Dielectric composition and electronic component

Abstract

To provide a dielectric composition that maintains a high dielectric constant while exhibiting excellent high-temperature load life and reliability, and to provide an electronic component having the dielectric composition.SOLUTION: When a concentration of a first rare-earth element at a center of a specific main phase particle having a particle size equal to or more than an average particle size (D50) of a main phase particle that is observed cross-sectionally is RA1, a concentration of the first rare-earth element at a center of a triple point segregation phase is RA2, a concentration of a second rare-earth element at the center of the specific main phase particle is RB1, and a concentration of the second rare-earth element at the center of the triple point segregation phase is RB2, 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 (preferably 5.0 or more and 7.0 or less).SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] For example, with the increasing electrification of vehicles, dielectric compositions used in multilayer ceramic capacitors are required to have a large capacitance and high reliability. As a general technique for increasing the capacitance, techniques of "reducing the interlayer thickness of the dielectric layer" and "increasing the relative permittivity of the dielectric material" have been developed (for example, Patent Document 1 below).

[0003] In general, to increase the relative permittivity, it is common to increase the crystal particle size. However, increasing the crystal particle size may result in "a decrease in the number of particles between layers and a significant decrease in reliability when the interlayer of the dielectric layer is thin". Conversely, to ensure high reliability, it is necessary to reduce the crystal particle size. In that case, however, the relative permittivity tends to decrease, making it difficult to cope with an increase in capacitance.

[0004] When using fine dielectric powder during thinning, if grain growth is allowed during sintering to increase the relative permittivity, it is difficult to stably control the particle size to a predetermined value. Even when the target particle size is achieved, the particle size variation is large, resulting in a decrease in reliability. In addition, for example, dielectric compositions used in electronic components for applications such as in-vehicle use are also required to have excellent high-temperature load life.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of such a situation, and an object thereof is to provide a dielectric composition excellent in high-temperature load life and reliability while maintaining a high relative permittivity, and an electronic component having the dielectric composition.

Means for Solving the Problems

[0007] In order to achieve the above object, a dielectric composition according to an aspect of the present invention is a dielectric composition having a main component represented by ABO3, a first rare earth element, and a second rare earth element, wherein the first rare earth element is one or more selected from the group consisting of Dy, Tb, Gd, and Eu, the second rare earth element is one or more selected from the group consisting of Y, Yb, and Ho, on a cross section of the dielectric ceramic composition, main phase particles and triple point segregates surrounded by three or more of the main phase particles are observed, let the concentration of the first rare earth element at the center of a specific main phase particle having a particle size equal to or larger than the average particle size (D50) of the particle size of the main phase particles observed in the cross section be RA1, let the concentration of the first rare earth element at the center of the triple point segregate be RA2, let the concentration of the second rare earth element at the center of the specific main phase particle be RB1, let the concentration of the second rare earth element at the center of the triple point segregate be RB2, RA2 / RA1 is 1.0 or more and 2.5 or less (preferably 1.2 or more and 2.5 or less), RB2 / RB1 is 3.0 or more and 9.0 or less (preferably 5.0 or more and 7.5 or less).

[0008] As a result of intensive studies on the dielectric composition, it has been found that by setting RA2 / RA1 and RB2 / RB1 to a predetermined ratio, a dielectric composition excellent in high-temperature load life and reliability while maintaining a high relative permittivity can be realized, and the present invention has been completed. By setting RA2 / RA1 and RB2 / RB1 to a predetermined ratio, a dielectric composition excellent in high-temperature load life and reliability while maintaining a high relative permittivity can be realized.

[0009] Preferably, the average particle diameter (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 it within such a range, it becomes easier to realize a dielectric composition excellent in high-temperature load life and reliability while maintaining a high relative permittivity.

[0010] Preferably, the ratio (D100 / D50) of the maximum particle diameter (D100) of the main phase particles to the average particle diameter (D50) of the main phase particles is 1.8 or less, more preferably 1.4 or less. By setting it within such a range, it becomes easier to realize a dielectric composition excellent in high-temperature load life and reliability while maintaining a high relative permittivity.

[0011] An electronic component according to one aspect of the present invention has the dielectric composition described in any one of the above. Further, an electronic component according to another aspect 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 be 2 μm or less.

Brief Description of Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described.

[0014] As shown in FIG. 1, a multilayer ceramic capacitor 1 as an example of an electronic component according to the present embodiment has an element body 10 in which a dielectric layer 2 and an internal electrode layer 3 are alternately laminated. At both ends of the element body 10, a pair of external electrodes 4 that are electrically connected to the internal electrode layers 3 alternately arranged inside the element body 10 are formed. There is no particular limitation on the shape of the element body 10, but it is usually in the shape of a rectangular parallelepiped. Also, there is no particular limitation on the dimensions of the element body 10, and appropriate dimensions may be set according to the application.

