JP3183675B2 - Ceramic dielectric material, multilayer ceramic capacitor, and method for preventing deterioration of multilayer ceramic capacitor over time - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic dielectric material, a multilayer ceramic capacitor using the same, and a method for preventing the multilayer ceramic capacitor from deteriorating with time when a DC voltage is applied.

[0002]

2. Description of the Related Art Multilayer ceramic capacitors are widely used as small, large-capacity, highly reliable electronic components.
The number used in one electronic device is also large. In recent years, with the miniaturization and high performance of devices, demands for further miniaturization, large capacity, low price, and high reliability of multilayer ceramic capacitors have become more and more severe.

Attempts have been made to reduce the thickness of the dielectric layer in order to reduce the size and increase the capacity. However, as the dielectric layer becomes thinner, the electric field applied to the dielectric layer when a DC voltage is applied increases.

[0004] Incidentally, in capacitors belonging to Type II according to the JIS standard, ferroelectrics, particularly barium titanate, are used as dielectric materials because of their high dielectric constant. Among them, in a standard called X7R characteristic defined in the EIA standard, the rate of change of capacity is from -55 ° C to 125 ° C.
It is specified within 15% between ° C. In order to keep the dielectric constant within this standard, the Curie point must be
With the same temperature of 125 ° C. as in TiO ₃ , various additives are used to blur the peak of the Curie point to improve the temperature characteristics.

[0005] By the way, BaTiO ₃ takes a tetragonal phase in the ferroelectric region below the Curie point, and in X-ray diffraction (XRD), the peak (002) is slightly less than 2θ = 45 °;
It is known that a (200) peak is shown at 2θ slightly over 45 °, and that the ratio c / a of the lattice constant between the c-axis and the a-axis is about 1.01.

Accordingly, in a load test under moisture-resistant conditions, a DC electric field is applied in this ferroelectric region, and along this electric field, dipole moments due to spontaneous polarization are arranged, and the orientation to the c-axis is performed. Occurs. In particular, when the thickness of the dielectric layer is reduced so that an electric field of 0.2 V / μm or more is applied to the dielectric layer and the electric field intensity increases, the orientation along the c-axis is further promoted. If this orientation does not return even after the electric field is removed, the dielectric constant in the c-axis direction is low, so that the dielectric constant decreases. Since the orientation to the c-axis is accompanied by mechanical deformation due to elongation of the crystal axis, it is presumed that it is difficult to return to the initial state.

In addition, when there is a lattice defect,
The stabilization of the polarization due to the movement of lattice defects promotes this tendency. Therefore, it is considered that the change in capacitance in a DC voltage load test under moisture-proof conditions or the like is more or less an unavoidable phenomenon as long as it is a ferroelectric substance.

In order to improve such a defect, a low dielectric constant layer is formed at a grain boundary to concentrate an electric field, reduce an electric field applied to a ferroelectric portion, and control movement of lattice defects and c-axis orientation. There is an idea to reduce it.

