Dielectric medium, capacitor, circuit, circuit board, device, and power storage device

Abstract

The dielectric (10) has a composition represented by Bi2xMgyTizOk. The composition satisfies the conditions x > = 0.15, y < = 0.40, z > = 0.25, and x + y + z = 1.0. In this composition, k is a value for maintaining electrical neutrality.

Description

Technical Field

[0001] The present disclosure relates to a dielectric, a capacitor, a circuit, a circuit substrate, a device, and an electric storage device. Background Art

[0002] Conventionally, capacitors using ceramics are known. For example, Patent Document 1 describes a multilayer ceramic capacitor including a dielectric ceramic layer containing an oxide containing Ba, Ca, and Ti.

[0003] Patent Document 2 describes a dielectric composition containing at least Bi, Na, Sr and Ti and having a perovskite-type crystal structure. The dielectric composition contains specific particles having a core-shell structure having at least one core portion containing SrTiO3. The dielectric composition can form a dielectric layer of a laminated ceramic capacitor.

[0004] Patent Document 3 describes a capacitor having an insulating structure including a polymer layer and a composite layer. The composite layer is disposed on the polymer layer and includes a thermoplastic polymer containing at least one inorganic component. The capacitor can be used for power conversion at high energy density.

[0005] Non-patent document 1 describes a perovskite Bi(Mg 0.5 Ti x )O3 thin film. In the thin film, x is 0.50 to 0.85.

[0006] Non-patent document 2 describes a BiMg y Ti 0.5 O3 film. In this film, y is 0.50 to 0.62.

[0007] Prior Art Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2000-058378

[0009] Patent Document 2: Japanese Patent Application No. 2018-531858

[0010] Patent Document 3: Japanese Patent Application Publication No. 2010-278430

[0011] Non-patent literature 1: Journal of Materials Chemistry C, 2019, vol. 7, p. 13632-13639

[0012] Non-patent document 2: Journal of the European Ceramic Society, 2020, vol. 40, p. 1243-1249 Summary of the invention

[0013] Problems to be solved by the invention

[0014] From the perspective of increasing the capacitance of a capacitor under conditions of high electric field strength, the technology described in the above document has room for further research. Therefore, the present disclosure provides a new dielectric that is advantageous from the perspective of increasing the capacitance of a capacitor under conditions of high electric field strength.

[0015] Means for solving problems

[0016] The dielectric of the present disclosure has a 2x Mg y Ti z O k The composition of the representation,

[0017] The composition satisfies the conditions of x≥0.15, y≤0.40, z≥0.25 and x+y+z=1.0,

[0018] In the above composition, k is a value for maintaining electrical neutrality.

[0019] Effects of the Invention

[0020] According to the present disclosure, it is possible to provide a new dielectric material which is advantageous from the viewpoint of increasing the capacitance of a capacitor under conditions of high electric field intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a cross-sectional view showing an example of the capacitor of the present disclosure.

[0022] Figure 2 is a cross-sectional view showing another example of the capacitor of the present disclosure.

[0023] Figure 3A Schematic diagram of an example of a circuit of the present disclosure.

[0024] Figure 3B This is a diagram schematically showing an example of the circuit board of the present disclosure.

[0025] Figure 3C This is a diagram schematically showing an example of the device disclosed in the present invention.

[0026] Figure 3D It is a diagram schematically showing an example of the power storage device of the present disclosure.

[0027] Figure 4 These are X-ray diffraction (XRD) patterns of the dielectric films of Examples 1 to 5.

[0028] Figure 5These are XRD patterns of the dielectric films of Comparative Examples 2 to 7. DETAILED DESCRIPTION

[0029] (Insights that form the basis of this disclosure)

[0030] In recent years, as devices have become smaller and their operating voltages have increased, electronic components used in circuits have also been required to be smaller and their operating voltages have increased. For example, if a small capacitor that can exert high capacitance under conditions of high electric field strength can be provided, it is believed that this can contribute to the miniaturization of devices and the increase in operating voltages.

[0031] Barium titanate and its derivatives have been used as dielectrics in capacitors. For example, multilayer ceramic capacitors have been widely used. Since the capacity of capacitors of the same shape is proportional to the relative dielectric constant of the dielectric, increasing the relative dielectric constant of the dielectric is related to the miniaturization and high capacity of the capacitor. For example, a multilayer ceramic capacitor with a high dielectric constant can have a very high relative dielectric constant of more than 1000.

