Dielectric composition, dielectric element, and laminated electronic component

Abstract

A dielectric composition (2) according to the present invention is provided with a first phase (21) and a second phase (22), the first phase (21) having a tungsten bronze-type crystal structure containing at least Sr, Na, Nb, Ca, Y, and Zr, the second phase (22) having a perovskite-type crystal structure containing at least Sr, Na, Ca, Y, and Zr, and in an observation range (S) set in a cross-section of the dielectric composition (2), the thickness of the first phase (21) is greater than that of the second phase (22). The second phase (22) is contained in a proportion of 8.8% to 60% (inclusive) with respect to the area (100%) of the entire observation range (S) other than the holes (20).

Description

Technical Field

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

[0002] Dielectric capacitors (e.g., multilayer ceramic capacitors) are capacitors with a dielectric layer formed from a dielectric composition and are used as main components in various electronic devices such as household appliances and automotive control equipment. Among such dielectric capacitors, for example, capacitors used in the powertrain system of electric vehicles are subjected to high voltages (e.g., 400V to 800V) as the voltage of the battery increases, and therefore require high withstand voltage (not to be destroyed by the applied high voltage) and to maintain a high relative dielectric constant under high electric fields. In addition, such dielectric capacitors are required to have high electrostatic capacitance (i.e., large capacity) in addition to high withstand voltage and high relative dielectric constant under high electric fields.

[0003] Note that, as disclosed in Patent Document 1, in order to obtain a large electrostatic capacitance in an environment where a high voltage is applied, a small change (amount of reduction) in the relative dielectric constant when a DC voltage is applied is required.

[0004] Conventionally, dielectric compositions containing BaTiO3, which has a high dielectric constant, have been used in dielectric capacitors. However, the relative dielectric constant of dielectric compositions containing BaTiO3 significantly decreases under high electric fields. Therefore, for example, the use of dielectric compositions with a tungsten bronze structure, such as that described in Patent Document 1, has been proposed for use in dielectric capacitors.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2017 / 163845 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In conventional tungsten bronze type dielectric compositions, although the change (decrease) in the relative dielectric constant is small, the relative dielectric constant under high electric fields cannot be said to be sufficiently high, which is a problem.

[0010] An object of the present invention is to provide a dielectric composition or the like having a small decrease in relative dielectric constant before and after application of a high DC voltage and a high relative dielectric constant under a high electric field.

[0011] Means for solving problems

[0012] The means for solving the above-mentioned problems are as follows.

[0013] <1> A dielectric composition comprising: a first phase having a tungsten bronze-type crystal structure containing at least Sr, Na, Nb, Ca, Y, and Zr; and a second phase having a perovskite-type crystal structure containing at least Sr, Na, Ca, Y, and Zr, wherein, within an observation range defined on a cross-section of the dielectric composition, the second phase is contained in a ratio of 8.8% to 60% relative to the entire area (100%) of the observation range excluding holes.

[0014] <2> According to the <1> The dielectric composition described above, wherein the concentration of Na contained in the second phase is 2.1 times or more and 2.5 times or less of the concentration of Na contained in the first phase, and the concentration of Sr contained in the second phase is 0.59 times or more and 0.63 times or less of the concentration of Sr contained in the first phase.

[0015] <3> According to the <1> or <2> The dielectric composition described herein contains the second phase at a ratio of 8.8% to 32% with respect to the entire area (100%) of the observation range excluding the pores.

[0016] <4> A dielectric element comprising <1> to <3> A dielectric ceramic formed of the dielectric composition according to any one of the above, and an electrode mounted on the dielectric ceramic.

[0017] <5> A laminated electronic component comprising a laminated body in which dielectric layers and internal electrode layers are alternately laminated, wherein the dielectric layers contain the <1> to <3> The dielectric composition according to any one of the above.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to provide a dielectric composition or the like which has a small decrease in relative dielectric constant before and after application of a high DC voltage and a high relative dielectric constant under a high electric field. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [ Figure 1 ] is a three-dimensional diagram of a dielectric element.

