JP3071449B2 - Dielectric porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dielectric porcelain composition obtained by adding barium titanate BaTiO ₃ as a main component and adding a lanthanum compound, zinc oxide, and niobium oxide. is there.

[Conventional technology]

The dielectric ceramic composition is used as a material for a multilayer ceramic capacitor or the like. Multilayer ceramic capacitors are
A plurality of green sheets of the dielectric porcelain composition on which the opposing internal electrodes are formed are laminated so as to have a predetermined capacity, and then integrally fired.

For example, a dielectric ceramic composition used for a multilayer ceramic capacitor of X7R (EIA standard: temperature characteristic is within ± 15% at −55 ° C. to 125 ° C.) has a relative dielectric constant of 25% at + 25 ° C.
00 or more, and the thickness of the raw sheet per sheet is 15μ
m or less, and it is important that the firing temperature is, for example, 1300 ° C. or less. That is, the relative dielectric constant at 25 ° C.
By setting the thickness of the raw sheet to 2,500 or more and the thickness of the raw sheet to 15 μm or less, it is possible to minimize the thickness and the facing area of the dielectric ceramic composition raw sheet between the opposed internal electrodes, and achieve miniaturization of the multilayer ceramic capacitor it can.

Further, by setting the firing temperature to 1300 ° C. or lower, the selection range of the material of the opposed internal electrode is increased, and for example, it is possible to use an inexpensive Pd-Ag from an expensive Pd 100% material.

Although not described above, the dielectric loss tan δ (2.5% or less) and the insulation resistance, which are various characteristics of the dielectric ceramic composition, must be sufficiently considered.

Hitherto, a dielectric porcelain composition containing barium titanate, niobium oxide, and zinc oxide has already been proposed (Japanese Patent Application Laid-Open No.
-18162, JP-A-59-18159).

According to this dielectric ceramic composition, the relative dielectric constant is 2000 to 30.
00 can be set.

[Problems to be solved by the invention]

However, even though the above-mentioned dielectric porcelain composition can obtain a high relative dielectric constant, the dielectric loss tanδ is large, so that the raw sheet cannot be thinned. The effect of obtaining a dielectric constant was not sufficiently exhibited.

The present invention has been devised in view of the above-described problems.Specifically, in X7R, the relative dielectric constant at 25 ° C. is high, and the firing temperature is relatively low, and further, the dielectric loss is excellent, An object of the present invention is to provide a dielectric ceramic composition in which one green sheet can be made thin.

[Means for solving the problem]

Specific measures taken to achieve the above objectives are:
Barium titanate, lanthanum compounds, zinc oxide comprises niobium oxide, relative to 100 parts by weight of barium titanate, 0.2 to 1.0 wt% lanthanum compound in La ₂ O ₃ in terms of zinc oxide (ZnO) is 0.3 to 1.2 weight %, Niobium oxide (Nb ₂ O ₅ ) is 1.0
This is a dielectric porcelain composition containing about 2.5% by weight.

[Action]

As described above, according to the present invention, barium titanate, a lanthanum compound, zinc oxide, niobium oxide is contained, and based on 100 parts by weight of barium titanate, the lanthanum compound is 0.2 to 1.0% by weight in terms of La ₂ O ₃ , is 0.3-1.2% by weight of zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅₎ is set in the dielectric ceramic composition comprising 1.0 to 2.5 wt%. As a result, the relative dielectric constant ε at 25 ° C. becomes 2500 or more, the firing temperature is relatively low, the dielectric loss is excellent, and a small-sized and large-capacity multilayer ceramic capacitor can be obtained.

If the lanthanum compound is less than 0.2 in La ₂ O ₃ conversion, the relative dielectric constant
It has dropped significantly to 2000 or less. If it exceeds 1.0% by weight, the dielectric loss tan δ exceeds 3.0%, and the temperature characteristics become large.

If the zinc oxide (ZnO) is less than 0.3, the relative dielectric constant is 2300
Below, the insulation resistance is greatly reduced. Also 1.
If it exceeds 2% by weight, the insulation resistance is reduced and the temperature characteristics are greatly deteriorated.

