Dielectrics, capacitors, electric circuits, circuit boards, and devices

Abstract

A dielectric 10 includes a complex oxide. The complex oxide is amorphous and has a composition represented by CexAl1–xOk. In said composition represented by CexAl1–xOk, the condition 0.400≤x<0.90 is satisfied, and k is a value that preserves the electroneutrality of the complex oxide.

Description

[Technical Field]

[0001] The present disclosure relates to dielectrics, capacitors, electric circuits, circuit boards, and devices. [Background technology]

[0002] Conventionally, capacitors using metal oxides as dielectrics have been known.

[0003] For example, Patent Document 1 describes a capacitor element using an anode foil on which a dielectric oxide film is formed as a typical aluminum electrolytic capacitor. The dielectric oxide film is formed by anodization on the surface of the aluminum foil whose effective surface area has been increased by etching.

[0004] Additionally, Patent Document 1 describes a method for manufacturing an electrode foil in which aluminum is etched by applying an alternating current in an electrolyte. The electrolyte is an aqueous solution containing hydrochloric acid as its main component and at least one of sulfuric acid, oxalic acid, and phosphoric acid. In this manufacturing method, the current density of the applied alternating current reaches a maximum value at the beginning of the etching process and gradually decreases from that maximum value, eventually reaching zero midway through. It is explained that this manufacturing method can increase the surface area of ​​the electrode foil by generating dense, high-density etching pits, thereby increasing the capacitance of the aluminum electrolytic capacitor.

[0005] Patent Document 2 describes a capacitor having a dielectric layer located on the porous portion of a conductive porous substrate. The material for forming the dielectric layer is a metal oxide such as Al2O3. The dielectric layer is formed by a deposition method such as atomic layer deposition, rather than an anodic oxide film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-203529 [Patent Document 2] International Publication No. 2017 / 026247 Summary of the Invention [Problem to be solved by the invention]

[0007] The techniques described in Patent Documents 1 and 2 need to be reconsidered from the viewpoint of increasing the capacitance while maintaining low dielectric loss of the capacitor. Therefore, the present disclosure provides a dielectric that is advantageous from the viewpoint of increasing the capacitance while maintaining low dielectric loss of the capacitor. [Means for solving the problem]

[0008] The present disclosure provides: Ce x Al 1-x O k The composite oxide has a composition represented by the formula: In the composition, the condition of 0.400≦x<0.900 is satisfied, and k is a value that maintains the electrical neutrality of the composite oxide. A dielectric is provided. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a dielectric that is advantageous from the viewpoint of increasing the capacitance while keeping the dielectric loss of the capacitor low. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a capacitor according to an embodiment of the present disclosure. [Figure 2A] FIG. 2A is a cross-sectional view of a capacitor according to another embodiment of the present disclosure. [Figure 2B] FIG. 2B is a cross-sectional view of a modification of the capacitor shown in FIG. 2A. [Figure 3A] FIG. 3A is a diagram illustrating a schematic diagram of an electric circuit according to an embodiment of the present disclosure. [Figure 3B] FIG. 3B is a diagram schematically illustrating a circuit board according to an embodiment of the present disclosure. [Figure 3C]FIG. 3C is a schematic diagram of an apparatus according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a graph showing the relationship between the relative dielectric constant of the dielectric film and the atomic ratio of metal atoms in each sample. [Figure 5] FIG. 5 is a graph showing the relationship between the dielectric loss tangent of the dielectric film of each sample and the atomic ratio of metal atoms. [Figure 6] FIG. 6 shows X-ray diffraction (XRD) patterns of the dielectric films of Samples 1 to 4. [Figure 7] FIG. 7 shows XRD patterns of the dielectric films of Samples 5 and 6. [Figure 8] FIG. 8 shows XRD patterns of the dielectric films of Samples 7 to 11. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Findings that formed the basis of this disclosure) Porous portions can be formed by etching the surface of a metal foil. A metal foil having porous portions can be subjected to a chemical conversion treatment such as anodization to form a metal oxide on the surface of the metal skeleton of the porous portion, thereby producing a capacitor with a metal oxide as a dielectric. Because the porous portion has a large surface area, the capacitance of the capacitor can be increased. However, there are limits to how much the surface area of ​​the porous portion can be increased. Furthermore, depending on the application of the capacitor, it may be difficult to use a metal foil having porous portions as a capacitor electrode. It is also important to keep the dielectric loss of the capacitor low.