[0009] is around dielectric constant epsilon ₁ of the crystal, when covered with alpha times the thickness of the crystal grain size to the dielectric constant epsilon ₂ of the material, when alpha 1, a dielectric constant which is combined with the voltage across the crystal, Both are ε ₂ / (αε ₁ + ε ₂ ) times the original. That is, if an electric field is concentrated by forming a layer having a low dielectric constant at the grain boundary and the electric field applied to the ferroelectric portion is reduced, the dielectric constant is reduced accordingly. Therefore, as long as this method is used, it is inevitable that there is a trade-off between the dielectric constant and the time-dependent change in capacitance when a DC electric field is applied.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problem that the dielectric constant is deteriorated with the lapse of time by the application of such a DC electric field, and that the dielectric constant is reduced when the deterioration with the lapse of time is reduced. SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic dielectric material which solves both of them, a multilayer ceramic capacitor using the same, and a method for preventing deterioration of the multilayer ceramic over time.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (17). (1) Barium titanate as a main component, and containing 1 to 10% by atom of a pentavalent donor ion for substituting Ti and / or a trivalent donor ion for substituting Ba with respect to 100 mol% of barium titanate. And further contains a divalent acceptor ion for substituting Ti in an atomic number of less than one time of the donor ion, has a Curie point of 85 ° C. or more, and has a c-axis and a a ceramic dielectric material ratio c / a of the lattice constants of the shaft comprises more than 40% in the ferroelectric crystal at a volume ratio is 1.005 or less, relative to 100 mol% of barium titanate, AM ²
_1/3 M ⁵ _2/3 O ₃ (A is one or more of Ba, Ca, Sr, M
² Mg, Co and Zn 1 or more, M ⁵ is Nb and / or Ta) converted at 1.5-6 mol% of A (M ²
_1/3 M ⁵ _2/3) ceramic dielectric of the composite oxide, and manganese oxide 0.1-2 mole% in terms of MnO, characterized in that it contains 1 mole% or less of barium oxide in terms of BaO Body material. (2) The ceramic dielectric material according to (1), which is fired in a neutral or reducing atmosphere. (3) The ceramic dielectric material according to the above (1) or (2), which has an average grain size of 0.3 to 1.5 µm and is fired at 1300 to 1400 ° C. (4) A multilayer ceramic capacitor, wherein the dielectric layer of the ceramic dielectric material according to any one of (1) to (3) is integrally formed with an internal conductor layer. (5) The thickness of the dielectric layer between the internal conductor layers is 100 μm.
m. The multilayer ceramic capacitor according to the above (4), which is not more than m. (6) When applying a DC voltage to the multilayer ceramic capacitor and using the same, use the multilayer ceramic capacitor described in (4) or (5) above to prevent the capacitance from deteriorating with time when the DC voltage is applied. A method for preventing deterioration of multilayer ceramic capacitors over time. (7) The method according to the above (6), wherein the electric field generated by the DC voltage is 0.02 V / μm or more. (8) For 100 mol% of barium titanate, AM ²
_1/3 M ⁵ _2/3 O ₃ (A is one or more of Ba, Ca, Sr, M
² Mg, Co and Zn 1 or more, M ⁵ is Nb and / or Ta) converted at 1.5-6 mol% of A (M ²
_1/3 M ⁵ _2/3) composite oxide, and manganese oxide 0.1-2 mole% in terms of MnO, a dielectric of a dielectric ceramic material containing a 1 mol% of barium oxide in terms of BaO A multilayer ceramic capacitor, wherein the layers are integrally formed with an internal conductor layer. (9) The multilayer ceramic capacitor according to (8), wherein the internal conductor layer is a base metal, and is integrally fired in a neutral or reducing atmosphere. (10) Barium titanate as a main component, and containing 1 to 10% by atom of a pentavalent donor ion for substituting Ti and / or a trivalent donor ion for substituting Ba with respect to 100 mol% of barium titanate. And further contains a divalent acceptor ion for substituting Ti in an atomic number of less than one time of the donor ion, has a Curie point of 85 ° C. or more, and has a c-axis and a a ceramic dielectric material ratio c / a of the lattice constants of the shaft comprises more than 40% in the ferroelectric crystal at a volume ratio is 1.005 or less, relative to 100 mol% of barium titanate, respectively, Nb ₂ 0.6 to a total of O ₅ and Ta ₂ O ₅ conversion
2 mol% of niobium oxide and / or tantalum oxide;
The total molar ratio of CoO and / or ZnO is N
A ceramic dielectric material containing 0.5 to 1 times of cobalt oxide and / or zinc oxide of b ₂ O ₅ and / or Ta ₂ O ₅ and fired in the air is used. The body layer is formed integrally with the inner conductor layer,
A method for preventing deterioration of capacitance with time when a DC voltage is applied by using a multilayer ceramic capacitor having a thickness of a dielectric layer between the internal conductor layers of 50 μm or less. . (11) The electric field generated by the DC voltage is 0.02 V / μm.
The method for preventing deterioration with time of a multilayer ceramic capacitor as described in (10) above. (12) The ceramic dielectric material has an average grain size of 0.3 to 1.5 μm,
The method according to any one of the above (9) to (11), wherein the multilayer ceramic capacitor is fired at 400 ° C. (13) Barium titanate as a main component, and containing 1 to 10% by atom of a pentavalent donor ion for substituting Ti and / or a trivalent donor ion for substituting Ba with respect to 100 mol% of barium titanate. And further contains a divalent acceptor ion for substituting Ti in an atomic number of less than one time of the donor ion, has a Curie point of 85 ° C. or more, and has a c-axis and a A dielectric layer using a ceramic dielectric material containing a ferroelectric crystal having a lattice constant ratio c / a of not more than 1.005 or less by volume ratio of not less than 40% by integral molding with a base metal inner conductor layer A monolithic ceramic capacitor, which is integrally fired in a neutral or reducing atmosphere, and wherein the thickness of the dielectric layer between the internal conductor layers is 50 μm or less. (14) One kind of yttrium oxide and lanthanoid oxide in a total of 0.6 to 4 mol% in terms of R ₂ O ₃ (R is Y and a lanthanoid element) with respect to 100 mol% of barium titanate. Above, M ² O respectively
(M ² is Mg, Ca and Co), and at least one kind of magnesium oxide, calcium oxide and cobalt oxide in a molar ratio of 0.5 to 1 times the total of yttrium oxide and lanthanoid oxide; The multilayer ceramic capacitor according to the above (13), comprising titanium oxide. (15) The ceramic dielectric material has an average grain size of 0.3 to 1.5 μm,
The multilayer ceramic capacitor according to the above (13) or (14), fired at 400 ° C. (16) When using the multilayer ceramic capacitor by applying a DC voltage to the multilayer ceramic capacitor, the multilayer ceramic capacitor according to any one of the above (13) to (15) is used.
A method for preventing deterioration of a multilayer ceramic capacitor with the lapse of time, characterized by preventing the deterioration with time of the capacitance when a DC voltage is applied. (17) The electric field due to the DC voltage is 0.02 V / μm
The method for preventing deterioration of a multilayer ceramic capacitor over time according to the above (16).

