JP7765302B2 - Dielectric composition and electronic component - Google Patents

Description

The present invention relates to a dielectric composition and an electronic component.

Patent Document 1 discloses a dielectric composition whose main component is a tungsten bronze-type composite oxide represented by the chemical formula _BaαR ( _{Ti1.00- xZrx} ) _2.00 ( _{Nb1.00- yTay} ) _{3.00O13.00 + α} , and whose minor components are V, W, and Si and/or Ge.

In recent years, there has been a demand for dielectric compositions containing the above main components that can achieve higher sintered densities even when fired at low temperatures.

Patent No. 6922701

The present invention was made in consideration of these circumstances, and aims to provide a dielectric composition that has a high sintered density, a high dielectric constant, and good temperature characteristics of capacitance even when fired at a relatively low temperature.

The dielectric composition according to the present invention includes a main component and a first subcomponent,
the main component is a tungsten bronze-type composite oxide represented by Ba _α R{Ti _(1.00-x) Zr _x } _2.00 {Nb _(1.00-y) Ta _y } _3.00 O _{13.00+ α} ,
R is a rare earth element,
The α is 2.05≦α≦2.25,
The x is 0.40≦x≦1.00,
The y is 0.05≦y≦0.85,
the first minor component is Mg and Si,
The content of Si in the dielectric composition in terms of SiO ₂ relative to 100 molar parts of the main component is defined as CSi molar parts,
When the content of Mg in terms of MgO relative to 100 parts by mole of the main component in the dielectric composition is expressed as CMg parts by mole,
CMg/CSi is 0.75≦CMg/CSi≦2.0,
CMg+CSi is 15≦CMg+CSi≦30.

The dielectric composition of the present invention has a high sintered density, a high dielectric constant, and good temperature characteristics of capacitance, even when fired at a relatively low temperature. The reasons for this are not entirely clear, but the following is thought to be the case. It is believed that the effect of lowering the sintering start temperature is achieved by having α, x, and y within the above ranges and the dielectric composition containing predetermined amounts of both Si and Mg. This makes it easier to achieve a high sintered density even when fired at a relatively low temperature, improves the dielectric constant, and improves the temperature characteristics of capacitance.

As such, the dielectric composition according to this embodiment exhibits excellent characteristics in the high-temperature range, making it suitable for use in the operating temperature range (-55°C to 250°C) of SiC and GaN-based power devices. It can also be used effectively as an electronic component for noise removal in harsh environments such as automobile engine compartments.

The dielectric composition according to the present invention preferably contains a second subcomponent,
the second minor component is Al,
When the content of Al in terms of Al ₂ O ₃ relative to 100 parts by mole of the main component in the dielectric composition is expressed as CAl parts by mole,
It is preferred that CAl is within the range of 2.5-10.

By including the second minor component in the dielectric composition within the above range, the sintering initiation temperature is further reduced. This further improves the sintered density and improves the temperature characteristics of the capacitance. Furthermore, by including the second minor component in the dielectric composition within the above range, the effect of improving reduction resistance is obtained. As a result, the resistivity is improved.

The dielectric composition according to the present invention preferably contains a third subcomponent,
the third minor component is at least one selected from the group consisting of Ho, Eu, Nd, Yb, and Gd;
The content of Ho in the dielectric composition calculated as Ho ₂ O ₃ relative to 100 parts by mole of the main component is defined as CHO parts by mole,
The content of Eu in the dielectric composition calculated as _Eu2O3 relative to 100 parts by _mole of the main component is defined as CEu parts by mole,
The content of Nd in the dielectric composition calculated as _Nd2O3 relative to ₁₀₀ molar parts of the main component is defined as CNd molar parts,
The content of Yb in the dielectric composition calculated as _Yb2O3 relative to ₁₀₀ molar parts of the main component is defined as CYb molar parts,
When the content of Gd in terms of _Gd2O3 relative to 100 parts by _mole of the main component in the dielectric composition is expressed as CGd parts by mole,
It is preferred that at least one selected from the group consisting of CHo, CEu, CNd, CYb and CGd is included within the range of 2.5 to 10.

By including the third minor component in the dielectric composition within the above range, the effect of improving reduction resistance is further achieved. As a result, the resistivity is further improved.

It is preferable that R is La.

Furthermore, the electronic component according to the present invention comprises the above-mentioned dielectric composition.

Furthermore, a laminated electronic component according to the present invention is a laminated electronic component in which dielectric layers and internal electrode layers are alternately laminated,
The dielectric layer is the above-described dielectric composition.

FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a thin film capacitor according to one embodiment of the present invention. FIG. 3 is a graph relating to an example of the present invention and a comparative example.

