JPH08171814A - Dielectric ceramic composition and laminated ceramic capacitor using thereof - Google Patents

Abstract

PURPOSE: To provide a dielectric ceramic composition with high dielectric constant in spite of small grain size, small temperature and voltage dependence of the dielectric constant, and high dielectric breakdown voltage and a laminated ceramic capacitor using the ceramic composition. CONSTITUTION: A dielectric ceramic composition contains 83.3-96.7 mole % of BaTiO3 in which the content of alkali metal oxide impurity is not more than 0.03wt.%, 1.4-5.0 mole % (in conversion into LaO3/2 , CeO2 , PrO11/6 , NdO3/2 , SmO3/2 ) of at least one oxide selected from lanthanum oxide, cerium oxide, praseodymium oxide, and samarium oxide, 0.5-6.7 mole % of CaZrO3 , and 1.4-5.0 mole % of TiO2 . A laminated ceramic capacitor is composed by using the dielectric ceramic composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition and a laminated ceramic capacitor using the same.

[0002]

2. Description of the Related Art Heretofore, many dielectric ceramic compositions mainly composed of BaTiO ₃ have been known for use in ceramic capacitors. BaTiO ₃ is 120
It has a Curie point near ℃ and 10,000 near that temperature.
Although it has a high dielectric constant, it is low at room temperature. Therefore, a material called a shifter material is added to move the Curie point to room temperature so that a high dielectric constant can be obtained at room temperature. As the shifter material, Sn oxide, Zr oxide, rare earth oxide, etc. are known.

BaTi using such a shifter material
As a ceramic capacitor mainly composed of O ₃ , a single plate type with lead wire has been manufactured. However, in recent years, the lamination technology has advanced, and it has become possible to easily obtain a dielectric green sheet having a thickness of about 30 to 80 μm. Then, so-called multilayer ceramic capacitors in which a plurality of layers are laminated by sandwiching a dielectric thin film between internal electrodes have entered the electronics industry, and conventional dielectric ceramic compositions are also used as materials for such multilayer ceramic capacitors. became.

On the other hand, recent ceramic capacitors tend to be miniaturized, and particularly in laminated ceramic capacitors, the thickness of the porcelain dielectric layer tends to be as thin as 6 to 10 μm. In this case, 100-10,000μ
Compared to a single-plate type capacitor having a thickness of m, it receives electric field strength ten times or more. Therefore, there is a demand for a composition having a smaller voltage dependency than a single plate capacitor.

Further, as the thickness of the dielectric layer becomes thinner, the characteristics are more likely to be affected by structural defects in the ceramic, so that the crystal grain size (grain size) is uniform and fine, and the pores are Is desired to be small and small.

Examples of the dielectric ceramic composition mainly composed of BaTiO _{3 and} having a small grain size include, for example, Japanese Patent Application Nos. 56-18059, 57-16809, 57-105919, and 57-105919. 57-196469
It is disclosed in Japanese Patent Publication No. These are BaTiO ₃ with CeO ₂ , or CeO ₂ and BaZrO ₃ , or Nd.
The grain size of BaTiO ₃ is reduced by adding ₂ O ₅ .

[0007]

However, in the conventional dielectric ceramics having a small grain size, the dielectric constant is about 10,000 at maximum at room temperature, and the dielectric constant is lower than that of a large grain size, and the multilayer capacitor is small. However, it was difficult to obtain a large capacitance.

Further, there is a problem that the change in the dielectric constant with temperature is sharp, and if an additive is added to improve the change, the dielectric constant is lowered to around 7,000 at room temperature.

Therefore, an object of the present invention is to provide a dielectric ceramic composition which has a high dielectric constant even though the grain size is small, has a small temperature and voltage dependency of the dielectric constant, and has a high dielectric breakdown voltage. And to provide a laminated ceramic capacitor using the same.

