JP3289379B2 - 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 ceramic capacitors, and has a small temperature change rate and a small dielectric loss. It relates to a 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. Among the barium titanate-based porcelain compositions, as a material having a high dielectric constant and a small temperature change rate, generally, BaTiO ₃ —Bi-based, BaTi
O ₃ -Nb ₂ O ₅ -MnO ₂ based started, it has been 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]

However, among the above-mentioned conventional barium titanate-based porcelain compositions, BaTi
The O ₃ -Bi-based ceramic composition, when used as a ceramic multilayer capacitor, since it reacts when using palladium or platinum-palladium alloy to the internal electrode and bismuth dielectric, without the use of expensive platinum as the internal electrodes There was a problem that had to be.

On the other hand, the BaTiO ₃ —Nb ₂ O ₅ —MnO ₂ based dielectric porcelain composition overcomes the above problems, but the Ba / Ti 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. Then, it is deposited on the element surface of the ceramic multilayer capacitor, and when this is subjected to electrolytic plating, the plating grows and causes a short circuit between the 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 a multilayer ceramic capacitor element is mounted, there are irregularities in the secondary phase on the element surface, so that when the element is adsorbed, a displacement may occur and the mounting rate may be reduced.

[0007]

SUMMARY OF THE INVENTION The high dielectric constant dielectric ceramic composition of the present invention in order to solve this problem, as a main _{component, xBaO + yTiO 2 + zDyO 3/2} ( where, x,
When y and z are molar ratios and expressed as x + y + z = 1 ), the ternary component is within the range of the molar ratio surrounded by a straight line connecting a, b, c, d, and e shown in (Table 1). and with respect to the main component in terms of niobium oxide in the form of Nb ₂ O ₅ 0.6 to
In addition to the addition of 2.4 wt%, magnesium oxide was added in an amount of 0.05 to 0.80 wt% in terms of MgO.
This is a configuration with addition .

Alternatively, niobium oxide is converted into Nb ₂ O ₅ as a sub-component of the above-mentioned main component in the form of 0.6-2.
It was added 4 wt%, and magnesium oxide and manganese oxide of MgO, respectively, in total in terms of the form of MnO ₂ 0.
05 to 0.80 wt% (However, the allowable range of adding MnO ₂ is 0.40 wt% excluding 0 wt%.
It proposes a composition prepared by adding the following).

[0009]

With this configuration, the relative dielectric constant at room temperature is about 200
It shows a high value of 0 to 4900 and the dielectric loss (tan δ)
Shows a small value of 1.0% or less, and the temperature change rate of the dielectric constant is the JD characteristic specified in JIS-C-5130 (in the temperature range of -25 ° C to 85 ° C, the temperature change of the dielectric constant is 20%). (Within + 20% to -30% based on ° C).

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 excess Ti is extremely small.

[0011]

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

FIG. 1 is a ternary composition diagram showing the composition range of the main components of the high dielectric constant dielectric porcelain composition according to the present invention, and is surrounded by a straight line connecting a, b, c, d and e in the figure. The ternary component contained in the region indicated is the composition of the present invention. FIG. 2 is a view showing the steps of manufacturing the high dielectric constant dielectric porcelain composition of the present invention.

First, a high purity BaTiO ₃ powder whose Ba / Ti molar ratio is adjusted to 1 and BaCO ₃ ,
Each powder of Dy ₂ O ₃ , MnO ₂ , MgO, Nb ₂ O ₅ is prepared, weighed so that the composition after firing is as shown in the following (Table 3 ), and a rubber lining provided with an agate ball. Was put into a ball mill together with pure water, wet-mixed for 18 hours, and then dehydrated and dried.

An appropriate amount of a 5 wt% solution of a polyvinyl alcohol binder is added to the dried powder to make it homogeneous.
The particles are sieved through a mesh sieve, and are molded using a mold and a hydraulic press at a molding pressure of 1.5 ton / cm ² and a diameter of 16 mm and a thickness of 0.1 mm.
It was formed into a disk of 6 to 0.8 mm.

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 baked while being kept at 1350 ° C. for 2 hours. At this time, the temperature at which the density of the sintered body becomes the maximum is defined as the optimum firing temperature, silver electrodes are applied to both surfaces of the obtained sintered body disk and baked to form capacitors. 20
C., and the rate of temperature change of the capacity was measured based on the capacity at 20 ° C. The results of each measurement are shown in (Table 4 ).

[0016]

[Table 3]

[0017]

[Table 4]

Here, as shown in (Table 4 ), the sample N
o. For 1, 4, and 6, the JD characteristics according to the JIS-C-5130 standard were satisfied, and the rate of change in capacity at -25 ° C and 85 ° C and the rate of change at the Curie point were (ΔC / C ₂₀ ) max. On the other hand, for other samples, JIS-C-5, which is more strict
It satisfies the DR characteristics in the 130 standard, and the capacity change rate at −25 ° C. and 85 ° C., and −55 to 1 at that time.
The maximum rate of change in the range of 25 ° C. is shown as | ΔC / C ₂₀ | max.

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. Further, below the straight line cd, the effect of adding DyO _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-Mg as a subcomponent or
In the combination of Nb-Mg-Mn, Nb_TwoO_FiveBut
If it is less than 0.6 wt%, the sinterability deteriorates and the dielectric loss is reduced.
On the other hand, when it exceeds 2.4 wt%, the dielectric constant decreases.
And become impractical. MgO is 0.05wt%
If it is less than 0.8%, the effect of the addition is not obtained.
The dielectric constant decreases and the capacitance temperature change rate increases.
It is not practical. Further, MgO and MnO_TwoBoth
If the total is more than 0.05 wt%
If the total effect is 0.8w
If it exceeds t%, the dielectric constant decreases, and the capacitance temperature change rate increases.
And become impractical. Also, MnO _TwoAmount of
If it exceeds 0.40 wt%, the dielectric constant similarly decreases,
The rate of temperature change is large, making it impractical.

Incidentally, in the method of manufacturing a high dielectric constant dielectric porcelain of this embodiment, BaCO ₃ , Nb ₂ O ₅ , MnO ₂ , Dy
_Although an oxide such as ₂ O ₃ was used, the present invention is not limited to these methods, and similar properties can be obtained by using a carbonate, a hydroxide, or the like so that a desired composition is obtained after firing. be able to. 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 4900, the dielectric loss (tan δ) shows a small value of 1.0% or less, and the temperature change rate of the dielectric is JIS-C-
Satisfy the JD characteristics as defined in 5130, many more standard
The strict DR characteristics specified in JIS-C-5130
Satisfaction and prevention of secondary phase precipitation of the sintered body
Short circuit failure between them can be prevented.

Further, since bismuth which easily reacts with palladium is not contained in the composition, palladium alone can be used as the internal electrode. Further, since the generation of secondary phases 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 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 +
zDyO _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 A high dielectric constant dielectric porcelain composition comprising 2.4 wt% of magnesium oxide and 0.05 to 0.80 wt% of MgO in terms of MgO. 2. The main component is xBaO + yTiO ₂ +
zDyO _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,
Niobium oxide is added in an amount of 0.6 to 2.4 wt% in terms of Nb ₂ O ₅ as a sub-component with respect to the main component and is in a range surrounded by a straight line connecting d and e. MgO magnesium and manganese oxide, respectively, 0.05～0.80Wt% in total in terms of the form of MnO ₂ (where less 0.40 wt% tolerance applied the MnO ₂ is not containing 0 wt% in these A) a high dielectric constant dielectric porcelain composition comprising: [Table 2]