[First embodiment]
< Multilayer ceramic capacitors >
The multilayer ceramic capacitor 1, which is one type of multilayer electronic component according to this embodiment, has a capacitor element body 10 configured such that dielectric layers 2 and internal electrode layers 3 are alternately laminated.

A pair of external electrodes 4 are formed on both ends of the capacitor element body 10, and are electrically connected to the internal electrode layers 3 arranged alternately inside the capacitor element body 10.

The capacitor element body 10 may have any shape, but is typically rectangular. Its dimensions may also be any, and may be set to an appropriate size depending on the application. The portion where the dielectric layers 2 and internal electrode layers 3 are alternately stacked is referred to as the laminated portion.

The internal electrode layers 3 are stacked so that their ends are alternately exposed on the surfaces of the two opposing end faces of the capacitor element body 10. A pair of external electrodes 4 are formed on both end faces of the capacitor element body 10 and are connected to the exposed ends of the alternately arranged internal electrode layers 3 to form a capacitor circuit.

The thickness of the dielectric layer 2 is arbitrary, but is preferably 100 μm or less per layer, and more preferably 30 μm or less. The lower limit of the thickness is arbitrary, but is, for example, approximately 0.5 μm.

The number of dielectric layers 2 stacked is optional, but it is preferable that it be 20 or more, and more preferably 50 or more.

The type of conductive material contained in the internal electrode layer 3 is arbitrary. Ni, a Ni-based alloy, Cu, or a Cu-based alloy is preferred. Ni or a Ni-based alloy is more preferred. Even more preferably, the main component of the internal electrode layer 3 is Ni or a Ni-based alloy, with one or more secondary components selected from Al, Si, Li, Cr, and Fe. The main component of the internal electrode layer 3 refers to a component contained in an amount of 85% by mass or more of the entire internal electrode layer 3.

By making the main component of the internal electrode layer 3 Ni or a Ni-based alloy and including one or more of Al, Si, Li, Cr, and Fe as secondary components, the Ni contained in the internal electrode layer 3 is less likely to oxidize. This also makes it less likely that the continuity and conductivity of the internal electrode layer 3 will deteriorate due to oxidation, even when the multilayer ceramic capacitor 1 is continuously used at high temperatures of around 250°C.

The internal electrode layer 3 may contain trace elements such as P at approximately 0.1% by mass or less. The internal electrode layer 3 may also be formed using commercially available electrode paste. The thickness of the internal electrode layer 3 may be determined appropriately depending on the application, etc.

The conductive material contained in the external electrode 4 is arbitrary. In this embodiment, for example, inexpensive Ni or Cu, highly heat-resistant Au, Ag or Pd, or an alloy of Ni, Cu, Au, Ag and/or Pd can be used. The thickness of the external electrode 4 can be determined appropriately depending on the application, etc., but is typically preferably around 10 to 50 μm.

Next, we will explain the dielectric composition that constitutes the dielectric layer 2 in this embodiment.

The dielectric composition according to this embodiment is mainly composed of a tungsten bronze type composite oxide represented by _BaαR {Ti _{(1.00-x) Zrx} } _2.00 {Nb _{(1.00-y) Tay} } _{3.00O13.00 + α} .

R is a rare earth element. The type of R is arbitrary, but it is preferable to use La as R. Using La as R makes it easier to obtain uniform sintered particles. Furthermore, the La content relative to the entire R is preferably 50 mol % or more, and it is most preferable for R to consist essentially of La alone. R consisting essentially of La alone means that the La content relative to the entire R is 95 mol % or more.

α represents the Ba content. In this embodiment, α is in the range of 2.05≦α≦2.25, and preferably 2.10≦α≦2.20.

x represents the Zr content. In this embodiment, x is in the range of 0.40≦x≦1.00, and preferably 0.60≦x≦0.80.

y represents the Ta content. In this embodiment, y is in the range of 0.05≦y≦0.85.

The dielectric composition according to this embodiment contains a first minor component. The first minor component is Mg and Si.

The content of Si in terms of _SiO2 per 100 molar parts of the main component in the dielectric composition is defined as CSi molar parts, and the content of Mg in terms of MgO per 100 molar parts of the main component in the dielectric composition is defined as CMg molar parts.

In this embodiment, CMg/CSi is 0.75≦CMg/CSi≦2.0.

Also, CMg + CSi is 15≦CMg + CSi≦30.

The dielectric composition according to the present invention preferably contains a second minor component. The second minor component is Al.

The content of Al in terms of Al ₂ O ₃ relative to 100 parts by mole of the main component in the dielectric composition is defined as CAl parts by mole.

