Multilayer ceramic capacitor

Abstract

The invention provides a laminated ceramic capacitor with excellent reliability. The multilayer ceramic capacitor includes: a body portion including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the thickness direction, the body portion including a first main surface and a second main surface facing each other in the thickness direction, a first side surface and a second side surface facing each other in the width direction, and a first end surface and a second end surface facing each other in the length direction; and a pair of external electrodes provided on the first end surface and the second end surface, respectively, and electrically connected to the plurality of internal electrode layers. The dielectric ceramic layer contains, as a main component, crystal grains comprising a perovskite-type composite oxide containing barium (Ba) and titanium (Ti), and further contains a rare earth element (Re). In a cross section including the thickness direction, the dielectric ceramic layer includes a rare earth high-concentration region in which the molar ratio (Re / Ti ratio) of a rare earth element (Re) to titanium (Ti) is 0.04-0.30 in an area ratio of 50% or more, and in the cross section, the CV value of the line segment ratio in the thickness direction of the rare earth high-concentration region is 25% or less.

Description

Technical Field

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

[0002] With the miniaturization of electronic devices typified by mobile phones and the high-speed operation of CPUs, the demand for multilayer ceramic capacitors (MLCCs) has been increasing. A multilayer ceramic capacitor has a structure in which dielectric layers and internal electrode layers are alternately laminated. Due to the thin high-dielectric-constant dielectric layers, it has a large electrostatic capacitance despite its small size. Although multilayer ceramic capacitors using various materials are known, multilayer ceramic capacitors using barium titanate (BaTiO3)-based compounds for the dielectric layers and base metals such as nickel (Ni) for the internal electrode layers are widely used because they are inexpensive and exhibit high characteristics.

[0003] For miniaturization and large capacitance of multilayer ceramic capacitors, it is important to make the dielectric layers thinner. However, if the thinning of the dielectric layers is advanced, there is a problem that the insulation resistance life between the internal electrode layers is shortened, resulting in a decrease in reliability. To address such a problem, technologies have been proposed in which additives such as rare earth elements (RE) and magnesium (Mg) are added to the dielectric layers containing BaTiO3-based compounds, thereby seeking to extend the insulation resistance life and improve the reliability.

[0004] For example, Patent Document 1 discloses a dielectric ceramic composition containing the following main components: barium titanate, at least one selected from europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, and ytterbium oxide, barium zirconate, magnesium oxide, and manganese oxide, and represented by a specific composition formula (Claim 1 of Patent Document 1). In addition, Patent Document 1 describes the following: applying this ceramic composition to the dielectric ceramic layer of a multilayer ceramic capacitor whose internal electrode contains nickel or a nickel alloy; and when used under a high electric field strength, the product of the insulation resistance and the electrostatic capacitance (CR product) is high, the dielectric strength is high, and weather resistance such as high-temperature load and moisture resistance is excellent (Claims 4 and

[0007] of Patent Document 1).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 3334607 Gazette Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] With the progress of electronic components and electronic devices, further miniaturization and higher capacitance of multilayer ceramic capacitors are expected. In addition, as the applications of multilayer ceramic capacitors expand, the requirement for improving their reliability becomes increasingly high. Therefore, a multilayer ceramic capacitor with excellent reliability as follows is required, that is, although the thinning of the dielectric layer is advanced, the insulation characteristics are still high, and furthermore, the deterioration is less even under high temperature and high humidity conditions. However, regarding the previously proposed technologies, although there are certain effects, there is still room for improvement.

[0010] In view of such problems, the inventors of the present invention have conducted intensive research. As a result, the following insight has been obtained, that is, by controlling the region containing rare earth elements in the dielectric ceramic layer, the reliability of the multilayer ceramic capacitor can be significantly improved.

[0011] The present invention has been completed based on such an insight, with the object of providing a multilayer ceramic capacitor with excellent reliability.

[0012] Technical solutions for solving the problems

[0013] The present invention includes the following aspects. In addition, in this specification, the expression "~" includes the numerical values at both ends. That is, "X~Y" is synonymous with "X or more and Y or less".

[0014] According to one aspect of the present invention, there is provided a multilayer ceramic capacitor, comprising:

[0015] A body portion having a first main surface and a second main surface opposite to each other in the thickness direction, a first side surface and a second side surface opposite to each other in the width direction, and a first end surface and a second end surface opposite to each other in the length direction, and including a plurality of dielectric ceramic layers and a plurality of internal electrode layers laminated in the thickness direction; and

[0016] A pair of external electrodes respectively provided on the first end surface and the second end surface and electrically connected to the plurality of internal electrode layers,

[0017] wherein,

[0018] The dielectric ceramic layer contains grains composed of a perovskite-type composite oxide containing barium (Ba) and titanium (Ti) as the main component, and also contains rare earth elements (Re),

[0019] In a cross-section including the thickness direction, the dielectric ceramic layer contains a rare earth high-concentration region with a molar ratio of rare earth elements (Re) to titanium (Ti) (Re / Ti ratio) of 0.04 or more and 0.30 or less in an area ratio of 50% or more,

[0020] In the cross-section, the CV value of the thickness-direction line segment ratio of the rare earth high-concentration region is 25% or less.

[0021] Advantageous Effects of the Invention

[0022] According to the present invention, a multilayer ceramic capacitor with excellent reliability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. is a perspective view showing the external shape of the multilayer ceramic capacitor.

[0024] Figure 2 FIG. is a cross-sectional view schematically showing the internal structure of the multilayer ceramic capacitor.

[0025] Figure 3 FIG. is a cross-sectional view schematically showing the internal structure of the multilayer ceramic capacitor.

[0026] Figure 4 FIG. is a graph for explaining the thickness direction line segment ratio and the CV value of the rare earth high concentration region.

[0027] Figure 5 FIG. is a schematic cross-sectional view showing the microstructure of the multilayer ceramic capacitor. DETAILED DESCRIPTION OF THE INVENTION

[0028] A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described. In addition, the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

[0029] <<1. Multilayer Ceramic Capacitor>>

[0030] The multilayer ceramic capacitor of the present embodiment includes: a main body portion having a first main surface and a second main surface opposite to each other in the thickness direction, a first side surface and a second side surface opposite to each other in the width direction, and a first end surface and a second end surface opposite to each other in the length direction, and including a plurality of dielectric ceramic layers and a plurality of internal electrode layers laminated in the thickness direction; and a pair of external electrodes respectively provided on the first end surface and the second end surface and electrically connected to the plurality of internal electrode layers. Further, the dielectric ceramic layer contains grains composed of a perovskite-type composite oxide containing barium (Ba) and titanium (Ti) as a main component, and also contains a rare earth element (Re). In a cross section including the thickness direction, the dielectric ceramic layer contains a rare earth high concentration region having a molar ratio (Re / Ti ratio) of the rare earth element (Re) to titanium (Ti) of 0.04 or more and 0.30 or less in an area ratio of 50% or more. Further, in the cross section, the CV value of the thickness direction line segment ratio of the rare earth high concentration region is 25% or less.