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[0021]

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[0024]

[0025]

[0026]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail. The ceramic dielectric material of the present invention is mainly composed of barium titanate. That is, even if the perovskite compound is barium titanate alone,
A perovskite compound in which the site (Ba) and the B site (Ti) are substituted with various known elements may be used.
In this specification, "barium titanate" also includes those substituted at the A and B sites.

As the A-site substitution element, A-site substitution divalent ions such as Sr and Ca can be used, and the substitution amount is generally 20 at% or less. The B-site-substituting element can be a B-site-substituted tetravalent ion such as Zr or Sn, and its substitution amount is generally 20 at% or less. In addition, SiO ₂ and various glass components such as Ba _{0.58 3}
Ca _0.417 SiO ₂ or the like may be contained in an amount of 6 mol% or less.

Such a ceramic dielectric material has a characteristic of 85 ° C. or more, generally 120 ° C. to 130 ° C., due to the characteristics of the capacitor.
Curie point of

Further, at a temperature lower than the Curie point, that is, in the ferroelectric state, such a ceramic dielectric material has a ratio c / a ≦ 1.00 of the lattice constant between the c-axis and the a-axis.
5 containing 40% or more by volume of the ferroelectric crystal. As a result, the deterioration of the capacitance with time when a DC electric field is applied is reduced critically.

Such a microscopic crystal structure can be confirmed by X-ray diffraction (XRD) or neutron diffraction. That is, for example, in XRD using CuKα, in the tetragonal phase BaTiO ₃ , the c-axis (002) peak is 2θ =
44.95 °, a-axis (200) peak 2θ = 45.4
1 °, lattice constant a = 3.9947, b = 4.03
36, c / a = 1.0097, atomic coordinates Baz = 0,
Tiz = 0.512, and the result is the same in neutron diffraction.

On the other hand, in the present invention, a is larger than these, c is smaller, and c / a ≦ 1.005, usually c / a =
0.995 to 1.005, the atomic coordinate z of Ti> 0.5
Another phase, also called a pseudo-cubic phase, is generated in addition to or in place of the tetragonal phase. As a result, in XRD and neutron diffraction,
A new single peak is generated between the (002) peak and the (200) peak, or the (002) peak or the (200) peak is placed on the shoulder of this new peak.

When the Rietveld analysis of these samples was performed using the RIETAN program, c
The crystal having a peak of /a≦1.005 has a volume ratio of 40
%, Especially 50% or more, and more preferably 60 to 100%. Rietveld analysis using the RIETAN program was performed by Fujio Izumi, Hajime Asano, and others.
Appl. Crystallogr. 20 1987 P411.

In order to generate such a pseudo-cubic phase with c / a ≦ 1.005, for example, a predetermined amount of various donors such as Nb to be described later is added, or the grain size, sintering temperature, sintering temperature, etc. By controlling the sintering atmosphere or the like, the generation conditions can be easily obtained from experiments.

