JP2018140891A - Dielectric composition and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric composition having high specific resistance under high electric field intensity when applied with a DC voltage while showing a high dielectric constant and an electronic component including a dielectric layer configured of the dielectric composition.SOLUTION: A dielectric composition of this invention includes a complex oxide as a main component, the complex oxide being represented by a composition formula: ABCOand having a rutile type crystal structure. In the formula, A is Ti and Sn; B is at least one element selected from among Al, Ga, In, Bi, and a rare earth element; C is at least one element selected from among Nb, Sb, Ta, and W; 0.10<α≤9.00, preferably 0.33≤α≤3.00, where α is a ratio of a Ti amount to a Sn amount in A; x>0; y>0; z>0; x+y+z=1.0000; 0.0050≤y+z≤0.2000; and 0.8000≤y/z≤1.2500, preferably 0.9000≤y/z≤1.1000.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a dielectric composition and an electronic component including a dielectric layer composed of the dielectric composition. In particular, the present invention relates to a dielectric composition suitable for a dielectric layer of an electronic component such as a multilayer ceramic capacitor or a thin film capacitor.

  As electronic components such as multilayer ceramic capacitors and thin film capacitors become smaller and have higher functionality, dielectric materials used for these dielectric layers include materials that exhibit a high relative dielectric constant and a low dielectric loss. Desired. Furthermore, since the DC voltage is applied to the electronic component during the operation of the electronic device on which these electronic components are mounted, the insulation and electrostatic property of the dielectric layer are maintained even under a high electric field strength caused by the DC voltage. It is necessary to maintain capacity.

At present, the relative dielectric constant of BaTiO ₃ -based dielectric compositions widely used as dielectric materials is about 500 to 6000, and the relative dielectric constant hardly exceeds 10,000. In addition, it is known that when a DC voltage is applied to a BaTiO ₃ -based dielectric composition, the relative dielectric constant rapidly decreases according to the magnitude of the voltage.

Various types of dielectric materials that are different from BaTiO ₃ -based dielectric materials and exhibit a high relative dielectric constant have been studied. For example, Patent Document 1 discloses that TiO ₂ having a rutile crystal structure is co-substituted with a +3 valent element A such as In or Ga and a +5 valent element B such as Nb or Ta (A ³⁺ , B ⁵⁺ ) A TiO ₂ based dielectric material is disclosed. According to Patent Document 1, this dielectric material uses an electron pinning defect dipole mechanism obtained by co-substituting a +3 valent element and a +5 valent element, and has a high relative dielectric constant exceeding 10,000 and a low dielectric constant. It is compatible with dielectric loss.

Patent Document 2 discloses a dielectric material in which Nb ₂ O ₅ is contained in TiO ₂ as a main component to make it a semiconductor and Bi ₂ O ₃ , CeO ₂ , and La ₂ Ti ₂ O ₇ are further contained. It is disclosed that this dielectric material also has both a huge relative dielectric constant exceeding 10,000 and low dielectric loss.

Special table 2014-531389 gazette JP-A-55-95204

  However, in the dielectric material described in Patent Document 1, since electrons are localized (pinned) using oxygen defects, a high DC voltage is applied to an electronic component including a dielectric layer using the dielectric material. When is applied, oxygen vacancies are easily moved, and localized electrons are easily hopped and the specific resistance is abruptly reduced. If the specific resistance when a DC voltage is applied decreases, the insulation of the dielectric layer when the DC voltage is applied cannot be maintained, and the relative dielectric constant cannot be measured when the DC voltage is applied.

Moreover, in the dielectric material described in Patent Document 2, Bi ₂ O ₃ , CeO ₂ , and La ₂ Ti ₂ O ₇ contained form a grain boundary having a high specific resistance, but the grain boundary itself Is extremely thin (for example, 10 nm or less), and therefore, when a high DC voltage is applied, there is a problem similar to that of Patent Document 1 in which dielectric breakdown occurs and specific resistance decreases rapidly.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a high specific resistance (for example, 5 V / min) even under a high electric field strength when a DC voltage is applied while exhibiting a high relative dielectric constant (for example, 10,000 or more). It is an object of the present invention to provide an electronic component including a dielectric composition having a thickness of 1.00 × 10 ¹⁰ Ωcm or more in μm and a dielectric layer composed of the dielectric composition.

In order to achieve the above object, the dielectric composition of the present invention comprises:
[1] represented by the composition formula _{A x B y C z O 2} + δ, comprise a composite oxide having a rutile-type crystal structure as a main component,
A is Ti and Sn;
B is one or more elements selected from the group consisting of Al, Ga, In, Bi and rare earth elements,
C is one or more elements selected from the group consisting of Nb, Sb, Ta and W,
When the ratio of Ti amount to Sn amount in A is α, 0.10 <α ≦ 9.00,
x, y and z are
x> 0, y> 0, z> 0,
x + y + z = 1.0000,
0.0050 ≦ y + z ≦ 0.2000,
0.8000 ≦ y / z ≦ 1.2500
A dielectric composition characterized by satisfying the following relationship:

  [2] The dielectric composition according to [1], wherein α satisfies a relationship of 0.33 <α ≦ 3.00.