[0010]

In order to achieve the above object, the dielectric ceramic composition of the present invention comprises:
Content of alkali metal oxides as impurities is 0.03
83.3-96.7 mol% of BaTiO ₃ in an amount of not more than wt%
On the other hand, at least one selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, and samarium oxide is replaced with LaO _3/2 and Ce, respectively.
O _2, PrO _11/6 ,, NdO 1.4~5.0 mol% in terms of _3/2 and SmO _3/2, 0.5 to the CaZrO ₃
It is characterized by containing 6.7 mol% and 1.4 to 5.0 mol% of TiO ₂ .

In the second aspect, the content of the alkali metal oxide as an impurity is 0.03% by weight or less.
With respect to 83.3 to 96.7 mol% of aTiO ₃ , at least one selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide and samarium oxide is added to LaO _3/2 , CeO ₂ , PrO, respectively.
_{Converted to 11/6} , NdO _3/2 and SmO _3/2 , 1.4-
5.0 mol%, CaZrO ₃ 0.5 to 6.7 mol%,
And 100 parts by weight of the main component containing 1.4 to 5.0 mol% of TiO ₂ , and BaO-SrO-CaO-Li ₂ O-
The glass containing SiO ₂ as a main component has a subcomponent of 0.3.
.About.2.5 parts by weight.

The laminated ceramic capacitor of the present invention is the same as that of claim 3 in which a plurality of dielectric ceramic layers are provided.
In a monolithic ceramic capacitor comprising a plurality of internal electrodes arranged via the dielectric ceramic layer and external electrodes connected to the internal electrode, the dielectric ceramic layer contains an alkali metal oxide as an impurity. BaTiO ₃ in an amount of 0.03% by weight or less is 83.3 to 9
With respect to 6.7 mol%, lanthanum oxide, cerium oxide,
At least one selected from praseodymium oxide, neodymium oxide, and samarium oxide is La, respectively.
O _3/2 , CeO ₂ , PrO _11/6 , NdO _3/2 and SmO
Converted to _3/2 , 1.4 to 5.0 mol%, CaZrO ₃ 0.5 to 6.7 mol%, and TiO ₂ 1.4 to 5.0.
It is characterized in that it is composed of a dielectric material containing mol%, and that the internal electrodes are composed mainly of palladium.

The multilayer ceramic capacitor according to claim 4, comprising a plurality of dielectric ceramic layers, a plurality of internal electrodes arranged via the dielectric ceramic layers, and external electrodes connected to the internal electrodes. In the dielectric ceramic layer, the content of the alkali metal oxide as an impurity is 0.03% by weight or less with respect to BaTiO ₃ of 83.3 to 96.7 mol% with respect to lanthanum oxide, cerium oxide, and oxidation. At least one selected from praseodymium, neodymium oxide and samarium oxide,
LaO _3/2 , CeO ₂ , PrO _11/6 , NdO respectively
1.4 to 5.0 mol% in terms of _3/2 and SmO _3/2 ,
The main component containing 0.5 to 6.7 mol% of CaZrO ₃ and 1.4 to 5.0 mol% of TiO ₂ and 100 parts by weight of BaO—SrO—CaO—Li ₂ O—SiO ₂ are mainly used. It is characterized in that it is composed of a dielectric material composed of 0.3 to 2.5 parts by weight of a sub-component composed of glass as a component, and the internal electrode is composed mainly of palladium. .

[0014]

EXAMPLES The present invention will now be described based on examples. In the table below, sample numbers marked with * indicate those outside the scope of the present invention.

Example 1 First, a BaTiO ₃ raw material powder was prepared. That is, BaCO ₃ and TiO ₂ of various purities
Were weighed so that the molar ratio of BaCO ₃ and TiO ₂ was 1.000, wet-mixed for 16 hours by a ball mill using zirconia boulders, and then evaporated to dryness to obtain a mixed powder. . The obtained mixed powder was calcined in a natural atmosphere at 1150 ° C. for 2 hours, and then ground again with a ball mill until the average particle size became 2 μm or less.
Thus, four kinds of BaTiO ₃ shown in A, B, C and D of Table 1 having different purities were obtained.