[0015] The thickness (layer thickness) of each layer of the dielectric layer 2 is not particularly limited and can be arbitrarily set according to desired characteristics, applications, etc. Usually, the thickness of the dielectric layer 2 may be 20 μm or less, 10 μm or less, or 5 μm or less. However, in the present embodiment, even when it is 2 μm or less, or 1 μm or less, it has good characteristics.

[0016] Also, the number of laminated dielectric layers 2 is not particularly limited. In the multilayer ceramic capacitor of the present embodiment, for example, it may be 10 or more, 100 or more, or 200 or more.

[0017] In the present embodiment, the internal electrode layer 3 is laminated so that each end is alternately exposed on the surfaces of the two opposing end faces of the element body 10. The conductive material contained in the internal electrode layer 3 is not particularly limited. Examples of noble metals used as the conductive material include Pd, Pt, Ag-Pd alloys, etc. Examples of base metals used as the conductive material include Ni, Ni-based alloys, Cu, Cu-based alloys, etc. Note that Ni, Ni-based alloys, Cu, or Cu-based alloys may contain various trace components such as P and / or S in an amount of about 0.1 mass% or less. Also, the internal electrode layer 3 may be formed using a commercially available electrode paste. The thickness of the internal electrode layer 3 may be appropriately determined according to the application, etc.

[0018] The conductive material contained in the external electrode 4 is not particularly limited. For example, known conductive materials such as Ni, Cu, Sn, Ag, Pd, Pt, Au, or alloys thereof, and conductive resins may be used. The thickness of the external electrode 4 may be appropriately determined according to the application and the like.

[0019] The dielectric layer 2 is composed of the dielectric composition according to the present embodiment. The dielectric composition according to the present embodiment has a main component and a sub-component having a perovskite crystal structure represented by ABO3.

[0020] In the perovskite crystal structure represented by ABO3, A is one or more selected from barium (Ba), strontium (Sr), and calcium (Ca). It may be one or more selected from Ba and Sr. It may contain 80 mol% or more of Ba with respect to A, and may contain 90 mol% or more of Ba. A may be only Ba.

[0021] B is one or more selected from titanium (Ti) and zirconium (Zr), may contain hafnium (Hf), and may be one or more selected from Ti and Zr. B may contain Ti at 70 mol% or more, may contain Ti at 80 mol% or more, and may be only Ti.

[0022] Assuming that A is one or more selected from Ba, Sr, and Ca, and B is one or more selected from Ti and Zr, if the composition of the main component is specifically described, it is {Ba 1-x-y Ca x Sr y}O} u (Ti 1-z Zr z ) v O2.

[0023] 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, sintering tends to be insufficient, and the relative permittivity and reliability of the dielectric composition also tend to decrease. If u / v is too low, firing stability tends to deteriorate, and the temperature characteristics and reliability of the dielectric composition tend to decrease.

[0024] 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.

[0025] In the dielectric composition, the content C of RA with respect to the main component RA is not particularly limited, but in terms of RA2O3 conversion, 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. The content C of RB RB is not particularly limited, but in terms of RB2O3 conversion, 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, but in terms of SiO2 conversion, it may 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 M, the content of M may be 0.01 mol% or more and 1.0 mol% or less in terms of MO conversion.

[0026] Among the rare earth elements contained in the dielectric composition, as the first rare earth element RA, one or more selected from gadolinium (Gd), terbium (Tb), dysprosium (Dy), and europium (Eu) are included. Also, among the rare earth elements contained in the dielectric composition, as the second rare earth element RB, at least one or more selected from yttrium (Y), ytterbium (Yb), and holmium (Ho) are included. Further, the dielectric composition may contain other sub-component elements, and these elements may be contained as oxides.

[0027] RA corresponds to an element with a smaller difference in ionic radius from the A-site atoms among the rare earth elements 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 even more preferably RA is Dy. RB corresponds to an element with a larger difference in ionic radius from the A-site atoms among the rare earth elements 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 even more preferably RB is Y. By RA and RB being the above rare earth elements, the temperature characteristics and high-temperature load life are likely to be improved, and the reliability is also improved.

[0028] As shown in FIG. 2, the dielectric layer 2 of the present embodiment is composed of the above-described dielectric composition and has main phase particles (crystalline particles) 2a, 2b and triple point segregates 2c.