[0031] Use Figures 1 to 3 to illustrate one way of the multilayer ceramic capacitor. Figure 1It is a perspective view showing the outer shape of a multilayer ceramic capacitor. Figure 2 and Figure 3 is a cross-sectional view showing the inside of a multilayer ceramic capacitor. The multilayer ceramic capacitor (100) includes: a main body portion (6) including a plurality of stacked dielectric ceramic layers (2) and a plurality of internal electrode layers (4); and a pair of external electrodes (8a, 8b) provided on two end faces (14a, 14b) of the main body portion (6). The multilayer ceramic capacitor (100) and the main body portion (6) have a substantially rectangular parallelepiped shape. The so-called substantially rectangular parallelepiped includes not only a rectangular parallelepiped but also a rectangular parallelepiped having rounded corners and / or edges. Further, the multilayer ceramic capacitor (100) and the main body portion (6) have a first main face (10a) and a second main face (10b) opposing in the thickness direction T, a first side face (12a) and a second side face (12b) opposing in the width direction W, and a first end face (14a) and a second end face (14b) opposing in the length direction L. Here, the so-called thickness direction T is the direction in which a plurality of dielectric ceramic layers (2) and a plurality of internal electrode layers (4) are stacked. The length direction L is a direction orthogonal to the thickness direction T and orthogonal to the end faces (14a, 14b) on which the external electrodes (8a, 8b) are provided. The width direction W is a direction orthogonal to the thickness direction T and the length direction L. A plane including the thickness direction T and the width direction W is defined as the WT plane, a plane including the width direction W and the length direction L is defined as the LW plane, and a plane including the length direction L and the thickness direction T is defined as the LT plane.

[0032] The external electrodes (8a, 8b) include a first external electrode (8a) provided on the first end face (14a) and a second external electrode (8b) provided on the second end face (14b). The first external electrode (8a) may be provided not only on the first end face (14a) but also around a part of the first main face (10a), the second main face (10b), the first side face (12a), and the second side face (12b). Further, the second external electrode (8b) may be provided not only on the second end face (14b) but also around a part of the first main face (10a), the second main face (10b), the first side face (12a), and the second side face (12b). However, the first external electrode (8a) and the second external electrode (8b) are not in contact and are electrically separated.

[0033] The internal electrode layer (4) includes a plurality of first internal electrode layers (4a) and a plurality of second internal electrode layers (4b). The plurality of first internal electrode layers (4a) extend to the first end face (14a) and are electrically connected to the first external electrode (8a) here. In addition, the plurality of second internal electrode layers (4b) extend to the second end face (14b) and are electrically connected to the second external electrode (8b) here. The first internal electrode layer (4a) and the second internal electrode layer (4b) facing each other with the dielectric ceramic layer (2) interposed therebetween are not electrically connected. Therefore, if a voltage is applied between the first internal electrode layer (4a) and the second internal electrode layer (4b) via the external electrodes (8a, 8b), charges can be accumulated. Due to the accumulated charges, capacitance is generated, thereby exhibiting the function as a capacitive element.

[0034] The size of the multilayer ceramic capacitor (100) is not particularly limited. However, preferably, the size in the length direction L is 0.4 mm or more and 5.7 mm or less, the size in the width direction W is 0.2 mm or more and 5.0 mm or less, and the size in the stacking direction T is 0.125 mm or more and 5.0 mm or less.

[0035] <Dielectric ceramic layer>

[0036] The dielectric ceramic layer contains ceramics. In addition, the dielectric ceramic layer contains grains composed of a perovskite-type composite oxide containing barium (Ba) and titanium (Ti) as a main component. That is, the main grains are composed of a perovskite-type composite oxide. The main grains contain barium titanate (BaTiO3)-type compounds. Therefore, it can also be said that the dielectric ceramic layer contains a sintered body of BaTiO3-type compounds. BaTiO3 is a perovskite-type oxide represented by the general formula ABO3. BaTiO3 is a ferroelectric that shows a tetragonal crystal structure at room temperature and shows a high dielectric constant. Therefore, by using BaTiO3-type compounds as the main component, the dielectric constant of the dielectric ceramic can be increased, and a large capacitance of the capacitor can be achieved. In addition, in this specification, the so-called main component is the component with the largest content ratio in the ceramic. The content ratio of the main component can be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0037] Regarding compounds of barium titanate (BaTiO3), as long as they are perovskite-type composite oxides mainly containing barium (Ba) and titanium (Ti), there is no particular limitation. That is, the compound can be BaTiO3, or it can also be a compound in which a part of Ba and / or Ti contained in BaTiO3 is replaced by other elements. Specifically, a part of barium (Ba) can also be replaced by other elements such as strontium (Sr) and calcium (Ca). In addition, a part of titanium (Ti) can also be replaced by other elements such as zirconium (Zr) and hafnium (Hf). Furthermore, the ratio of the A-site element (Ba, Sr, Ca, etc.) to the B-site element (Ti, Zr, Hf, etc.) in the BaTiO3-type compound is not strictly limited to 1:1. As long as the perovskite crystal structure is maintained, a deviation in the ratio of the A-site element to the B-site element is allowed.

[0038] The dielectric ceramic layer contains rare earth elements (Re) in addition to barium (Ba) and titanium (Ti). Rare earth elements (Re) are the general name of elements that form a group in the periodic table including 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. The dielectric ceramic layer can contain one kind of rare earth element, or it can also contain a combination of multiple rare earth elements. In addition, the rare earth element can be contained only in the BaTiO3-type compound as the main crystal grain, or it can also be contained not only in the main crystal grain but also in grain boundaries, triple points, etc. When contained in the main crystal grain, it can occupy the Ba site (A site) of the BaTiO3-type compound, or it can occupy the Ti site (B site), or it can also occupy both sites.

[0039] By adding rare earth elements (Re) to the dielectric ceramic layer, various properties such as the reliability of the multilayer ceramic capacitor and the temperature characteristics of the dielectric constant can be improved. That is, the BaTiO3-type compound as the main component sometimes contains many oxygen vacancies generated in the firing process. These oxygen vacancies tend to lower the insulation resistance in the case of accompanied by electron compensation, and in addition, they move under an electric field and tend to cause the insulation resistance to decrease over time. If rare earth elements are added to the dielectric ceramic layer, they tend to dissolve in the Ba site and Ti site of the BaTiO3-type compound. The dissolved rare earth elements act as donors and acceptors, preventing the movement of oxygen vacancies or suppressing the generation of conduction electrons. Therefore, the deterioration of the insulation resistance becomes smaller, and the high-temperature load life can be improved. In addition, the temperature dependence of the dielectric constant near the Curie temperature Tc of the BaTiO3-type compound is large. By dissolving rare earth elements, the temperature change of the dielectric constant can be made flatter in a wide range including the Curie temperature Tc.

