JP2902926B2 - Dielectric porcelain composition - Google Patents

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, for example, a dielectric ceramic composition used for a ceramic capacitor for temperature compensation.

[0002]

2. Description of the Related Art Conventionally, ceramic capacitors for temperature compensation have been widely used in various electric devices for tuning, resonance, etc., and there has been a demand for a capacitor having a small size, a small dielectric loss, and a stable dielectric characteristic. .

For this reason, the conditions of the dielectric porcelain include a large relative dielectric constant, a small dielectric loss (in other words, a large Q value), and a change in the relative dielectric constant with respect to temperature in response to a demand for miniaturization. It is mainly small, and it is chemically stable for reliability.
High mechanical strength, high strength against thermal shock and the like can be mentioned.

Conventionally, as this type of dielectric porcelain, a BaO-RE having a relative dielectric constant as high as about 55 to 95 and a temperature coefficient of capacitance TCC of about 0 ± 200 ppm / ° C.
_{A 2} O ₃ —TiO ₂ (where RE ₂ O ₃ is a rare earth oxide, the same applies hereinafter) -based material has been known (Japanese Patent Publication No. Sho 50-2).
No. 0280).

[0005]

However, recent dielectric porcelains used in mobile communication equipment, for example, have a high relative dielectric constant and a high Q value for higher frequency and smaller size. not only stable with temperature characteristic, now that such a temperature coefficient TCC of the capacitance is within 0 ± 30 ppm / ° C. are required, the BaO-RE ₂
The O ₃ —TiO ₂ based material has a drawback that if the temperature coefficient TCC of the capacitance is controlled within the above range while maintaining a high relative dielectric constant, the sinterability of the porcelain becomes unstable. Conventionally, in order to stabilize sinterability, for example, S
Addition of an auxiliary agent such as iO ₂ has been performed. However, the addition of the auxiliary agent may cause a decrease in relative dielectric constant and a deterioration in temperature characteristics, and may deteriorate a Q value in a high frequency region. However, there is a problem that the dielectric properties may be impaired.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has been developed in view of the above-mentioned drawbacks.
r is as high as 50 or more, Q value is as high as 3000 or more, temperature characteristics are stable, and temperature coefficient of capacitance TCC is 0 ± 30 pp.
It is an object of the present invention to provide a dielectric ceramic composition as small as m / ° C. or less.

[0007]

[Means for Solving the Problems] The present inventors have proposed Ba-N
As a result of examining the d- (Ti + Me) system,
Satisfaction of various characteristics by shifting the temperature coefficient TCC of the large capacitance to the minus side to the plus side while maintaining a high dielectric constant by blending one or more of Zr and Sn with the -Nd-Ti system. I found that I can do that.

Further, it has been found that when the amount of Na is reduced by means such as using a raw material having a small amount of Na, stable sinterability is exhibited without adding an auxiliary agent such as SiO _{2 and the} like, and the present invention has been achieved. .

That is, a TiO ₂ raw material (a TiO ₂ raw material prepared by a sulfuric acid method, which is widely used in industry) contains about 0.05% by weight of Na. When creating a sheet,
Since the sodium carboxylate dispersant used to disperse the raw material powder in the slurry contains about 5.00% by weight of Na, the total amount in the dielectric porcelain is 0.20% by weight. % Of Na is mixed in, but it has been found that when the amount of Na is more than 0.1% by weight, the sinterability deteriorates.

The dielectric porcelain composition of the present invention is a composite oxide obtained by adding Mn to a main component comprising at least one of Ba, Nd, Ti and Zr or Sn as a metal element. the main component molar ratio according to the composition formula xBaO · yNd ₂ O ₃ · z of the metal element [(1-
c) TiO ₂ + cMeO ₂ ] (where x + y + z = 10
0, 0.01 ≦ c ≦ 0.10, and Me is at least one element of Zr or Sn).
Is in a range surrounded by the following A, B, C, D, and E, and the Mn is 0.01% with respect to the main component in terms of MnCO _3.
0.5% by weight, Na as an impurity component is 0.10% by weight or less in the total amount, and the relative dielectric constant at a measurement frequency of 1 MHz is 50 or more,
It has a temperature coefficient of capacitance Tcc of 0 ± 30 ppm / ° C.

