Dielectric composition, dielectric element, and multilayer electronic component

Abstract

A dielectric composition according to the present invention includes a crystal phase which contains an Sr2NaNb5O15-based oxide that has a tungsten bronze type structure. The Sr2NaNb5O15-based oxide has a crystal structure wherein: in the synchrotron radiation XRD pattern as measured at a measurement wavelength of 0.85 Å, a peak top of the synchrotron radiation XRD pattern is present in the range of 10.7° to 11.0° of the diffraction angle 2θ; and the ratio of the intensity of a peak having the peak top to the intensity of a maximum peak having the maximum intensity attributed to the Sr2NaNb5O15-based oxide in the synchrotron radiation XRD pattern is 0.0043 or more.

Description

Dielectric composition, dielectric element, and laminated electronic component

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

[0002] Dielectric capacitors (e.g., multilayer ceramic capacitors) are capacitors having a dielectric layer formed from a dielectric composition, and are used as key components in various electronic devices such as home appliances and automobile control devices. Among these dielectric capacitors, for example, those used in the powertrains of electric vehicles are subjected to high voltages (e.g., 400 V to 800 V) as batteries become higher voltages. Therefore, they are required to have a high withstand voltage (not break down under the applied high voltage) as well as a high relative dielectric constant under a high electric field. Furthermore, in addition to the high withstand voltage and high relative dielectric constant under a high electric field, these types of dielectric capacitors are also required to have a large capacitance (i.e., a large capacitance).

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

[0004] Conventionally, high dielectric constant BaTiO ３ Dielectric compositions containing BaTiO ３ Dielectric compositions containing tungsten bronze have a significantly reduced dielectric constant under high electric fields. For this reason, it has been proposed to use a dielectric composition having a tungsten bronze structure in a dielectric capacitor, as shown in Patent Document 1, for example.

[0005] International Publication No. 2017 / 163845

[0006] In conventional dielectric compositions having a tungsten bronze structure, although the change (reduction) in the dielectric constant is small, the dielectric constant 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 which shows a small decrease in relative dielectric constant before and after application of a high DC voltage and which has a high relative dielectric constant under a high electric field.

[0008] The means for solving the above problems are as follows: <1> Sr having a tungsten bronze structure ２ NaNb ５ O １５ A dielectric composition having a crystalline phase containing a Sr-based oxide, ２ NaNb ５ O １５ The Sr-based oxide has a peak top in a synchrotron XRD pattern measured at a measurement wavelength of 0.85 Å in a diffraction angle 2θ range of 10.7° to 11.0°, and in the synchrotron XRD pattern, ２ NaNb ５ O １５ A dielectric composition having a crystalline 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 system oxide is 0.0043 or more.

[0009] <2> The Sr ２ NaNb ５ O １５ The dielectric composition according to <1>, wherein the base oxide contains Ca, Y, and Zr.

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

[0011] <4> A laminated electronic component having a laminate formed by alternately laminating dielectric layers made of the dielectric composition according to <1> or <2> and internal electrode layers.

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

[0013] A perspective view of a dielectric element. A cross-sectional view of a laminated electronic component. Figures showing synchrotron XRD patterns for each measurement sample of Examples 1 to 4 and Comparative Examples 1 to 4, where the diffraction angle 2θ is in the range of 10° to 20°. Figures showing synchrotron XRD patterns for each measurement sample of Examples 1 to 4 and Comparative Examples 1 to 4, where the diffraction angle 2θ is in the range of 9° to 12°.

[0014] The dielectric composition, the dielectric element, and the laminated electronic component according to the embodiment will be described below.

[0015] The dielectric composition is a tungsten bronze-type structured Sr ２ NaNb ５ O １５ In this specification, "a tungsten bronze-type structure Sr ２ NaNb ５ O １５ The "Sr-based oxide" is a tungsten bronze-type structure ２ NaNb ５ O １５ The specific element is not particularly limited as long as it does not impair the object of the present invention, and examples thereof include Ca, Y, and Zr.

