 than the surroundings can be set as the main phase particles 2a and 2b. In addition, particles with a concentration of RB (i.e., Y or Yb) higher than the average of the cross-sectional field of view and in contact with three or more main phase particles 2a and 2b and having an equivalent circular diameter of 5 nm or more and 50 nm or less can be set as triple-point segregation 2c. In addition, the boundary between two main phase particles 2a and 2b is a grain boundary, and its thickness is 5 nm or less.

[0050] In the present embodiment, at the center (first point) of a specific main phase particle 2a with a particle size of D50 or more, the concentration of RA can be measured as RA1, and the concentration of RB can be measured as RB1. In addition, at the center (second point) of the triple-point segregation 2c, the concentration of RA can be measured as RA2, and the concentration of RB can be measured as RB2. Moreover, RA2 / RA1 and RB2 / RB1 can be calculated. The concentrations of these RAs and RBs can also be measured, for example, by STEM-EDS, etc. Regarding the centers of the main phase particle 2a and the triple-point segregation 2c, the center of gravity obtained from their respective areas can be used as the center.

[0051] In the present embodiment, RA2 / RA1 is 1.0 or more and 2.5 or less, preferably 1.2 or more and 2.3 or less. Further, RB2 / RB1 is 3.0 or more and 9.0 or less, preferably 5.0 or more and 7.5 or less. By setting it within such a range, it is possible to improve the high-temperature load life and reliability while maintaining a high relative dielectric constant. Regarding the reason, for example, the following aspects can be considered.

[0052] Generally, during firing, as the grains of the main-phase particles 2a and 2b grow, the donor component (mainly RA) and the acceptor component (mainly RB, M) dissolve in the main-phase particles 2a and 2b. At this time, if the grain growth proceeds excessively, the temperature characteristics deteriorate. Moreover, the reliability of the dielectric composition decreases, and the high-temperature load life also decreases. It is considered that in the present embodiment, the triple-point segregation substances (RA2 and RB2) stabilize the grain growth of the main-phase particles (RA1 and RB1), suppress local abnormal grain growth, and improve the high-temperature load life and reliability while maintaining a high relative dielectric constant. Further, it is considered that the first rare-earth element dissolves inside the main-phase particles (near the center) (RA2 / RA1 is 1.0 or more and 2.5 or less), which also improves the high-temperature load life and reliability while maintaining a high dielectric constant.

[0053] In addition, as a means for making RA2 / RA1 and RB2 / RB1 into a specified ratio, for example, a method of separately adding a compound that becomes a segregation substance containing a second rare-earth element and a main-phase raw material that becomes a raw material of the main-phase particles can be exemplified. Further, the following method is also effective: that is, for a compound raw material containing a first rare-earth element, instead of heat-treating it together with a compound raw material containing other elements, it is included in the main-phase raw material.

[0054] Hereinafter, Figure 1 An example of the manufacturing method of the multilayer ceramic capacitor 1 shown will be described below.

[0055] Regarding the multilayer ceramic capacitor 1 of the present embodiment, in the same manner as in the conventional multilayer ceramic capacitor, a green sheet is produced by a usual printing method or a tape casting method using a paste, and after firing it, an external electrode is printed or transferred and fired to complete the manufacturing. Hereinafter, the manufacturing method will be specifically described.

[0056] First, a dielectric raw material for forming a dielectric layer is prepared, made into a coating, and a paste for the dielectric layer is prepared.

[0057] As a dielectric raw material, raw materials of the main component ABO3 and raw materials of various other oxides are prepared. As these raw materials, oxides or mixtures thereof and complex oxides of the above components can be used. In addition, various compounds such as carbonates, oxalates, nitrates, hydroxides, and organometallic compounds that become the above oxides or complex oxides through firing can also be appropriately selected and mixed for use. In addition, in the present embodiment, the particle size of the raw material powder of the main component ABO3 is preferably 200 nm or less.

