Dielectric and multilayer capacitor including the same

Abstract

The present disclosure provides a dielectric and a multilayer capacitor including the same. The multilayer capacitor includes a main body including a plurality of dielectric layers and a plurality of internal electrodes stacked and the dielectric layers interposed between the plurality of internal electrodes, and an external electrode disposed on an outer surface of the main body and connected to the internal electrodes, respectively. The plurality of dielectric layers includes a dielectric represented by a formula of BaM1 a Ti 1‑x Sn x M2 b O3(0.008≤x≤0.05, 0.006≤a≤0.03 and 0.0006≤b<0.006), wherein M1 includes a rare earth element, and M2 includes at least one of Mn and V.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0176581, filed on December 16, 2020, with the Korean Intellectual Property Office, and Korean Patent Application No. 10-2021-0074123, filed on June 8, 2021, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to a dielectric and a multilayer capacitor including the dielectric. Background Technology

[0003] A capacitor is a device that stores electrical energy. Essentially, when a voltage is applied to a capacitor with its two electrodes facing each other, charge accumulates at each electrode. When a direct current (DC) voltage is applied to a capacitor, current flows through the capacitor while charge accumulates, but stops flowing once the charge accumulation is complete. Conversely, when an alternating current (AC) voltage is applied to a capacitor, AC current flows through the capacitor while the polarities of the electrodes alternate.

[0004] Such capacitors can be classified according to the type of insulator disposed between the electrodes as follows: aluminum electrolytic capacitors in which the electrodes are formed of aluminum and a thin oxide layer is disposed between the electrodes formed of aluminum; tantalum capacitors in which tantalum is used as the electrode material; ceramic capacitors in which a dielectric with a high dielectric constant, such as barium titanate, is used between the electrodes; multilayer ceramic capacitors (MLCCs) in which a ceramic with a high dielectric constant is used as the dielectric disposed between the electrodes in a multilayer structure; and film capacitors in which a polystyrene film is used as the dielectric disposed between the electrodes.

[0005] Furthermore, due to their excellent temperature and frequency characteristics, and the ability to be implemented in small sizes, multilayer ceramic capacitors have recently been widely used in various fields such as high-frequency circuits. Recently, efforts have continued to be made to achieve multilayer ceramic capacitors with smaller dimensions, and for this purpose, the thickness of the dielectric layer and internal electrodes has been reduced. In addition, research has been conducted on dielectric materials for achieving multilayer ceramic capacitors with high capacitance and excellent reliability. Summary of the Invention

[0006] One aspect of this disclosure provides a multilayer capacitor with improved performance due to the use of a dielectric material having a high dielectric constant and excellent reliability.

[0007] According to one aspect of this disclosure, a multilayer capacitor may include: a body comprising a plurality of stacked dielectric layers and a plurality of inner electrodes, wherein the dielectric layers are disposed between the plurality of inner electrodes; and outer electrodes disposed on an outer surface of the body and respectively connected to the inner electrodes. The plurality of dielectric layers may comprise those of formula BaM1. a Ti 1-x Sn x M2 b A dielectric material represented by O3 (0.008≤x≤0.05, 0.006≤a≤0.03 and 0.0006≤b<0.006), wherein M1 includes rare earth elements and M2 includes at least one of Mn and V.

[0008] The rare earth element may include Dy.

[0009] The dielectric may include 0.006 mol to 0.012 mol of Dy relative to 1 mol of Ba.

[0010] M2 may include both Mn and V, and the dielectric may include Mn in a content of 0.0003 mol to 0.0035 mol relative to 1 mol of Ba, and the dielectric may include V in a content of 0.0003 mol to 0.0025 mol relative to 1 mol of Ba.

[0011] The dielectric may further include an Al component in an amount greater than or equal to 0.003 mol and less than 0.012 mol, relative to 1 mole of Ba.

[0012] The dielectric may further include Mg in an amount greater than or equal to 0.001 mol and less than 0.012 mol, relative to 1 mole of Ba.

[0013] The dielectric may further include a Si content of greater than or equal to 0.03 moles, relative to 1 mole of Ba.