[0016] The dielectric composition may contain any of the above Sr as long as it does not impair the object of the present invention. ２ NaNb ５ O １５ The crystalline phase of the system oxide may be contained as a main phase or as a subphase. The main crystalline phase is the crystalline phase corresponding to the peak pattern that occupies the largest proportion in the synchrotron radiation XRD pattern described below. The subphase is the crystalline phase corresponding to the peak pattern other than that of the main phase in the synchrotron radiation XRD pattern. The method for measuring the synchrotron radiation XRD pattern will be described later.

[0017] The Sr ２ NaNb ５ O １５The compound oxide has a peak top in the synchrotron XRD pattern measured at a measurement wavelength of 0.85 Å in a diffraction angle 2θ 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-width greater than 0.02°. The diffraction peak in the range of 10.7≦2θ(°)≦11.0 at a measurement wavelength of 0.85 Å corresponds to a lattice spacing of 4.43 Å to 4.56 Å.

[0018] Generally, Sr has a tetragonal tungsten bronze structure. ２ NaNb ５ O １５ is NbO in the c-axis direction. ６ It is known that the dielectric composition of the present embodiment has a crystal structure in which the octahedron structure is tilted with respect to the c-axis direction.

[0019] Tungsten bronze structure Sr ２ NaNb ５ O １５ It is presumed that the incorporation of trace amounts of specific elements (e.g., Ca, Y, Zr) into the A site and B site of the above induces a tilt of the octahedral structure, and as a result, a diffraction peak (peak top) was confirmed in the diffraction angle 2θ range of 10.7° to 11.0°, as will be described later.

[0020] In addition, the dielectric composition is characterized in that, in the synchrotron XRD pattern, the Sr ２ NaNb ５ O １５ The crystalline structure of the tungsten bronze oxide has a peak intensity ratio of 0.0043 or more, where the peak intensity ratio is selected from the diffraction peaks derived from a tungsten bronze structure in the synchrotron radiation XRD pattern.

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

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

[0023] Examples of raw materials used in the production of 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 Sr-containing compounds include various inorganic powders such as Sr oxide, Sr composite oxide, Sr hydroxide, Sr carbonate, Sr chloride, Sr sulfate, Sr nitrate, Sr phosphate, etc. A specific example is strontium carbonate powder.

[0025] Examples of the Na-containing compound include various inorganic 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. Specific examples include sodium carbonate powder. Specific examples include sodium carbonate powder.

[0026] Examples of Nb-containing compounds include various inorganic powders such as Nb oxide, Nb composite oxide, Nb hydroxide, Nb carbonate, Nb chloride, Nb sulfate, Nb nitrate, Nb phosphate, etc. Specifically, niobium oxide powder can be used.

[0027] Examples of the Ca-containing compound include various inorganic powders such as Ca oxide, Ca composite oxide, Ca hydroxide, Ca carbonate, Ca chloride, Ca sulfate, Ca nitrate, Ca phosphate, etc. A specific example is calcium carbonate powder.

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

[0029] Examples of the Zr-containing compound include various inorganic powders such as Zr oxide, Zr composite oxide, Zr hydroxide, Zr carbonate, Zr chloride, Zr sulfate, Zr nitrate, Zr phosphate, etc. Specific examples include zirconium oxide powder.

[0030] The method for producing the dielectric composition of this embodiment will be explained appropriately in the explanations of the methods for producing the dielectric element and laminated electronic component described later.

[0031] In the dielectric composition of the present embodiment, the relative dielectric constant under a high electric field (8 kV / mm) is 1000 or more, and the rate of decrease (rate of change) in the relative dielectric constant before and after application of a high DC voltage is −35% or more, so that the degree of decrease in the relative dielectric constant is kept small.

