Multilayer ceramic capacitor

Abstract

To provide a multilayer ceramic capacitor in which the occurrence of extra carriers is suppressed and a dielectric layer is formed of a dielectric having high insulating resistance even under a high electric field intensity.SOLUTION: A multilayer ceramic capacitor 1 includes a multilayer body 2 in which dielectric layers 4 and internal electrode layers 5 are alternately stacked, and a pair of external electrodes 3a, 3b with different polarities provided at opposite end parts of the multilayer body 2. The dielectric layer 4 mainly contains a barium titanate solid solution, and contains a first additive component and a second additive component. When a decision coefficient R2 of the concentration of the first additive component and the concentration of the second additive component is expressed by R2=S2xy / Sx*Sy, 0.5≤R2≤1.0 is satisfied, where Sxy represents a covariance of the concentration of the first additive component and the concentration of the second additive component; Sx represents the standard deviation of the concentration of the first additive component; and Sy represents the standard deviation of the concentration of the second additive component.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventional multilayer ceramic capacitors are described, for example, in Patent Document 1. This conventional multilayer ceramic capacitor includes a plurality of dielectric ceramic layers, internal electrodes formed between the dielectric ceramic layers, and external electrodes electrically connected to the internal electrodes.

[0003] The dielectric ceramic layer is composed of a barium titanate-based solid solution and an additive component. When represented by the general formula ABO3+aR+bM, for the main component within the range of 0.950 ≦ A / B (molar ratio) ≦ 1.050, 0.12 < a ≦ 1.5, and 0.04 ≦ b ≦ 1.5, a sintering aid is contained as a sub-component.

[0004] In the above general formula, ABO3 represents a barium titanate-based solid solution represented by the general formula showing a perovskite structure, R is an oxide of at least one metal element selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, M is an oxide of at least one metal element selected from Mn, Ni, Mg, Fe, Al, Cr, and Zn, and a and b are molar ratios when the respective oxides are converted into chemical formulas containing one metal element. Such a dielectric ceramic layer has a firing temperature of 1300°C or lower, a dielectric constant of 200 or more, an electric field strength of 10 kV / mm, and a high insulation resistance of 7000 Ω·F or more at room temperature.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the conventional technology of Patent Document 1, dysprosium (Dy) and gadolinium (Gd) are only used as additive components, so that excess carriers (electrons or holes) are generated in the areas where dysprosium (Dy) or gadolinium (Gd) is in excess, and there is a risk of the insulation resistance value decreasing. In addition, since carriers are the source of current flow, the electrical conductivity increases and the insulation resistance value decreases as the number of carriers increases. Therefore, there has been a demand for a multilayer ceramic capacitor in which the decrease in insulation resistance value is suppressed. [Means for solving the problem]

[0007] The multilayer ceramic capacitor according to the present disclosure includes a laminate in which dielectric layers and internal electrodes are alternately laminated, and a pair of external electrodes having different polarities provided at both ends of the laminate, the dielectric layer containing a barium titanate-based solid solution as a main component and containing a first additional component and a second additional component, and a coefficient of determination R 2 where Sxy is the covariance of the concentration of the first additive component and the concentration of the second additive component, Sx is the standard deviation of the concentration of the first additive component, and Sy is the standard deviation of the concentration of the second additive component, 2 =S 2 When expressed as xy / Sx Sy, 0.5≦R 2 The configuration satisfies ≦1.0. Effect of the Invention

[0008] In the multilayer ceramic capacitor according to the present disclosure, the concentration of the first additive component and the concentration of the second additive component are determined by a coefficient of determination R 2 However, 0.5≦R 2 Since the composition satisfies the condition of ≦1.0, it is possible to provide a multilayer ceramic capacitor having a dielectric layer which suppresses the generation of excess carriers and has high insulation resistance even under a high electric field strength. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment of the present invention; [Diagram 2] 2 is a perspective view showing a laminate of the multilayer ceramic capacitor of FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view taken along the line III-III in FIG. [Figure 4] FIG. 2 is a map of dysprosium (Dy) by energy dispersive X-ray spectroscopy in a dielectric layer of the multilayer ceramic capacitor according to the present embodiment. [Diagram 5] FIG. 2 is a map of gadolinium (Gd) by energy dispersive X-ray spectroscopy in a dielectric layer of the multilayer ceramic capacitor according to the present embodiment. [Figure 6] 1 is a graph showing the concentration distribution of dysprosium (Dy) and gadolinium (Gd) obtained by TEM-EDS measurement. [Figure 7] 1 is a graph showing the correlation between the concentration of dysprosium (Dy) and the concentration of gadolinium (Gd). [Figure 8] FIG. 2 is a map showing the results of semi-quantitative analysis by TEM-EDS of the dielectric layers of the multilayer ceramic capacitor of the present embodiment. [Figure 9] 9 is a graph showing the concentration distribution in the scanning region S of the map diagram of FIG. 8. [Figure 10] 1 is a graph showing calculation results by simulation of the solid solution state of dysprosium (Dy) and gadolinium (Gd). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the multilayer ceramic capacitor of the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones. In the multilayer ceramic capacitor according to the embodiment, any direction may be considered as the upper or lower direction, but in this specification, for convenience, a Cartesian coordinate system xyz is defined in some drawings. In the following description, the positive side in the z-axis direction is considered as the upper side, and terms such as the upper surface and the lower surface may be used. The x-axis direction is also referred to as the first direction or the length direction. The y-axis direction is also referred to as the second direction or the width direction. The z-axis direction is also referred to as the third direction, the height direction, or the stacking direction.

