Multilayer ceramic capacitor

Abstract

This multilayer ceramic capacitor 1 is provided with: an element part 10 that includes a plurality of dielectric ceramic layers 20 and a plurality of internal electrode layers 30, which are stacked in the thickness direction T; and external electrodes 11, 12 that are provided on the surface of the element part 10, and that are electrically connected to the internal electrode layers 30. The dielectric ceramic layers 20 include crystal grains 40 that are each composed of a perovskite composite oxide. The perovskite composite oxide contains barium (Ba), titanium (Ti), and a rare earth element (Re), and may additionally contain at least one of calcium (Ca) and zirconium (Zr). If GI(Re) is the Re / Ti atomic concentration ratio in an in-grain region GI of the crystal grains 40 and GB(Re) is the Re / Ti atomic concentration ratio in a grain boundary region GB of the crystal grains 40, 0.074 ≥ GI(Re) ≥ 0.005 (formula 1-1) and 1.10 ≥ GB(Re) / GI(Re) ≥ 0.90 (formula 1-2) are satisfied. If GI(Ca) is the Ca / Ti atomic concentration ratio in the in-grain region GI of the crystal grains 40 and GB(Ca) is the Ca / Ti atomic concentration ratio in the grain boundary region GB of the crystal grains 40, 0.250 ≥ GI(Ca) ≥ 0 (formula 2-1) and 1.10 ≥ GB(Ca) / GI(Ca) ≥ 0.90 (excluding the case of GI(Ca) = 0) (formula 2-2) are satisfied. If (Ba + Ca) / (Ti + Zr) is the atomic concentration ratio of the total of Ba and Ca to the total of Ti and Zr, 0.997 < (Ba + Ca) / (Ti + Zr) < 1.030 (formula 3) is satisfied.

Description

Multilayer ceramic capacitors

[0001] The present invention relates to a multilayer ceramic capacitor.

[0002] Patent Document 1 discloses a multilayer ceramic capacitor in which dielectric layers composed of barium titanate crystal particles having a calcium concentration of 0.2 atomic % or less and barium calcium titanate crystal particles having a calcium concentration of 0.4 atomic % or more and internal electrode layers are alternately stacked. The multilayer ceramic capacitor described in Patent Document 1 is characterized in that the barium titanate crystal particles and the barium calcium titanate crystal particles contain magnesium, two rare earth elements consisting of a combination of one of yttrium and holmium and one of terbium and dysprosium, and vanadium, and the ratio of the content of the magnesium and the rare earth element of yttrium and holmium in the central part of the barium titanate crystal particles to the content of the magnesium and the rare earth element of yttrium and holmium in the surface side of the barium titanate crystal particles is greater than the ratio of the content of the magnesium and the rare earth element of yttrium and holmium in the central part of the barium calcium titanate crystal particles to the content of the magnesium and the rare earth element of yttrium and holmium in the surface side of the barium calcium titanate crystal particles.

[0003] JP 2008-135638 A

[0004] According to Patent Document 1, the barium titanate crystal particles have a high degree of cubic crystallinity in the core-shell structure, and by having these highly cubic barium titanate crystal particles coexist between barium calcium titanate crystal particles, it is possible to obtain a dielectric ceramic composed of barium titanate crystal particles and barium calcium titanate crystal particles that has high insulation resistance even after firing and that shows little decrease in insulation resistance over time in a high-temperature load test.

[0005] However, in a multilayer ceramic capacitor in which a dielectric layer (hereinafter also referred to as a dielectric ceramic layer) is formed by crystal grains assuming a core-shell structure as described in Patent Document 1, localized electric field concentration occurs when a high electric field strength is applied, and there is a risk that insulation resistance will decrease over time in a high-temperature load test. Therefore, it can be said that there is still room for improvement from the viewpoint of obtaining a multilayer ceramic capacitor having a long high-temperature load life and high electrical reliability.

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a multilayer ceramic capacitor having a long high-temperature load life and high electrical reliability.

[0007] The multilayer ceramic capacitor of the present invention comprises an element body including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the thickness direction, and external electrodes provided on the surface of the element body and electrically connected to the internal electrode layers. The dielectric ceramic layers contain crystal grains composed of a perovskite-type complex oxide. The perovskite-type complex oxide contains barium (Ba), titanium (Ti), and a rare earth element (Re), and may further contain at least one of calcium (Ca) and zirconium (Zr). When GI(Re) is the atomic concentration ratio of Re / Ti in the intragranular region of the crystal grain, and GB(Re) is the atomic concentration ratio of Re / Ti in the grain boundary region of the crystal grain, the following formulas are satisfied: 0.074≧GI(Re)≧0.005, and 1-2: 1.10≧GB(Re) / GI(Re)≧0.90. When the atomic concentration ratio of Ca / Ti in the intragranular region of the crystal grain is GI(Ca) and the atomic concentration ratio of Ca / Ti in the grain boundary region of the crystal grain is GB(Ca), the following formula 2-1 is satisfied: 0.250≧GI(Ca)≧0, and the formula 2-2 is satisfied: 1.10≧GB(Ca) / GI(Ca)≧0.90 (excluding the case where GI(Ca)=0). When the atomic concentration ratio of the total of Ba and Ca to the total of Ti and Zr is (Ba+Ca) / (Ti+Zr), the formula 3 is satisfied: 0.997<(Ba+Ca) / (Ti+Zr)<1.030.

[0008] According to the present invention, it is possible to provide a multilayer ceramic capacitor having a long high-temperature accelerated life and high electrical reliability.

[0009] FIG. 1 is a perspective view schematically illustrating an example of a multilayer ceramic capacitor according to the present invention. FIG. 2 is an example of an LT cross-sectional view of the multilayer ceramic capacitor shown in FIG. 1 , including a length direction L and a thickness direction T along line II-II. FIG. 3 is an example of a WT cross-sectional view of the multilayer ceramic capacitor shown in FIG. 1 , including a width direction W and a thickness direction T along line III-III. FIG. 4A is an example of an enlarged cross-sectional view of a dielectric ceramic layer 20 sandwiched between internal electrode layers 30. FIG. 4B is a schematic diagram illustrating an example of crystal grains constituting the dielectric ceramic layer 20 in the region surrounded by a dashed line in FIG. 4A. FIG. 5A is a bright-field image of sample 1-1 taken by a transmission electron microscope. FIG. 5B is a mapping image showing the distribution of Dy element in sample 1-1.