[0012] In view of these circumstances, the present inventors have conducted extensive research to develop a novel dielectric having advantageous properties from the viewpoint of increasing the capacitance while maintaining low dielectric loss in a capacitor. After extensive trial and error, the present inventors have newly discovered that a material containing a predetermined composite oxide containing Ce and Al is advantageous from the viewpoint of increasing the capacitance while maintaining low dielectric loss in a capacitor. As a result, the present inventors have devised the dielectric and capacitor disclosed herein.

[0013] (Summary of one aspect of the present disclosure) The dielectric according to the first aspect of the present disclosure comprises: Ce x Al 1-x O k The composite oxide has a composition represented by the formula: In the composition, the condition 0.400≦x<0.900 is satisfied, and k is a value that maintains the electrical neutrality of the composite oxide.

[0014] The dielectric according to the first aspect tends to have a high relative dielectric constant and a low dielectric loss tangent, which is advantageous from the viewpoint of increasing the capacitance while keeping the dielectric loss of the capacitor low.

[0015] In a second aspect of the present disclosure, for example, in the dielectric according to the first aspect, the dielectric may include a sputtered film. According to the second aspect, a dielectric film for a capacitor can be formed by sputtering.

[0016] In a third aspect of the present disclosure, for example, the dielectric according to the first or second aspect may be for a capacitor. According to the third aspect, this dielectric can be used in a capacitor.

[0017] A capacitor according to a fourth aspect of the present disclosure includes: A first electrode; a dielectric according to any one of the first to third aspects, disposed on the first electrode; and a second electrode covering at least a portion of the dielectric.

[0018] According to the fourth aspect, the dielectric tends to have a high relative dielectric constant and a low dielectric loss tangent, so that the capacitance of the capacitor tends to be high and the dielectric loss of the capacitor tends to be kept low.

[0019] In a fifth aspect of the present disclosure, for example, in the capacitor according to the fourth aspect, at least a portion of the first electrode may be porous. According to the fifth aspect, the surface area of ​​the first electrode is likely to be large, and the capacitance of the capacitor is likely to be high.

[0020] In a sixth aspect of the present disclosure, for example, in the capacitor according to the fourth or fifth aspect, the first electrode may contain a valve metal. According to the sixth aspect, a member containing a valve metal can be used as the first electrode.

[0021] In a seventh aspect of the present disclosure, for example, in the capacitor according to the sixth aspect, the valve metal may contain at least one selected from the group consisting of aluminum, tantalum, and niobium. According to the seventh aspect, a member containing such a valve metal can be used as the first electrode.

[0022] In an eighth aspect of the present disclosure, for example, in the capacitor according to any one of the fourth to seventh aspects, the second electrode may contain at least one selected from the group consisting of aluminum, tantalum, niobium, gold, silver, platinum, and nickel. According to the eighth aspect, a member containing such a metal can be used as the second electrode.

[0023] In a ninth aspect of the present disclosure, for example, the capacitor according to the fifth aspect may further include an electrolyte in contact with the second electrode. In addition, the electrolyte may be filled inside the porous material and include at least one selected from the group consisting of an electrolytic solution, a conductive polymer, and manganese oxide. According to the ninth aspect, a capacitor including an electrolyte such as an electrolytic solution can be provided.

[0024] An electric circuit according to a tenth aspect of the present disclosure includes the capacitor according to any one of the fourth to ninth aspects. According to the tenth aspect, the dielectric loss of the capacitor is likely to be low and the capacitance of the capacitor is likely to be high, which makes it easy to improve the characteristics of the electric circuit.

[0025] A circuit board according to an eleventh aspect of the present disclosure includes the capacitor according to any one of aspects 4 to 9. According to the eleventh aspect, the dielectric loss of the capacitor is likely to be low and the capacitance of the capacitor is likely to be high, which tends to improve the characteristics of the circuit board.

[0026] A device according to a twelfth aspect of the present disclosure includes the capacitor according to any one of aspects 4 to 9. According to the twelfth aspect, the dielectric loss of the capacitor is likely to be low and the capacitance of the capacitor is likely to be high, which makes it easy to improve the characteristics of the device.