In this embodiment, it is preferable that CAl be within the range of 2.5 to 10.

The dielectric composition according to the present invention preferably contains a third minor component. The third minor component is at least one selected from the group consisting of Ho, Eu, Nd, Yb, and Gd. In other words, the third minor component may be a single component or a combination of two or more components.

The content of Ho in terms of _Ho2O3 relative to 100 _molar parts of the main component in the dielectric composition is defined as CHo _molar parts. The content of Eu in terms of _Eu2O3 relative to 100 molar parts of the main component in the dielectric composition is defined as CEu molar parts. The content of Nd in terms of _Nd2O3 relative to 100 molar parts of the main _component in the dielectric composition is defined as CNd molar parts. The content of Yb in terms of _Yb2O3 relative to 100 molar parts of the main component in the dielectric composition is defined as CYb molar parts. The content of Gd in terms of _Gd2O3 relative to _{100 molar} parts of the main component in the dielectric composition is defined as CGd molar parts.

In this embodiment, it is preferable that at least one selected from the group consisting of CHo, CEu, CNd, CYb, and CGd is included in the range of 2.5 to 10.

The dielectric composition according to this embodiment is composed mainly of main phase particles made up of the main component and grain boundaries present between the main phase particles. The proportion of the main component in the main phase particles is, for example, 90 mass% or more on average. The particle size of the main phase particles is also optional. For example, it may be 0.5 μm or more and 2.0 μm or less on average.

In this embodiment, the first to third subcomponents may be solid-dissolved in the main phase particles, or may be present at the grain boundaries without being solid-dissolved in the main phase particles.

Furthermore, the dielectric composition according to this embodiment may contain trace impurities or subcomponents other than the first to third subcomponents, as long as they do not significantly deteriorate the temperature coefficient of capacitance. For example, the dielectric composition may contain Cr, Zn, Cu, Ga, etc. Therefore, the content of the main component relative to the entire dielectric composition is arbitrary. For example, the amount of elements other than oxygen that constitute the main component may be 65 mol % or more and 94.6 mol % or less of all elements other than oxygen that constitute the dielectric composition.

Next, an example of a manufacturing method for the multilayer ceramic capacitor 1 of this embodiment will be described. In the manufacturing method below, R is assumed to be La.

The multilayer ceramic capacitor 1 of this embodiment is manufactured in the same way as conventional multilayer ceramic capacitors, by creating a green chip using a paste by a standard printing method or sheet method, firing it, and then applying external electrodes and firing it again. The manufacturing method is described in detail below.

First, calcined powders of the main components are prepared. Powders of oxides and mixtures primarily composed of Ba, La, Zr, Nb, and Ta are prepared as starting materials for the main components. The average particle size of each powder is preferably 1.0 μm or less. It is also possible to mix and use compounds appropriately selected from various compounds that become the above-mentioned oxides upon firing, such as carbonates, oxalates, nitrates, hydroxides, and organometallic compounds. After weighing out the starting materials in the specified proportions, they are wet-mixed for a specified time using a ball mill or similar. After drying the mixed powder, it is heat-treated in air at 1000°C or less to obtain calcined powders of the main components.

Next, prepare the calcined powders of the minor components. For the first minor component, prepare Si oxide powder and Mg oxide powder with an average particle size of 2.0 μm or less as starting materials. Also, if necessary, prepare Al oxide powder with an average particle size of 2.0 μm or less as starting materials for the second minor component. Furthermore, if necessary, prepare Ho oxide powder, Eu oxide powder, Nd oxide powder, Yb oxide powder, and Gd oxide powder with an average particle size of 2.0 μm or less as starting materials for the third minor component.

These ingredients are weighed out in the specified proportions and then wet-mixed for a specified time using a ball mill or similar. Alternatively, various compounds that become the oxides mentioned above upon firing, such as carbonates, oxalates, nitrates, hydroxides, and organometallic compounds, can be selected and mixed appropriately. The mixed powder is then dried and heat-treated in air at 700°C to 800°C for 1 to 5 hours to obtain a calcined powder of the minor components. Alternatively, the dried mixed powder can be used without heat treatment.

Then, the resulting calcined powder of the main component and the calcined powder of the secondary component or the mixed powder of the secondary components are mixed and crushed to obtain the dielectric composition raw material. The average particle size of the dielectric composition raw material is optional. For example, it is 0.5 μm to 2.0 μm.

The obtained dielectric composition raw material is made into a paint to prepare a dielectric layer paste. The dielectric layer paste may be an organic paint made by kneading the dielectric composition raw material with an organic vehicle, or it may be a water-based paint.