[0011] In this embodiment, the perovskite oxide represented by the basic chemical composition ABO3 can be combined with A and B that satisfy the conditions of ionic radius and electrical neutrality to replace part of the A site and B site with other metal ions while maintaining this structure, thereby introducing oxygen defects. In the following explanation, holes in a p-type semiconductor move to an n-type semiconductor with a low hole density by a diffusion phenomenon, and electrons in an n-type semiconductor move to a p-type semiconductor with a low electron density by a diffusion phenomenon. The amount of current is defined as the amount of carriers that flow when a voltage is applied to an object.

[0012] Fig. 1 is a perspective view showing the appearance of a multilayer ceramic capacitor according to one embodiment of the present invention, and Fig. 2 is a perspective view showing a laminate of the multilayer ceramic capacitor of Fig. 1. Fig. 3 is a cross-sectional view taken along the line III-III in Fig. 1. In Fig. 2, for ease of illustration, the portions of the internal electrode layers exposed on the surface of the laminate are shown with hatching.

[0013] 1, the multilayer ceramic capacitor 1 of this embodiment includes a laminate 2, a first external electrode 3a, and a second external electrode 3b. Hereinafter, the first external electrode 3a and the second external electrode 3b may be collectively referred to as external electrodes 3a, 3b.

[0014] As shown in FIG. 2, the laminate 2 is substantially rectangular. The laminate 2 has a first surface 7a and a second surface 7b facing each other, a first end surface 8a and a second end surface 8b facing each other, and a first side surface 9a and a second side surface 9b facing each other. The first end surface 8a and the second end surface 8b may be perpendicular to the first direction x. The first side surface 9a and the second side surface 9b may be perpendicular to the second direction y. The first surface 7a and the second surface 7b may be perpendicular to the third direction z. Hereinafter, the first surface 7a and the second surface 7b may be collectively referred to as the main surfaces 7a and 7b, the first end surface 8a and the second end surface 8b may be collectively referred to as the end surfaces 8a and 8b, and the first side surface 9a and the second side surface 9b may be collectively referred to as the side surfaces 9a and 9b.

[0015] 3, the laminate 2 is configured by alternately stacking a plurality of dielectric layers 4 and a plurality of internal electrode layers 5. The plurality of dielectric layers 4 and the plurality of internal electrode layers 5 are stacked in the third direction z.

[0016] The dielectric layer 4 is made of a dielectric material. The dielectric layer 4 may be made of a ceramic material mainly composed of barium titanate (BaTiO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), barium zirconate (BaZrO3), or the like. In the following, unless otherwise specified, the dielectric layer 4 is made of a ceramic material mainly composed of barium titanate (BaTiO3). In this specification, the term "main component" refers to the component having the highest content in the material or member of interest. The content may be expressed, for example, in mol% or mass%.

[0017] The dielectric layer 4 may contain metal elements such as magnesium (Mg), manganese (Mn), vanadium (V), and rare earth elements such as yttrium (Y), dysprosium (Dy), holmium (Ho), terbium (Tb), ytterbium (Yb), etc. In this case, it is possible to improve the high temperature load life and temperature characteristics of the capacitance of the multilayer ceramic capacitor 1.

[0018] The thinner the dielectric layers 4, the greater the capacitance of the multilayer ceramic capacitor 1. The thickness of each of the dielectric layers 4 may be, for example, not less than about 0.1 μm and not more than about 3 μm.

