JPH05279106A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To improve dielectric constant of a ceramic composition by including a main component of a specific composition expressed by formula I and a by-product expressed by formula II in a prescribed weight ratio. CONSTITUTION:Powder of raw materials of PbO, CaCO3, Fe2O3, Nb2O5, ZnO, NiO, WO3 and MnCO3, etc., is weighted in prescribed blend ratios and subjected to wet blending with water. Then the blend is dehydrated and dried and then calcined at 600-800 deg.C. The calcined material is subjected to wet powdering and then dried and a binder such as PVA is added thereto to prepare granules and resultant granules are subjected to press molding. Then the resultant formed product is burned at 750-1000 deg.C for a prescribed time to provide the dielectric ceramic composition having high dielectric constant and low dielectric loss and containing a main component having a composition of formula I (R is Ca, Ba or Sr; M is Zn, Mg or Ni; 0.00<(a)<0.10, 0.00<(b)+(c)<0.05, 0.00<(b)<=0.20, 0.00<(c)<=0.20) and containing Pb(Fe1/2Nb1/2)O3, Pb(Zn1/3Nb2/3)O3 and Pb(M1/2W1/2)O3 and a subsidiary component expressed by formula II in the concentration of 0.01-0.50 pts.wt. based on 100 pts.wt. main component composition.

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

[0002]

2. Description of the Related Art Conventionally, as a high dielectric constant porcelain composition, a composition mainly containing barium titanate (BaTiO ₃ ) has been generally used. That is, the composition is BaTiO ₃
In general, the composition is a composition in which a shifter agent for moving the Curie point to around room temperature, a depressor agent for improving the twisting temperature characteristic, a sintering accelerator, a reduction inhibitor, and the like are added to the substrate. However, since the sintering temperature of the porcelain composition mainly composed of barium titanate is as high as 1300 to 1400 ° C., the firing cost is high, and especially when this porcelain composition is used as a laminated capacitor, it is used as an internal electrode material. Must use expensive noble metals, such as Pt and Pd, which have a high melting point so as not to react with the dielectric or oxidize even at such a high temperature, which is a great barrier to cost reduction of the multilayer capacitor. Was becoming.

On the other hand, in recent years, lead-based composite perovskies have been used.
At low temperature by using dielectric ceramic composition mainly composed of
Depending on the method of firing at
It is being reduced. Especially Pb (Fe_1/2Nb_1/2) O₃To
The porcelain composition containing it can be sintered at low temperature and has a high dielectric constant.
And various porcelain compositions centered on this component system
Proposed (eg M.Yonezawa: Ceramic Bulleti
n 62 (1983) 1375). Japanese Patent Laid-Open No. 2-252649
Is a Pb (Fe _{1 / 2}N
b_1/2) O₃, Pb (Zn_1/3Nb_2/3) O₃And Pb (M
_1/2W_1/2) O₃Is contained as a main component, and the main component composition has the general formula (Pb_1-aR_a) [(Fe_1/2Nb_1/2)_1-bc(Zn_1/3Nb_2/3)_b (M_1/2W_1/2)_c] O₃ Is represented by the formula (1), and R in the formula (1) is Ca, Ba or Sr.
At least one atom selected from the group consisting of
At least M is selected from the group consisting of Zn, Mg and Ni
Both are one kind of atom, and the values of a, b and c are positive numbers satisfying 0.00 <a <0.10 (2) 0.00 <b + c <0.50 (3) , A part of Pb atom is Ca, Ba and
And at least one atom selected from the group consisting of Sr
Dielectric porcelain compositions having a substituted composition are disclosed.
It This porcelain composition can be sintered at a temperature of about 1000 ° C
And has a high dielectric constant.

[0004]

However, the above-mentioned conventional porcelain composition is capable of low-temperature sinterability, and has a problem that the dielectric loss is large or the insulation resistance is small even if it has a high dielectric constant. It was still left. The object of the present invention is to provide a dielectric material for a small-sized and large-capacity multilayer ceramic capacitor, which has a low sintering temperature, a large dielectric constant, a low dielectric loss, a large insulation resistance, a small temperature change of the dielectric constant and the dielectric loss. An object is to provide a dielectric ceramic composition that can be used.

