JP2000281435A - Dielectric composition and ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric composition that shows excellent reduction resistance on firing and has high dielectric constant, low distortion factor, and excellent capacity-temperature properties. SOLUTION: This dielectric composition includes at least BaTiO3, SrZrO3 and CaZrO3. As for these three composition molar ratios, the composition molar ratio of BaTiO3 (X) is 0.5<=X<=0.675, the composition molar ratio of SrZrO3 (Y) is 0.1<=Y<=0.4 and the composition molar ratio of CaZrO3 (Z) is 0.07<=Z<=0.25 where X+Y+Z=1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric composition and a ceramic capacitor using the same, and more particularly to a dielectric composition having excellent reduction resistance during firing, a high dielectric constant and a low distortion rate, and a capacitance temperature. A dielectric composition with excellent properties,
Also, the present invention relates to a ceramic capacitor having high insulation resistance, high capacitance, low distortion characteristics, flat capacitance-temperature characteristics, and capable of using a base metal for an internal electrode.

[0002]

2. Description of the Related Art As a dielectric composition used for a ceramic capacitor or the like, barium titanate (BaTiO.sub.3) is used.
₃ ) A substance having a high dielectric constant mainly composed of ₃ ) is known. However, since it is a ferroelectric substance, the nonlinear characteristic of voltage is strong, and the distortion rate is as large as -50 dB to -70 dB. For this reason, a capacitor requiring a low distortion rate such as a capacitor for a coupling circuit, a capacitor for an acoustic circuit, or a capacitor for an image processing circuit cannot use a BaTiO ₃ -based capacitor, and exclusively uses a film capacitor or an electrolytic capacitor. However, it is difficult to miniaturize such film capacitors and electrolytic capacitors, and there is a problem in surface mountability.

On the other hand, among ceramic capacitors,
Calcium ruconate (CaZrO)₃ ), Zirconate strike
Rontium (SrZrO₃), Calcium titanate
(CaTiO₃), Strontium titanate (SrT
iO₃), Strontium calcium zirconate (C
aSrZrO₃), Neodymium titanate (NdTiO)
₃) Is composed of a paraelectric
Because of its low efficiency, it can be used for coupling circuits and acoustic circuits.
However, the relative dielectric constant ε is 30
It is difficult to obtain a high-capacity capacitor as low as ~ 200
It is.

Therefore, both high dielectric constant and low distortion are shown.
SrTiO as a dielectric composition ₃, Bis titanate
Trout (Bi₂TiO₃), CaTiO₃,Titanium
Lead acid (PbTiO₃) As the main component has been proposed
(See, for example, JP-A-3-97,669).
See).

[0005]

By the way, platinum (Pt) and gold (Au) are applied to the internal electrodes of the ceramic capacitor.
Alternatively, a noble metal such as silver (Ag) is used, but it is preferable to use a base metal such as nickel (Ni) from the viewpoint of cost.

[0006] Since the above-mentioned dielectric composition contains bismuth (Bi) and lead (Pb) having low vapor pressures, they are evaporated when fired in a reducing atmosphere. Therefore, firing in an oxidizing atmosphere is a prerequisite, but firing in an oxidizing atmosphere oxidizes Ni when a low-cost base metal, for example, Ni is used for the internal electrodes, and eventually, Pt and Au are applied to the internal electrodes. Or noble metal such as Ag was used.
SrTiO ₃ and CaTiO ₃ have a dielectric constant of 250.
It is as low as below.

[0007] The present invention has been made in view of such problems of the prior art, and has excellent reduction resistance during firing.
A dielectric composition that exhibits high dielectric constant and low distortion rate and has excellent capacitance-temperature characteristics, and that a base metal is used for the internal electrodes with high insulation resistance, high capacitance and low distortion characteristics, flat capacitance-temperature characteristics, It is an object of the present invention to provide a ceramic capacitor which can be used.

[0008]

Means for Solving the Problems (1) The dielectric constant is large, the distortion rate is small, and the capacitance change rate with respect to temperature is also small (hereinafter, sometimes referred to as "the capacitance-temperature characteristics are flat"). The present inventors have conducted intensive studies in order to obtain a well-balanced dielectric composition, and have obtained the following findings.

First, the strain rate depends on the electric field dependence of the dielectric constant and the non-linear characteristic (ie, ferroelectricity). As a measure for suppressing this, the linearity of the dielectric constant can be improved or the crystallinity can be improved. It is considered effective to reduce ferroelectricity by reducing anisotropy or to use a paraelectric phase. However, reducing the ferroelectricity lowers the dielectric constant, so that a balance between these is important. In addition, since a paraelectric has a negative capacitance-temperature characteristic and a ferroelectric has a positive capacitance-temperature characteristic, the balance between the ferroelectric and the paraelectric is important for the capacitance-temperature characteristic.