[0019] The internal electrode layer 5 is exposed at the first end surface 8a or the second end surface 8b depending on the polarity. The end of the internal electrode layer 5 exposed at the first end surface 8a is covered by one (first external electrode 3a) of the pair of external electrodes 3a, 3b and connected to the first external electrode 3a. The end of the internal electrode layer 5 exposed at the second end surface 8b is covered by the other (second external electrode 3b) of the pair of external electrodes 3a, 3b and connected to the second external electrode 3b. Such an internal electrode layer 5 is made of a conductive material. The internal electrode layer 5 may be made of a metal material mainly composed of metal such as nickel (Ni), copper (Cu), tin (Sn), platinum (Pt), palladium (Pd), silver (Ag), gold (Au), etc., or an alloy thereof. The internal electrode layer 5 may have a thickness of, for example, 1.5 μm or less. In this case, internal defects caused by internal stress during firing of the laminate 2 or during application of voltage can be suppressed, and the reliability of the multilayer ceramic capacitor 1 can be improved.

[0020] As long as the characteristics of the multilayer ceramic capacitor can be ensured, the thinner the internal electrode layers 5, the more the occurrence of internal defects caused by internal stress during firing of the laminate 2 or during voltage application can be suppressed, and the more the reliability of the multilayer ceramic capacitor 1 can be improved. The thickness of the internal electrode layers 5 may be, for example, about 1.5 μm or less.

[0021] The first external electrode 3a is located at least on the first end face 8a. The first external electrode 3a may be located from the first end face 8a to at least one of the first face 7a, the second face 7b, the first side face 9a, and the second side face 9b. The second external electrode 3b may be located from the second end face 8b to the first face 7a, the second face 7b, the first side face 9a, and the second side face 9b, as shown in FIG. 1.

[0022] The external electrodes 3a, 3b are composed of a single layer or multiple layers of conductive layers. As shown in FIG. 3, the external electrodes 3a, 3b may be composed of a first layer 31 and a second layer 32. The first layer 31 is also called an underlayer. The underlayer 31 is in contact with the surface of the laminate 2 and is connected to the end exposed at the end faces 8a, 8b of the internal electrode layer 5. The second layer 32 is also called an outer layer. The outer layer 32 covers the surface of the underlayer 31 opposite to the laminate 2 side. By forming the external electrodes 3a, 3b from multiple conductive layers, it is possible to increase the adhesion between the external electrodes 3a, 3b and the laminate 2 while increasing the wettability of a conductive bonding material such as solder to the external electrodes 3a, 3b. As a result, it is possible to improve the reliability of the multilayer ceramic capacitor 1 and the mounting structure including the multilayer ceramic capacitor 1.

[0023] The underlayer 31 may be composed of a metal material. The underlayer 31 may be composed of a metal such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), gold (Au), or an alloy containing these metals. The underlayer 31 may be formed by using a thin film forming technique such as a plating method, a sputtering method, or a vapor deposition method, or may be formed by using a thick film forming technique such as a dipping method, a screen printing method, or a gravure printing method.

[0024] The outer layer 32 may be configured to include a metal material. The outer layer 32 may be configured to include, for example, a metal such as nickel (Ni), copper (Cu), gold (Au), or tin (Sn), or an alloy including at least two of these metals. The outer layer 32 may be formed using a thin film formation technique such as an electroless plating method or an electrolytic plating method. The outer layer 32 may be a single-layer plating layer or a multi-layer plating layer.

[0025] In the multilayer ceramic capacitor 1 of this embodiment, a case where dysprosium (Dy) is used as the first additive component and gadolinium (Gd) is used as the second additive component will be described. The above-mentioned dielectric layer 4 contains a titanate-based solid solution as a main component and contains the first additive component and the second additive component. The concentrations of the first additive component and the second additive component are determined by the coefficient of determination R 2 is 0.5≦R 2It is constructed to satisfy the following: Coefficient of determination R 2 is expressed by the following Equation 1, where Sxy is the covariance of the concentration of the first additive component and the concentration of the second additive component, Sx is the standard deviation of the concentration of the first additive component, and Sy is the standard deviation of the concentration of the second additive component.

[0026] R 2 =S 2 xy / Sx Sy …(1)

[0027] The covariance Sxy is expressed as the total number of measured concentration data, n, the concentration of each of the first added components, xi, and the average value of each concentration of the first added component. JPEG2025071722000002.jpg10139, the concentration of each of the second additive components is yi, and the average concentration of each of the second additive components is When JPEG2025071722000003.jpg10139 is used, it can be calculated by the following formula 2. When calculating the concentration of the first added component and the second added component in the crystal grain, an electron beam is applied to the center of the crystal grain, and the amount of the main element contained in the crystal grain is calculated from the obtained X-ray output as 100 atomic %, and the proportion of the first added component and the second added component is calculated from this.

[0028] JPEG2025071722000004.jpg13131

[0029] The standard deviation Sx of each concentration of the first additive component is calculated by the following formula 3.

[0030] JPEG2025071722000005.jpg16131

[0031] The standard deviation Sy of each concentration of the second additive component is calculated by the following formula 4.