  [3] The dielectric composition according to [1] or [2], wherein y and z satisfy a relationship of 0.9000 ≦ y / z ≦ 1.1000.

  [4] An electronic component comprising a dielectric layer containing the dielectric composition according to any one of [1] to [3].

Since the dielectric composition of the present invention has the above characteristics, it exhibits a high specific resistance (for example, 5 V / μm) even under a high electric field strength when a DC voltage is applied while exhibiting a high relative dielectric constant (for example, 10,000 or more). In addition, it is possible to provide an electronic component including a dielectric composition having 1.00 × 10 ¹⁰ Ωcm or more) and a dielectric layer made of the dielectric composition.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail in the following order based on specific embodiments.
1. Multilayer Ceramic Capacitor 1.1 Overall Configuration of Multilayer Ceramic Capacitor 1.2 Dielectric Layer 1.2.1 Dielectric Composition 1.3 Internal Electrode Layer 1.4 External Electrode 2. Manufacturing method of multilayer ceramic capacitor Effect in the present embodiment 4. Modified example

(1. Multilayer ceramic capacitor)
(1.1 Overall structure of multilayer ceramic capacitor)
As shown in FIG. 1, a multilayer ceramic capacitor 1 as an example of an electronic component according to this embodiment includes an element body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. At both ends of the element body 10, a pair of external electrodes 4 are formed which are electrically connected to the internal electrode layers 3 arranged alternately in the element body 10. Although there is no restriction | limiting in particular in the shape of the element main body 10, Usually, it is set as a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use.

(1.2 Dielectric layer)
The dielectric layer 2 is comprised from the dielectric composition which concerns on this embodiment mentioned later. As a result, the multilayer ceramic capacitor having the dielectric layer 2 exhibits a high specific resistance (for example, 5 V / μm) while exhibiting a high relative dielectric constant (for example, 10,000 or more) and a high electric field strength when a DC voltage is applied. 1.00 × 10 ¹⁰ Ωcm or more).

  The thickness per layer of the dielectric layer 2 (interlayer thickness) is not particularly limited, and can be arbitrarily set according to desired characteristics and applications. Usually, the interlayer thickness is preferably 100 μm or less, more preferably 30 μm or less. In the present embodiment, the lower limit of the interlayer thickness can be set to about 3.0 μm, for example, but it may be thinner than this. According to the dielectric composition according to the present embodiment, the above-described effects can be sufficiently obtained even when the interlayer thickness is in the above range.

  Further, the number of stacked dielectric layers 2 is not particularly limited, but in the present embodiment, it is preferably 20 or more, and more preferably 50 or more.

(1.2.1 Dielectric composition)
The dielectric composition according to the present embodiment contains a composite oxide having a rutile crystal structure as a main component. The composite oxide is represented by a composition formula A _x B _y C _z O _{2 + δ} and contains each metal element belonging to three groups represented by “A”, “B”, and “C” in the rutile crystal structure. Has been. In this embodiment, an element belonging to “B” and “C” is included in the oxide (AO ₂ ) of “A” that can take a rutile crystal structure, and a part of “A” is substituted. .

  In the composite oxide, the oxygen (O) amount may be a stoichiometric ratio, or may be slightly deviated from the stoichiometric ratio due to oxygen defects or the like. The amount of deviation from the stoichiometric ratio varies depending on the type of element to be substituted and the amount of substitution, and is represented by “δ” in the above composition formula.

  In the present embodiment, the three element groups (“A”, “B”, and “C”) are divided based on the valence.

  “A” in the composition formula is composed of an element having a valence of +4. In this embodiment, “A” is Ti and Sn.

  “X” in the above composition formula indicates a ratio (content of A) occupied by an element belonging to “A” among the metal elements in the composition formula of the composite oxide. In the present embodiment, the upper and lower limits of “x” are determined by the relationship with “y” and “z” described later.

  In “A”, assuming that the proportion occupied by Ti (Ti content) is x1, and the proportion occupied by Sn (Sn content) is x2, x = x1 + x2. Here, x1> 0 and x2> 0, x1 is preferably 0.005 or more, and x2 is preferably 0.005 or more. In this embodiment, the ratio of the Ti content (x1) to the Sn content (x2) is defined as α. That is, α = x1 / x2.

  “B” in the above composition formula is composed of an element having a valence of +3 that is 1 less than the valence (+4) of “A”. That is, the element belonging to “B” is an acceptor. Specifically, “B” is one or more selected from the group consisting of Al, Ga, In, Bi, and rare earth elements, and preferably includes at least In.

