JP3321826B2 - High dielectric constant 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 having a high dielectric constant among dielectric ceramic compositions for a fixed ceramic capacitor for electronic equipment, which has a small temperature change rate and a small dielectric loss. The present invention relates to a dielectric ceramic composition.

[0002]

2. Description of the Related Art Conventionally, barium titanate-based porcelain compositions have been widely used as dielectric materials for high dielectric constant ceramic capacitors. The material having a small temperature change rate in a high dielectric constant among the ceramic compositions of this barium titanate, generally BaTiO ₃ -Bi system, BaTiO ₃ -Nb
Including ₂ O ₅ -MnO ₂ system are known a number of ceramic composition. In addition, recent ceramic multilayer capacitors are very often required to have a small size, a large capacity, and excellent high frequency characteristics.

[0003]

SUMMARY OF THE INVENTION
Among the barium titanate-based porcelain compositions, BaTiO
_Three-In the Bi-based ceramic composition, a ceramic multilayer capacitor is used.
Palladium or white on the internal electrode
Reaction with Bismuth in Dielectric Using Gold-Palladium Alloy
Expensive platinum must be used for the internal electrodes.
There was a problem that must be done.

On the other hand, the BaTiO ₃ —Nb ₂ O ₅ —MnO ₂ based dielectric porcelain composition overcomes the above problems, but the BaTiO ₃ molar ratio in BaTiO ₃ , that is, the Ba / Ti ratio Must be 1 or less, and in a normal manufacturing method, a plate-like or needle-like secondary phase is precipitated on the surface of the obtained sintered body, and this secondary phase is produced when a ceramic multilayer capacitor is manufactured. It was deposited on the element surface of the ceramic multilayer capacitor, and when this was subjected to electrolytic plating, the plating spread, causing short-circuit failure between external electrodes.

[0005] Further, since a secondary phase is generated at the interface between the internal electrode and the dielectric, the secondary phase pushes up the internal electrode during firing, and some discontinuous points of the internal electrode are formed. It was causing variation. Further, the composition range in which the rate of temperature change of the capacitance is small was very limited.

On the other hand, when mounting a multilayer ceramic capacitor element, there are irregularities in the secondary phase on the element surface, so that when the element is adsorbed, a positional shift occurs, and the mounting rate may be reduced.

[0007]

In order to solve this problem, the high dielectric constant dielectric porcelain composition of the present invention comprises, as a main component, xBaO + yTiO ₂ + zNdO _3/2 (x + y + z =
When expressed as 1), the above ternary component is

[0008]

[Table 2]

[0009] is in the above range a shown in (Table 2), b, c, d , the molar ratio of area enclosed by the lines connecting the e, in terms of Nb relative to the main component Nb ₂ O ₅ 0. 6 to 2.4 parts by weight, and Co is converted to Co ₂ O ₅ to 0.1 to
0.8 parts by weight of Mn in terms of MnO ₂ 0.01 to
It is configured to contain at least one of 0.4 parts by weight.

[0010]

With this configuration, the relative dielectric constant at room temperature is about 200
It shows a high value of 0 to 4800, and the dielectric loss (tan)
δ) is as small as 1.1% or less, and the temperature change rate of the dielectric constant is JIS-C-5 based on 20 ° C.
It is possible to satisfy the JD characteristics or more specified in 130.

Further, since the Ba / Ti ratio in BaTiO ₃ is larger than 1, it is possible to obtain a material in which the generation of a secondary phase due to an excessive amount of Ti is extremely small.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a ternary diagram showing the composition range of the main components of the high dielectric constant dielectric porcelain composition of the present invention.
3 included in an area surrounded by a straight line connecting b, c, d, and e
The original components indicate the composition of the present invention.

FIG. 2 is a diagram showing the manufacturing process of the high dielectric constant dielectric ceramic composition of the present invention.
/ Ti molar ratio is adjusted to 1, high purity BaTiO ₃ powder, BaCO ₃ , Nd ₂ O ₃ , MnO ₂ , Co ₂ O ₃ , Nb
Each powder of ₂ O ₅ was prepared, weighed so that the composition after firing was as shown in Table 3 and put together with pure water into a rubber-lined ball mill equipped with an agate ball, and after 18 hours of wet mixing , Dehydrated and dried.