The balance between the dielectric constant, the strain rate, and the capacitance-temperature characteristic is determined by using barium titanate (BaTiO ₃ ),
It becomes suitable by controlling the composition molar ratio of strontium zirconate (SrZrO ₃ ) and calcium zirconate (CaZrO ₃ ). In the present invention, the paraelectric phase and the ferroelectric phase are balanced by adding BaTiO ₃ which is a ferroelectric substance to CaZrO ₃ and SrZrO ₃ which are paraelectric substances, so that the dielectric constant is large and the distortion rate is small. In addition, a dielectric composition having a flat capacitance-temperature characteristic can be obtained.

That is, BaTiO₃Composition molar ratio increased
Then, the dielectric constant increases, but the capacitance changes with temperature.
The conversion rate also tends to increase. On the other hand, SrZr
O₃ As the composition molar ratio increases, the dielectric constant decreases.
In addition, CaZrO₃When the composition molar ratio of
The rate tends to increase. In addition, CaZrO₃And Sr
ZrO₃And SrZrO₃Composition molar ratio of
Increases, the strain rate decreases, but
The capacity change rate tends to increase. In contrast, C
aZrO₃When the composition molar ratio of
The rate of change in capacitance tends to decrease but the rate of distortion increases
There is.

(2) Based on these findings, the invention according to the first aspect provides at least BaTiO ₃ , SrZrO
₃ and a “dielectric composition” containing CaZrO ₃ , wherein at least these three molar ratios are:
When the composition molar ratio (X) of BaTiO ₃ is 0.5 ≦ X ≦
0.675 (0.5 or more and 0.675 or less), SrZrO
_{3 has} a composition molar ratio (Y) of 0.1 <Y ≦ 0.4 (0.
1 and 0.4 or less), and the composition molar ratio (Z) of CaZrO ₃ is 0.075 ≦ Z <0.25 (0.075 ≦
(Smaller than 0.25) and X + Y + Z = 1 (the hatched portion in FIG. 1; however, in FIG. 1, the line on Y = 0.1 and the boundary on Z = 0.25 are Not included).

SrZrO ₃ and CaZ as paraelectrics
By adding BaTiO ₃ , which is a ferroelectric substance, to rO ₃ , a dielectric composition that achieves a balance between the paraelectric phase and the ferroelectric phase, has a large dielectric constant, a small distortion rate, and has a flat capacitance-temperature characteristic. You can get things. In the present invention, in order to say that the dielectric constant is large, for example, the relative dielectric constant ε is preferably 350 or more, more preferably 400 or more. In order to say that the distortion rate is small, for example, the third harmonic distortion rate (THD) is
Preferably -70 dB or less, more preferably -75 dB
It is as follows. Furthermore, in order to say that the capacitance-temperature characteristics are flat (the capacitance change rate with respect to temperature is small), for example, the capacitance change rate with respect to temperature is at least -3.
In the temperature range of 0 ° C to + 85 ° C, the reference temperature is 2
When the temperature is set to 5 ° C., it is preferably within ± 15%, more preferably within ± 10%.

That is, the composition molar ratio of BaTiO ₃ (X)
Is large, the dielectric constant increases, but the rate of change in capacitance with respect to temperature tends to increase (temperature characteristics deteriorate). If it is low, the dielectric constant tends to decrease. Also, S
When the composition molar ratio (Y) of rZrO ₃ is large, the dielectric constant tends to decrease. Further, when the composition molar ratio (Z) of CaZrO ₃ is large, the strain rate tends to increase, and when the composition molar ratio (Z) is small, the capacity change rate with respect to temperature tends to increase. Therefore, in order to balance the dielectric constant, the distortion factor, and the capacitance temperature characteristic, 0.525 ≦ X ≦ 0.675
(X is 0.525 or more and 0.675 or less), 0.125 ≦
Y ≦ 0.375 (Y is 0.125 or more and 0.375 or less) and 0.075 ≦ Z ≦ 0.225 (Z is 0.07
5 to 0.225) and X + Y + Z = 1, preferably 0.525 ≦ X ≦ 0.65 (X is 0.525 to 0.65) and 0.15 ≦ Y ≦ 0. 3
5 (Y is 0.15 or more and 0.35 or less), and 0.1 ≦ Z
≦ 0.2 (Z is 0.1 or more and 0.2 or less), and X
More preferably, + Y + Z = 1.

(3) The invention according to the second aspect is characterized in that at least BaTiO ₃ , SrZrO ₃ and CaZr
A dielectric composition containing O ₃ , wherein BaTiO ₃ in which calcium (Ca), strontium (Sr), and zirconium (Zr) are at least partially dissolved.
And SrZrO ₃ and C surrounding the particles
aZrO ₃ or a solid solution thereof ((SrCa) Z
rO ₃ ).

By forming a structure in which BaTiO ₃ , which is a ferroelectric, is surrounded by SrZrO ₃ and CaZrO ₃ , which are paraelectrics, or a solid solution thereof ((SrCa) ZrO ₃ ), the paraelectric phase and the ferroelectric It is possible to obtain a dielectric composition that balances phases, has a large dielectric constant, a small distortion rate, and has a flat capacitance-temperature characteristic.