  The rare earth element is at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. . Therefore, “B” consists of Al, Ga, In, Bi, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. One or more selected from the group.

  “Y” in the above composition formula indicates a ratio (acceptor amount) of “B” replacing “A” in the composite oxide. In the present embodiment, y> 0 and preferably 0.0025 or more. The upper limit of “y” is determined by the relationship between “x” described above and “z” described later.

  “C” in the above composition formula is composed of an element having a valence of +5 which is 1 greater than the valence (+4) of “A”. That is, the element belonging to “C” is a donor. Specifically, “C” is one or more selected from the group consisting of Nb, Sb, Ta and W, and preferably contains at least Nb.

  “Z” in the above composition formula indicates the ratio (donor amount) of “C” replacing “A” in the composite oxide. In the present embodiment, z> 0 and preferably 0.0025 or more. The upper limit of “z” is determined by the relationship between “x” and “y” described above.

In this embodiment, in the oxide (AO ₂ ) of “A” having a rutile crystal structure, “B” serving as an acceptor and “C” serving as a donor are contained (a part of “A” is replaced). ), Complex oxide. Therefore, in the composition formula A _x B _y C _z O _{2 + δ} of the composite oxide, x + y + z = 1.0000.

The ratio of the Ti amount to the Sn amount (α), the replacement amount of “B” with respect to “A” (acceptor amount), and the replacement amount of “C” with respect to “A” (donor amount) satisfy the predetermined relationship. By controlling, it exhibits a very high dielectric constant (for example, 10,000 or more), and also has a high specific resistance (for example, 1.0 × 10 ¹⁰ Ωcm or more at 5 V / μm) even under a high electric field strength when a DC voltage is applied. Can be obtained.

  Specifically, the relationship between the Ti amount and the Sn amount satisfies the relationship of 0.10 <α ≦ 9.00, and the total of the replacement amounts of “B” and “C” (“A” is replaced) The total element substitution amount) satisfies the relationship of 0.0050 ≦ y + z ≦ 0.2000, and the ratio of the acceptor amount to the donor amount satisfies the relationship of 0.8000 ≦ y / z ≦ 1.2500. To do.

  In this embodiment, by setting the ratio of the Ti amount to the Sn amount and the ratio of the acceptor amount and the donor amount within the above ranges, a high specific resistance can be obtained even under a high electric field strength when a DC voltage is applied. Can do. On the other hand, when the ratio of the Ti amount to the Sn amount and the ratio between the acceptor amount and the donor amount do not satisfy the above relationship, when a high DC voltage is applied, the specific resistance tends to decrease rapidly. .

  Further, by setting the total substitution amount (total substitution amount) of “B” and “C” and the ratio between the acceptor amount and the donor amount within the above ranges, a very high dielectric constant can be obtained. On the other hand, if the total substitution amount is too large or too small, a high relative permittivity tends to be not obtained. Further, when the ratio between the acceptor amount and the donor amount is too small, a high relative dielectric constant tends not to be obtained.

  Therefore, in order to achieve both a very high dielectric constant and a high specific resistance under a high electric field strength when a DC voltage is applied, the ratio between the Ti amount and the Sn amount in “A” and the substitution of “B” and “C” The total amount and the ratio between the acceptor amount and the donor amount must all satisfy the above relationship.

For example, the following explanation is possible as a factor for obtaining a very high dielectric constant. That is, a part of “A” of AO ₂ ((Ti, Sn) O ₂ ) having a rutile-type crystal structure is selected from at least a pentavalent element “C” (Nb, Sb, Ta, W) as a donor By substituting with (one), negatively charged electrons are generated. However, when only the donor is introduced, usually, the hopping conduction of electrons is promoted, so that the specific resistance is lowered.

Therefore, further, by substituting a part of “A” of AO ₂ with an acceptor + trivalent element “B” (at least one selected from Al, Ga, In, Bi, and rare earth elements), Charged oxygen defects are generated, and the electrons generated by the generated oxygen defects are pinned. As a result, the movement of electrons is suppressed, so that a decrease in specific resistance can be suppressed. At this time, since the generated electrons move between the lattices of Ti—Ti or Sn—Sn within the range of the pinning effect due to oxygen defects, defect dipoles using oxygen defects are formed, and the presence of defect dipoles It is possible to obtain a huge relative dielectric constant.

  Moreover, as a factor which can obtain a high specific resistance under the high electric field strength at the time of DC voltage application, it can estimate as follows, for example. Oxygen vacancies generated by introduction of the acceptor are easily moved when a high DC voltage is applied, and the influence of the pinning effect is reduced for the pinned electrons, and the hopping conduction of the electrons easily occurs. For this reason, specific resistance falls rapidly under a high DC voltage.