[0040] The type of rare earth element (Re) contained in the dielectric ceramic layer is not particularly limited. However, it preferably contains 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), and particularly preferably contains dysprosium (Dy). Dy is an element located near the middle of the lanthanide group in the periodic table, and its ionic radius is also of medium size. Therefore, it can be dissolved in both the Ba site (A site) and the Ti site (B site) of the BaTiO3-based compound, which is effective in improving reliability. The dielectric ceramic layer may contain only Dy as the rare earth element, or may also contain other rare earth elements together with Dy.

[0041] By adding an appropriate amount of rare earth element (Re) to the dielectric ceramic layer, the effect of improving various properties can be more significantly exerted. In the dielectric ceramic layer, relative to 100 moles of titanium (Ti), the rare earth element (Re) is preferably contained in a proportion of 0.1 mole or more and 35.0 moles or less, more preferably in a proportion of 0.5 mole or more and 30.0 moles or less, and further preferably in a proportion of 3.5 moles or more and 25.0 moles or less. In addition, these mole numbers are the mole numbers of the raw materials.

[0042] The dielectric ceramic layer may also contain other additive components other than the rare earth element (Re). Examples of such components include manganese (Mn), magnesium (Mg), silicon (Si), aluminum (Al), vanadium (V), lithium (Li), boron (B), copper (Cu), and / or molybdenum (Mo). The existence form of the additive component is not limited. It may be contained in any of the main grains, grain boundaries, and triple points.

[0043] Preferably, the thickness of the dielectric ceramic layer is 0.5 μm or more and 7.0 μm or less. By making the thickness of the dielectric ceramic layer 0.5 μm or more, deterioration of the insulation characteristics can be prevented, which helps to improve reliability. On the other hand, by making the thickness 7.0 μm or less, the dielectric ceramic layer is thinned, and an increase in capacitance can be achieved. In addition, the number of layers of the dielectric ceramic layer is preferably 50 layers or more and 1000 layers or less.

[0044] In the multilayer ceramic capacitor of the present embodiment, in a cross section including the thickness direction, the dielectric ceramic layer includes a rare-earth high-concentration region at an area ratio of 50% or more. Here, the thickness direction is the stacking direction of the dielectric ceramic layer and the internal electrode layer. Therefore, a cross section including the thickness direction is a plane passing through the inside of the multilayer ceramic capacitor and a plane whose perpendicular line is orthogonal to the thickness direction, for example, the LT plane or the WT plane. Further, the rare-earth high-concentration region is a region where the molar ratio (Re / Ti ratio) of a rare-earth element (Re) to titanium (Ti) is 0.04 or more and 0.30 or less. That is, when the cross section of the dielectric ceramic layer is classified into a rare-earth ultra-high-concentration region where the Re / Ti ratio exceeds 0.30, a rare-earth high-concentration region where the Re / Ti ratio is 0.04 or more and 0.30 or less, and a rare-earth low-concentration region where the Re / Ti ratio is less than 0.04, the area ratio of the rare-earth high-concentration region with respect to the total area of the rare-earth ultra-high-concentration region, the rare-earth high-concentration region, and the rare-earth low-concentration region is 50% or more.

[0045] By increasing the area ratio of the rare-earth high-concentration region to 50% or more, it is possible to more significantly improve the reliability of the multilayer ceramic capacitor. Although the detailed reason is unclear, it is speculated as follows. A high rare-earth concentration means that the average distance between the positions where the rare-earth exists becomes shorter. The rare-earth element has an effect of hindering the movement of oxygen vacancies. By shortening the average distance between the rare-earth elements, the effect of suppressing the movement of oxygen vacancies increases, and as a result, the reliability is improved. From the viewpoint of improving the reliability, the higher the area ratio of the rare-earth high-concentration region, the more preferable. The area ratio can be 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, or can also be 100%. However, if the area ratio is too high, the dielectric constant sometimes decreases. From the viewpoint of increasing the dielectric constant, the area ratio can be 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, or 60% or less.

[0046] Preferably, in a cross-section including the thickness direction, the CV value of the Re / Ti ratio in the rare earth high-concentration region is 35% or less. The CV value serves as an index of deviation. The smaller the CV value of the Re / Ti ratio, the smaller the deviation of the Re / Ti ratio at each location in the rare earth high-concentration region. By limiting the CV value of the Re / Ti ratio to 35% or less, deviation in reliability can be suppressed. Although the detailed reason is unclear, it is speculated as follows. The so-called "even if the average Re / Ti ratio is the same, the CV value is large" sometimes means that there are regions where the Re / Ti ratio is extremely low compared to the average, and the total size of the low Re / Ti ratio regions distributed dispersedly is large. The low Re / Ti ratio regions may reduce reliability. Therefore, if the CV value of the Re / Ti ratio is small, it means that reliability is less likely to decrease, and reliability deviation can be reduced. From the perspective of suppressing reliability deviation, the smaller the CV value, the more preferable. The CV value can be 30% or less, 25% or less, 20% or less, 15% or less, or 10% or less. Regarding the CV value of the Re / Ti ratio, it can be obtained by the following method: dividing the rare earth high-concentration region into minute regions, measuring the Re / Ti ratio of each region by methods such as transmission electron microscopy (TEM)-energy dispersive X-ray spectroscopy (EDX), and using the average value and the standard deviation σ to calculate according to the following formula (1).

[0047] [Formula 1]

[0048] …(1)

[0049] In the multilayer ceramic capacitor of the present embodiment, in a cross-section including the thickness direction, the CV value of the line segment ratio in the thickness direction of the rare earth high-concentration region is 25% or less. Here, the line segment ratio in the thickness direction of the rare earth high-concentration region refers to the ratio of the part occupied by the rare earth high-concentration region on a line in the thickness direction inside the dielectric ceramic layer. Therefore, the CV value of the line segment ratio in the thickness direction serves as an index of the deviation of the distribution of the rare earth high-concentration region and other regions inside the dielectric ceramic layer.

