Dielectric composition, dielectric element, and laminated electronic component

Abstract

To provide a dielectric composition or the like having a small decrease in relative permittivity before and after application of a DC high voltage and having a high relative permittivity under a high electric field.SOLUTION: A dielectric composition according to the present invention comprises a crystalline phase comprising an Sr2NaNb5O15 based oxide having a tungsten bronze structure. The Sr2NaNb 5O15 based oxide has, in a synchrotron radiation XRD pattern measured at a measurement wavelength of 0.85 Å, a crystal structure having a peak top of the synchrotron radiation XRD pattern in the range of 10.7° to 11.0° at a diffraction angle 2θ and the ratio of the intensity of the peak having the peak top to the intensity of the maximum peak having the maximum intensity in the Sr2NaNb5O15 based oxide in the synchrotron radiation XRD pattern is 0.0043 or more.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a dielectric composition, a dielectric element, and a multilayer electronic component.

Background Art

[0002] A dielectric capacitor (for example, a multilayer ceramic capacitor) is a capacitor including a dielectric layer formed of a dielectric composition, and is used as a main component in various electronic devices such as home appliances and automotive control devices. Among such dielectric capacitors, for example, those used in the power train of an electric vehicle are applied with a high voltage (for example, 400V to 800V) as the voltage of the battery increases. Therefore, it is required to maintain a high breakdown voltage (not to break down against the applied high voltage) and a high relative permittivity under a high electric field. In addition, this type of dielectric capacitor is required to have a large capacitance (that is, a large capacity) in addition to a high breakdown voltage and a high relative permittivity under a high electric field.

[0003] As shown in Patent Document 1, in an environment where a high voltage is applied, in order to obtain a large capacitance, it is required that the change (decrease width) in relative permittivity when a DC voltage is applied is small.

[0004] Conventionally, a dielectric composition containing high-permittivity BaTiO3 has been used as a dielectric capacitor. However, the dielectric composition containing BaTiO3 has a significantly reduced relative permittivity under a high electric field. Therefore, for example, as shown in Patent Document 1, it has been proposed to use a dielectric composition having a tungsten bronze type structure for a dielectric capacitor.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a conventional dielectric composition having a tungsten bronze type structure, although the change (decrease width) in the relative permittivity is small, the relative permittivity under a high electric field is not sufficiently high, which has been a problem.

[0007] An object of the present invention is to provide a dielectric composition or the like in which the decrease width of the relative permittivity before and after the application of a DC high voltage is small and the relative permittivity under a high electric field is high.

Means for Solving the Problems

[0008] The means for solving the above problems are as follows. That is, <1> A dielectric composition comprising a crystal phase containing a Sr2NaNb5O-based oxide having a tungsten bronze type structure, wherein the Sr2NaNb5O-based oxide has a peak top in the range of diffraction angle 2θ of 10.7° to 11.0° in the synchrotron radiation XRD pattern measured at a measurement wavelength of 0.85 Å, and among the synchrotron radiation XRD patterns, the ratio of the intensity of the peak having the peak top to the intensity of the maximum peak having the maximum intensity in the Sr2NaNb5O-based oxide is 0.0043 or more. 15 system oxide, a dielectric composition having a crystal structure. 15 system oxide, in the synchrotron radiation XRD pattern measured at a measurement wavelength of 0.85 Å, the diffraction angle 2θ is in the range of 10.7° to 11.0°, has the peak top of the synchrotron radiation XRD pattern, and among the synchrotron radiation XRD patterns, the Sr2NaNb5O 15 For the intensity of the maximum peak having the maximum intensity in the system oxide, the ratio of the intensity of the peak having the peak top is 0.0043 or more.

[0009] <2> The Sr2NaNb5O 15 system oxide, the dielectric composition according to <1> above, which contains Ca, Y, and Zr.

[0010] <3> A dielectric element comprising a dielectric ceramic formed of the dielectric composition according to <1> or <2> above and an electrode attached to the dielectric ceramic.

[0011] <4> A multilayer electronic component having a laminate in which a dielectric layer made of the dielectric composition according to <1> or <2> above and an internal electrode layer are alternately laminated.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a dielectric composition and the like in which the decrease in relative permittivity before and after the application of a DC high voltage is small and the relative permittivity under a high electric field is high.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] Hereinafter, a dielectric composition, a dielectric element, and a multilayer electronic component according to an embodiment will be described.