  In this embodiment, in order to suppress this rapid decrease in specific resistance, the distance required for electron hopping conduction is increased to suppress electron hopping conduction, and “A” is composed of a plurality of elements. In addition, an interaction that suppresses a decrease in specific resistance is caused by setting the acceptor amount and the donor amount in a predetermined relationship.

That is, “A” of AO ₂ is composed of Ti and Sn, and the ratio of the Ti amount to the Sn amount (“α”) is controlled, and the ratio of the acceptor amount to the donor amount is controlled to control the amount of electrons. It is possible to increase the distance required for hopping conduction and to cause an interaction between elements belonging to “A”, “B” and “C”. This interaction makes it possible to suppress the movement of oxygen vacancies and enhance the effect of pinning electrons, and it is considered that the decrease in specific resistance can be suppressed even under a high electric field strength when a DC voltage is applied.

Therefore, among the oxides having a rutile crystal structure, SnO _{2 in} which the lengths of both the a-axis and the c-axis in the structure are relatively long is used, and the elements belonging to “A”, “B”, and “C” By adopting a combination having a strong interaction between them, a high specific resistance can be obtained under a high electric field strength when a DC voltage is applied. In other words, the above-described effect cannot be obtained at all by introducing an acceptor and a donor only into TiO ₂ or introducing an acceptor and a donor only into SnO ₂ .

  In the present embodiment, it is preferable that α satisfies the relationship of 0.33 <α ≦ 3.00. As described above, α indicates the ratio between the Ti amount (x1) and the Sn amount (x2). Therefore, the range of α described above is such that the Ti amount is more than 0.33 times the Sn amount and 3.00 times. The following are shown. In addition, since x1 + x2 = x, the range of α described above is the range where Ti occupies 24.81% to 75.00% in “A”, or Sn is 25.00% to 75.19%. It can be said that it is the range that occupies.

When Ti is 24.81% or less (when Sn is 75.19% or more), Ti, “B” and “C” replace Sn in SnO ₂ having a rutile crystal structure, and SnO ₂ Tends to be obtained. On the other hand, when Ti is more than 75.00% (when Sn is less than 25.00%), Ti in TiO ₂ having a rutile crystal structure is substituted with Sn, “B” and “C”, A composite oxide based on TiO ₂ tends to be obtained.

On the other hand, when α satisfies the relationship of 0.33 <α ≦ 3.00, it exceeds the limit (solid solution limit) at which Sn can be substituted for Sn in SnO ₂ . Complex oxide not containing (Ti _x B _y C _z O _{2 + δ} ) and complex oxide containing both Ti and Sn as “A” ((Ti, Sn) _x B _y C _z O _{2 + δ} ) Seems to coexist.

In addition, when exceeding the limit (solid solution limit) where Sn can be substituted for Ti in TiO ₂ , “A” is a composite oxide not containing Ti (Sn _x B _y C _z O _{2 + δ} ), and “A composite oxide that contains both Ti and Sn as "the _{((Ti, Sn) x B} y C z O 2 + δ), appear to coexist.

  In such a phase coexistence region, it is considered that two-phase interaction occurs. As a result, the DC bias voltage characteristics are dramatically improved while maintaining the above-described effects. That is, by setting the α range to the above preferable range, in addition to obtaining a very large dielectric constant and a high specific resistance under a high electric field strength when a DC voltage is applied, a DC voltage is applied. It is possible to reduce the decrease rate of the relative dielectric constant when the DC voltage is applied with respect to the relative dielectric constant when there is not.

  Moreover, it is preferable that y and z satisfy the relationship of 0.9000 ≦ y / z ≦ 1.1000. That is, by setting the ratio of the substitution amount of “B” (acceptor amount) and the substitution amount of “C” (donor amount) within the above range, a higher specific resistance can be obtained.

  In addition, the dielectric composition according to the present embodiment may contain a trace amount of impurities, subcomponents, and the like within a range where the effects of the present invention are exhibited. Examples of such components include Mn, Ca, Ba, Zn, and the like. Therefore, the content of the main component is not particularly limited, but is, for example, 70 mol% or more and 100 mol% or less with respect to the entire dielectric composition containing the main component.

(1.3 Internal electrode layer)
In the present embodiment, the internal electrode layers 3 are laminated so that each end face is alternately exposed on the surface of the two opposite ends of the element body 10.

  The conductive material contained in the internal electrode layer 3 is not particularly limited, but Ni, Ni-based alloy, Cu or Cu-based alloy is preferable. In addition, in Ni, Ni-type alloy, Cu, or Cu-type alloy, various trace components, such as P, may be contained about 0.1 mass% or less. The internal electrode layer 3 may be formed using a commercially available electrode paste. What is necessary is just to determine the thickness of the internal electrode layer 3 suitably according to a use etc.