Under such a premise, the c / a of the present invention
As a composition effective for forming a pseudo-cubic phase of ≦ 1.005, 100 mol% of barium titanate and Ti
A pentavalent donor ion replacing the site and / or B
The trivalent donor ion for substituting the a site is 1 to
Those containing 10% are preferred. Due to the inclusion of the donor,
Although a pseudo-cubic phase is likely to be generated, if the amount of the donor is too large, sintering becomes difficult, or a different phase is generated to lower the dielectric constant.

In such a case, the pentavalent donor ion includes one or more of Nb ⁵⁺ , Ta ⁵⁺ , and V ⁵⁺ , especially Nb ⁵⁺ and / or Ta ⁵⁺ . Examples of the trivalent donor include one or more of Y ³⁺ and R ³⁺ (R is a lanthanoid element), and R ³⁺ includes Ce ³⁺ , La ³⁺ ,
Pr ³⁺ , Sm ³⁺ , Gd ³⁺ , and Nd ³⁺ are preferred. The number of atoms per 100 mol% of barium titanate of the donor ion is particularly preferably 1 to 8%.

As described above, when a donor ion is contained,
In order to improve the temperature characteristics, the sinterability, the specific resistance, and the like, it is preferable to further contain a divalent acceptor ion that replaces Ti. However, as the number of acceptor ions increases, the effect of adding the donor decreases, and therefore, the number of atoms is preferably less than 1 times the total number of donors, particularly preferably 0.1 to 0.5 times. As the divalent acceptor, Mg ²⁺ , Zn ²⁺ , Mn ²⁺ , and Co ²⁺ are preferable.

These donors and acceptors may be added to the starting barium titanate compound in the form of an oxide or a precursor that becomes an oxide upon firing, or may be added in the form of a composite perovskite compound. When adding a donor or an acceptor, the ratio A / B of the number of atoms at the A site to the number of atoms at the B site is about 1, preferably 1.010 to 1.0.
For the purpose of keeping at 0.998, the raw material barium titanate contains:
Titanium, barium, an oxide such as an A-site substituted divalent ion element or a B-site substituted tetravalent ion element, or the like may be added.

In such a case, particularly preferred first composition systems include Nb ⁵⁺ and / or Ta ⁵⁺ , especially Nb ⁵⁺
Is a donor and niobium oxide and / or tantalum oxide are added. The content of niobium oxide and / or tantalum oxide is based on 100 mol% of BaTiO ₃ .
In _{Nb 2 O 5, Ta 2 O} 5 in terms of, preferably in the 0.6 to 2 mol%, in particular 0.8 to 1.5 mol%. The pseudo cubic phase is effectively generated in such a range. In such a case, the Nb donor alone or a part thereof
Those substituted with a are preferred.

It is preferable that such a composition contains cobalt oxide and / or zinc oxide as an acceptor, particularly for the purpose of improving temperature characteristics and improving sinterability. These contents are expressed in terms of a molar ratio of the total of CoO and ZnO, and are 0.1% of the total of Nb ₂ O ₅ and Ta ₂ O ₅ .
Preferably it is 5 to 1 times.

The ceramic dielectric of such a composition system is as follows:
To a barium titanate powder, a predetermined amount of powder of Nb ₂ O _{5 and the} like, and a powder of CoO and / or ZnO are mixed, and a known organic binder, a vehicle containing a solvent or the like is added thereto, and a moldable state is obtained. After that, it is manufactured by sintering it alone or integrally with the conductor material. The firing is performed in the atmosphere at about 1300 ° C. to 1400 ° C., particularly 13 ° C.
What is necessary is just to carry out at about 50-1400 degreeC. As the conductor material, a noble metal material such as palladium, silver palladium, and platinum is preferable.

A preferred second composition system is also N
b ⁵⁺ or Ta ⁵⁺ as a donor, wherein 0.1 to 2 mol% of manganese oxide in terms of MnO and 1 mol% or less, particularly 0% in terms of BaO, based on 100 mol% of barium titanate 0.1 to 1 mol% of barium oxide, for example, BaMg
Of 1.5-6.0 mol% in _1/2 Nb _2/3 O ₃ in terms Ba-
And a composite perovskite compound such as an Mg-Nb compound.

As such a composite perovskite compound, an AM ² _1/3 M ⁵ _2/3 O ₃ compound may be used in addition to a Ba—Mg—Nb compound. Here, A is Ba, Ca, Sr
Of these, Ba is an essential component, and it is preferable to include these 1 to 3 types. M ² is,
There are one to three kinds of Mg, Co, and Zn, and it is preferable to include one to three kinds of these with Mg as an essential component.
M ⁵ is Nb and / or Ta, and preferably contains Nb.