[0029] The main phase particles 2a, 2b of the present embodiment mainly contain a compound having a perovskite crystal structure represented by ABO3. The main component of the main phase particles 2a, 2b is a component that occupies 80 parts by mass or more, preferably 90 parts by mass or more, based on 100 parts by mass of the main phase particles. Note that the main phase particles 2a, 2b may contain sub-components other than the above main component.

[0030] The main phase particles 2a and 2b are preferably all main phase particles in which at least a part of the sub-components is completely solid-solved in the main component (hereinafter sometimes referred to as completely solid-solved main phase particles) within the observed range, but at least a part may contain particles having a core-shell structure. There is no particular limitation on the ratio of the completely solid-solved main phase particles to the main phase particles 2a and 2b, but it is preferably 90% or more on a number basis.

[0031] There is no particular limitation on the composition of the triple point segregation 2c shown in FIG. 2. The triple point segregation 2c contains RA and RB, and may contain at least one or more of Si, Mg, and other sub-components as necessary.

[0032] Hereinafter, in the dielectric composition constituting the dielectric layer 2 according to the present embodiment shown in FIG. 2, the relationship between the main phase particles 2a and 2b and the triple point segregation 2c will be described.

[0033] 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 diameter D50) of the particle sizes of the main phase particles 2a and 2b observed in the cross section within a predetermined 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.

[0034] The predetermined 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 the number of the main phase particles 2a and 2b is observed to be 500 or more (the cross section itself may be cross sections at a plurality of locations). Within the observation range of the cross section, assuming the area of the dielectric layer 2 is 100%, the total area of the main phase particles 2a and 2b is preferably observed within a range of 95.0% or more, and the total area of the triple point segregation 2c is preferably observed within a range of 0.1 to 5.0%. Also, within the same observation range, the total number of the triple point segregation 2c is preferably within a range of 0.2 to 20.0% with respect to the total number of the main phase particles 2a and 2b.

[0035] The discrimination, particle size, number, area, etc. of each of the main phase particles 2a and 2b and the triple point segregation 2c may be measured, for example, as follows.

[0036] First, the particle diameters of the main phase particles 2a and 2b can be obtained by performing image analysis on the SEM (Search Engine Marketing) image of the cross-section of the dielectric layer 2 as shown in, for example, FIG. 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 to the Heywood diameter (equivalent circle diameter), and further converted to the equivalent spherical diameter to obtain the particle size distribution. Based on the obtained particle size distribution, the median value (for example, the 250th particle diameter among 500 particles) can be set as D50, and the maximum value (for example, the 500th particle diameter among 500 particles) can be set as D100.

[0037] From the viewpoint of increasing the relative permittivity, D50 is preferably 190 nm or more, more preferably 200 nm or more. From the viewpoint of increasing the high-temperature load life, D50 is preferably 600 nm or less, more preferably 500 nm or less. Also, the ratio of D100 to D50 (D100 / D50) may be preferably 1.8 or less, more preferably 1.4 or less. In such a range, the high-temperature load life is improved.

[0038] In this embodiment, using a STEM (scanning transmission electron microscope), the mapping image obtained by STEM-EDS in the cross-section of the dielectric layer 2 is compared with the reflected electron image obtained by STEM, and particles with higher concentrations of the A-site and B-site in ABO3 compared to the surroundings can be used as the main phase particles 2a and 2b. Also, among the particles in which the concentration of RB (that is, Y or Yb) is higher than the average of the cross-sectional field of view and that are in contact with three or more main phase particles 2a and 2b, particles with an equivalent circle diameter of 5 nm or more and 50 nm or less can be used as the triple-point segregation products 2c. Also, the boundary between two main phase particles 2a and 2b is a grain boundary, and its thickness is 5 nm or less.

[0039] In this embodiment, at the center (the first point) of specific main-phase particles 2a having 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. Also, the concentration of RA at the center (the second point) of the triple-point segregation 2c can be measured as RA2, and the concentration of RB can be measured as RB2. Then, RA2 / RA1 and RB2 / RB1 can be calculated. The concentrations of these RAs and RBs may be measured, for example, by STEM-EDS or the like. The centers of the main-phase particles 2a and the triple-point segregation 2c may be centered on the centroids obtained from their respective areas.

[0040] In this embodiment, RA2 / RA1 is 1.0 or more and 2.5 or less, preferably 1.2 or more and 2.3 or less. Also, 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 becomes possible to improve the high-temperature load life and reliability while maintaining a high relative permittivity. The reason can be considered as follows, for example.