[0032] JPEG2025071722000006.jpg16131

[0033] The first additive component is an oxide of one metal element selected from dysprosium (Dy), magnesium (Mg), manganese (Mn), and vanadium (V). The second additive component is an oxide of one metal element selected from gadolinium (Gd), yttrium (Y), ytterbium (Yb), holmium (Ho), and terbium (Tb).

[0034] FIG. 4 is a diagram showing a distribution image of dysprosium (Dy) by energy dispersive X-ray spectroscopy in the dielectric layer of the multilayer ceramic capacitor of this embodiment, and FIG. 5 is a diagram showing a distribution image of gadolinium (Gd) by energy dispersive X-ray spectroscopy in the dielectric layer of the multilayer ceramic capacitor of this embodiment. When an electron beam is irradiated to an atom in the ground state, there is a certain probability that an inner shell electron is excited outside the atom, and a vacancy occurs in the inner shell. Since the state with a vacancy in the inner shell is energetically unstable, the outer shell electron transitions to the inner shell. At that time, characteristic X-rays corresponding to the energy difference between the state before the transition and the state after the transition are emitted. Since the characteristic X-rays have specific energies depending on the element, elemental analysis can be performed by measuring this.

[0035] In order to confirm the element distribution state of the dielectric ceramic containing the metallic elements dysprosium (Dy) and gadolinium (Gd) of the first additive component in the aforementioned barium titanate (BaTiO3), the elements were identified by performing mapping processing using Energy Dispersive X-ray Spectroscopy (EDS) with a Transmission Electron Microscope (TEM). Line L1 in Fig. 4 and line L2 in Fig. 5 indicate the scanning position where the electron beam was irradiated on a sample made of the same material as the dielectric layer 4. The characteristic X-rays generated by irradiating the sample with the electron beam along lines L1 and L2 are detected, and the elements can be identified from the element-specific spectrum obtained by dispersing the X-rays by energy, and information on the structure can be obtained from the intensity. As shown by reference A in Figure 4 and reference B in Figure 5, it was confirmed that dysprosium (Dy) and gadolinium (Gd) are distributed in an O-shape, with dysprosium (Dy) dissolved in the Ti site and gadolinium (Gd) dissolved in the Ba site, and they are present at the same position. The presence of dysprosium (Dy) and gadolinium (Gd) at the same position suppresses the generation of excess carriers.

[0036] FIG. 6 is a graph showing the concentration distribution of dysprosium (Dy) and gadolinium (Gd) obtained by TEM-EDS measurement, in which the horizontal axis is the detection width ΔL in FIG. 4 and the vertical axis is the concentration in atomic percentage (atm%). FIG. 6 plots the results of semi-quantitative measurement of the ranges shown in FIG. 4 and FIG. 5 in the vertical direction from the top, using TEM-EDS measurement. As is clear from each of lines L21 and L22 in FIG. 6, they have concentration peaks at almost the same position and have similar waveforms. Therefore, it can be seen that dysprosium (Dy) shown by line L21 and gadolinium (Gd) shown by line L22 are present in the same amount at the same position.

[0037] FIG. 7 is a graph showing the correlation between the concentration of dysprosium (Dy) and the concentration of gadolinium (Gd). In FIG. 7, the horizontal axis shows the concentration of dysprosium (Dy) in atomic percentage (atm%), and the vertical axis shows the concentration of gadolinium (Gd) in atomic percentage (atm%). The Gd concentration values ​​in FIG. 7 were obtained by measuring at five points in the image at random positions without overlapping, changing the position of the region m in FIG. 8. In addition, the semi-quantitative analysis results are values ​​smoothed by moving average (10 points) because there are scattered values. The line L11 in FIG. 7 is a straight line showing the geometric mean when the concentration of dysprosium (Dy) and the concentration of gadolinium (Gd) are calculated at 10 points randomly and each concentration is used as a variable. In this example, L13=0.5135+0.2001. From this concentration distribution, it can be seen that dysprosium (Dy) and gadolinium (Gd) are present in the same amount at the same position.

[0038] In an area of ​​0.1 μm×1 μm in the dielectric layer 4, the ratio (maximum / minimum) of the maximum concentration of dysprosium (Dy) is 3.0 or more. If the ratio of the maximum concentration of dysprosium (Dy) to the minimum concentration is less than 3.0, a core-shell structure cannot be formed. Here, the core-shell structure refers to a two-phase structure consisting of a core portion with a high dielectric constant and a shell portion with a relatively low dielectric constant surrounding the core portion. In the case of dysprosium (Dy), the ratio of the concentration in the center portion to the concentration in the outer periphery is 2 or more.