An organic vehicle is a binder dissolved in an organic solvent. The type of binder used in the organic vehicle is arbitrary and may be appropriately selected from various binders commonly used in this technical field, such as ethyl cellulose and polyvinyl butyral. The type of organic solvent is also arbitrary. Depending on the method for manufacturing the multilayer ceramic capacitor (e.g., printing method or sheet method), it may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, and acetone.

If the dielectric layer paste is to be a water-based paint, the dielectric raw material can be kneaded with an aqueous vehicle in which a water-soluble binder and dispersant are dissolved in water. Any type of water-soluble binder can be used in the aqueous vehicle. For example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, etc. can be used.

The internal electrode layer paste is prepared by kneading the above-mentioned organic vehicle with conductive materials made from the various conductive metals and alloys, or various oxides, organometallic compounds, resinates, etc. that become the above-mentioned conductive materials after firing.

The paste for the external electrodes can be prepared in the same manner as the paste for the internal electrode layers described above.

There are no particular restrictions on the content of organic vehicles in each of the above pastes, and typical contents, such as approximately 1% to 5% by mass for binder and 10% to 50% by mass for solvent, may be used. Each paste may also contain additives selected from various dispersants, plasticizers, dielectric materials, insulating materials, etc., as needed. The total content of these is preferably 10% by mass or less.

Any type of dispersant can be used. For example, surfactant-type dispersants and polymer-type dispersants can be used. Any type of plasticizer can be used. For example, dioctyl phthalate and dibutyl phthalate can be used. Any type of dielectric material can be used _. For example, BaTiO3 _- based and CaZrO3 _- based materials can be used. Any type of insulator material can be used. For example, _Al2O3 and _SiO2 can be used.

When using the printing method, the dielectric layer paste and internal electrode layer paste are printed and laminated on a substrate such as PET, cut to the desired shape, and then peeled off from the substrate to form a green chip.

When using the sheet method, a green sheet is formed using the dielectric layer paste, and then the internal electrode layer paste is printed on top of this, and these are then stacked to form a green chip.

Before firing, the green chip may be subjected to a binder removal treatment. The conditions for the binder removal treatment are arbitrary. The temperature rise rate is preferably 5°C/hour to 300°C/hour, the holding temperature is preferably 180°C to 500°C, and the temperature holding time is preferably 0.5 hours to 24 hours. The atmosphere for the binder removal treatment is air or a reducing atmosphere. In the binder removal treatment described above, the method for humidifying _N2 gas or mixed gas is arbitrary. For example, a wetter or the like may be used. In this case, the water temperature is preferably about 5°C to 75°C.

The holding temperature during firing can be any temperature. Preferably, it is between 1100°C and 1400°C. By keeping the holding temperature within this range, the material is sufficiently densified, preventing breaks in the electrodes due to abnormal sintering of the internal electrode layers and preventing diffusion of the materials that make up the internal electrode layers, thereby suppressing a deterioration in the rate of capacity change. Furthermore, coarsening of the main phase particles can be prevented, improving the high-temperature load life.

The temperature rise rate during sintering is optional. Preferably, it is between 200°C/hour and 5000°C/hour. The temperature holding time during sintering and the cooling rate after sintering are optional. In order to control the particle size distribution of the main phase particles after sintering to within the range of 0.5 μm to 5.0 μm and to suppress volume diffusion between the main phase particles, the temperature holding time during sintering is preferably between 0.5 hours and 2.0 hours, and the cooling rate after sintering is preferably between 100°C/hour and 500°C/hour.

As the firing atmosphere, it is preferable to use a mixed gas of humidified N ₂ and H ₂ and to perform firing at an oxygen partial pressure of 10 ⁻² to 10 ⁻⁶ Pa.

After firing, the resulting capacitor element body is annealed as needed. The annealing conditions may be well-known. For example, it is preferable to set the oxygen partial pressure during annealing to a higher level than that during firing, and to maintain the temperature at 1000°C or lower.

In addition, in the above manufacturing method, the binder removal process, firing, and annealing process are performed independently, but they may also be performed consecutively.

The capacitor element body obtained as described above is subjected to end polishing, for example by barrel polishing or sandblasting, and then external electrode paste is applied and fired to form the external electrodes 4. If necessary, a coating layer is then formed on the surface of the external electrodes 4 by plating or other methods.

The dielectric composition according to this embodiment has a high sintered density, a high dielectric constant, and good temperature characteristics of capacitance, even when fired at a relatively low temperature, for example, between 1250°C and 1350°C, preferably between 1300°C and 1350°C. The reason for this is not entirely clear, but the following is thought to be the reason. With α, x, and y within the above ranges and the dielectric composition containing predetermined amounts of both Si and Mg, it is thought that the effect of lowering the sintering start temperature is achieved. This makes it easier to achieve a high sintered density even when fired at a relatively low temperature, improves the dielectric constant, and improves the temperature characteristics of capacitance.