[0032] According to patent document 1, a dielectric based on barium titanate and with a predetermined amount of a specific oxide added has a relative dielectric constant of more than 1000 without applying a DC voltage. In addition, in the laminated ceramic capacitor described in patent document 1, it is known that the rate of change of capacity when a DC voltage is applied at an electric field strength of 5 kV / mm is reduced. Regarding the dielectric composition described in patent document 2, it is known that it has a relative dielectric constant of more than 1000 without applying a DC voltage. In addition, in the dielectric composition described in patent document 2, it is known that the rate of change of the electrostatic capacitance before and after applying a DC bias of 5 V / μm is small.

[0033] On the other hand, for example, a buffer capacitor or a smoothing capacitor in a vehicle-mounted converter or a vehicle-mounted inverter may be applied with a high DC voltage of several hundred volts. In order to achieve miniaturization of a capacitor that is expected to be used under a condition where a high DC voltage is applied, it is considered important to increase the capacitance of the capacitor under an electric field intensity higher than the electric field intensity in the evaluation of the capacitance change rate in Patent Documents 1 and 2.

[0034] The insulating structure of the capacitor described in Patent Document 3 has a dielectric constant in the range of about 3 to 100 and an insulation resistance of about 150 kV / mm. Although the insulating structure has a high insulation resistance, the relative dielectric constant of the insulating structure is not that high because it contains a polymer layer. In addition, in Patent Document 3, the relative dielectric constant of the insulating structure under high electric field strength near the insulation resistance is not evaluated.

[0035] According to the records in non-patent documents 1 and 2, although the saturation polarization density is reduced by adding an excess of titanium or magnesium in the synthesis of magnesium bismuth titanate, the dielectric withstand voltage is increased and the capacity of the material is increased. On the other hand, in non-patent documents 1 and 2, there is no study on the performance of Bi(Mg) at high electric field strength. 0.5 Ti x )O3 thin film and BiMg y Ti 0.5 The relative dielectric constant of the O3 film was evaluated.

[0036] In view of such a situation, the inventors have repeatedly conducted in-depth research to develop a new dielectric that is advantageous from the perspective of increasing the capacitance of a capacitor under conditions of high electric field strength. After a large number of repeated experiments, the inventors have gained new insights into the relationship between the contents of Bi, Mg and Ti in oxides containing Bi, Mg and Ti and the characteristics of dielectrics under high electric field strength. Based on this new insight, the inventors have proposed the dielectric disclosed herein.

[0037] (Summary of a technical solution involved in the present disclosure)

[0038] The dielectric of the first technical solution of the present disclosure has a Bi 2x Mg y Ti z O k The composition of the representation,

[0039] The composition satisfies the conditions of x≥0.15, y≤0.40, z≥0.25 and x+y+z=1.0,

[0040] In the above composition, k is a value for maintaining electrical neutrality.

[0041] According to the first technical solution, the relative dielectric constant of the dielectric under the condition of high electric field strength is likely to be high. Therefore, the dielectric is advantageous from the viewpoint of increasing the capacitance of the capacitor under the condition of high electric field strength.

[0042] In the second technical solution of the present disclosure, for example, the dielectric of the first technical solution may contain crystalline Bi2Ti2O7. According to the second technical solution, the relative dielectric constant of the dielectric under the condition of high electric field strength is easy to become higher. This is advantageous from the viewpoint of increasing the capacitance of the capacitor under the condition of high electric field strength.

[0043] In the third technical solution of the present disclosure, for example, the dielectric of the first technical solution or the second technical solution may contain a crystalline Bi4Ti3O 12 , crystalline γ-Bi2O3 and crystalline Bi(Mg 0.5 Ti 0.5)O3. According to the third technical solution, the relative dielectric constant of the dielectric under the condition of high electric field strength is easy to become higher. Therefore, the dielectric is more advantageous from the viewpoint of increasing the capacity of the capacitor under the condition of high electric field strength.

[0044] In the fourth technical solution of the present disclosure, for example, the dielectric in any one of the first technical solution to the third technical solution may contain a crystalline Bi4Ti3O 12 and crystalline γ-Bi2O3. According to the fourth technical solution, the relative dielectric constant of the dielectric under the condition of high electric field strength is easy to become higher. Therefore, the dielectric is more advantageous from the perspective of increasing the capacitance of the capacitor under the condition of high electric field strength.

[0045] In the fifth technical solution of the present disclosure, for example, the dielectric of any one of the first to third technical solutions may contain crystalline γ-Bi2O3. According to the fifth technical solution, the relative dielectric constant of the dielectric under the condition of high electric field strength is easy to become higher. Therefore, the dielectric is more advantageous from the viewpoint of increasing the capacitance of the capacitor under the condition of high electric field strength.

[0046] In the sixth technical solution of the present disclosure, for example, the dielectric of any one of the first to fifth technical solutions may have a relative dielectric constant greater than 138 when the electric field strength is increased at an electric field strength of 0.5 MV / cm. In addition, the dielectric may have a relative dielectric constant greater than 100 when the electric field strength is reduced at an electric field strength of 0.5 MV / cm. According to the sixth technical solution, the dielectric is more advantageous from the viewpoint of increasing the capacitance of the capacitor under conditions of high electric field strength.

