Dielectric composition and electronic component

Abstract

The present invention relates to a dielectric composition and an electronic component. The dielectric composition contains at least any one of barium and strontium and tantalum as a main component, and contains calcium and silicon as a subcomponent.

Description

Technical Field

[0001] This invention relates to a dielectric composition and an electronic component. Background Technology

[0002] For example, as shown in Patent Document 1, a dielectric composition with a high relative permittivity that does not contain lead or alkali metals has been developed.

[0003] However, the newly developed dielectric composition has the problem that high-density dielectrics cannot be obtained without high-temperature firing.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-103671 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] The present invention was made in view of the current situation, and its object is to provide a novel dielectric composition that can achieve high density even when fired at relatively low temperatures.

[0009] Means for solving technical problems

[0010] The dielectric composition of the present invention contains at least one of barium and strontium and tantalum as the main component, and contains calcium and silicon as secondary components.

[0011] The dielectric composition involved in this invention exhibits high density and a high relative permittivity even when sintered at relatively low temperatures. The reasons for this are as follows.

[0012] It is believed that by including calcium and silicon as byproducts in the dielectric composition according to the present invention, the elements constituting the main component become more mobile through the byproducts. As a result, it is believed that the density can be increased even when the dielectric composition is sintered at a relatively low temperature. In addition, the relative permittivity can also be increased.

[0013] The principal component preferably includes strontium.

[0014] Therefore, even when the dielectric composition is fired at a relatively low temperature, the density can be further increased, and the relative permittivity can be further increased.

[0015] The main components preferably include barium and strontium.

[0016] Therefore, even when the dielectric composition is fired at a relatively low temperature, the density can be further increased, and the relative permittivity can be further increased.

[0017] The secondary component preferably also includes barium.

[0018] Therefore, even when the dielectric composition is fired at a relatively low temperature, the density can be further increased, and the relative permittivity can be further increased.

[0019] When the total amount of the dielectric composition is set to 100 parts by mass,

[0020] The total content of calcium and silicon, when the atomic valence of calcium is set to 2 and the atomic valence of silicon is set to 4, is preferably 0.5 to 10 parts by mass when converted to oxides.

[0021] The principal component is preferably {Ba x Sr (1-x)} m Ta4O 12 This indicates that x is below 0.75. Consequently, the relative permittivity increases further, and the density also increases further. Furthermore, the resistivity increases, and the dielectric loss decreases.

[0022] m is preferably 1.8 to 2.2. As a result, the relative permittivity becomes higher, the density and resistivity become higher, and the dielectric loss becomes lower.

[0023] The crystal system of the main component is preferably tetragonal.

[0024] The dielectric composition involved in this invention is preferably substantially free of niobium, alkali metals and lead.

[0025] Furthermore, the electronic component according to the present invention comprises the above-described dielectric composition. Attached Figure Description

[0026] Figure 1 This is a schematic cross-sectional view of a multilayer ceramic capacitor according to one embodiment of the present invention.

[0027] Explanation of symbols:

[0028] 1…Laminated ceramic capacitors

[0029] 10…Component Body

[0030] 2…Dielectric layer

[0031] 3…Inner Electrode Layer

[0032] 4…External electrode. Detailed Implementation

[0033] < Multilayer ceramic capacitors >

[0034] exist Figure 1 The image shows a multilayer ceramic capacitor 1, which is an example of an electronic component according to this embodiment. The multilayer ceramic capacitor 1 has a component body 10 formed by alternating layers of dielectric layers 2 and internal electrode layers 3. A pair of external electrodes 4 are formed at both ends of the component body 10, respectively communicating with the internal electrode layers 3 alternately arranged inside the component body 10. The shape of the component body 10 is not particularly limited, and it is usually made into a cuboid shape. Furthermore, the size of the component body 10 is not particularly limited, and can be set to an appropriate size according to the application.

[0035] < Dielectric layer >

[0036] The dielectric layer 2 is composed of the dielectric composition of this embodiment, which will be described later.

[0037] The thickness of each layer of dielectric layer 2 (interlayer thickness) is not particularly limited and can be set according to desired characteristics, applications, etc. Generally, the interlayer thickness is preferably 30 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

[0038] < Internal electrode layer >

[0039] In this embodiment, the internal electrode layer 3 is stacked in such a way that each end is alternately exposed on the surfaces of two opposite end faces of the element body 10.