Second Embodiment
< Thin film capacitor >
A schematic diagram of a thin film capacitor 11 according to this embodiment is shown in Fig. 2. The thin film capacitor 11 shown in Fig. 2 has a lower electrode 112 and a dielectric thin film 113 formed in this order on a substrate 111, and an upper electrode 114 on the surface of the dielectric thin film 113.

There are no particular restrictions on the material of the substrate 111, but using a silicon single crystal substrate as the substrate 111 is easy to obtain and cost-effective. If flexibility is important, nickel foil or copper foil can also be used as the substrate.

There are no particular restrictions on the materials for the lower electrode 112 and upper electrode 114, as long as they function as electrodes. Examples include platinum, silver, and nickel. There are no particular restrictions on the thickness of the lower electrode 112, and it is, for example, 0.01 to 10 μm. There are also no particular restrictions on the thickness of the upper electrode 114, and it is, for example, 0.01 to 10 μm.

The composition and crystal system of the main component of the dielectric composition that constitutes the dielectric thin film 113 in this embodiment are the same as those in the first embodiment.

There are no particular restrictions on the thickness of the dielectric thin film 113, but it is preferably between 10 nm and 1 μm.

Next, we will explain the manufacturing method of the thin-film capacitor 11.

There are no particular limitations on the method for forming the thin film that will ultimately become the dielectric thin film 113. Examples include vacuum evaporation, sputtering, pulsed laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), metal-organic decomposition (MOD), sol-gel deposition, and chemical solution deposition (CSD).

In addition, the raw materials used during film formation may contain trace impurities or secondary components, but this is not a problem as long as the amount is sufficient to not significantly impair the performance of the thin film. Furthermore, the dielectric thin film 113 according to this embodiment may also contain trace impurities or secondary components to the extent that it does not significantly impair performance.

In this embodiment, we will explain a film formation method using the PLD method.

First, a silicon single crystal substrate is prepared as the substrate 111. Next, SiO ₂ , TiO _x , and platinum are deposited in this order on the silicon single crystal substrate to form the platinum lower electrode 112. There are no particular limitations on the method for forming the lower electrode 112. Examples include sputtering and CVD.

Next, a dielectric thin film 113 is formed on the lower electrode 112 using the PLD method. Alternatively, a metal mask may be used to expose part of the lower electrode 112, leaving some areas uncovered by the thin film.

In the PLD method, a target containing the constituent elements of the desired dielectric thin film 113 is first placed in a film formation chamber. Next, a pulsed laser is irradiated onto the surface of the target. The intense energy of the pulsed laser instantly vaporizes the surface of the target. The evaporated material is then deposited on a substrate placed opposite the target, forming the dielectric thin film 113.

There are no particular restrictions on the type of target, and in addition to metal oxide sintered bodies containing the constituent elements of the dielectric thin film 113 to be produced, alloys and the like can be used. Furthermore, it is preferable that each element be evenly distributed in the target, but variations in distribution are acceptable as long as they do not affect the quality of the resulting dielectric thin film 113.

The number of targets does not necessarily have to be one; it is also possible to prepare multiple targets containing some of the constituent elements of the dielectric thin film 113 and use them for film formation. There are also no restrictions on the shape of the target, as long as it is a shape that is suitable for the film formation device being used.

When using the PLD method, it is preferable to heat the substrate 111 with an infrared laser during deposition in order to crystallize the dielectric thin film 113 being deposited. The heating temperature of the substrate 111 varies depending on the constituent elements and composition of the dielectric thin film 113 and the substrate 111, but for example, deposition is performed by heating to a temperature between 600°C and 800°C. By maintaining the appropriate temperature of the substrate 111, the dielectric thin film 113 is more likely to crystallize and cracks that occur during cooling can be prevented.

Finally, the thin-film capacitor 11 can be manufactured by forming the upper electrode 114 on the dielectric thin film 113. There are no particular restrictions on the material of the upper electrode 114, and silver, gold, copper, etc. can be used. There are also no particular restrictions on the method of forming the upper electrode 114. For example, it can be formed by vapor deposition or sputtering.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be embodied in a variety of different forms without departing from the spirit of the invention.

In the above-described embodiment, the electronic component according to the present invention is a multilayer ceramic capacitor. However, the electronic component according to the present invention is not limited to a multilayer ceramic capacitor and may be any electronic component that has the dielectric composition described above.