[0010] The multilayer ceramic capacitor of the present invention will be described below. Note that the present invention is not limited to the following embodiments, and can be appropriately modified and applied within the scope of the present invention. Furthermore, a combination of two or more of the individual preferred configurations described in the following embodiments also constitutes the present invention.

[0011] In this specification, terms indicating the relationship between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms indicating the shape of elements are not expressions that only express a strict meaning, but are expressions that also include a range of substantial equivalence, for example, a difference of about a few percent.

[0012] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, and other scales may differ from those of the actual product. In the drawings, the same or equivalent parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0013] FIG. 1 is a perspective view schematically showing an example of a multilayer ceramic capacitor according to the present invention.

[0014] 1 includes an element body 10 and external electrodes 11 and 12 provided on the surface of the element body 10. The length direction, width direction, and thickness direction of the element body 10 are defined by double-headed arrows L, W, and T, respectively.

[0015] The element body 10 has, for example, a rectangular parallelepiped shape and includes a first main surface 10 a and a second main surface 10 b that face each other in a thickness direction T, a first side surface 10 c and a second side surface 10 d that face each other in a width direction W that is perpendicular to the thickness direction T, and a first end surface 10 e and a second end surface 10 f that face each other in a length direction L that is perpendicular to the thickness direction T and the width direction W.

[0016] At least one of the corners and ridges of the element body 10 may be rounded. Here, a corner is a portion where three faces of the element body 10 intersect, and a ridge is a portion where two faces of the element body 10 intersect.

[0017] The external electrode 11 is provided on the first end face 10e of the element body 10. The external electrode 11 may extend around to parts of the first main surface 10a, the second main surface 10b, the first side surface 10c, and the second side surface 10d of the element body 10.

[0018] The external electrode 12 is provided on the second end face 10f of the element body 10. The external electrode 12 may extend around the first main surface 10a, the second main surface 10b, the first side surface 10c, and part of the second side surface 10d of the element body 10.

[0019] There are no particular limitations on the dimensions of the multilayer ceramic capacitor 1. For example, the dimension in the length direction L is 0.4 mm or more and 5.7 mm or less, the dimension in the width direction W is 0.2 mm or more and 5.0 mm or less, and the dimension in the thickness direction T is 0.125 mm or more and 5.0 mm or less.

[0020] Fig. 2 is an example of an LT cross-sectional view including a length direction L and a thickness direction T along line II-II of the multilayer ceramic capacitor shown in Fig. 1. Fig. 3 is an example of a WT cross-sectional view including a width direction W and a thickness direction T along line III-III of the multilayer ceramic capacitor shown in Fig. 1.

[0021] The element body 10 includes a plurality of dielectric ceramic layers 20 and a plurality of internal electrode layers 30 stacked in the thickness direction T.

[0022] The internal electrode layers 30 include first internal electrode layers 31 and second internal electrode layers 32 arranged alternately in the thickness direction T.

[0023] The first internal electrode layer 31 extends to the first end face 10 e of the element body 10 and is electrically connected to the external electrode 11 there.

[0024] The second internal electrode layer 32 extends to the second end face 10 f of the element body 10 and is electrically connected to the external electrode 12 there.

[0025] The first internal electrode layer 31 and the second internal electrode layer 32 that face each other with the dielectric ceramic layer 20 interposed therebetween are not electrically connected. Therefore, when a voltage is applied between the first internal electrode layer 31 and the second internal electrode layer 32 via the external electrodes 11 and 12, electric charges are accumulated. The accumulated electric charges generate electrostatic capacitance, thereby exhibiting the function as a capacitive element.

[0026] An outer layer portion 25 formed by laminating only the dielectric ceramic layers 20 may be provided on the outside of the plurality of dielectric ceramic layers 20 and the plurality of internal electrode layers 30 laminated in the thickness direction T. The outer layer portion 25 is a dielectric ceramic layer located on both main surface sides of the element body portion 10 and located between each main surface and the internal electrode layer 30 closest to that main surface. On the other hand, the region sandwiched between both outer layer portions 25 can also be referred to as an inner layer portion.

[0027] Fig. 4A is an example of an enlarged cross-sectional view of a dielectric ceramic layer 20 sandwiched between internal electrode layers 30. Fig. 4B is a schematic diagram showing an example of crystal grains constituting the dielectric ceramic layer 20 in the region surrounded by the dashed line in Fig. 4A.

[0028] The dielectric ceramic layer 20 is made of ceramic. Specifically, the dielectric ceramic layer 20 contains, as a main component, crystal grains 40 (see FIGS. 4A and 4B ) made of a perovskite-type complex oxide. Hereinafter, the crystal grains 40 made of the perovskite-type complex oxide are also referred to as main crystal grains. The main crystal grains are made of barium titanate (BaTiO ３ Therefore, the dielectric ceramic layer 20 is made of BaTiO ３It can also be said that the material is a sintered body of a BaTiO ３ is a ferroelectric material that exhibits a tetragonal crystal structure at room temperature and has a high dielectric constant. ３ By using a compound containing such a compound as the main component, the dielectric constant of the dielectric ceramic layer 20 can be increased, which makes it possible to increase the capacitance of the capacitor.

[0029] In this specification, the term "main component" refers to the component that has the largest mass percentage in the ceramic. The mass percentage of the main component is not particularly limited as long as it is less than 100 mass%, and may be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, or 90 mass% or more.