[0015] The dielectric composition includes a crystal phase containing an Sr2NaNb5O 15 system oxide having a tungsten bronze type structure. In this specification, "Sr2NaNb5O 15 system oxide having a tungsten bronze type structure" refers to a material in which a trace amount of a specific element is incorporated into the A site and B site of Sr2NaNb5O 15 having a tungsten bronze type structure. The specific element is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include Ca, Y, and Zr.

[0016] The dielectric composition may contain the Sr2NaNb5O 15The oxide crystal phase may be included as the main phase or as a secondary phase. Note that the main phase of the crystal phase is the crystal phase corresponding to the peak pattern with the largest proportion in the synchrotron radiation XRD pattern described later. Also, the secondary phase of the crystal phase is the crystal phase corresponding to the peak pattern other than the main phase in the synchrotron radiation XRD pattern. The measurement method of the synchrotron radiation XRD pattern will be described later.

[0017] The Sr2NaNb5O 15 Based on the synchrotron radiation XRD pattern measured at a measurement wavelength of 0.85 Å, the diffraction angle 2θ has a peak top in the range of 10.7° to 11.0°. The diffraction peak corresponding to the peak top has a maximum value in the range of 10.7 ≤ 2θ (°) ≤ 11.0 and a half-value width greater than 0.02°. Note that the diffraction peak in the range of 10.7 ≤ 2θ (°) ≤ 11.0 at a measurement wavelength of 0.85 Å corresponds to an interplanar spacing of 4.43 Å to 4.56 Å.

[0018] Generally, Sr2NaNb5O having a tetragonal tungsten bronze structure 15 is known to have a structure in which NbO6 octahedra are linearly connected in the c-axis direction. In contrast, the dielectric composition of this embodiment is presumed to have a crystal structure in which the octahedral structure is inclined with respect to the c-axis direction.

[0019] In Sr2NaNb5O with a tungsten bronze structure 15 When trace amounts of specific elements (e.g., Ca, Y, Zr) are incorporated into the A-site and B-site, the tilt of the octahedral structure is induced, and accordingly, as described later, it is presumed that a diffraction peak (peak top) is confirmed in the range of diffraction angle 2θ of 10.7° to 11.0°.

[0020] Also, in the synchrotron radiation XRD pattern of the dielectric composition, the Sr2NaNb5O 15It has a crystal structure in which the ratio (peak intensity ratio) of the intensity of the peak having the peak top to the intensity of the maximum peak having the maximum intensity in the case of the oxide-based one is 0.0043 or more. The maximum peak is selected from among the diffraction peaks derived from the tungsten bronze type structure in the synchrotron radiation XRD pattern.

[0021] Note that the dielectric composition of the present embodiment may contain a crystal phase having a perovskite-type crystal structure or other crystal phases as long as the object of the present invention is not impaired.

[0022] Further, the dielectric composition of the present embodiment may contain inevitable impurities at a ratio of 1000 ppm or less.

[0023] Examples of the raw materials used for producing the dielectric composition include Sr-containing compounds containing strontium, Na-containing compounds containing sodium, Nb-containing compounds containing niobium, Ca-containing compounds containing calcium, Y-containing compounds containing yttrium, and Zr-containing compounds containing zirconium.

[0024] Examples of the Sr-containing compound include various inorganic-based powders such as oxides of Sr, composite oxides of Sr, hydroxides of Sr, carbonates of Sr, chlorides of Sr, sulfates of Sr, nitrates of Sr, and phosphates of Sr. Specifically, strontium carbonate powder can be mentioned.

[0025] Examples of the Na-containing compound include various inorganic-based powders such as oxides of Na, composite oxides of Na, hydroxides of Na, carbonates of Na, chlorides of Na, sulfates of Na, nitrates of Na, and phosphates of Na. Specifically, sodium carbonate powder can be mentioned. Specifically, sodium carbonate powder can be mentioned.