[0041] Generally, as the main-phase particles 2a and 2b grow in grain size during firing, the donor component (mainly RA) and the acceptor component (mainly RB, M) dissolve in the main-phase particles 2a and 2b. If the grain growth progresses too far at this time, the temperature characteristics deteriorate. Furthermore, the reliability of the dielectric composition deteriorates and the high-temperature load life deteriorates. In this embodiment, it is considered that the triple-point segregation (RA2 and RB2) stabilizes the grain growth of the main-phase particles (RA1 and RB1), suppresses local abnormal grain growth, and improves the high-temperature load life and reliability while maintaining a high relative permittivity. Also, it is considered that the fact that the first rare-earth element is dissolved even inside the main-phase particles (near the center) (RA2 / RA1 is 1.0 or more and 2.5 or less) improves the high-temperature load life and reliability while maintaining a high dielectric constant.

[0042] As a means for setting a predetermined ratio between RA2 / RA1 and RB2 / RB1, for example, a method of adding a compound that becomes a segregate containing a second rare earth element separately from a main-phase raw material that is a raw material for main-phase particles is exemplified. Also, a method such as including a compound raw material containing a first rare earth element in the main-phase raw material without heat-treating it together with a compound raw material containing other elements is effective.

[0043] An example of a method for manufacturing the multilayer ceramic capacitor 1 shown in FIG. 1 will be described below.

[0044] The multilayer ceramic capacitor 1 of the present embodiment is manufactured in the same manner as a conventional multilayer ceramic capacitor by producing a green chip by an ordinary printing method or sheet method using a paste, firing this, and then printing or transferring and firing an external electrode. The manufacturing method will be specifically described below.

[0045] First, a dielectric raw material for forming a dielectric layer is prepared, and this is made into a paint to prepare a paste for the dielectric layer.

[0046] As the dielectric raw material, a raw material for ABO3 which is the main component and raw materials for various other oxides are prepared. As these raw materials, oxides of the above-described components, mixtures thereof, and complex oxides can be used, but in addition, various compounds that become the above-described oxides and complex oxides by firing, for example, carbonates, oxalates, nitrates, hydroxides, organometallic compounds, etc. can be appropriately selected and mixed for use. In the present embodiment, the particle size of the raw material powder of ABO3 which is the main component is preferably 200 nm or less.

[0047] In this embodiment, an oxide of RB, an oxide of M (e.g., MgO), and a compound of Si are premixed, calcined, pulverized again, and dried to prepare a heat-treated powder. The obtained heat-treated powder is mixed with a raw material of the main component, an oxide of RA, and an oxide of M (e.g., MnO) 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 may be prepared, and a raw material of an oxide of A (e.g., a raw material of Ba oxide) contained separately from the main component, an oxide of RA, and an oxide of M (e.g., MnO) are mixed therewith to prepare a dielectric raw material. By doing so, the solubility of various rare earth elements in the main phase particles changes, and it becomes possible to adjust RA2 / RA1 and RB2 / RB1 within a predetermined range.

[0048] In this embodiment, a dielectric raw material in which the main component is coated with the above-described components may be used. Further, in addition to the raw material of the main component, for example, an oxide of RA, an oxide of RB, an oxide of M, and a compound of Si may be used.

[0049] Note that the raw material of ABO3 as the main component can be produced by various methods such as so-called solid-phase methods and those produced by various liquid-phase methods (e.g., oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.).

[0050] Furthermore, when a component other than the above-described components is contained in the dielectric layer 2, oxides of those components, mixtures thereof, or composite oxides can be used as raw materials of the components. In addition, various compounds that become the above-described oxides or composite oxides by firing can be used.

[0051] The content of each compound in the dielectric raw material may be determined so as to have the composition of the dielectric composition described above after firing.

[0052] The paste for the dielectric layer may be an organic-based paint obtained by kneading a dielectric raw material and an organic vehicle, or may be an aqueous paint.

[0053] An organic vehicle is a binder dissolved in an organic solvent. Known binders and solvents may be used.

[0054] When the dielectric layer paste is an aqueous paint, an aqueous vehicle in which a water-soluble binder, dispersant, etc. are dissolved in water may be kneaded with a dielectric raw material. The water-soluble binder is not particularly limited, and for example, polyvinyl alcohol, cellulose, a water-soluble acrylic resin, etc. may be used.

[0055] The paste for the internal electrode layer may be prepared by kneading a conductive material made of the above-described Ni or Ni alloy, or various oxides, organometallic compounds, resinate, etc. that become the above-described Ni or Ni alloy after firing, with the above-described organic vehicle. Further, the paste for the internal electrode layer may contain a co-material. The co-material is not particularly limited, but may have the same composition as the main component.

