JPH07201225A - Dielectric porcelain composite - Google Patents

Abstract

PURPOSE:To provide a dielectric porcelain composite having excellent anti-fold resistance and dielectric strength, and reduced dependency of electrostatic capacity temperature characteristics on the baking temperature. CONSTITUTION:A composite is expressed by (SrxCayBaz)TiO3, where 55<=x<=0.85, 0.45<=y<=0.15. and 0<=z<=5.0 at a mole ratio of x+y+z=1. As additives, Bi2O3 by 0.5-8.0mol% and MgO by 0.5-2.0mol% are added.

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 temperature compensation, and more particularly to a dielectric ceramic composition used for disk capacitors and trimmer capacitors.

[0002]

2. Description of the Related Art A trimmer capacitor is a variable capacitor whose capacitance can be arbitrarily adjusted by changing the contact area between a dielectric element (stator) having an electrode on one surface and a metal rotor as its counter electrode. . However, since the contact area is changed by rotating the adjusting pin with a driver, a considerable stress is applied to the dielectric element (stator). Further, as a technological trend, the height of the trimmer capacitor will be further reduced in the future, and it will be required to make the dielectric element (stator) thinner.

[0003]

However, (Sr
There is a problem that the dielectric strength of the dielectric element (stator) is weak only with the composition of the CaBa) TiO ₃ and Bi ₂ O ₃ system, and the dielectric element (stator) cracks during the capacity adjustment when the thickness is reduced. Further, the dielectric breakdown voltage is also reduced by making the dielectric element thinner.

In addition to the thickness (Sr _x Ca _y Ba _z )
TiO ₃ and Bi ₂ O ₃ also have a problem that the firing temperature dependency of the capacitance temperature characteristic is remarkable.

The present invention eliminates the above-mentioned conventional drawbacks and provides a dielectric ceramic composition in which the bending strength is improved, the dielectric strength is improved, and the firing temperature dependence of the capacitance temperature characteristic is relaxed. With the goal.

[0006]

[Means for Solving the Problems] Solving these problems
Therefore, in the present invention, the general formula (Sr_xCa_yBa_z)
TiO₃And x, y and z represent molar ratios.
Then, when x + y + z = 1, the values of x, y, and z are 0.55 ≦ x ≦
0.85, 0.45 ≦ y ≦ 0.15, 0 ≦ z ≦ 0.5
Yes, Bi as an additive₂O₃Is 0.5-8.0 mol%
Furthermore, a dielectric material containing 0.5 to 2.0 mol% of MgO.
Porcelain composition, Bi as an additive₂O₃And Nb ₂O_FiveTo 0.0
Dielectric ceramic composition comprising 2 to 0.5 mol% and additive
Bi as an additive₂O₃And ZrO₂0.01-0.2mo
A dielectric ceramic composition comprising 1% is provided.

[0007]

In the general formula, (Sr _x Ca _y Ba _z ) TiO ₃ is represented, and x, y and z are molar ratios, and x + y + z
= 1 and the values of x, y, z are 0.55 ≦ x ≦ 0.85, 0.
45 ≦ y ≦ 0.15, 0 ≦ z ≦ 0.5, and the dielectric ceramic composition containing Bi ₂ O ₃ as an additive in an amount of 0.5 to 8.0 mol% further contains MgO in an amount of 0.5 to 2. By adding 0 mol%, the crystal grain size becomes uniform and small, and the bending strength is improved. In addition, the dielectric strength is 20 (kv / mm) to 30 (kv / mm) by adding Nb ₂ O _5.
Can be Then, by adding ZrO ₂ , the firing temperature dependence of the capacitance temperature characteristic can be relaxed.

[0008]

EXAMPLES Examples of the present invention will be described below.

The dielectric ceramic composition of the present invention is used for trimmer capacitors and the like. That is, as shown in FIG. 1, a metal rotor 4 having a semi-circular concave portion 3 formed on the lower surface thereof is mounted on a stator composed of a dielectric ceramic plate 2 having a semi-circular stator electrode 1 built-in inside near the surface. Then, the spring 6 is installed in the adjusting recess 5 formed on the upper surface of the metal rotor 4, and the cylindrical portion 7 at the center of the spring 6 is penetrated through the centers of the metal rotor 4 and the stator and caulked on the lower surface of the stator. It constitutes a trimmer capacitor.

The present invention provides a dielectric ceramic composition that constitutes the dielectric ceramic plate 2 as the stator of such a trimmer capacitor, which has excellent bending strength, excellent dielectric strength, and firing temperature dependence of capacitance. Is provided as a relaxation.

