JPH0360452A - Dielectric ceramic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dielectric ceramic composition, which can be sintered at low temperatures, suppresses grain growth in the sintered body, and has a high dielectric constant and low loss. The present invention relates to a dielectric ceramic composition that has dielectric properties and is suitable as a dielectric material for, for example, small-sized, large-capacity multilayer capacitors.

[Prior Art] Conventionally, as a high dielectric constant ceramic composition, a composition mainly containing barium titanate (BaTiOa) has been used for -M. That is, the composition is generally made of BaTiO3 as a base, to which are added a shifter agent that moves the Curie point to around room temperature, a depressor agent that improves the capacitance-temperature characteristics, and a sintering accelerator, reduction inhibitor, etc. be.

As a shifter agent, BaSnO3, BaZrO3, C
aZrO3, CaSnO3SrTiO3, PbTiO3
, La2O3°CeO2, etc. are used, and depressor agents include CaTiO3, MgTiOz, B12(S
nO3)s, Bi2 (TiO3)3NiSnOs, M
gZrO3, Mg5nOs, etc. are used. Further, as the sintering accelerator, AJ220a, S io2. Z
nO, CeO2゜B203, Nb205, WO2, etc. are used, and as reduction inhibitors, MnO2, Fe2
03°CuO etc. are used.

[Problems to be Solved by the Invention] However, since the sintering temperature of a composition mainly composed of BaTiOs is as high as 1,300 to 1,400°C, the firing cost is high, and especially when it is used as a multilayer capacitor, the internal Expensive precious metals such as palladium and platinum had to be used as electrodes, which was a problem in reducing the cost of multilayer capacitors.

Moreover, the dielectric constant of a composition mainly composed of BaTfOa is 1.0000 degrees at most, so in order to obtain a small-sized, large-capacity multilayer capacitor, a large number of circuits must be used.
As expected, this was the major obstacle to reducing manufacturing costs.

For this reason, it is possible to use an inexpensive electrode containing Ag as the main component as the internal electrode, and also to reduce the manufacturing cost of the multilayer capacitor by keeping the number of layers small.
There is a demand for the emergence of high permittivity dielectric materials that can be sintered at low temperatures.

Many compositions have been proposed in which the lead-based composite perovskite type compound can be sintered at low temperatures. In particular, P b (F e l/2 N b l/2)
A composition containing 03 and P b (F e2y3W!/3)03 can be sintered at a low temperature and has a high dielectric constant,
Various compositions have been proposed centering on this two-component system (for example, M. Yonezawa: Cerami
cBulletin [i2 (1983) 1375
). However, when such a composition containing PB or W is used, the crystal grain size in the sintered body becomes large, making it unsuitable for thinning the layer. On the other hand, if the material is fired at a low temperature that can speed up crystal grain growth, there will be problems such as not being able to obtain excellent electrical properties.

Therefore, there is a demand for a high dielectric constant dielectric material that can be sintered at low temperatures and exhibits excellent electrical properties while suppressing grain growth in the sintered body.

The present invention was made in view of the above-mentioned conventional circumstances, and it is possible to perform low-temperature sintering, suppress grain growth in the sintered body, and have a high dielectric constant. It is an object of the present invention to provide a dielectric ceramic composition that has a small loss (tan δ) and allows manufacturing of small-sized, large-capacity multilayer capacitors, etc. at low cost.