That is, most of the applied voltage depends on a mixed structure (inter-particle level and intra-particle level) of a ferroelectric phase (having a domain structure) having a high strain rate and a paraelectric phase (having no domain structure) having a low strain rate. It is considered that the voltage applied to the ferroelectric phase having a high strain rate is reduced because the voltage applied to the paraelectric phase having a low relative dielectric constant (ε) is reduced, and thus the strain rate is reduced as a whole.

The Ca, Sr and Zr present in the BaTiO ₃ particles need only be dissolved in at least a part of the particles. For example, in the particles made of BaTiO ₃ , Ca, Sr and Zr are diffused at a low concentration, and a portion having a region showing a domain structure of almost pure BaTiO ₃ and a portion having a high concentration of Ca, Sr and Zr are provided. A portion which is diffused and does not have a domain structure-indicating region, and comprises Ca, Sr from a portion having the domain structure-indicating region to a portion not having the domain structure-indicating region. And Zr
Even if the structure has a concentration gradient in which the concentration distribution gradually increases (see FIG. 5A), a structure having a region having a domain structure and a structure having no region having a domain structure are adjacent to each other. (See FIG. 5B), but preferably (see FIG. 5A). Particles made of BaTiO _{3 having} a structure like
₃ and CaZrO ₃ , or a solid solution thereof ((Sr
According to the dielectric composition having particles structured to be surrounded by particles composed of Ca) ZrO ₃ ), the balance between the dielectric constant, the strain rate, and the capacitance-temperature characteristic can be further improved.

(4) In the invention according to the first and second aspects described above, the average particle diameter of the BaTiO ₃ is 1.0 μm.
m or less. By using BaTiO ₃ having an average particle diameter of 1.0 μm or less, the balance between the paraelectric phase and the ferroelectric phase is more remarkably achieved, the dielectric constant is large, the distortion is small, and the capacitance-temperature characteristic is flat. A certain dielectric composition can be easily obtained.

That is, if the average particle diameter of BaTiO ₃ is too large, the strain rate tends to increase. Therefore,
In order to further balance the dielectric constant, the strain rate, and the capacitance-temperature characteristic, the average particle diameter is more preferably 0.7 μm or less, and most preferably 0.5 μm or less. The lower limit of the average particle size is appropriately determined within a range in which the object of the present invention can be achieved, and is usually 0.1 μm.

(5) In the invention according to the first and second aspects described above, various additives may be contained. Such additives include Mg, Mn, Cr, Co, Z
At least one oxide selected from the group consisting of n and Al (eg, magnesium oxide (MgO)) and / or a compound that becomes an oxide of Mg upon firing, and a “reduction-resistant auxiliary agent” such as a carbonate. Preferably Mg
(For example, magnesium oxide (MgO)) and / or a compound which becomes an oxide of Mg by firing, more preferably MgO. This reduction-resistant auxiliary has an effect of accelerating sintering and an effect of improving insulation resistance (IR). However, if the addition amount is too large, the relative dielectric constant decreases,
On the other hand, if the amount is too small, the insulation resistance decreases, so that the amount of BaTiO ₃ , SrZrO ₃ and CaZ
For 100 mol% of the basic component containing rO ₃ ,
A range of 0.1 to 10 mol% is preferred.

Further, as another additive, silicon oxide (Si
O₂), Aluminum oxide (Al ₂O₃),
MO-SiO₂(However, "M" here is Ba, S
at least one selected from the group consisting of r, Ca and Mg
Shows more than species. ), Such as those previously calcined and synthesized.
Agent ", preferably SiO 2₂Or M
O-SiO₂It is. This sintering aid lowers the sintering temperature.
And has the effect of promoting sintering and insulation resistance.
It also has the effect of improving. Also, the capacity-temperature characteristics are not very
Has no effect. However, if the amount is too large,
Electricity decreases, and too low results in poor sinterability
Therefore, the addition amount is BaTiO₃, SrZrO
₃And CaZrO₃100 moles of basic components containing
% Is preferably in the range of 0.05 to 5 mol%.

(6) The above-described dielectric composition according to the present invention is preferably used as a material for the dielectric layer of a ceramic capacitor having an internal electrode and a dielectric layer.

In this case, the internal electrode is made of nickel (N
More preferably, it is composed of i) or a Ni alloy. Since the dielectric composition according to the present invention is excellent in reduction resistance, sintering in a reducing atmosphere is possible, and Ni or a Ni alloy can be used as an internal electrode, so that the cost can be reduced.

The structure and the like of the ceramic capacitor are not particularly limited, and include a single-plate capacitor as well as a multilayer capacitor.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a partially cutaway perspective view showing an embodiment of the multilayer ceramic capacitor of the present invention.

First, the structure of the multilayer ceramic capacitor will be described. As shown in FIG. 2, the multilayer ceramic capacitor 1 of the present embodiment has a pair of external electrodes 13 in which internal electrodes 11 and dielectric layers 12 are alternately stacked and connected to each internal electrode.