For example, it may be a single-plate ceramic capacitor in which a pair of electrodes is formed on a single-layer dielectric substrate made of the above-mentioned dielectric composition.

In addition to capacitors, the electronic components according to the present invention may also be filters, diplexers, resonators, oscillators, antennas, etc.

The present invention will be explained in more detail below using specific examples, but the present invention is not limited to these examples.

(Experimental Example 1)
First, powders of _BaCO3 , La(OH) ₃ , _TiO2 , _ZrO2 , _Ta2O5 , and _Nb2O5 , each with an average particle size of 1.0 μm or less, were prepared as starting materials for the main components _. These raw materials were weighed out so that the main component _BaαLa {Ti _{(1.00-x) Zrx} } _2.00 {Nb(1.00- _{y ) Tay} } _{3.00O13.00 + α} contained in the final dielectric composition would satisfy the α, x, and y values listed in Tables 1 to 3.

The mixture was then wet mixed in a ball mill for 24 hours using ethanol as a dispersion medium. The resulting mixture was then dried to obtain a mixed raw material powder. It was then heat-treated in air at a holding temperature of 900°C for 2 hours to obtain a calcined powder of the main component.

Next, MgO and _SiO2 powders were prepared as starting materials for the first subcomponent _{, Al2O3 was prepared as starting materials for the second subcomponent, and Ho2O3 , Eu2O3 , Nd2O3 , Yb2O3 , and Gd2O3} powders were prepared as starting materials for the _{third subcomponent} .

The average particle size of the starting material for the first minor component, the second minor component, and the third minor component was 0.2 μm or more and 2.0 μm or less.

These starting materials were weighed out to achieve the blending ratios shown in Tables 1 to 3. The contents of the first to third minor components shown in Tables 1 to 3 are expressed as the content in terms of the specified oxide per 100 molar parts of the main component.

The starting materials for each subcomponent were then wet-mixed for 24 hours in a ball mill using ethanol as a dispersion medium. The resulting mixture was then dried to obtain a mixed powder. This was then heat-treated in air at a holding temperature of 800°C for two hours to obtain a calcined powder of the subcomponents.

The calcined powder of the main component and the calcined powder of the subcomponent obtained by the above method were mixed and crushed to obtain a dielectric composition raw material. Next, 700 g of a solvent consisting of a toluene + ethanol solution (toluene:ethanol = 50:50 (weight ratio)), a plasticizer (dioctyl phthalate (DOP) (manufactured by J-Plus)), and a dispersant (Marialim AKM-0531 (manufactured by NOF Corp.)) mixed in a 90:6:4 (weight ratio) was added to 1,000 g of the dielectric composition raw material. The mixture was then dispersed for two hours using a basket mill to produce a dielectric layer paste. In all examples and comparative examples, the viscosity of the dielectric layer paste was adjusted to approximately 200 cps. Specifically, the viscosity was adjusted by adding a small amount of a toluene + ethanol solution.

As raw materials for the internal electrode layers, Ni with an average particle size of 0.2 μm, Al oxide with an average particle size of 0.1 μm or less, and Si oxide with an average particle size of 0.1 μm or less were prepared, and were weighed and mixed so that the total of Al and Si was 5 mass% relative to Ni. Then, the mixture was heat-treated in a humidified _N2 and _H2 mixed gas at 1200°C or higher, and crushed using a ball mill or the like to prepare a raw material powder with an average particle size of 0.20 μm.

100 parts by mass of the raw material powder, 30 parts by mass of an organic vehicle (8 parts by mass of ethyl cellulose resin dissolved in 92 parts by mass of butyl carbitol), and 8 parts by mass of butyl carbitol were kneaded using a three-roll mill to form a paste, yielding a paste for the internal electrode layers.

The dielectric layer paste was then applied to a PET film to form a green sheet. The thickness of the dried green sheet was adjusted to 10 μm. Next, a predetermined pattern of internal electrode layers was printed on the green sheet using the internal electrode layer paste. The green sheet was then peeled off from the PET film to produce a green sheet with the internal electrode layers printed in the predetermined pattern. Next, multiple green sheets with the internal electrode layers printed in the predetermined pattern were stacked and pressure-bonded to form a green laminate. The green laminate was then cut into a predetermined shape to obtain a green chip.

The resulting green chip was then subjected to binder removal, firing, and annealing processes to obtain a multilayer ceramic fired body. The conditions for binder removal, firing, and annealing are as follows. A wetter was used to humidify the atmospheric gas during the binder removal, firing, and annealing processes.