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

[0033] Next, a dielectric element 200 including a dielectric porcelain 100 made of a dielectric composition will be described with reference to Fig. 1. Fig. 1 is a perspective view of the dielectric element 200. As shown in Fig. 1, the dielectric element 200 has a disk-shaped appearance and comprises a disk-shaped dielectric porcelain (dielectric layer) 100 and electrodes 301 and 302 attached to the upper and lower surfaces of the dielectric porcelain 100. The dielectric porcelain 100 is formed from the above-mentioned 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, powders of strontium carbonate, sodium carbonate, niobium oxide, calcium carbonate, yttrium oxide, and zirconium oxide are prepared as raw material powders, and these powders are weighed out so as to obtain the desired 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 resulting slurry is dried appropriately to obtain a mixed powder. The resulting mixed powder is calcined in an air atmosphere at a temperature of 1100°C to 1300°C for 5 to 7 hours to obtain a calcined powder.

[0036] The calcined powder was mixed with a dispersant, a binder, and ethanol to obtain a slurry, which was then dried and granulated. The granulated material was then uniaxially pressed at a pressure of 20 MPa to obtain a disk-shaped pre-formed body. The disk-shaped pre-formed body was then subjected to cold isostatic pressing (CIP) at a pressure of 150 MPa to obtain a compact.

[0037] The obtained compact is subjected to a binder removal treatment by holding it at 650°C for 4 hours. The compact after the binder removal treatment is subjected to air firing by holding it in an air atmosphere at a temperature condition of 1300 to 1350°C for 4 hours, thereby obtaining a dielectric ceramic (dielectric layer) made of the dielectric composition. Both main surfaces (upper and lower surfaces) of the obtained dielectric ceramic are subjected to a polishing treatment, and then external electrodes made of Au are formed on both main surfaces by a sputtering method, thereby obtaining the dielectric element 200.

[0038] Next, a laminated electronic component 1 including a dielectric layer 11 made of a dielectric composition will be described with reference to Fig. 2 . Fig. 2 is a cross-sectional view of the laminated electronic component 1. The laminated electronic component 1 is a so-called multilayer ceramic capacitor, and as shown in Fig. 2 , includes a laminate 10 having a plurality of dielectric layers 11 made of a dielectric composition, first internal electrode layers (an example of internal electrode layers) 12 and second internal electrode layers (an example of internal electrode layers) 13 alternately stacked with the dielectric layers 11 interposed therebetween, and first external electrodes 14 and second external electrodes 15 electrically connected to the first internal electrode layers 12 and second internal electrode layers 13 and formed on the outer surface of the laminate 10. The first internal electrode layers 12 and the first external electrode 14 are connected on one side of the laminated electronic component 1, and the second internal electrode layers 13 and the second external electrode 15 are connected on the other opposing side.

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

[0040] Here, an example of a method for manufacturing the laminated electronic component 1 will be described. First, powders of strontium carbonate, sodium carbonate, niobium oxide, calcium carbonate, yttrium oxide, and zirconium oxide are prepared as raw material powders, and these powders are weighed out so as to obtain the desired 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 resulting slurry is dried appropriately to obtain a mixed powder. The resulting mixed powder is calcined in an air atmosphere at a temperature of 1100°C to 1300°C for 5 to 7 hours to obtain a calcined powder.

[0042] A dispersant, a binder, and ethanol are added to the calcined powder, and the mixture is pulverized and mixed to obtain a slurry, which is then processed into a sheet shape by a doctor blade method to produce a plurality of ceramic green sheets.

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

[0044] Next, multiple ceramic green sheets with electrode layers formed thereon are stacked so that the electrode layers are exposed alternately from both sides, and ceramic green sheets without electrode layers are stacked on both the front and back sides of the resulting laminate. The resulting laminate is then pressed together to obtain a laminate in which ceramic green sheets and electrode layers are alternately stacked. This laminate is then cut into a desired shape and then subjected to a binder removal treatment, for example, by holding it at a temperature of 200 to 400°C for 2 to 10 hours.

