JPS63319242A - High-dielectric constant ceramic composition - Google Patents

Abstract

PURPOSE:To obtain the title ceramic composition having high dielectric constant and insulation resistance and capable of being sintered at low temp. by substituting a part of the Pb having the composition within the region obtained by connecting the specified points in a ternary phase diagram with the apexes corresponding to the respective components in a specified ceramic composition for Ca. CONSTITUTION:A part of the Pb having the composition within the region obtained by connecting the following points in the ternary phase diagram with the apexes corresponding to the respective components in the ceramic composition shown by the formula is substituted for 2-30mol.% Ca to obtain a ceramic composition. The points are shown by (a) (x=0.60, y=0.39, and z=0.01), (b) (x=0.60, y=0.05, and z=0.35), (c) (x=0.45, y=0.05, and z=0.50), (d) (x=0.01, y=0.49, and z=0.50), (e) (x=0.01, y=0.85, and z=0.14), and (f) (x=0.14, y=0.85, and z=0.01). In addition, <=1.0mol.% of at least one kind, expressed in terms of Mn, Co, NiO, and Cr2O3, can be incorporated, as required.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a high-temperature ceramic composition, which can be sintered at low temperature and has a high insulation resistance, which is particularly suitable for multilayer ceramic capacitors. The present invention relates to a high dielectric constant ceramic composition that has excellent electrical properties such as high electrical properties.

(Prior art) Electrical properties required for dielectric materials include dielectric constant, temperature coefficient of dielectric constant (T, C, C), dielectric loss, dielectric bias electric field dependence, capacitance-resistance product, etc. .

In particular, the capacitance-resistance product (CR value) must be sufficiently high, and must be 500MΩ・μF or more at room temperature according to EIAJ (Electronic Industries Association of Japan) standard RC-3698B for multilayer ceramic capacitors (chip type) for electronic equipment. stipulated. Furthermore, it is required to maintain a high CR value even at high temperatures (for example, the U.S. Department of Defense standard MIL-C-55681B stipulates a CR value at 125° C.) so that it can be used under even more severe conditions.

Furthermore, when considering a laminated type element, since the electrode layer and the dielectric layer are fired as one unit, it is necessary to use an electrode material that is stable even at the current temperature of the dielectric material. Therefore, if the firing temperature of the dielectric material is high, platinum (Pt
), expensive materials such as palladium (Pd) must be used, and in order to be able to use inexpensive materials such as silver (Ag), firing at a low temperature of about 1100°C or less is required. Ru.

Conventionally known high dielectric constant ceramic compositions include those based on barium titanate, in which lead stannate, lead zirconate, lead titanate, etc. are dissolved. Although it is certainly possible to obtain a material with a high dielectric constant, problems arise in that as the dielectric constant increases, T, C, and C0 become larger, and the bias electric field dependence also becomes larger. Furthermore, the firing temperature of barium titanate-based materials is 1300 to 140
Due to the high temperature of around 0℃, platinum,
An expensive material such as palladium that can withstand high temperatures must be used, which causes high costs.

In order to solve the problems of barium titanate, various compositions have been studied. For example, those based mainly on iron lead niobate (Japanese Patent Application Laid-Open No. 57-57204), those based mainly on magnesium lead niobate (Japanese Patent Application Laid-Open No. 55-517)
No. 58), and one mainly composed of magnesium and lead tungstate (Japanese Patent Application Laid-open No. 52-2LH9). Those containing lead iron niobate as a main component have a problem in that the CR value changes greatly depending on the firing temperature, and the CR value decreases particularly at high temperatures. Products mainly composed of magnesium and lead niobate have a relatively high firing temperature, and also contain magnesium and lead niobate.
A material mainly composed of lead tungstate has the problem that when the CR value is large, the dielectric constant is small, and when the dielectric constant is large, the CR value is small. Furthermore, T, C, C of these materials
, is superior to the barium titanate system, but is not sufficient.

Furthermore, research has also been conducted on materials in which a solid solution of magnesium/lead niobate and lead titanate is used, in which part of the lead is replaced with barium, strontium, or calcium as necessary (Japanese Patent Laid-Open No. 121959/1983).

However, the T, C, C, of this material ranges from -25°C to 85°C.
Even the best one at °C is -59.8%, which is not sufficient. Furthermore, the above publication does not mention the CR value, which is the most important value for capacitor materials, and its usefulness as a capacitor material is not clear.

Further, in Japanese Patent Application Laid-Open No. 57-25807, solid solution materials of magnesium lead niobate and zinc lead niobate are also studied. However, the CR value and T, C,
No mention is made of C, and its usefulness as a capacitor material is unclear.