In the present embodiment, the internal electrode 11 is formed of Ni or a Ni alloy, and is not particularly limited.
As the alloy, 95% by weight or more of Ni and manganese (M
n), one or more alloys such as chromium (Cr), cobalt (Co), and aluminum (Al).
Ni or a Ni alloy may contain, as a trace component, 0.1% by weight or less of phosphorus (P) or the like.

Various conditions such as the thickness of the internal electrode 11 may be appropriately determined according to the purpose and application.
It is 5 μm, preferably 2-3 μm.

The material of the dielectric layer 12 is at least BaT
It is composed of a dielectric composition containing iO ₃ , SrZrO ₃ and CaZrO ₃ . The three composition molar ratios are as described above.

Further, 0.1 to 10 mol% of a reduction resistance auxiliary such as MgO is added to 100 mol% of the dielectric composition.
Preliminarily calcined and synthesized with SiO ₂ , Al ₂ O ₃ , and MO—SiO ₂ (where “M” represents at least one or more selected from the group consisting of Ba, Sr, Ca, and Mg). It is preferable to add a sintering aid such as 0.05 to 5 mol%.

The external electrode 13 is usually made of copper (C
u), a Cu alloy, Ni or a Ni alloy, or the like, but gold (Au), an alloy of silver (Ag) and palladium (Pd), or the like can also be used. The thickness of the external electrode 13 is arbitrary, and may be appropriately determined according to the purpose and application.
0 to 50 μm.

The shape and size of such a multilayer ceramic capacitor 1 may be appropriately determined according to the purpose and application. For example, in the case of a rectangular parallelepiped, usually 1.6 to 1.6
3.2mm × 0.8-1.6mm × 0.6-1.2mm
It is about.

Next, a method of manufacturing the multilayer ceramic capacitor 1 of the present embodiment will be described. First, a paste for a dielectric layer, a paste for an internal electrode, and a paste for an external electrode are manufactured.

The dielectric layer paste is manufactured by kneading a dielectric material and an organic vehicle according to the composition of the above-described dielectric composition, or as a water-based paint. Dielectric raw materials include various compounds that become the above-described composite oxides and oxides,
For example, they can be appropriately selected from carbonates, nitrates, hydroxides, organometallic compounds, and the like, and used by mixing. The content of each compound in the dielectric material may be determined so as to have the above-described composition of the dielectric layer after firing. The dielectric material is
Usually, it is used as a powder having an average particle diameter of about 0.1 to 3.0 μm.

The organic vehicle is obtained by dissolving a binder in an organic solvent, and the binder used for the organic vehicle is not particularly limited, and may be appropriately selected from various ordinary binders such as ethyl cellulose and polyvinyl butyral. In addition, the organic solvent used at this time is not particularly limited, and may be appropriately selected from organic solvents such as terpineol, butyl carbitol, acetone, and toluene depending on a method such as a printing method or a sheet method.

The water-based paint is obtained by dissolving a water-soluble binder, a dispersant, and the like in water. The water-based binder is not particularly limited, and may be polyvinyl alcohol, cellulose, water-soluble acrylic resin, emulsion, or the like. May be selected as appropriate.

The paste for an internal electrode is obtained by kneading the above-mentioned organic vehicle with the above-mentioned conductive material comprising various conductive metals or alloys or various oxides, organometallic compounds, resinates, etc. which become the above-mentioned conductive material after firing. It is prepared by The external electrode paste is also prepared in the same manner as the internal electrode paste.

The content of the organic vehicle in each of the above-mentioned pastes is not particularly limited, and may be a usual content, for example, about 1 to 5% by weight of a binder and about 10 to 50% by weight of a solvent. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like, as necessary.

When a printing method is used, a dielectric chip and an internal electrode paste are laminated and printed on a substrate such as polyethylene terephthalate, cut into a predetermined shape, and then separated from the substrate to obtain a green chip. On the other hand, when the sheet method is used, a green sheet is formed using a dielectric paste, an internal electrode paste is printed thereon, and these are laminated to form a green chip.

Next, the green chip is subjected to binder removal treatment and firing. The binder removal treatment is performed before firing, and may be performed under normal conditions. In particular, when a base metal such as Ni or a Ni alloy is used as the conductive material of the internal electrode layer, the temperature increase rate is 5 to 5 in an air atmosphere. 300 ° C./hour, more preferably 10 to 100 ° C./hour, and holding temperature of 180 ° C.
To 400 ° C, more preferably 200 to 300 ° C, and the temperature holding time is 0.5 to 24 hours, more preferably 5 to 2 hours.
0 hours.