[0021] [ Figure 2 ] is a cross-sectional view of stacked electronic components.

[0022] [ Figure 3 ] is a diagram showing an SEM image of a cut surface in the measurement sample of Example 4.

[0023] [ Figure 4 ]yes Figure 3 A magnified view of a portion of the SEM image.

[0024] [ Figure 5] is a diagram showing a first binarized image corresponding to the SEM image of Example 4.

[0025] [ Figure 6 ] is a diagram showing a second binarized image corresponding to the SEM image of Example 4.

[0026] [ Figure 7 ] is a diagram showing the X-ray diffraction patterns of Example 4 and Example 5. DETAILED DESCRIPTION

[0027] Hereinafter, a dielectric composition, a dielectric element, and a laminated electronic component according to embodiments will be described.

[0028] The dielectric composition includes: a first phase having a tungsten bronze type crystal structure containing at least Sr, Na, Nb, Ca, Y, and Zr; and a second phase having a perovskite type crystal structure containing at least Sr, Na, Ca, Y, and Zr.

[0029] In an observation range defined on a cross-section of the dielectric composition, the second phase comprises 8.8% to 60% (preferably 8.8% to 32%) of the entire area of the observation range excluding the holes (100%). The remainder of the entire area of the observation range excluding the second phase is the first phase.

[0030] The tungsten bronze type crystal structure in the first phase includes a tungsten bronze type composite oxide containing at least Sr, Na, Nb, Ca, Y, and Zr. The tungsten bronze type composite oxide is represented by the following composition formula (1).

[0031] Sr a Ca b Y c Na x Nb 5-d Zr d O 15 ·····(1)

[0032] As the values of the coefficients x, a, b, c, and d in the composition formula (1), preferred values are appropriately selected from the viewpoint of the electrical properties of the dielectric composition, among the values at which a tungsten bronze type crystal structure is established.

[0033] Specifically, the coefficient a of Sr is 1.34≤a≤1.75, the coefficient b of Ca is 0.05≤b≤0.11, the coefficient c of Y is 0.09≤c≤0.14, the coefficient x of Na is 0.82≤x≤1.04, the coefficient d of Zr is 0.02≤d≤0.08, and the coefficient 5-d of Nb is 4.82≤5-d≤4.98.

[0034] The perovskite-type crystal structure in the second phase includes a perovskite-type composite oxide containing at least Sr, Na, Ca, Y, and Zr. The perovskite-type composite oxide is represented by the following composition formula (2).

[0035] (Sr e Ca f Y g Na h )(Nb i Zr j )O3 ·····(2)

[0036] As the values of the coefficients e, f, g, h, i, and j in the composition formula (2), preferred values are appropriately selected from the viewpoint of the electrical properties of the dielectric composition, among the values at which the perovskite-type crystal structure is established.

[0037] Specifically, the coefficient e of Sr is 0.186≤e≤0.242, the coefficient f of Ca is 0.010≤f≤0.020, the coefficient g of Y is 0.007≤g≤0.009, and the coefficient h of Na is 0.431≤h≤0.505.

[0038] In addition, the coefficient i of Nb is 0.911≤i≤0.998, and the coefficient j of Zr is 0.009≤j≤0.089.

[0039] In the dielectric composition, the concentration of Na contained in the second phase is preferably 2.1 times or more and 2.5 times or less of the concentration of Na contained in the first phase.

[0040] In the dielectric composition, the concentration of Sr contained in the second phase is preferably 0.59 times or more and 0.63 times or less of the concentration of Sr contained in the first phase.

[0041] It should be noted that the dielectric composition may include crystal phases other than the first phase and the second phase as long as the purpose of the present invention is not impaired.

[0042] Furthermore, the dielectric composition may contain elements other than the elements contained in the first phase and the second phase as unavoidable impurities at a ratio of 1000 ppm or less.