Next, this BaTiO ₃ is added to 83.3-9.
Against 6.7 mol%, such that the composition ratio shown in Table _{2, La 2 O 3, CeO} 2, Pr 6 O 11, Nd 2 O 3,
Sm ₂ O ₃ , CaZrO ₃ and TiO ₂ were weighed, a vinyl acetate resin binder was added, and wet mixing was performed for 16 hours to obtain a mixture. Then, this mixture is dried and granulated, and then 20
10 mm diameter and 0.6 m thickness at a pressure of 00 kg / cm ^2.
It was molded into a disk of m. Then, the disc was fired at the temperature shown in Table 3 for 2 hours to obtain a disc-shaped porcelain.

Thereafter, the surface of this porcelain was observed at 2000 times with an electron microscope to measure the grain size.

Next, silver electrodes were baked on both sides of the obtained porcelain to obtain a measurement sample (capacitor). Then, the dielectric constant (ε), the dielectric loss (tan δ), the temperature change rate of the electrostatic capacitance, the dielectric loss (tan δ) when an AC voltage was applied, the specific resistance and the dielectric breakdown voltage were obtained.

In this case, the dielectric constant and the dielectric loss are 2
The measurement was performed under the conditions of 5 ° C., 1 kHz, and 1 Vrms. The rate of change in capacitance with temperature is the rate of change in capacitance at −25 ° C. and 85 ° C. (Δ) with reference to the capacitance at 20 ° C.
C / C ₂₀ ) was determined. Furthermore, the dielectric loss when applying an AC voltage is 100 V / mm, 1 kHz at a temperature of 25 ° C.
The AC voltage was applied to measure the dielectric loss. The specific resistance was determined by applying a DC voltage of 100 V for 2 minutes at 25 ° C. and 125 ° C. and measuring the insulation resistance. Then, as the dielectric breakdown voltage, an AC voltage and a DC voltage were separately applied at a boosting rate of 100 V / sec, and the breakdown voltages at the AC voltage and the DC voltage were measured. The results of these measurements are shown in Table 3.

Example 2 First, in the same manner as in Example 1, four kinds of BaTiO ₃ having different purities shown in A, B, C and D of Table 1 were prepared.

Next, as a low temperature sintering agent, the composition is 8BaO.
_{-6SrO-6CaO-30Li 2 O-} 50SiO
An oxide glass represented by ₂ (mol%) was prepared. That is, as a starting material, industrial raw materials such as BaCO ₃ and S
rCO ₃ , CaCO ₃ , Li ₂ O and SiO ₂ were prepared. Next, these starting materials were weighed so as to have the composition of the above oxide glass, wet mixed and pulverized by a ball mill for 16 hours, and then evaporated and dried to obtain a mixed powder. Then, the obtained mixed powder was put in an alumina crucible and left at a temperature of 1300 ° C. for 1 hour, and then rapidly cooled to vitrify. Then, this glass was crushed so as to pass through a 200-mesh sieve to obtain glass powder.

Next, the previously prepared BaTiO ₃ was added to 83.
Against 3 to 96.7 mol%, such that the composition ratio shown in Table _{4, La 2 O 3, CeO} 2, Pr 6 O 11, Nd 2 O
₃ , Sm ₂ O ₃ , CaZrO ₃ , and TiO ₂ were weighed as main components, and the previously prepared glass was also weighed and added to the main components so that the composition shown in Table 4 was obtained. After that, a molded body was obtained in the same manner as in Example 1 and fired at the temperature shown in Table 5 to obtain a disk-shaped porcelain.

Then, the surface of this porcelain was observed at 2000 times with an electron microscope to measure the grain size.