[0030] BaTiO ３ The perovskite-based compound is not particularly limited as long as it is a perovskite-type composite oxide containing mainly Ba and Ti. For example, BaTiO ３ The compound is BaTiO ３ The Ba and / or Ti contained in the BaTiO may be partially substituted with other elements. For example, Ba may be partially substituted with alkaline earth metal elements such as strontium (Sr) and calcium (Ca), and Ti may be partially substituted with transition metal elements such as zirconium (Zr) and hafnium (Hf). ３ The molar ratio of the A-site element (Ba, Sr, Ca, etc.) to the B-site element (Ti, Zr, Hf, etc.) in the perovskite-based compound (hereinafter also referred to as the A / B ratio) is not strictly limited to 1:1, and deviations in the molar ratio of the A-site element to the B-site element are permissible as long as the perovskite-type crystal structure is maintained.

[0031] The perovskite complex oxide constituting the crystal particles 40 contains barium (Ba), titanium (Ti), and a rare earth element (Re). The rare earth element (Re) is a general term for elements constituting a group consisting of scandium (Sc) with atomic number 21, yttrium (Y) with atomic number 39, and lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71 in the periodic table. The perovskite complex oxide constituting the crystal particles 40 may contain one type of rare earth element (Re) or may contain a combination of multiple types of rare earth elements (Re). Furthermore, the rare earth element (Re) is present in the BaTiO 3 as the main crystal particles. ３ The rare earth element (Re) may be contained only in the BaTiO system compound, or may be contained together with the main crystal grains at the grain boundaries or triple points. ３ It may occupy the Ba site (A site) of the base compound, or the Ti site (B site), or it may occupy both sites.

[0032] The inclusion of a rare earth element (Re) in the dielectric ceramic layers 20 can improve the reliability of the multilayer ceramic capacitor 1 and various other characteristics such as the temperature characteristics of the dielectric constant. ３ The BaTiO-based compound may contain many oxygen vacancies generated during the firing process. These oxygen vacancies tend to lower the insulation resistance when accompanied by electron compensation, and tend to migrate under an electric field, causing a decrease in insulation resistance over time. Therefore, when a rare earth element (Re) is contained in the dielectric ceramic layer 20, the BaTiO ３ The rare earth element (Re) tends to dissolve in the Ba site or Ti site of the BaTiO based compound. The dissolved rare earth element (Re) acts as a donor or acceptor, hindering the movement of oxygen vacancies or suppressing the generation of conduction electrons. This reduces the deterioration of insulation resistance and improves the high-temperature load life. In addition, BaTiO ３ BaTiO compounds have a large temperature dependence of the dielectric constant near the Curie temperature Tc. ３ By dissolving a rare earth element (Re) in the compound, it becomes possible to make the temperature change of the dielectric constant flatter over a wide range including the Curie temperature Tc.

[0033] The type of rare earth element (Re) is not particularly limited, but the rare earth element (Re) preferably includes at least one element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and more preferably includes at least dysprosium (Dy). Dy is an element located near the middle of the lanthanoid group in the periodic table, and its ionic radius is also about intermediate. Therefore, BaTiO ３ The dielectric ceramic layer 20 may contain only Dy as the rare earth element (Re), or may contain other rare earth elements (Re) together with Dy.

[0034] The perovskite complex oxide constituting the crystal grains 40 may further contain at least one of calcium (Ca) and zirconium (Zr). In this case, these elements may be contained in any of the main crystal grains, grain boundaries, and triple points.

[0035] When the atomic concentration ratio of Re / Ti in the intragranular region GI of the crystal grain 40 is GI(Re) and the atomic concentration ratio of Re / Ti in the grain boundary region GB of the crystal grain 40 is GB(Re), the following relations are satisfied: Equation 1-1: 0.074≧GI(Re)≧0.005; and Equation 1-2: 1.10≧GB(Re) / GI(Re)≧0.90.

[0036] When a region surrounded by grain boundaries of crystal particles 40 is defined as a grain, a region formed by the boundaries of three or more adjacent grains is defined as a triple junction region TJ as shown in Fig. 4B. The triple junction region TJ does not refer to the triple junction itself, but refers to a region including the triple junction.

[0037] Next, as shown in Fig. 4B, among the regions centered on the same plane as the boundary surface between two adjacent grains, a region having a width of 10 nm that does not include the triple point region TJ is defined as a grain boundary region GB. The grain boundary region GB does not refer to the grain boundary itself, but refers to a region that includes the grain boundary.

[0038] As shown in FIG. 4B, the region inside the grain (grain interior) that does not include the grain boundary region GB and the triple point region TJ is defined as the grain interior region GI.

[0039] The above formulas 1-1 and 1-2 can be satisfied by uniformly dissolving the rare earth element (Re) in the entire region of the dielectric ceramic layer 20. When the dielectric ceramic layer 20 contains two or more rare earth elements (Re), it is sufficient that the total concentration of the rare earth elements (Re) satisfies formulas 1-1 and 1-2.

[0040] If formula 1-1 is not satisfied and GI(Re)>0.074, segregation of the rare earth element (Re) occurs, resulting in a significant decrease in electrical reliability. On the other hand, if GI(Re)<0.005, it becomes difficult to obtain the effect of improving electrical reliability due to the rare earth element (Re).

[0041] If formula 1-2 is not satisfied and GB(Re) / GI(Re)>1.10 or GB(Re) / GI(Re)<0.90, the difference in concentration of the rare earth element (Re) between the intragranular region GI and the grain boundary region GB becomes large, causing electric field concentration and reducing electrical reliability.

[0042] When the atomic concentration ratio of Re / Ti in the triple point region TJ of the crystal particle 40 is TJ(Re), at least one of the following may be satisfied, for example: Equation 1-3: 1.10≧TJ(Re) / GI(Re)≧0.90; and Equation 1-4: 1.10≧TJ(Re) / GB(Re)≧0.90.

[0043] When the atomic concentration ratio of Ca / Ti in the intragranular region GI of the crystal grain 40 is GI(Ca) and the atomic concentration ratio of Ca / Ti in the grain boundary region GB of the crystal grain 40 is GB(Ca), the following equations are satisfied: 0.250≧GI(Ca)≧0, and 1.10≧GB(Ca) / GI(Ca)≧0.90 (excluding the case where GI(Ca)=0). When GI(Ca)=0, only equation 2-1 needs to be satisfied.