[0014] The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.12≤a / x≤3.75.

[0015] The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.012≤b / x≤0.75.

[0016] In the formula BaM1 a Ti 1-x Sn x M2b In O3, the molar ratio of Ba to Ti (Ba / Ti) can be from 1.010 to 1.050.

[0017] At least one of the grains included in the plurality of dielectric layers may have a core-shell structure, the core-shell structure comprising a core and a shell covering the core.

[0018] The Sn content in the shell can be higher than the Sn content in the core.

[0019] The average thickness of each of the plurality of dielectric layers can be 500 nm or less.

[0020] The average thickness of each of the plurality of internal electrodes may be 400 nm or less.

[0021] According to one aspect of this disclosure, a method that can be derived from formula BaM1 a Ti 1-x Sn x M2 b A dielectric material represented by O3 (0.008≤x≤0.05, 0.006≤a≤0.03 and 0.0006≤b<0.006), wherein M1 includes rare earth elements and M2 includes at least one of Mn and V.

[0022] The rare earth element may include Dy, and the content of Dy relative to 1 mole of Ba may be from 0.006 moles to 0.012 moles.

[0023] M2 may include both Mn and V, and the content of Mn relative to 1 mole of Ba may be greater than or equal to 0.0003 moles and less than 0.0035 moles, and the content of V relative to 1 mole of Ba may be greater than or equal to 0.0003 moles and less than 0.0025 moles.

[0024] The dielectric may further include an Al component in an amount greater than or equal to 0.003 mol and less than 0.012 mol, relative to 1 mole of Ba.

[0025] The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.12≤a / x≤3.75.

[0026] The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.012≤b / x≤0.75. Attached Figure Description

[0027] The above and other aspects, features and advantages of this disclosure will be more clearly understood from the following detailed embodiments, taken in conjunction with the accompanying drawings, in which:

[0028] Figure 1 This is a perspective view schematically illustrating the appearance of a multilayer capacitor according to an exemplary embodiment of the present disclosure;

[0029] Figure 2 It is along Figure 1 A cross-sectional view taken from line I-I' in a multilayer capacitor;

[0030] Figure 3 It is along Figure 1 A cross-sectional view taken from line II-II' in a multilayer capacitor; and

[0031] Figure 4 This is a schematic enlarged view of the grains in the dielectric layer. Detailed Implementation

[0032] In the following, exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings.

[0033] Figure 1 This is a perspective view schematically illustrating the appearance of a multilayer capacitor according to an exemplary embodiment of the present disclosure. Figure 2 It is along Figure 1 A cross-sectional view taken from line I-I' in a multilayer capacitor. Figure 3 It is along Figure 1 A cross-sectional view taken from line II-II' in a multilayer capacitor. Figure 4 This is a schematic enlarged view of the grains in the dielectric layer.

[0034] Reference Figures 1 to 3 The multilayer capacitor 100 according to exemplary embodiments of the present disclosure may include a body 110 and external electrodes 131 and 132. The body 110 includes a dielectric layer 111 stacked in a first direction (X direction) and a plurality of internal electrodes 121 and 122, with the dielectric layer 111 situated between the plurality of internal electrodes 121 and 122. Furthermore, the plurality of dielectric layers 111 may include those of formula BaM1. a Ti 1-x Sn x M2 b A dielectric material represented by O3 (0.008≤x≤0.05, 0.006≤a≤0.03 and 0.0006≤b<0.006), wherein M1 includes rare earth elements and M2 includes at least one of Mn and V.

[0035] The body 110 may include a stacked structure in which multiple dielectric layers 111 are stacked in a first direction (X direction), and can be obtained, for example, by stacking and then sintering multiple green sheets. The multiple dielectric layers 111 can be integrally formed by sintering as described above. Figure 1 As shown, the body 110 may have a shape similar to a cuboid. In this exemplary embodiment, the dielectric layer 111 included in the body 110 may include a barium titanate-based ceramic dielectric, which may include Sn, rare earth elements, and transition metal components. The grain size and dielectric constant of the dielectric can be effectively controlled by adjusting the composition and content of the additive. In this case, when such an additive is used and simultaneously coated on the matrix material powder, the growth of the dielectric grains can be effectively controlled, and the withstand voltage characteristics of the dielectric, etc., can be improved.