Xyz A 15.50 17.50 67.00 B 10.50 22.50 67.00 C 7.50 22.50 70.00 D 9.17 19.17 71.66 E 12.50 17.50 70.00 Further, it is desirable that the content of Si as an impurity component is 0.05% by weight or less in the total amount in terms of SiO ₂ .

In the dielectric ceramic composition of the present invention, the content of Na as an impurity component is set to 0.10% by weight or less in the total amount because the sinterability deteriorates when Na is more than 0.10% by weight in the total amount. This causes deterioration of various dielectric constant characteristics such as relative dielectric constant, Q value, temperature coefficient of capacitance, etc., and it is more preferable that Na is 0.05% by weight or less in the total amount.

In order to reduce the amount of Na, the raw material B
aO (or BaCO ₃ ), Nd ₂ O ₃ , TiO ₂ , Z
Use high purity rO ₂ and SnO ₂ powder,
Use low soda raw materials or repeatedly calcine
It is possible to apply a chemical such as a dispersant or an organic binder (binder) used at the time of pulverization or molding, which has a low Na content, or the like.

Next, the composition formula based on the molar ratio is expressed as xBaO ·
yNd ₂ O ₃ .z [(1-c) TiO ₂ + cMeO ₂ ]
(However, x + y + z = 100, 0.01 ≦ c <0.1
0 and Me are at least one element of Zr or Sn)
When the BaO amount x is limited to 7.50 ≦ x ≦ 15.50, when x is smaller than 7.50, the relative dielectric constant becomes smaller than 50, and x is larger than 15.50. If so, the temperature coefficient TCC deteriorates. The relative permittivity tends to increase as the amount of BaO increases.

The amount y of Nd ₂ O _{3 is} defined as 17.50 ≦ y ≦
The reason for setting 22.50 is that when y is smaller than 17.50 or larger than 22.50, the temperature coefficient TCC
Is worse.

Further, [(1-c) TiO ₂ + cMe
O ₂ ] The amount z was set to 67.00 ≦ z ≦ 71.66 because
When z is smaller than 67.00, the sinterability and the temperature coefficient TCC deteriorate, and when z is larger than 71.66, the temperature coefficient TCC deteriorates.

Further, the ratio c of MeO ₂ to the total molar amount of TiO ₂ and MeO ₂ is, 0.01 ≦ c ≦ 0.10
It is desirable that This is because when c is smaller than 0.01, the temperature coefficient of capacitance TCC, which is an effect of the addition of ZrO ₂ , hardly moves to the positive side, and when c is larger than 0.10. Because it will be great.

The composition formula based on the molar ratio is represented by xBaO
・ YNd ₂ O ₃ .z [(1-c) TiO ₂ + cMe
O ₂ ] (however, x + y + z = 100, 0.01 ≦ c ≦
0.10, and Me is at least one element of Zr or Sn), and if it is within the range surrounded by the following a, b, c, d, and e, the temperature coefficient of capacitance TCC is 0
It is more preferable that the temperature is within ± 30 ppm / ° C. (COG characteristics) and the relative dielectric constant is as high as 60 or more.

Xyz a 15.50 17.50 67.00 b 10.50 22.50 67.00 c 10.00 22.50 70.00 d 10.00 20.00 70.00 e 15.00 17.50 67.50 Further, manganese is converted to 0.01 to 0.50 in terms of MnCO _3.
The reason for the content by weight is that when the content is less than 0.01% by weight or more than 0.50% by weight, the Q value decreases.