[0050] This is illustrated by Figure 4 (a) and (b) thereof. Figure 4 (a) and (b) thereof schematically show the manner in which rare earth low-concentration regions are dispersed in the rare earth high-concentration region in the cross-section of the dielectric ceramic layer. In the case where the rare earth low-concentration regions (Y in the figure) are unevenly distributed ( Figure 4 (a) thereof), among multiple lines in the thickness direction, the ratio of the part occupied by the rare earth high-concentration region (X in the figure) on each line (the line segment ratio in the thickness direction of the rare earth high-concentration region) varies greatly. Therefore, the CV value of the line segment ratio in the thickness direction becomes large. In contrast, in the case where the rare earth low-concentration regions are relatively evenly distributed (Figure 4 In (b)), the value of the thickness direction line segment ratio is almost constant regardless of the line. Therefore, the CV value of the thickness direction line segment ratio becomes small.

[0051] By limiting the CV value of the thickness direction line segment ratio to less than 25%, it is possible to seek further improvement in reliability and to suppress the deviation in reliability. That is, the so-called CV value of the thickness direction line segment ratio is small, which means that the rare earth high concentration area and other areas are more evenly distributed in the ceramic layer. If their distribution becomes uniform, the local electric field concentration can be alleviated, which leads to further improvement in reliability. From the viewpoint of seeking improved reliability and reduced deviation, the CV value of the thickness direction line segment ratio in the rare earth high concentration area is more preferably less than 15%.

[0052] In addition, the CV value of the thickness direction line segment ratio of the rare earth high concentration region can be obtained as follows. First, in the cross section including the thickness direction, a line parallel to the thickness direction is hypothetically drawn. Then, the length L of the portion where the line crosses the dielectric ceramic layer is obtained. c .L c It can also be called the length of the line segment on the line divided by the dielectric ceramic layer. In addition, the total length L of the part of the line that crosses the rare earth high concentration area is calculated. high-Re .L high-Re It can also be called the total length of the line segments on the line dividing the rare earth high concentration area. Then, calculate L high-Re Relative to L c The ratio of (L high-Re / L c ), as the line segment ratio in the thickness direction of the rare earth high concentration region. For a plurality of separated lines (for example, 256 lines), the line segment ratio in the thickness direction is calculated, and the CV value is obtained using the average value and standard deviation σ according to the following formula (2).

[0053] [Mathematical formula 2]

[0054] … (2)

[0055] In addition, by investigating the high-temperature load life, it is possible to evaluate the reliability of the multilayer ceramic capacitor and its deviation. Regarding the high-temperature load life, a high-temperature load test can be performed on the capacitor, and evaluation can be made using the mean time to failure (MTTF) and B1 life obtained therefrom. Specifically, a high-temperature load test is performed on a plurality of capacitors, and the time when the insulation resistance sharply decreases is defined as the failure time. Weibull analysis is performed on the failure times of the respective capacitors to obtain the failure time and shape parameter m at which the cumulative failure rate becomes 63.2%, and the mean time to failure (MTTF) is determined based on them. In addition, the failure time at which the cumulative failure rate becomes 1% is defined as the B1 life. The longer the MTTF, the higher the reliability can be judged. In addition, the larger the B1 life / MTTF, the smaller the deviation of the reliability can be judged.

[0056] The distribution of the high-concentration rare earth region included in the dielectric ceramic layer is not particularly limited. It may also be in the following manner, that is, the dielectric ceramic layer has an island structure in the cross section, and the high-concentration rare earth region and the other region constitute the sea part and the island part, respectively. Specifically, it may also be in the following manner, that is, the other region, for example, a low-concentration rare earth region, is dispersedly arranged in the high-concentration rare earth region. Or, it may also be in the following manner, that is, the high-concentration rare earth region and the other region extend in a layered manner, and each layer of the dielectric ceramic layer has a laminated structure of a high-concentration rare earth region and the other region that become layered.

[0057] Preferably, in a cross-section including the thickness direction, the dielectric ceramic layer includes a rare-earth low-concentration region, and the rare-earth low-concentration region includes a plurality of sub-regions surrounded by a high-concentration region. Further, preferably, the average value of the equivalent circle diameters (average equivalent circle diameter) of the respective sub-regions in the cross-section is 130 nm or more. That is, preferably, the dielectric ceramic layer has an island structure in its cross-section, the rare-earth high-concentration region forms the sea portion, and the rare-earth low-concentration region forms the island portion, and the average equivalent circle diameter of the island portion is a given value or more. In this way, by dispersing and arranging the rare-earth low-concentration regions having a desired size in an island shape in the rare-earth high-concentration region, it is possible to increase the dielectric constant while ensuring the reliability of the multilayer ceramic capacitor. Although the detailed reason is unclear, it is speculated as follows. Regarding the Curie temperature Tc of the rare-earth high-concentration region, depending on the Re / Ti ratio, it sometimes becomes lower than room temperature, and at this time, the dielectric constant decreases. However, by mixing the rare-earth low-concentration regions having a Curie temperature Tc sufficiently higher than room temperature, a decrease in the dielectric constant can be avoided. In addition, since the dielectric constant has a size effect, by increasing the average equivalent circle diameter of the rare-earth low-concentration region to a given value or more, a higher dielectric constant can be obtained. From the viewpoint of increasing the dielectric constant, the larger the size of the dispersed sub-regions, the more preferable. The average equivalent circle diameter of the sub-regions may be 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, 200 nm or more, 210 nm or more, or 220 nm or more. On the other hand, in order to more effectively exhibit the effect of improving the reliability, it is preferable to suppress the size of the rare-earth low-concentration region to a certain extent. The average equivalent circle diameter of the sub-regions may be 300 nm or less, 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, or 160 nm or less. In addition, the average equivalent circle diameter (D50) is the diameter of a circle having the same area as the cumulative 50% area. Further, the cumulative 50% area is the area of the sub-regions when the cumulative area reaches 50% by cumulatively adding the areas of the sub-regions in ascending order with the total area of the respective sub-regions set to 100%. Regarding the average equivalent circle diameter, it can be calculated using the cumulative 50% area according to the following formula (3).

[0058] [Mathematical formula 3]

[0059] …(3)

[0060] Preferably, in a cross-section including the thickness direction, the average circularity (mean circularity) of each sub-region constituting the rare-earth low-concentration region is 0.70 or more. Circularity is an index indicating the complexity of the shape of a region, with a perfect circle being 1, and the more complex the shape, the smaller the circularity. By making the shape of the dispersedly arranged rare-earth low-concentration regions approximately circular, it is possible to suppress the voltage dependence of the high-temperature load life. Although the detailed reason is unclear, it is speculated as follows. By increasing the circularity of the sub-regions constituting the rare-earth low-concentration region, the probability of the presence of parts with extremely high curvature at the boundary with the rare-earth high-concentration region can be reduced. Since the insulation resistance varies according to the rare-earth concentration, it is considered that the change in the insulation resistance at the boundary between the rare-earth low-concentration region and the rare-earth high-concentration region becomes larger in particular. Therefore, the smoother this boundary is, that is, the higher the circularity of the sub-regions constituting the rare-earth low-concentration region, the more the electric field concentration can be suppressed, and as a result, the voltage dependence of the high-temperature load life becomes smaller. The mean circularity of the sub-regions can also be 0.75 or more, 0.80 or more, or 0.85 or more. In addition, the mean circularity can be obtained by using the area and perimeter of each sub-region obtained by TEM observation or the like, calculating the circularity according to the following formula (4), and calculating the average value thereof.