[0058] In the present embodiment, an oxide of RB, an oxide of M (e.g., MgO), and a compound of Si are pre-mixed and pre-fired, and further pulverized and dried to prepare a heat treatment powder. The obtained heat treatment powder, the raw material of the main component, the oxide of RA, and the oxide of M (e.g., MnO) are mixed to prepare a dielectric raw material. Alternatively, a raw material in which the raw material of the main component is coated with an oxide of RB, an oxide of M (e.g., MgO), and a compound of Si can be prepared, and a raw material of an oxide of A (e.g., a raw material of Ba oxide), an oxide of RA, and an oxide of M (e.g., MnO) contained separately from the main component is mixed therein to prepare a dielectric raw material. Thereby, the solubility of various rare earth elements in the main phase particles changes, and RA2 / RA1 and RB2 / RB1 can be adjusted to a specified range.

[0059] In the present embodiment, a dielectric raw material in which the main component is coated with the above components can also be used. Moreover, in addition to the raw material of the main component, oxides of RA, RB, M, and Si compounds can also be used, for example.

[0060] In addition, as the raw material of the main component ABO3, raw materials manufactured by various methods can be used, for example, raw materials manufactured by the so-called solid phase method and raw materials manufactured by various liquid phase methods (e.g., oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.).

[0061] Moreover, when a component other than the above components is contained in the dielectric layer 2, as the raw material of this component, oxides or mixtures thereof and complex oxides of these components can be used. In addition, in addition to this, various compounds that become the above oxides or complex oxides through firing can be used.

[0062] The content of each compound in the dielectric raw material can be determined so as to become the composition of the above dielectric composition after firing.

[0063] The paste for the dielectric layer can be an organic coating obtained by kneading a dielectric raw material and an organic carrier, or can be an aqueous coating.

[0064] The organic carrier is formed by dissolving a binder in an organic solvent. As for the binder and the solvent, well-known substances can be used.

[0065] In addition, when the dielectric layer paste is an aqueous coating, an aqueous carrier (formed by dissolving a water-soluble binder or a dispersant, etc. in water) and a dielectric raw material can be kneaded. There is no particular limitation on the water-soluble binder, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, etc. can be used.

[0066] Regarding the paste for the internal electrode layer, it can be prepared by kneading the above-mentioned conductive material composed of Ni or Ni alloy, or various oxides, organometallic compounds, resin salts, etc. that become the above-mentioned Ni or Ni alloy after firing, and the above-mentioned organic carrier. In addition, a common material can also be contained in the paste for the internal electrode layer. As the common material, there is no particular limitation, and it can have the same composition as the main component.

[0067] Regarding the paste for the external electrode, it can be prepared in the same manner as the above-mentioned paste for the internal electrode layer.

[0068] The content of the organic carrier in the above-mentioned pastes is not particularly limited, and the general content is as follows: For example, the binder can be set to about 1 to 15% by mass, and the solvent can be set to about 10 to 60% by mass. In addition, additives selected from various dispersants, plasticizers, dielectrics, insulators, etc. can also be contained in each paste as needed. Their total content can also be set to 10% by mass or less.

[0069] In the case of using the printing method, the paste for the dielectric layer and the paste for the internal electrode layer are printed or laminated on a substrate such as PET, cut into a specified shape, and then peeled off from the substrate to form a green sheet.

[0070] In addition, in the case of using the sheet method, a green sheet is formed using the paste for the dielectric layer, the paste for the internal electrode layer is printed thereon, then they are laminated, and then cut into a specified shape to form a green sheet.

[0071] Before firing, a debinding treatment is performed on the green sheet. The conditions for debinding are as follows: The heating rate is preferably set to 5 to 300 °C / h, the debinding temperature is preferably set to 180 to 900 °C, and the holding time is preferably set to 0.5 to 48 hours. In addition, regarding the atmosphere during the debinding treatment, it is preferably air or a reducing atmosphere (for example, a humidified N2 + H2 mixed gas atmosphere).