By the composite perovskite, a predetermined amount of donor is added to facilitate the formation of a pseudo-cubic phase, and the composite perovskite and manganese oxide form
A predetermined amount of the acceptor is added. The addition of manganese oxide makes it possible to improve the sinterability and prevent the reduction of the ceramic, and the addition of barium oxide makes it possible to prevent the reduction of the ceramic.

The ceramic dielectric of such a composition system is as follows:
A predetermined amount of MnCO ₃ powder in barium titanate powder,
It is manufactured by mixing BaCO ₃ powder and composite perovskite compound powder, adding a vehicle to form a moldable state, and firing the mixture alone or with a conductor material. The calcination may be performed in the air, but the oxygen partial pressure is 1
It is preferable to use a neutral atmosphere or a reducing atmosphere (for example, N ₂ + H ₂ + H ₂ O) at 0 ⁻⁶ to 10 ⁻¹² atm.
The firing temperature is from 1300 to 1400 ° C, especially from 1350 to 14
00 ° C is preferred. This makes it possible to use a base metal inner conductor such as nickel or a nickel alloy.

Further, a preferred third composition system uses a trivalent ion of Y or a litanoid element as a donor. Yttrium oxide and lanthanoid oxide 1
The total content of at least one species is 0.6 to 4 mol%, particularly 1.0 to 3.0 mol% in terms of R ₂ O ₃ (R is Y and a lanthanoid element) based on 100 mol% of barium titanate. 0 mol%, and M ² O (M is M
g, Ca and Co) in terms of 0.1% of the total amount of R ₂ O ₃ .
It contains one or more of magnesium oxide, cobalt oxide and calcium oxide in an amount of 5-1 mole times. This acceptor is also suitable in terms of preventing reduction.

Further, preferably, the ratio A / B of the number of atoms at the A site to the number of atoms at the B site is 1.00.
Before and after, preferably 0.998 to 1.010
Preferably, iO ₂ is added.

To obtain such a composition system, a predetermined amount of TiO ₂ powder, R ₂ O ₃ powder and M ² O powder are mixed with barium titanate powder, and the same as in the second composition system, After the mold is ready to be molded, 1
It is preferable to bake at 300 to 1400 ° C. And it becomes possible to use a base metal inner conductor such as Ni.

The average grain size in these ceramic dielectric materials is generally preferably about 0.3 to 1.5 μm. And it has a good dielectric constant.

Such a ceramic dielectric material is laminated with an internal conductor to form a multilayer ceramic capacitor.
The thickness of each dielectric layer of the ceramic dielectric material after firing is 100 μm or less, particularly 50 μm or less, and more preferably about 5 to 30 μm. In the first and third composition systems, the thickness is 50 μm or less. The present invention is effective in preventing the capacitance of a multilayer ceramic capacitor having such a thin dielectric layer from changing over time. The number of stacked dielectric layers is usually about 2 to 200.

The lamination and integration of the ceramic dielectric material and the internal conductor material may be performed by a green sheet method or a printing method. After laminating these, firing is performed. The firing can be performed in the atmosphere using a noble metal material as an internal conductor. Further, the preferred second and third composition systems described above can be carried out in a neutral or reducing atmosphere having an oxygen partial pressure of 10 ⁻⁶ atm or less, and have an advantage that a base metal material can be used as an internal conductor. In each case, a sufficient capacitance and a high resistance of 10 ¹⁰ Ω or more can be obtained, and a multilayer ceramic capacitor having sufficient mechanical strength without defects such as delamination can be obtained.
Note that the multilayer ceramic capacitor is provided with a pair of external electrodes that conduct with the internal conductor. Various known materials can be applied as the external electrode material.

Such a multilayer ceramic capacitor is
During use, a DC electric field of 0.02 V / μm or more, particularly 0.2 V / μm or more, more preferably 0.5 V / μm or more, and generally about 5 V / μm or less per 1 μm of the dielectric layer is usually superimposed on this. An AC component is applied. Even when such a DC electric field is loaded by the generation of the pseudo cubic phase according to the present invention, the change with time of the capacitance is extremely small.

[0052]

The present invention will be described in more detail with reference to the following examples. Example 1 BaCO ₃ and TiO ₂ were weighed to a molar ratio of 1: 1 and mixed with garnet in water and mixed in air with 110
It was calcined at 0 ° C. for 2 hours. Into a crushed calcined product,
Nb ₂ O ₅ (0.2 to 1.0 mol%), Co ₃ O ₄
(0.25 mol%), mixed in the same manner, dehydrated and dried to obtain a raw material powder.