[0005]

In order to achieve the above object, the dielectric ceramic composition of the present invention comprises Pb (Fe _1/2 Nb
_1/2 ) O ₃ , Pb (Zn _1/3 Nb _2/3 ) O ₃ and Pb (M _1/2
W _1/2 ) O ₃ is contained as a main component, and the main component composition has the general formula (Pb _{1-a Ra} ) [(Fe _1/2 Nb _1/2 ) _1-bc (Zn _1/3 Nb _{2 / 3} ) _b (M _1/2 W _1/2 ) _c ] O ₃ (1) where R in the formula (1) is Ca, Ba and Sr.
At least one atom selected from the group consisting of
M is at least one atom selected from the group consisting of Zn, Mg and Ni, and the values of a, b and c are 0.00 <a <0.10 (2) 0.00 <b + c <0. .50 ... (3) is a positive number, and Pb (Mn _1/3
Nb _2/3 ) O ₃ is contained as an auxiliary component in an amount of 0.01 to 0.50 parts by weight based on 100 parts by weight of the main component composition.

The present invention will be described in detail below. The dielectric ceramic composition of the present invention comprises the main component composition represented by the above formula (1) and Pb (Mn _1/3) added to the main component composition in a predetermined ratio.
Nb _2/3 ) O _{3 and} its subcomponent composition. The reasons for limiting the composition range of the dielectric ceramic composition of the present invention will be described. In the above formula (1), when a is 0.00, the change in the dielectric constant with temperature becomes sharp, and when a is 0.10 or more, the peak of the dielectric constant shifts remarkably to the low temperature side and the dielectric constant is small. Become. Therefore, the range of a is 0.00 <a <0.10. Further, in the region satisfying b ≧ 0.50 in the above formula (1), Pb (Zn _1/3 Nb _2/3 ) O ₃ which does not form a perovskite structure in a normal solid-phase reaction has a main composition and has a dielectric constant. Is reduced. Further, in a region satisfying c ≧ 0.50, Pb (M _1/2 W _1/2 ) O which is an antiferroelectric substance is used.
₃ (where M is as described above) is the main composition, and the dielectric constant decreases. Furthermore, in the region where b + c ≧ 0.50 and b <0.50 and c <0.50 are satisfied,
Since the above two factors coexist, the permittivity also decreases. Therefore, b + c <0.50 must be satisfied. When b + c = 0, Pb (Fe _1/2 N
The composition is such that Pb of b _1/2 ) O ₃ is replaced with R (R is as described above), and good electrical characteristics cannot be obtained. For this reason,
0.00 <b + c.

In the present invention, particularly regarding b and c
Is preferably 0.00 <b ≦ 0.20 (4) 0.00 <c ≦ 0.20 (5). Limited composition as above
On the other hand, Pb (Mn_1/3Nb_2/3) O₃When added,
If the added amount is too large, the electrical characteristics are deteriorated. Obey
Pb (Mn _{1 / 3}Nb_2/3) O₃The addition amount of
With respect to 100 parts by weight of the composition represented by the formula (1), 0.
It is set to 01 to 0.50 parts by weight.

To produce such a dielectric ceramic composition of the present invention, for example, lead monoxide, calcium carbonate, barium carbonate, strontium carbonate, ferric oxide, niobium pentoxide, zinc oxide, magnesium oxide, Powders of nickel carbonate, tungsten trioxide, manganese carbonate and the like are weighed so as to have a predetermined ratio and sufficiently mixed using a wet ball mill or the like. Here, the predetermined ratio is a ratio at which the mixed powder becomes a solid solution having a main component composition represented by the formulas (1) to (3) by firing described later.

The mixture is then dehydrated and dried, then 6
Calcination is performed for several hours in a temperature range of about 00 to 800 ° C.
This calcination is not necessarily required, but it tends to make the particles more uniform and improve the dielectric properties. When calcined, the calcined product is pulverized again by a wet ball mill or the like, dried, and then an appropriate binder such as polyvinyl alcohol is added to prepare granules, which are press-molded into a predetermined shape and then calcined. .. This firing is 75
It is carried out in the temperature range of 0 to 1000 ° C. for 0.5 to several hours. Since each numerical value of the above manufacturing conditions is the most suitable value,
The porcelain composition of the present invention can be manufactured without being limited to this numerical range.

[0010]

EXAMPLES Examples of the present invention will be described below to show specific embodiments of the present invention. The examples described below do not limit the technical scope of the present invention. As starting materials, PbO, CaCO ₃ , Fe ₂ O ₃ , Nb ₂ O ₅ , ZnO, N
Using iO, WO ₃ and MnCO ₃ , these were weighed so as to have a compounding ratio of 16 shown in Table 1, and wet-mixed with pure water for about 20 hours in a ball mill. Pb (Mn _1/3 N
For b _2/3 ) O ₃ , as shown in Table 1, 0.00-
0.50 parts by weight was added. Next, this mixture was dehydrated, dried, and then held at 700 to 750 ° C. for 2 hours to be calcined. Approximately 2 parts of this calcined product was again mixed with pure water in the ball mill.
After wet pulverizing for 0 hours, it was dehydrated and dried. Polyvinyl butyral ethanol solution was added as an organic binder to the obtained powder, and the molding pressure was about 3 t / cm ³ , and the diameter was about 15 m.
m and a thickness of about 0.7 mm were pressed into a disk. 16 types of molded products based on the compounding ratio of 16 were held at about 600 ° C. for 1 hour to remove the binder, then placed in a magnesia porcelain container and fired at the temperature shown in Table 1 for 2 hours. Silver electrodes were baked on both surfaces of the obtained sintered body at 650 to 750 ° C. to form a parallel plate capacitor, and its electrical characteristics were examined. The results are shown in Table 2 and FIGS.

