JPH1029858A - High dielectric constant dielectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high dielectric constant dielectric porcelain compsn. suppressed in a capacity change and having superior characteristics. SOLUTION: This dielectric porcelain compsn. is based on xBaO+ yTiO2 +zPrO11/6 [where x+y+z=1 and (x), (y) and (z) are within the range defined by points (a), (b), (c), (d) and (e) in the diagram] and further contains 0.6-2.4 pts.wt. (expressed in terms of Nb2 O5 ) niobium oxide and 0.05-0.8 pt.wt. (expressed in terms of MgO) magnesium oxide as subsidiary components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-permittivity dielectric ceramic composition having a small temperature change rate and a small dielectric loss used for a fixed ceramic capacitor for electronic equipment, for example.

[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, many porcelain compositions including a BaTiO ₃ —Nb ₂ O ₅ —MnO ₂ system are generally known as materials having a high dielectric constant and a small rate of temperature change. I have. In recent years, there has been an increasing demand for a ceramic multilayer capacitor having a small size, a large capacity, and excellent high frequency characteristics.

[0003]

SUMMARY OF THE INVENTION BaTiO_Three-Nb_TwoO
_Five-MnO_TwoBaTiO3 based dielectric porcelain composition
_ThreeThe molar ratio of Ba and Ti, ie, the Ba / Ti ratio
Below, and in a normal manufacturing method,
A plate-like or needle-like crystal secondary phase precipitates on the surface,
When the secondary phase produces a ceramic multilayer capacitor,
Deposited on the element surface of the MIC multilayer capacitor,
When plating is applied, the plating becomes stretched, and between the external electrodes
This was the cause of short-circuit failure.

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. Then, when mounting the multilayer ceramic capacitor element, there are irregularities of the secondary phase on the element surface, so that when the element is adsorbed, the element may be displaced and the mounting rate may be reduced. Further, the composition range in which the rate of temperature change of the capacitance is small was very limited. Accordingly, the present invention provides a high dielectric constant dielectric porcelain composition which has no secondary phase, has a high relative dielectric constant and a low dielectric loss, and has a small change in dielectric constant with temperature.

[0005]

In order to achieve this object, a high dielectric constant dielectric porcelain composition of the present invention comprises xB as a main component.
When expressed as aO + yTiO ₂ + zPrO _11/6 (x + y + z = 1), these ternary components are represented by a, b, and
in a molar ratio range surrounded by a straight line connecting c, d, and e;
And with containing 0.6 to 2.4 parts by weight in terms of niobium oxide in the form of Nb ₂ O _5, further magnesium oxide in terms of the shape of the MgO 0.05 to respect the above-mentioned main components
0.8 parts by weight.

[0006]

[Table 2]

With this configuration, the relative dielectric constant at room temperature is about 2
000 to 4900, and the dielectric loss (ta)
nδ) shows a low value of 1.1% or less, and the temperature change of the dielectric constant is JIS-C-
5130 (the temperature change of the dielectric constant in the temperature range of -25 ° C to 85 ° C is within + 20% to -30%) and the JD characteristic or less can be satisfied.

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.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION According to the invention described in claim 1 of the present invention, when the main component is represented by xBaO + yTiO ₂ + zPrO _{1 1/6} (where x + y + z = 1), the ternary component is as shown in Table 2. in the range of a, b, c, d, the molar ratio of area enclosed by the lines connecting the e shown in, and as a secondary component to the main component in terms of niobium oxide in the form of Nb ₂ O ₅ 0. 6 ~
Containing 2.4 parts by weight of magnesium oxide and Mg
It is contained in an amount of 0.05 to 0.8 part by weight in terms of O, and satisfies the JD characteristic or less in a high relative dielectric constant, a low dielectric loss, and a change in dielectric constant.

The invention according to claim 2 further comprises manganese oxide as a sub-component, and the magnesium oxide and the manganese oxide are converted to the form of MgO and MnO ₂ , respectively, in a total of 0.05 to 0.8. Parts by weight (however, MnO
₂ is 0.4 parts by weight or less excluding 0 parts by weight), and satisfies the JD characteristic or less in a high relative dielectric constant, a low dielectric loss, and a temperature change of the dielectric constant.

[0011]

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

(Example 1) FIG. 1 is a ternary diagram showing the composition range of the main components of the high dielectric constant dielectric ceramic composition of the present invention, and shows a, b, c, d shown in (Table 2). , E indicate the composition of the present invention. FIG. 2 is a manufacturing process diagram of the high dielectric constant dielectric porcelain composition of the present invention.
High purity BaTiO ₃ powder whose Ti molar ratio is adjusted to 1 and BaCO ₃ , Pr ₆ O ₁₁ , MnO ₂ , MgO, Nb ₂ O ₅
Are prepared and weighed so that the composition after sintering becomes as shown in Table 3 and put together with pure water into a rubber-lined ball mill equipped with an agate ball, and after wet mixing for 18 hours (FIG. 1) 1) and dehydration drying (2 in FIG. 2).