[0027] (Embodiment) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0028] FIG. 1 is a cross-sectional view showing a capacitor 1a according to an example of an embodiment of the present disclosure. As shown in FIG. 1, the capacitor 1a includes a dielectric 10. In other words, the dielectric 10 is a material for a capacitor. The dielectric 10 is made of Ce. x Al 1-x O k The composite oxide includes a composite oxide having a composition represented by the formula: In this composition, the condition 0.400≦x<0.900 is satisfied. In addition, k is a value that maintains the electrical neutrality of the composite oxide. In the composite oxide, when the valence of Ce is trivalent, k is 1.5. In the composite oxide, when the valence of Ce is tetravalent, k is 1.7 or more and less than 1.95. The composite oxide is amorphous. When the dielectric 10 includes such a composite oxide, the dielectric 10 tends to have a high relative dielectric constant and a low dielectric loss tangent. Therefore, the capacitor 1a tends to exhibit a high capacitance and tend to maintain a low dielectric loss of the capacitor 1a.

[0029] The composite oxide contained in the dielectric 10 is, for example, a solid solution of aluminum oxide and cerium oxide.

[0030] x is preferably 0.475 or more, which makes it easier for the dielectric 10 to have a high relative dielectric constant. x may be 0.500 or more, or 0.600 or more, depending on the circumstances.

[0031] x is preferably 0.880 or less, more preferably 0.850 or less, even more preferably 0.840 or less, and particularly preferably 0.830 or less, whereby the dielectric 10 tends to have a low dielectric loss tangent.

[0032] The dielectric constant of dielectric 10 is not limited to a specific value. Dielectric 10 has a higher dielectric constant than, for example, Al2O3. The dielectric constant of dielectric 10 at 10 kHz is, for example, 14.0 or more, desirably 15.0 or more, and more desirably 18.0 or more. The dielectric constant of dielectric 10 at 10 kHz may be 22.0 or more, or may be 25.0 or more, depending on the case. The dielectric constant of dielectric 10 at 1 MHz is, for example, 13.0 or more, desirably 14.0 or more, more desirably 15.0 or more, and even more desirably 17.0 or more. The dielectric constant of dielectric 10 at 1 MHz may be 21.0 or more, or may be 24.0 or more, depending on the case.

[0033] The dielectric loss tangent of the dielectric 10 is not limited to a specific value. The dielectric loss tangent of the dielectric 10 at 10 kHz and 1 MHz is, for example, 0.020 or less. The dielectric loss tangent of the dielectric 10 at 10 kHz and 1 MHz may be, for example, less than 0.020.

[0034] As described above, the complex oxide is amorphous. When dielectric 10 contains such a complex oxide, leakage current is less likely to occur in dielectric 10. This is because it is believed that the occurrence of leakage current due to crystal grain boundaries can be suppressed in the complex oxide. Therefore, dielectric 10 is likely to have a high relative dielectric constant and a low dielectric loss tangent. For example, when an XRD pattern of a complex oxide at a diffraction angle of 10° to 50° has a half-width of 5° or less and no clear peak is observed against the background, it can be determined that the compound contained in dielectric 10 is amorphous.

[0035] As shown in FIG. 1, in the capacitor 1a, the dielectric 10 includes, for example, a film. The dielectric 10 includes, for example, a sputtered film. In this case, the dielectric 10 is likely to have a high relative dielectric constant and a low dielectric loss tangent. Furthermore, the composition ratio of each metal atom in the complex oxide is easily adjusted to a desired value. The dielectric 10 may be an anodic oxide film or other thin film. Methods for forming other thin films include, for example, vacuum evaporation, pulsed laser deposition (PLD), atomic layer deposition (ALD), and chemical vapor deposition (CVD).

[0036] 1, the capacitor 1a further includes a first electrode 21 and a second electrode 22. The dielectric 10 is disposed on the first electrode 21. The second electrode 22 covers at least a portion of the dielectric 10.

[0037] The materials forming the first electrode 21 and the second electrode 22 are not limited to a specific material. The first electrode 21 and the second electrode 22 contain, for example, a metal. The first electrode 21 is preferably, for example, a metal having electrical conductivity. The first electrode 21 contains, for example, a valve metal. Examples of the valve metal are aluminum, tantalum, and niobium. The first electrode 21 contains, for example, at least one valve metal selected from the group consisting of aluminum, tantalum, and niobium. The first electrode 21 may contain a noble metal such as gold or platinum, or may contain nickel.

[0038] The second electrode 22 is preferably, for example, a conductive metal. The second electrode 22 may contain, for example, a valve metal such as aluminum, tantalum, or niobium, or may contain a noble metal such as gold, silver, or platinum, or may contain nickel. The second electrode 22 contains, for example, at least one selected from the group consisting of aluminum, tantalum, niobium, gold, silver, platinum, and nickel.