[0039] A regression equation was derived from all the data obtained from the TEM-EDS analysis, where the concentration of gadolinium (Gd) is on the vertical axis (y) and the concentration of dysprosium (Dy) is on the horizontal axis (x). The coefficient of determination, R 2 =0.7791. The coefficient of determination R 2 is a value between 0 and 1, and the closer it is to 1, the better the regression equation fits the actual data.

[0040] FIG. 8 is a map diagram of the semi-quantitative analysis of the dielectric layer of the multilayer ceramic capacitor of this embodiment by TEM-EDS. The central part of the sample of the multilayer ceramic capacitor 1 was measured by the TEM-EDS method at a magnification of 30000 / □1 μm, and a semi-quantitative analysis was performed. Five points were measured randomly without overlapping on the output image in an area of ​​0.1 μm×1 μm in the central dielectric layer 4, surrounded by a virtual line m, and the semi-quantitative analysis results were smoothed using a moving average of 10 points. FIG. 9 shows the data after smoothing, with dysprosium (Dy) on the horizontal axis and gadolinium (Gd) on the vertical axis, and shows the result of calculating the determination constant of linear approximation.

[0041] When the free energy of the atoms that make up the crystal is low in the external environment, oxygen atoms leak out and create oxygen lattice vacancies. The oxygen lattice vacancies migrate to the negative side of the dielectric layer during a voltage load test, which causes space charge polarization. The formation of space charge polarization generates a strong internal electric field at the crystal grain boundaries. As a result, the effective potential barrier is lowered, increasing the leakage current and lowering the insulation resistance. The lowered insulation resistance can lead to dielectric breakdown.

[0042] The large maximum-minimum difference in dysprosium (Dy) concentration means that the core-shell structure is clearly formed, and the dysprosium (Dy) concentration has a covering region on the outer periphery of the particle compared to the main raw material particle BT (barium titanate). The clear core-shell structure also makes the grain boundaries between particles clear, so oxygen vacancies are captured by the grain boundaries. The grain boundaries capture atomic defects such as impurities and vacancies. The capture of oxygen lattice vacancies at the grain boundaries prevents the formation of space charge polarization, and the generation of internal electric fields at the crystal grain boundaries can be suppressed. As a result, the effective potential barrier is suppressed from decreasing, so leakage current is suppressed, insulation breakdown can be reduced, and a longer life can be expected. The shell reduces the probability that the main raw material particles BT (barium titanate) of the core come into contact with each other, making it difficult for grains to grow due to contact between BT. By making it difficult for grains to grow, the area of ​​the grain boundaries can be maintained.

[0043] Since the ratio of the maximum and minimum values ​​of the concentration of dysprosium (Dy) is large, a core-shell structure is clearly formed, and oxygen vacancies are captured at the grain boundaries as acceptors. In an external environment, when the free energy of the atoms constituting the crystal is low, oxygen atoms leak out to the outside, generating oxygen vacancies. The oxygen vacancies move to the negative electrode side in the dielectric layer by a voltage load test, which causes space charge polarization. The formation of space charge polarization generates a strong internal electric field at the crystal grain boundaries. As a result, the effective potential barrier is lowered, which increases the leakage current and reduces the insulation resistance, and the insulation resistance is reduced, which causes insulation breakdown. In contrast, the dielectric layer of this embodiment can capture oxygen vacancies, thereby suppressing the reduction in insulation resistance.

[0044] In order to confirm the effects of the multilayer ceramic capacitor of the present disclosure, the present inventors prepared Samples 1 to 10 shown in the following Tables 1 and 2. Samples 1 to 10 are laminates prepared by adding 0.5 to 1.0 (mol%) of dysprosium (Dy) as a first additive component and 0.2 to 0.5 (mol%) of gadolinium (Gd) as a second additive component to barium titanate (BaTiO3) as a main raw material, and firing the laminate at a firing temperature rise rate of 3000 to 10000 (°C / hr).

[0045] [Table 1]

[0046] In addition, as shown in Table 2 below, the insulation resistance values ​​(MΩ) and the state of flaking of Samples 1 to 10 were also confirmed. Regarding flaking, a focused ion beam (FIB) was irradiated onto Samples 1 to 10 to confirm the change in properties. In Table 2, the overall judgment results are shown with the symbol "x" indicating poor, "△" indicating acceptable, and "○" indicating good. The symbol "○" indicates a case where the resistance value of the sample is 100MΩ or more and the mean time to failure (MTTF) is 50 or more. The symbol "x" indicates a case where the resistance value is less than 50MΩ and the mean time to failure (MTTF) is less than 50. The symbol "△" indicates a judgment result other than the symbols "○" and "x" mentioned above.