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

[0046] After the firing, the side surfaces of the laminate 10 are polished appropriately (by barrel polishing, sandblasting, or the like), and then a pair of external electrodes (first external electrode 14, second external electrode 15) made of Au are formed, for example, by sputtering, on the side surfaces of the laminate 10. In this manner, the laminate electronic component 1 is obtained.

[0047] The dielectric composition disclosed herein exhibits a small decrease in relative permittivity before and after application of a high DC voltage, a high relative permittivity under a high electric field, and a high withstand voltage.

[0048] Dielectric elements and laminated electronic components having a dielectric layer formed from the dielectric composition are used, for example, in the powertrain of an electric vehicle to which a high voltage (e.g., 400 V to 800 V) is applied. Examples of the laminated electronic components include dielectric capacitors and laminated ceramic capacitors. The dielectric composition may also be used in various electronic devices such as home appliances and automobile control devices.

[0049] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples in any way.

[0050] Examples 1 to 4, Comparative Examples 1 to 4 Powders of strontium carbonate, calcium carbonate, sodium carbonate, potassium carbonate, niobium oxide, yttrium oxide, and zirconium oxide were prepared as raw material powders, and necessary powders were selected from these and weighed to achieve the 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] The calcined powder was mixed with a dispersant, a binder, and ethanol to obtain a slurry. The slurry was dried and granulated, and the granulated material was uniaxially pressed at a pressure of 20 MPa to obtain a disk-shaped pre-formed body. The disk-shaped pre-formed body was then subjected to cold isostatic pressing (CIP) at a pressure of 150 MPa to obtain a compact.

[0052] The obtained compact was subjected to a binder removal treatment by holding it at 650°C for 4 hours. The compact after the binder removal treatment was subjected to air firing by holding it in an air atmosphere at a temperature condition of 1300 to 1350°C for 4 hours, thereby obtaining a dielectric porcelain made of the dielectric composition. Both main surfaces (upper and lower surfaces) of the obtained dielectric porcelain were subjected to a polishing treatment to obtain a measurement sample including both mirror-like 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 ceramic by sputtering, thereby obtaining a dielectric element (a measurement sample for evaluating the electrical properties).

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

[0055] (Dielectric Constant) The dielectric constants (0 kV / mm, 8 kV / mm) of the measurement samples for evaluating electrical properties were calculated from the capacitance value at 1 kHz measured using an impedance analyzer at room temperature without applying a DC voltage (i.e., 0 kV / mm) and the capacitance value at 1 kHz measured using an impedance analyzer at room temperature with applying a DC voltage of 8 kV / mm. The results are shown in Table 1.

[0056] (Reduction Rate of Dielectric Constant) The reduction rate (change rate) [%] of the dielectric constant at an applied voltage of 0 kV / mm to the dielectric constant at an applied voltage of 8 kV / mm was calculated by [(Dielectric constant at 8 kV / mm) - (Dielectric constant at 0 kV / mm)] / (Dielectric constant at 0 kV / mm) x 100. The results are shown in Table 1.

[0057] (Synchrotron XRD) A structural analysis was performed by synchrotron XRD (X-ray diffraction) on the polished surface of the measurement sample without external electrodes. The wavelength of the synchrotron radiation was 0.85 Å. The synchrotron XRD pattern obtained for each measurement sample is shown in FIG. 3. FIG. 3 shows the synchrotron XRD patterns with a diffraction angle 2θ in the range of 10° to 20°. The horizontal axis of FIG. 3 represents the diffraction angle 2θ (°), and the vertical axis represents the intensity (arbitrary units).