This powder was added to polyvinyl alcohol (PV
A) An aqueous solution was added, granulated, and pressed into a disk shape.
The firing was performed at 1360 ° C. in the air. A part of the fired sample was ground in an agate mortar to obtain a sample for XRD and neutron diffraction. FIG. 1 shows the results of XRD using CuKα.

As shown in FIG. 1, when the added amount of Nb ₂ O ₅ exceeds 0.4 mol%, the (200) peak and (0
02) The peaks approached, the ratio of the lengths of the c-axis and the a-axis became almost 1, and the structure was almost cubic. However, the Curie point remained at 125 ° C. from the temperature characteristics of the capacitance. Since there is a sudden change in the dielectric constant at 125 ° C., there is no doubt that it is a ferroelectric. The grain size is 0.4
0.8 μm, irrespective of the amount of Nb ₂ O ₅ except in the case of mol%
m.

XR in the range of 2θ = 20 ° to 120 °
Rietveld analysis was performed using the D data to determine the volume ratio of the ferroelectric crystal in which the ratio c / a between the c-axis and the a-axis was 1.005 or less. Table 1 shows the results.

[0056]

[Table 1]

Table 2 shows the result of neutron diffraction of Sample No. 5. Thus, sample Nos. 5 and N
In o.4, 82% and 73% of pseudo-cubic phases with c / a = 0.9962 were formed, respectively. In addition,
Sample Nos. 4 and 5 had a dielectric constant at room temperature of about 4200.

[0058]

[Table 2]

Next, Green 10 of Sample Nos. 1 to 5
A Pd paste was printed on a sheet, laminated, and fired in the air under the above conditions. Thereafter, Ag external electrodes were further formed to produce five types of multilayer ceramic capacitors.
The thickness per dielectric layer after firing was 25 μm.

Each of the thus obtained capacitors is connected to 15
Heat treated at 0 ° C for 1 hour, set at room temperature for 24 hours, LCR
Measure the capacitance with a meter under the conditions of 1kHz and 1Vrms,
Initial value. Then, at 40 ° C,
A voltage of 25 V is applied, a DC electric field of 1 V / μm is applied for a certain period of time, and then left at room temperature for 24 hours under no load, and the capacitance is measured under the same conditions as above, and the initial capacitance is measured. Was calculated. After 100 hours and 1000
The results after the time are shown in Table 1.

From the results shown in Table 1, c / a ≦ 1.0
It can be seen that when the 05 phase is formed at 40% by volume or more, the change over time in the capacity is critically reduced. The resistance of the capacitors using Sample Nos. 4 and 5 was 10 ¹⁰ Ω or more, and the capacitors exhibited sufficient resistance and were free from defects such as delamination.

Example 2 A composite perovskite compound BaM was prepared from a carbonate and an oxide.
g _1/3 Nb _2/3 O ₃ was synthesized. MnCO ₃ 0.5 mol% relative to BaTiO ₃ 100 mol%, BaCO ₃
0.5 mol%, and complex perovskite compound
5 mol% or 2.0 mol% were mixed, to which was added an organic binder, molded, the O ₂ partial pressure of 10 ^{-1 0} atm N ₂ -
It was fired in an H ₂ -H ₂ O atmosphere.

FIG. 2 shows the amount of composite perovskite added.
XRD of 0.5 mol% and 2.0 mol% are shown. FIG.
From the equation, when 2.0 mol% is added, c / a = 1.00
It can be seen that the pseudo cubic phase No. 3 was generated.
In this case, BaMg _1/3 when Nb _2/3 O 3 is more than 1.5 mol%, the volume ratio of the ferroelectric crystal ratio c / a is 1.003 and c-axis and a-axis of 60% That's all. Also,
In the case of adding 2.0 mol% of the composite perovskite compound,
The Curie point was 125 ° C., and the dielectric constant at room temperature was 2,800.

Next, such a composite perovskite
Using a 2.0 mol% added ceramic dielectric, a Ni paste was printed and laminated on the green sheet, and sintered in the above atmosphere to produce a multilayer ceramic capacitor having the same size as in Example 1. . The resistance of the obtained capacitor was 10 ¹⁰ Ω or more, and there was no defect such as delamination. Further, the rate of change of the capacity after 1000 hours was also 0, and it was confirmed that the change in capacity when a DC voltage was applied was critically reduced due to the formation of c / a ≦ 1.005 phase.