The Si content is 0.02 in terms of SiO _2.
When the content is more than 5% by weight, the Q value decreases. Therefore, the content is preferably 0.05% by weight or less of the total amount, and more preferably 0.0% by weight.
It is particularly preferred that the content be 3% by weight or less.

The dielectric ceramic composition of the present invention is prepared, for example, as follows. First, Ba of 99% or more purity
CO ₃ (BaO), TiO ₂ , ZrO ₂ and MnCO ₃
And Nd ₂ O ₃ powder having a purity of 95% or more (Pr or the like may be mixed as an impurity of the rare earth oxide), and the content of Na in the composition and the SiO of Si are used.
BaC so that the content in ₂ conversion falls within the range of the present invention.
O ₃ (BaO), TiO ₂ , Nd ₂ O ₃ , ZrO _2, and MnCO ₃ powders were prepared, weighed so that the composition of the sintered body would be as shown in Tables 1 and 2 described below, and mixed, and the mixture was dried. Then, it is calcined at 1000 to 1200 ° C for 1 to 3 hours.

After the calcined powder is pulverized with a ball mill, an organic binder having a low Na content (binder) is obtained.
After adding and stirring, for example, green sheets are formed by a doctor blade method, these green sheets are laminated, and after debinding treatment, 1280 to 1340
The dielectric ceramic composition of the present invention is obtained by firing in air at a temperature of 1 to 3 hours.

[0023]

According to the dielectric porcelain composition of the present invention, it is possible to improve the temperature coefficient of capacitance, obtain a high relative dielectric constant and a high Q value, and further improve the Ba-Nd-Ti system. T
By substituting a part of i with one or more of Zr or Sn, the relative permittivity of the Ba-Nd-Ti system is large, but the temperature coefficient TCC of the capacitance is large on the negative side.
Can be shifted to the plus side to expand the usable composition.

Further, Na as an impurity is contained in the total amount of 0.1%.
When the content is 0% by weight or less, the sinterability can be improved, and the relative dielectric constant, the Q value, and the temperature coefficient TCC can be improved.

In addition, manganese is converted to MnCO ₃ by 0.0
A high Q value can be obtained by containing 1 to 0.5% by weight.

Further, Si is contained in a total amount of 0.1% in terms of SiO ₂ .
By setting the content to 05% by weight or less, the Q value can be further improved.

[0027]

EXAMPLE As a starting material, BaCO having a purity of 99% or more was used.
₃ , each powder of TiO ₂ , ZrO ₂ , SnO _2, MnCO ₃ and Nd ₂ O ₃ having a purity of 95% or more (Pr etc. may be mixed as impurities of rare earth oxide) is used, and the amount of impurities in the raw material is used. Was adjusted to control the contents of Na and Si in the composition, and after weighing them so as to be as shown in Tables 1, 2 and 3, pure water was added, and ball milling was performed day and night using a resin ball. Was.

Next, after drying this mixture,
After calcining for 2 hours with a ball mill, the calcined powder was pulverized with a ball mill for 20 hours, an organic binder was added thereto, mixed and stirred, and formed into a green sheet having a thickness of 50 μm by a doctor blade method.

The green sheets thus obtained were stacked on each other and hot-pressed to form a green molded plate having a diameter of 20 m.
After punching into a disc having a thickness of about 1 mm and a thickness of about 1 mm, these compacts were subjected to a binder removal treatment at 300 ° C. for 2 hours, and subsequently fired at a temperature of 1280 to 1340 ° C. for 2 hours in air.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

Silver electrodes are formed on the entire upper and lower surfaces of the disk-shaped porcelain thus obtained to form a single-layer disk-shaped capacitor.
This was used as an evaluation sample.

Next, each sample for evaluation was subjected to a frequency of 1 MHz.
z, the capacitance (C) and the quality factor (Q value) were measured at an input power level of 1 Vrms, and at a frequency of 1 MHz,
Temperature coefficient of capacitance TCC in the range of 55 ° C to 125 ° C
Was measured.