Further, when the niobium oxide (Nb ₂ O ₅ ) is less than 1.0, the dielectric loss tan δ is greatly deteriorated, and the temperature characteristics are further deteriorated.
If it exceeds 2.5% by weight, the relative dielectric constant decreases.

In the method of producing barium titanate, a satisfactory dielectric loss tan δ cannot be obtained by the solid phase method or the oxalic acid method.

Due to these interactions, the temperature characteristic is -55 ° C to 125 ° C
Within ± 15%, the relative dielectric constant at + 25 ° C. is 2500 or more within ± 15%, and the dielectric loss tan δ can be as low as 2.5% or less even when the thickness of the green sheet is 15 μm. For this reason, a small-sized and large-capacity multilayer capacitor can be achieved.

In addition, the sintering temperature is 1300 ° C or less, and it is easy to manufacture industrially, and inexpensive silver-palladium (Ag
-Pd: Ag / Pd = 20/80 to 40/60) is achieved, and a dielectric ceramic composition which can be used for a multilayer ceramic capacitor or the like is achieved.

Furthermore, the dielectric loss tan δ, which is a basic characteristic of a dielectric ceramic composition, is 2.5% or less, and the insulation resistance (IR) is 1 × 10 ⁴ MΩ.
Thus, a dielectric ceramic composition sufficiently satisfactory is achieved.

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail.

Based on barium titanate produced by hydrothermal synthesis as a main component, with respect to 100 parts by weight of this barium titanate,
La ₂ O ₃ , zinc oxide (ZnO), and niobium oxide (Nb ₂ O ₅ ) powders were weighed as shown in Table 1 as a lanthanum compound, wet-ground with a ball mill for 20 hours, and then an organic binder. Is added, and then stirred, the thickness is 15 μm by a doctor blade method.
Into a tape shape. This tape is cut into 130 mm x 100 mm, 10 sheets are stacked, and a laminate is prepared by hot pressing at 80 ° C.

Ag-based paste (Ag / Pd = 30/70) as internal electrode
Was printed.

This laminate was cut into 2.0 mm x 1.25 mm, and 125
It was baked at 0-1300 ° C. for 2 hours. Further, electrodes of silver paste were baked on both end surfaces at 800 ° C. for 10 minutes to obtain measurement samples.

For the sample thus formed, the capacitance and the dielectric loss tan δ were measured at a reference temperature of 25 ° C., a frequency of 1.0 kHz, and a measurement voltage of 1.0 Vrms. The temperature change rate of the capacitance is
It was measured in the range of -55 ° C to + 125 ° C, and the capacity at + 25 ° C was used as a reference. Further, the insulation resistance was measured when a DC voltage of 25 V was applied for 1 minute. The relative permittivity was calculated backward from the capacitance.

Table 1 shows the results. Samples marked with * are out of the scope of the present invention.

And as an evaluation of the scope of the present invention, the relative dielectric constant ε is 2500
The above was regarded as non-defective. That is, when the relative dielectric constant ε is less than 2500,
A sufficient relative permittivity cannot be obtained, which makes it difficult to reduce the size of the multilayer ceramic capacitor.

A dielectric loss tan δ of 2.5% or less was regarded as a good product. That is, if the dielectric loss tan δ exceeds 2.5%, the dielectric loss tan δ becomes defective in the multilayer ceramic capacitor, and it becomes difficult to reduce the thickness of the dielectric layer.

Furthermore, the temperature characteristic is -55 ° C to correspond to X7R.
A non-defective product was determined to have a temperature change rate of a capacity within ± 15% within a temperature range of up to + 125 ° C.

Further, the insulation resistance (IR) of 10 ⁴ MΩ or more was regarded as a good product.

Sample Nos. 1 to 9 are lanthanum compounds added to barium titanate BaTiO ₃ which is a main component of the dielectric ceramic composition.
The composition of La ₂ O ₃ was studied. That is, the added amount of La ₂ O ₃ is 0.1
The values were each varied to 1.1% by weight.