Example 3 1.0 mol% of MgO, 0.5 mol% of TiO ₂ , La ₂ O ₃ and Pr ₂ with respect to 100 mol% of BaTiO ₃
The mixture was mixed with 2.0 mol% of O ₃ or Y ₂ O ₃ , added with an organic binder, molded, and fired in a N ₂ -H ₂ -H ₂ O atmosphere having an O ₂ partial pressure of 10 ⁻¹⁰ atm. Their Curie point was 125 ° C.

FIG. 3 shows the XRD. From FIG. 3, c / a
It can be seen that a pseudo-cubic phase of ≦ 1.005 was generated. In these, the ratio c / a between the c-axis and the a-axis is
Is 60% or less by volume
The above was generated.

Further, using such a ceramic dielectric green sheet, a Ni paste was printed and laminated on the green sheet, and sintering was performed in the above atmosphere to produce a multilayer ceramic capacitor having the same size as that of Example 1. . As a result, the capacity change rate after 1000 hours was 0, and c / a ≦
Due to the formation of the 1.005 phase, the change in capacity when the DC voltage was applied was critically reduced. The resistance of each capacitor is 10
¹⁰ Ω or more, and no defects such as delamination occurred.

[0068]

According to the present invention, the deterioration with time of the capacitance of a multilayer ceramic capacitor used by applying a DC voltage is significantly reduced.

[Brief description of the drawings]

FIG. 1 shows an X-ray diffraction (X-ray diffraction) of a ceramic dielectric material of the present invention.
It is a RD) chart.

FIG. 2 is an XRD chart of the ceramic dielectric material of the present invention.

FIG. 3 is an XRD chart of the ceramic dielectric material of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kosuke Nishiyama 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-3-112860 (JP, A) JP-A Heisei 3-112861 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/42-35/49 CA (STN) REGISTRY (STN)

Claims (17)