[0026] Examples of the Nb-containing compound include various inorganic-based powders such as oxides of Nb, composite oxides of Nb, hydroxides of Nb, carbonates of Nb, chlorides of Nb, sulfates of Nb, nitrates of Nb, and phosphates of Nb. Specifically, niobium oxide powder can be mentioned.

[0027] Examples of the Ca-containing compound include various inorganic powders such as Ca oxides, Ca composite oxides, Ca hydroxides, Ca carbonates, Ca chlorides, Ca sulfates, Ca nitrates, and Ca phosphates. Specifically, calcium carbonate powder can be mentioned.

[0028] Examples of the Y-containing compound include various inorganic powders such as Y oxides, Y composite oxides, Y hydroxides, Y carbonates, Y chlorides, Y sulfates, Y nitrates, and Y phosphates. Specifically, yttrium oxide powder can be mentioned.

[0029] Examples of the Zr-containing compound include various inorganic powders such as Zr oxides, Zr composite oxides, Zr hydroxides, Zr carbonates, Zr chlorides, Zr sulfates, Zr nitrates, and Zr phosphates. Specifically, zirconium oxide powder can be mentioned.

[0030] The manufacturing method of the dielectric composition of this embodiment will be appropriately described in the description of each manufacturing method of the dielectric element and the multilayer electronic component described later.

[0031] In the dielectric composition of this embodiment, the relative permittivity under a high electric field (8 kV / mm) is 1000 or more, and the decrease rate (change rate) of the relative permittivity before and after the application of a DC high voltage is -35% or more, and the decrease width of the relative permittivity is suppressed to be small.

[0032] In the dielectric composition of this embodiment, the relative permittivity in a state where no electric field is applied (0 kV / mm) is not particularly limited as long as the object of the present invention is not impaired, but is preferably 1300 or more.

[0033] Next, while referring to FIG. 1, a dielectric element 200 including a dielectric ceramic 100 made of a dielectric composition will be described. FIG. 1 is a perspective view of the dielectric element 200. As shown in FIG. 1, the dielectric element 200 has a disc-shaped appearance and includes a disc-shaped dielectric ceramic (dielectric layer) 100 and electrodes 301 and 302 attached to the upper and lower surfaces of the dielectric ceramic 100. The dielectric ceramic 100 is formed of the above-described dielectric composition. The electrodes 301 and 302 are made of, for example, Au.

[0034] Here, an example of a method for manufacturing the dielectric element 200 will be described. First, as raw material powders, powders of strontium carbonate, sodium carbonate, niobium oxide, calcium carbonate, yttrium oxide, and zirconium oxide are prepared, and these powders are weighed so as to have a target composition.

[0035] Ethanol is added to the weighed raw material powders, and the mixture is wet-mixed in a ball mill for 15 hours or more to obtain a slurry. The obtained slurry is appropriately dried to obtain mixed powders. The obtained mixed powders are calcined in an air atmosphere at a temperature condition of 1100°C to 1300°C for 5 to 7 hours to obtain calcined powders.

[0036] A dispersant, a binder, and ethanol are added to the obtained calcined powders, and the mixture is pulverized and mixed to obtain a slurry. This slurry is dried and granulated, and the obtained granulated product is uniaxially pressed at a pressure of 20 MPa to obtain a disc-shaped preform. Then, the disc-shaped preform is subjected to CIP treatment (cold isostatic pressing treatment) at a pressure of 150 MPa to obtain a formed body.

[0037] The obtained formed body is held at 650°C for 4 hours to perform a debinding treatment. The formed body after the debinding treatment is subjected to air firing by holding it at a temperature condition of 1300 to 1350°C for 4 hours in an air atmosphere to obtain a dielectric ceramic (dielectric layer) made of a dielectric composition. Polishing treatment is performed on both main surfaces (upper surface, lower surface) of the obtained dielectric ceramic, and then, external electrodes made of Au are formed on both main surfaces by a sputtering method, whereby the dielectric element 200 is obtained.