[0015]

[Table 3]

After adding an appropriate amount of polyvinyl alcohol and a 5 wt% solution to the dried powder to make it homogeneous, the granules are sieved through a 32-mesh sieve, and formed with a mold and a hydraulic press at a molding pressure of 1.5 ton / cm ² . Diameter 16mm, thickness 0.6 ~
It was formed into a 0.8 mm disk.

Next, the molded disk was placed in an alumina sheath covered with zirconia powder, and was placed in the air at 1250 to 1250.
It was baked while being kept at 1350 ° C. for 2 hours. The temperature at which the density of the sintered body becomes maximum is set to the optimum firing temperature, silver electrodes are applied to both surfaces of the obtained sintered body disk and baked to form capacitors, and each electric characteristic is measured at a frequency of 1 KHz and a room temperature of 20 ° C. The capacity temperature change rate was measured based on the capacity at 20 ° C. The results of each measurement are shown in (Table 4).

[0018]

[Table 4]

Next, the reasons for limiting the composition range of the present invention are shown in FIG.
This will be described with reference to FIG. Above the straight line ae, the rate of change in capacitance is large and does not satisfy the JD characteristics in JIS-C-5130 standard. On the left side of the straight line abc, sintering becomes difficult, which is not practical. Below the line cd,
The effect of adding Nd is thin, the dielectric constant is lowered, and the sinterability is poor.
On the right side of the straight line de, generation of a secondary phase is remarkable on the surface of the sintered body, and the dielectric constant tends to decrease, so that it is not practical.

Further, Nb-Co, Nb-Mn or Nb
In the combination of b-Mn-Co, Nb ₂ O ₅ is 0.6
If it is less than wt%, the sinterability deteriorates and the dielectric loss increases, and if it exceeds 2.4 wt%, the dielectric constant decreases and it becomes impractical. If MnO ₂ is less than 0.01 wt%, there is no effect of adding it, and if it exceeds 0.4 wt%, the dielectric constant is lowered and the rate of change in capacitance with temperature is increased, so that it is not practical. Further, when the content of Co ₂ O ₃ exceeds 0.8 wt%, the dielectric constant decreases and the capacity change rate increases.
If it is less than 0.1 wt%, the effect of the addition is not obtained, and it is not practical.

In the method of manufacturing a dielectric ceramic composition having a high dielectric constant according to the present embodiment, BaCO ₃ , Nb ₂ O ₅ , Mn
Oxides such as O ₂ and Nd ₂ O ₃ were used. However, the present invention is not limited to these oxides. Similar properties can be obtained even if carbonates, hydroxides, or the like are used to obtain a desired composition after firing. Can be obtained. Further, even if the main component is calcined in advance and then the sub-component is added, the same characteristics as in this embodiment can be obtained.

[0022]

The high dielectric constant dielectric porcelain composition of the present invention is
The dielectric constant shows a high value of about 2000 to 4800, the dielectric loss (tan δ) shows a small value of 1.1% or less, and the temperature change rate of the dielectric is JIS-C-
5130 or less can be satisfied.

Further, since the composition does not contain Bi which easily reacts with Pd, it is possible to use Pd alone as an internal electrode. Further, since the generation of the secondary phase on the surface of the sintered body is extremely small, it is possible to manufacture a stable multilayer ceramic capacitor element having a small plating spread and a small capacity variation when used in a multilayer ceramic capacitor. Also, when mounted on a board, the same element can be stably mounted,
It has a very high industrial utility value.

[Brief description of the drawings]

FIG. 1 is a ternary diagram illustrating a composition range of a main component of a high dielectric constant dielectric porcelain composition according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a high dielectric constant dielectric ceramic composition according to the example.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01B 3/12 303 C04B 35/46 H01G 4/12 415

Claims (1)

(57) [Claims] 1. The main component is xBaO + yTiO ₂ +
zNdO _3/2 (where x, y, and z represent molar ratios and x + y
+ Z = 1) , the above ternary components are as shown in Table 1. Is within a range of a molar ratio surrounded by a straight line connecting a, b, c, d, and e.
In the form of Nb ₂ O ₅ , containing 0.6 to 2.4 parts by weight, further converting Co to 0.1 to 0.8 part by weight in terms of Co ₂ O ₃ and Mn to MnO ₂ . A high dielectric constant dielectric ceramic composition containing at least one of 0.01 to 0.4 parts by weight in terms of conversion.