[0039] As shown in FIG. 1, the first electrode 21 has a principal surface 21p. The "principal surface" refers to the surface of the electrode having the largest area. One principal surface of the dielectric 10 is in contact with the principal surface 21p, for example. The second electrode 22 has a principal surface 22p parallel to the principal surface 21p. The other principal surface of the dielectric 10 is in contact with the principal surface 22p, for example.

[0040] 2A is a cross-sectional view showing a capacitor 1b according to another embodiment of the present disclosure. Capacitor 1b has the same configuration as capacitor 1a, except for portions that will be specifically described. Components of capacitor 1b that are the same as or correspond to components of capacitor 1a are denoted by the same reference numerals, and detailed description thereof will be omitted. The description of capacitor 1a also applies to capacitor 1b, unless technically inconsistent.

[0041] 2A, in capacitor 1b, at least a portion of first electrode 21 is porous. This configuration tends to increase the surface area of ​​first electrode 21, and tends to increase the capacitance of the capacitor. Such a porous structure can be formed, for example, by etching a metal foil and sintering a powder.

[0042] 2A, for example, a film of dielectric 10 is formed on the surface of the porous portion of first electrode 21. In this case, the method of forming the film of dielectric 10 can be an anodic oxidation method or ALD.

[0043] In capacitor 1b, second electrode 22 is disposed so as to fill the voids around the porous portion of first electrode 21, for example.

[0044] The second electrode 22 may contain, for example, a valve metal such as aluminum, tantalum, or niobium, or may contain a noble metal such as gold, silver, or platinum, or may contain nickel. The second electrode 22 contains, for example, at least one selected from the group consisting of aluminum, tantalum, niobium, gold, silver, platinum, and nickel.

[0045] Capacitors 1a and 1b may be electrolytic capacitors. In this case, for example, an electrolyte 23 is disposed between first electrode 21 and second electrode 22. Alternatively, electrolyte 23 may be disposed between dielectric 10 and second electrode 22. Fig. 2B shows a modified example of capacitor 1b configured as an electrolytic capacitor. In capacitor 1b, electrolyte 23 is disposed so as to fill voids around the porous portion of first electrode 21, for example.

[0046] The electrolyte includes, for example, at least one selected from the group consisting of an electrolytic solution and a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof. The electrolyte may be a manganese compound such as manganese oxide. The electrolyte may include a solid electrolyte.

[0047] An electrolyte containing a conductive polymer can be formed by chemically polymerizing, electrolytically polymerizing, or both chemically and electrolytically polymerizing a raw material monomer on the dielectric 10. An electrolyte containing a conductive polymer may also be formed by depositing a solution or dispersion of the conductive polymer on the dielectric 10.

[0048] FIG. 3A is a diagram schematically illustrating an electric circuit 3 according to an embodiment of the present disclosure. As shown in FIG. 3A, the electric circuit 3 includes a capacitor 1a. The electric circuit 3 is not limited to a specific circuit as long as it includes the capacitor 1a. The electric circuit 3 may be an active circuit or a passive circuit. The electric circuit 3 may be a discharge circuit, a smoothing circuit, a decoupling circuit, or a coupling circuit. Since the electric circuit 3 includes the capacitor 1a, the electric circuit 3 is likely to have desired characteristics. For example, the capacitor 1a easily reduces noise in the electric circuit 3. The electric circuit 3 may also include a capacitor 1b instead of the capacitor 1a.

[0049] FIG. 3B is a diagram schematically illustrating a circuit board 5 according to an embodiment of the present disclosure. As shown in FIG. 3B, the circuit board 5 includes a capacitor 1a. The circuit board 5 is not limited to a specific circuit board as long as it includes the capacitor 1a. The circuit board 5 includes, for example, an electric circuit 3. The circuit board 5 may be an embedded board or a motherboard. The circuit board 5 may include a capacitor 1b instead of the capacitor 1a.

[0050] FIG. 3C is a diagram schematically illustrating a device 7 according to an embodiment of the present disclosure. As shown in FIG. 3C, the device 7 includes a capacitor 1a. The device 7 is not limited to a specific device as long as it includes the capacitor 1a. The device 7 includes, for example, a circuit board 5. The device 7 may be an electronic device, a communication device, a signal processing device, or a power supply device. The device 7 may be a server, an AC adapter, an accelerator, or a flat panel display such as a liquid crystal display (LCD). The device 7 may be a USB charger, a solid-state drive (SSD), an information terminal such as a PC, a smartphone, or a tablet PC, or an Ethernet switch. [Example]

[0051] The present disclosure will be described in more detail below with reference to examples. Note that the following examples are merely illustrative and the present disclosure is not limited to the following examples.