Next, silver electrodes were baked on both sides of the obtained porcelain to obtain a measurement sample (capacitor). Then, as in Example 1, the dielectric constant (ε), the dielectric loss (tan δ), the temperature change rate of the capacitance, and the dielectric loss (ta) when an AC voltage is applied.
nδ), specific resistance and dielectric breakdown voltage were determined. The results of these measurements are shown in Table 5.

Next, the reason why the composition range of the dielectric porcelain composition of the present invention is limited will be described based on the results of Examples 1 and 2 described above.

Sample Nos. 1-1, 1-2, 2-1 and 2-
As shown in FIG. 2, the contents of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide and samarium oxide are LaO _3/2 , CeO ₂ , PrO _11/6 ,
If it is less than 1.4 mol% in terms of NdO _3/2 and SmO _3/2 , the dielectric constant becomes low and the grain size becomes 4 μm or more, which is not preferable. On the other hand, sample numbers 1-12, 1
As shown in -13, 2-17, and 2-18, when the content of these exceeds 5.0 mol%, the dielectric constant is also low and the sintering temperature is high, which is not preferable.

As shown in sample numbers 1-14 and 2-19, when the content of CaZrO ₃ is less than 0.5 mol%,
The rate of change in capacitance exceeds -55%, which is not preferable. On the other hand, as shown in Sample Nos. 1-15 and 2-20, when the content of CaZrO ₃ exceeds 6.7 mol%, the dielectric constant is significantly lowered, which is not preferable.

As shown in Sample Nos. 1-16, 1-17, 2-21 and 2-22, when BaTiO ₃ raw material C or D containing a large amount of alkali metal oxide was used, the dielectric constant was significantly increased. It becomes low, which is not preferable.

As shown in Sample Nos. 1-18 and 2-23, when the content of TiO ₂ is less than 1.4 mol%, the sintering temperature becomes high, which is not preferable. On the other hand, sample number 1-19
And 2-24, the content of TiO ₂ is 5.0.
If it exceeds mol%, the specific resistance at 25 ° C. and 125 ° C.,
That is, the insulation resistance becomes small, which is not preferable.

When the glass content is less than 0.3 parts by weight, the sintering temperature is 1 as shown in sample No. 2-15.
When it exceeds 300 ° C, the effect of lowering the sintering temperature is hardly obtained. On the other hand, as shown in Sample No. 2-16, when the glass content exceeds 2.5 parts by weight, the dielectric constant is lowered, which is not preferable.

On the other hand, in the samples (Sample Nos. 1-3 to 1-11 and Sample Nos. 2-3 to 2-14) using the dielectric ceramic composition within the scope of the present invention, The grain size of the sintered body is as small as 1.0 to 3.0 μm. Further, the rate of change in capacitance at −25 ° C. and 85 ° C. based on 20 ° C. is within −55%, which satisfies the E characteristics of JIS standard.

Further, in the case of the composition in which glass as the low temperature sintering agent is not added, the dielectric constant is as high as 9300 or more, and even in the case of the composition in which the glass component is added, the dielectric constant is as high as 8900 or more. And in each case, the dielectric loss when an AC voltage of 100 V / mm is applied is as small as 3.0% or less. Further, the specific resistance at 25 ° C. is 10 ¹³ Ω · cm or more, 1
The specific resistance at 25 ° C. is as large as 10 ¹⁰ Ω · cm or more. Furthermore, the dielectric breakdown voltage is 12 to 13 kV / mm in AC voltage,
The DC voltage shows a large value of 14 to 15 kV / mm.

Example 3 A multilayer ceramic capacitor using the dielectric ceramic composition of the present invention was produced. First, a polyvinyl butyral binder and an organic solvent such as toluene or ethyl alcohol were added to the raw materials weighed so as to have the composition of Sample No. 1-11, and the mixture was mixed with a ball mill to obtain 16
The mixture was mixed for a time to form a slurry, and a 22 μm ceramic green sheet was prepared by the doctor blade method. A palladium paste for internal electrodes was printed on this ceramic green sheet by a screen printing method. Then, a plurality of ceramic green sheets were laminated so that the printed palladium pastes face each other, and thermocompression bonded to obtain a laminated body.