[0056] The paste for the external electrode may be prepared in the same manner as the above-described paste for the internal electrode layer.

[0057] There is no particular limitation on the content of the organic vehicle in each of the above-described pastes, and normal contents may be used, for example, about 1 to 15% by mass for the binder and about 10 to 60% by mass for the solvent. Further, each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, etc. as required. The total content of these may be 10% by mass or less.

[0058] When using the printing method, the dielectric layer paste and the internal electrode layer paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled off from the substrate to form a green chip.

[0059] When using the sheet method, a green sheet is formed using the dielectric layer paste, the internal electrode layer paste is printed thereon, and then these are laminated and cut into a predetermined shape to form a green chip.

[0060] Before firing, the green chip is subjected to a debinding process. As the debinding conditions, the heating rate is preferably 5 to 300 °C / hour, the debinding temperature is preferably 180 to 900 °C, and the holding time is preferably 0.5 to 48 hours. Also, the atmosphere in the debinding process is air or a reducing atmosphere (for example, a humidified N2 + H2 mixed gas atmosphere).

[0061] After debinding, the green chip is fired. For example, the heating rate may be 200 to 20000 °C / h, the firing temperature may be 1150 to 1350 °C, and the holding time may be 0.1 to 10 hours.

[0062] The atmosphere during firing is not particularly limited either. It may be air or a reducing atmosphere. As the atmosphere gas in the case of a reducing atmosphere, for example, a mixed gas of N2 and H2 can be humidified and used. Also, the oxygen partial pressure may be 1.0×10 -14 ~1.0×10 -9 MPa.

[0063] The lower the oxygen partial pressure during firing, the easier the solid solution of the rare earth elements into the main phase particles progresses. When comparing RA and RB, in particular, the solid solution of RA into the main phase particles tends to progress more easily. That is, when the oxygen partial pressure during firing is low, relatively more RB remains at the grain boundaries compared to RA. By adjusting the oxygen partial pressure, RA2 / RA1 and RB2 / RB1 can also be adjusted slightly. Also, RA2 / RA1 and RB2 / RB1 can be adjusted slightly depending on the raw material composition that becomes the dielectric composition, particularly the content ratios of the various oxides described above.

[0064] Generally, the higher the content of RA relative to RB, the more RA that does not dissolve in the main phase particles tends to increase. The higher the content of RB relative to RA, the more RB that does not dissolve in the main phase particles tends to increase. Whether the content of M is too high or too low, the content of M affects the amounts of RA and RB that dissolve into the main phase particles.

[0065] In this embodiment, it is preferable to perform an annealing process (oxidation process of the dielectric layer) on the element body after firing. Specifically, the annealing temperature may be 950 to 1100 °C. The holding time may be 0.1 to 20 hours. The atmosphere during the oxidation process may be humidified N2 gas (oxygen partial pressure: 1.0×10 -9 ~1.0×10 -6 MPa).

[0066] In the above-described debinding process, firing, and annealing process, when humidifying N2 gas, mixed gas, etc., for example, a wetter or the like may be used. In this case, the water temperature is preferably about 5 to 75 °C.

[0067] The debinding process, firing, and annealing process may be performed continuously or independently.

[0068] The end faces of the capacitor element body obtained as described above are polished, for example, by barrel polishing or sandblasting, an external electrode paste is applied 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.

[0069] The multilayer ceramic capacitor of this embodiment manufactured in this way is mounted on a printed circuit board or the like by soldering or the like and used in various electronic devices and the like. Note that in the above-described embodiment, the fine structure is controlled by particularly controlling the composition and firing conditions, but the present invention is not limited to this method.

[0070] In the above-described embodiment, the case where the electronic component is a multilayer ceramic capacitor has been described. However, the electronic component according to the present invention is not limited to a multilayer ceramic capacitor, and any electronic component having the above-described dielectric composition may be used.

[0071] For example, it may be a single-layer ceramic capacitor in which a pair of electrodes is formed on the dielectric composition described above. Further, the electronic component and the multilayer electronic component including the dielectric composition according to the present embodiment have a high relative permittivity and a high high-temperature load life, and thus are particularly suitably used for in-vehicle applications.

Examples

[0072] Hereinafter, the present invention will be described in more detail using examples and comparative examples. However, the present invention is not limited to the following examples.

[0073] Example 1 (Preparation of Dielectric Paste) As the main component ABO3, BaTiO3 powder (Ba / Ti = 1.000) with an average particle diameter of 120 nm was prepared.