[0038] Next, while referring to FIG. 2, a multilayer electronic component 1 including a dielectric layer 11 made of a dielectric composition will be described. FIG. 2 is a cross-sectional view of the multilayer electronic component 1. The multilayer electronic component 1 is a so-called multilayer ceramic capacitor. As shown in FIG. 2, it has a laminate 10 including a plurality of dielectric layers 11 formed of a dielectric composition, and a first internal electrode layer (an example of an internal electrode layer) 12 and a second internal electrode layer (an example of an internal electrode layer) 13 alternately laminated via the dielectric layers 11, and a first external electrode 14 and a second external electrode 15 that are electrically connected to these first internal electrode layer 12 and second internal electrode layer 13 and are formed on the outer surface of the laminate 10. On one side surface of the multilayer electronic component 1, the first internal electrode layer 12 and the first external electrode 14 are connected, and on the opposite side surface, the second internal electrode layer 13 and the second external electrode 15 are connected.

[0039] Examples of the materials constituting the first internal electrode layer 12 and the second internal electrode layer 13 include Cu, Ag, Ni, etc. Examples of the materials constituting the first external electrode 14 and the second external electrode 15 include Au, etc.

[0040] Here, an example of the manufacturing method of the multilayer electronic component 1 will be described. First, as raw material powders, powders of strontium carbonate, sodium carbonate, niobium oxide, calcium carbonate, yttrium oxide, and zirconium oxide are prepared, and these powders are weighed so as to have a target composition.

[0041] Ethanol is added to the weighed raw material powders, and the mixture is wet-mixed in a ball mill for 15 hours or more to obtain a slurry. The obtained slurry is appropriately dried to obtain a mixed powder. The obtained mixed powder is calcined in an air atmosphere at a temperature condition of 1100°C to 1300°C for 5 to 7 hours to obtain a calcined powder.

[0042] To the obtained calcined powder, a dispersant, a binder, and ethanol are added, and the mixture is pulverized and mixed to obtain a slurry. By processing this slurry into a sheet shape by the doctor blade method, a plurality of ceramic green sheets are produced.

[0043] Next, using a conductive paste for an internal electrode, an electrode layer that will become an internal electrode layer (first internal electrode layer, second internal electrode layer) is formed on one surface of the ceramic green sheet, for example, by screen printing. The electrode layer is mainly composed of a base metal, for example, nickel (Ni) as the main component.

[0044] Thereafter, a plurality of ceramic green sheets on which the electrode layer is formed are laminated so that the electrode layers are alternately exposed from both sides, and ceramic green sheets on which no electrode layer is formed are further laminated on both the front and back surfaces of the obtained laminate. By pressing the obtained laminate, a laminate in which the ceramic green sheets and the electrode layers are alternately laminated is obtained. This laminate is cut into a desired shape, and then, for example, a debinding treatment is performed by holding it at a temperature of 200 to 400 °C for 2 to 10 hours.

[0045] The laminate after the debinding treatment is subjected to air firing by holding it at a temperature of 1300 to 1350 °C for 4 hours in an air atmosphere. After firing, the ceramic green sheet becomes the dielectric layer 11, and the electrode layer becomes the internal electrode layer (first internal electrode layer, second internal electrode layer).

[0046] After appropriately polishing (barrel polishing, sandblasting, etc.) the side surface of the fired laminate 10, a pair of external electrodes (first external electrode 14, second external electrode 15) made of Au are formed on the side surface of the laminate 10, for example, by sputtering. In this way, the multilayer electronic component 1 is obtained.

[0047] The dielectric composition disclosed in this specification has a small decrease width in the relative permittivity before and after the application of a DC high voltage, and a high relative permittivity under a high electric field. Further, the dielectric composition has a high breakdown voltage.

[0048] Dielectric elements and multilayer electronic components provided with a dielectric layer formed of the above dielectric composition are used, for example, in the power train of an electric vehicle to which a high voltage (for example, 400 V to 800 V) is applied. Examples of the multilayer electronic component include a dielectric capacitor, a multilayer ceramic capacitor, and the like. Further, the dielectric composition may be used in various electronic devices such as home appliances and automotive control devices.

Examples

[0049] Hereinafter, the present invention will be described in more detail based on examples. Note that the present invention is not limited by these examples.