[0072] After debinding, the green sheet is fired. For example, it can be: The heating rate is set to 200 to 20000 °C / h, the firing temperature is set to 1150 to 1350 °C, and the holding time is set to 0.1 to 10 hours.

[0073] There is no particular limitation on the atmosphere during firing. It can be set to air or a reducing atmosphere. As the atmosphere gas in the case of setting it to a reducing atmosphere, for example, a mixed gas of humidified N2 and H2 can be used. In addition, the oxygen partial pressure can also be set to 1.0×10 －14 ~1.0×10 －9 MPa.

[0074] The lower the oxygen partial pressure during firing, the easier it is for rare earth elements to dissolve into the main phase particles. When comparing RA and RB, there is a particular tendency for RA to more easily dissolve into the main phase particles. That is, there is a tendency that when the oxygen partial pressure during firing is low, relatively more RB remains in the grain boundaries compared to RA. By adjusting the oxygen partial pressure, RA2 / RA1 or RB2 / RB1 can also be slightly adjusted. In addition, depending on the composition of the raw materials that make up the dielectric composition, particularly the content ratios of the various oxides described above, RA2 / RA1 or RB2 / RB1 can also be slightly adjusted.

[0075] Generally, the more the content of RA relative to RB, the more likely there is an increase in RA that does not dissolve into the main phase particles. The more the content of RB relative to RA, the more likely there is an increase in RB that does not dissolve into the main phase particles. Too much or too little content of M will affect the amounts of RA and RB that dissolve into the main phase particles with respect to the content of M.

[0076] In the present embodiment, it is preferable to perform an annealing treatment (oxidation treatment of the dielectric layer) on the fired element body. Specifically, the annealing temperature can also be set to 950 to 1100 °C. The holding time can also be set to 0.1 to 20 hours. The atmosphere during the oxidation treatment can also be set to humidified N2 gas (oxygen partial pressure: 1.0×10 －9 ~1.0×10 －6 MPa).

[0077] In the above-mentioned debinding treatment, firing, and annealing treatment, when using humidified N2 gas or a mixed gas, etc., it is sufficient to use, for example, a humidifier. In this case, the water temperature is preferably around 5 to 75 °C.

[0078] Regarding the debinding treatment, firing, and annealing treatment, they can be carried out continuously or independently.

[0079] For the capacitor element body obtained as described above, end face grinding is performed by, for example, barrel grinding or sandblasting, an external electrode paste is coated and fired to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

[0080] The multilayer ceramic capacitor of the present embodiment manufactured in this way is mounted on a printed circuit board by soldering or the like and used in various electronic devices and the like.

[0081] In addition, in the above-described embodiments, the fine structure is controlled particularly by controlling the composition and firing conditions, but the present invention is not limited to this method.

[0082] In the above-described embodiments, the case where the electronic component is a multilayer ceramic capacitor has been described, but the electronic component of the present invention is not limited to a multilayer ceramic capacitor, and any electronic component having the above-described dielectric composition is acceptable.

[0083] For example, it may also be a single-plate type ceramic capacitor in which a pair of electrodes are formed on the above-described dielectric composition. In addition, since the electronic component and the multilayer electronic component containing the dielectric composition of the present embodiment have a high relative dielectric constant and a high-temperature load life, they are particularly suitable for in-vehicle applications.

[0084] Examples

[0085] Hereinafter, the present invention will be described in further detail using examples and comparative examples. However, the present invention is not limited to the following examples.

[0086] Example 1

[0087] (Production of dielectric paste)

[0088] As the main component ABO3, BaTiO3 powder (Ba / Ti = 1.000) having an average particle diameter of 120 nm was prepared.

[0089] First, with respect to 100 moles of BaTiO3 powder, 0.6 moles of Dy2O3 powder as RA2O3, 0.3 moles of Y2O3 powder as RB2O3, 0.5 moles of SiO2 powder, 0.1 moles of MgO powder, 0.2 moles of MnO powder, and 0.5 moles of BaCO3 powder were weighed respectively.