(1.4 External electrode)
In the present embodiment, the pair of external electrodes 4 are formed at both ends of the element body 10 and connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit. The conductive material contained in the external electrode 4 is not particularly limited. In the present embodiment, various conductive materials such as inexpensive Ni, Cu, high heat-resistant Au, Ag, Pd, and alloys thereof can be used. The thickness of the external electrode 4 may be determined as appropriate according to the application and the like, but is usually preferably about 10 to 50 μm.

(2. Manufacturing method of multilayer ceramic capacitor)
Next, an example of a method for manufacturing the multilayer ceramic capacitor 1 shown in FIG. 1 will be described below.

  In the multilayer ceramic capacitor 1 according to the present embodiment, a green chip is produced by a normal printing method or a sheet method using a paste as in the case of a conventional multilayer ceramic capacitor, and this is fired to obtain an element body. It is manufactured by printing or transferring an external electrode on the element body and baking it. Hereinafter, the manufacturing method will be specifically described.

First, a starting material for the dielectric composition is prepared. As a starting material, a metal oxide, a mixture thereof, or a composite oxide included in the composite oxide constituting the dielectric composition can be used. In addition, various compounds that are converted into the above-described oxides or composite oxides by firing, such as carbonates, oxalates, nitrates, hydroxides, organometallic compounds, and the like, can be appropriately selected and mixed for use. For example, when “B” is In and “C” is Nb, TiO ₂ powder, SnO ₂ powder, In ₂ O ₃ powder, and Nb ₂ O ₅ powder may be prepared. In addition, it is preferable that the average particle diameter of each powder is 1.0 micrometer or less.

  The prepared starting materials are weighed at a predetermined ratio, and then wet mixed using a ball mill or the like for a predetermined time. After drying the mixed powder, heat treatment at 1000 ° C. or lower is performed in the air to obtain a calcined powder of a composite oxide.

  Subsequently, the calcined powder obtained above is made into a paint to prepare a dielectric layer paste. The dielectric layer paste may be an organic paint obtained by kneading a dielectric mixed powder and an organic vehicle, or may be a water-based paint.

  An organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. The organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone and the like according to a method to be used such as a printing method or a sheet method.

  In addition, when the dielectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder, a dispersant or the like is dissolved in water and a dielectric material may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, etc. may be used.

  The internal electrode layer paste is a mixture of the above-described various conductive metals, conductive materials made of alloys thereof, or various oxides, organometallic compounds, resinates, and the like that become the conductive materials described above after firing, and the above-described organic vehicle. To prepare.

  The external electrode paste may be prepared in the same manner as the internal electrode layer paste described above.

  There is no restriction | limiting in particular in content of the organic vehicle in each above-mentioned paste, For example, what is necessary is just about 1 mass%-about 5 mass% for a binder, and about 10 mass%-about 50 mass% for a solvent. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. The total content of these is preferably 10% by mass or less.

  When the printing method is used, the dielectric layer paste and the internal electrode layer paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip.

  When the sheet method is used, a dielectric layer paste is used to form a green sheet, the internal electrode layer paste is printed thereon, and these are stacked to form a green chip.

Before firing, the green chip is subjected to binder removal processing. As binder removal conditions, the rate of temperature rise 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 is air or a reducing atmosphere. Further, in the above-described binder removal process, for example, a wetter or the like may be used to wet the N ₂ gas, mixed gas, or the like. In this case, the water temperature is preferably about 5 ° C to 75 ° C.

  Moreover, the holding temperature at the time of baking becomes like this. Preferably it is 1250 degreeC-1450 degreeC, More preferably, it is 1300 degreeC-1400 degreeC. If the holding temperature is less than the above range, densification of the sintered body becomes insufficient, and if it exceeds the above range, the electrode is likely to be disconnected due to abnormal sintering of the internal electrode layer, and the material constituting the internal electrode layer The rate of change of capacitance with respect to temperature is likely to increase due to the diffusion of. In addition, if the above range is exceeded, the crystal grains may be coarsened and the insulating properties of the sintered body may be reduced.

  The rate of temperature rise is preferably 200 ° C./hour to 1000 ° C./hour, more preferably 200 ° C./hour to 500 ° C./hour. In order to control the particle size distribution of the sintered crystal particles within the range of 0.5 μm to 5.0 μm, the temperature holding time is preferably 1.0 hour to 24.0 hours, more preferably 2.0. The cooling rate is preferably 100 ° C./hour to 500 ° C./hour, more preferably 200 ° C./hour to 300 ° C./hour.

As the firing atmosphere, a mixed gas of wet _{N 2} and _{H 2,} it is preferable oxygen partial pressure is ¹⁰ -2 ^~10 -9 Pa. More preferably, the oxygen partial pressure is 10 ⁻² to 10 ⁻⁵ Pa.