Next, the laminate was fired at a temperature of 1300 ° C. for 2 hours to obtain a sintered body. Then, silver paste was applied to both end faces of the sintered body and baked at 800 ° C. in air to form an external electrode electrically connected to the internal electrode. Thus, as shown in sample number 3-1 of Table 6, the outer dimensions are 1.6 mm in width × 3.2 mm in length × 1.2 mm in thickness, the thickness of the dielectric ceramic layer between the internal electrodes is 13 μm, and the effective dielectric A total of 19 body ceramic layers and a counter electrode area per layer of 2.0 mm ² were obtained as a monolithic ceramic capacitor.

Next, using the raw materials weighed so as to have the composition of Sample No. 2-11, and under the conditions of the firing temperature of 1270 ° C., otherwise in the same manner as in Sample No. 3-1, the sample No. of Table 6 was obtained. A multilayer ceramic capacitor shown in 3-2 was produced.

After that, the capacitance and the dielectric loss (tan) of the two types of monolithic ceramic capacitors obtained above are
δ), insulation resistance (IR), rate of change in capacitance with temperature, and breakdown voltage were determined.

In this case, the dielectric constant and the dielectric loss are 25
The measurement was performed under the conditions of ° C, 1 kHz, and 1 Vrms. Also,
The insulation resistance was measured at 25 ° C. by applying a DC voltage of 25 V for 2 minutes. Furthermore, the temperature change rate of capacitance is
The rate of change in capacitance (ΔC / C ₂₀ ) at −25 ° C. and 85 ° C. based on the capacitance at 20 ° C. was determined. And
As the dielectric breakdown voltage, an AC voltage and a DC voltage were separately applied at a boosting rate of 100 V / sec, and the breakdown voltages at the AC voltage and the DC voltage were measured.

As a comparative example, BaTiO ₃ of 78.
Based on 5 mol%, BaZrO ₃ 14.5 mol% and C
7.0 mol% of aZrO ₃ was added, and a laminated ceramic capacitor was produced by the same method as described above. And
Each characteristic was measured similarly for this comparative example.

The surface of each monolithic ceramic capacitor was observed with an electron microscope at a magnification of 2000 to measure the grain size. The above results are shown in Table 6.

As shown in Table 6, the monolithic ceramic capacitor made of the porcelain composition of the present invention has a smaller grain size and a smaller dielectric loss than the comparative example. Further, the monolithic ceramic capacitor of the present invention has
It has a double breakdown voltage. That is, it is shown that a laminated ceramic capacitor having good characteristics can be obtained by using the porcelain composition of the present invention as a dielectric ceramic layer.

Further, in the above embodiment, 8BaO-6SrO-6CaO-3 was added to the glass as the low temperature sintering agent.
Although glass represented by 0Li ₂ O-50SiO ₂ (mol%) is used, BaO—SrO— having a composition ratio other than that is used.
CaO-Li ₂ O-SiO ₂ based glass or other S,
The same characteristics can be obtained by using glass or the like containing iO ₂ as a main component.

Even if MnCO ₃ is added as a reducing agent to the starting material of the dielectric ceramic composition shown in the above-mentioned embodiment in an amount not exceeding 0.48 parts by weight with respect to 100 parts by weight of the main component. , The characteristics of the obtained dielectric ceramic are not impaired. The amount of the reduction inhibitor MnCO ₃ added is 0.48.
When it exceeds the weight part, the specific resistance becomes small and the grain size becomes large, which is not preferable. In addition, a small amount of Fe ₂ O ₃ , Co ₃ O ₄ , and NiO are used as reducing agents.
Like MnCO ₃ , the addition of the above does not impair the characteristics of the obtained dielectric ceramic.