[0090] Next, the weighed Y2O3, MgO, and SiO2 were wet-mixed with a ball mill for 8 hours. Then, the mixture was dried at 130°C and heat-treated at 800°C. The powder after the heat treatment was processed again with a ball mill for 8 hours and dried at 130°C, thereby obtaining a pre-fired powder (refer to Table 1A).

[0091] Then, the pre-fired powder, BaTiO3 powder, BaCO3, MnO, and Dy2O3 were mixed with a ball mill for 8 hours to obtain a dielectric raw material. In addition, BaCO3 is contained in the dielectric composition in the form of BaO after firing.

[0092] Next, 10 parts by mass of polyvinyl butyral resin, 5 parts by mass of dioctyl phthalate (DOP) as a plasticizer, and 100 parts by mass of ethanol as a solvent were mixed with 100 parts by mass of the dielectric raw material using a ball mill to make a paste, obtaining a paste for the dielectric layer.

[0093] (Preparation of paste for internal electrode layer)

[0094] Ni powder, terpineol, ethyl cellulose, and benzotriazole were prepared in a mass ratio of 44.6:52.0:3.0:0.4. Then, they were kneaded using a three-roll mill to make a paste, thereby preparing a paste for the internal electrode layer.

[0095] (Fabrication of green sheet)

[0096] The above-mentioned paste for the dielectric layer was used to form a green sheet on a PET film. Regarding the thickness of the green sheet, the thickness after drying was 0.8 to 1.2 μm. Next, the paste for the internal electrode layer was used to print the electrode layer on the green sheet in a specified pattern. Then, the green sheet was peeled off from the PET film, thereby fabricating a green sheet with an electrode layer. Next, multiple green sheets with electrode layers were laminated and pressure-bonded to obtain a green laminate. The green laminate was cut into a specified size to fabricate a green chip.

[0097] (Fabrication of component body)

[0098] Next, the obtained green chip was subjected to a debinding treatment, firing, and oxidation treatment to obtain a component body as a sintered body.

[0099] Regarding the conditions for the debinding treatment, the heating rate was set to 25 °C / h, the debinding temperature was set to 235 °C, the holding time was set to 8 hours, and the atmosphere was set to air.

[0100] Regarding the firing conditions, the heating rate was set to 200 °C / h, the firing temperature was set to 1120 °C (refer to Table 1A), the holding time was set to 2 hours, and the cooling rate was set to 200 °C / h. The atmosphere was set to a humidified N2 + H2 mixed gas atmosphere. The oxygen partial pressure was set to about 5.0×10 －11 MPa.

[0101] Regarding the oxidation treatment conditions, the heating rate and the cooling rate were set to 200 °C / h, the oxidation treatment temperature was set to 1050 °C, the holding time was set to 3 hours, the atmosphere was set to a humidified N2 gas atmosphere, and the oxygen partial pressure was set to 1.0×10 －7 MPa.

[0102] Humidification of the atmosphere during firing and oxidation treatment was carried out using a humidifier.

[0103] (Fabrication of multilayer ceramic capacitor specimen)

[0104] Next, after barrel polishing the end face of the obtained element body, Cu paste is coated as an external electrode, and firing treatment is performed in a reducing atmosphere to obtain Figure 1 the sample of the multilayer ceramic capacitor shown. The size of the obtained capacitor sample is 2.0 mm × 1.25 mm × 1.25 mm, the thickness of the dielectric layer is 1.0 μm or less, and the thickness of the internal electrode layer is 0.8 - 1.2 μm. In addition, the number of dielectric layers is set to 4 layers.

[0105] (Cross-sectional observation of dielectric layer)

[0106] The cross-sectional observation of the main phase particles 2a, 2b and triple-point segregation 2c contained in the dielectric layer 2 is carried out as follows. First, the obtained capacitor sample is cut along a plane perpendicular to the internal electrode layer, and the cut surface is wet-polished to obtain a polished surface. Then, chemical etching is performed on this polished surface. The polished surface at the center of the chip after chemical etching is observed by SEM.