[0036] As described above, dielectric layer 111 may include materials of formula BaM1 a Ti 1-x Sn x M2 b The dielectric material is represented by O3 (0.008≤x≤0.05, 0.006≤a≤0.03, and 0.0006≤b<0.006), where M1 includes rare earth elements and M2 includes at least one of Mn and V. The Sn component used for doping can be coated onto the matrix material powder and can suppress the growth of dielectric grains during sintering. Therefore, even when the dielectric material is achieved using fine powder, excessive increase in grain size can be suppressed, and a high dielectric constant can be ensured. Specifically, fine dielectric powder is required to reduce the thickness of the dielectric layer 111, and in the case of fine barium titanate powder, the driving force for sintering increases, making grain growth control during sintering difficult, and excessive grain growth occurs until the sintered body becomes dense. As a result, deterioration in withstand voltage characteristics and high-temperature reliability may occur, and the effective capacitance in a DC field may be reduced. In this exemplary embodiment, the Sn component is added at an optimized range to solve the above-mentioned problems, and this effect can be more fully manifested when the Sn component is coated onto the matrix material powder while using the Sn component.

[0037] Furthermore, the Sn component can act as an acceptor, thereby improving the reduction resistance of the dielectric material. Additionally, by replacing Ti with Sn through Sn doping, a crystal structure with a high dielectric constant can be obtained, thus increasing the dielectric constant of the dielectric. Therefore, by adding the Sn component, a high dielectric constant and improved withstand voltage characteristics can be ensured even when the thickness of the dielectric layer 111 is small. The amount of Sn added relative to 1 mole of Ba can be from 0.008 mol to 0.05 mol, and the aforementioned effects are not significantly observed when the amount of Sn added is less than 0.008 mol. On the other hand, when the amount of Sn added is greater than 0.05 mol, impact resistance and other properties may deteriorate due to the network formed between Sn particles. The Sn component can be uniformly dispersed in the grains during sintering, and can even exist at the interface between the dielectric layer 111 and the inner electrode 121, and at the interface between the dielectric layer 111 and the inner electrode 122. Furthermore, when the growth of dielectric grains is limited, such as... Figure 4 As shown, the core-shell structure can be preserved within the dielectric grain. (Refer to...) Figure 4 The dielectric grains may include both core-shell grains 11 and grains 12 without a core-shell structure, and the core-shell grains 11 include a core 11a and a shell 11b. Here, the Sn content in the shell 11b may be higher than the Sn content in the core 11a.

[0038] With the addition of Sn, the Ba / Ti ratio can be increased compared to ordinary barium titanate, thereby suppressing the growth of dielectric grains. In this case, the Ba / Ti ratio can be in the range of 1.010 to 1.050. When the Ba / Ti ratio (Ba / Ti) is 1.010 to 1.050, corresponding to a high molar ratio, the growth of dielectric grains during sintering can be suppressed, and densification can be achieved. As a result, electrical properties (withstand voltage characteristics) and moisture resistance are improved.

[0039] In the dielectric, M1 is a rare earth element, and the rare earth element may include Dy. M1 is included in a content of 0.006 mol to 0.03 mol relative to 1 mole of Ba. When the dielectric includes Dy, the dielectric may include 0.006 mol to 0.012 mol of Dy relative to 1 mole of Ba. When the dielectric includes other rare earth elements besides Dy (e.g., Tb, Eu, Ce, Sc, Y, etc.), as described above, the total amount of rare earth elements relative to 1 mole of Ba may be 0.006 mol to 0.03 mol. Furthermore, in the dielectric, M2 includes at least one of Mn and V, and is included in a content of 0.0006 mol to 0.006 mol relative to 1 mole of Ba, where Mn and V are transition metals. In this case, M2 may include both Mn and V. Relative to 1 mole of Ba, the dielectric may include Mn in a content greater than or equal to 0.0003 mol and less than 0.0035 mol, and relative to 1 mole of Ba, the dielectric may include V in a content greater than or equal to 0.0003 mol and less than 0.0025 mol. Similar to the Sn composition, M1 and M2 can be added simultaneously, coating both M1 and M2 onto the matrix material powder. However, M1 and M2 can be uniformly dispersed within the grains during sintering. In this case, rare earth elements and transition metal components can be used to enhance the Schottky barrier and prevent a decrease in the insulation resistance of the dielectric material, thereby improving the reliability of the dielectric.