[0050] 〔Examples 1 to 4, Comparative Examples 1 to 4〕 As raw material powders, powders of strontium carbonate, calcium carbonate, sodium carbonate, potassium carbonate, niobium oxide, yttrium oxide, and zirconium oxide were prepared, and while selecting the necessary ones from them, they were weighed to have the respective compositions shown in Table 1. Ethanol was added to the weighed raw material powders, and the mixture was wet-mixed in a ball mill for 15 hours or more to obtain a slurry. The obtained slurry was appropriately dried to obtain a mixed powder. The obtained mixed powder was calcined in an air atmosphere at a temperature of 1200 °C for 6 hours to obtain a calcined powder.

[0051] A dispersant, a binder, and ethanol were added to the obtained calcined powder, and the mixture was pulverized and mixed to obtain a slurry. This slurry was dried and granulated, and the obtained granulated product was uniaxially pressed at a pressure of 20 MPa to obtain a disk-shaped preform. Thereafter, the disk-shaped preform was subjected to CIP treatment (cold isostatic pressing treatment) at a pressure of 150 MPa to obtain a formed body.

[0052] The obtained molded body was subjected to a debinding treatment by holding it at 650 °C for 4 hours. The molded body after the debinding treatment was subjected to air firing by holding it at a temperature of 1300 to 1350 °C for 4 hours in an air atmosphere, thereby obtaining a dielectric porcelain composed of a dielectric composition. Both main surfaces (upper surface and lower surface) of the obtained dielectric porcelain were polished to obtain a measurement sample including mirror-like both main surfaces.

[0053] Thereafter, in order to evaluate the electrical properties, external electrodes made of Au were formed on both main surfaces of the dielectric porcelain by sputtering, thereby obtaining a dielectric element (measurement sample for evaluating electrical properties).

[0054] 〔Evaluation〕 The following tests were conducted on the measurement samples of Examples 1 to 4 and Comparative Examples 1 to 4.

[0055] (Relative permittivity) The relative permittivities (0 kV / mm, 8 kV / mm) of the measurement samples for evaluating electrical properties were calculated from the value of the capacitance at 1 kHz measured using an impedance analyzer at room temperature in a state where no DC voltage was applied (that is, 0 kV / mm) and the value of the capacitance at 1 kHz measured using an impedance analyzer at room temperature in a state where a DC voltage of 8 kV / mm was applied, respectively. The results are shown in Table 1.

[0056] (Reduction rate of relative permittivity) The reduction rate (change rate) [%] from the relative permittivity at an applied voltage of 0 kV / mm to the relative permittivity at an applied voltage of 8 kV / mm was determined by [(relative permittivity at 8 kV / mm) - (relative permittivity at 0 kV / mm)] / (relative permittivity at 0 kV / mm) × 100. The results are shown in Table 1.

[0057] (Radiation light XRD) Structural analysis by synchrotron XRD (X-ray diffraction method) was performed on the polished surface of the measurement sample in a state where no external electrode was formed. The wavelength of the synchrotron radiation was 0.85 Å. For each measurement sample, the obtained synchrotron XRD pattern is shown in Fig. 3. Fig. 3 shows the synchrotron XRD pattern in the range of diffraction angle 2θ of 10° to 20°. The horizontal axis in Fig. 3 represents the diffraction angle 2θ (°), and the vertical axis represents the intensity (arbitrary unit).

[0058] In the obtained synchrotron XRD pattern, background removal was performed by the Sonneveld-Visser method with a peak width threshold of 0.1 and an intensity threshold of 1. Then, the synchrotron XRD pattern was normalized with the peak intensity value of the peak with the highest intensity (maximum peak) being 1. The peak with the highest intensity (maximum peak) was found in the range of diffraction angle 2θ of 17° to 18° for all measurement samples, as shown in Fig. 3. Here, the maximum peak was selected from those in the synchrotron XRD pattern of the Sr2NaNb5O 15 oxide having a tungsten bronze type structure.

[0059] Also, the synchrotron XRD patterns of each measurement sample in the range of diffraction angle 2θ of 9° to 12° are shown in Fig. 4. The horizontal axis in Fig. 4 represents the diffraction angle 2θ (°), and the vertical axis represents the intensity (arbitrary unit).

[0060] (Peak intensity ratio) In the synchrotron XRD pattern of each measurement sample, when a peak top (maximum value) exists in the range of diffraction angle 2θ of 10.7° to 11.0°, the ratio of the intensity of the peak having the peak top to the intensity of the maximum peak (peak intensity ratio) was determined. The results are shown in Table 1. Here, the peak intensity ratio was determined from those in the synchrotron XRD pattern of the Sr2NaNb5O 15 oxide having a tungsten bronze type structure.