[0043] 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.

[0044] Examples of the Sr-containing compound include various inorganic powders such as Sr oxides, Sr composite oxides, Sr hydroxides, Sr carbonates, Sr chlorides, Sr sulfates, Sr nitrates, and Sr phosphates. Specifically, strontium carbonate powder is mentioned.

[0045] Examples of Na-containing compounds include various inorganic powders such as Na oxides, Na composite oxides, Na hydroxides, Na carbonates, Na chlorides, Na sulfates, Na nitrates, and Na phosphates. Specifically, sodium carbonate powder can be used. Specifically, sodium carbonate powder can be used.

[0046] Examples of the Nb-containing compound include various inorganic powders such as Nb oxides, Nb composite oxides, Nb hydroxides, Nb carbonates, Nb chlorides, Nb sulfates, Nb nitrates, and Nb phosphates. Specifically, niobium oxide powder is mentioned.

[0047] 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 is mentioned.

[0048] 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 is included.

[0049] 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 is mentioned.

[0050] In addition, the manufacturing method of the dielectric composition will be appropriately described in the description of each manufacturing method of the dielectric element and the laminated electronic component mentioned later.

[0051] In an observation range set on the cross-section of the dielectric composition, when the second phase is contained at a ratio of 8.8% to 60% relative to the entire area (100%) of the observation range excluding the holes, the relative dielectric constant under a high electric field (8 kV / mm) is 900 or higher, and the rate of decrease (rate of change) in the relative dielectric constant before and after application of a high DC voltage is greater than -41%, and the magnitude of the decrease in the relative dielectric constant is suppressed to a small extent.

[0052] In the dielectric composition, the relative dielectric constant in a state where no electric field is applied (0 kV / mm) is not particularly limited unless the purpose of the present invention is impaired, but is preferably 1300 or greater, more preferably 1400 or greater, and even more preferably 1500 or greater.

[0053] In particular, in an observation range set on the cross-section of the dielectric composition, when the second phase is contained at a ratio of 8.8% to 32% relative to the entire area (100%) of the observation range excluding the holes, the relative dielectric constant under a high electric field (8 kV / mm) is 1000 or higher, 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 higher, further suppressing the decrease in the relative dielectric constant.

[0054] Next, refer to Figure 1 , a dielectric element 200 including a dielectric ceramic 100 containing a dielectric composition will be described. Figure 1 is a perspective view of the dielectric element 200. Figure 1 As shown, the dielectric element 200 has a disc-shaped appearance and includes a disc-shaped dielectric ceramic (dielectric layer) 100 and electrodes 301 and 302 mounted on the upper and lower surfaces of the dielectric ceramic 100. The dielectric ceramic 100 is formed from the above-mentioned dielectric composition. The electrodes 301 and 302 contain, for example, Au.

[0055] Here, an example of a method for manufacturing the dielectric element 200 is 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 to obtain a target composition.

[0056] After adding ethanol to the weighed raw material powder, wet mixing was performed in a ball mill for at least 15 hours to obtain a slurry. The resulting slurry was then dried to obtain a mixed powder. The resulting mixed powder was pre-calcined at 1100°C to 1300°C in an atmosphere for 5 to 7 hours to obtain a calcined powder.

[0057] The calcined powder was then pulverized and mixed with a dispersant, a binder, and ethanol to obtain a slurry. The slurry was dried and granulated, and the resulting granules were uniaxially pressed at a pressure of 20 MPa to obtain a disk-shaped preform. The disk-shaped preform was then subjected to a CIP (cold isostatic pressing) treatment at a pressure of 150 MPa to obtain a compact.

[0058] The resulting compact was held at 650°C for 4 hours to remove the binder. The debindered compact was then sintered in air at 1300-1350°C for 4 hours to obtain a dielectric ceramic (dielectric layer) containing the dielectric composition. Both main surfaces (top and bottom) of the resulting dielectric ceramic were polished, and then external electrodes containing Au were formed on both main surfaces by sputtering, thereby obtaining dielectric element 200.