[0040] The conductive material contained in the internal electrode layer 3 is not particularly limited. Examples of noble metals used as conductive materials include palladium, platinum, and silver-palladium alloys. Examples of base metals used as conductive materials include nickel, nickel alloys, copper, and copper alloys. Furthermore, nickel, nickel alloys, copper, or copper alloys may contain trace amounts of phosphorus and / or sulfur, approximately 0.1% by mass or less. Additionally, the internal electrode layer 3 can be formed using commercially available electrode paste. The thickness of the internal electrode layer 3 can be appropriately determined based on the intended application.

[0041] < external electrodes >

[0042] There are no particular limitations on the conductive material contained in the external electrode 4. For example, known conductive materials such as nickel, copper, tin, silver, palladium, platinum, gold, or their alloys, or conductive resins can be used. The thickness of the external electrode 4 can be appropriately determined according to the application and other factors.

[0043] < Dielectric composition >

[0044] The dielectric composition constituting the dielectric layer 2 in this embodiment contains at least one of barium and strontium and tantalum as main components.

[0045] The main component of the dielectric composition of this embodiment preferably includes strontium, and more preferably includes both strontium and barium.

[0046] The main component of the dielectric composition in this embodiment is {Ba x Sr (1-x)} m Ta4O 12 express.

[0047] x is preferably below 0.75.

[0048] m is preferably 1.8 to 2.2, and more preferably 1.9 to 2.1.

[0049] The crystal system of the main component of the dielectric composition in this embodiment is not particularly limited, but it is preferably tetragonal or orthorhombic, and more preferably tetragonal.

[0050] Furthermore, the main component refers to the component that accounts for 80 to 100 moles when the element other than oxygen contained in the dielectric composition is set to 100 moles, preferably 90 to 100 moles.

[0051] Furthermore, the dielectric composition of this embodiment is substantially free of niobium, alkali metals, and lead. "Substantially free of niobium, alkali metals, and lead" means that when the elements other than oxygen contained in the dielectric composition are set to 100 molar parts, the total amount of "niobium, alkali metals, and lead" is 10 molar parts or less, preferably 5 molar parts or less.

[0052] The dielectric composition of this embodiment contains calcium and silicon as byproducts. Additionally, barium is preferably also included as a byproduct.

[0053] When the total amount of the dielectric composition is set to 100 parts by mass, in this embodiment, the total amount of calcium and silicon contained in the dielectric composition is preferably 0.5 to 10 parts by mass when the atomic valence of calcium is set to 2 and the atomic valence of silicon is set to 4, and more preferably 1 to 5 parts by mass when converted to oxides.

[0054] The ratio of the amount (moles) of calcium contained in the dielectric composition of this embodiment to the amount (moles) of silicon contained in the dielectric composition is preferably 0.12 to 1.1, more preferably 0.22 to 0.88.

[0055] In addition to the main and secondary components described above, the dielectric composition of this embodiment may also contain vanadium, titanium, aluminum, magnesium, manganese, chromium, rare earth elements, etc.

[0056] < Manufacturing method of multilayer ceramic capacitors >

[0057] Next, regarding Figure 1An example of the manufacturing method of the multilayer ceramic capacitor 1 shown will be described.

[0058] In this embodiment, powders of the main component and powders of the secondary component constituting the above-described dielectric composition are prepared separately. The method for preparing the powder of the main component is not particularly limited, and it can be prepared by a solid-state reaction method such as calcination. The raw materials for each element used as the powder of the main component or the powder of the secondary component are not particularly limited, and oxides of each element can be used. Furthermore, various compounds in which oxides of each element can be obtained by calcination can be used.

[0059] In this embodiment, barium may also be included as a secondary component. By including barium in the powder of the secondary component, barium becomes more readily present at grain boundaries. The ratio of the amount (moles) of barium contained in the secondary component to the amount (moles) of silicon contained in the secondary component (hereinafter referred to as "Ba / Si") is preferably 0.12 to 1.1, more preferably 0.22 to 0.88.

[0060] After weighing the raw materials of the main component powder and the secondary component powder in a specified ratio, they are wet-mixed using a ball mill or similar equipment for a specified time. The mixed powder is then dried and heat-treated in air at a temperature ranging from 700 to 1300°C to obtain calcined powders of the main and secondary components. Alternatively, the calcined powder can be pulverized using a ball mill or similar equipment for a specified time.

[0061] Next, a paste for fabricating the raw chip is prepared. The calcined powders of the obtained main and secondary components are mixed with a solvent and coated to prepare a paste for the dielectric layer. Known adhesives and solvents can be used.

[0062] The paste for dielectric layers may also contain additives such as plasticizers and dispersants as needed.