[0047] [Table 2]

[0048] For example, in Sample 4, Sample 7, and Sample 10 in Table 1.2, the covariance Sxy of the concentration of the first additive component and the concentration of the second additive component is 3.1. The standard deviation Sx of the concentration of the first additive component is 6.0, and the standard deviation Sy of the concentration of the second additive component is 2.0. In addition, in Sample 6 in Table 1.2, the covariance Sxy of the concentration of the first additive component and the concentration of the second additive component is 1.9. The standard deviation Sx of the concentration of the first additive component is 5.2, and the standard deviation Sy of the concentration of the second additive component is 1.2.

[0049] In Tables 1 and 2 above, sample 1 had a firing temperature rise rate of 1000°C / hr, 1.0 mol% dysprosium (Dy) and 1.0 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.1, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 2.5, an insulation resistance value of less than 1 MΩ, and a mean time to failure (MTTF) that was not measurable.

[0050] Sample 2 had a firing heating rate of 1000°C / hr, 0.5 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.3, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 50 MΩ, and a mean time to failure (MTTF) of 80 hours.

[0051] Sample 3 had a firing heating rate of 3000°C / hr, 1.0 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.5, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 100 MΩ, and a mean time to failure (MTTF) of 90 hours.

[0052] Sample 4 had a firing heating rate of 10,000°C / hr, 1.0 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.8, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 150 MΩ, and a mean time to failure (MTTF) of 100 hours.

[0053] Sample 5 had a firing heating rate of 10,000°C / hr, 0.1 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.3, a concentration difference of dysprosium (Dy) of 2.5, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 50 MΩ, and a mean time to failure (MTTF) of 10 hours.

[0054] Sample 6 had a firing heating rate of 10,000°C / hr, 0.5 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.1, a concentration difference of dysprosium (Dy) of 3.0, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 100 MΩ, and a mean time to failure (MTTF) of 50 hours.

[0055] Sample 7 had a firing heating rate of 10,000°C / hr, 0.5 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.8, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 150 MΩ, and a mean time to failure (MTTF) of 100 hours.

[0056] Sample 8 had a firing heating rate of 10,000°C / hr, 1.0 mol% dysprosium (Dy) and 0.1 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.3, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 1.0, an insulation resistance of 50 MΩ, and a mean time to failure (MTTF) of 10 hours.

[0057] Sample 9 had a firing heating rate of 10,000°C / hr, 1.0 mol% dysprosium (Dy) and 0.2 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.5, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 1.5, an insulation resistance of 100 MΩ, and a mean time to failure (MTTF) of 50 hours.

[0058] Sample 10 had a firing heating rate of 10,000°C / hr, 1.0 mol% dysprosium (Dy) and 0.5 mol% gadolinium (Gd) added, a correlation coefficient between dysprosium (Dy) and gadolinium (Gd) of 0.5, a concentration difference of dysprosium (Dy) of 3.5, a concentration difference of gadolinium (Gd) of 2.0, an insulation resistance of 150 MΩ, and a mean time to failure (MTTF) of 100 hours.

[0059] Coefficient of determination R 2 The range is 0.5≦R 2 The reason is as follows: When the two graphs for Dy and Gd are completely in agreement, the coefficient of determination R 2 Since it is 1, the coefficient of determination R 2 is in the range of 1 or less. As shown by lines L21 and L22 in Figure 6, the two types of graphs are somewhat consistent, and the coefficient of determination R 2 was measured at five locations, and the average linear approximation was calculated to be 0.637. The lower limit was set to 0.5 to allow for some margin around this calculated value of 0.637.

[0060] The dielectric layer 4 has a coefficient of determination R 2 However, as mentioned above, 0.5≦R 2 By adding SiO2 so that the ratio is ≦1.0, the grain boundaries between the particles constituting the dielectric layer 4 become clear, and the grain boundaries capture oxygen vacancies. The formation of such grain boundaries prevents the capture of lattice vacancies in oxygen, which captures atomic defects such as impurities or vacancies, and prevents the formation of space charge polarization, thereby suppressing the generation of an internal electric field at the crystal grain boundaries. As a result, the effective potential barrier is prevented from decreasing, thereby suppressing leakage current, reducing dielectric breakdown, and improving the lifespan.

[0061] The ceramic grain size is 0.3 μm or less, and the thickness of each dielectric layer 4 is 3 μm or less. With this configuration, when a core-shell structure is formed with a grain size of 100 to 150 nm for the main raw material of a thin film type in which grain growth is suppressed, for example, a multilayer ceramic capacitor with a ceramic grain size of 0.1 to 0.3 μm and excellent insulation resistance can be obtained.