[0052] (Sample preparation) Sputtering was performed using Ti and Pt targets to form a lower electrode, a laminate of Ti and Pt thin films, on the substrate. The Ti thin film was in contact with the substrate. Corning EAGLE XG alkali-free glass was used as the substrate. During sputtering, the substrate environment was maintained at a pressure of 0.3 Pa, with argon gas occupying 100% of the volume. In addition, the substrate temperature was adjusted to 600°C.

[0053] Next, a dielectric film for each sample was formed on the bottom electrode by co-sputtering using Al2O3 and CeO2 targets. The co-sputtering conditions were adjusted to achieve a dielectric film thickness of 100 nm. During co-sputtering, the substrate environment was maintained at a pressure of 0.3 Pa, with argon gas accounting for 90% by volume and oxygen gas accounting for 10% by volume. In addition, the substrate was not heated. The Al and Ce composition ratio for each sample was adjusted by adjusting the film formation time by opening and closing a shutter. This resulted in the dielectric films for Samples 1 to 9. Next, sputtering was performed using Pt as the target to form a top electrode made of Pt with a diameter of 104 μm and a thickness of 100 nm on the dielectric film. In this manner, Samples 1 to 9 were obtained.

[0054] (Identifying the composition) Before forming the top electrode, X-ray fluorescence analysis was performed on the dielectric film of each sample using a Rigaku ZSX Primus IV X-ray fluorescence analyzer, and quantitative analysis of the elements in the dielectric film of each sample was performed. The fundamental parameter method (FP method) was used as the quantitative analysis method. From the results of the quantitative analysis, the ratio of the number of Ce atoms to the number of Al and Ce atoms in the dielectric film of each sample, Ce / (Al+Ce), was determined. The results are shown in Table 1.

[0055] (Check for the presence or absence of crystalline phases) Before forming the upper electrode, X-ray diffraction measurements were performed on the dielectric films of each sample using a Bruker D8 Discover X-ray diffractometer to obtain XRD patterns by 2θ / θ scan for each dielectric film. Figure 6 shows the XRD patterns of the dielectric films of Samples 1 to 4. Figure 7 shows the XRD patterns of the dielectric films of Samples 5 and 6. Figure 8 shows the XRD patterns of the dielectric films of Samples 7 to 11. In Figures 6, 7, and 8, the vertical axis represents the diffraction intensity in arbitrary units, and the horizontal axis represents the diffraction angle. In Figures 6, 7, and 8, a scale indicating zero diffraction intensity is provided at the boundary between two adjacent XRD patterns along the vertical axis. For the measurements, Cu-Kα radiation was used as the X-ray source, and the voltage was adjusted to 50 kV and the current to 100 mA. Measurements were performed using a two-dimensional detector and converted to 2θ.

[0056] (Dielectric properties) The dielectric constant ε and dielectric loss tangent tanδ of the dielectric film of each sample were measured at 10 kHz and 1 MHz using an LCR meter. The dielectric constant was determined by measuring the capacitance of each sample and based on the measured capacitance, the thickness of the dielectric film, and the electrode area. The ambient temperature during the measurements was 25°C. The results are shown in Table 1. Figure 4 shows the relationship between the dielectric constant of the dielectric film and the ratio of the number of Ce atoms to the number of Al and Ce atoms. In Figure 4, the vertical axis shows the dielectric constant of the dielectric film, and the horizontal axis shows the ratio of the number of Ce atoms to the number of Al and Ce atoms. Figure 5 shows the relationship between the dielectric loss tangent of the dielectric film and the ratio of the number of Ce atoms to the number of Al and Ce atoms. In Figure 5, the vertical axis shows the dielectric loss tangent of the dielectric film, and the horizontal axis shows the ratio of the number of Ce atoms to the number of Al and Ce atoms.

