JPH05330909A - Porcelain composition of high dielectric constant - Google Patents

Abstract

PURPOSE:To obtain a composition having characteristics of a low sintering temperature and high dielectric constant. CONSTITUTION:The porcelain composition of a high dielectric constant is characterized by having a principal composition, prepared from PbO, MgO, Fe2O3, TiO2 and Nb2O5 and expressed by the general formula xPbTiO3-yPb(Mg1/3Nb2/3) O3zPb(Fe1/2Nb1/2)O3... (1) [when values of x, y and z are (x+y+z)=1 in formula (1), the values of x, y and z are respectively within the range of 0.02<=x<=0.06... (2), 0.80<=y<=0.92... (3) and 0.02<=z<=0.18... (4)].

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 porcelain composition suitable for a dielectric material such as a small size and large capacity multilayer ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, as a high dielectric constant porcelain composition, one containing barium titanate (BaTiO ₃ ) as a main component has been generally used. However, the porcelain composition containing barium titanate as a main component has a sintering temperature of 1300 to 1400.
The firing cost is high because it is a high temperature of ℃, especially when this porcelain composition is used as a multilayer capacitor, as an internal electrode material, to prevent reaction or oxidation with the dielectric even at such a high temperature, Precious metals with high melting point,
For example, Pt, Pd, etc. must be used, which has been a major obstacle to cost reduction of the monolithic ceramic capacitor. In order to solve this problem, a low-sintering temperature lead-iron-niobate-lead-magnesium-niobate-based dielectric porcelain composition which can use an inexpensive electrode containing Ag as a main component in a monolithic ceramic capacitor (Japanese Patent Application Laid-Open No. 2000-242242) 55-121957, JP-B-62-17805), or a lead titanate-lead magnesium niobate-based dielectric ceramic composition (JP-A-55-1).
21958 and JP-A-55-121959).

[0003]

However, among the above-mentioned conventional porcelain compositions, those of the lead iron niobate-lead magnesium niobate type have a low insulation resistance, and since they contain iron, they are dielectric materials with stable performance. Is hard to get. Further, the sintering temperature of the lead titanate-lead magnesium niobate system is not sufficiently low. Therefore, it has been desired to develop a porcelain composition that has a higher dielectric constant and insulation resistance than the conventional porcelain composition and can be sintered at a lower temperature. An object of the present invention is to provide a high dielectric constant porcelain composition which has a low sintering temperature and a large dielectric constant and can be used as a dielectric material for a small-sized and large-capacity laminated ceramic capacitor.

[0004]

In order to achieve the above object, a high dielectric constant porcelain composition of the present invention comprises PbO, MgO,
The main component composition prepared from Fe ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ is the general formula xPbTiO ₃ -yPb (Mg _1/3 Nb _2/3 ) O ₃ -zPb (Fe _1/2 Nb _1/2 ). Is expressed by O ₃ (1) and the values of x, y and z in the formula (1) are expressed as x +
When y + z = 1, the values of x, y and z are 0.02 ≦ x ≦ 0.06 (2) 0.80 ≦ y ≦ 0.92 (3) 0.02 ≦ z ≦ 0 .18 ... (4). It should be noted that, with MgO as an additive in the main component composition, 0.1
It may be contained in an amount of not less than 0.5% by weight and not more than 0.5% by weight.

The present invention will be described in detail below. The porcelain composition of the present invention is composed of the main component composition represented by the above formula (1). The reason for limiting the values of x, y and z of the main component composition will be described. In the above formula (1), when x is less than 0.02, the dielectric constant is small, and x is 0.0
If it exceeds 6, the dielectric loss increases. Therefore, the range of x is 0.02 ≦ x ≦ 0.06. Further, when y is less than 0.80, the dielectric loss becomes large, and when y exceeds 0.92, the sintering temperature becomes high. Therefore, the range of y is 0.80
≦ y ≦ 0.92. Further, if z is less than 0.02, the sintering temperature becomes high, and if z exceeds 0.18, the specific resistance becomes small. Therefore, the range of z is 0.02 ≦ z ≦ 0.1
8

The object of the present invention can be achieved even if MgO is added to the above main component composition. The reason for adding this MgO is
This is to further increase the dielectric constant. MgO when added
Is 0.1 when the main component composition is 100% by weight.
It is at least 0.5% by weight and at most 0.5% by weight. If it is less than 0.1% by weight, it hardly contributes to the improvement of the dielectric constant, and if it exceeds 0.5% by weight, the sintering temperature rises.