[0044] When GI(Ca)>0, Ca is uniformly dissolved in the entire dielectric ceramic layer 20, thereby satisfying the above formulas 2-1 and 2-2.

[0045] On the other hand, when GI(Ca)=0, it is preferable that GB(Ca)=0.

[0046] If formula 2-1 is not satisfied and GI(Ca)>0.250, a secondary phase occurs in the dielectric ceramic layer 20, resulting in a significant decrease in electrical reliability.

[0047] If formula 2-2 is not satisfied and GB(Ca) / GI(Ca)>1.10 or GB(Ca) / GI(Ca)<0.90, the difference in Ca concentration between the intragranular region GI and the grain boundary region GB becomes large, causing electric field concentration and reducing electrical reliability.

[0048] When the atomic concentration ratio of Ca / Ti in the triple point region TJ of the crystal particle 40 is TJ(Ca), for example, at least one of the following may be satisfied: Expression 2-3: 1.10≧TJ(Ca) / GI(Ca)≧0.90 (excluding the case where GI(Ca)=0) and Expression 2-4: 1.10≧TJ(Ca) / GB(Ca)≧0.90 (excluding the case where GB(Ca)=0). When GI(Ca)=0, it is preferable that GB(Ca)=TJ(Ca)=0.

[0049] When the atomic concentration ratio of the total of Ba and Ca to the total of Ti and Zr is (Ba + Ca) / (Ti + Zr), the following formula 3 is satisfied: 0.997<(Ba + Ca) / (Ti + Zr)<1.030. As described above, the dielectric ceramic layer 20 may or may not contain Ca, and may or may not contain Zr.

[0050] If formula 3 is not satisfied and (Ba + Ca) / (Ti + Zr)≦0.997, a different phase is generated in the dielectric ceramic layer 20, resulting in a decrease in electrical reliability. Furthermore, insulation resistance also decreases. On the other hand, if (Ba + Ca) / (Ti + Zr)≧1.030, crystallinity decreases, resulting in a decrease in capacitance.

[0051] As described above, by satisfying the above formulas 1-1, 1-2, 2-1, 2-2, and 3, it is possible to obtain a multilayer ceramic capacitor 1 having a long high-temperature loaded life and high electrical reliability.

[0052] It is preferable that the formula 1-1 satisfies 0.074≧GI(Re)≧0.05, in which case the electrical reliability can be further improved.

[0053] It is preferable that the formula 2-1 satisfies 0.06≧GI(Ca)≧0.03, in which case the electrical reliability can be further improved.

[0054] The atomic concentration ratios of various elements in each region can be determined by analyzing a cross section of the dielectric ceramic layer 20 with a transmission electron microscope (TEM)-energy dispersive X-ray spectrometer (EDX) and performing image analysis on the obtained cross-sectional EDX image.

[0055] Specifically, the central portion of the multilayer ceramic capacitor 1 is polished to obtain an LT cross section, thereby exposing the dielectric ceramic layer 20. TEM observation is performed on the main crystal grains near the central portion of the exposed dielectric ceramic layer 20, and EDX is used to obtain a mapping image showing the atomic distribution within the crystal grain 40. It is preferable to perform the observation on 100 crystal grains 40.

[0056] The perovskite complex oxide constituting the crystal particles 40 may further contain at least one metal element (M) selected from the group consisting of vanadium (V), molybdenum (Mo), niobium (Nb), and tantalum (Ta). In this case, it is sufficient that these elements are contained in any of the main crystal particles, grain boundaries, and triple points. The metal element (M) preferably contains at least vanadium (V).

[0057] When the perovskite complex oxide constituting the crystal grain 40 contains a metal element (M), it is preferable that the following formula 4-1 be satisfied: 0.050≧GI(M)≧0.001, where GI(M) is the atomic concentration ratio of M / Ti in the intragranular region GI of the crystal grain 40, and GB(M) is the atomic concentration ratio of M / Ti in the grain boundary region GB of the crystal grain 40.

[0058] The above formula 4-1 can be satisfied by dissolving the metal element (M) in the dielectric ceramic layer 20. When two or more types of M are contained in the dielectric ceramic layer 20, it is sufficient that the total concentration of M satisfies formula 4-1.

[0059] If formula 4-1 is not satisfied and GI(M)>0.050, the insulation resistance is likely to decrease significantly. On the other hand, if GI(M)<0.001, it becomes difficult to obtain the effect of M in improving electrical reliability.

[0060] It is preferable that the formula 4-1 satisfies 0.005≧GI(M)≧0.003, in which case the electrical reliability can be further improved.

[0061] The perovskite complex oxide constituting the crystal particles 40 may further contain elements other than the above-mentioned barium (Ba), titanium (Ti), rare earth elements (Re), calcium (Ca), zirconium (Zr), and metal elements (M). Examples of other elements include manganese (Mn), magnesium (Mg), silicon (Si), and aluminum (Al). These elements may be contained in any of the main crystal particles, grain boundaries, and triple points.

[0062] The average thickness of the dielectric ceramic layers 20 is not particularly limited and may be, for example, 0.3 μm to 5 μm, 0.4 μm to 4 μm, 0.5 μm to 3 μm, 0.6 μm to 2 μm, or 0.7 μm to 1 μm. When the average thickness of the dielectric ceramic layers 20 is within the above range, deterioration of the insulating properties can be prevented. Furthermore, when the average thickness of the dielectric ceramic layers 20 is within the above range, the dielectric ceramic layers 20 can be made thinner, thereby improving the electrostatic capacitance. The number of layers of the dielectric ceramic layers 20 is, for example, 50 to 1,000.

[0063] The average particle size of the ceramic grains contained in the dielectric ceramic layer 20 is not particularly limited, but is preferably 100 nm or more and 400 nm or less, and more preferably 150 nm or more and 300 nm or less.