[0061] [Mathematical formula 4]

[0062] …(4)

[0063] <Internal electrode layer>

[0064] The internal electrode layer contains a conductive metal. As the conductive metal, well-known electrode materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and their alloys can be used. In addition, the internal electrode layer may also contain other components other than the conductive metal. As the other components, ceramic components that function as common materials can be cited. As the ceramic components, BaTiO3-based compounds contained in the dielectric ceramic layer can be cited.

[0065] Preferably, the thickness of the internal electrode layer is 0.3 μm or more and 0.7 μm or less. By making the thickness of the internal electrode layer 0.3 μm or more, defects such as electrode interruption can be suppressed. In addition, by making the thickness of the internal electrode layer 0.7 μm or less, a decrease in the proportion of the dielectric ceramic layer that exhibits an electrical function in the capacitor and a resulting decrease in capacitance can be suppressed.

[0066] <External electrode>

[0067] As the external electrode, a known structure can be adopted. For example, it can be set to a laminated structure including a base layer, a first plating layer, and a second plating layer starting from the end face side of the multilayer ceramic capacitor. The base layer contains metals such as nickel (Ni) and copper (Cu), for example. In addition, ceramic powder can be included as a common material in addition to the metal. The first plating layer is a nickel (Ni) plating layer, for example. The second plating layer is a tin (Sn) plating layer, for example. In addition, a conductive resin layer can 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 resin. The external electrode only needs to be an electrode that is electrically connected to the internal electrode layer and functions as an external input / output terminal, and its form is not limited.

[0068] <<2. Manufacturing Method of Multilayer Ceramic Capacitor>>

[0069] Regarding the multilayer ceramic capacitor of the present embodiment, as long as the above-mentioned requirements are met, its manufacturing method is not limited. An exemplary manufacturing method includes the following steps. It includes: a step of manufacturing a green sheet containing at least barium (Ba), titanium (Ti), and rare earth elements (Re) (green sheet manufacturing step); a step of coating a conductive paste on the surface of the green sheet to obtain a green sheet with an internal electrode pattern formed thereon (electrode pattern forming step); a step of laminating and pressing a plurality of green sheets to obtain a laminated block (laminating step); a step of cutting the obtained laminated block to obtain laminated chips (cutting step); a step of subjecting the obtained laminated chips to a debinding treatment and a firing treatment to obtain a body part (firing step); and a step of forming an external electrode on the obtained body part (external electrode forming step). Hereinafter, each step will be described in detail.

[0070] <Green Sheet Manufacturing Step>

[0071] In the green sheet manufacturing step, a green sheet containing at least barium (Ba), titanium (Ti), and rare earth elements (Re) is manufactured. The green sheet is a precursor of the dielectric ceramic layer of the capacitor and contains the main component raw material and additive raw material of the dielectric ceramic layer. The manufacturing of the green sheet can be carried out by a known method without particular limitation. As long as the additive raw material is mixed in the main component raw material to manufacture the dielectric raw material, a binder and a solvent are added to the obtained dielectric raw material and mixed to make it into a slurry, and the obtained slurry is used to form the green sheet.

[0072] As the main component raw material, a powder of a BaTiO3-based compound is used. Regarding the BaTiO3-based compound, any known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides, and / or chelate compounds can be used, and they can be synthesized by known ceramic synthesis methods such as solid-phase reaction method, hydrothermal synthesis method, alkoxide method, etc. In addition, the additive raw materials at least include rare earth element (Re) raw materials. As the Re raw material, any known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides, and / or chelate compounds of Re can be used. The additive raw materials may also include raw materials of other additive components such as Mn, Mg, Si, Al, V, Li, B, Cu, and / or Mo. Furthermore, in order to adjust the composition of the BaTiO3-based compound as the main component, Ba raw materials such as barium carbonate (BaCO3) and Ti raw materials such as titanium oxide (TiO2) can be added to the additive raw materials.

[0073] The mixing of raw materials can be carried out by known methods. For example, a method of wet mixing and pulverizing the weighed main component raw materials, additive raw materials, and water together with a pulverizing medium using a ball mill can be cited. In the case of wet mixing, the obtained mixture only needs to be dried. In addition, the dielectric raw materials obtained after drying can be pre-fired as needed. The slurry formation can also be carried out by known methods, and only by mixing an organic binder and an organic solvent into the dielectric raw materials. As the organic binder, any known binder such as a polyvinyl butyral-based binder can be used. In addition, as the organic solvent, any known solvent such as toluene and ethanol can be used. Additives such as plasticizers can also be added to the slurry as needed. Furthermore, the forming of the green sheet can be carried out by known methods such as the doctor blade method and the lip method.

[0074] <Electrode pattern forming process>

[0075] In the electrode pattern forming process, a conductive paste is coated on the surface of the green sheet to obtain a green sheet with an internal electrode pattern formed. The internal electrode pattern becomes an internal electrode layer after firing. As the conductive metal contained in the conductive paste, any conductive materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and alloys containing them can be used. In addition, a ceramic component that functions as a common material can also be added to the conductive paste. As the ceramic component, the main component raw material of the dielectric ceramic layer can be used. The coating of the conductive paste can be carried out by known methods such as screen printing and gravure printing.

[0076] <Lamination process>

[0077] In the lamination process, multiple green sheets are laminated and pressed to obtain a laminated block. As the green sheets, those with an internal electrode pattern formed thereon are used, but green sheets without an internal electrode pattern formed thereon can also be used in part. Lamination and pressing can be performed by known methods.

[0078] <Cutting process>

[0079] In the cutting process, the obtained laminated block is cut to obtain laminated chips. Cutting is performed such that chips of a given size can be obtained and at least a part of the internal electrode pattern is exposed on the end face of the laminated chip.