[0040] In this exemplary embodiment, the contents of M1 and M2 can satisfy specific conditions regarding the content of Sn. That is, the above formula can satisfy the condition 0.12 ≤ a / x ≤ 3.75. Simultaneously or individually, the above formula can satisfy the condition 0.012 ≤ b / x ≤ 0.75. This condition represents an appropriate range of relative contents of Sn, M1, and M2 as additives and used for doping (this appropriate range is the range set with consideration of the above-described functions).

[0041] In addition to the components mentioned above, the dielectric may also include one or more secondary components. Specifically, relative to 1 mole of Ba, the dielectric may further include Al in an amount greater than or equal to 0.003 mol and less than 0.012 mol. Furthermore, relative to 1 mole of Ba, the dielectric may further include Mg in an amount greater than or equal to 0.001 mol and less than 0.012 mol. Additionally, relative to 1 mole of Ba, the dielectric may further include Si in an amount greater than or equal to 0.03 mol. Such additional secondary components may be added directly to the matrix material powder or added by coating onto the matrix material powder.

[0042] Furthermore, the composition of the dielectric used in multilayer capacitors can be analyzed using the following methods. In a destructive method, the multilayer capacitor is crushed, the internal electrodes are removed, the dielectric is sorted, and the composition of the sorted dielectric can be analyzed using a device such as inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). In a non-destructive method, the composition of the dielectric grains in the central part of the wafer can be analyzed using transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS). Here, the Si composition can be measured at the grain boundaries, rather than inside the grains.

[0043] Furthermore, as described above, when the dielectric layer 111 and the inner electrodes 121 and 122 are thinner than conventional components, the effects of improved withstand voltage characteristics, etc., obtainable by using a dielectric can be significant. The thickness of the dielectric layer 111 can be 500 nm or less, and the thickness of the inner electrodes 121 and 122 can be 400 nm or less. Here, the thickness of the dielectric layer 111 can refer to the average thickness of each dielectric layer 111 disposed between the inner electrodes 121 and 122. As an example of a measurement standard, the average thickness of the dielectric layer 111 can be measured by scanning images of cross-sections of the body 110 in the first direction (X direction) and the third direction (Z direction) using a scanning electron microscope (SEM). For example, for any dielectric layer extracted from an image of a cross-section in the first direction and the third direction cut from the central portion of the body 110 in the second direction (Y direction) using a scanning electron microscope (SEM), the average value can be measured by measuring its thickness at 30 equally spaced points in the third direction. The thickness can be measured at 30 equally spaced points in the capacitor forming section (the area where the inner electrodes 121 and 122 are stacked on top of each other).

[0044] Similarly, the thickness of inner electrodes 121 and 122 can refer to the average thickness of each of the inner electrodes 121 and 122. In this case, the average thickness of the inner electrodes 121 and 122 can be measured by scanning images of the body 110 in the first direction (X direction) and the third direction (Z direction) using a scanning electron microscope (SEM). For example, for any inner electrode 121 and 122 extracted from images of cross-sections in the first and third directions cut from the central portion of the body 110 in the second direction (Y direction) using a scanning electron microscope (SEM), the average thickness can be measured by measuring its thickness at 30 equally spaced points in the third direction. The 30 equally spaced points can be measured in the capacitor forming area, which is the area where the inner electrodes 121 and 122 overlap each other.