[Means and Effects for Solving the Problems J The dielectric ceramic composition of the present invention has Pb(FetzzNb+7z)03
, Pb (Zn+z3Nb273)03 and Pb
(M+/2 Wl/2) 03 (In a composition containing the D3 component as a main component, some of the pb atoms are replaced by Ca, B
a and S "M-substituted with at least one atom selected from the group consisting of - formula (I) (P b + - a Ra ) [(F er/2N b
uzz ) 1-b-c(Z n l/3 N b 2
/3) b(M+/2 Wl/2) c] 03
...(I) (R is at least one selected from the group consisting of Ca, Ba and Sr, M is at least one selected from the group consisting of Zn, Mg and Ni) When expressed as: 0.00< ago, 10 0.00<b+c<0.50 As shown by the calcined product,
and NbzOs, respectively in weight% 0.00<PbO
<1.5 0.00<Nbz Os <1.0 The present inventors have previously developed a high dielectric constant dielectric ceramic composition that can be sintered at a temperature of about 1000°C. proposed a composition having the composition represented by the above-mentioned formula (1) (Japanese Patent Application No. 1-74573).
. The dielectric 6R composition of the present invention is obtained by adding predetermined amounts of PbO and Nb2O as subcomponents to the calcined product made of this composition system, thereby achieving a
The object of the present invention is to provide a high dielectric constant dielectric IIf1 composition that can be sintered at a temperature around 50°C and exhibits excellent electrical properties while suppressing grain growth in the sintered body.

The present invention will be explained in detail below.

First, the reason for limiting the composition range of the dielectric ceramic composition of the present invention will be explained.

In the above formula (1), if a is 0.00, the temperature change in the dielectric constant will be rapid, and if a is 0.10 or more, the peak of the dielectric constant will shift significantly to the low temperature side, resulting in a small dielectric constant. Become. Therefore, the range of the value of a is 0.00<a<0.10.

In addition, in the region where b≧0.50 is satisfied in the above formula (1), the main composition is P b (Z nl/3N b27s )03, which does not form a perovskite structure in a normal solid phase reaction, and the dielectric constant decreases. . In addition, in the region satisfying C20,50, Pb (M+
/2 Wl/2 ) 03 (where M is as described above) becomes the main composition, and the dielectric constant decreases. Furthermore, b+c≧
In the region satisfying 0.50 and boo, 50, c<0.5, the two factors described above coexist, so the dielectric constant also decreases. Therefore, b+c<0.50 must be satisfied. Moreover, when b+c=o, pb(F e
1/2 N b 1/2 ) 03 is substituted with R (R is as described above), and good electrical characteristics cannot be obtained. Therefore, 0.00<b+c.

In the present invention, especially o, oo<b≦0.20 0.0oz≦0,20 It is preferable that

As shown in the calcined product having a limited composition as described above, when only NbzOa is added, grain growth in the sintered body is significantly suppressed depending on the amount added, but on the other hand, sintering becomes worse. Dielectric constant and insulation resistance decrease. As shown, when PbO and Nb2O5 are added at the same time, grain growth is suppressed, low-temperature sintering is possible, and the dielectric constant and insulation resistance do not decrease. From this, it is necessary to add PbO, Nb, and O at the same time. However, PbO and Nbz
If the amount of Os added is too large, sintering may become unstable,
This is undesirable because it causes deterioration of electrical characteristics and a decrease in reliability and strength. Therefore, the amounts of PbO and Nb2O5 added are 0.00<PbO<1 by weight, respectively, as represented by the calcined product having the composition represented by formula (I) above.
．． 5 0.00<Nt)zOs<1.0.

To produce such a dielectric ceramic composition of the present invention,
For example, - powders of lead oxide, calcium carbonate, barium carbonate, strontium carbonate, ferric oxide, niobium pentoxide, zinc oxide, magnesium oxide, nickel carbonate, tungsten trioxide, etc. are weighed in a predetermined proportion and wet-processed. Mix thoroughly using a ball mill or the like. Next, after drying this mixture, if necessary, it is calcined at a temperature in the range of 600 to 800°C for several hours. Predetermined amounts of PbO and NbzOs are added to the obtained calcined product, and the mixture is pulverized using a wet ball mill or the like.

After drying the calcined powder obtained by pulverization, a suitable organic binder such as polyvinyl alcohol is added to make granules.
After press-molding this into a predetermined shape, firing is performed.