[0080] <Firing process>

[0081] In the firing process, the obtained laminated chips are subjected to a debinding treatment and a firing treatment to obtain a body part. The green sheet and the internal electrode pattern are co-fired by the firing treatment to become a dielectric ceramic layer and an internal electrode layer, respectively. The conditions for the debinding treatment are determined according to the type of the organic binder contained in the green sheet and the internal electrode pattern. In addition, the firing treatment is performed at a temperature at which the laminated chips are sufficiently densified. For example, it can be performed under the following conditions: maintaining at a temperature of 1100 °C or higher and 1200 °C or lower for 1 hour or longer and 10 hours or shorter. In addition, firing is performed in an atmosphere in which the BaTiO3-based compound as the main component is not reduced and oxidation of the conductive metal can be suppressed. For example, it can be performed in an N2-H2-H2O gas flow with an oxygen partial pressure of 1.9×10 -11 MPa or higher and 6.4×10 -9 MPa or lower. Furthermore, an annealing treatment can also be performed after firing.

[0082] <External electrode forming process>

[0083] In the external electrode forming process, an external electrode is formed on the obtained body part. The formation of the external electrode can be performed by known methods. For example, it can be formed by the following method: coating a conductive paste containing metals such as silver (Ag), copper (Cu), and / or nickel (Ni) on the end face of the body part where the internal electrode is led out and exposed, and then performing sintering. Or, it can also be formed by the following method: coating a conductive paste on the two end faces of the laminated chip before firing, and then performing a firing treatment. In addition, the formed electrode can be used as a base layer, and a plating film of nickel (Ni), tin (Sn), etc. can be formed thereon. Thus, a multilayer ceramic capacitor can be manufactured.

[0084] Examples

[0085] The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples.

[0086] (1) Fabrication of multilayer ceramic capacitors

[0087] [Examples 1 to 19]

[0088] Specimens of multilayer ceramic capacitors were fabricated in the following order.

[0089] First, BaTiO3 powder with a BET diameter of 190 nm and a tetragonality of 1.0099 was prepared as BT-A powder. Here, tetragonality is an index of the degree of tetragonality in the tetragonal crystal structure, and is represented by the ratio of the c-axis length to the a-axis length (c / a axis ratio) in the tetragonal crystal. Tetragonality can be determined by powder X-ray diffraction (XRD). In addition, the BET diameter is the average primary particle diameter obtained by assuming that the particles are spherical and converting based on the BET specific surface area of the BaTiO3 powder.

[0090] In addition, differently, BaTiO3 powder with a BET diameter of 100 nm and a tetragonality of 1.007 was prepared as BT-B powder, and it was wet-milled to obtain micro-milled BT-B powder. The BET specific surface area of the micro-milled BT-B powder was 50 m 2 / g.

[0091] Furthermore, Dy2O3 powder, BaCO3 powder, and TiO2 powder were wet-milled individually to obtain micro-milled Dy2O3 powder, micro-milled BaCO3 powder, and micro-milled TiO2 powder. The BET specific surface areas of the micro-milled Dy2O3 powder, micro-milled BaCO3 powder, and micro-milled TiO2 powder were in the range of 50 m 2 / g to 56 m 2 / g.

[0092] Next, the BT-A powder, micro-milled BT-B powder, micro-milled Dy2O3 powder, micro-milled BaCO3 powder, and micro-milled TiO2 powder were mixed using a wet mill to obtain the composition shown in Table 1 below, and then dried to obtain a mixed powder. In addition, in Table 1, the A / B ratio of the perovskite-type oxide (ABO3) is also shown. The A / B ratio is the molar ratio of the A-site element to the B-site element. Regarding Dy, it is treated as an element that enters both the A-site and the B-site in the formulation to obtain the A / B ratio shown in Table 1.

[0093] In the obtained mixed powder, the following heat treatment was carried out to obtain a pre-sintered powder, that is, it was heated to 1100 °C at a heating rate of 600 °C / hour in the atmosphere and then held for two hours.

[0094] To 100 moles of TiO2 in the pre-sintered powder, 1.0 mole of MgCO3 powder and 0.3 mole of MnCO3 powder were added, and SiO2 sol and Li2CO3 were added to the pre-sintered powder in the amounts shown in Table 1 below, followed by wet mixing and drying to obtain a dielectric powder.

[0095] A polyvinyl butyral-based binder and a plasticizer were added to the obtained dielectric powder, and then toluene and ethanol were added. The mixture was made into a slurry using a wet mill, and the slurry was formed to obtain a green sheet. The thickness of the obtained green sheet after sintering densification was 1.7 μm.

[0096] On the surface of the obtained green sheet, a conductive paste mainly composed of nickel was screen-printed to form a pattern of a conductive paste layer that became the internal electrode layer.

[0097] Then, 201 green sheets with a conductive paste layer formed on the surface were stacked such that the sides from which the conductive paste layer was led out were different from each other. Further, green sheets without a conductive paste layer were provided above and below, and then the whole was pressed to produce a stacked block.

[0098] The obtained stacked block was cut and separated into green stacked chips. The cutting and separation were performed such that the size of the manufactured multilayer ceramic capacitor became 3.2 mm × 1.6 mm.

[0099] The obtained green stacked chips were heat-treated at 280 °C in a N2 gas stream to burn off the binder. Next, firing was carried out for two hours in a N2-H2-H2O gas stream at 1150 °C under the condition that the oxygen partial pressure was 1.6×10 -9 MPa.

[0100] In the fired stacked chips, a conductive paste mainly composed of Cu was applied to the end faces from which the internal electrode layers were led out, and baking was carried out at 800 °C to form external electrodes. Further, a Ni-Sn plating layer was formed on the surface of the external electrodes.

[0101] In this way, a multilayer ceramic capacitor was manufactured. The obtained multilayer ceramic capacitor had an outer shape of length 3.2 mm × width 1.6 mm × thickness 1.6 mm. In addition, the number of dielectric ceramic layers sandwiched by the internal electrode layers was 200, and the thickness of each dielectric ceramic layer was 1.7 μm.

[0102] [Examples 20 to 23]

[0103] Rare earth oxides (Gd2O3, Y2O3, Ho2O3, and Er2O3) corresponding to the types of rare earth elements (Re) shown in Table 1 below were prepared. Then, until the BET specific surface area fell within the range of 50 m 2 / g to 60 m 2 / g, these rare earth oxides were individually wet-milled to obtain finely milled Re oxide powders. The raw material powders (BT-A powder, finely milled BT-B powder, finely milled Re oxide powder, finely milled BaCO3 powder, and finely milled TiO2 powder) were mixed to obtain the composition shown in Table 1 below, and dried to obtain a mixed powder. Regarding the rare earth element (Re), it was treated as an element that enters both the A-site and the B-site in the formulated composition, and the raw materials were formulated so as to obtain the A / B ratio shown in Table 1 below. Other than that, multilayer ceramic capacitors were produced in the same manner as in Examples 1 to 19.