[0074] First, for 100 mol of BaTiO3 powder, 0.6 mol of Dy2O3 powder as RA2O3, 0.3 mol of Y2O3 powder as RB2O3, 0.5 mol of SiO2 powder, 0.1 mol of MgO powder, 0.2 mol of MnO powder, and 0.5 mol of BaCO3 powder were weighed respectively.

[0075] Next, the weighed Y2O3, MgO, and SiO2 were wet-mixed in a ball mill for 8 hours. Then, the mixture was dried at 130°C and heat-treated at 800°C. The heat-treated powder was processed in a ball mill for 8 hours again and dried at 130°C to obtain a calcined powder (see Table 1A).

[0076] Thereafter, the calcined powder, BaTiO3 powder, BaCO3, MnO, and Dy2O3 were mixed in a ball mill for 8 hours to obtain a dielectric raw material. Note that BaCO3 is contained in the dielectric composition as BaO after firing.

[0077] 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 alcohol as a solvent were mixed with 100 parts by mass of the dielectric raw material using a ball mill to form a paste, thereby obtaining a paste for the dielectric layer.

[0078] (Preparation of Paste for Internal Electrode Layer) Ni powder, terpineol, ethyl cellulose, and benzotriazole were prepared such that the mass ratio was 44.6:52.0:3.0:0.4. Then, these were kneaded using a three-roll mill and made into a paste to prepare a paste for the internal electrode layer.

[0079] (Preparation of Green Chip) A green sheet was formed on a PET film using the above paste for the dielectric layer. The thickness of the green sheet was set such that the thickness after drying was 0.8 - 1.2 μm. Next, an electrode layer was printed in a predetermined pattern on the green sheet using the paste for the internal electrode layer. Then, the green sheet was peeled from the PET film to prepare a green sheet having an electrode layer. Next, a plurality of green sheets having electrode layers were laminated and pressure-bonded to obtain a green laminate. The green laminate was cut into a predetermined size to prepare a green chip.

[0080] (Preparation of Element Body) Next, the obtained green chip was subjected to a debinding treatment, firing, and oxidation treatment to obtain an element body which is a sintered body.

[0081] The debinding treatment conditions were a heating rate of 25°C / h, a debinding temperature of 235°C, a holding time of 8 hours, and an atmosphere of air. The firing conditions were a heating rate of 200°C / h, a firing temperature of 1120°C (see Table 1A), a holding time of 2 hours, and a cooling rate of 200°C / h. The atmosphere was a humidified N2 + H2 mixed gas atmosphere. The oxygen partial pressure was about 5.0×10 -11 MPa.

[0082] The acid treatment conditions were as follows: the heating rate and the cooling rate were 200 °C / h, the acid treatment temperature was 1050 °C, the holding time was 3 hours, the atmosphere was a humidified N2 gas atmosphere, and the oxygen partial pressure was 1.0×10 -7 MPa.

[0083] A wetter was used for humidifying the atmosphere during firing and acid treatment.

[0084] (Fabrication of Multilayer Ceramic Capacitor Samples) Next, after barrel-polishing the end faces of the obtained element bodies, Cu paste was applied as an external electrode, and baking treatment was performed in a reducing atmosphere to obtain samples of the multilayer ceramic capacitor shown in Fig. 1. The size of the obtained capacitor samples was 2.0 mm × 1.25 mm × 1.25 mm, the thickness of the dielectric layer was 1.0 μm or less, and the thickness of the internal electrode layer was 0.8 - 1.2 μm. Also, the number of dielectric layers was 4 layers.

[0085] (Cross-Section Observation of Dielectric Layer) The cross-section observation of the main phase particles 2a, 2b and triple-point segregates 2c contained in the dielectric layer 2 was performed as follows. First, the obtained capacitor sample was cut along a plane perpendicular to the internal electrode layer, and the cut surface was wet-polished to obtain a polished surface. Next, chemical etching was performed on the polished surface. The polished surface at the center of the chip after chemical etching was observed by SEM.

[0086] Also, using FIB (Focused Ion Beam), the cross-section of the obtained multilayer ceramic capacitor sample was sliced into pieces with a thickness of about 100 nm. STEM-EDS mapping analysis was performed on the cross-section of the sliced sample. The observation magnification at this time was set to 30,000 times to 100,000 times.

[0087] By comparing the mapping image obtained by the above STEM-EDS with the backscattered electron image obtained by STEM, the particles with higher Ba and Ti concentrations than the surroundings were defined as the main phase particles 2a, 2b. Among the particles where RB was higher than the field average and in contact with three or more main phase particles, the locations where the equivalent circle diameter was 5 nm or more and 50 nm or less were defined as the triple-point segregates 2c.

