JP3289387B2 - 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 high dielectric constant dielectric porcelain composition, and more particularly to a high dielectric constant dielectric porcelain composition having a small temperature change rate and a small dielectric loss.

[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. Among the barium titanate-based porcelain compositions, as a material having a high dielectric constant and a small temperature change rate, a BaTiO-bismuth-based material and a BaTiO-based material are generally used.
₃ -Nb ₂ O ₅ -MnO ₂ based Introduction Numerous compositions are known. 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 However, the above BaTiO ₃ - The bismuth porcelain composition, if you try to apply a laminated capacitor, and a bismuth palladium or platinum-palladium alloy and the dielectric in the internal electrode Due to the reaction, there was a problem that expensive platinum had to be used as the internal electrode. on the other hand,
BaTiO ₃ -Nb ₂ O ₅ -MnO ₂ based dielectric ceramic is is excellent in the addition-frequency characteristics that overcome the above problems, the molar ratio of Ba and Ti, i.e. Ba / Ti
When the ratio is 1 or less, in the ordinary production method, a plate-like or needle-like crystal secondary phase is precipitated on the surface of the obtained sintered body. When this secondary phase is used for producing a multilayer capacitor and subjected to electrolytic plating, it causes plating to grow and causes a short circuit between external electrodes. Also, when mounted on a substrate, the surface of the element becomes uneven due to the generation of a secondary phase,
When the element was sucked, a displacement occurred, and the mounting rate was sometimes reduced. In addition, since a secondary phase occurs at the interface between the dielectric and the internal electrode, the internal electrode is pushed up during firing,
Since some discontinuous points of the internal electrodes were formed, the capacitance was varied. In addition, the composition range in which the rate of temperature change of the capacitance is small is very limited.

[0004]

Means for Solving the Problems A high permittivity dielectric ceramic composition of the present invention in order to solve this problem, as a main component
XBaO + yTiO ₂ + zSmO _3/2 (where x,
y and z indicate molar ratios and when expressed as x + y + z = 1),
Within the range enclosed by a, b, c, d, and e shown in Table 1
And as a secondary component to the above main component,
Ob is converted to the form of Nb ₂ O ₅ and 0.6 to 2.4 wt% is added.
And convert cobalt oxide to the form of Co ₂ O _3.
In addition, 0.1 to 0.8 wt% is added.

Alternatively , niobium oxide is converted into Nb ₂ O ₅ as a subcomponent with respect to the above main component in the form of 0.6 to 2.0.
4 wt%, and add manganese oxide and cobalt oxide.
Respectively 0.1 in total in terms of the form of MnO _2, Co ₂ O ₃
0.80 wt% (with the addition of MnO ₂
The allowable range is 0.01 to 0.40 wt% or less)
The present invention proposes a composition comprising:

[0006]

By using the dielectric ceramic composition of the present invention, the relative dielectric constant at room temperature has a high value of 2000 to 4700, and the dielectric loss (tan δ) is a small value of 1.1% or less. Above, the temperature change rate of the dielectric constant is JIS-C
JD characteristics specified in −5130 (in the temperature range of −25 ° C. to 85 ° C., the temperature change of the dielectric constant is +2
0% to -30%). Further, in the composition of the present invention, since the Ba / Ti ratio is larger than 1, a composition in which the generation of the secondary phase due to the excess of Ti is extremely small can be obtained.

[0007]

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a ternary composition diagram for explaining the composition range of the main components of the high dielectric constant ceramic composition according to the present invention, and FIG. 2 is a view showing the manufacturing process of the high dielectric constant ceramic composition of the present invention. is there.

First, a high purity BaTiO ₃ powder whose Ba / Ti molar ratio is adjusted to 1 and BaCO ₃ ,
Each powder of Sm ₂ O ₃ , MnO ₂ , Co ₂ O ₃ , Nb ₂ O ₅ was
The composition after sintering was weighed so as to be as shown in the following (Table 3 ), put into a rubber-lined ball mill equipped with an agate ball together with pure water, wet-mixed for 18 hours, and then dehydrated and dried. An appropriate amount of a 5 wt% solution of a PVA (polyvinyl alcohol) binder was added thereto, and the mixture was granulated.
Diameter 16 mm, thickness 0.6-0.8 mm under pressure of cm ²
Into a disk shape. Next, this molded product was used for 1250 to 1
It was baked while being kept at 350 ° C. for 2 hours. At this time, the temperature at which the density of the sintered body becomes maximum is set as the optimum firing temperature, Ag electrodes are baked on both surfaces of the disc of the obtained sintered body to form a capacitor, 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 ). (Table
Sample Nos. 3) and (Table 4) 7 is the scope of the present invention.
Does not belong to the enclosure.