At this time, the addition amounts of zinc oxide (ZnO) and niobium oxide (Nb ₂ O ₅ ) were set to 0.6% by weight and 1.6% by weight.

In sample No. 1 (the amount of La ₂ O ₃ added: 0.1% by weight), the relative dielectric constant ε was as low as 1950, and the dielectric loss tan δ was 2.8%. Further, the temperature characteristic is deteriorated to + 21%.

In sample numbers 2 to 8 (addition amount of La ₂ O ₃ : 0.2 to 1.0% by weight), the relative dielectric constant ε was 2900 to 3300, and the dielectric loss ta
nδ is 2.43% or less and temperature characteristics are within ± 14%. The insulation resistance is also in the range of good products. That is, a composition having a high relative dielectric constant ε, excellent temperature characteristics, and a small dielectric loss tan δ is achieved.

Further, in sample No. 9 (the amount of La ₂ O ₃ added: 1.1% by weight), the relative dielectric constant ε was 3600, which is a good range, but the dielectric loss tan δ was 3.05%, and the temperature characteristics were deteriorated to −20%. Would.

Therefore, in the present invention, the weight of La ₂ O ₃ added to barium titanate BaTiO ₃ is in the range of 0.2 to 1.0% by weight based on 100 parts by weight of barium titanate BaTiO ₃ .

Sample Nos. 10 to 16 investigated the composition amount of zinc oxide (ZnO) added to barium titanate BaTiO ₃ which is a main component of the dielectric ceramic composition. That is, the added amount of ZnO is 0.2 to 1.3% by weight.
The values were changed up to each.

At this time, the added amounts of the lanthanum compound La ₂ O ₃ and niobium oxide (Nb ₂ O ₅ ) were set to 0.6% by weight and 1.6 to 2.1% by weight.

In sample No. 10 (the amount of ZnO added: 0.2% by weight), the relative dielectric constant ε was as low as 2300, and the dielectric loss tan δ and the insulation resistance were good, but no result was obtained.

In sample numbers 11 to 15 (the amount of ZnO added: 0.3 to 1.2% by weight), the relative dielectric constant ε is 2500 to 3300, the temperature characteristics are within ± 14%, the dielectric loss tan δ is 2.39% or less, and the insulation resistance is Is 1 × 10 ⁴ MΩ or more.

That is, a composition having a high relative dielectric constant ε, good temperature characteristics, and low-temperature firing is achieved.

Further, in Sample No. 16 (the amount of ZnO added: 1.3% by weight), although the relative dielectric constant ε was extremely high at 6000, the temperature characteristics,
The insulation resistance is greatly deteriorated.

Therefore, in the present invention, the weight of ZnO added to barium titanate BaTiO ₃ is in the range of 0.3 to 1.2% by weight based on 100 parts by weight of barium titanate BaTiO ₃ .

Next, Sample Nos. 17 to 25 examined the amount of niobium oxide (Nb ₂ O ₅ ) added to barium titanate BaTiO ₃ which is a main component of the dielectric ceramic composition. That is, the value of the additive amount of Nb ₂ O ₅ up to 0.9 to 2.6 wt% respectively varied.

At this time, the addition amounts of the lanthanum compound La ₂ O ₃ and zinc oxide (ZnO) were set to 0.6% by weight and 0.3 to 1.1% by weight.

In sample No. 17 (the amount of Nb ₂ O ₅ added was 0.9% by weight), the relative dielectric constant ε was 3900, but the temperature characteristic was −22%.
The dielectric loss tan δ is as large as 3.5%. This makes it difficult to reduce the thickness of the dielectric layer.

In sample numbers 18 to 24 (addition amount of Nb ₂ O ₅ : 1.0 to 2.5% by weight), the relative dielectric constant ε is 2500 to 3500, and the temperature characteristic is -14% to + 12%. Furthermore, the dielectric loss tanδ is 2.3
9% or less.