Furthermore, materials that are solid solutions of zinc lead niobate and nickel lead niobate, in which part of the lead is replaced with barium, strontium, or calcium, are also being researched (Japanese Patent Laid-Open No. 58-214201 issue). However, there is no mention of CR value, and its usefulness as a capacitor material is unclear. Furthermore, JP-A-59-105208 discloses a solid solution of lead magnesium niobate, lead zinc niobate, and lead nickel niobate. However, there is no mention of CR value, and its usefulness as a capacitor material is unclear.

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above points, and addresses the problems of the prior art, namely: ■ High firing temperature ■ CR value is small when dielectric constant is high ■ At high temperature The purpose is to provide a high dielectric constant ceramic composition that solves the problem of low CR value (insulation resistance), etc., has high dielectric constant and insulation resistance, and has excellent electrical properties that can be sintered at low temperatures. shall be.

[Structure of the Invention] (Means for Solving the Problems) The present invention essentially provides lead zinc niobate (Pb (Znl13
Nb213)03), magnesium lead niobate (Pb
(Mgl13Nb213) 03 ), a part of the three elements pb of lead zirconate (Pb Zr 03 )
When expressed by the general formula % formula %, a of the ternary diagram with each component as the vertex is a (x −0, BO, y= 0.39, z” 0.
OL)b(x'-0,BO,Y=0.05,
z= 0.35)c (x= 0.45, y=
0.05, z -0,50)d (x -0,OL
, Y= 0.49, z= 0.50)e (x=
0.01, y=0.85, z=0.14)f
(x= 0.14, Y= 0.85, z= 0
．． This is a high dielectric constant ceramic composition characterized in that a part of Pb in the composition within the line connecting each point indicated by OL is replaced with 2 to 30 moJ% of Ca.

Furthermore, in the high dielectric constant ceramic composition having the above-mentioned composition range, Pb and Ca elements are replaced by As Z n s Mg 5
NbsZr, a high dielectric constant ceramic composition where the element is B and the chemical formula of these composite compounds is expressed as ABO3, the molar ratio of A/B is within the range of 1.00≦A/B<1.10 It is.

In addition, manganese, cobalt, nickel,
Chromium M n Os Co OSN i O%Cr2
When converted to O3, at least one is 1. Om
This is a high dielectric constant ceramic composition in which the content is oρ% or less.

(Function) The function of each means in the present invention and the reason for limiting the composition range will be explained below.

The porcelain composition defined in the present invention is x-Pb (Znl13Nb273) 03-y
@Pb (Mgl13Nb213)03-2-Pb
A part of pb in the shaded area of FIG. 1 showing the ZrO3 ternary diagram is replaced with 2 to 30 mo % of Ca. Note that each point in Figure 1 is a (x - (1, BO, y - 0, 39, z - 0, 0
1) b (x -0,60, Y= 0.05, z=
0.35 ) c (x −0,45, Y= 0.05
,z=0.50)d(x=0.01,Y-
0,49, z= 0.50 )e (x-0, 吋, y=
0.85,z=0.14)f(x-0,1
4, y=0.85, z=0.01).

In the region (■) where Pb (ZnlI3Nb2.) 03 is more abundant than the a-b line, the dielectric constant is as low as 3000 or less, and the insulation resistance is also as small as 1010 Ωcm (25° C.) or less.

Pb (Mgl13Nb213) Oa from be-e line
In the region (■) where the resistance is small, the dielectric constant is as small as 3000 or less, and the CR value at room temperature is also 1000 Ω·F or less.

In the region (■) where there is more Pb Zr 03 than the c-d line,
The sintered body had many bores, making it impossible to obtain a satisfactory porcelain product.
The insulation resistance is also less than 1010 Ωcm, and the CR value is also extremely small.

P b (Z nL7aN b27g) from the de line
In the region (■) with less 03, the firing temperature exceeds 1100° C. and the insulation resistance becomes low.

P b (Mg1laN b27a) from e-f line
In the region (■) with a large amount of 03, the firing temperature becomes high and the CR value also becomes 1000 ΩF or less.

Also, b-(x=0.8, yo, 2, z-0,2)C
'' (x=0.3, y=0.2, z-0,5), p l) (M gt, I'J
b2 /3) A region with a large amount of 03 is more preferable, and a ceramic composition having a dielectric constant of 5000 or more can be obtained.

Furthermore, e − (x = 0.01% y −0,8
,2-0,19),f-(x=0.5,yo-o,
5, z-0), P b (
A region with a small amount of M gL73N b273)03 is more preferable, and a ceramic composition having a CR value of 1000 ΩF or more can be obtained even at high temperatures.