[0062] Figure 8 is an enlarged photograph of ceramic particles when the dielectric layer was semi-quantitatively analyzed by TEM-EDS. The TEM-EDS measurement conditions were as follows: the center of the multilayer ceramic capacitor was photographed at a magnification of 30,000x / 1μm, the electron beam for dysprosium (Dy) was set to Mz line, and the electron beam for gadolinium (Gd) was set to La line, and measurements were taken at five random locations without overlap within an area of ​​0.1μm x 1μm.

[0063] Fig. 9 is a graph showing the concentration distribution in the scanning region S of the map diagram of Fig. 8. In order to confirm that dysprosium (Dy) is dissolved in the titanium (Ti) site and gadolinium (Gd) is dissolved in the barium (Ba) site, the present inventors calculated the solid solution ratio including oxides of other metal elements lithium (Li), magnesium (Mg), vanadium (V), manganese (Mn), tungsten (W), ytterbium (Yb), and aluminum (Al).

[0064] A simulation was performed to show that dysprosium (Dy) enters the Ti site and gadolinium (Gd) enters the Ba site. As shown in FIG. 9, dysprosium (Dy) and gadolinium (Gd) have similar concentration distributions, and the following results are obtained: (a) dysprosium (Dy) becomes an acceptor that captures oxygen vacancies, (b) gadolinium (Gd) suppresses the generation of oxygen vacancies, and (c) the presence of dysprosium (Dy) and gadolinium (Gd) in the same position suppresses the generation of excess carriers. Also, O2⇔V0 2+ +2e + It was confirmed that the reaction causes oxygen to escape from the main raw material, barium titanate (BaTiO3), and the resulting vacancies drift, resulting in a decrease in the high-temperature load life.

[0065] FIG. 10 is a graph showing the results of a simulation of the solid solution state of dysprosium (Dy) and gadolinium (Gd). In FIG. 10, the A site in the legend is Ba, and the B site is Ti. The numbers 1, 2, ..., 5, and 6 attached to A and B represent the valence of each atom. For example, "B-6" represents a portion in which an atom with a valence of 6 is solid-dissolved in the B site. The composition (mol% / main raw material) of the additives including the glass component and the firing conditions are as follows. The main raw material is BaTiO3, the main raw material A / B ratio is 1.007, and the additives include Gd2O3 and Dy2O3, and the contents of these are 0.366 and 1.098, respectively. The firing furnace was used at a temperature of 1230 degrees, with a firing time of 2 minutes and a temperature drop time of 2 to 4 minutes. The oxygen concentration in the firing furnace was 2.14×10 -9 (atm) was used for the transaction.

[0066] The fired laminate containing such additives had an oxygen vacancy concentration of 0.143% and a conduction band electron concentration (BTO+e ― The valence band hole concentration (+h of BTO) is 0.00093%. + (Percentage of respondents).

[0067] In the defect equation, (a) dysprosium (Dy) is an acceptor (captures oxygen vacancies), (b) gadolinium (Gd) is a donor (suppresses the generation of oxygen vacancies), and (c) dysprosium (Dy) and gadolinium (Gd) in the same position suppress the generation of excess carriers, so it can be expressed by (a), (b), and (c). O2⇔Vo 2+ +2e - It is believed that the high temperature load life is reduced due to the drift of vacancies formed after oxygen is removed from the main component BT. (a) Dy 3+ , Ti 4+ … is the reaction when Dy is dissolved in the main raw material; 2Dy Ti + +V O 2+ This occurs. (b) Gd 3+ , B.A. 2+, O 2- … is the reaction when Gd is dissolved in the main raw material; 2Gd Ba + +O 2- ...is difficult to escape to the outside as O2, so oxygen vacancies are unlikely to occur. (c) When Dy and Gd are extra, DyTi - +h + , Gd Ba + +e - ⇒DyTi - +GdBa + ... is the case where Dy and Gd are excessive, and it is considered that each generates carriers and reduces the resistance value.

[0068] For the above reasons, the shell portion reduces the probability of contact between the barium titanates (BaTiO3) in the core portion, making it difficult for grains to grow due to contact between the barium titanates (BaTiO3). By making it difficult for grains to grow, the area of ​​the grain boundaries can be maintained. As a result, the concentration of gadolinium (Gd) is higher in the outer periphery of the main raw material particle compared to the center. Gadolinium (Gd) forms a core-shell structure and acts as a donor to suppress the generation of oxygen vacancies.

[0069] In the multilayer ceramic capacitor according to the present disclosure, the concentration of the first additive component and the concentration of the second additive component are determined by a coefficient of determination R 2 However, 0.5≦R 2 Since the composition satisfies the condition of ≦1.0, it is possible to provide a multilayer ceramic capacitor in which the generation of excess carriers is suppressed and the dielectric layers are made of a dielectric material that has high insulation resistance even under a high electric field strength.

[0070] The present disclosure can implement the following configurations (1) to (7).