[0047] In the seventh technical solution of the present disclosure, for example, the dielectric of any one of the first to sixth technical solutions may have a relative dielectric constant greater than 138 at an electric field strength of 0.7 MV / cm when the electric field strength is increased. In addition, the dielectric may have a relative dielectric constant greater than 57 at an electric field strength of 0.7 MV / cm when the electric field strength is reduced. According to the seventh technical solution, the dielectric is more advantageous from the viewpoint of increasing the capacitance of the capacitor under conditions of high electric field strength.

[0048] In the eighth technical solution of the present disclosure, for example, the dielectric of any one of the first to seventh technical solutions can form at least one film selected from a pulsed laser deposited film, a vacuum evaporated film, a sputtered film, an atomic layer deposited film, a chemical vapor growth film, and an anodized film. According to the eighth technical solution, since the dielectric can exist as a film such as a pulsed laser deposited film, it is advantageous from the viewpoint of increasing the capacitance of the capacitor.

[0049] In the ninth aspect of the present disclosure, for example, the dielectric of any one of the first to eighth aspects can be used for a capacitor. According to the ninth aspect, a dielectric can be used to increase the capacitance of a capacitor under conditions of high electric field strength.

[0050] The capacitor according to the tenth technical solution of the present disclosure comprises:

[0051] a first electrode;

[0052] The dielectric of any one of the first to ninth technical solutions arranged on the first electrode; and

[0053] A second electrode covers at least a portion of the dielectric.

[0054] According to the tenth technical solution, the capacitance of the capacitor tends to increase under conditions of high electric field strength.

[0055] The circuit according to the 11th technical solution of the present disclosure comprises the capacitor according to the 10th technical solution. According to the 11th technical solution, when the capacitor is used under the condition of high electric field intensity, the circuit can easily exhibit desired performance.

[0056] The circuit board according to the twelfth technical solution of the present disclosure comprises the capacitor according to the tenth technical solution. According to the twelfth technical solution, when the capacitor is used under the condition of high electric field intensity, the circuit board can easily exhibit the desired performance.

[0057] The circuit board according to the 13th technical solution of the present disclosure comprises the capacitor according to the 10th technical solution. According to the 13th technical solution, when the capacitor is used under the condition of high electric field intensity, the device can easily exhibit the desired performance.

[0058] The electric storage device according to the 14th technical solution of the present disclosure includes the capacitor according to the 10th technical solution. According to the 14th technical solution, when the capacitor is used under the condition of high electric field intensity, the electric storage device can easily exhibit the desired performance.

[0059] (Implementation Method)

[0060] Hereinafter, the embodiments of the present disclosure will be described with reference to the accompanying drawings. In addition, the embodiments described below all represent general or specific examples. Therefore, the numerical values, shapes, materials, constituent elements, configuration positions of constituent elements, and connection methods shown in the following embodiments are only examples, and their main purpose does not limit the present disclosure. In addition, among the constituent elements in the following embodiments, the constituent elements that are not recorded in the independent claims representing the highest-level concepts are described as arbitrary constituent elements. In addition, in the accompanying drawings, the description of the parts marked with the same symbols is sometimes omitted. In addition, for ease of understanding, the various constituent elements are schematically shown in the drawings, and sometimes the shapes and size ratios are not accurately represented.

[0061] Figure 1 is a cross-sectional view showing an example of a capacitor disclosed in the present invention. Figure 1 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 has a Bi 2x Mg y Ti z O k The composition represented by . The composition satisfies the conditions of x ≥ 0.15, y ≤ 0.40, z ≥ 0.25 and x + y + z = 1.0. In this composition, k is a value for maintaining electrical neutrality. According to such a technical configuration, the relative dielectric constant of the dielectric 10 under the condition of high electric field strength tends to become high. Therefore, the dielectric 10 is advantageous from the viewpoint of increasing the capacitance of the capacitor 1a under the condition of high electric field strength.

[0062] The dielectric 10 contains, for example, crystalline Bi2Ti2O7. According to such a technical configuration, the relative dielectric constant of the dielectric 10 under the condition of high electric field strength is easily increased, which is more advantageous from the viewpoint of increasing the capacitance of the capacitor 1a under the condition of high electric field strength.