[0059] Next, refer to Figure 2 , a laminated electronic component 1 including a dielectric layer 11 containing a dielectric composition will be described. Figure 2 is a cross-sectional view of a laminated electronic component 1. The laminated electronic component 1 is a so-called laminated ceramic capacitor, such as Figure 2 As shown, the laminated electronic component 1 comprises a laminate 10 having a plurality of dielectric layers 11 formed from a dielectric composition; first internal electrode layers 12 (an example of an internal electrode layer) and second internal electrode layers 13 (an example of an internal electrode layer) alternately stacked with the dielectric layers 11 interposed therebetween; and first external electrodes 14 and second external electrodes 15 formed on the outer surfaces of the laminate 10 and electrically connected to the first internal electrode layers 12 and the second internal electrode layers 13. 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 opposite side.

[0060] Examples of materials constituting the first internal electrode layer 12 and the second internal electrode layer 13 include Cu, Ag, and Ni. Examples of materials constituting the first external electrode 14 and the second external electrode 15 include Au.

[0061] Here, an example of a method for manufacturing the laminated electronic component 1 is 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 to obtain a target composition.

[0062] After adding ethanol to the weighed raw material powder, wet mixing was performed in a ball mill for at least 15 hours to obtain a slurry. The resulting slurry was then dried to obtain a mixed powder. The resulting mixed powder was pre-calcined at 1100°C to 1300°C in an atmosphere for 5 to 7 hours to obtain a calcined powder.

[0063] A dispersant, a binder, and ethanol were added to the calcined powder, and the mixture was pulverized and mixed to obtain a slurry. The slurry was processed into a sheet shape by a doctor blade method to produce a plurality of ceramic green sheets.

[0064] Next, an internal electrode conductive paste is used to form internal electrode layers (first internal electrode layer, second internal electrode layer) on one side of the ceramic green sheet, for example, by screen printing. The electrode layers are mainly composed of a base metal, such as nickel (Ni).

[0065] Next, multiple ceramic green sheets with electrode layers are stacked so that the electrode layers are alternately exposed from both sides. Ceramic green sheets without electrode layers are further stacked on both the front and back sides of the resulting stack. The resulting stack is then press-bonded to produce a stack consisting of alternating ceramic green sheets and electrode layers. This stack is cut into the desired shape and then held at a temperature of, for example, 200 to 400°C for 2 to 10 hours to remove the binder.

[0066] The binder-removed laminate is fired in air at 1300-1350° 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 and second internal electrode layers).

[0067] After the fired laminate 10 is appropriately polished (by barrel polishing, sandblasting, etc.), a pair of external electrodes (first external electrode 14 and second external electrode 15) made of Au are formed on the side surfaces of the laminate 10 by, for example, sputtering. In this way, the laminated electronic component 1 is obtained.

[0068] The dielectric composition disclosed in this specification exhibits a small decrease in relative permittivity before and after application of a high DC voltage, a high relative permittivity under high electric fields, and a high withstand voltage.

[0069] Dielectric elements and laminated electronic components comprising a dielectric layer formed from the dielectric composition are used, for example, in powertrain systems for electric vehicles that are subject to high voltages (e.g., 400V to 800V). Examples of such laminated electronic components include dielectric capacitors and laminated ceramic capacitors. Furthermore, the dielectric composition can be used in various electronic devices, including home appliances and automotive control devices.

[0070] Example

[0071] Hereinafter, the present invention will be described in more detail based on examples. It should be noted that the present invention is not limited to these examples.

[0072] [Examples 1 to 6, Comparative Examples 1 to 4]

[0073] As raw material powders, powders of strontium carbonate, calcium carbonate, sodium carbonate, potassium carbonate, niobium oxide, yttrium oxide, and zirconium oxide were prepared. The desired powders were selected from these and weighed to give the compositions shown in Table 1. Ethanol was added to the weighed raw material powders, and wet mixing was performed using a ball mill for at least 15 hours to obtain a slurry. The obtained slurry was suitably dried to obtain a mixed powder. The obtained mixed powder was pre-calcined at 1200°C in an atmosphere for 6 hours to obtain a calcined powder.