The firing atmosphere of the green chip may be appropriately determined according to the type of the conductive material in the internal electrode layer paste. However, when a base metal such as Ni or a Ni alloy is used as the conductive material, the firing atmosphere may be changed. Oxygen partial pressure is 1 × 10 ⁻⁸ to 1
It is preferably set to × 10 ⁻¹² atm. If the oxygen partial pressure is too low, the conductive material of the internal electrode will be abnormally sintered and be interrupted, and if the oxygen partial pressure is too high, the internal electrode will be oxidized. In addition, the holding temperature for firing is 1,1.
00 to 1,400 ° C, more preferably 1,200 to
1,380 ° C. If the holding temperature is too low, the densification becomes insufficient, and if the holding temperature is too high, the capacitance-temperature characteristics are deteriorated due to breakage of the electrodes due to abnormal sintering of the internal electrodes or diffusion of the internal electrode material.

Other firing conditions include a heating rate of 50 to 500 ° C./hour, more preferably 200 to 30 ° C.
0 ° C./hour, a temperature holding time of 0.5 to 8 hours, more preferably 1 to 3 hours, a cooling rate of 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour, and a firing atmosphere Is preferably a reducing atmosphere. As the atmosphere gas, for example, a mixed gas of nitrogen gas and hydrogen gas is desirably used after being humidified.

When firing in a reducing atmosphere,
It is desirable to anneal the sintered body of the sub chip. A
Neal is a process to re-oxidize the dielectric layer.
Thereby, the insulation resistance can be increased. Anneal atmosphere
The oxygen partial pressure of the atmosphere is 1 × 10 ^-6More than atmospheric pressure, more preferred
1x10^-5~ 1 × 10^-4Pressure. Oxygen partial pressure
Is too low, it is difficult to reoxidize the dielectric layer, and the oxygen partial pressure
Is too high, the internal electrodes may be oxidized. Ani
The holding temperature during the cooling is preferably 1,100 ° C or less.
Or 500-1,100 ° C. Low holding temperature
Insufficient re-oxidation of the dielectric layer results in poor insulation resistance
And the accelerated life is shortened. Also, the holding temperature increases
If it breaks, the internal electrodes are oxidized and the capacity only decreases.
And reacts with the dielectric substrate, resulting in capacitance-temperature characteristics and insulation.
Resistance and its accelerated life deteriorate. Note that the annealing
It may be composed of only the warming step and the cooling step. This
In this case, the temperature holding time is zero and the holding temperature is
Synonymous with high temperature.

Other annealing conditions include a temperature holding time of 0 to 20 hours, more preferably 6 to 10 hours.
The cooling rate is 50 to 500 ° C./hour, more preferably 1 to 500 ° C./hour.
It is preferable to set the temperature to 00 to 300 ° C./hour and to use, for example, a nitrogen gas humidified as an atmosphere gas for annealing.

For the purpose of humidifying the nitrogen gas or the mixed gas in the above-described binder removal processing, firing and annealing steps, for example, a wetter or the like can be used. In this case, the water temperature is desirably 5 to 75 ° C.

The binder removal, firing and annealing may be performed continuously or independently of each other. In the case where these steps are continuously performed, the atmosphere is changed without cooling after the binder removal processing, the temperature is raised to the holding temperature at the time of firing, and firing is performed. When the temperature reaches the above, it is more preferable to change the atmosphere and perform the annealing treatment.

On the other hand, when these steps are performed independently, the firing is performed by raising the temperature in a nitrogen gas or humidified nitrogen gas atmosphere to the holding temperature during the binder removal treatment, and then changing the atmosphere. It is preferable to continue the temperature increase, and after cooling to the annealing holding temperature, it is preferable to change the atmosphere to a nitrogen gas or a humidified nitrogen gas atmosphere again and continue the cooling. Further, regarding the annealing, the atmosphere may be changed after the temperature is raised to the holding temperature in the nitrogen gas atmosphere, or the entire annealing process may be performed in a humidified nitrogen gas atmosphere.

The capacitor fired body obtained as described above is subjected to end surface polishing by, for example, barrel polishing or sandblasting, and printing or transferring an external electrode paste and firing to form external electrodes. The firing conditions for the external electrode paste are preferably, for example, about 10 minutes to 1 hour at 600 to 800 ° C. in a humidified mixed gas of nitrogen gas and hydrogen gas. Then, if necessary, a coating layer is formed on the surface of the external electrode by plating or the like.

The ceramic capacitor 1 of the present embodiment manufactured as described above is mounted on a printed circuit board by soldering or the like, and is used for various electronic devices.

[0051]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. In the following examples, the characteristics of the dielectric composition itself according to the present invention and the characteristics of the multilayer ceramic capacitor using the dielectric composition as a dielectric layer were evaluated.

[0052]Preparation of dielectric composition BaTiO₃(Hereinafter sometimes abbreviated as "BT")
), SrZrO₃(Hereinafter abbreviated as "SZ"
There is also) CaZrO₃(Hereinafter abbreviated as “CZ”)
In some cases), MgO and (BaCa) SiO₃Lumber
The powder was wet-mixed for 16 hours using a ball mill.
Was dried to obtain a dielectric material. Become a base material
BT, SZ and CZ are BaCO₃, CaCO₃,
SrCO₃ , TiO₂, Zirconium oxide (ZrO
₂) Are weighed and used for 16 hours using a ball mill.
After wet mixing and drying, 1,050 to 1,2
Ball milled at 50 ° C in air
For 20 to 60 hours. By the way
BT, SZ and CZ are hydrothermally synthesized powder, oxalate method, etc.
Therefore, similar characteristics can be obtained using the prepared raw materials.
Was.