[0104] [Examples 24 to 28]

[0105] Rare earth oxides (Dy2O3, La2O3, Nd2O3, Tb4O7, Yb2O3, Lu2O3, Eu2O3, Sm2O3, CeO2, Pr6O 11 、and Tm2O3) corresponding to the types of rare earth elements (Re) shown in Table 1 below were prepared. Then, until the BET specific surface area fell within the range of 50 m 2 / g to 60 m 2 / g, these rare earth oxides were individually wet-milled to obtain finely milled Re oxide powders. The raw material powders (BT-A powder, finely milled BT-B powder, finely milled Re oxide powder, finely milled BaCO3 powder, and finely milled TiO2 powder) were mixed to obtain the composition shown in Table 1 below, and dried to obtain a mixed powder. When formulating the raw materials, the addition amounts of rare earth elements other than Dy were all set to 0.1 mole fraction. In addition, regarding La, Nd, Eu, Sm, Ce, and Pr, they were treated as elements that enter the A-site in the formulated composition. Regarding Tb, Yb, Lu, and Tm, they were treated as elements that enter the B-site in the formulated composition. Regarding Dy, it was treated as an element that enters both the A-site and the B-site in the formulated composition. On the basis of considering these, the raw materials were formulated so as to obtain the A / B ratio shown in Table 1 below. Other than that, multilayer ceramic capacitors were produced in the same manner as in Examples 1 to 19.

[0106] (2) Evaluation

[0107] Regarding the multilayer ceramic capacitors obtained in Examples 1 to 28, various characteristics were evaluated as follows.

[0108] <TEM Observation / EDX Analysis>

[0109] The dielectric ceramic layer of the multilayer ceramic capacitor was observed using a field emission type transmission electron microscope (FE-TEM), and elemental analysis of the microscopic region was performed using an energy dispersive X-ray spectrometer (EDX) attached to the TEM. A thin film specimen was prepared by processing the dielectric ceramic layer using the FIB lift-out method. In addition, the observation and analysis were carried out under the following conditions.

[0110] - Equipment: JEOL Ltd., JEM-2200FS / Noran System 7

[0111] - Field of view: n = 2

[0112] - Magnification: 60,000 times

[0113] - Pixel size: 9.2 nm / 1 pixel

[0114] - Spot diameter: 1 nm φ

[0115] - Measurement: EDX cumulative count 100 times

[0116] In addition, during observation, the dielectric ceramic layer within the field of view was extracted, and the region where the Re / Ti ratio was 0.04 or more and 0.30 or less was defined as the rare earth high-concentration region, and its area ratio was calculated according to the following formula (5). Furthermore, the Re / Ti ratio of each pixel in the rare earth high-concentration region was measured, and the CV value was calculated according to the following formula (1) based on its average value and standard deviation σ.

[0117] [Mathematical formula 5]

[0118] … (5)

[0119] [Mathematical formula 6]

[0120] … (1)

[0121] In addition, the CV value of the line ratio in the thickness direction of the rare earth high-concentration region was obtained as follows. First, in a cross-section including the thickness direction, a line parallel to the thickness direction was hypothetically drawn. Next, the number of pixels of the dielectric ceramic layer on this line was obtained as the value corresponding to the length L of the part crossing the dielectric ceramic layer. In addition, the number of pixels of the rare earth high-concentration region on this line was obtained as the value corresponding to the total length L of the part crossing the rare earth high-concentration region. Then, as shown in the following formula (6), the ratio of L c corresponding value. In addition, the number of pixels of the rare earth high-concentration region on this line was obtained as the value corresponding to the total length L high-Re corresponding value. Then, as shown in the following formula (6), L was calculated high-Re with respect to L c ratio (Lhigh-Re / L c ), as the line segment ratio in the thickness direction of the rare earth high concentration region. The line segment ratio in the thickness direction was calculated for the 256 separated lines, and the CV value was calculated using the average value and standard deviation σ according to the following formula (2).

[0122] [Mathematical formula 7]

[0123] … (6)

[0124] [Mathematical formula 8]

[0125] … (2)

[0126] In addition, the area where the Re / Ti ratio is less than 0.04 is defined as a rare earth low concentration area, and the equivalent circle diameter and circularity of the sub-area constituting the rare earth low concentration area are calculated. Specifically, the boundary lines of the sub-areas constituting the rare earth low concentration area and the rare earth high concentration area are drawn with a stylus. Then, the obtained data is analyzed using image analysis software (Winroof, Mitani Shoji Co., Ltd.) to calculate the area and perimeter of each sub-area. Furthermore, the total area of ​​each sub-area is set to 100 (100%), and the areas of the sub-areas are accumulated in ascending order to calculate the area of ​​the sub-area when the cumulative amount is 50 (50%) (cumulative 50% area). Then, using this cumulative 50% area, the average equivalent circle diameter (D50) is calculated according to the following formula (3). In addition, the circularity of each sub-area is calculated according to the following formula (4), and its average value is calculated.

[0127] [Mathematical formula 9]

[0128] … (3)

[0129] [Formula 10]

[0130] … (4)

[0131] <Dielectric properties>

[0132] The obtained multilayer ceramic capacitor was measured for capacitance (C) using an automatic bridge tester at an AC voltage of 1 V and 1 kHz. The relative dielectric constant (ε) was then calculated using the area of ​​the opposing electrodes of the multilayer ceramic capacitor and the number and thickness of the dielectric ceramic layers. r ). 72 samples prepared under the same conditions were measured and the average value of the obtained values ​​was calculated.

[0133] <Reliability (MTTF, B1 life)>

[0134] The high - acceleration life test (HALT) was carried out on multilayer ceramic capacitors, and the mean time to failure (MTTF) was obtained. In the high - acceleration life test, a high - temperature load was applied to the samples under the conditions of a temperature of 175 °C and a test voltage of 50 V. Then, the time when the insulation resistance became 200 kΩ or less was defined as the failure time. The failure times of 72 samples fabricated under the same conditions were measured.

[0135] Next, the obtained data was plotted on Weibull probability paper to obtain the Weibull distribution. In the obtained Weibull distribution, a linear regression was performed on the relationship between the failure time and the cumulative failure rate, and the slope was obtained as the shape parameter m. In addition, the failure time when the cumulative failure rate reached 63.2% was read, and the mean time to failure (MTTF) at a test voltage of 50 V was defined using this failure time and the shape parameter m equivalent to the slope of the regression line. Then, the samples with an MTTF of 50 hours or more were judged as qualified products. In addition, the failure time when the cumulative failure rate reached 1% was defined as the B1 life. Then, B1 life / MTTF was calculated and expressed in %.