[0013]

[Table 3]

An appropriate amount of a 5 wt% solution of a polyvinyl alcohol binder is added to the dried powder to make it homogenous.
The particles are sieved through a 2-mesh sieve, and the diameter is 16 m using a mold and a hydraulic press at a molding pressure of 1.5 ton / cm ^2.
m and a disk having a thickness of 0.6 to 0.8 mm (3 in FIG. 2).

Next, this molded disk is put into an alumina sheath covered with zirconia powder, and is placed in the air at 1250 to 1250.
It was held at 1350 ° C. for 2 hours and fired (4 in FIG. 2). The temperature at which the density of the sintered body becomes the maximum is defined as the optimum firing temperature, and silver electrodes are applied to both sides of the obtained sintered body disk and baked (5 in FIG. 2) to obtain a capacitor. The measurement was performed under the conditions of 1 KHz and room temperature of 20 ° C., and the rate of change in capacity with temperature was measured based on the capacity at 20 ° C. (6 in FIG. 2). The results of each measurement are shown in (Table 4).

[0016]

[Table 4]

In Table 4, samples NO1, 4, 5,
7 shows the JD characteristic in the JIS-C-5130 standard, and shows the maximum capacity temperature change rate at the Curie temperature by (ΔC / C ₂₀ ) m.
ax (%). In the case of the other sample NO, JIS-C-5130 having a smaller capacity temperature change rate was used.
Satisfies the DR characteristics in the standard, -25 ° C and 85
The maximum capacity temperature change rate is shown as | ΔC / C ₂₀ | max (%) in the case of the temperature change rate of the capacity in ° C. and the measured temperature range in the range of −55 ° C. to 125 ° C. at that time. Next, the reasons for limiting the composition range of the present invention will be described with reference to FIG. Above the straight line ae, the rate of change in capacitance with temperature is large, and the JD characteristics in JIS-C-5130 are not satisfied. On the left side of the straight line abc, sintering becomes difficult, which is not practical. Below the line cd, P
The effect of adding r 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 is decreasing, so that it is not practical.

When Nb 2 Mg or Nb—Mg—Mn is used as a sub-component and Nb ₂ O ₅ is less than 0.6 parts by weight, sinterability deteriorates and dielectric loss increases. If it exceeds 2.4 parts by weight, the dielectric constant decreases,
It becomes impractical. If the content of Co ₂ O ₃ is less than 0.05 part by weight, there is no effect of addition, and if it exceeds 0.80 part by weight, the dielectric constant is lowered and the rate of change in capacitance with temperature is increased, so that it is not practical. Further, when both MgO and MnO ₂ are added, the addition effect can be obtained if the total addition amount is 0.05 parts by weight or more, but if the total addition amount exceeds 0.8 parts by weight, The dielectric constant decreases, the rate of change in capacitance with temperature increases, and is not practical. Also, MnO
_If the addition amount of ( ₂ ) exceeds 0.40 parts by weight, the dielectric constant similarly decreases, and the rate of change in capacitance with temperature increases, which 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 , and Mn are used.
Oxides such as O ₂ and Pr ₆ O ₁₁ were used. However, the present invention is not limited to these methods, and the same applies to the use of carbonates, hydroxides, and the like so that a desired composition is obtained after firing. Characteristics 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.

[0020]

The high dielectric constant dielectric porcelain composition of the present invention is
The relative dielectric constant shows a high value of about 2000 to 4900, the dielectric loss (tan δ) shows not only a small value of 1.1% or less, but also the temperature change rate of the dielectric according to JIS-C-
5130 or less can be satisfied.

Since the composition does not contain bismuth which easily reacts with palladium, expensive Pt is used as an internal electrode.
Need not be used, and Pd alone can be used. 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. In addition, when the device is mounted on a substrate, the device can be stably mounted, which is extremely valuable 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 manufacturing process diagram of a high dielectric constant dielectric porcelain composition according to an embodiment of the present invention.

Claims (2)

[Claims] The main component is xBaO + yTiO ₂ + zP
When expressed as rO _11/6 (where x + y + z = 1), this ternary component is in a molar ratio range surrounded by a straight line connecting a, b, c, d, and e shown in (Table 1), and The main component 1
In addition to niobium oxide, niobium oxide contains 0.6 to 2.4 parts by weight in terms of Nb ₂ O ₅ as a secondary component,
Convert magnesium oxide to MgO form 0.05 ~
A high dielectric constant dielectric porcelain composition containing 0.8 parts by weight. [Table 1] 2. The composition further contains manganese oxide as a sub-component, and the magnesium oxide and the manganese oxide are converted to the form of MgO and MnO ₂ , respectively, in a total amount of 0.05 to 0.05.
_2. The high dielectric constant dielectric porcelain composition according to claim 1, comprising 0.8 parts by weight (provided that MnO ₂ is added in an allowable range of 0.4 part by weight or less excluding 0 part by weight). .