Preparation of Multilayer Ceramic Capacitor Using the above composition, a multilayer ceramic capacitor was prepared. First, regarding the dielectric layer paste, 100% by weight of each dielectric material, 4.8% by weight of acrylic resin, 40% by weight of methylene chloride, 20% by weight of ethyl acetate, 6% by weight of mineral spirit and 4% by weight of acetone. Were mixed in a ball mill to form a paste.

As for the internal electrode paste, 100% by weight of Ni particles having an average particle size of 0.2 to 0.8 μm and 40% by weight of an organic vehicle (8% by weight of ethyl cellulose resin dissolved in 92% by weight of butyl carbitol) % And 10% by weight of butyl carbitol were kneaded with a three-roll mill to form a paste.

As for the paste for external electrodes, 100% by weight of Cu particles having an average particle size of 0.5 μm, 35% by weight of an organic vehicle (8% by weight of ethyl cellulose resin dissolved in 92% by weight of butyl carbitol), 7% by weight of carbitol was kneaded to form a paste.

Next, 4.5 μm and 15 μm thick green sheets are formed on the PET film using the above-mentioned dielectric layer paste, and the internal electrode paste is printed thereon. The sheet was peeled off. Next, a plurality of the green sheets thus obtained were laminated and pressed and pressed to produce a green chip. Number of stacked green sheets with internal electrodes is 4
Layers.

Next, the green chip was cut into a predetermined size and subjected to a binder removal treatment, firing and annealing to obtain a fired multilayer ceramic body.

This binder removal treatment is performed at a temperature rising time of 15 ° C.
/ Hour, a holding temperature of 280 ° C., a holding time of 8 hours, and an air atmosphere. In addition, firing is performed at a heating rate of 200 °.
C / hour, holding temperature of 1,200 to 1,380 ° C, holding time of 2 hours, cooling rate of 300 ° C / hour, of a mixed gas atmosphere of humidified nitrogen gas and hydrogen gas (1 × 10 ⁻⁹ atm) Performed under conditions. Annealing temperature 900 °
C, a holding time of 9 hours, a cooling rate of 300 ° C./hour, and a humidified nitrogen gas atmosphere (1 × 10 ⁻⁵ atm). Note that a wetter was used for humidification of each atmosphere gas, and the water temperature was 35 ° C.

Next, after polishing the end face of the laminated ceramic fired body by sand blasting, the external electrode paste was transferred to the end face, and fired at 800 ° C. for 10 minutes in a humidified nitrogen gas and hydrogen gas atmosphere. Thus, a sample of a multilayer ceramic capacitor was obtained (hereinafter, also referred to as a “capacitor sample”). The size of each sample is 3.2 mm x 1.6 mm x 0.6 mm
The thickness of the dielectric layer was 10 μm and 3 μm, and the thickness of the internal electrode was 2.0 μm.

With respect to each sample of the multilayer ceramic capacitor thus obtained, the capacitance-temperature characteristic and the third harmonic distortion (THD) were measured.

The composition molar ratio of BT, SZ and CZ and the average particle diameter of each sample, the kind of additive and the amount of additive were changed as shown in Tables 1 to 3, and the above-mentioned capacitor was changed. A sample was prepared.

Table 1 shows that MgO and (BaCa) SiO
₃ and the average particle diameter of BT, SZ and CZ were fixed (specifically, MgO = 2.0 mol%,
(BaCa) SiO ₃ = 2.8 mol%, average particle size of BT = 0.15 μm, average particle size of SZ = 0.1 μm, CZ
Is an example in which the composition molar ratio of BT, SZ and CZ is changed. Samples 1 to 23 are Examples of the present invention, and Samples 24 to 28 are Comparative Examples of the present invention. is there. FIG. 3 shows sample numbers corresponding to the respective composition molar ratios.

Table 2 shows that MgO and (BaCa) SiO
₃ and the composition molar ratio of BT, SZ and CZ were fixed (specifically, MgO = 2.0 mol%, (Ba
Ca) SiO ₃ = 2.8 mol%, BT = 0.55 mol%, SZ = 0.3 mol%, CZ = 0.15 mol%), B
This is an example in which the average particle size of T, SZ and CZ was changed,
9 to 32 are examples of the present invention, and sample 33 is a reference example of the present invention.

In Table 3, the composition molar ratios of BT, SZ and CZ and the average particle size are fixed (specifically, BT = 0.6 mol%, SZ = 0.25 mol%, CZ = 0.15). Mol%, B
Average particle size of T = 0.15 μm, average particle size of SZ = 0.1
μm, average particle size of CZ = 0.1 μm), MgO and (B
aCa) SiO ₃ is an example in which the additive amount of the additive is changed, and samples 34 to 37 are reference examples of the present invention. In addition, the sample 8 in Table 3 is the same as the one already described, and is shown for comparison.