[0061]

Table 1

[0062] From the results of synchrotron radiation XRD (see FIGS. 3 and 4), the dielectric compositions of Examples 1 to 4 were confirmed to include a crystal phase containing a Sr2NaNb5O 15 system oxide having a tungsten bronze type structure.

[0063] Also, each of the dielectric compositions of Examples 1 to 4 had a peak top of the synchrotron radiation XRD pattern in the range of diffraction angle 2θ of 10.7° to 11.0°, and among the synchrotron radiation XRD patterns, the ratio (peak intensity ratio) of the intensity of the peak having the peak top to the intensity of the maximum peak having the maximum intensity in the Sr2NaNb5O 15 system oxide was 0.0043 or more. As shown in FIG. 3, in the case of any measurement sample, in the synchrotron radiation XRD pattern derived from the Sr2NaNb5O 15 system oxide, the peak with the highest intensity (maximum peak) was found in the range of diffraction angle 2θ of 17° to 18°. In such dielectric compositions of Examples 1 to 4, the relative permittivity under a high electric field (8 kV / mm) was 1000 or more, and the reduction rate (change rate) of the relative permittivity before and after applying a DC high voltage was -35% or more, and the reduction width of the relative permittivity was suppressed to be small.

[0064] In addition, from the results of synchrotron radiation XRD (see FIGS. 3 and 4), it was confirmed that the dielectric compositions of Examples 1 to 4 also included a crystal phase having a perovskite type crystal structure.

[0065] In the case of the dielectric compositions of Comparative Examples 1 to 4, as shown in FIG. 4, no peak top was found in the range of diffraction angle 2θ of 10.7° to 11.0°. In such cases of Comparative Examples 1 to 4, the reduction rate (change rate) of the relative permittivity was -54.1 to -50.5%, resulting in a large reduction width of the relative permittivity.

[0066] The dielectric composition of Comparative Example 1 has a crystal phase of a tungsten bronze type structure without inclination (tilt) of the octahedral structure. Note that the dielectric composition of Comparative Example 1 also includes a crystal phase of a perovskite type crystal structure. Further, for the dielectric compositions of Comparative Examples 2 to 4, as shown in FIGS. 3 and 4, it was confirmed that they consisted only of the main phase (crystal phase of the tungsten bronze type structure) and did not have a sub-phase. In the case of Comparative Examples 2 to 4, since no tilt of the octahedral structure occurs in the K substitution, it is presumed that as a result, no peak exists in the range of 10.7° to 11.0°.

Explanation of symbols

[0067] 100... Dielectric porcelain (dielectric layer), 200... Dielectric element, 301, 302... Electrodes, 1... Multilayer electronic component, 10... Laminate, 11... Dielectric layer, 12... First internal electrode layer (internal electrode layer), 13... Second internal electrode layer (internal electrode layer), 14... First external electrode, 15... Second external electrode

Claims

1. Sr having a tungsten bronze type structure ２ NaNb ５ O １５ A dielectric composition comprising a crystal phase containing a system oxide The Sr ２ NaNb ５ O １５ -based oxide has a peak top in the range of diffraction angle 2θ of 10.7° to 11.0° in the synchrotron radiation XRD pattern measured at a measurement wavelength of 0.85 Å, and among the synchrotron radiation XRD patterns, the Sr ２ NaNb ５ O １５ -based oxide has a crystal structure in which the ratio of the intensity of the peak having the peak top to the intensity of the maximum peak having the maximum intensity in the -based oxide is 0.0043 or more.

2. said Sr ２ NaNb ５ O １５ The oxide-based dielectric composition according to claim 1 containing Ca, Y, and Zr.

3. A dielectric element comprising a dielectric porcelain formed of the dielectric composition according to Claim 1 or Claim 2, and an electrode attached to the dielectric porcelain.

4. A multilayer electronic component having a laminate in which dielectric layers made of the dielectric composition according to Claim 1 or Claim 2 and internal electrode layers are alternately laminated.

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