[0088] For at least 500 or more primary phase particles 2a and 2b, the area was measured by image analysis respectively. The value obtained by converting the measured area into the Heywood diameter was multiplied by 1.27 to obtain the equivalent spherical diameter, and the particle size distribution was obtained. Based on the obtained particle size distribution, the median value (for example, the 250th particle size among 500) was defined as D50, and the maximum value (for example, the 500th particle size among 500) was defined as D100.

[0089] Also, based on the obtained mapping image, the composition of the center (the first point) of the primary phase particle 2a with a particle diameter of D50 or more was analyzed by point analysis using EDS, and RA1 (mol%) and RB1 (mol%) were obtained. Also, the composition of the center (the second point) of the triple point segregation 2c was analyzed by point analysis using EDS, and RA2 (mol%) and RB2 (mol%) were obtained. From these, RA2 / RA1 and RB2 / RB1 were calculated. These results are shown in Table 1B.

[0090] (Measurement of magnetic properties) The relative permittivity was measured for the multilayer ceramic capacitor sample using a digital LCR meter (4274A manufactured by YHP). Specifically, the capacitance after heat treatment at 150°C for 1 hour and 24 hours later was measured. The measurement conditions were a reference temperature of 25°C, a frequency of 1.0 kHz, and an input signal level (measurement voltage) of 1.0 Vrms. The relative permittivity was calculated from the capacitance. A relative permittivity of 3000 or more was considered good.

[0091] The high-temperature load life was evaluated for the multilayer ceramic capacitor sample by measuring the life time while maintaining a DC voltage of 20 V / μm applied at 180°C. In this example, the time from the start of application until the insulation resistance dropped by one digit was defined as the life time. Also, in this example, the above evaluation was performed for 20 capacitor samples, and the mean time to failure (MTTF) was calculated from the life time of each capacitor sample. When the MTTF was 10 hours or more, the high-temperature load life was judged to be good. These results are shown in Table 1B.

[0092] (Reliability) For each capacitor sample, after performing a voltage application test of 20.0 V / μm at 125°C for 3000 hours, a sample with a one-digit drop in insulation resistance from the insulation resistance at the start of voltage application was determined to be a defective product, and among 2000 capacitor samples, the number of samples with low reliability was obtained. In this example, it was judged to be good when the number of samples with low reliability was 0. The results are shown in Table 1B.

[0093] Examples 2 - 8 Except that the firing temperature was changed to the content described in Table 1A, a dielectric paste was prepared and laminated ceramic capacitor samples were prepared in the same manner as in Example 1. For each laminated ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 1B.

[0094] Examples 9 - 13 Except that the types and amounts of RA2O3 and RB2O3 and the firing temperature were changed to the content described in Table 1A, a dielectric paste was prepared and laminated ceramic capacitor samples were prepared in the same manner as in Example 1. For each laminated ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 1B.

[0095] Example 14 Except that the dielectric raw material was prepared by the following procedure, a dielectric paste was prepared and laminated ceramic capacitor samples were prepared in the same manner as in Example 3. Specifically, as the main component ABO3, 0.3 mol of Y2O3, 0.1 mol of MgO, and 0.5 mol of SiO2 were coated on 100 mol of barium titanate powder with an average particle diameter of 120 nm to prepare RB-coated barium titanate particles.

[0096] For 100 mol of the main component composed of barium titanate particles of the RB coat (100 mol does not include the coating material), 0.5 mol of BaCO3, 0.2 mol of MnO, and 0.6 mol of Dy2O3 were added, and these were wet-mixed in a ball mill for 8 hours to prepare a dielectric raw material. For the laminated ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 1B.

[0097] Comparative Example 1 A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Example 3, except that the dielectric raw material was prepared by the following procedure. Specifically, for 100 mol of barium titanate powder with an average particle diameter of 120 nm as the main component ABO3, Dy2O3, Y2O3, BaCO3, MnO, MgO, and SiO2 were weighed in the same molar ratios as in Example 3, and these were directly wet-mixed in a ball mill for 8 hours without obtaining a calcined powder to prepare a dielectric raw material. For the laminated ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 2B. Note that Table 2A describes part of the manufacturing conditions for preparing the sample according to Comparative Example 1.

[0098] Comparative Examples 2 - 4 A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 1, except that the firing temperature was changed to the value described in Table 2A. For the laminated ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 2B.

[0099] Comparative Examples 5 and 6 A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 4, except that the average particle diameter of the barium titanate powder was changed to the value described in Table 2A. For the laminated ceramic capacitor sample, the same evaluation as in Example 1 was performed. The results are shown in Table 2B.