[0063] The paste for the internal electrode layer is obtained by mixing the raw materials of the aforementioned conductive material, binder, and solvent. Commonly known binders and solvents can be used. The paste for the internal electrode layer may contain additives such as commonly used materials and plasticizers, as needed.

[0064] The paste for the external electrode layer can be prepared in the same way as the paste for the internal electrode layer.

[0065] The obtained pastes are used to form green sheets and internal electrode patterns, which are then stacked to obtain a green chip.

[0066] The obtained green chip is then subjected to a binder removal process as needed. The binder removal process is preferably carried out at a holding temperature of 200–350°C.

[0067] After the binder is removed, the green chip is fired to obtain the device body 10. In this embodiment, the firing atmosphere is not particularly limited and can be in air or a reducing atmosphere. In this embodiment, the holding temperature during firing is, for example, 1250 to 1455°C.

[0068] After firing, the resulting component body 10 is subjected to re-oxidation treatment (annealing) as needed. As for annealing conditions, for example, it is preferable to set the oxygen partial pressure during annealing to be higher than the oxygen partial pressure during firing, and to set the holding temperature to 1150°C or below.

[0069] The dielectric composition of the dielectric layer 2 constituting the main body 10 obtained as described above is the aforementioned dielectric composition. The main body 10 is subjected to end face grinding, and an external electrode paste is applied and welded to form an external electrode 4. Then, as needed, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

[0070] Thus, the multilayer ceramic capacitor 1 of this embodiment is manufactured.

[0071] In this embodiment, by including calcium and silicon as byproducts in the dielectric composition, a high-density dielectric composition can be achieved even when sintered at a relatively low temperature. The reasons for this are as follows.

[0072] It is believed that by including calcium and silicon as byproducts in the dielectric composition of this embodiment, the elements constituting the main component become more mobile through the byproducts. As a result, it is believed that the dielectric composition of this embodiment can increase density even when sintered at a relatively low temperature. In addition, the relative permittivity can also be increased.

[0073] Furthermore, it is believed that by including barium as a secondary component, the elements constituting the main component become more mobile via the secondary component. As a result, it is thought that even with firing at relatively low temperatures, the density and relative permittivity can be further improved.

[0074] Furthermore, according to this embodiment, by containing at least one selected from barium and strontium, and tantalum as the main component, a dielectric composition with a constant and high relative permittivity over a wide temperature range can be obtained. Specifically, the dielectric composition according to this embodiment exhibits a relative permittivity of 35 or higher in a temperature range of -55 to 150°C, and a relative permittivity of 33 or higher in a temperature range of -70 to 180°C.

[0075] Furthermore, according to the dielectric composition of this embodiment, setting the reference temperature to 25°C within a temperature range of -55 to 150°C enables a capacitance change rate within ±22%, thus satisfying the X8S characteristic. Further, setting the reference temperature to 25°C within a temperature range of -70 to 180°C enables a capacitance change rate within ±22%.

[0076] Furthermore, according to this embodiment, it is possible to obtain a dielectric composition that is substantially free of niobium, alkali metals, and lead, and exhibits high density, high relative permittivity, low dielectric loss, and high resistivity.

[0077] Examples of dielectric compositions exhibiting high relative permittivity include (Sr,Ba)Nb2O6, which is mainly composed of niobium; (Na,K)NbO3, which contains alkali metals; and Pb(Zr,Ti)O3, which contains lead.

[0078] The dielectric composition of this embodiment, which contains tantalum but is substantially free of niobium, tends to exhibit a high relative permittivity, low dielectric loss, and high resistivity compared to existing dielectric compositions that contain niobium but are free of tantalum. This is because tantalum oxide is considered less prone to oxygen vacancies than niobium oxide.

[0079] Dielectric properties are properties predicated on the insulator. Therefore, a high resistivity is required in the dielectric composition to prevent it from becoming semiconductor or conductor-like. Furthermore, as mentioned above, tantalum oxide is less prone to oxygen vacancies compared to niobium oxide. In other words, changes in valence state can be suppressed. Therefore, it is believed that because it is sintered simultaneously with a base metal, even during reduction sintering, the valence state is less likely to change, the decrease in resistivity is suppressed, and a high resistivity can be exhibited over a wide temperature range. Additionally, for the same reason, it is believed that low dielectric loss can be exhibited.

[0080] Furthermore, the dielectric composition of this embodiment is substantially free of alkali metals, thus preventing fluctuations in the composition of the dielectric composition or furnace contamination caused by the evaporation of alkali metals.