(57) [Claims] 1. A barium titanate as a main component, wherein 100 mol% of barium titanate has a pentavalent donor ion for substituting Ti and / or a trivalent donor ion for substituting Ba in an amount of 1 to 10 atoms. %, And further contains less than 1 time of the above-mentioned donor ion in terms of the number of atoms of the divalent acceptor ion which substitutes for Ti, has a Curie point of 85 ° C. or more, and has a c-axis at a temperature lower than the Curie point. The ratio c / a of the lattice constant between the a axis and the a axis is 1.
A ceramic dielectric material containing at least 40% by volume of a ferroelectric crystal of 005 or less, wherein AM ² _1/3 M ^{5 is} added to 100 mol% of barium titanate.
_2/3 O ₃ (A is at least one of Ba, Ca and Sr, M ² is M
g, one or more of Co and Zn, and M ⁵ is 1.5 to 6 mol% of A (M ² _1/3 M ⁵ ) in terms of Nb and / or Ta).
_2/3 ) A ceramic dielectric material comprising a composite oxide, 0.1 to 2 mol% of manganese oxide in terms of MnO, and 1 mol% or less of barium oxide in terms of BaO. 2. The ceramic dielectric material according to claim 1, fired in a neutral or reducing atmosphere. 3. An average grain size of 0.3 to 1.5 μm.
m and calcined at 1300-1400 ° C.
Or the ceramic dielectric material according to 2. 4. A multilayer ceramic capacitor, wherein a dielectric layer of the ceramic dielectric material according to claim 1 is integrally formed with an internal conductor layer. 5. The method according to claim 1, wherein the thickness of the dielectric layer between the inner conductor layers is 1
The multilayer ceramic capacitor according to claim 4, wherein the thickness is not more than 00 µm. 6. A capacitor according to claim 4 or 5, wherein a DC voltage is applied to the multilayer ceramic capacitor to prevent the capacitor from deteriorating with time when a DC voltage is applied. Method for preventing deterioration of laminated ceramic capacitor over time. 7. An electric field generated by the DC voltage is 0.02 V /
7. The method for preventing deterioration of a multilayer ceramic capacitor over time according to claim 6, which is not less than μm. 8. With respect to 100 mol% of barium titanate,
AM ² _1/3 M ⁵ _2/3 O ₃ (A is one or more of Ba, Ca, Sr, M ² is one or more of Mg, Co and Zn, M ⁵ is N
b and / or 1.5-6 mol% of A in terms of Ta)
(M ² _1/3 M ⁵ _2/3 ) composite oxide and 0.1 in terms of MnO
A multilayer ceramic capacitor, wherein a dielectric layer of a dielectric ceramic material containing マ ン ガ ン 2 mol% of manganese oxide and 1 mol% or less of barium oxide in terms of BaO is integrally formed with an internal conductor layer. 9. The multilayer ceramic capacitor according to claim 8, wherein said internal conductor layer is a base metal and is integrally fired in a neutral or reducing atmosphere. 10. A pentavalent donor ion for replacing Ti and / or a trivalent donor ion for replacing Ba in an amount of 1 to 10 containing barium titanate as a main component and 100 mol% of barium titanate. %, And further contains less than 1 time of the above-mentioned donor ion in terms of the number of atoms of the divalent acceptor ion which substitutes for Ti, has a Curie point of 85 ° C. or more, and has a c-axis at a temperature lower than the Curie point. The ratio c / a of the lattice constant between the a axis and the a axis is 1.
A ceramic dielectric material containing at least 40% by volume of a ferroelectric crystal of 005 or less, and 100 mol% of barium titanate and Nb, respectively.
0.6 to 2 mol% in total in terms of ₂ O ₅ and Ta ₂ O ₅
Nb ₂ O ₅ , in terms of the total molar ratio of niobium oxide and / or tantalum oxide to CoO and / or ZnO
And / or a ceramic dielectric material containing 0.5 to 1 times of cobalt oxide and / or zinc oxide of Ta ₂ O ₅ and fired in the air, wherein the dielectric layer of the ceramic dielectric material is The use of a multilayer ceramic capacitor formed integrally with the internal conductor layer and having a thickness of the dielectric layer between the internal conductor layers of 50 μm or less to prevent deterioration with time of the capacitance when a DC voltage is applied. To prevent deterioration of laminated ceramic capacitors over time. 11. The electric field generated by the DC voltage is 0.02
The method for preventing deterioration of a multilayer ceramic capacitor over time according to claim 10, which is not less than V / μm. 12. The ceramic dielectric material according to claim 1, wherein the average grain size is 0.3 to 1.5 μm.
The method for preventing deterioration with time of a multilayer ceramic capacitor according to any one of claims 9 to 11, wherein the method is fired at 0 to 1400 ° C. 13. A pentavalent donor ion for substituting Ti and / or a trivalent donor ion for substituting Ba in an amount of 1 to 10 containing barium titanate as a main component and 100 mol% of barium titanate. %, And further contains less than 1 time of the above-mentioned donor ion in terms of the number of atoms of the divalent acceptor ion which substitutes for Ti, has a Curie point of 85 ° C. or more, and has a c-axis at a temperature lower than the Curie point. The ratio c / a of the lattice constant between the a axis and the a axis is 1.
A dielectric layer using a ceramic dielectric material containing at least 40% by volume of a ferroelectric crystal of 005 or less is integrally formed with an inner conductor layer of a base metal, and integrally fired in a neutral or reducing atmosphere. Wherein the thickness of the dielectric layer between the internal conductor layers is set to 50 μm or less. 14. A total of 0.6 to 4 mol% of yttrium oxide and lanthanoid oxide in terms of R ₂ O ₃ (R is Y and a lanthanoid element) with respect to 100 mol% of barium titanate. One or more kinds of magnesium oxide and calcium oxide in a molar ratio of 0.5 to 1 times the sum of yttrium oxide and lanthanoid oxide in terms of M ² O (M ² is Mg, Ca and Co). 14. The multilayer ceramic capacitor according to claim 13, comprising one or more of cobalt oxide and titanium oxide. 15. The ceramic dielectric material according to claim 15, wherein said ceramic dielectric material has an average grain size of 0.3 to 1.5 μm.
The multilayer ceramic capacitor according to claim 13, which is fired at 0 to 1400 ° C. 15. 16. When applying a DC voltage to a multilayer ceramic capacitor for use, the multilayer ceramic capacitor according to claim 13 is used.
A method for preventing deterioration of a multilayer ceramic capacitor with the lapse of time, characterized by preventing the deterioration with time of the capacitance when a DC voltage is applied. 17. The electric field generated by the DC voltage is 0.02
17. The method for preventing deterioration of a multilayer ceramic capacitor over time according to claim 16, which is not less than V / μm.