[0107] In addition, using FIB (Focused Ion Beam), the cross-section of the obtained multilayer ceramic capacitor sample is sliced into flakes with a thickness of about 100 nm. STEM-EDS mapping analysis is performed on the cross-section of the sliced sample. The observation magnification at this time is 30,000 times to 100,000 times.

[0108] The mapping image obtained by STEM-EDS and the reflected electron image obtained by STEM are compared above. The particles with a higher concentration of Ba and Ti than the surroundings are set as the main phase particles 2a, 2b. The part with a circular equivalent diameter of 5 nm or more and 50 nm or less among the particles with an RB ratio higher than the field average and in contact with three or more main phase particles is set as the triple-point segregation 2c.

[0109] For at least 500 or more main phase particles 2a, 2b, the area is measured respectively by image analysis. The measured area is converted into 1.27 times the value of the Heywood diameter to obtain the spherical equivalent diameter, and the particle size distribution is obtained. Based on the obtained particle size distribution, the median value (for example, the particle size of the 250th out of 500) is set as D50, and the maximum value (for example, the particle size of the 500th out of 500) is set as D100.

[0110] In addition, based on the obtained mapping image, the center (the first point) of the main-phase particles 2a with a particle size of D50 or more is subjected to point analysis of its composition using EDS to obtain RA1 (mol%) and RB1 (mol%). In addition, the center (the second point) of the triple-point segregation 2c is subjected to point analysis of its composition using EDS to obtain RA2 (mol%) and RB2 (mol%). Thus, RA2 / RA1 and RB2 / RB1 are calculated. These results are shown in Table 1B.

[0111] (Measurement of magnetic properties)

[0112] The relative dielectric constant of the multilayer ceramic capacitor sample is measured using a digital LCR meter (4274A manufactured by YHP). Specifically, it is heat-treated at 150°C for 1 hour, and the capacitance is measured 24 hours later. The measurement conditions are set as: reference temperature 25°C, frequency 1.0 kHz, input signal level (measurement voltage) 1.0 Vrms. The relative dielectric constant is calculated from the capacitance. A relative dielectric constant of 3000 or more is considered good.

[0113] Regarding the high-temperature load life, for the multilayer ceramic capacitor sample, it is maintained at a state of applying a DC voltage of 20 V / μm at 180°C and the life time is measured, thereby evaluating the high-temperature load life. In this example, the time from the start of application until the insulation resistance decreases by one digit is set as the life time.

[0114] In addition, in this example, the above evaluation is performed on 20 capacitor samples, and the mean time to failure (MTTF) is calculated from the life time of each capacitor sample. When the MTTF is 10 hours or more, the high-temperature load life is judged to be good. These results are shown in Table 1B.

[0115] (Reliability)

[0116] After applying a voltage of 20.0 V / μm to each capacitor sample at 125°C for 3000 hours, a sample whose insulation resistance decreases by one digit from the insulation resistance at the start of voltage application is judged as a defective product, thereby obtaining the number of samples with low reliability among 2000 capacitor samples. In this example, when the number of samples with low reliability is 0, it is judged as good. The results are shown in Table 1B.

[0117] Examples 2 to 8

[0118] Except that the firing temperature is changed to the temperature described in Table 1A, the operation is the same as in Example 1 to produce a dielectric paste and produce a multilayer ceramic capacitor sample. For each multilayer ceramic capacitor sample, the same evaluation as in Example 1 is performed. The results are shown in Table 1B.

[0119] Examples 9 to 13

[0120] Except for changing the type or amount of RA2O3 or RB2O3 and the firing temperature to those described in Table 1A, the operation was the same as in Example 1 to produce a dielectric paste and a multilayer ceramic capacitor sample. For each multilayer ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 1B.