[0100] Comparative Example 7 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. Otherwise, a dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 6. The laminated ceramic capacitor sample was evaluated in the same manner as in Example 1. The results are shown in Table 2B.

[0101] Comparative Example 8

[0102] A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 1, except that RA2O3 such as Dy2O3 was not added. The laminated ceramic capacitor sample was evaluated in the same manner as in Example 1. The results are shown in Table 2B.

[0103] Comparative Example 9 A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 1, except that RB2O3 such as Y2O3 was not added. The laminated ceramic capacitor sample was evaluated in the same manner as in Example 1. The results are shown in Table 2B.

[0104] Comparative Example 10 A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 8, 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 laminated ceramic capacitor sample was evaluated in the same manner as in Example 1. The results are shown in Table 2B.

[0105] Comparative Example 11 A dielectric paste was prepared and a laminated ceramic capacitor sample was prepared in the same manner as in Comparative Example 9, 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 laminated ceramic capacitor sample was evaluated in the same manner as in Example 1. The results are shown in Table 2B.

[0106] Comparative Example 12 A dielectric paste was prepared in the same manner as in Example 14 except that the dielectric raw material was prepared by the following procedure. Specifically, for 100 mol of barium titanate with an average particle diameter of 120 nm as the main component, 0.6 mol of Dy2O3, 0.3 mol of Y2O3, 0.1 mol of MgO, and 0.2 mol of MnO were used to coat barium titanate particles with an RA+RB coating. Barium carbonate was added in an amount of 0.5 mol and silica was added in an amount of 0.5 mol with respect to 100 mol of the main component of the barium titanate particles (100 mol does not include the coating material), and these were wet-mixed in a ball mill for 8 hours to prepare a dielectric raw material. The same evaluation as in Example 1 was performed on the laminated ceramic capacitor sample. The results are shown in Table 2B.

[0107] Evaluation From the results shown in Table 1A, Table 1B, Table 2A and Table 2B, in each example satisfying the configuration where 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, it was found that, compared with each comparative example, while maintaining a high relative permittivity, the high-temperature load life and product reliability are excellent. Also, when D100 / D50 is preferably 1.8 or less, more preferably 1.4 or less, it was found that, while maintaining a high relative permittivity, the high-temperature load life and product reliability are excellent.

[0108] Furthermore, 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, it was found that the high-temperature load life is further improved while maintaining a high relative permittivity. Also, when RB2 / RB1 is 5.0 or more and 7.5 or less, it was found that the high-temperature load life is further improved while maintaining a high relative permittivity.

[0109] 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 (crystalline particles) observed in the compositions of these Examples 1 to 14 are considered to be all solid solution particles in which at least a part of the sub-components is sufficiently diffused near the center of the particles. Further, in Comparative Examples 5 to 7 and 12, since RA2 / RA1 is 5.5 or more, the main phase particles observed in the compositions according to these Comparative Examples are considered to be particles having a core-shell structure in which the sub-components are not diffused to the center of the particles.

[0110]

Table 1A

[0111]

Table 1B

[0112]

Table 2A

[0113]

Table 2B

Explanation of Reference Numerals

[0114] 1… Multilayer ceramic capacitor 10… Element body 2… Dielectric layer 2a, 2b… Main phase particles 2c… Triple point segregation 3… Internal electrode layer 4… External electrode

Claims

1. ABO 3 A dielectric composition having a main component represented by, a first rare earth element, and a second rare earth element, The first rare earth element is one or more selected from the group consisting of Dy, Tb, Gd, and Eu, The second rare earth element is one or more selected from the group consisting of Y, Yb, and Ho, In the cross-section of the dielectric ceramic composition, main phase particles and triple point segregates surrounded by three or more of the main phase particles are observed, Let the concentration of the first rare earth element at the center of specific main phase particles having a particle size equal to or greater than the average particle size (D50) of the main phase particles observed in the cross-section be RA1, Let the concentration of the first rare earth element at the center of the triple point segregate be RA2, Let the concentration of the second rare earth element at the center of the specific main phase particles be RB1, Let the concentration of the second rare earth element at the center of the triple point segregate be RB2, RA2 / RA1 is 1.0 or more and 2.5 or less, A dielectric composition in which RB2 / RB1 is 3.0 or more and 9.0 or less.

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 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.

4. An electronic component having the dielectric composition according to any one of claims 1 to 3.

5. An electronic component having a dielectric layer composed of the dielectric composition according to any one of claims 1 to 3.

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

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