[0057] As shown in Table 1 and Fig. 4, the dielectric films of Samples 1 to 4, in which the atomic ratio Ce / (Al+Ce) is 0.400 or more and less than 0.900, have a relative permittivity exceeding 15.0 at frequencies of 10 kHz and 1 MHz. In addition, Table 1 and Fig. 5 show that the dielectric loss tangents of the dielectric films of Samples 1 to 4 at frequencies of 10 kHz and 1 MHz are as low as less than 0.020. This suggests that a dielectric containing a composite oxide having Al and Ce, in which the atomic ratio Ce / (Al+Ce) is adjusted to 0.400 or more and less than 0.900, satisfies both a high relative permittivity and a low dielectric loss tangent.

[0058] Figure 6 shows the X-ray diffraction (XRD) patterns of the dielectric films of Samples 1 to 4. As shown in Figure 6, no peaks having a half-width of 5° or less and clear against the background were observed in the XRD patterns of the dielectric films of Samples 1 to 4, and it can be determined that the compounds contained in the dielectric films are amorphous. This suggests that the dielectrics containing the above complex oxides are amorphous, allowing the dielectrics to satisfy both a high relative dielectric constant and a low dielectric loss tangent.

[0059] As shown in Table 1 and FIG. 4, the dielectric films of Samples 5 and 6, in which the atomic ratio Ce / (Al+Ce) was less than 0.300, had dielectric constants less than 15 at frequencies of 10 kHz and 1 MHz. On the other hand, as shown in Table 1 and FIG. 5, the dielectric loss tangents of Samples 5 and 6 at frequencies of 10 kHz and 1 MHz were very low, less than 0.020. Therefore, it is difficult to say that a dielectric containing a composite oxide in which the atomic ratio Ce / (Al+Ce) was adjusted to less than 0.300 satisfies both a high dielectric constant and a low dielectric loss tangent. Furthermore, as shown in FIG. 7, the XRD patterns of the dielectric films of Samples 5 and 6 did not show any peaks with a half-width of 5° or less that were distinct from the background, indicating that the compounds contained in the dielectric films were amorphous.

[0060] As shown in Table 1 and FIG. 4, the dielectric films of Samples 7 to 11, which have an atomic ratio Ce / (Al+Ce) of 0.900 or more, have high dielectric constants of 14 or more at frequencies of 10 kHz and 1 MHz. On the other hand, as shown in Table 1 and FIG. 5, the dielectric films of Samples 7 to 11 have high dielectric loss tangents of 0.1 or more at frequencies of 10 kHz and 1 MHz. Therefore, it is difficult to say that a dielectric containing a complex oxide with an atomic ratio Ce / (Al+Ce) adjusted to 0.900 or more satisfies both a high dielectric constant and a low dielectric loss tangent. Furthermore, as shown in FIG. 8, the XRD patterns of the dielectric films of Samples 7 to 11 do not show any peaks with a half-width of 5° or less that are distinct from the background, indicating that the compounds contained in the dielectric films are amorphous.

[0061] [Table 1] [Industrial Applicability]

[0062] The dielectric material of the present disclosure can be suitably used in electronic components such as electrolytic capacitors.

Claims

1. A dielectric disposed on a first electrode comprising a valve metal, a noble metal, or nickel, Ce x Al 1-x O k The composite oxide has a composition represented by the formula: In the composition, the condition of 0.400≦x<0.900 is satisfied, and k is a value that maintains the electrical neutrality of the composite oxide. Dielectric.

2. The dielectric of claim 1 , wherein the dielectric comprises a sputtered film.

3. The dielectric according to claim 1 or 2, wherein the dielectric is for a capacitor.

4. The first electrode; The dielectric material according to claim 1 , disposed on the first electrode; and a second electrode covering at least a portion of the dielectric; Capacitor.

5. The capacitor of claim 4 , wherein at least a portion of the first electrode is porous.

6. The capacitor of claim 4 or 5, wherein the first electrode comprises a valve metal.

7. 7. The capacitor of claim 6, wherein the valve metal includes at least one selected from the group consisting of aluminum, tantalum, and niobium.

8. The capacitor according to claim 4 , wherein the second electrode contains at least one selected from the group consisting of aluminum, tantalum, niobium, gold, silver, platinum, and nickel.

9. further comprising an electrolyte in contact with the second electrode; the electrolyte is filled inside the porous material and includes at least one selected from the group consisting of an electrolytic solution, a conductive polymer, and manganese oxide; The capacitor according to claim 5 .

10. An electric circuit comprising the capacitor according to any one of claims 4 to 9.

11. A circuit board comprising the capacitor according to any one of claims 4 to 9.

12. An apparatus comprising the capacitor according to any one of claims 4 to 9.

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