The diameter (D) and thickness (T) dimensions of the sample were measured with an accuracy of ± 5 μm, and the weight (m) was measured with an accuracy of ± 5 mg, and the relative permittivity εr was calculated. The above results are shown in Tables 4, 5 and 6.

Further, as a result of quantitative analysis of the sintered body by means of atomic absorption, ICP, etc., it was confirmed that the composition of Ba, Nd, Ti, Zr, Sn, etc. was basically the same as the prepared composition.

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

[Table 6]

As is clear from Tables 4, 5 and 6, the temperature coefficient TCC of the capacitance is large on the minus side in the region α in FIG. 1, and the TCC is large on the plus side in the region γ. Therefore, in the region of β, the characteristics are not satisfied because the relative dielectric constant is low. Further, it can be seen that the sinterability deteriorates in the region of δ, and it is difficult to obtain a dense porcelain.

On the other hand, when Mn is less than 0.01% by weight or more than 0.5% by weight in terms of MnCO ₃ , it can be seen that the Q value decreases and the dielectric properties deteriorate.

Further, it can be seen that the sinterability deteriorates due to the incorporation of Na, and the relative dielectric constant and Q value decrease, and the temperature coefficient TCC also worsens.

It can also be seen that the relative dielectric constant decreases as the amount of Si increases, the absolute value of the temperature coefficient of capacitance TCC increases, and the Q value decreases.

On the other hand, the dielectric ceramic composition of the present invention has excellent characteristics such as a relative dielectric constant of 50 or more, a Q value of 3000 or more, and a temperature coefficient TCC of 0 ± 30 ppm / ° C. or less. In addition, it can be seen that by preventing the incorporation of Si, a ceramic having a high relative dielectric constant with a stable temperature coefficient can be manufactured.

[0045]

As described above, the dielectric ceramic composition of the present invention can be used without using a sintering aid such as SiO _2.
It can be fired at 40 ° C or lower, has a small capacitance temperature change, and has a high relative dielectric constant and a high Q value. Therefore, it is suitable for a dielectric ceramic composition for a temperature compensating ceramic capacitor having Pd as an internal electrode. Can be used.

[Brief description of the drawings]

FIG. 1 shows the composition range of the present invention, BaO—Nd ₂ O ₃ −.
FIG. 3 is a ternary diagram of a (TiO ₂ + MeO ₂ ) system.

Continuation of the front page (56) References JP-A-2-49307 (JP, A) JP-A-2-106810 (JP, A) JP-A-62-243207 (JP, A) JP-A-4-334809 (JP) , A) JP-A-7-192531 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/42-35/49 C04B 35/00-35/22 H01B 3/00 -3/14

Claims (2)

(57) [Claims] 1. At least Ba, Nd, T
A composite oxide obtained by adding Mn to a main component consisting of i and one or more of Zr and Sn, wherein the main component is represented by a composition formula of xBaO · y based on a molar ratio of a metal element.
Nd ₂ O ₃ .z [(1-c) TiO ₂ + cMeO ₂ ]
(Where x + y + z = 100, 0 <c, and Me is at least one element of Zr or Sn), the x, y, and z are surrounded by the following A, B, C, D, and E. Mn is present in a range of 0.01 to 0.5% by weight based on the main component in terms of MnCO ₃ , and
Na as an impurity component is 0.10% by weight or less in the total amount, and the relative dielectric constant at a measurement frequency of 1 MHz is 5%.
0 or more, the temperature coefficient of capacitance Tcc of 0 ± 30 ppm /
A dielectric porcelain composition characterized in that the temperature is ℃. xyz A 15.50 17.50 67.00 B 10.50 22.50 67.00 C 7.50 22.50 70.00 D 9.17 19.17 71.66 E 12.50 17.50 70.00 2. The dielectric ceramic composition according to claim 1, wherein the content of Si as an impurity component is 0.05% by weight or less in the total amount in terms of SiO ₂ .