Specific examples of the dielectric ceramic composition of the present invention will be described below. (Example 1) SrTiO ₃ , CaTi as starting materials
O ₃ , BaTiO ₃ , Bi ₂ O ₃ and MgO were weighed so as to have the composition ratio shown in (Table 1), wet-mixed with partially stabilized zirconia balls, and dehydrated and dried. Next 11
It was calcined at 00 ° C. for 2 hours. This calcined powder was wet-ground under the same conditions as wet mixing, and dehydrated and dried. An organic binder was added to this pulverized powder to make it homogenous, and then the powder was sized through a 32 mesh sieve and molded with a molding pressure of 1 ton / cm ^{2 into} a diameter of 15 mm and a thickness of 0.4 mm using a die and a hydraulic press. Next, the molded disc is put into an alumina sheath covered with zirconia powder, and the temperature rising / falling rate is 400 in air.
° C / h, holding temperature 1300 to 1400 ° C, holding time 1 to
After firing for 4 hours, dielectric ceramic discs having composition ratios shown in sample numbers 1 to 30 of (Table 1) were obtained.

The thickness, diameter and weight of the thus obtained dielectric porcelain disc were measured, and the samples for measuring the dielectric constant, the goodness Q and the temperature coefficient of capacitance were both sides of the dielectric porcelain disc. A silver electrode was baked on the whole surface. Then, the dielectric constant, the goodness Q,
The temperature coefficient of capacitance is model 4 of the digital LCR meter.
275A (manufactured by Yokogawa Hewlett-Packard Co.) was used, and the measurement temperature was 20 ° C., the measurement voltage was 0.5 Vrms, and the measurement frequency was 1 MHz. The temperature coefficient of capacitance was obtained by measuring the capacitance at -25 ° C and 85 ° C and using the following formula.

TC = (C-Co) / Co × 1/110 ×
10 ⁶ TC: Capacitance temperature coefficient (ppm / ° C.) Co: Capacitance at -25 ° C. (pF) C: Capacitance at 85 ° C. (pF) Further, the dielectric constant was calculated by the following formula.

K = 143.8 × Co × t / (D / 2) ²
/ Π K: Dielectric constant Co: Capacitance at 20 ° C (pF) D: Diameter of dielectric ceramic disk (mm) t: Thickness of dielectric ceramic disk (mm) Further, bending strength is shown in Fig. 2. As shown, 3 according to JIS
The point bending strength was measured. The test piece 9 is placed on the two fulcrums 8, and the dial gauge 1 in which the load point has a constant radius of curvature
The load was applied to the test piece 9 by 0. The maximum load when the test piece 9 was broken was read and determined by the following formula.

Bending strength = 3 PL / (2 wt ² ) P: Maximum load when the test piece breaks (kgf / mm ² ) L: Distance between fulcrums (mm) w: Width of test piece (mm) t: Test piece (Mm) The above measurement results are shown in Table 1 for each of sample numbers 1 to 30.

[0016]

[Table 1]

As can be seen from (Table 1), when SrTiO ₃ is less than 0.55, Q decreases, and when it exceeds 0.80, the element body is reduced to become a semiconductor capacitor.
The capacity becomes large and the Q becomes extremely small. Further, the temperature characteristic on the minus side also becomes large.

When the added amount of BaTiO ₃ exceeds 0.08, the Q is lowered and the temperature characteristic on the negative side is increased, which is not practical.

Next, when Bi ₂ O ₃ is less than 0.1 mol%,
Dielectric constant and Q are low without sintering. On the other hand, if it exceeds 8.0 mol%, the sinterability will deteriorate and the Q will decrease. Further MgO
Is less than 0.5 mol%, no improvement in bending strength is observed,
When it exceeds 2.0 mol%, a decrease in Q is observed. MgO
It is considered that the reason for improving the bending strength is that the addition of MgO suppresses grain growth and forms homogeneous crystal grains.

In this example, the titanic acid compound was used as the starting material for Sr, Ca, and Ba, but there is no significant difference in characteristics even if the oxide or carbonate and titanium oxide are used. At that time, 1
If calcination is performed at 000 ° C to 1200 ° C, stable characteristics with little variation can be obtained.

(Example 2) Nb ₂ O ₅ was weighed so as to have the composition ratio shown in (Table 2), and a sample was prepared by the same manufacturing method as in (Example 1).