  After firing, the obtained element body is annealed as necessary. The annealing conditions may be known conditions. For example, it is preferable that the oxygen partial pressure during the annealing process is higher than the oxygen partial pressure during firing, and the holding temperature is 1000 ° C. or lower.

  Moreover, said binder removal process, baking, and annealing treatment may be performed independently, and may be performed continuously.

  The composite oxide contained in the dielectric layer of the sintered body (element body) obtained as described above is represented by the above-described composition formula and has a rutile crystal structure. The sintered body is subjected to end face polishing by, for example, barrel polishing or sand blasting, and an external electrode paste is applied and fired to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

(3. Effects in the present embodiment)
In this embodiment, as a composite oxide constituting the dielectric composition, an oxide of an element having a valence of +4 (“A”) is used as a base, and a part of “A” is used as an acceptor element (“B”). ") And a donor element (" C ").

  Then, by controlling the total substitution amount (y + z) of the substitution element and the ratio of the acceptor amount (y) and the donor amount (z) to a predetermined range, it is caused by a defect dipole mechanism using oxygen defects. It is possible to develop a very large relative dielectric constant.

  Furthermore, as “A”, Ti and Sn are selected, and the ratio (α) between the Ti amount and the Sn amount and the ratio between the acceptor amount (y) and the donor amount (z) are controlled within a predetermined range. ing. This increases the distance required for hopping conduction of electrons, and interaction occurs between Ti and Sn (A), the acceptor (B), and the donor (C). As a result, it is possible to suppress a decrease in specific resistance even under a high electric field strength when a DC voltage is applied. In other words, the voltage dependency of the specific resistance can be reduced.

That is, in AO ₂ , a specific element is selected as A, a part of “A” is replaced by an acceptor (“B”) and a donor (“C”), and “A”, “B” and “C” By making the relationship of the content of the elements belonging to the above-mentioned range, a high specific resistance (for example, an electric field of 5 V / μm) under a high electric field strength while exhibiting a very high dielectric constant (for example, 10,000 or more) Under strength, 1.00 × 10 ¹⁰ Ωcm or more) can be obtained.

  Since the electric field strength is proportional to the applied voltage, the fact that the dielectric composition according to the present embodiment has a high specific resistance under a high electric field strength means that an electron including a dielectric layer containing the dielectric composition is provided. It leads to raising the rated voltage of parts. Therefore, such an electronic component can be used even when a high voltage exceeding the rated voltage of the conventional electronic component is applied, and more electric charges can be accumulated.

Further, by limiting the ratio (α) between the Ti amount and the Sn amount to a preferable range, “A” is an AO ₂ -based composite oxide containing both elements (Ti and Sn), and “A” By making the AO ₂ -based composite oxide containing one of Ti, Sn and the phase coexist, the DC bias voltage characteristics can be dramatically improved.

  The DC bias voltage characteristic is a characteristic indicating how much the relative dielectric constant when a predetermined DC voltage is applied changes (decreases) with respect to the relative dielectric constant when no DC voltage is applied. is there. When the electronic device on which the electronic component is mounted is operated, a DC voltage is applied to the electronic component as a bias voltage. When the relative permittivity when no DC voltage is applied is used as a reference, the relative permittivity when a DC voltage is applied usually decreases. In particular, the relative permittivity tends to decrease rapidly as the voltage increases. Therefore, even if the relative permittivity when the DC voltage is not applied is very large, if the relative permittivity when the DC voltage is applied decreases (if the DC bias voltage characteristics are poor), the electronic device is activated. In this case, the effective electrostatic capacity of the electronic component becomes small.

  Therefore, the improvement of the DC bias voltage characteristics of the dielectric composition according to the present embodiment leads to an increase in the effective capacitance of an electronic component including a dielectric layer containing the dielectric composition. Such an electronic component can store more charge than a conventional electronic component because the decrease in relative permittivity is small even when a DC bias voltage is applied.

  Further, by limiting the ratio of the acceptor amount (y) and the donor amount (z), the high specific resistance under a high electric field strength can be further increased.

(4. Modifications)
In the above-described embodiment, the case where the electronic component is a multilayer ceramic capacitor has been described. However, the electronic component may be another electronic component, for example, a thin film capacitor. In this case, the dielectric layer of the thin film capacitor may be composed of the above-described dielectric composition. The dielectric layer of the thin film capacitor may be formed by depositing the elements constituting the dielectric composition described above on the substrate using, for example, a thin film forming method. As the thin film forming method, a known vapor deposition method such as a sputtering method or a chemical vapor deposition method is preferable.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment at all, You may modify | change in various aspects within the scope of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

First, as a starting material of the composite oxide (A _x B _y C _z O _{2 + δ} ) which is the main component of the dielectric composition, titanium dioxide (TiO ₂ ), tin dioxide (SnO ₂ ), and an oxide of “B” ( B ₂ O ₃ ) and “C” oxide (C ₂ O ₅ ) powders were prepared. The average particle size of each powder was 1.0 μm or less. The above starting materials were weighed so that the fired dielectric composition (sintered body) had the compositions shown in Tables 1 and 2.