[0063] When the dielectric material satisfies the above composition, the dielectric material does not necessarily contain crystalline Bi2Ti2O7. 0.5 Ti x )O3 thin film and BiMg described in Non-Patent Document 2 y Ti 0.5From the XRD patterns of the films of Bi2Ti2O7, it can be seen that these films do not contain crystalline Bi2Ti2O7. On the other hand, according to the research of the present inventors, even if the dielectric 10 contains crystalline Bi2Ti2O7, if the above-mentioned composition conditions are not satisfied, the relative dielectric constant of the dielectric 10 under the condition of high electric field strength is difficult to become higher. In the dielectric 10, by satisfying the above-mentioned composition conditions and containing crystalline Bi2Ti2O7, the relative dielectric constant of the dielectric 10 under the condition of high electric field strength is easy to become higher.

[0064] In the above composition, the condition of x≤0.65 may be satisfied, the condition of x≤0.60 may be satisfied, the condition of x≤0.55 may be satisfied, and the condition of x≤0.50 may be satisfied. In the above composition, the condition of x≤0.45 may be satisfied, and the condition of x≤0.40 may be satisfied. In the above composition, for example, the conditions of 0.15≤x≤0.65, 0.15≤x≤0.60, 0.15≤x≤0.55, 0.15≤x≤0.50, 0.15≤x≤0.45, or 0.15≤x≤0.40 are satisfied.

[0065] In the above composition, the condition of y≥0.05 may be satisfied, the condition of y≥0.10 may be satisfied, the condition of y≥0.15 may be satisfied, and the condition of y≥0.20 may be satisfied. In the above composition, for example, the condition of 0.05≤y≤0.40, 0.10≤y≤0.40, 0.15≤y≤0.40, or 0.20≤y≤0.40 is satisfied.

[0066] In the above composition, the condition of z≤0.80 may be satisfied, the condition of z≤0.75 may be satisfied, the condition of z≤0.70 may be satisfied, the condition of z≤0.65 may be satisfied, and the condition of z≤0.60 may be satisfied. In the above composition, for example, the conditions of 0.25≤z≤0.80, 0.25≤z≤0.75, 0.25≤z≤0.70, 0.25≤z≤0.65, or 0.25≤z≤0.60 are satisfied.

[0067] The dielectric 10 may contain only Bi2Ti2O7 as a crystalline oxide, or may contain a crystalline oxide other than Bi2Ti2O7. For example, the dielectric 10 may contain a crystalline oxide selected from Bi4Ti3O 12 , crystalline γ-Bi2O3 and crystalline Bi(Mg 0.5 Ti 0.5 )O3. In this case, the relative dielectric constant of the dielectric 10 under the condition of high electric field intensity is likely to become higher.

[0068] The dielectric 10 may contain a crystalline Bi4Ti3O 12and crystalline γ-Bi 2 O 3. In this case, the relative dielectric constant of the dielectric 10 under the condition of high electric field intensity is likely to be higher.

[0069] The dielectric 10 may contain crystalline γ-Bi 2 O 3. In this case, the relative dielectric constant of the dielectric 10 under the condition of high electric field intensity is likely to be higher.

[0070] For example, the dielectric 10 has a relative dielectric constant greater than 138 when the electric field strength is increased at an electric field strength of 0.5 MV / cm, and has a relative dielectric constant greater than 100 when the electric field strength is reduced. In this case, the dielectric 10 has a high relative dielectric constant at a high electric field strength of 0.5 MV / cm, and the capacitance of the capacitor 1a tends to increase under the condition of high electric field strength.

[0071] For example, the dielectric 10 may have a relative dielectric constant of 140 or more, 150 or more, or 160 or more, at an electric field strength of 0.5 MV / cm, when the electric field strength is increased. For example, the dielectric 10 may have a relative dielectric constant of 110 or more, 115 or more, or 120 or more, at an electric field strength of 0.5 MV / cm, when the electric field strength is decreased. The dielectric 10 may have a relative dielectric constant of 2000 or less, 1500 or less, or 1000 or less, at an electric field strength of 0.5 MV / cm, when the electric field strength is increased and when the electric field strength is decreased. The dielectric 10 has a relative dielectric constant of, for example, greater than 138 and less than 2000, less than 1500, or less than 1000 at an electric field strength of 0.5 MV / cm when the electric field strength is increased. The dielectric 10 has a relative dielectric constant of, for example, greater than 100 and less than 2000, less than 1500, or less than 1000 at an electric field strength of 0.5 MV / cm when the electric field strength is reduced.

[0072] For example, at an electric field strength of 0.7 MV / cm, the dielectric 10 has a relative dielectric constant greater than 138 when the electric field strength is increased, and has a relative dielectric constant greater than 57 when the electric field strength is reduced. In this case, at a high electric field strength of 0.7 MV / cm, the dielectric 10 has a high relative dielectric constant, and under the condition of high electric field strength, the capacitance of the capacitor 1a tends to increase.