[0045] The plurality of internal electrodes 121 and 122 can each be obtained, for example, by printing a paste containing a conductive metal of a predetermined thickness on one surface of a ceramic green sheet, and then sintering the resulting structure. In this case, the plurality of internal electrodes 121 and 122 may include a first internal electrode 121 and a second internal electrode 122 exposed from surfaces of the body 110 that are opposite to each other in the third direction (Z direction), such as... Figure 2 As shown in the diagram. Here, the third direction (Z direction) may be perpendicular to the first direction (X direction) and the second direction (Y direction), where the second direction is the direction in which the first surface and the second surface of the effective portion of the body 110 face each other. The first inner electrode 121 and the second inner electrode 122 may be connected to different outer electrodes 131 and 132, respectively. The first inner electrode 121 and the second inner electrode 122 may have different polarities when driven, and the first inner electrode 121 and the second inner electrode 122 may be electrically insulated from each other by a dielectric layer 111 disposed between them. However, the number of outer electrodes 131 and 132 and the manner in which they are connected to the inner electrodes 121 and 122 may vary depending on the embodiment. Examples of the main constituent materials of the inner electrodes 121 and 122 may include nickel (Ni), copper (Cu), palladium (Pd), and silver (Ag), as well as alloys thereof.

[0046] External electrodes 131 and 132 may be formed on the outer surface of the body 110, and may include a first external electrode 131 and a second external electrode 132 electrically connected to the first internal electrode 121 and the second internal electrode 122, respectively. External electrodes 131 and 132 may be formed by preparing a paste using a material containing a conductive metal and applying the paste to the body 110. Examples of conductive metals may include nickel (Ni), copper (Cu), palladium (Pd), gold (Au), and alloys thereof. Each of the external electrodes 131 and 132 may also include a plating containing Ni, Sn, etc.

[0047] The inventors of this disclosure prepared a dielectric having the following composition and conducted reliability tests. Unlike the description above, in the following composition, the content of each element is based on 100 moles of Ba instead of 1 mole of Ba. The results of the High Accelerated Life Test (HALT) for each sample are as follows.

[0048] Table 1

[0049] Sample No. Sn Dy Mn V Al Mg HALT #1 0 0.800 0.100 0.104 0.880 1.000 X #2 0 0.600 0.050 0.052 0.640 0.500 X #3 1.000 0.600 0.03 0.03 0.880 1.000 O #4 1.000 0.600 0.075 0.078 0.760 0.750 O #5 1.000 0.600 0.050 0.052 0.640 0.500 O #6 1.000 0.800 0.050 0.052 0.640 0.500 O #7 1.000 0.840 0.075 0.075 0.360 0.100 O #8 1.000 1.200 0.150 0.150 0.720 0.200 O #9 1.000 0.900 0.35 0.25 0.620 0.150 X #10 1.000 1.080 0.098 0.098 1.2 1.2 X

[0050] In Table 1, “O” indicates a good result and “X” indicates a relatively poor result.

[0051] Based on the test results above, the samples (#3 to #8) that satisfy the above formula of this exemplary embodiment exhibit good results in HALT. These samples not only meet the expected capacitance conditions but also possess excellent withstand voltage characteristics and reliability. In the samples, Dy is used as the rare earth element, and excellent reliability is obtained when Dy is 0.600 mol to 1.200 mol relative to 100 mol of Ba. That is, excellent reliability is obtained when the rare earth element is 0.600 mol to 1.200 mol relative to 100 mol of Ba. However, as mentioned above, in addition to Dy, the dielectric may also include other rare earth elements (e.g., Tb, Eu, Ce, Sc, Y, etc.). In this case, as a preferred condition, the total amount of rare earth elements may be 0.6 mol to 3.0 mol relative to 100 mol of Ba. Unlike the samples according to the embodiments, the remaining samples according to the comparative example do not satisfy at least one of the Sn content conditions, rare earth element content conditions, transition metal content conditions, etc., of this disclosure, and exhibit relatively poor withstand voltage characteristics in HALT.

[0052] As described above, according to exemplary embodiments of the present disclosure, multilayer capacitors can have high capacitance and excellent reliability (such as excellent withstand voltage characteristics).