[0064] The internal electrode layers 30 contain a conductive metal. Examples of the conductive metal include electrode materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and alloys thereof. The internal electrode layers 30 may contain components other than the conductive metal. Examples of the other components include ceramic components that function as co-materials. Examples of the ceramic components include BaTiO contained in the dielectric ceramic layers 20. ３ compounds based on

[0065] The average thickness of the internal electrode layers 30 is not particularly limited, and is, for example, 0.3 μm or more and 0.7 μm or less. When the average thickness of the internal electrode layers 30 is within the above range, defects such as electrode discontinuities are suppressed. Furthermore, when the average thickness of the internal electrode layers 30 is within the above range, a decrease in the proportion of the electrically functional dielectric ceramic layers 20 in the capacitor is suppressed, and therefore, a decrease in capacitance can be suppressed.

[0066] The average thickness of the dielectric ceramic layers 20 and the internal electrode layers 30 is determined by observing the WT cross section of the element body 10 exposed by polishing with a scanning electron microscope (SEM), measuring the thickness on a total of five lines, including a center line passing through the center of the WT cross section along the thickness direction T, and two lines drawn equally spaced on both sides of this center line, and then averaging these five measured values.

[0067] The average grain size of the ceramic grains contained in the dielectric ceramic layer 20 can be measured by analyzing a cross-sectional image scanned with an SEM. For example, the average grain size of the ceramic grains can be measured using software for measuring average grain size in accordance with the JIS G 0551:2013 standard.

[0068] The configuration of the external electrodes 11 and 12 is not particularly limited. For example, the external electrodes 11 and 12 may have a laminated structure including, from the end face side of the multilayer ceramic capacitor 1, a base layer, a first plating layer, and a second plating layer. The base layer includes a metal such as nickel (Ni) or copper (Cu). The base layer may also include ceramic powder as a co-material in addition to the metal. The first plating layer is, for example, a nickel (Ni) plating layer. The second plating layer is, for example, a tin (Sn) plating layer. A conductive resin layer may be provided between the base layer and the first plating layer. The conductive resin layer is a layer containing conductive metal particles such as copper (Cu), silver (Ag), and nickel (Ni) and a resin. The external electrodes 11 and 12 may be electrically connected to the internal electrode layer 30 and function as external input / output terminals, and the configuration is not limited thereto.

[0069] The multilayer ceramic capacitor of the present invention may be produced by any method as long as it satisfies the above-mentioned requirements.

[0070] The method for manufacturing a multilayer ceramic capacitor of the present invention includes, for example, a step of preparing a green sheet containing at least barium (Ba), titanium (Ti), and a rare earth element (Re) (green sheet preparation step), a step of applying a conductive paste to the surface of the green sheet to obtain a green sheet on which an internal electrode pattern is formed (electrode pattern formation step), a step of stacking and pressing a plurality of green sheets to obtain a laminated block (stacking step), a step of cutting the obtained laminated block to obtain a laminated chip (cutting step), a step of subjecting the obtained laminated chip to a binder removal treatment and a firing treatment to obtain an element part (firing step), and a step of forming external electrodes on the obtained element part (external electrode formation step). Each step is described in detail below.

[0071] <Green Sheet Preparation Step> In the green sheet preparation step, a green sheet containing at least barium (Ba), titanium (Ti), and a rare earth element (Re) is prepared. The green sheet is a precursor of the dielectric ceramic layer and contains the main component raw material and the additive raw material of the dielectric ceramic layer. The method for preparing the green sheet is not particularly limited. For example, the main component raw material is mixed with the additive raw material to prepare a dielectric raw material, a binder and a solvent are added to and mixed with the obtained dielectric raw material to form a slurry, and the obtained slurry is molded into a green sheet.

[0072] BaTiO as the main component raw material ３ Powder of BaTiO ３ The ceramic compounds may be synthesized using known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides and / or chelate compounds, by known ceramic synthesis methods such as solid-phase reaction methods, hydrothermal synthesis methods, and alkoxide methods.

[0073] BaTiO ３ When synthesizing the Ba-based compound, for example, a Ba raw material, a Ti raw material, a Re raw material, and optionally a Ca raw material are wet-mixed in a ball mill, and the dried powder is heated at 1300° C. Furthermore, in order to facilitate the solid solution of Re and Ca, it is preferable to carry out wet-pulverization again after heating, and to carry out the heating operation three times.

[0074] As the Ba raw material, known ceramic raw materials such as Ba oxide, carbonate, acetate, etc. are used.

[0075] As the Ti raw material, known ceramic raw materials such as oxides, carbonates, acetates, and chlorides of Ti are used.

[0076] As the Re raw material, known ceramic raw materials such as oxides, carbonates, acetates, etc. of Re can be used.

[0077] As the Ca raw material, known ceramic raw materials such as oxides and carbonates of Ca are used.

[0078] The additive raw material may contain raw materials of other additive components such as Mn, Mg, Si, Al, and V. Furthermore, the main component BaTiO ３ In order to adjust the composition of the system compound, barium carbonate (BaCO ３ ) and titanium oxide (TiO ２ Ba raw materials and Ti raw materials such as Cr, Ni, and Ni may be added to the additive raw materials.

[0079] The slurry may be formed by a known method, for example, by mixing an organic binder and an organic solvent with the dielectric material. The organic binder may be a known binder such as a polyvinyl butyral binder. The organic solvent may be a known solvent such as toluene or ethanol. Additives such as a plasticizer may be added to the slurry as needed. Furthermore, the green sheet may be formed by a known method such as a doctor blade method or a lip method.

[0080] <Electrode Pattern Forming Process> In the electrode pattern forming process, a conductive paste is applied to the surface of a green sheet to obtain a green sheet on which an internal electrode pattern is formed. The internal electrode pattern becomes an internal electrode layer after firing. Examples of conductive metals contained in the conductive paste include conductive materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and alloys containing these. A ceramic component that acts as a co-material may also be added to the conductive paste. Examples of ceramic components include the main component raw material of the dielectric ceramic layer. The conductive paste may be applied by a known method such as screen printing or gravure printing.

[0081] <Lamination Step> In the lamination step, a plurality of green sheets are laminated and pressed together to obtain a laminated block. Green sheets on which internal electrode patterns are formed are used as the green sheets, but some green sheets on which internal electrode patterns are not formed may also be used. Lamination and pressing may be performed by known techniques.