[0136] Furthermore, except for changing the test voltage to 60 V, the high - acceleration life test was carried out under the same conditions, the mean time to failure (MTTF) at a test voltage of 60 V was obtained, and the decrease in MTTF was calculated according to the following formula (7).

[0137] [Mathematical formula 11]

[0138] … (7)

[0139] (3)Evaluation results

[0140] The evaluation results obtained for Examples 1 to 28 are summarized in Table 1 below. In addition, regarding the MTTF shown in Table 1, except for the decrease in MTTF, the values were measured under the condition of a test voltage of 50 V.

[0141] In the sample examples (Examples 2 to 17, Examples 19 to 28) where the area ratio in the rare - earth high - concentration region was 50% or more, the MTTF was 71 hours or more. In particular, in the samples (Examples 9, 12, 14, and 16) where the rare - earth element (Re) was Dy and the area ratio was 60% or more, the MTTF was as long as 122 hours or more. On the other hand, in the comparative - example samples (Examples 1, 18) where the area ratio was less than 50%, the MTTF was as short as 39 hours or less. From these results, it can be seen that by increasing the area ratio of the rare - earth high - concentration region to 50% or more, a multilayer ceramic capacitor with high reliability can be obtained.

[0142] In all of the example samples (Examples 2 to 17, Examples 19 to 28), the CV value of the line segment ratio in the thickness direction of the rare earth high-concentration region is 25% or less. In particular, in the samples where the CV value of the line segment ratio in the thickness direction is 15% or less (Examples 2 to 17 and Examples 20 to 28), the MTTF is 79 hours or more, and the B1 lifetime / MTTF is 23% or more. From these results, it can be seen that by reducing the CV value of the line segment ratio in the thickness direction of the rare earth high-concentration region, the reliability and its deviation can be suppressed.

[0143] In the example samples where the CV value of the Re / Ti ratio is 35% or less (Examples 2 to 14, Example 16, Example 17, and Examples 19 to 28), the B1 lifetime / MTTF is 19% or more, and the deviation of the failure time is small. In particular, in the example samples where the CV value of the Re / Ti ratio is 15% or less (Examples 11, 14, and 17), the B1 lifetime / MTTF is 47% or more, and the deviation of the failure time is very small.

[0144] In the example samples where the equivalent circle diameter of the rare earth low-concentration region is 130 nm or more (Examples 2 to 11, Examples 13 to 17, and Examples 19 to 28), the relative dielectric constant ε r is 2600 or more. Furthermore, in the example samples where the circularity of the rare earth low-concentration region is 0.70 or more (Examples 2 to 12, Examples 14 to 17, and Examples 19 to 28), the decrease in MTTF is 58% or less. From these results, it can be seen that by converging the CV value of the Re / Ti ratio, the equivalent circle diameter, and / or the circularity of the rare earth low-concentration region within a given range, the deviation of reliability and the voltage dependence can be suppressed, and an increase in the dielectric constant can be achieved.

[0145] In Figure 5 (a) and (b) schematically show the microstructure and element distribution of the cross-section of the multilayer ceramic capacitor obtained in the examples. Figure 5 (a) is a diagram showing the cross-sectional microstructure. In the figure, points A and C show the internal electrode layers, and in addition, point B shows the dielectric ceramic layer. Furthermore, Figure 5 (b) is an element distribution diagram showing the distribution of Dy. In Figure 5 (b), the regions with a high Dy concentration in the dielectric ceramic layer are shown brightly, and the regions with a low concentration are shown darkly. As shown in Figure 5 (a), the dielectric ceramic layer contains many grains. In addition, as shown in Figure 5 (b), the Dy distribution is uneven, and the Dy low-concentration regions are distributed in an island shape in the Dy high-concentration regions. Furthermore, there are grains containing a plurality of independent rare earth low-concentration regions.

[0146] [Table 1]

[0147]

[0148] [Table 2]

[0149]

[0150] Explanation of Reference Numerals

[0151] 2: Dielectric ceramic layer;

[0152] 4: Internal electrode layer;

[0153] 6: Body portion;

[0154] 8a: First external electrode;

[0155] 8b: Second external electrode;

[0156] 10a: First main surface;

[0157] 10b: Second main surface;

[0158] 12a: First side surface;

[0159] 12b: Second side surface;

[0160] 14a: First end surface;

[0161] 14b: Second end surface;

[0162] 100: Multilayer ceramic capacitor.

Claims

1. A multilayer ceramic capacitor, comprising: A body portion having a first main surface and a second main surface opposite to each other in the thickness direction, a first side surface and a second side surface opposite to each other in the width direction, and a first end surface and a second end surface opposite to each other in the length direction, and including a plurality of dielectric ceramic layers and a plurality of internal electrode layers laminated in the thickness direction; and A pair of external electrodes respectively provided on the first end surface and the second end surface and electrically connected to the plurality of internal electrode layers, wherein, The dielectric ceramic layer contains grains composed of a perovskite-type composite oxide containing barium Ba and titanium Ti as a main component, and also contains a rare earth element Re, In a cross section including the thickness direction, the dielectric ceramic layer contains a rare earth high-concentration region with a Re / Ti ratio of 0.04 or more and 0.30 or less in an area ratio of 50% or more. The Re / Ti ratio is the molar ratio of the rare earth element Re to titanium Ti, In the cross section, the CV value of the thickness direction line segment ratio of the rare earth high-concentration region is 25% or less.

2. The multilayer ceramic capacitor according to claim 1, wherein, In the cross section, the CV value of the thickness direction line segment ratio of the rare earth high-concentration region is 15% or less.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein, In the cross section, the dielectric ceramic layer contains the rare earth high-concentration region in an area ratio of 60% or more.

4. The multilayer ceramic capacitor according to any one of claims 1 to 3, wherein, In the cross section, the CV value of the Re / Ti ratio in the rare earth high-concentration region is 35% or less.

5. The multilayer ceramic capacitor according to any one of claims 1 to 4, wherein, In the cross section, the CV value of the Re / Ti ratio in the rare earth high-concentration region is 15% or less.

6. The multilayer ceramic capacitor according to any one of claims 1 to 5, wherein, In the cross section, the dielectric ceramic layer contains a rare earth low-concentration region with a Re / Ti ratio less than 0.

04. The Re / Ti ratio is the ratio of the rare earth element Re to titanium Ti, The rare earth low-concentration region contains a plurality of sub-regions surrounded by the rare earth high-concentration region, The average value of the equivalent circle diameters of the sub-regions in the cross section, that is, the average equivalent circle diameter, is 130 nm or more.

7. The multilayer ceramic capacitor according to claim 6, wherein, The average value of the circularity of the sub-regions in the cross section, that is, the average circularity, is 0.70 or more.

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