[0010]

[Table 3]

[0011]

[Table 4]

Here, as shown in Table 4 , the sample N
o. For 1, 4, 5, and 7, JIS-C-5130
The JD characteristics in the standard are satisfied, and the rate of change of capacity at -25 ° C. and 85 ° C. and the rate of change at the Curie point are shown as (ΔC / C ₂₀ ) max. On the other hand, for other samples, JIS-C
Satisfies DR characteristics of -5130 standard, -25 ℃
And the rate of change of the capacity at 85 ° C.
The maximum rate of change in the range of 125 ° C. to 125 ° C. is shown as | ΔC / C ₂₀ | max.

FIG. 1 shows a ternary composition diagram for explaining the composition range of the main component in the composition of the present invention as described above, and is surrounded by a straight line connecting a, b, c, d, and e in the figure. The ternary components contained in the region defined are those of the composition of the present invention.

Next, the reasons for limiting the composition range of the present invention are shown in FIG.
This will be described with reference to FIG. First, the rate of change in capacitance is higher above the straight line ae, and does not satisfy the JD characteristics in JIS-C-5130 standard. Further, sintering is difficult at the left side of the straight line abc, which is not practical. Furthermore, below the straight line cd, the effect of adding SmO _3/2 is thin,
The dielectric constant is lowered and the sinterability is poor. Then, on the right side of the straight line de, a secondary phase is remarkably generated on the surface of the sintered body, and the dielectric constant is in a decreasing direction, which is not practical.

Further, Nb-Mn, Nb-
In the combination of Co or Nb-Mn-Co,
If Nb ₂ O ₅ is less than 0.6 wt%, the sinterability deteriorates, and the dielectric loss increases. On the other hand, if Nb ₂ O ₅ exceeds 2.4 wt%, the dielectric constant decreases, which is not practical. If the content of MnO ₂ is less than 0.01% by weight, there is no effect of adding MnO ₂ .
If it exceeds 40% by weight, the dielectric constant decreases and the rate of change in capacitance with temperature increases, which is not practical. Further, Co ₂ O ₃
Similarly, when the content exceeds 0.8 wt%, the dielectric constant decreases, and the rate of change in capacitance with temperature increases. On the other hand, when the content is less than 0.1 wt%, there is no effect of the addition, which is not practical.

In the combination of Nb-Mn-Co, MnO ₂ and Co ₂ O ₃ may be added in a total amount of 0.1 to 0.8 wt% with respect to the main component. The allowable range to which MnO ₂ is added is 0.01 to 0.40 wt% as is clear from the above description.

In the method of manufacturing the dielectric porcelain in the embodiment, oxides such as BaCO ₃ , Nb ₂ O ₅ , MnO ₂ , Sm ₂ O ₃ are used, but the present invention is not limited to this method.
After firing, the same characteristics can be obtained by using a carbonate, a hydroxide, or the like so as to obtain a desired composition. Also,
Even if the main component is calcined in advance and the subcomponent is added, the same characteristics as those of the embodiment can be obtained.

[0018]

The dielectric ceramic composition of the present invention has a high relative dielectric constant of about 2000 to 4700, a low dielectric loss (tan δ) of 1.1% or less, and a high dielectric constant. The rate of temperature change is based on J specified in JIS-C-5130.
JIS satisfying D characteristics or less
Satisfies the DR characteristics defined in C-5130 . Also,
Since the composition does not contain bismuth that easily reacts with palladium, it is possible to use palladium alone as the internal electrode. Furthermore, since the generation of the secondary phase on the surface of the sintered body is extremely small, when used for a multilayer chip capacitor, it is possible to manufacture a stable element with little plating and little variation in capacity. Also, when mounting on a board,
The element can be stably mounted, and is extremely useful in industrial use.

[Brief description of the drawings]

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

FIG. 2 is a view showing a manufacturing process diagram of a high dielectric constant dielectric porcelain composition according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01B 3/12 303 C04B 35/46 H01G 4/12 358

Claims (2)

(57) [Claims] 1. The main component is xBaO + yTiO ₂ +
zSmO _3/2 (where x, y, and z represent molar ratios and x + y
+ Z = 1) In the range surrounded by straight lines connecting a, b, c, d, e-shown, and as a secondary component to said main component in terms of niobium oxide in the form of Nb ₂ O ₅ 0.6 to with added 2.4 wt%, and the cobalt oxide obtained by adding 0.1～0.8Wt% in terms of the form of Co ₂ O ₃ high permittivity dielectric ceramic composition. 2. The main component is xBaO + yTiO ₂ +
zSmO _3/2 (where x, y, and z represent molar ratios and x + y
+ Z = 1) and when expressed, a shown in (Table 2), b, c,
In the range surrounded by the straight line connecting d and e, niobium oxide is added in an amount of 0.6 to 2.4 wt% in terms of Nb ₂ O ₅ as a subcomponent with respect to the main component, and Manganese and cobalt oxide are converted into MnO ₂ and Co ₂ O ₃ , respectively, in a total of 0.1 to 0.80 wt% (provided that the allowable range to which MnO ₂ is added does not include 0 wt%. (40 wt% or less). [Table 2]