[0073] For example, the dielectric 10 may have a relative dielectric constant of 140 or more, 150 or more, or 160 or more, at an electric field strength of 0.7 MV / cm, when the electric field strength is increased. For example, the dielectric 10 may have a relative dielectric constant of 60 or more, 80 or more, or 100 or more, at an electric field strength of 0.7 MV / cm, when the electric field strength is decreased. The dielectric 10 may have a relative dielectric constant of 2000 or less, 1500 or less, or 1000 or less, at an electric field strength of 0.7 MV / cm, when the electric field strength is increased and when the electric field strength is decreased. The dielectric 10 has a relative dielectric constant of, for example, greater than 138 and less than 2000, less than 1500, or less than 1000 at an electric field strength of 0.7 MV / cm when the electric field strength is increased. The dielectric 10 has a relative dielectric constant of, for example, greater than 57 and less than 2000, less than 1500, or less than 1000 at an electric field strength of 0.7 MV / cm when the electric field strength is reduced.

[0074] The shape of the dielectric 10 is not limited to a specific shape. The dielectric 10 is formed into a film, for example. The method of forming the film is not limited to a specific method. The film can be formed, for example, by a vapor deposition method, or by an anodizing process. The dielectric 10 is, for example, at least one film selected from a pulsed laser deposition (PLD) film, a vacuum evaporation film, a sputtering film, an atomic layer deposition (ALD) film, a chemical vapor growth (CVD) film, and an anodized film. In this case, the relative dielectric constant of the dielectric 10 under conditions of high electric field strength tends to become higher. In addition, Bi 2x Mg y Ti z O k The values ​​of x, y and z in the composition can be easily adjusted to the desired range.

[0075] like Figure 1 As shown, capacitor 1a includes first electrode 21, dielectric 10, and second electrode 22. Dielectric 10 is disposed on first electrode 21. Second electrode 22 covers at least a portion of dielectric 10. Since capacitor 1a includes dielectric 10, it is easy to exhibit high capacitance under conditions of high electric field strength.

[0076] Figure 2 is a cross-sectional view showing another example of the capacitor of the present disclosure. Figure 2The capacitor 1b shown is constructed similarly to the capacitor 1a except for the parts specifically described. The components of the capacitor 1b that are identical or corresponding to the components of the capacitor 1a are marked with the same symbols, and detailed descriptions are omitted. The descriptions of the capacitor 1a are also applicable to the capacitor 1b as long as there is no technical contradiction.

[0077] like Figure 2 As shown, in the capacitor 1b, at least a portion of the first electrode 21 is porous. According to such a technical structure, the surface area of ​​the first electrode 21 is easy to increase, and the electrostatic capacitance of the capacitor 1b is easy to increase. Such a porous structure can be formed by, for example, etching of metal foil and sintering of powder.

[0078] like Figure 2 As shown, for example, a film of the dielectric 10 is formed on the surface of the porous portion of the first electrode 21. In this case, as a method for forming the film of the dielectric 10, an atomic layer deposition method (ALD method) or a chemical vapor method such as a CVD method and a spray CVD method can be used.

[0079] The first electrode 21 includes, for example, a valve metal such as Al, Ta, Nb, Zr, Hf, and Bi. The second electrode 22 may include, for example, a silver-containing paste solidified material, a carbon material such as graphite, or both of the solidified material and the carbon material.

[0080] Capacitors 1a and 1b may be electrolytic capacitors. In this case, for example, an electrolyte 23 is disposed between the first electrode 21 and the second electrode 22. The electrolyte 23 may also be disposed between the dielectric 10 and the second electrode 22. In capacitor 1b, the electrolyte 23 is disposed so as to fill the gaps around the porous portion of the first electrode 21, for example.

[0081] The electrolyte 23 includes, for example, at least one selected from manganese oxide, an electrolyte solution, and a conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and derivatives thereof. The electrolyte 23 may be a manganese compound such as manganese oxide. The electrolyte 23 may include a solid electrolyte.

[0082] For example, a circuit including the capacitor 1a or 1b may be provided. Figure 3A An example of the circuit of the present disclosure is schematically shown. Circuit 3 includes capacitor 1a. Circuit 3 may be an active circuit or a passive circuit. Circuit 3 may be a discharge circuit, a smoothing circuit, a decoupling circuit, or a coupling circuit. Since circuit 3 includes capacitor 1a, when capacitor 1a is used under conditions of high electric field strength, circuit 3 is likely to exhibit the desired performance. Circuit 3 may also include capacitor 1b.

[0083] For example, a circuit board including the capacitor 1a or 1b can be provided. Figure 3B An example of a circuit substrate of the present disclosure is schematically shown. Figure 3B As shown, the circuit board 5 includes a capacitor 1a. For example, a circuit including the capacitor 1a is formed in the circuit board 5. Since the circuit board 5 includes the capacitor 1a, when the capacitor 1a is used under the condition of high electric field strength, the circuit board 5 can easily exert the desired performance. The circuit board 5 may also include a capacitor 1b.