In addition, the temperature dependence of the dielectric constant is greatly influenced by the position of the Curie temperature (Tc), but a-b-c-d-e-f
+22% relative to room temperature value in the range of -30°C to +85°C by substituting a part of PB of the composition in the range of
Fluctuations within ~-56%, US standard EIAY5
Characteristics satisfying U can be obtained.

The substitution amount of Ca is preferably 2 mob% to 30mo42%, and when it is less than 2 mob%, the sintering temperature is 1100%.
C, and the CR value also falls below 1000ΩF. In addition, if the replacement exceeds 30 oI1%, there will be many bores in the sintered body, and the insulation resistance will also be 1010Ω.
It falls below Qm, and the CR value becomes extremely small.

Therefore, the amount of Ca substitution is set to 2 to 30 moJ%.

Furthermore, in the ceramic composition of the present invention, pb and C
A SZ n SM g SN' b SZ
Let the r element be B, and the chemical formula of these composite compounds is ABO.
3, the molar ratio of A/B is 1.00≦A/
It is preferable that B<1.10. 1.0
When it is smaller than 0, the dielectric constant decreases and the dielectric loss exceeds 1.5%, which is not practical.

Moreover, if it exceeds 1.10, the insulation resistance begins to decrease, which is not preferable. Therefore, the range of A/B is 1.00
≦A/B<1.10. When pb is substituted with Ba or Sr instead of Ca substitution, A/B is 1.00.
If it is larger, the dielectric constant will decrease, contrary to the case of Ca substitution. This means that the Cal conversion of pb is Ba, Sr.
This is thought to indicate that it cannot be treated in the same way as substitution, but the reason remains unclear.

The present invention is mainly based on what is represented by the above general formula. When this composition is converted into oxide, P b O5'3.53 ~ H, 54w t
%Zn0 0.08 ~ 5.74
wt% M g 0 0.19
~4.12wt%Nb
20s 12.28 ~31J4
W t % Z r 0 2
0.3e ~21.58wt
%CaOO, 33-6.28 wt
%.

In addition, in the present invention, the same effect may be obtained even if the ratio is slightly deviated and does not satisfy the above-mentioned chemical formula.

Further, impurities, additives, substitutes, etc. may be contained within a range that does not impair the effects of the present invention. For example, other Sb20 (Mn0SCoo, N1pSCr203 listed above)
3, TiO2, La203, etc. The content of these additives is about lvt% at most.

Next, a method for producing the composition of the present invention will be explained.

Pbs Cas Zns Nbs Zr as starting materials
5Mg oxide or salts such as carbonate and oxalate which become oxides by firing, hydroxide, organic compounds, etc. are weighed out in predetermined proportions, thoroughly mixed, and then calcined. This calcination is performed at about 700°C to 850°C.

If the calcination temperature is too low, the sintered density will decrease, and if it is too high, the sintered density will also decrease and the insulation resistance will decrease.

Next, the calcined product is pulverized to produce a raw material powder. The average particle size is preferably about 0.5 to 3 μm; if it is too large, bores will increase in the sintered body, and if it is too small, moldability will deteriorate. A high dielectric constant ceramic is obtained by molding such raw material powder into a desired shape and firing it. By using the composition of the present invention, firing can be performed at 1100°C or less, 900 to 10
It can be carried out at a relatively low temperature of about 50°C.

When manufacturing a laminated type element, a binder, a solvent, etc. are added to the raw material powder mentioned above to form a slurry, a green sheet is formed, internal electrodes are printed on this green sheet, and a predetermined number of sheets are laminated and crimped. , manufactured by firing. At this time, since the dielectric material of the present invention can be sintered at a low temperature, an inexpensive material mainly composed of Ag, for example, can be used as the internal electrode material.

As shown, the composition of the present invention can be heated to 1100°C or less,
It can be fired at a relatively low temperature of ~1050°C, with a relative dielectric constant of 2800 (25°C) or higher, a dielectric loss of 2.0% or lower, and a CR value of 2.
000 Ω・F (25℃) or more 500 Ω・
It has stable and excellent electrical characteristics with an insulation resistance of 1012 Ω or more (-30°C to +85°C) at 125°C, and excellent DC bias dependence of less than 40% in IKV/mm. It also has excellent mechanical strength. Furthermore, since it can be sintered at a low temperature of about 900 to 1050°C, it is effective as a material for multilayer capacitors in which internal electrodes are stacked and integrally sintered. In this case, low melting point metals such as Ag-based, Cu-based, Ni-based, M-based, etc., which are relatively cheaper than Pd, Pt, etc., can be used for the internal electrodes, which greatly contributes to cost reduction. Further, even when this composition is used in a minute displacement element that utilizes piezoelectric/electrostrictive effects, it is effective because its characteristics do not fluctuate due to temperature.