  Next, each starting raw material powder weighed was wet mixed by a ball mill for 16 hours using ethanol as a dispersion medium, and the mixture was dried to obtain a mixed raw material powder. Thereafter, the obtained mixed raw material powder was heat-treated in the atmosphere under the conditions of a holding temperature of 950 ° C. and a holding time of 24 hours to obtain a calcined powder of a composite oxide.

  To 1000 g of the calcined powder obtained above, 700 g of a solvent obtained by mixing a toluene + ethanol solution, a plasticizer and a dispersant at 90: 6: 4 was added, and 2 using a basket mill which is a well-known dispersion method. Dispersion with time was performed to prepare a dielectric layer paste.

  Ni powder having an average particle size of 0.2 μm was prepared as a raw material for the internal electrode layer, Ni powder 100% by mass, and organic vehicle (ethyl cellulose resin 8% by mass dissolved in butyl carbitol 92% by mass) 30% by mass. % And 8% by mass of butyl carbitol were kneaded and made into a paste with three rolls to obtain an internal electrode layer paste. The viscosity of these pastes was adjusted to about 200 cps.

  Using the produced dielectric layer paste, a green sheet was formed on a PET film so that the thickness after drying was 7 μm. Next, the internal electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, and then the sheet was peeled from the PET film to produce a green sheet having the internal electrode layer. Next, a plurality of green sheets having internal electrode layers were laminated and pressure-bonded to form a green laminate, and the green laminate was cut into a predetermined size to obtain a green chip.

Next, the obtained green chip was subjected to binder removal processing, firing and annealing treatment to obtain a multilayer ceramic sintered body. The conditions for the binder removal treatment, firing and annealing treatment are as follows. Moreover, a wetter was used for humidifying each atmospheric gas.
(Binder removal)
Temperature increase rate: 100 ° C / hour Holding temperature: 400 ° C
Temperature holding time: 8.0 hours Atmospheric gas: Mixed gas of N ₂ and H ₂ humidified (firing)
Temperature rising rate: 300 ° C./hour holding temperature: 1300 ° C. to 1450 ° C.
Temperature holding time: 10 hours Cooling rate: 200 ° C./hour Atmospheric gas: Mixed gas of humidified N ₂ and H ₂ Oxygen partial pressure: 10 ⁻² to 10 ⁻⁵ Pa
(Annealing treatment)
Holding temperature: 1000 ° C
Temperature holding time: 2.0 hours temperature rise, temperature drop rate: 200 ° C./hour Atmosphere gas: humidified N ₂ gas

  The obtained sintered bodies (element main bodies) were analyzed in terms of the composition of the dielectric composition contained in each sintered body using ICP emission spectroscopy, and are listed in Tables 1 and 2. Consistent with composition.

  After polishing the end face of the obtained sintered body by sand blasting, an In—Ga eutectic alloy was applied as an external electrode, and a multilayer ceramic capacitor sample having the same shape as the multilayer ceramic capacitor shown in FIG. And Comparative Examples 1 to 33) were obtained. The size of each obtained multilayer ceramic capacitor sample is 3.2 mm × 1.6 mm × 1.2 mm, the thickness of the dielectric layer is 5.0 μm, the thickness of the internal electrode layer is 2.0 μm, The number of the dielectric layers sandwiched was 50 layers.

  For the obtained multilayer ceramic capacitor samples of Examples 1 to 44 and Comparative Examples 1 to 33, the relative dielectric constant at room temperature, tan δ, specific resistance when applying a DC voltage of 25 V (electric field strength of 5 V / μm), and room temperature The relative dielectric constant change rate (DC bias voltage characteristics) when a DC voltage of 25 V (electric field strength of 5 V / μm) was applied to the relative dielectric constant was measured and evaluated as follows.

[Relative permittivity and tan δ]
A multilayer ceramic capacitor sample is input at room temperature (20 ° C) with a digital LCR meter (YHP 4284A) with a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms, and the capacitance and tan δ are measured. did. The relative dielectric constant (no unit) was calculated based on the thickness of the dielectric layer, the effective electrode area, and the capacitance obtained by the measurement. The relative dielectric constant is preferably high, and it is judged that 10,000 or more is good, and tan δ is preferably low, and 30% or less is judged good. The results are shown in Tables 1 to 3.

[Specific resistance when DC voltage is applied]
A measurement voltage of 25 V (electric field strength of 5 V / μm) was applied to the multilayer ceramic capacitor sample at room temperature (20 ° C.) with a digital resistance meter (R8340 manufactured by ADVANTEST), and the insulation resistance was measured under the conditions of a measurement time of 60 seconds. It was measured.