[0071] (1) A laminate in which dielectric layers and internal electrodes are alternately laminated, and a pair of external electrodes having different polarities are provided at both ends of the laminate, The dielectric layer contains a barium titanate-based solid solution as a main component and a first additive component and a second additive component, The coefficient of determination R of the concentration of the first added component and the concentration of the second added component 2 where Sxy is the covariance of the concentration of the first additive component and the concentration of the second additive component, Sx is the standard deviation of the concentration of the first additive component, and Sy is the standard deviation of the concentration of the second additive component, 2 =S 2 When expressed as xy / Sx Sy, 0.5≦R 2 ≦1.0.

[0072] (2) the first additive component is an oxide of one metal element selected from dysprosium, magnesium, manganese, and vanadium; The multilayer ceramic capacitor according to the above configuration (1), wherein the second additive component is an oxide of one metal element selected from the group consisting of gadolinium, yttrium, ytterbium, holmium, and terbium.

[0073] (3) The multilayer ceramic capacitor according to the above configuration (1) or (2), wherein the first additive component has a region with a higher concentration on the periphery of the crystal grains of the barium titanate compared to the crystal grains.

[0074] (4) The multilayer ceramic capacitor according to any one of the above configurations (1) to (3), wherein the first additive component has a region with a higher concentration in an outer periphery of a crystal grain of the barium titanate compared to a center of the crystal grain.

[0075] (5) The multilayer ceramic capacitor according to any one of the above configurations (1) to (4), wherein the ratio of the maximum concentration to the minimum concentration of the first additive component is 3.0 or more in an area of ​​0.1 μm × 1 μm in the dielectric layer.

[0076] (6) The multilayer ceramic capacitor according to any one of the above configurations (1) to (5), wherein the difference between the maximum and minimum concentrations of the first additive component is 1.5 or more in an area of ​​0.1 μm × 1 μm in the dielectric layer.

[0077] <7> The dielectric layer is composed of particles having a particle size of 0.3 μm or less, The multilayer ceramic capacitor according to any one of the above configurations (1) to (6), wherein the thickness of each of the dielectric layers is 3 μm or less.

[0078] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-mentioned embodiments, and various modifications and improvements are possible within the scope of the gist of the present invention. It goes without saying that all or part of the components of each of the above-mentioned embodiments can be appropriately combined within the scope of not contradicting each other. [Explanation of symbols]

[0079] 1. Multilayer ceramic capacitors 2. Laminate 3a 1st external electrode 3b 2nd external electrode 4 Dielectric Layer 5 Internal electrode layer 7a 1st page 7b 2nd side 8a 1st end face 8b 2nd end face 9a 1st side 9b Second side

Claims

1. A laminate in which dielectric layers and internal electrodes are alternately laminated, and a pair of external electrodes having different polarities are provided at both ends of the laminate, The dielectric layer contains a barium titanate-based solid solution as a main component and a first additive component and a second additive component, The coefficient of determination R of the concentration of the first added component and the concentration of the second added component ２ where Sxy is the covariance of the concentration of the first additive component and the concentration of the second additive component, Sx is the standard deviation of the concentration of the first additive component, and Sy is the standard deviation of the concentration of the second additive component, R ２ = S ２ When expressed as xy / Sx·Sy, 0.5≦R ２ A multilayer ceramic capacitor that satisfies the requirements of ≦1.

0.

2. The first additive component is an oxide of one metal element selected from dysprosium, magnesium, manganese, and vanadium, 2. The multilayer ceramic capacitor according to claim 1, wherein the second additive component is an oxide of one metal element selected from the group consisting of gadolinium, yttrium, ytterbium, holmium, and terbium.

3. 2. The multilayer ceramic capacitor according to claim 1, wherein the first additive component has a region with a higher concentration in an outer periphery of the crystal grain of the barium titanate compared to the crystal grain.

4. 2. The multilayer ceramic capacitor according to claim 1, wherein the first additive component has a region in which the concentration is higher in an outer periphery of a crystal grain of the barium titanate than in a central portion of the crystal grain.

5. 5. The multilayer ceramic capacitor according to claim 3, wherein the ratio of the maximum concentration to the minimum concentration of said first additive component is 3.0 or more in an area of ​​0.1 μm×1 μm in said dielectric layer.

6. 5. The multilayer ceramic capacitor according to claim 3, wherein the difference between the maximum and minimum concentrations of said first additive component is 1.5 or more within an area of ​​0.1 μm×1 μm in said dielectric layer.

7. the dielectric layer is composed of particles having a particle size of 0.3 μm or less; 5. The multilayer ceramic capacitor according to claim 3, wherein each of said dielectric layers has a thickness of 3 [mu]m or less.

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