The microstructure of the dielectric composition in this example was observed with a TEM microscope, and FIG. 5A schematically shows the structure. In view of this, the dielectric composition of the present embodiment is characterized in that the particles 2 composed of BT which is a ferroelectric are converted to SZ and CZ which are paraelectrics or a solid solution of SZ and CZ ((SrCa) ZrO ₃ ). It has a structure surrounded by particles 3 consisting of In particular, in the particles 2 composed of BT, Ca, Sr and Zr are diffused at a low concentration, and a portion 21 having a region showing a domain structure composed of almost pure BT, and Ca, Sr and Zr are diffused at a high concentration. Part 2 which does not have a region showing the domain structure
And a concentration gradient in which the concentration distribution of Ca, Sr, and Zr gradually increases from a portion 21 having a region showing a domain structure to a portion 22 having no region showing a domain structure. It was also confirmed that.

Evaluation Items and Evaluation Method For the capacitor sample, 1 kHz was measured using an LCR meter.
The capacitance under the conditions of z and 1 Vrms was measured.
The relative dielectric constant ε was calculated from the obtained capacitance, the electrode dimensions and the thickness of the sample.

Regarding the temperature characteristic of the capacitance, the capacitance of the capacitor sample was measured at a voltage of 1 V in a temperature range of -30 ° C. to + 85 ° C. using an LCR meter, and the reference temperature was set to 25 ° C. Then, it was examined whether or not the rate of change of capacity at the time of performing the measurement satisfied ± 15% or less (Y5R characteristic of EIA standard of Electronic Machinery Manufacturers Association). Tables 1 to 3 show the case of satisfying as “と し て” and the case of not satisfying as “×”.
The value of the capacity change rate at 5 ° C. is also shown.

With respect to the representative sample 1 satisfying the Y5R characteristic, the capacitance change rate ΔC / C in the temperature range of −30 ° C. to + 85 ° C. was graphed. In FIG.
The rate of change based on the capacity at 5 ° C. is shown.
As can be seen from the figure, it is understood that good temperature characteristics are exhibited.

The third harmonic distortion rate (THD) was determined for the capacitor sample by the EIAJ standard of the Japan Electronic Machinery Manufacturers Association.
The measurement was performed according to the procedure of the non-linearity measurement method of the fixed resistor of RC2111. The measuring instrument is RE-TECNOLOG
CLT-1 manufactured by Y-AS was used. An AC voltage of 10 kHz was applied to all capacitor samples at 0.3 V / μ.
The third harmonic distortion rate when applied at an electric field strength of m was measured.

The above results are shown in Tables 1 to 3. Tables 1-3
In the numerical value of the insulation resistance IR, “mE + n” is “m
× 10 ^{+ n} ”. In addition, although the evaluation results of the sinterability were not shown in these tables, there was no problem for the samples other than the sample 36. For sample 36, since (BaCa) SiO ₃ was not added, the sinterability was poor, and the sample could not be densified and could not be evaluated.

[0071]

[Table 1]

[0072]

[Table 2]

[0073]

[Table 3]

Discussion From the results in Table 1, it is understood that the composition molar ratios of BT, SZ and CZ are as follows. Samples 1 to 20 (FIG. 3
, 0.5 ≦ X ≦ 0.675, 0.1 <Y ≦ 0.
4, 0.075 ≦ Z <0.25, and X + Y + Z =
1) have a good balance between the dielectric constant, the strain rate, and the capacitance-temperature characteristic. Among them, samples 12 to 15 (FIG. 3)
In 0.525 ≦ X ≦ 0.675, 0.125 ≦
Y ≦ 0.375, 0.075 ≦ Z ≦ 0.225, and
X + Y + Z = 1), samples 1 to 11 (0.52
5 ≦ X ≦ 0.65, 0.15 ≦ Y ≦ 0.35, 0.1 ≦
Z ≦ 0.2 and X + Y + Z = 1).
There is a tendency that the above three characteristics are gradually balanced.
On the other hand, Samples 21 to 24 and 26, which are comparative examples,
The capacitance-temperature characteristics deteriorate, and in particular, the samples 24 and 26 greatly deviate from the Y5R standard. Samples 25, 27, and 28
Although the Y5R characteristic is satisfied, the third harmonic distortion rate TH
D is particularly deteriorating.

From the results in Table 2, it is understood that the average particle size of BT is as follows. The sample 32 (1 μm), the sample 31 (0.8 μm), the sample 29 (0.15 μm), and the sample 30 (0.3 μm) are gradually balanced in the dielectric constant, the distortion factor, and the capacitance-temperature characteristic. There is a tendency.
This is because, when the composition molar ratio of BT, SZ and CZ, and the amount of the additive are the same, as the average particle diameter of BT which is a ferroelectric material becomes smaller from 1.0 μm, The distortion rate decreases. On the other hand, the sample 33 (BT having an average particle size of 1.5 μm) as a reference example has a tendency that the third harmonic distortion rate THD is deteriorated.