[0082] <Cutting Step> In the cutting step, the obtained laminated block is cut to obtain laminated chips. The cutting may be performed so that chips of a predetermined size are obtained and at least a part of the internal electrode patterns are exposed on the end faces of the laminated chips.

[0083] <Firing Process> In the firing process, the obtained laminated chip is subjected to a binder removal process and a firing process to obtain an element part. The firing process causes the green sheet and the internal electrode pattern to be co-sintered to become a dielectric ceramic layer and an internal electrode layer, respectively. The conditions for the binder removal process can be determined depending on the type of organic binder contained in the green sheet and the internal electrode pattern. The firing process can be carried out at a temperature at which the laminated chip is sufficiently densified. For example, the firing process can be carried out under conditions of holding the temperature at 1200°C or higher and 1300°C or lower for 1 hour or longer and 10 hours or shorter. The firing process is carried out by heating the main component BaTiO ３ The reaction is carried out in an atmosphere in which the compound is not reduced and the oxidation of the conductive metal is suppressed. For example, the oxygen partial pressure is 1.9×10 －１１ MPa or more, 6.4 × 10 －９ MPa or less ２ -H ２ -H ２ The firing may be performed in a stream of O. Furthermore, an annealing treatment may be performed after firing.

[0084] The laminated chip is fired at a temperature rise rate of, for example, 400°C / min. Grain growth can be suppressed by increasing the temperature rise rate during firing. Furthermore, by adding a large amount of glass components such as Si and Al as additive raw materials, Re can be dissolved and discharged from the grain boundary region GB (see Figure 4B).

[0085] <External Electrode Forming Process> In the external electrode forming process, external electrodes are formed on the obtained element body. The external electrodes may be formed by a known method. For example, the external electrodes may be formed by applying and baking a conductive paste containing a metal such as silver (Ag), copper (Cu), and / or nickel (Ni) to the end faces of the element body where the internal electrode layers are drawn out and exposed. Alternatively, the external electrodes may be formed by applying a conductive paste to both end faces of the laminated chip before firing, followed by a firing process. Alternatively, the formed electrodes may be used as a base layer, and a plating film such as nickel (Ni) or tin (Sn) may be formed thereon. In this manner, a multilayer ceramic capacitor is produced.

[0086] The present specification discloses the following:

[0087] <1> An element body including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in a thickness direction, and external electrodes provided on a surface of the element body and electrically connected to the internal electrode layers, wherein the dielectric ceramic layers include crystal grains made of a perovskite complex oxide, the perovskite complex oxide includes barium (Ba), titanium (Ti), and a rare earth element (Re), and may further include at least one of calcium (Ca) and zirconium (Zr), and the element body satisfies the following formula 1-1: 0.074≧GI(Re)≧0.005, and formula 1-2: 1.10≧GB(Re) / GI(Re)≧0.90, a multilayer ceramic capacitor which satisfies the following formula 2-1: 0.250≧GI(Ca)≧0, and formula 2-2: 1.10≧GB(Ca) / GI(Ca)≧0.90 (excluding the case where GI(Ca)=0), where GI(Ca) is the atomic concentration ratio of Ca / Ti in an intragranular region of the crystal grain, and GB(Ca) is the atomic concentration ratio of Ca / Ti in a grain boundary region of the crystal grain; and where (Ba+Ca) / (Ti+Zr) is the atomic concentration ratio of the total of Ba and Ca to the total of Ti and Zr, then satisfies formula 3: 0.997<(Ba+Ca) / (Ti+Zr)<1.030.

[0088] <2> The multilayer ceramic capacitor according to <1>, wherein the formula 1-1 satisfies 0.074≧GI(Re)≧0.05.

[0089] <3> The multilayer ceramic capacitor according to <1> or <2>, wherein the formula 2-1 satisfies 0.06≧GI(Ca)≧0.03.

[0090] <4> The multilayer ceramic capacitor according to any one of <1> to <3>, wherein the perovskite complex oxide further contains at least one metal element (M) selected from the group consisting of vanadium (V), molybdenum (Mo), niobium (Nb), and tantalum (Ta).

[0091] <5> The multilayer ceramic capacitor according to <4>, wherein, when GI(M) is an atomic concentration ratio of M / Ti in an intragranular region of the crystal grain, and GB(M) is an atomic concentration ratio of M / Ti in a grain boundary region of the crystal grain, the following formula 4-1 is satisfied: 0.050≧GI(M)≧0.001.

[0092] <6> The multilayer ceramic capacitor according to <5>, wherein the formula 4-1 satisfies 0.005≧GI(M)≧0.003.

[0093] <7> The multilayer ceramic capacitor according to any one of <4> to <6>, wherein the metal element (M) includes at least vanadium (V).

[0094] <8> The multilayer ceramic capacitor according to any one of <1> to <7>, wherein the rare earth element (Re) includes at least one selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0095] <9> The multilayer ceramic capacitor according to <8>, wherein the rare earth element (Re) includes at least dysprosium (Dy).

[0096] EXAMPLES Hereinafter, examples will be given that more specifically disclose the multilayer ceramic capacitor of the present invention, but the present invention is not limited to these examples.

[0097] Example 1 In Example 1, the influence of the content of rare earth element (Re) was confirmed. In this example, vanadium (V) was used as an example of the metal element (M).

[0098] (1) Preparation of Multilayer Ceramic Capacitor A sample of a multilayer ceramic capacitor was prepared according to the following procedure.

[0099] First, BaCO ３ Powder, TiO ２ powder, rare earth oxide powder (e.g., Dy ２ O ３ Raw material powders such as SiO2 powder were wet-mixed in a ball mill, and the dried powder was heated at 1300° C. After heating, wet-pulverization was again performed, and heating at 1300° C. was repeated three times to obtain a dielectric powder.

[0100] A polyvinyl butyral binder and a plasticizer were added to the obtained dielectric powder, and then toluene and ethyl alcohol were added to form a slurry using a wet mill. The slurry was then molded into a green sheet. The obtained green sheet had a thickness of 1.7 μm after sintering and densification.