[0084] For example, a device including the capacitor 1a or 1b can be provided. Figure 3C An example of a machine of the present disclosure is schematically shown. Figure 3C As shown, the machine 7 has a capacitor 1a. The machine 7, for example, has a circuit substrate 5 including the capacitor 1a. Since the machine 7 has the capacitor 1a, when the capacitor 1a is used under conditions of high electric field strength, the machine 7 can easily exert the desired performance. The machine 7 may also have a capacitor 1b. The machine 7 may be an electronic machine, a communication machine, a signal processing device, a power supply device, an inverter, or a converter. The machine 7 may be a server, an AC adapter, an accelerator, or a flat panel display such as a liquid crystal display device (LCD). The machine 7 may be a USB charger, a solid state drive (SSD), an information terminal such as a PC, a smartphone, and a tablet PC, or an Ethernet switch.

[0085] For example, it is possible to provide an electric storage device including the capacitor 1 a or 1 b . Figure 3D Schematically shows an example of the power storage device of the present disclosure. Figure 3D As shown in FIG. 1 , the power storage device 9 includes a capacitor 1a. Therefore, when the capacitor 1a is used under conditions of high electric field strength, the power storage device 9 can easily exert the desired performance. The power storage device 9 may also include a capacitor 1b. Figure 3D As shown, for example, the power storage device 9 can be used to provide the power storage system 50. The power storage system 50 includes the power storage device 9 and the power generation device 2. In the power storage system 50, the electricity obtained by the power generation in the power generation device 2 is stored in the power storage device 9. The power generation device 2 is, for example, a device for solar power generation or wind power generation. The power storage device 9 includes, for example, a secondary battery such as a lithium ion battery and a lead storage battery.

[0086] Example

[0087] Hereinafter, the present disclosure will be described in more detail based on examples, but the present disclosure is not limited to the following examples.

[0088] (Examples 1 to 5 and Comparative Examples 2 to 7)

[0089] A Pt thin film was formed on an Al2O3 (0001) substrate by sputtering using Pt as a target to obtain a lower electrode. The Pt thin film was in contact with the substrate. During sputtering, the environment of the substrate was maintained under the condition of 0.3 Pa with argon accounting for 100% by volume. In addition, the temperature of the substrate was adjusted to 500°C.

[0090] PLD films of samples of Examples 1 to 5 and Comparative Examples 2 to 7 were formed on the lower electrode by the PLD method using Bi2O3, MgO and TiO2 as targets. The conditions of the PLD method were adjusted so that the thickness of the PLD film was 100 nm. In the PLD, the environment of the substrate was maintained at a pressure of 0.01 Pa with 100% by volume of oxygen, and the substrate was not heated. The composition ratio of Bi, Mg and Ti in the dielectric film of each sample was adjusted by adjusting the film formation time accompanied by the opening and closing of the gate. Then, the PLD film was heat-treated at 640°C for 2 minutes in an environment of 80% by volume of argon and 20% by volume of oxygen using the atmosphere variable lamp annealing device VHC-P616C manufactured by Advance Technology Co., Ltd. In this way, the dielectric films of Examples 1 to 5 and Comparative Examples 2 to 7 were obtained. Next, a Pt thin film having a diameter of 100 μm and a thickness of 100 nm was formed on the dielectric film by sputtering using Pt as a target, thereby obtaining an upper electrode. In this way, samples of Examples 1 to 5 and Comparative Examples 2 to 7 were obtained.

[0091] (Determination of composition)

[0092] Using the fluorescent X-ray analysis device micro EDX-1400 manufactured by Shimadzu Corporation, fluorescent X-ray analysis was performed on the dielectric film of each sample before forming the upper electrode, and quantitative analysis of the elements in each dielectric film was performed. The method of quantitative analysis adopted the basic parameter method (FP method). According to the results of the quantitative analysis, the atomic ratio of Bi, Mg and Ti in the dielectric film of each sample was determined. The results are shown in Table 1. In Table 1, x is the half value of the number of atoms of Bi / (half value of the number of atoms of Bi + the number of atoms of Mg + the number of atoms of Ti). y is the number of atoms of Mg / (half value of the number of atoms of Bi + the number of atoms of Mg + the number of atoms of Ti). z is the number of atoms of Ti / (half value of the number of atoms of Bi + the number of atoms of Mg + the number of atoms of Ti).