The specific resistance value was calculated from the obtained insulation resistance, the electrode area of the multilayer ceramic capacitor sample, and the dielectric thickness. A higher specific resistance is preferable, and a sample having a measurement voltage of 25 V (electric field strength of 5 V / μm) of 1.00 × 10 ¹⁰ Ωcm or higher was judged to be good. A sample having a specific resistance of 1.00 × 10 ¹² Ωcm or more is more preferable. The results are shown in Tables 1 to 3.

In Tables 1 to 3, specific resistance values are logarithmically expressed. When “a” is represented in the specific resistance column of Tables 1 to 3, the specific resistance value is 10 ^a . When 1.00 × 10 ¹² is logarithmically displayed, it becomes 12.0, and when 3.16 × 10 ¹⁰ is logarithmically displayed, it becomes 10.5, and when 1.00 × 10 ⁸ is logarithmically displayed, it becomes 8.0.

[DC bias voltage characteristics]
With a measurement voltage of 25 V (electric field strength of 5 V / μm) applied to a multilayer ceramic capacitor sample at room temperature (20 ° C.), a digital LCR meter (YHP 4284A) has a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms. The signal was input and the capacitance was measured. And the relative dielectric constant (unitless) at the time of DC voltage application was computed based on the thickness of a dielectric material layer, an effective electrode area, and the electrostatic capacitance obtained by measurement. Subsequently, the change rate (DC bias voltage characteristics) of the obtained dielectric constant when a DC voltage was applied was calculated based on the above-described dielectric constant at room temperature. A sample having a DC bias voltage characteristic of −10% or more was judged to be good. A sample having a DC bias voltage characteristic of −5% or more is more preferable. The results are shown in Tables 1 to 3.

  In addition, in the column of the DC bias voltage characteristics in Tables 1 to 3, when “−” is represented, the dielectric characteristics that are the characteristics of the insulating material with the decrease in the specific resistance when the DC voltage is applied to the sample, that is, Indicates that the capacitance could not be measured.

From Tables 1 to 3, in the composite oxide having a rutile crystal structure and containing the above-described metal element, the ratio of Ti amount to Sn amount (“α”), acceptor amount (y), donor amount ( A sample in which the relationship of z) is within the above-described range exhibits a very high relative dielectric constant (10000 or more), and has a high specific resistance (1.00 × 10 ¹⁰ Ωcm) under a high electric field strength (5 V / μm). The above was confirmed.

  Furthermore, by further limiting the range of “α”, the DC bias voltage characteristics can be dramatically improved while achieving both a very high dielectric constant and a high resistivity under a high electric field strength. Was confirmed.

Further, it was confirmed that a higher specific resistance (1.00 × 10 ¹² Ωcm or more) was exhibited under a high electric field strength (5 V / μm) by further limiting the ratio between the acceptor amount and the donor amount.

  On the other hand, when the above-mentioned metal element is not contained in the oxide having a rutile crystal structure, or the ratio of Ti amount to Sn amount (“α”), acceptor amount (y), donor amount (z) When the relationship is outside the above-mentioned range, it was confirmed that one or both of the high specific permittivity and the high specific resistance under a high electric field strength tend to deteriorate.

The dielectric composition according to the present invention has a high relative dielectric constant (for example, 10,000 or more) and a high specific resistance under a high electric field strength (for example, 1.00 × 10 ¹⁰ Ωcm or more at 5 V / μm). Therefore, it can be suitably used as a dielectric layer of an electronic component such as a small-sized and large-capacity multilayer ceramic capacitor or a low-profile and large-capacity thin film capacitor.

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Element main body 2 ... Dielectric layer 3 ... Internal electrode layer 4 ... External electrode

Claims (4)

Composition formula represented by _{A x B y C z O 2} + δ, comprise a composite oxide having a rutile-type crystal structure as a main component,
A is Ti and Sn,
B is one or more elements selected from the group consisting of Al, Ga, In, Bi and rare earth elements,
The C is one or more elements selected from the group consisting of Nb, Sb, Ta and W;
When the ratio of Ti amount to Sn amount in A is α, 0.10 <α ≦ 9.00,
X, y and z are
x> 0, y> 0, z> 0,
x + y + z = 1.0000,
0.0050 ≦ y + z ≦ 0.2000,
0.8000 ≦ y / z ≦ 1.2500
A dielectric composition characterized by satisfying the relationship:   The dielectric composition according to claim 1, wherein the α satisfies a relationship of 0.33 <α ≦ 3.00.   The dielectric composition according to claim 1, wherein the y and the z satisfy a relationship of 0.9000 ≦ y / z ≦ 1.1000.   An electronic component comprising a dielectric layer comprising the dielectric composition according to claim 1.

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