[0121] Example 14

[0122] Except for preparing the dielectric raw materials in the following order, the operation was the same as in Example 3 to produce a dielectric paste and a multilayer ceramic capacitor sample. Specifically, as the main component ABO3, 100 moles of barium titanate powder with an average particle size of 120 nm was used, and barium titanate particles coated with RB and coated with 0.3 moles of Y2O3, 0.1 moles of MgO, and 0.5 moles of SiO2 were prepared.

[0123] With respect to 100 moles of the main component composed of barium titanate particles coated with RB (the coating material is not included in the 100 moles), 0.5 moles of BaCO3, 0.2 moles of MnO, and 0.6 moles of Dy2O3 were added and wet-mixed with a ball mill for 8 hours to produce a dielectric raw material. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 1B.

[0124] Comparative Example 1

[0125] Except for preparing the dielectric raw materials in the following order, the operation was the same as in Example 3 to produce a dielectric paste and a multilayer ceramic capacitor sample. Specifically, with respect to 100 moles of barium titanate powder with an average particle size of 120 nm as the main component ABO3, Dy2O3, Y2O3, BaCO3, MnO, MgO, and SiO2 were weighed in the same molar ratio as in Example 3 and directly wet-mixed with a ball mill for 8 hours instead of obtaining a pre-fired powder to produce a dielectric raw material. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 2B. In addition, a part of the manufacturing conditions for producing the sample of Comparative Example 1 is described in Table 2A.

[0126] Comparative Examples 2 to 4

[0127] Except for changing the firing temperature to the value described in Table 2A, the operation was the same as in Comparative Example 1 to produce a dielectric paste and a multilayer ceramic capacitor sample. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 2B.

[0128] Comparative Examples 5 and 6

[0129] Except that the average particle diameter of the barium titanate powder was changed to the value described in Table 2A, the operation was carried out in the same manner as in Comparative Example 4 to produce a dielectric paste, and a multilayer ceramic capacitor sample was produced. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was carried out. The results are shown in Table 2B.

[0130] Comparative Example 7

[0131] Except that the firing temperature was changed to the value described in Table 2A and the average particle diameter of the barium titanate powder was changed to the value described in Table 2A, the operation was carried out in the same manner as in Comparative Example 6 to produce a dielectric paste, and a multilayer ceramic capacitor sample was produced. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was carried out. The results are shown in Table 2B.

[0132] Comparative Example 8

[0133] Except that RA2O3 such as Dy2O3 was not added, the operation was carried out in the same manner as in Comparative Example 1 to produce a dielectric paste, and a multilayer ceramic capacitor sample was produced. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was carried out. The results are shown in Table 2B.

[0134] Comparative Example 9

[0135] Except that RB2O3 such as Y2O3 was not added, the operation was carried out in the same manner as in Comparative Example 1 to produce a dielectric paste, and a multilayer ceramic capacitor sample was produced. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was carried out. The results are shown in Table 2B.

[0136] Comparative Example 10

[0137] Except that RA2O3 such as Dy2O3 was not added and 0.15 mol of Y2O3 and 0.15 mol of Yb2O3 were used as RB2O3, the operation was carried out in the same manner as in Comparative Example 8 to produce a dielectric paste, and a multilayer ceramic capacitor sample was produced. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was carried out. The results are shown in Table 2B.

[0138] Comparative Example 11

[0139] Except that RB2O3 such as Y2O3 was not added and 0.3 mol of Dy2O3 and 0.3 mol of Tb2O3 were used as RA2O3, the operation was carried out in the same manner as in Comparative Example 9 to produce a dielectric paste, and a multilayer ceramic capacitor sample was produced. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was carried out. The results are shown in Table 2B.

[0140] Comparative Example 12

[0141] Except for preparing the dielectric raw material in the following order, the operation was the same as in Example 14 to produce a dielectric paste and a multilayer ceramic capacitor sample. Specifically, barium titanate particles with an average particle diameter of 120 nm as the main component were prepared, and 0.6 mol of Dy2O3, 0.3 mol of Y2O3, 0.1 mol of MgO, and 0.2 mol of MnO were coated on 100 mol of barium titanate, and RA+RB-coated barium titanate particles were obtained. With respect to 100 mol of the main component of the barium titanate particles (the coating material is not included in the 100 mol), 0.5 mol of BaCO3 and 0.5 mol of SiO2 were added, and they were wet-mixed with a ball mill for 8 hours to produce a dielectric raw material. For the multilayer ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 2B.