(Debinding treatment)
Heating rate: 100°C/hour Holding temperature: 400°C
Temperature retention time: 8.0 hours Atmospheric gas: Humidified _N2 and _H2 mixed gas

(Firing)
Heating rate: 500°C/hour Holding temperature: 1200°C to 1350°C Temperature holding time: 2.0 hours Cooling rate: 100°C/hour Atmospheric gas: Mixed gas of humidified _N2 and _H2 Oxygen partial pressure: ^10-5 to ^10-9 Pa

(Annealing treatment)
Holding temperature: 800°C to 1000°C Holding time: 2.0 hours Temperature increase and decrease rate: 200°C/hour Atmospheric gas: Humidified _N2 gas

The composition of the dielectric layers (dielectric compositions) of each of the obtained multilayer ceramic sintered bodies was analyzed using ICP atomic emission spectroscopy, and it was confirmed that they had substantially the same compositions as those listed in Tables 1 to 3. X-ray diffraction measurements were also performed, and the X-ray diffraction patterns confirmed that they had a tungsten bronze-type crystal structure.

The end faces of the obtained multilayer ceramic sintered bodies were polished by sandblasting, and then an In-Ga eutectic alloy was applied as an external electrode, resulting in multilayer ceramic capacitor samples with the same shape as the multilayer ceramic capacitor shown in Figure 1. The resulting multilayer ceramic capacitor samples all measured 3.2 mm x 1.6 mm x 1.2 mm, with dielectric layer thicknesses of 7 μm, internal electrode layers of 2 μm, and 50 dielectric layers sandwiched between the internal electrode layers.

The sintered density, dielectric constant, temperature change rate of capacitance, resistivity, DC withstand voltage, and high-temperature load life of the obtained multilayer ceramic capacitor samples were measured and evaluated using the methods described below, and the results are shown in Tables 1 to 3.

[Sintered density]
The sintered density of the dielectric composition was measured 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 the sintered density of the dielectric composition was obtained by calculating M/V. The results are shown in Tables 1 to 3.

[Dielectric constant at 250°C]
The capacitance of each multilayer ceramic capacitor sample was measured at 250°C using a digital LCR meter (YHP 4284A) with a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms. The dielectric constant (unitless) was calculated based on the thickness of the dielectric layer, the effective electrode area, and the capacitance obtained as a result of the measurement. A higher dielectric constant is preferable, and in this example, a value of 680 or higher was considered to be good.

[Temperature change rate of capacitance]
A multilayer ceramic capacitor sample was placed in a thermostatic chamber manufactured by Despatch, and the capacitance was measured at a measurement voltage of 1 Vrms over a temperature range of -55 to 250°C. The rate of change (ΔC _T /C ₂₅ (%)) of capacitance (C _T ) at temperature T (°C) relative to the capacitance (C 25 ) at + ₂₅ °C was calculated using the formula: ΔC _T /C ₂₅ = {(C _T - C ₂₅ )/C ₂₅ } × 100. The rate of change of capacitance was measured when T = -55°C and when T = 250°C. In this example, a rate of change of capacitance with temperature within ±15% at T = -55°C and T = 250°C was considered to have good temperature characteristics of capacitance, and a rate of change within ±10% was considered to have even better temperature characteristics of capacitance.

[Specific resistance at 250°C]
The insulation resistance of the multilayer ceramic capacitor samples was measured at 250°C using a digital resistance meter (R8340 manufactured by ADVANTEST) under conditions of a measurement voltage of 350 V (50 V/μm) and a measurement time of 60 seconds. The specific resistance was calculated from the measured insulation resistance value, the electrode area of the capacitor sample, and the thickness of the dielectric layer. A higher specific resistance is preferable.

From Tables 1 to 3, it was confirmed that when α was 2.05≦α≦2.25, x was 0.40≦x≦1.00, y was 0.05≦y≦0.85, CMg/CSi was 0.75≦CMg/CSi≦2.0, and CMg+CSi was 15≦CMg+CSi≦30 (sample numbers 4 to 8, 11 to 13, 15 to 18, 22 to 26, 30, 31, 33, and 37 to 58), the sintered density was 5.60 g/cm3 or ^more , the relative dielectric constant was 680 or more, and the rate of change of capacitance with temperature was within the range of ±15%.

From Table 3, it was confirmed that when CAl was within the range of 2.5 to 10 (sample numbers 39 to 42, 44 to 58), the resistivity was 3.2×10 ¹¹ Ωm or more and the temperature coefficient of capacitance was within the range of ±10%.

From Table 3, it was confirmed that when at least one selected from the group consisting of CHo, CEu, CNd, CYb and CGd was within the range of 2.5 to 10 (sample numbers 44 to 58), the resistivity was 5.5×10 ¹¹ Ωm or more.