[0093] (Evaluation of Crystalline Phase)

[0094] Before forming the upper electrode, the dielectric film of each sample was subjected to X-ray diffraction measurement using an X-ray diffraction apparatus D8 Discover manufactured by Bruker Corporation, and a 2θ / θ scanning XRD pattern of each dielectric film was obtained. Figure 4 XRD patterns of the dielectric films of the samples of Examples 1 to 5 are shown. Figure 5The XRD patterns of the dielectric films of the samples of Comparative Examples 2 to 7 are shown. Figure 4 and Figure 5 In the figure, the vertical axis represents the diffraction intensity in arbitrary units on a logarithmic scale (scale), and the horizontal axis represents the diffraction angle 2θ. Figure 4 and Figure 5 In the figure, the vertical axis represents the relative relationship of the diffraction intensity in one XRD pattern, and does not represent the relative relationship of the diffraction intensity in different XRD patterns. In this measurement, Cu-Kα line is used as the X-ray source, the voltage is adjusted to 50 kV, and the current is adjusted to 100 mA. The measurement is performed using a two-dimensional detector and converted to 2θ.

[0095] (Dielectric properties)

[0096] The electric field intensity dependence of the polarization density of the dielectric film of each sample at a frequency of 10kHz was measured using a ferroelectric tester Precision Premier II manufactured by RADIANT TECHNOLOGIES. Inc. The relative dielectric constant at a specific electric field intensity is calculated based on the differential capacitance (the change in polarization density per unit change in electric field intensity) at the electric field intensity, based on the thickness of the dielectric film and the value of the electrode area. The ambient temperature during the measurement was 25°C. The results are shown in Table 1. In addition, in Table 1, the mark "OL" indicates that insulation breakdown has occurred and the relative dielectric constant cannot be calculated.

[0097] In order to serve as a benchmark for the evaluation of the relative dielectric constant, a barium titanate-based laminated ceramic capacitor was prepared as Comparative Example 1. The laminated ceramic capacitor is model GRM188D71A106MA73D manufactured by Murata Manufacturing Co., Ltd. In this laminated ceramic capacitor, the capacity is 10μF, the withstand voltage is 10V, and the size is 1.6×0.8×0.8mm. Using the above-mentioned ferroelectric tester, the electric field intensity dependence of the polarization density at a frequency of 10kHz was measured within the withstand voltage range. Using a scanning electron microscope (SEM), the cross-section of the laminated ceramic capacitor of Comparative Example 1 was observed, the thickness of the dielectric and the surface area of ​​the electrode were determined, and the relative dielectric constant of the dielectric of the laminated ceramic capacitor of Comparative Example 1 was calculated according to the same steps as above. The results are shown in Table 1.

[0098] The relative dielectric constant of the laminated ceramic capacitor of Comparative Example 1 at an electric field strength of 0.5MV / cm is 138 and 100, respectively, when the voltage is increased and when the voltage is decreased. By increasing the voltage, the electric field strength increases. By reducing the voltage, the electric field strength decreases. The relative dielectric constant of the laminated ceramic capacitor of Comparative Example 1 at an electric field strength of 0.7MV / cm is 138 and 57, respectively, when the voltage is increased and when the voltage is decreased. The evaluation of the relative dielectric constant of the dielectric of the capacitor under high voltage conditions is mostly carried out under the condition of an electric field strength of about tens of kV / cm. On the other hand, in order to achieve the miniaturization of capacitors that can apply hundreds of volts of DC voltage, such as capacitors used in vehicle-mounted converters or vehicle-mounted inverters, it is considered insufficient to evaluate the relative dielectric constant of the dielectric under this electric field strength. Therefore, considering the withstand voltage of the multilayer ceramic capacitor of Comparative Example 1, the relative dielectric constant of the dielectric at an electric field strength of about 10 times greater than the electric field strength of about several tens of kV / cm, such as 0.5 MV / cm and 0.7 MV / cm, was evaluated as described above.

[0099] As shown in Table 1, the relative dielectric constants of the dielectric films of the samples of Examples 1 to 5 at 0.5 MV / cm exceeded 138 when the voltage was increased, and exceeded 100 when the voltage was decreased. In addition, the relative dielectric constants of the dielectric films of the samples of Examples 1 to 5 at 0.7 MV / cm exceeded 138 when the voltage was increased, and exceeded 57 when the voltage was decreased. On the other hand, the relative dielectric constants of the dielectric films of the samples of Comparative Examples 2 to 7 satisfied at least one of the following conditions (i), (ii), (iii), and (iv).

[0100] (i) The relative dielectric constant at 0.5 MV / cm is 138 or less when the voltage is increased.

[0101] (ii) The relative dielectric constant at 0.5 MV / cm is 100 or less when the voltage is reduced.

[0102] (iii) The relative dielectric constant at 0.7 MV / cm is 138 or less when the voltage is increased.