[0081] Furthermore, while RoHS (Restriction of Hazardous Substances Directive) and other directives restrict the use of lead, the dielectric composition of this embodiment is substantially lead-free.

[0082] The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments and can be implemented in various different ways without departing from the spirit of the present invention.

[0083] In the above embodiments, the case where the electronic component of the present invention is a multilayer ceramic capacitor has been described. However, the electronic component of the present invention is not limited to a multilayer ceramic capacitor, and any electronic component having the above-described dielectric composition is acceptable.

[0084] For example, it could also be a single-plate ceramic capacitor in which a pair of electrodes are formed on a single-layer dielectric substrate made of the above-described dielectric composition.

[0085] In addition to capacitors, the electronic components of the present invention can also be filters, duplexers, resonators, transmitters, and antennas.

[0086] Example

[0087] The present invention will now be described in more detail using examples and comparative examples. However, the present invention is not limited to the following examples.

[0088] [ Experiment 1 ]

[0089] < Sample numbers 1-3, 11-13, 21-23, 31-33, 41-44, 51-54 >

[0090] Barium carbonate, strontium carbonate, and tantalum oxide powders were prepared as starting materials for the main components of the dielectric composition. The starting materials for the main components were weighed in accordance with the composition of the main components after calcination as described in Tables 1 to 3.

[0091] In addition, raw material powders for each of the by-products listed in Tables 1 to 3 were prepared as starting materials for the by-products of the dielectric composition. The prepared starting materials for the by-products were weighed according to the method described in Tables 1 to 3, with the content of the by-products after calcination being the same. Furthermore, "content of by-products" refers to "the content of the elements constituting the by-products converted to oxides when the total amount of the dielectric composition is set to 100 parts by mass." In this case, the valence of barium was set to 2, the valence of calcium was set to 2, the valence of silicon was set to 4, and the valence of magnesium was set to 2, and oxide conversions were performed.

[0092] Specifically, in samples 2, 12, and 22, calcium carbonate and silicon dioxide were prepared as starting materials for the by-products. In samples 2, 12, and 22, the molar ratio of calcium to silicon in the by-products (hereinafter referred to as "Ca / Si") was set to 0.42.

[0093] In addition, barium carbonate, calcium carbonate, and silicon oxide were prepared as starting materials for samples 3, 13, and 23 as by-products. In samples 3, 13, and 23, the Ba / Si ratio was set to 0.58, and the Ca / Si ratio was set to 0.42.

[0094] Next, the weighed powders were wet-mixed using ion-exchanged water as the dispersion medium in a ball mill, and the mixture was dried to obtain a mixed raw material powder. Subsequently, the obtained mixed raw material powder was heat-treated in air at a temperature of 900°C for 2 hours to obtain calcined powders of the main component and secondary components.

[0095] The calcined powders of the main and secondary components were wet-milled using ion-exchange water as the dispersion medium in a ball mill and then dried to obtain the dielectric raw material.

[0096] To 100 parts by mass of the obtained dielectric raw material, 10 parts by mass of an aqueous solution containing 6 parts by mass of polyvinyl alcohol resin as a binder are added, and granulation is performed to obtain granulated powder.

[0097] The obtained granulated powder is added to The mold, at 0.6 ton / cm 2 Pre-compression molding is performed under pressure, followed by compression molding at 1.2 ton / cm. 2 The pressure is used for main compression molding to obtain a disc-shaped generated body.

[0098] Next, the obtained prototyping body is subjected to debinding, firing, and annealing under the following conditions to obtain the component body.

[0099] The adhesive removal treatment conditions were set as follows: temperature: 400℃, temperature holding time: 2 hours, atmosphere: air.

[0100] Firing conditions were set as follows: holding temperature: 1340℃, holding time: 2 hours, atmosphere: humidified N2+H2 mixture (oxygen partial pressure 10). -12 (MPa). In addition, a humidifier is used to humidify the atmosphere gas during firing.

[0101] Annealing conditions are set as follows: holding temperature: 1050℃, holding time: 2 hours, atmosphere: humidified N2 gas (oxygen partial pressure: 10). -7 (MPa). In addition, a humidifier is used to humidify the atmosphere gas during annealing.

[0102] The density and relative permittivity of the obtained sintered body (dielectric composition) were investigated by the following method. Furthermore, to determine the relative permittivity, an In-Ga electrode was coated onto the aforementioned dielectric composition (sintered body) to obtain a disc-shaped ceramic capacitor sample (capacitor sample).