[0142] Evaluation

[0143] From the results shown in Table 1A, Table 1B, Table 2A, and Table 2B, it can be seen that compared with each comparative example, in each example with a composition satisfying that RA2 / RA1 is 1.0 or more and 2.5 or less, and RB2 / RB1 is 3.0 or more and 9.0 or less, while maintaining a high relative dielectric constant, it has excellent high-temperature load life and product reliability. In addition, it can be seen that when D100 / D50 is preferably 1.8 or less, more preferably 1.4 or less, while maintaining a high relative dielectric constant, it has excellent high-temperature load life and product reliability.

[0144] Furthermore, it can be seen that when RA2 / RA1 is preferably 1.2 or more and 2.5 or less, more preferably 1.2 or more and 2.3 or less, while maintaining a high relative dielectric constant, the high-temperature load life is further improved. In addition, it can be seen that when RB2 / RB1 is 5.0 or more and 7.5 or less, while maintaining a high relative dielectric constant, the high-temperature load life is further improved.

[0145] In addition, it is considered that in Examples 1 to 14, since RA2 / RA1 is in the range of 1.0 or more and 2.5 or less, the main phase particles (crystal particles) observed in the compositions of these Examples 1 to 14 are all solid solution particles in which at least a part of the sub-components is sufficiently diffused to the vicinity of the center of the particles. In addition, it is considered that in Comparative Examples 5 to 7 and 12, since RA2 / RA1 is 5.5 or more, the main phase particles observed in the compositions of these comparative examples are core-shell structured particles in which the sub-components are not diffused to the center of the particles.

[0146] Table 1A

[0147]

[0148] Table 1B

[0149]

[0150] Table 2A

[0151]

[0152] Table 2B

[0153]

[0154] [Description of Reference Numerals]

[0155] 1 Multilayer Ceramic Capacitor; 10 Element Body; 2 Dielectric Layers; 2a, 2b Main Phase Particles; 2c Triple Point Segregation; 3 Internal Electrode Layer; 4 External Electrode.

Claims

1. A dielectric composition, wherein: having a main component represented by ABO3, a first rare earth element, and a second rare earth element, The first rare earth element is one or more selected from Dy, Tb, Gd and Eu, The second rare earth element is one or more selected from Y, Yb and Ho, In the cross section of the dielectric-porcelain composition, main phase grains and triple point segregation surrounded by three or more main phase grains are observed, When the concentration of the first rare earth element at the center of a specific main phase grain having a grain size equal to or larger than the average grain size D50 of the grain size of the main phase grains observed in the cross section is set to RA1, the concentration of the first rare earth element at the center of the triple point segregation is set to RA2, the concentration of the second rare earth element at the center of the specific main phase grain is set to RB1, and the concentration of the second rare earth element at the center of the triple point segregation is set to RB2, RA2 / RA1 is 1.0 or more and 2.5 or less, RB2 / RB1 is greater than or equal to 3.0 and less than or equal to 9.

0.

2. The dielectric composition according to claim 1, wherein The average particle size D50 of the main phase particles is 200 nm or more and 500 nm or less.

3. The dielectric composition according to claim 1, wherein A ratio D100 / D50 of the maximum particle size D100 of the main phase particles to the average particle size D50 of the main phase particles is 1.8 or less.

4. An electronic component, wherein: A dielectric composition according to any one of claims 1 to 3.

5. An electronic component, wherein: A dielectric layer comprising the dielectric composition according to any one of claims 1 to 3.

6. The electronic component according to claim 5, wherein The dielectric layer has a thickness of 2 μm or less.

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