[0074] A dispersant, a binder, and ethanol were added to the calcined powder, and the resulting material was crushed and mixed to obtain a slurry. The slurry was dried and granulated, and the resulting granules were uniaxially pressed at a pressure of 20 MPa to obtain a disc-shaped preform. The disc-shaped preform was then subjected to a CIP (cold isostatic pressing) treatment at a pressure of 150 MPa to obtain a compact.

[0075] The resulting compact was held at 650°C for 4 hours to remove the binder. The debindered compact was then sintered in air at 1300-1350°C for 4 hours to obtain a dielectric ceramic containing the dielectric composition. Both main surfaces (upper and lower surfaces) of the resulting dielectric ceramic were polished to obtain a measurement sample having both mirror-finished main surfaces.

[0076] Then, in order to evaluate the electrical characteristics, external electrodes made of Au were formed on both main surfaces of the dielectric ceramic by sputtering, thereby obtaining a dielectric element (measurement sample for evaluating the electrical characteristics).

[0077] [evaluate]

[0078] The following tests were performed on each sample of Examples 1 to 6 and Comparative Examples 1 to 4.

[0079] (Relative dielectric constant)

[0080] The relative dielectric constants (0 kV / mm, 8 kV / mm) of the measurement samples used for electrical property evaluation were calculated from the capacitance values at 1 kHz measured using an impedance analyzer at room temperature with no DC voltage applied (i.e., 0 kV / mm) and the capacitance values at 1 kHz measured using an impedance analyzer at room temperature with a DC voltage of 8 kV / mm applied. The results are shown in Table 3.

[0081] (Reduction rate of relative dielectric constant)

[0082] The rate of decrease (rate of change) [%] in the relative permittivity at an applied voltage of 0 kV / mm to that at an applied voltage of 8 kV / mm was calculated from [(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 3.

[0083] (Ratio of the second phase)

[0084] Different from the measurement sample for evaluating electrical characteristics, a measurement sample in a state where no external electrode is formed is prepared, and the measurement sample is cut in the thickness direction. The obtained cut surface is subjected to grinding treatment. Then, a scanning electron microscope (SEM) is used to photograph the cut surface of the measurement sample after grinding treatment at a magnification of 500 times, and an SEM image of the cut surface is obtained. Then, by performing image analysis using image processing software (Image-J) on the obtained SEM image, the proportion of the secondary phase in the entire S (excluding the hole) of the observation range (the range of a rectangle of 1280 pixels vertically and 960 pixels horizontally) set on the cut surface is calculated according to the following steps.

[0085] Here, an example of a SEM image is shown. Figure 3 and Figure 4 . Figure 3 This is an SEM image of the cross section of the measurement sample (dielectric composition 2) of Example 4. Figure 4 It will Figure 3 A part of the SEM image is enlarged. Figure 3 and Figure 4 In FIG, the black spotted portion corresponds to the pores (voids) 20 formed in the dielectric composition 2. Figure 3 and Figure 4 The lightest colored portion corresponds to the first phase 21 in the dielectric composition. Figure 3 and Figure 4 In the SEM image of the measurement sample, the portion that is darker than the first phase 21 and lighter than the pores 20 (i.e., the gray portion) corresponds to the second phase 22 in the dielectric composition. In this way, in the SEM image of the measurement sample, the first phase, the second phase, and the pores can be distinguished from each other by the difference in color (such as the depth of the pixel color).

[0086] Therefore, for the SEM image, by setting appropriate thresholds, binarization processing for detecting the second phase and pores (hereinafter referred to as "first binarization processing") and binarization processing for detecting only pores (hereinafter referred to as "second binarization processing") are performed respectively.