[0101] A conductive paste containing nickel as a main component was screen-printed on the surface of the obtained green sheet to form a pattern of a conductive paste layer that would become an internal electrode layer.

[0102] Then, 201 green sheets with conductive paste layers formed on their surfaces were stacked so that the sides on which the conductive paste layers were drawn out were staggered, and green sheet layers without conductive paste layers were placed on top and bottom, and the whole was then pressed together to produce a laminated block.

[0103] The resulting laminated block was cut into green laminated chips so that the size of the manufactured multilayer ceramic capacitors would be 3.2 mm x 1.6 mm.

[0104] The obtained green laminated chip was２ The binder was burned off by heat treatment at 280°C in an air stream. ２ -H ２ -H ２ In an O2 stream at 1260°C and an oxygen partial pressure of 1.6 x 10 －９ The mixture was fired under the condition of 100 MPa for 2 hours.

[0105] In the fired laminated chip, a conductive paste mainly composed of Cu was applied to the end surface where the internal electrode layer was drawn out, and baked at 800°C to form an external electrode, and further a Ni plating layer and a Sn plating layer were formed on the surface of the external electrode.

[0106] In this way, the multilayer ceramic capacitor of Example 1 was produced. The obtained multilayer ceramic capacitor had an outer shape of 3.2 mm long x 1.6 mm wide x 1.6 mm thick. The number of dielectric ceramic layers sandwiched between the internal electrode layers was 200, and each dielectric ceramic layer had a thickness of 1.7 μm.

[0107] (2) Evaluation The multilayer ceramic capacitor obtained in Example 1 was evaluated for various properties as follows.

[0108] <TEM Observation / EDX Analysis> The dielectric ceramic layers of the multilayer ceramic capacitor were observed using a field emission transmission electron microscope (FE-TEM), and component analysis of the microscopic region was performed using an energy dispersive X-ray spectrometer (EDX) attached to the TEM. The observation sample was prepared by processing the dielectric ceramic layer into thin pieces using the FIB lift-out method. Observation and analysis were performed under the following conditions.

[0109] - Apparatus: JEM-2200FS / Noran System 7 manufactured by JEOL Ltd. - Field of view: n=2 - Magnification: 60,000 times - Pixel size: 9.2 nm / 1 pixel - Spot diameter: 1 nmφ - Measurement: EDX accumulation number: 100

[0110] 5A is a transmission electron microscope bright-field image of sample 1-1, and FIG. 5B is a mapping image showing the distribution of Dy element in sample 1-1.

[0111] For each sample, GI(Re), GB(Re), GI(Ca) and GB(Ca) were measured, and the ratios of GB(Re) / GI(Re) and GB(Ca) / GI(Ca) were calculated. The results are shown in Table 1.

[0112] The rare earth elements (Re) are ABO ３ In the perovskite structure, rare earth elements (Re) occupy the A and B sites other than the oxygen (O) site, but the quantitative ratios occupying each site are not necessarily clear. However, it is true that rare earth elements (Re) substitute into the A and B sites in a certain ratio, forming a solid solution, forming a perovskite structure in this state. The A / B ratio shown in Table 1 refers to the ratio of (Ba + Ca) / (Ti + Zr) in which only Ba, Ca, Ti, and Zr are extracted from the perovskite structure in which rare earth elements (Re) are solid-solved.

[0113] <Reliability (MTTF)> A highly accelerated life test (HALT) was performed on the multilayer ceramic capacitor to determine the mean time to failure (MTTF). In the highly accelerated life test, the time to failure was measured under two measurement conditions. Specifically, a high-temperature load was applied to the sample under two conditions: a temperature of 175°C and a test voltage of 50V, and a temperature of 160°C and a test voltage of 50V. The time to failure was defined as the time when the insulation resistance became 200 kΩ or less. The time to failure was measured for 72 samples fabricated under the same conditions.

[0114] The obtained data was then plotted on Weibull probability paper to obtain a Weibull distribution. In the obtained Weibull distribution, the relationship between failure time and cumulative failure rate was linearly regressed, and the slope was determined as the shape parameter m. The failure time at which the cumulative failure rate reached 63.2% was then read, and the mean time to failure (MTTF) at a test voltage of 50 V was determined using this failure time and the shape parameter m, which corresponds to the slope of the regression line. Samples with an MTTF of 200 hours or more under either of the two temperature conditions of the highly accelerated life test were deemed to have passed the test. The results are shown in Table 1.

[0115] <XRD Analysis> The presence or absence of heterogeneous phases in the multilayer ceramic capacitor was evaluated using XRD (powder X-ray diffraction). Evaluation samples were prepared by crushing the multilayer ceramic capacitor in a mortar and removing the electrode portions. The heterogeneous phases (sub-component layers) described in the examples were Dy. ２ Ti ２ O ７ The presence of this crystalline phase significantly reduces the MTTF of the dielectric.

[0116] <Measurement conditions> Equipment: Bruker AXS D8 Advance Tube: Cu (enclosed X-ray tube) Optical system: Concentrated optical system

[0117] <Dielectric Constant> The capacitance of each sample was measured and the dielectric constant was calculated. The measurement was performed using an automatic bridge type measuring device by applying an AC voltage of 1 Vrms and 1 kHz at a temperature of 25°C. The dielectric constant εr was calculated from the obtained capacitance value, the opposing area of ​​the internal electrode layers, and the thickness of the dielectric ceramic layers.

[0118] <Specific Resistivity> The insulation resistance of each sample was measured and the specific resistance was calculated. Specifically, the insulation resistance was measured using an insulation resistance meter by applying a DC voltage of 10 V for 120 seconds at a temperature of 25°C. The specific resistance was then calculated from the obtained insulation resistance value, the opposing area of ​​the internal electrode layers, and the thickness of the dielectric ceramic layers.

[0119]

[0120] In Table 1, samples marked with an asterisk (*) are comparative examples that fall outside the scope of the present invention. The same applies to the following tables.