With respect to the dielectric constant, the goodness Q and the temperature characteristic of capacitance, the same method as in (Example 1) was used. For the dielectric breakdown strength, a high voltage power supply PHS35K-3 type (manufactured by Kikusui Electronics Co., Ltd.) was used, the sample was put in silicon oil, and the dielectric breakdown voltage obtained at a step-up speed of 50 V / sec was used as the dielectric thickness. It was divided by to obtain the dielectric breakdown strength per 1 mm.

The above measurement results are shown in (Table 2) for each of the sample numbers 31 to 35.

[0024]

[Table 2]

As can be seen from (Table 2), the dielectric strength of the sample without Nb ₂ O ₅ is 20 (kv / mm),
The sample to which b ₂ O ₅ is added has improved withstand voltage. However, if it exceeds 0.5 mol%, the capacitance-temperature characteristic becomes large on the negative side, which is not practical.

(Example 3) ZrO ₂ was weighed so as to have the composition ratio shown in (Table 3), and a sample was prepared by the same manufacturing method as in (Example 1). The electrical characteristics are the same as in the measuring method of (Example 1).

The above measurement results are shown in (Table 3) for each of sample numbers 36 to 40.

[0028]

[Table 3]

As can be seen from (Table 3), the sample without ZrO ₂ has a very large firing temperature dependence, but 0.01
If it exceeds mol%, the firing temperature dependency becomes smaller. If it exceeds 0.2 mol%, sintering inhibition will occur.

In the examples, MgO, Nb ₂ O ₅ and ZrO are used.
_{Although 2} is added separately, it has been confirmed that even if at least two elements are added at the same time, the effect can be exhibited without impairing the characteristics of each.

[0031]

As is apparent from the above description of the embodiments, the present invention has the general formula (Sr _x Ca _y Ba _z ) TiO ₃
And x, y and z represent a molar ratio, x + y
+ Z = 1 and the values of x, y, z are 0.55 ≦ x ≦ 0.85,
0.45 ≦ y ≦ 0.15, 0 ≦ z ≦ 5.0, and (S
_{r x Ca y Ba z) Bi} 2 O 3 as an additive with respect to TiO ₃
Is 0.5 to 8.0 mol%, and MgO is 0.5 to 2.
0.02 The Bi ₂ O ₃ and Nb ₂ O ₅ a large dielectric ceramic composition comprising a bending strength of 0 mol%, and as an additive
A dielectric ceramic composition having a high withstand voltage of 0.5 mol% and Bi ₂ O ₃ and ZrO ₂ as additives were added in an amount of 0.1%.
The present invention provides a dielectric ceramic composition of 01 to 0.2 mol% having a small capacitance firing temperature dependency.

[Brief description of drawings]

FIG. 1 is a sectional view of a trimmer capacitor using a dielectric ceramic composition of the present invention.

[Fig. 2] Similarly, an image diagram of bending strength measurement attachment

[Explanation of symbols]

 1 Stator electrode 2 Dielectric porcelain plate 3 Recessed part 4 Metal rotor 5 Adjustment recessed part 6 Spring 7 Cylindrical part 8 Support point 9 Test piece 10 Dial gauge

Claims (3)

[Claims]

1. The general formula (Sr_xCa_yBa_z) Ti
O₃And x, y and z represent a molar ratio, x
+ Y + z = 1, x, y, z values are 0.55 ≦ x ≦ 0.8
5, 0.45 ≦ y ≦ 0.15, 0 ≦ z ≦ 5.0,
(Sr_xCa_yBa _z) TiO₃As an additive to Bi
₂O₃Is 0.5-8.0 mol%, and MgO is 0.5-
A dielectric ceramic composition comprising 2.0 mol%.

2. The general formula (Sr_xCa_yBa_z) Ti
O₃And x, y and z represent a molar ratio, x
+ Y + z = 1, x, y, z values are 0.55 ≦ x ≦ 0.8
5, 0.45 ≦ y ≦ 0.15, 0 ≦ z ≦ 5.0,
(Sr_xCa_yBa _z) TiO₃As an additive to Bi
₂O₃Is 0.5 to 8.0 mol% and further Nb ₂O_FiveIs 0.0
A dielectric ceramic composition comprising 2 to 0.5 mol%.

3. The general formula (Sr_xCa_yBa_z) Ti
O₃And x, y and z represent a molar ratio, x
+ Y + z = 1, x, y, z values are 0.55 ≦ x ≦ 0.8
5, 0.45 ≦ y ≦ 0.15, 0 ≦ z ≦ 5.0,
(Sr_xCa_yBa _z) TiO₃As an additive to Bi
₂O₃Is 0.5-8.0 mol% and further ZrO₂Is 0.0
A dielectric ceramic composition comprising 1 to 0.2 mol%.