(Experimental Example 2)
Multilayer ceramic capacitor samples were prepared and their properties were evaluated in the same manner as in Experimental Example 1, except that the compositions of the main component and the first subcomponent were as shown in Table 4 and the firing temperature was 1300°C or 1350°C. The results are shown in Table 4. The relative dielectric constant, resistivity, and temperature coefficient of capacitance shown in Table 4 were measured values of multilayer ceramic capacitor samples obtained at a firing temperature of 1350°C.

Figure 3 is a graph for each sample listed in Table 4. The x-axis of Figure 3 represents the firing temperature [°C], and the y-axis represents the sintered density [g/ ^cm3 ]. In Figure 3, ○ represents sample number 61, ◆ represents sample number 62, × represents sample number 63, ● represents sample number 64, ▲ represents sample number 65, ◇ represents sample number 66, and ■ represents sample number 67.

Table 4 and Figure 3 confirm that when α is 2.05≦α≦2.25, x is 0.40≦x≦1.00, y is 0.05≦y≦0.85, CMg/CSi is 0.75≦CMg/CSi≦2.0, and CMg+CSi is 15≦CMg+CSi≦30 (sample numbers 64-67), a high sintered density can be obtained not only when the firing temperature is set to 1350°C, but also when the firing temperature is set to 1300°C.

(Experimental Example 3)
Multilayer ceramic capacitor samples were prepared in the same manner as sample number 6, except that the types of rare earth elements were changed as shown in Table 5, and various properties were evaluated. The results are shown in Table 5 and FIG.

Table 5 confirms that changing the rare earth element R to Sm, Dy, Tb, Yb, or Nd provides the same effect as when the rare earth element R is La.

REFERENCE SIGNS LIST 1 multilayer ceramic capacitor 2 dielectric layer 3 internal electrode layer 4 external electrode 10 capacitor element body 11 thin film capacitor 111 substrate 112 lower electrode 113 polycrystalline dielectric thin film 114 upper electrode

Claims (6)

comprising a major component and a first minor component,
the main component is a tungsten bronze-type composite oxide represented by Ba _α R{Ti _(1.00-x) Zr _x } _2.00 {Nb _(1.00-y) Ta _y } _3.00 O _{13.00+ α} ,
R is a rare earth element,
The α is 2.05≦α≦2.25,
The x is 0.40≦x≦1.00,
The y is 0.05≦y≦0.85,
the first minor component is Mg and Si,
The content of Si in the dielectric composition in terms of SiO ₂ relative to 100 molar parts of the main component is defined as CSi molar parts,
When the content of Mg in terms of MgO relative to 100 parts by mole of the main component in the dielectric composition is expressed as CMg parts by mole,
CMg/CSi is 0.75≦CMg/CSi≦2.0,
A dielectric composition in which CMg+CSi satisfies 15≦CMg+CSi≦30. The dielectric composition includes a second subcomponent,
the second minor component is Al,
When the content of Al in terms of Al ₂ O ₃ relative to 100 parts by mole of the main component in the dielectric composition is expressed as CAl parts by mole,
2. The dielectric composition according to claim 1, wherein CAl is in the range of 2.5 to 10. The dielectric composition includes a third subcomponent,
the third minor component is at least one selected from the group consisting of Ho, Eu, Nd, Yb, and Gd;
The content of Ho in the dielectric composition calculated as Ho ₂ O ₃ relative to 100 parts by mole of the main component is defined as CHO parts by mole,
The content of Eu in the dielectric composition calculated as _Eu2O3 relative to 100 parts by _mole of the main component is defined as CEu parts by mole,
The content of Nd in the dielectric composition calculated as _Nd2O3 relative to ₁₀₀ molar parts of the main component is defined as CNd molar parts,
The content of Yb in the dielectric composition calculated as _Yb2O3 relative to ₁₀₀ molar parts of the main component is defined as CYb molar parts,
When the content of Gd in terms of _Gd2O3 relative to 100 parts by _mole of the main component in the dielectric composition is expressed as CGd parts by mole,
3. The dielectric composition according to claim 1, wherein at least one selected from the group consisting of CHo, CEu, CNd, CYb and CGd is contained within the range of 2.5 to 10. The dielectric composition according to any one of claims 1 to 3, wherein R is La. An electronic component comprising the dielectric composition according to any one of claims 1 to 4. A laminated electronic component in which dielectric layers and internal electrode layers are alternately laminated,
A laminated electronic component, wherein the dielectric layer is made of the dielectric composition according to any one of claims 1 to 4.