[0053] While exemplary embodiments have been shown and described above, it will be readily understood by those skilled in the art that modifications and variations may be made without departing from the scope of this disclosure as defined by the appended claims.

Claims

1. A multilayer capacitor, comprising: The main body includes multiple stacked dielectric layers and multiple internal electrodes, with the dielectric layers located between the multiple internal electrodes; as well as External electrodes are disposed on the outer surface of the main body and are respectively connected to the internal electrodes. The plurality of dielectric layers include those of formula BaM1 a Ti 1-x Sn x M2 b The dielectric material represented by O3, wherein 0.008≤x≤0.05, 0.006≤a≤0.03 and 0.0006≤b<0.006, M1 includes rare earth elements, and M2 includes at least one of Mn and V.

2. The multilayer capacitor according to claim 1, wherein, The rare earth element includes Dy.

3. The multilayer capacitor according to claim 2, wherein, The dielectric comprises Dy in an amount of 0.006 mol to 0.012 mol relative to 1 mol of Ba.

4. The multilayer capacitor according to claim 1, wherein, M2 comprises both Mn and V. The dielectric comprises Mn in an amount greater than or equal to 0.0003 mol and less than 0.0035 mol relative to 1 mol of Ba, and the dielectric comprises V in an amount greater than or equal to 0.0003 mol and less than 0.0025 mol relative to 1 mol of Ba.

5. The multilayer capacitor according to claim 1, wherein, The dielectric also includes an Al component in an amount greater than or equal to 0.003 mol and less than 0.012 mol, relative to 1 mole of Ba.

6. The multilayer capacitor according to claim 1, wherein, The dielectric also includes Mg in an amount greater than or equal to 0.001 mol and less than 0.012 mol, relative to 1 mole of Ba.

7. The multilayer capacitor according to claim 1, wherein, The dielectric also includes a Si component at a concentration of ≥0.03 moles, relative to 1 mole of Ba.

8. The multilayer capacitor according to claim 1, wherein, The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.12≤a / x≤3.

75.

9. The multilayer capacitor according to claim 1, wherein, The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.012≤b / x≤0.

75.

10. The multilayer capacitor according to claim 1, wherein, In the formula BaM1 a Ti 1-x Sn x M2 b In O3, the molar ratio of Ba to Ti is 1.010 to 1.

050.

11. The multilayer capacitor according to claim 1, wherein, At least one of the grains included in the plurality of dielectric layers has a core-shell structure, the core-shell structure comprising a core and a shell covering the core.

12. The multilayer capacitor according to claim 11, wherein, The Sn content in the shell is higher than the Sn content in the core.

13. The multilayer capacitor according to claim 1, wherein, The average thickness of each of the plurality of dielectric layers is 500 nm or less.

14. The multilayer capacitor according to claim 1, wherein, The average thickness of each of the plurality of internal electrodes is 400 nm or less.

15. A method based on formula BaM1 a Ti 1-x Sn x M2 b O3 represents the dielectric, where, 0.008≤x≤0.05, 0.006≤a≤0.03 and 0.0006≤b<0.006, M1 includes rare earth elements and M2 includes at least one of Mn and V.

16. The dielectric according to claim 15, wherein, The rare earth element includes Dy, and the content of Dy is from 0.006 mol to 0.012 mol relative to 1 mol of Ba.

17. The dielectric according to claim 15, wherein, M2 includes both Mn and V. The content of Mn relative to 1 mole of Ba is greater than or equal to 0.0003 moles and less than 0.0035 moles, and the content of V relative to 1 mole of Ba is greater than or equal to 0.0003 moles and less than 0.0025 moles.

18. The dielectric of claim 15, wherein, relative to 1 mole of Ba, the dielectric further comprises an Al component in an amount greater than or equal to 0.003 moles and less than 0.012 moles.

19. The dielectric according to claim 15, wherein, The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.12≤a / x≤3.

75.

20. The dielectric according to claim 15, wherein, The formula BaM1 a Ti 1-x Sn x M2 b O3 satisfies the condition 0.012≤b / x≤0.75.

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