This firing is carried out at a temperature range of 750 to 1000°C.
Do this for about a few hours. (Of course, these manufacturing conditions are the most suitable values, and the porcelain composition of the present invention may be manufactured under conditions or methods other than those described above.) [Examples] The present invention will be described below with examples. The present invention will be described in more detail below, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 PbO, CaCO3, Fe2O3, Nb as starting materials
20s, ZnO and wag, and these were
In formula (I), ayob=c=0.05. R=Ca
, M=Zn, and mixed in a ball mill with pure water in a groove for about 20 hours. Next, the mixture was dried and calcined by holding at 700 to 750°C for 2 hours.

Add PbO and N to this calcined product in the mixing ratio shown in Table 1.
However, in No. 1 to 4, Nb2O is added.
, only added), and again in a ball mill with pure water for about 20 min.
After time slot pulverization, it was dried.

A polyvinyl alcohol aqueous solution (organic binder) was added to the obtained powder, and the bottom pressure was about 2 tons/c tn.
', diameter 15mm, thickness approximately 0. It was pressure molded into a 7 mm disc. The molded product was held at about 600° C. for 1 hour to remove the binder, then placed in a magnesia porcelain container and fired at the temperatures shown in Table 1 for 3 to 18 hours.

Silver electrodes were baked on both sides of the obtained sintered body at 650 to 700°C to form a parallel plate capacitor, and its electrical properties were investigated.

The results are shown in Table 1.

Note that the dielectric constant and dielectric loss were measured using YHP digital LCR meter model 4274A, with measurement frequency lKH2 and measurement voltage 1. OVrms was measured at a temperature of 25°C. Also,
The insulation resistance was measured using a YHP analog IR meter 4329A at a temperature of 25° C. and an applied voltage of 100 V after 1 minute. In addition, after polishing the cross section of the single-plate sample, it was chemically etched using an appropriate etchant, and the average grain size of the crystal grains in the sintered body was determined by observing the cross section with an optical microscope.

As is clear from Table 1, all of the compositions within the scope of the present invention have a high dielectric constant, a low dielectric loss, and
It exhibits excellent electrical properties with a relatively large capacitance-resistance product, and also has the advantage of a low sintering temperature and a small crystal grain size in the sintered body.

[Effects of the Invention] As detailed above, the dielectric ceramic composition of the present invention has a high dielectric constant and low loss, and has a relatively large capacitance-resistance product. The crystal grain size in the aggregate is small. Therefore, by using the dielectric magnetic composition of the present invention, a highly reliable small-sized, large-capacity capacitor can be obtained.

One possibility is that the dielectric ceramic composition of the present invention has a low sintering temperature, so the firing cost is low, and when used in a multilayer capacitor, there is no need to use expensive noble metals such as palladium or platinum for the internal electrodes. , relatively inexpensive metals such as silver thread can be used. Therefore, the manufacturing cost of multilayer capacitors can be reduced, and their prices can be significantly reduced.

Claims (1)

[Claims] (1) Pb(Fe_1_/_2Nb_1_/_2)O_
3, Pb(Zn_1_/_3Nb_2_/_3)O_3
and Pb(M_1_/_2W_1_/_2)O_3 as main components, and has the following general formula (I) (Pb_1_-_aR_a)[(Fe_1_/_2Nb
_1_/_2)_1_-_b_-_c(Zn_1_/_
3Nb_2_/_3)_b(M_1_/_2W_1_/
_2)_c]O_3...(I) [wherein, R is at least one kind selected from the group consisting of Ca, Ba and Sr; M is at least one kind selected from the group consisting of Zn, Mg and Ni a, b and c is a positive number that satisfies 0.00<a<0.10 0.00<b+c<0.50], some of the Pb atoms are replaced by Ca,
For a calcined material having a composition substituted with at least one type of atom selected from the group consisting of Ba and Sr, PbO and Nb_2O_5 were added in weight% of 0.00<PbO<1.5 0.00<Nb_2O_5< 1.0 A dielectric ceramic composition characterized by having an additive composition.