[0087] Next, based on the first binarized image obtained by the first binarization process, the ratio of the total area of the second phase and the pores to the entire area of the observation range of the SEM image (hereinafter referred to as "ratio A1") is calculated by Li's method. Figure 5 The first binarized image corresponding to the SEM image of Example 4 is shown in FIG. Figure 5 In FIG. 1 , the black spot-like portion 23 corresponds to the second phase and / or the pore.

[0088] In addition, based on the second binarized image obtained in the second binarization process, the ratio of the area of the hole to the entire area of the observation range of the SEM image (hereinafter referred to as "ratio A2") is calculated by the IsoDATA method. It should be noted that, for reference, Figure 6 The second binarized image corresponding to the SEM image of Example 4 is shown in FIG. Figure 6 In FIG. 1 , the black spot-like portion 24 corresponds to the hole.

[0089] Based on the obtained ratios A1 and A2, the ratio of the area of the second phase to the total area of the observation range of the cross-section excluding the holes was calculated using the formula [((Ratio A1) - (Ratio A2)) / (1 - (Ratio A2)) × 100]. The results are shown in Table 3.

[0090] (Elemental Analysis)

[0091] The elemental analysis of the first phase and the second phase was performed using an electron probe microanalyzer (EPMA) on the cross-section of the sample. The results are shown in Table 1. It should be noted that the measurement conditions were an accelerating voltage of 15 kV and an irradiation current of 25 nA. Table 1 shows the concentration (mol %) of each element relative to 100 mol % of the entire element.

[0092] For reference, the composition formulas representing the first phase tungsten bronze-type crystal structure and the second phase perovskite-type crystal structure in various examples, etc., obtained from the elemental analysis results (element ratios) in Table 1 are shown in Table 2. The composition formula for the tungsten bronze-type crystal structure was obtained so that the sum of the Nb concentration and the Zr concentration (Nb + Zr) shown in Table 1 was 5 (the coefficients of Nb and Zr in the composition formula). The composition formula for the perovskite-type crystal structure was obtained so that the sum of the Nb concentration and the Zr concentration (Nb + Zr) shown in Table 1 was 1 (the coefficients of Nb and Zr in the composition formula).

[0093] (Sr concentration ratio)

[0094] Based on the EPMA measurement results (see Table 1), the ratio of the Sr concentration contained in the second phase of the measurement sample to the Sr concentration contained in the first phase (Sr concentration ratio) was determined. The results are shown in Table 3.

[0095] (Na concentration ratio)

[0096] Based on the EPMA measurement results (see Table 1), the ratio of the concentration of Na contained in the second phase of the measurement sample to the concentration of Na contained in the first phase (Na concentration ratio) was determined.

[0097] (XRD)

[0098] The polished surface of the sample was subjected to structural analysis using XRD (X-ray diffraction). A micro X-ray diffractometer was used as the XRD measurement instrument, and analysis was performed within the range of 2θ = 20° to 90° using CuKα radiation.

[0099] For reference, Figure 7 The X-ray diffraction patterns of Examples 4 and 5 are shown in FIG. Figure 7 In the upper and lower graphs shown in FIG. 1 , the upper graph is the X-ray diffraction pattern of the sample measured in Example 4, and the lower graph is the X-ray diffraction pattern of the sample measured in Example 5. Figure 7 The horizontal axis represents the diffraction angle (°), and the vertical axis represents the intensity (arbitrary unit).

[0100] [Table 1]

[0101]

[0102] [Table 2]

[0103]

[0104] [Table 3]

[0105]

[0106] In the case of the dielectric compositions of Examples 1 to 6, the results of XRD and EPMA confirmed that the first phase had a tungsten bronze-type crystal structure containing Sr, Na, Nb, Ca, Y, and Zr, and the second phase had a perovskite-type crystal structure containing Sr, Na, Ca, Y, and Zr.