[0103] (iv) The relative dielectric constant at 0.7 MV / cm is 57 or less when the voltage is reduced.

[0104] like Figure 4 and Figure 5As shown, in the XRD patterns of the dielectric films of the samples of Examples 1 to 5 and Comparative Examples 2 to 7, peaks were observed near 14.8°, 16.5°, 21.8°, 22.3°, 28.0°, 29.9°, 30.3°, 31.8°, 32.8°, 34.5°, 46.2°, 50.0°, 52.3°, 55.8°, 56.5°, 57.8°, 61.9°, 62.3°, and 63.5°. Among them, the peaks at 14.8°, 29.9°, 34.5°, 50.0°, 57.8°, and 62.3° are attributed to Bi2Ti2O7. The peaks near 16.5°, 21.8°, 61.9°, and 63.5° are attributed to Bi4Ti3O 12 The peaks at 28.0°, 30.3° and 32.8° are attributed to γ-Bi2O3. The peaks at 22.3°, 31.8°, 46.2° and 56.5° are attributed to Bi(Mg 0.5 Ti 0.5 )O3. In addition, the peaks near 52.3° and 55.8° are attributed to at least one selected from Bi2Ti2O7 and γ-Bi2O3. Peaks are also observed near 39.8° and 41.7°, but these peaks are respectively attributed to the lower electrode Pt and the substrate Al2O3, and have nothing to do with the composition of the dielectric film. The presence or absence of each crystalline phase in the dielectric film of the samples of Examples 1 to 5 and Comparative Examples 2 to 7 is shown in Table 1. The dielectric films of the samples of Examples 1 to 5 contain Bi2Ti2O7. In addition, the dielectric films of the samples of Examples 1, 2, 4 and 5 contain a material selected from Bi4Ti3O 12 ,γ-Bi2O3 and Bi(Mg 0.5 Ti 0.5 )O3.

[0105] As can be seen from the above, a dielectric that satisfies the following two conditions (I) and (II) tends to have a high relative dielectric constant under conditions of high electric field intensity.

[0106] (I) The dielectric has a Bi 2x Mg y Ti z O k The composition represented by MgO satisfies the conditions of x≥0.15, y≤0.40, z≥0.25 and x+y+z=1.0.

[0107] (II) The dielectric contains crystalline Bi2Ti2O7.

[0108] Based on the above description, those skilled in the art will be able to clearly understand many improvements and other embodiments of the present disclosure. Therefore, the above description should only be interpreted as an example, and is provided to teach the best way to perform the present disclosure to those skilled in the art. Without departing from the gist of the present disclosure, its operating conditions, composition, structure and / or function can be substantially changed.

[0109] Table 1

[0110] Industrial Availability

[0111] The dielectric material disclosed herein can be used for applications such as capacitors for vehicles.

Claims

1. A dielectric having a dielectric material composed of Bi 2x Mg y Ti z O k The composition of the representation, The composition satisfies the conditions of x≥0.15, y≤0.40, z≥0.25 and x+y+z=1.0, In the above composition, k is a value for maintaining electrical neutrality.

2. The dielectric according to claim 1, Contains crystalline Bi2Ti2O7.

3. The dielectric according to claim 1, The dielectric contains a crystalline Bi4Ti3O 12 , crystalline γ-Bi2O3 and crystalline Bi(Mg 0.5 Ti 0.5 )O3.

4. The dielectric according to claim 1, The dielectric contains a crystalline Bi4Ti3O 12 and at least one of crystalline γ-Bi2O3.

5. The dielectric according to claim 1, The dielectric contains crystalline γ-Bi2O3.

6. The dielectric according to claim 1, The dielectric has a relative dielectric constant greater than 138 when the electric field strength is increased at an electric field strength of 0.5 MV / cm, and has a relative dielectric constant greater than 100 when the electric field strength is decreased.

7. The dielectric according to claim 1, The dielectric has a relative dielectric constant of greater than 138 when the electric field strength is increased at an electric field strength of 0.7 MV / cm, and has a relative dielectric constant of greater than 57 when the electric field strength is decreased.

8. The dielectric according to claim 1, The dielectric forms at least one film selected from a pulse laser deposition film, a vacuum evaporation film, a sputtering film, an atomic layer deposition film, a chemical vapor growth film and an anodized film.

9. The dielectric according to claim 1, The dielectric is used for a capacitor.

10. A capacitor comprising: a first electrode; The dielectric according to any one of claims 1 to 9 disposed on the first electrode; and A second electrode covers at least a portion of the dielectric.

11. A circuit comprising the capacitor according to claim 10. 12 . A circuit board comprising the capacitor according to claim 10 .

13. A device comprising the capacitor according to claim 10. 14 . An electric storage device comprising the capacitor according to claim 10 .

Images