[0103] < density >

[0104] The density of the dielectric composition was determined as follows. First, the volume V of the dielectric composition was calculated. Next, the mass m of the disk-shaped dielectric composition was measured, and m / V was calculated to obtain the density of the dielectric composition. The results are shown in Tables 1 to 3.

[0105] < Relative permittivity >

[0106] For the capacitor sample, the capacitance C was measured at room temperature (20°C) using a digital LCR meter (YHP 4284A) with an input frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms. Then, the relative permittivity was calculated based on the thickness of the sintered body, the effective electrode area, and the capacitance C obtained from the measurement. The results are shown in Tables 1 to 3.

[0107] [Table 1]

[0108]

[0109] [Table 2]

[0110]

[0111] [Table 3]

[0112]

[0113] According to Table 1, when calcium and silicon are present as byproducts (samples 2, 3, 12, 13, 22, 23), high density and high relative permittivity can be confirmed compared with other cases (samples 1, 11, 21, 31-33).

[0114] According to Table 2, when the calcium and silicon content is converted to oxides as 0.5 to 10 parts by mass (sample numbers 12, 41 to 44), it is confirmed to have high density and high relative permittivity. When the calcium and silicon content is converted to oxides as 1 to 5 parts by mass (sample numbers 12, 42 and 43), it is confirmed to have even higher density and even higher relative permittivity.

[0115] According to Table 3, the high density and high relative permittivity were confirmed when the Ca / Si ratio was 0.12 to 1.1 (sample numbers 12 and 51 to 54), and the higher density and higher relative permittivity were confirmed when the Ca / Si ratio was 0.22 to 0.88 (sample numbers 12, 52 and 53).

[0116] Furthermore, in this embodiment, silicon and calcium are not present except for the by-products. Therefore, "the case where Ca / Si is 0.12 to 1.1" (sample numbers 12 and 51 to 54) refers to "the case where the ratio of the amount (moles) of calcium contained in the dielectric composition to the amount (moles) of silicon contained in the dielectric composition is 0.12 to 1.1" (sample numbers 12, 51 to 54). Similarly, "the case where Ca / Si is 0.22 to 0.88" (sample numbers 12, 52 and 53) refers to "the case where the ratio of the amount (moles) of calcium contained in the dielectric composition to the amount (moles) of silicon contained in the dielectric composition is 0.22 to 0.88" (sample numbers 12, 52 and 53).

[0117] [ Experiment 2 ]

[0118] < Sample numbers 61-63, 71, 72 >

[0119] For samples 61–63, 71, and 72, the dielectric compositions were obtained in the same manner as in Experiment 1, except that the composition and amount of the starting materials for the dielectric composition were as described below. The density and relative permittivity were then investigated. The density and relative permittivity of each sample are shown in Tables 4 and 5.

[0120] That is, in Experiment 2, barium carbonate, strontium carbonate, and tantalum oxide powders were prepared as the starting materials for the main components of the dielectric composition. The calcined main components {Ba x Sr (1-x)} m Ta4O 12 The starting materials for the main components are weighed and prepared as shown in Table 4 or Table 5.

[0121] In addition, the byproducts are calcium and silicon, with a Ca / Si ratio of 0.42. Furthermore, when the total amount of the dielectric composition is set to 100 parts by mass, the content of the byproducts is converted to 3 parts by mass in terms of oxides.

[0122] [Table 4]

[0123]

[0124] [Table 5]

[0125]

[0126] According to Tables 4 and 5, in the principal components with {Ba x Sr (1-x)} m Ta4O 12It is confirmed that high density and high relative permittivity are achieved when x is less than 0.75 (sample numbers 12, 22, 61 to 63) and m is between 1.90 and 2.10 (sample numbers 12, 71 and 72).

Claims

1. A dielectric composition, wherein, at least any one of barium and strontium and tantalum are contained as a main component, calcium and silicon are contained as a sub component, The main component is represented by {Ba x Sr (1-x)} m Ta4O 12 ​ x is 0.75 or less, m is 1.8 to 2.2, when the total amount of the dielectric composition is set to 100 parts by mass, the total amount of calcium and silicon contained in the dielectric composition is 0.5 to 10 parts by mass in terms of oxides when the valence of calcium is set to 2 and the valence of silicon is set to 4, the molar ratio of calcium contained in the dielectric composition with respect to silicon contained in the dielectric composition is 0.12 to 1.

1.

2. The dielectric composition according to claim 1, wherein, the main component includes barium and strontium.

3. The dielectric composition according to claim 1, wherein, the sub component further includes barium.

4. An electronic component, wherein, the dielectric composition according to any one of claims 1 to 3 is provided.

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