From the results in Table 3, it is understood that the types and amounts of additives are as follows. From the comparison between Sample 34 and Sample 35, the relative dielectric constant ε
However, the insulation resistance IR, the capacitance-temperature characteristic, and the third harmonic distortion rate THD tend to deteriorate. On the other hand, if the added amount of MgO is too large, the relative dielectric constant ε tends to be low, and the capacitance-temperature characteristics tend to be deteriorated. Further, from the comparison between Sample 36 and Sample 37, (BaCa) SiO
_{If 3} is not added, densification tends to be difficult.
On the other hand, when the amount of (BaCa) SiO ₃ added is too large, the relative dielectric constant ε tends to decrease. Sample 35
From the comparison between sample and sample 37, the added amount of MgO was large (Ba
If the amount of Ca) SiO ₃ is small, the capacity-temperature characteristics tend to deteriorate. On the other hand, when the added amount of MgO is small and the added amount of (BaCa) SiO ₃ is large, the relative dielectric constant ε
Tends to decrease. By the way, (BaCa) SiO
₃ , SiO ₂ or Al ₂ O ₃ is added in place of ₃ ,
Each was evaluated under the same conditions as above, but the same result was obtained in each case.

The embodiments and examples described above have been described in order to facilitate understanding of the present invention, but are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments and examples includes all design changes and equivalents belonging to the technical scope of the present invention.

[0078]

As described above, according to the present invention,
Provided is a dielectric composition which is excellent in reduction resistance during firing, exhibits a high dielectric constant and a low distortion rate, and is excellent in capacitance temperature characteristics. Further, according to the present invention, there is provided a capacitor which has a high capacitance, a high insulation resistance, a low distortion rate, a flat capacitance-temperature characteristic, and can use a base metal for an internal electrode.

[Brief description of the drawings]

FIG. 1 is a ternary composition diagram of main components of a dielectric composition of the present invention.

FIG. 2 is a partially broken perspective view showing an embodiment of the multilayer capacitor of the present invention.

FIG. 3 is a ternary composition diagram showing composition molar ratios of Samples 1 to 31 in Examples.

FIG. 4 is a graph showing capacitance-temperature characteristics (Y5R) of the example.

FIG. 5A is a diagram schematically showing the microstructure of the dielectric composition according to the present example observed with a TEM microscope, and FIG. 5B is a diagram schematically illustrating the dielectric structure of the present invention. FIG. 2 is a view showing an example of a microstructure observed by a TEM microscope and schematically shown.

[Explanation of symbols]

1 ... multilayer ceramic capacitor 11 ... internal electrode 12 ... dielectric layer 13 ... external electrodes 2 ... portions 22 ... partial no region showing a domain structure 3 having a region exhibiting comprising particles 21 ... domain structure from BaTiO ₃ ... SZ Consisting of SZ and CZ or a solid solution of SZ and CZ

Continuation of the front page (72) Inventor Mikio Takahashi 1-13-1 Nihonbashi, Chuo-ku, Tokyo FDC term in TDK Corporation 4G031 AA04 AA05 AA06 AA11 AA12 AA39 BA09 CA04 GA03 5E001 AB03 AC03 AC09 AD03 AE00 AE01 AE02 AE03 AE04 AF00 AF06 AH01 AH05 AH06 AH08 AH09 AJ01 AJ02 5G303 AA01 AB06 AB11 AB20 BA12 CA01 CB03 CB06 CB32 CB35 CB39 CC03 CC08

Claims (8)

[Claims] 1. At least BaTiO₃, SrZrO
₃And CaZrO ₃A dielectric composition containing
At least for these three molar ratios, BaTiO₃Is less than or equal to 0.5 ≦ X ≦
0.675, SrZrO₃Is less than 0.1 <Y ≦
0.4, CaZrO₃Is less than 0.075 ≦ Z
<0.25, and X + Y + Z = 1.
object. 2. At least BaTiO₃, SrZrO
₃And CaZrO ₃A dielectric composition containing
Ba in which Ca, Sr and Zr are at least partially dissolved
TiO₃And SrZrO surrounding the particle₃And CaZrO₃,or
Has particles comprising these solid solutions.
The dielectric composition of the present invention. _3. The average particle diameter of the BaTiO ₃ is 1.
The dielectric composition according to claim 1, wherein the thickness is 0 μm or less. 4. The rate of change of capacitance with respect to temperature is at least ± 1 in a temperature range of −30 ° C. to + 85 ° C.
The dielectric composition according to claim 1, wherein the dielectric composition is within 5% (the reference temperature is 25 ° C.). 5. The dielectric composition according to claim 1, further comprising a reduction resistance auxiliary. 6. The dielectric composition according to claim 1, further comprising a sintering aid. 7. A ceramic capacitor having an internal electrode and a dielectric layer, wherein the dielectric layer is made of the composition according to claim 1. Description: . 8. The ceramic capacitor according to claim 7, wherein said internal electrode is made of Ni or a Ni alloy.