[0121] It can be seen from Table 1 that a multilayer ceramic capacitor having a long MTTF and high electrical reliability can be obtained by satisfying formula 1-1: 0.074≧GI(Re)≧0.005 and formula 1-2: 1.10≧GB(Re) / GI(Re)≧0.90. In particular, it can be seen that electrical reliability is further improved when formula 1-1 satisfies 0.074≧GI(Re)≧0.05.

[0122] Example 2 In Example 2, the influence of the calcium (Ca) content was confirmed.

[0123] CaCO added when producing dielectric powder ３ Except for varying the amount of powder, multilayer ceramic capacitors were fabricated in the same manner as in Example 1, and various properties were evaluated. The results are shown in Table 2.

[0124]

[0125] From Table 2, it can be seen that a multilayer ceramic capacitor having a long MTTF and high electrical reliability can be obtained by satisfying formula 2-1: 0.250≧GI(Ca)≧0 and formula 2-2: 1.10≧GB(Ca) / GI(Ca)≧0.90 (excluding the case where GI(Ca)=0). In particular, it can be seen that electrical reliability is further improved when formula 2-1 satisfies 0.06≧GI(Ca)≧0.03.

[0126] Example 3 In Example 3, the influence of the content of the metal element (M) was confirmed.

[0127] V added when producing dielectric powder ２ O ５ Except for varying the amount of powder, multilayer ceramic capacitors were fabricated in the same manner as in Example 1, and various properties were evaluated. The results are shown in Table 3.

[0128] <WD-XRF Analysis> The Ti content used to calculate the V / Ti atomic concentration ratio was analyzed by WD-XRF (wavelength dispersive X-ray fluorescence). Evaluation samples were prepared by crushing the multilayer ceramic capacitors in a mortar to a total weight of 0.1 g. The measurement conditions are as follows:

[0129] <Measurement conditions> Pretreatment: Glass bead method Measurement diameter: 30 nmφ

[0130] <ICP-AES analysis> The V content for calculating the V / Ti atomic concentration ratio was analyzed by ICP-AES (inductively coupled plasma atomic emission spectroscopy). Evaluation samples were prepared by crushing a multilayer ceramic capacitor in a mortar and dissolving it in acid. The measurement conditions are described below.

[0131] <Measurement conditions> Apparatus: iCAP6300 (manufactured by Thermo Fisher Scientific) Measurement wavelength range: 166 to 847 nm Analysis method: Acid dissolution method

[0132]

[0133] It can be seen from Table 3 that satisfying formula 4-1: 0.050≧GI(M)≧0.001 not only provides a long MTTF and high electrical reliability, but also a multilayer ceramic capacitor with high insulation resistance and excellent insulation properties. In particular, it can be seen that electrical reliability is further improved when formula 4-1 satisfies 0.005≧GI(M)≧0.003.

[0134] REFERENCE SIGNS LIST 1 multilayer ceramic capacitor 10 element body 10a first main surface 10b second main surface 10c first side surface 10d second side surface 10e first end surface 10f second end surface 11, 12 external electrode 20 dielectric ceramic layer 25 external layer 30 internal electrode layer 31 first internal electrode layer 32 second internal electrode layer 40 crystal grain GB grain boundary region GI intragrain region TJ triple point region L length direction T thickness direction W width direction

Claims

1. A ceramic ceramic ceramic material comprising: a body including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in a thickness direction; and external electrodes provided on a surface of the body and electrically connected to the internal electrode layers, wherein the dielectric ceramic layers include crystal grains made of a perovskite complex oxide, and the perovskite complex oxide includes barium (Ba), titanium (Ti) and a rare earth element (Re), and may further include at least one of calcium (Ca) and zirconium (Zr), wherein the atomic concentration ratio of Re / Ti in an intragranular region of the crystal grain is GI(Re) and the atomic concentration ratio of Re / Ti in a grain boundary region of the crystal grain is GB(Re), satisfying formula 1-1: 0.074≧GI(Re)≧0.005 and formula 1-2: 1.10≧GB(Re) / GI(Re)≧0.90, a multilayer ceramic capacitor which satisfies the following formula 2-1: 0.250≧GI(Ca)≧0, and formula 2-2: 1.10≧GB(Ca) / GI(Ca)≧0.90 (excluding the case where GI(Ca)=0), where GI(Ca) is the atomic concentration ratio of Ca / Ti in an intragranular region of the crystal grain, and GB(Ca) is the atomic concentration ratio of Ca / Ti in a grain boundary region of the crystal grain; and which satisfies the following formula 3: 0.997<(Ba+Ca) / (Ti+Zr)<1.030, where (Ba+Ca) / (Ti+Zr) is the atomic concentration ratio of the sum of Ba and Ca to the sum of Ti and Zr.

2. The multilayer ceramic capacitor according to claim 1, wherein the formula 1-1 satisfies 0.074≧GI(Re)≧0.

05.

3. The multilayer ceramic capacitor according to claim 1, wherein the formula 2-1 satisfies 0.06≧GI(Ca)≧0.

03.

4. The multilayer ceramic capacitor according to any one of claims 1 to 3, wherein the perovskite complex oxide further contains at least one metal element (M) selected from the group consisting of vanadium (V), molybdenum (Mo), niobium (Nb), and tantalum (Ta).

5. The multilayer ceramic capacitor according to claim 4, wherein the atomic concentration ratio of M / Ti in the intragranular region of the crystal grain is GI(M) and the atomic concentration ratio of M / Ti in the grain boundary region of the crystal grain is GB(M), satisfying formula 4-1: 0.050≧GI(M)≧0.

001.

6. The multilayer ceramic capacitor according to claim 5, wherein the formula 4-1 satisfies 0.005≧GI(M)≧0.

003.

7. The multilayer ceramic capacitor according to any one of claims 4 to 6, wherein the metal element (M) includes at least vanadium (V).

8. The multilayer ceramic capacitor according to any one of claims 1 to 7, wherein the rare earth element (Re) includes at least one selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

9. The multilayer ceramic capacitor according to claim 8, wherein the rare earth element (Re) includes at least dysprosium (Dy).

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