[0043]

As is apparent from the above description, according to the present invention, the grain size is small, the dielectric constant is high, the temperature and voltage dependence of the dielectric constant is small, and the dielectric breakdown is achieved. It is possible to obtain a dielectric ceramic composition having a high voltage.

Further, BaO--SrO is added to the above dielectric composition.
The sintering temperature can be lowered by adding glass containing —CaO—Li ₂ O—SiO ₂ as a main component.

By using the above-mentioned dielectric composition as the dielectric ceramic layer, it has a high dielectric constant even though the grain size is small, the temperature and voltage dependence of the dielectric constant is small, and the dielectric breakdown is caused. A monolithic ceramic capacitor having a high voltage can be obtained.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

[0051]

[Table 6]

Front page continued (72) Inventor Shigeki Nishiyama 2-10-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd.

Claims (4)

[Claims] 1. BaTiO ₃ having an alkali metal oxide content as an impurity of 0.03% by weight or less is 83.3 to.
With respect to 96.7 mol%, at least one selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide and samarium oxide is added to LaO _3/2 , CeO ₂ , Pr.
_1.4- converted to O _11/6 , NdO _3/2 and SmO _3/2
5.0 mol%, CaZrO ₃ 0.5 to 6.7 mol%,
And TiO ₂ in an amount of 1.4 to 5.0 mol%, a dielectric ceramic composition. 2. BaTiO ₃ having an alkali metal oxide content as an impurity of 0.03% by weight or less is 83.3 to.
With respect to 96.7 mol%, at least one selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide and samarium oxide is added to LaO _3/2 , CeO ₂ , Pr.
_1.4- converted to O _11/6 , NdO _3/2 and SmO _3/2
5.0 mol%, CaZrO ₃ 0.5 to 6.7 mol%,
And 100 parts by weight of the main component containing 1.4 to 5.0 mol% of TiO ₂ and 0.3 to 0.3% of a sub-component made of glass containing BaO—SrO—CaO—Li ₂ O—SiO ₂ as the main component. A dielectric ceramic composition containing 2.5 parts by weight. 3. A plurality of dielectric ceramic layers, a plurality of internal electrodes arranged via the dielectric ceramic layers,
A multilayer ceramic capacitor comprising an external electrode connected to the internal electrode, wherein the dielectric ceramic layer has a BaTiO ₃ content of 0.03 wt% or less of an alkali metal oxide as an impurity.
To 83.3-96.7 mol%, at least one selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide and samarium oxide is added to LaO _3/2 , CeO ₂ , Pr.
_1.4- converted to O _11/6 , NdO _3/2 and SmO _3/2
5.0 mol%, CaZrO ₃ 0.5 to 6.7 mol%,
And a dielectric material containing 1.4 to 5.0 mol% of TiO ₂ , and the internal electrodes are composed of palladium as a main component. 4. A plurality of dielectric ceramic layers, a plurality of internal electrodes arranged via the dielectric ceramic layers,
A multilayer ceramic capacitor comprising an external electrode connected to the internal electrode, wherein the dielectric ceramic layer has a BaTiO ₃ content of 0.03 wt% or less of an alkali metal oxide as an impurity.
To 83.3-96.7 mol%, at least one selected from lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide and samarium oxide is added to LaO _3/2 , CeO ₂ , Pr.
_1.4- converted to O _11/6 , NdO _3/2 and SmO _3/2
5.0 mol%, CaZrO ₃ 0.5 to 6.7 mol%,
And 100 parts by weight of the main component containing 1.4 to 5.0 mol% of TiO ₂ and 0.3 to 0.3% of a sub-component made of glass containing BaO—SrO—CaO—Li ₂ O—SiO ₂ as the main component. A monolithic ceramic capacitor, characterized in that it is made of a dielectric material of 2.5 parts by weight, and the internal electrodes are made of palladium as a main component.