Further, in Sample No. 25 (the amount of Nb ₂ O ₅ added: 2.6% by weight), the dielectric loss tan δ was 1.78%, but the relative dielectric constant ε was ε.
Decreases to 2200.

Therefore, in the present invention, the weight of Nb ₂ O ₅ added to barium titanate BaTiO ₃ is in the range of 1.0 to 2.5% by weight based on 100 parts by weight of barium titanate BaTiO ₃ .

Finally, the amounts of La ₂ O ₃ , ZnO and Nb ₂ O ₅ added are all less than the range, ie 0.2, 0.2 and 0.9% by weight.
In the case of (Sample No. 26), the dielectric ceramic composition cannot be sintered.

Conversely, when the added amounts of La ₂ O ₃ , ZnO and Nb ₂ O ₅ all exceed the range, that is, 1.1, 1.3 and 2.6% by weight (Sample No. 27), the relative dielectric constant ε becomes 1900 and Loss tan
δ becomes 2.61%.

As described above, barium titanate produced by hydrothermal synthesis, lanthanum compounds, zinc oxide comprises niobium oxide, relative to 100 parts by weight of barium titanate, lanthanum compound in La ₂ O ₃ in terms of 0.2 to 1.0 Weight percent, zinc oxide (ZnO)
According to the dielectric porcelain composition containing 0.3 to 1.2% by weight and 1.0 to 2.5% by weight of niobium oxide (Nb ₂ O ₅ ), -55 ° C. to 12 ° C.
The temperature change rate of the capacity at 5 ° C is within ± 15%, and the X7R
Fully satisfies the characteristics, and the relative dielectric constant ε at 25 ° C.
Is 2500 or more, the firing temperature is relatively low at 1250 to 1300 ° C., the dielectric loss tan δ is 2.5% or less, and the green sheet of the dielectric ceramic can be made as thin as 15 μm or less. Therefore, a small-sized and large-capacity multilayer ceramic capacitor having excellent temperature characteristics can be realized. Further, since the firing temperature is relatively low at 1250 to 1300 ° C., an inexpensive internal electrode material containing 100 to 40% of expensive palladium to 20 to 40% of Ag can be used as an internal electrode material. A condenser can be achieved.

In addition to the hydrothermal synthesis method, there are a solid phase method, an oxalic acid method, and the like as a method for producing barium titanate. 2.8
About 5%). To obtain stable barium titanate, it is desirable to use barium titanate produced by a hydrothermal synthesis method.

〔The invention's effect〕

As described above, according to the present invention, barium titanate,
Contains lanthanum compound, zinc oxide, niobium oxide, and 100 parts by weight of barium titanate, the lanthanum compound is La ₂ O ₃
0.2-1.0 wt% in terms of 0.3 to 1.2 wt% of zinc oxide (ZnO) is, for niobium oxide (Nb ₂ O ₅₎ is comprising 1.0 to 2.5 wt%, satisfying the X7R characteristic, the dielectric constant ε Is 2500 or more, and the firing temperature is 1300 ° C. or less. As other characteristics, dielectric loss tanδ is 2.5% or less, insulation resistance (I
R) is 1 × 10 ⁴ MΩ or more.

Thus, for example, when a multilayer ceramic capacitor is formed of the above-described dielectric ceramic composition, a small-sized and large-capacity capacitor having excellent temperature characteristics can be achieved, and a firing temperature of 1300 ° C.
In the following, it is possible to use inexpensive silver-palladium as an internal electrode between the laminated sheets, and it becomes an inexpensive dielectric ceramic composition of a laminated ceramic capacitor.

Claims (1)

(57) [Claims] 1. A barium titanate, a lanthanum compound, zinc oxide and niobium oxide, wherein a lanthanum compound is 0.2 to 1.0% by weight in terms of La ₂ O _{3 with} respect to 100 parts by weight of barium titanate, and zinc oxide (ZnO) There 0.3-1.2 wt%, niobium oxide (Nb ₂ O ₅₎ dielectric ceramic composition comprising 1.0 to 2.5 wt%.