[0058] The obtained synchrotron radiation XRD patterns were subjected to background removal by the Sonneveld-Visser method, with a peak width threshold of 0.1 and an intensity threshold of 1. The synchrotron radiation XRD patterns were then normalized by setting the peak intensity value of the peak with the highest intensity (maximum peak) to 1. As shown in FIG. 3, the peak with the highest intensity (maximum peak) was observed in the range of diffraction angle 2θ of 17° to 18° for all the measured samples. The maximum peak here was determined to be the peak of Sr having a tungsten bronze structure in the synchrotron radiation XRD patterns. ２ NaNb ５ O １５ The oxides were selected from the series.

[0059] The synchrotron XRD patterns of each measurement sample with a diffraction angle 2θ in the range of 9° to 12° are shown in Fig. 4. The horizontal axis of 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 calculated. The results are shown in Table 1. The peak intensity ratio here is calculated based on the ratio of the intensity of the peak having the peak top to the intensity of the maximum peak in the synchrotron XRD pattern of Sr having a tungsten bronze structure. ２ NaNb ５ O １５ The values ​​were calculated from those for the oxides.

[0061]

[0062] The dielectric compositions of Examples 1 to 4 were found to have a tungsten bronze structure, as determined by synchrotron XRD (see FIGS. 3 and 4). ２ NaNb ５ O １５ It was confirmed that the alloy had a crystalline phase containing the base oxide.

[0063] In addition, the dielectric compositions of Examples 1 to 4 all have a peak top in the synchrotron XRD pattern in the range of a diffraction angle 2θ of 10.7° to 11.0°, and in the synchrotron XRD pattern, Sr２ NaNb ５ O １５ 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 Sr-based oxide was 0.0043 or more. ２ NaNb ５ O １５ In the synchrotron XRD patterns derived from the oxides, the peak with the highest intensity (maximum peak) was observed in the diffraction angle 2θ range of 17° to 18°. In the dielectric compositions of Examples 1 to 4, the dielectric constant under a high electric field (8 kV / mm) was 1000 or more, and the rate of decrease (rate of change) in the dielectric constant before and after application of a high DC voltage was −35% or more, so the decrease in the dielectric constant was kept small.

[0064] It was confirmed from the results of synchrotron radiation XRD (see FIGS. 3 and 4) that the dielectric compositions of Examples 1 to 4 also contained a crystalline phase with a perovskite-type crystal structure.

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

[0066] The dielectric composition of Comparative Example 1 has a crystalline phase of a tungsten bronze structure with no tilt of the octahedral structure. The dielectric composition of Comparative Example 1 also contains a crystalline phase of a perovskite structure. As shown in FIGS. 3 and 4, it was confirmed that the dielectric compositions of Comparative Examples 2 to 4 consist only of a main phase (a crystalline phase of a tungsten bronze structure) and do not have a subphase. In the cases of Comparative Examples 2 to 4, it is presumed that the K substitution does not cause tilt of the octahedral structure, resulting in no peak in the range of 10.7° to 11.0°.

[0067] 100...Dielectric ceramic (dielectric layer), 200...Dielectric element, 301, 302...Electrodes, 1...Laminated 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 with tungsten bronze structure ２ NaNb ５ O １５ A dielectric composition having a crystal phase containing a Sr-based oxide, ２ NaNb ５ O １５ The Sr-based oxide has a peak top in a synchrotron XRD pattern measured at a measurement wavelength of 0.85 Å in a diffraction angle 2θ range of 10.7° to 11.0°, and in the synchrotron XRD pattern, ２ NaNb ５ O １５ A dielectric composition having a crystal structure in which the ratio of the intensity of a peak having said peak top to the intensity of a maximum peak having the maximum intensity in a system oxide is 0.0043 or more.

2. The Sr ２ NaNb ５ O １５ The dielectric composition according to claim 1 , wherein the base oxide comprises Ca, Y, and Zr.

3. A dielectric element comprising a dielectric ceramic formed from the dielectric composition according to claim 1 or 2, and an electrode attached to the dielectric ceramic.

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

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