JP3289378B2 - 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 recent years, there has been an increasing demand for ceramic multilayer capacitors that have a small size and a large capacity and also have 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 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 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 xBaO + yTiO ₂ + zSmO _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 5000, and the dielectric loss (tan)
δ) shows a small value of 1.1% or less, and the temperature change rate of the dielectric constant is the same as that of JIS-C-5130.
It is possible to satisfy D characteristics (a temperature change of dielectric constant in a temperature range of -25 ° C to 85 ° C is within + 20% to 30% based on 20 ° 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 ceramic 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 Sm ₂ O ₃ , MnO ₂ , MgO, Nb ₂ O ₅ was prepared, weighed so that the composition after firing was 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 granules were sieved through a mesh sieve and formed into a disk having a diameter of 16 mm and a thickness of 0.6 to 0.8 mm using a mold and a hydraulic press at a forming pressure of 1.5 ton / cm 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 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, 5, and 6, 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.

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 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, in the combination of Nb-Mg or Nb-Mg-Mn as secondary component, Nb is less than ₂ O ₅ is 0.6 wt%, sinterability is deteriorated, the dielectric loss increases, whereas 2 If it exceeds 0.4% by weight, the dielectric constant is lowered, which is not practical. MgO is 0.05wt%
If it is less than 0.80% by weight, on the other hand, if it exceeds 0.80 wt%, the dielectric constant is lowered and the rate of change in capacitance with temperature is increased, which is not practical. Further, when both MgO and MnO ₂ are added, the addition effect can be obtained if the total is 0.05 wt% or more, but the total addition amount is 0.80%.
If it exceeds wt%, the dielectric constant decreases, the rate of change in capacitance with temperature increases, and it becomes impractical. On the other hand, if the amount of MnO ₂ exceeds 0.40 wt%, the dielectric constant decreases, the rate of change in capacitance with temperature increases, and it becomes impractical.

In the method of manufacturing a dielectric ceramic having a high dielectric constant in this embodiment, BaCO ₃ , Nb ₂ O ₅ , MnO ₂ , Sm
_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 5000, 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-
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 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 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 +
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,
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]