The dielectric constant and the dielectric loss were measured using a YHP digital LCR meter model 4274A at a measurement frequency of 1 kHz, a measurement voltage of 1.0 Vrms, and a temperature of 25 ° C. The insulation resistance is YHP analog IR meter 4
329A was used, and the value after 1 minute was measured at an applied voltage of 100 V at a temperature of 25 ° C. As is clear from Tables 1 and 2, the dielectric ceramic composition of the examples of the present invention (Sample Nos. 3 to 8) to which the subcomponent Pb (Mn _1/3 Nb _2/3 ) O ₃ was added.
And 11 to 16) are dielectric ceramic compositions of comparative examples (Sample Nos. 1, 2, 9 and 1) to which subcomponents are not added.
It can be seen that the dielectric loss and the insulation resistance are superior to 0). 1 is a sample number 5 (example), FIG. 2 is a sample number 1 (comparative example), FIG. 3 is a sample number 13 (example), and FIG. 4 is a sample number 9 (comparative example). The temperature characteristic of dielectric loss is shown. However, the dielectric constant is 25 ° C
Based on the value of, the temperature characteristics of the rate of change were shown. Figure 1
~ As is clear from Fig. 4, Pb (Mn _1/3 N
b _2/3 ) O ₃ is added in an amount within the range of the present invention, the porcelain composition of the example has a higher dielectric constant and a lower dielectric loss temperature than the porcelain composition of the comparative example in which the accessory component is not added. It can be seen that the change is small. (Hereafter, margins on this page)

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

As described above, the dielectric ceramic composition of the present invention can be sintered at a relatively low temperature of 900 to 950 ° C., has a high dielectric constant, a low dielectric loss, and a large insulation resistance. In addition, changes in dielectric constant and dielectric loss with temperature are small. Therefore, if it is used as a dielectric material for a monolithic ceramic capacitor, a compact and large-capacity capacitor can be obtained. Further, the dielectric ceramic composition of the present invention has a low firing cost because it is sintered at a low temperature, and when used as a material for a laminated ceramic capacitor, it does not use expensive precious metals such as Pt and Pd for the internal electrodes. A relatively inexpensive Ag-based metal can be used. As a result, the manufacturing cost of the monolithic ceramic capacitor can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a rate of change in dielectric constant and dielectric loss of a dielectric ceramic composition according to an example of the present invention with temperature.

FIG. 2 is a diagram showing the rate of change of the dielectric constant and the dielectric loss of a dielectric ceramic composition of a comparative example with temperature.

FIG. 3 is a diagram showing the rate of change in dielectric constant and dielectric loss with temperature of the dielectric ceramic composition of another example of the present invention.

FIG. 4 is a diagram showing the rate of change in dielectric constant and dielectric loss with temperature of the dielectric ceramic composition of another comparative example.

Claims (2)

[Claims] 1. Pb (Fe _1/2 Nb _1/2 ) O ₃ , Pb (Z
n _1/3 Nb _2/3 ) O ₃ and Pb (M _1/2 W _1/2 ) O ₃ are contained as main components, and the main component composition has the general formula (Pb _{1-a Ra} ) [(Fe _{1 / 2} Nb _1/2 ) _1-bc (Zn _1/3 Nb _2/3 ) _b (M _1/2 W _1/2 ) _c ] O ₃ (1) in the formula (1) R is Ca, Ba and Sr
At least one atom selected from the group consisting of
M is at least one atom selected from the group consisting of Zn, Mg and Ni, and the values of a, b and c are 0.00 <a <0.10 (2) 0.00 <b + c <0. .50 ... (3) is a positive number, and Pb (Mn _1/3 Nb _2/3 ) O ₃ is contained in the main component composition as an auxiliary component in an amount of 0.01 with respect to 100 parts by weight of the main component composition.
˜0.50 parts by weight is included in the dielectric ceramic composition. 2. b and c in the formula (1) are positive numbers satisfying 0.00 <b ≦ 0.20 (4) 0.00 <c ≦ 0.20 (5). The dielectric ceramic composition described.