[0107] In contrast, in the case of the dielectric composition of Comparative Example 1, the results of XRD and EPMA confirmed the presence of a first phase (tungsten bronze type composite oxide) having only a tungsten bronze type crystal structure containing Sr, Na, Nb, Ca, Y, and Zr.

[0108] In the case of the dielectric compositions of Comparative Examples 2 to 4, the results of XRD and EPMA confirmed that the first phase contained only a tungsten bronze type crystal structure containing Sr, Na, Nb, K, Ca, Y, and Zr.

[0109] In Examples 1 to 6, the second phase was present in an observation range S defined on the cross-section at a ratio of 8.8% to 60% relative to the entire area (100%) of the observation range S excluding the holes (see Table 3). In contrast, the dielectric compositions of Comparative Examples 1 to 4 contained no second phase, and therefore had an Sr concentration ratio of 0 (see Table 3).

[0110] In such Examples 1 to 6, the relative dielectric constant under high electric field (8 kV / mm) is greater than 900, and the reduction rate (change rate) of the relative dielectric constant before and after applying DC high voltage is greater than -41%, and the reduction amplitude of the relative dielectric constant is suppressed to a small level.

[0111] The dielectric composition of Comparative Example 1 showed a small relative dielectric constant under a high electric field (8 kV / mm). In addition, the dielectric composition of Comparative Example 1 showed a greater decrease in relative dielectric constant than those of Examples 1-6.

[0112] In addition, the dielectric compositions of Comparative Examples 2 to 4 had large relative permittivities under a high electric field (8 kV / mm), but the extent of decrease in relative permittivity was greater than that of Examples 1 to 6.

[0113] Note that, in the dielectric compositions of Examples 1 to 6, the concentration of Na contained in the second phase is 2.1 times or more and 2.5 times or less of the concentration of Na contained in the first phase, and the concentration of Sr contained in the second phase is 0.59 times or more and 0.63 times or less of the concentration of Sr contained in the first phase.

[0114] In particular, in Examples 3 to 6, within the observation range S defined on the cut surface, the second phase comprised a proportion of 8.8% to 32% of the entire area (100%) of the observation range S excluding the hole (see Table 3). In these Examples 3 to 6, the relative permittivity under a high electric field (8 kV / mm) was 1000 or higher, and the rate of decrease (rate of change) in the relative permittivity before and after application of a high DC voltage was -35% or higher, minimizing the decrease in the relative permittivity.

[0115] Explanation of symbols

[0116] 100…Dielectric ceramic (dielectric layer), 200…Dielectric element, 301, 302…Electrodes, 1…Laminated electronic component, 10…Laminated body, 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, 2…Dielectric composition, 20…Hole, 21…First phase, 22…Second phase.

Claims

1. A dielectric composition comprising: The first phase has a tungsten bronze type crystal structure containing at least Sr, Na, Nb, Ca, Y, and Zr; and The second phase has a perovskite-type crystal structure containing at least Sr, Na, Ca, Y, and Zr, wherein: In an observation range set on a cut surface of the dielectric composition, the second phase is contained at a ratio of 8.8% to 60% with respect to the entire area (100%) of the observation range excluding the holes.

2. The dielectric composition according to claim 1, wherein The concentration of Na contained in the second phase is 2.1 times or more and 2.5 times or less relative to the concentration of Na contained in the first phase, and The concentration of Sr contained in the second phase is 0.59 times or more and 0.63 times or less relative to the concentration of Sr contained in the first phase.

3. The dielectric composition according to claim 1 or claim 2, wherein: The second phase is contained in a ratio of 8.8% to 32% with respect to the entire area (100%) of the observation range excluding the holes. 4 . A dielectric element comprising a dielectric ceramic formed from the dielectric composition according to claim 1 , and an electrode mounted on the dielectric ceramic. 5 . A laminated electronic component comprising a laminate in which dielectric layers and internal electrode layers are alternately laminated, wherein the dielectric layers comprise the dielectric composition according to claim 1 .

Images