Production of such a high dielectric constant porcelain composition
For example, PbO, MgO, Fe ₂O₃, TiO₂as well as
Nb₂O_FiveWeigh powders such as
Mix well using a ball mill or the like. Given here
The ratio means that the above-mentioned mixed powder has the above-mentioned formula by firing described later.
(1) to (4) is a solid solution of the main component composition
It is the case.

Next, this mixture is dehydrated and dried, and then, if necessary, in a temperature range of about 600 to 800 ° C. for 0.5 to
Calcination for several hours. This calcination is not necessarily required, but it tends to make the particles more uniform and improve the dielectric properties. In the case of calcination, the calcined product is pulverized again by a wet ball mill, etc., dried, and then a binder such as polyvinyl alcohol or polyvinyl butyral is added to prepare granules, which are press-molded into a predetermined shape, and then calcined. To do. This firing is performed in the temperature range of about 750 to 1000 ° C. for about 0.5 to several hours.

[0009]

EXAMPLES Next, examples of the present invention will be described in order to show specific embodiments of the present invention. The examples described below do not limit the technical scope of the present invention. <Example 1> PbO, MgO, Fe as starting materials
₂ O ₃ , TiO ₂ and Nb ₂ O ₅ were used, these were weighed so as to have the seven compounding ratios shown in Table 1, and wet mixed with pure water in a ball mill for 24 hours. About MgO, 0.2% by weight was added in excess. Next, this mixture was dehydrated, dried at about 120 ° C., and then held at about 800 ° C. for 2 hours to be calcined. This calcined product was again wet-milled with pure water in a ball mill for 24 hours, dehydrated and dried at about 120 ° C. An aqueous polyvinyl alcohol solution was added to the obtained powder as an organic binder, and the molding pressure was about 200 kgf / cm.
² was pressed into a disk having a diameter of 15 mm and a thickness of 0.8 mm. 7 types of molded products based on 7 blending ratios were put in a magnesia porcelain container and as shown in Table 1, 950 to 1050 ° C.
Each was fired in the temperature range of 2 hours. 700 to 800 Ag electrodes are formed on both sides of a disk-shaped dielectric obtained by sintering.
After baking at a temperature of ° C, the electrical characteristics were examined. The results are shown in Table 1. (Hereafter, margins on this page)

[0010]

[Table 1]

<Example 2> As in Example 1, PbO, MgO, Fe ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ were used as starting materials.
Was used, and eight types of disk-shaped dielectrics were produced in the same manner as in Example 1 except that these were weighed so as to have eight compounding ratios shown in Table 2. The Ag electrode was baked on both surfaces of the obtained dielectric material in the same manner as in Example 1, and the electrical characteristics thereof were examined. The results are shown in Table 2. (Hereafter, margins on this page)

[0012]

[Table 2]

The dielectric constant and the dielectric loss were measured with a YHP digital LCR meter model 4274A at a measurement frequency of 1
The measurement was performed at a frequency of kHz, a measurement voltage of 1.0 Vrms and a temperature of 25 ° C. Also, the specific resistance is YHP analog IR meter model 43.
29 A was used, a voltage of 500 V was applied at a temperature of 25 ° C., and then, it was determined from the insulation resistance value after 1 minute. As is clear from Tables 1 and 2, the magnetic compositions (sample numbers 1 to 7 and 8 to 15) in which the composition ratios of the main components of x, y and z are within the range of the present invention are all dielectric constants and specific resistances. Is large, the dielectric loss is small, and the sintering temperature is low.

[0014]

As described above, since the high dielectric constant porcelain composition of the present invention has a large dielectric constant and a high specific resistance, it can be used as a dielectric material for a laminated ceramic capacitor to obtain a small-sized and large-capacity capacitor. You can Further, since the high dielectric constant porcelain composition of the present invention can be prepared at a low sintering temperature, the firing cost is small, and when manufacturing a laminated ceramic capacitor,
Since a relatively inexpensive Ag-based internal electrode can be used, the manufacturing cost of the monolithic ceramic capacitor can be significantly reduced.

Claims (2)

[Claims] 1. A main component composition prepared from PbO, MgO, Fe ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ has the general formula xPbTiO ₃ —yPb (Mg _1/3 Nb _2/3 ) O ₃ -zPb ( Fe _1/2 Nb _1/2 ) O ₃ (1) and the values of x, y and z in the above formula (1) are expressed as x +
When y + z = 1, the values of x, y and z are 0.02 ≦ x ≦ 0.06 (2) 0.80 ≦ y ≦ 0.92 (3) 0.02 ≦ z ≦ 0 .18 (4) The high dielectric constant porcelain composition is characterized in that 2. The high dielectric constant porcelain composition according to claim 1, wherein the main component composition contains MgO as an additive in an amount of 0.1% by weight or more and 0.5% by weight or less with respect to the main component composition.