Furthermore, since it can be fired at such a low temperature, it is also effective as a material for thick film dielectric pastes to be printed and fired on circuit boards, etc. In this case, even if the oxygen partial pressure is lowered, the basic characteristics will not deteriorate, which is useful.

In such a composition, by containing 1 moρ% or less of manganese, cobalt, nickel, or chromium in terms of oxide, it is possible to reduce dielectric loss, improve sinterability, and obtain good properties. can. However, 1
If the content exceeds 1 Iloρ%, the insulation resistance will decrease and the dielectric loss will increase, so the content should be 1 mob% or less.

Such a ceramic composition of the present invention has a high dielectric constant and good temperature characteristics. In addition, the CR value is large, particularly sufficient even at high temperatures, and has excellent reliability at high temperatures.

(Example) The present invention will be explained in detail below.

Examples 1 to 11 Pb, Ca-Zn 1N as starting materials
Starting materials such as an oxide of b 1Z r sMg are mixed in a ball mill or the like and calcined at 700 to 850°C. Next, this calcined body is crushed with a ball mill, etc., dried, and then a binder is added to granulate it, which is then pressed to give a diameter of 17 mII and a thickness of about 2 mm.
A disk-shaped element body of mm was formed. As balls for mixing and grinding, it is preferable to use balls with high hardness and high toughness, such as partially stabilized zirconia balls, in order to prevent contamination of impurities. This element is 900 to 1050 in the air.
It was sintered at ℃ for 2 hours, silver electrodes were baked on both sides, and various characteristics were measured. Dielectric loss, capacity is I KHz %
I Vrms is a value measured by a digital LCR meter at 25° C., and the dielectric constant was calculated from this value. Moreover, the insulation resistance was calculated from the value measured using an insulation resistance meter after applying a voltage of 100 μ for 2 minutes. In addition, the capacitance temperature change rate is based on the value of 25℃, and -30℃
, expressed as the rate of change at 85°C. The capacitance-resistance product is 25℃
It was determined from (permittivity) x (insulation resistance) x (vacuum permittivity) at 125°C. Insulation resistance measurements were performed in silicone oil to eliminate the effects of atmospheric moisture. The results are shown in Table 1.

(Left below) As is clear from Table 1, the ceramic compositions of the present invention have a low dielectric constant of 2800 or more, a high dielectric constant of 3 or more, and a small dielectric loss of 2.0% or less. 1100℃
Hereinafter, sintering can be performed at a low temperature of 900 to 1050°C. Also,
The insulation resistance is as high as 1012 Ωc or more, and decreases are extremely small even at high temperatures. This means that the CR value is 100 at 125℃.
This can be seen from the fact that it is large, ranging from 0 to 9000 Ω·F. Furthermore, the temperature characteristics of the dielectric constant are also good (-56% at -30 to +85℃).
within).

A reference example will be explained for comparison.

Reference example 1 is a comparative example belonging to the above-mentioned region (3), but the dielectric constant is small and it is not practical.

Reference example 2 is a comparative example belonging to the above-mentioned area (■), but CR
The value becomes small, and the sintering at 900 to 1050°C is insufficient, and the mechanical strength becomes weak.

Reference example 3 is a comparative example belonging to area ■, but the relative permittivity is
Both CR values become small, making it impractical.

Examples 12 to 13 Next, Examples 12 to 13 and Reference Example 4 in Table 2 show examples in which the molar ratio of A/B was changed in the same manner as in Examples 1 to 11. Further, reference examples 5 to 8 in Table 2 show reference examples in which Ba and Sr substitution was performed instead of Ca substitution.

(Left below) As is clear from Table 2, the molar ratio of A/B is 1.00≦
A/B<1. In the case of lQ, particularly good results were obtained in which the dielectric constant was high and the insulation resistance was also high.

Reference example 4 is a case where A/B-0.97 is used, but it can be seen that the relative dielectric constant decreases and the dielectric loss also increases.

Further, Reference Examples 5 to 8 show examples in which A/B was changed when pb was replaced with Ba and Sr instead of Ca. A/B
When is larger than 1, the dielectric constant decreases. This is Ca
The tendency is opposite to that of substitution, and B a s S r s C
This is a new finding that suggests that a cannot be treated in the same way.

Examples 14 to 25 Examples 15 to 2B in Table 3 show examples in which Mn0SCoo and Ni01Cr203 were added to Example 4.

Further, an example in which 2 mo1% of MnO was added is shown as Reference Example 9 in Table 3.

As is clear from Table 3, by containing 1 moρ% or less of manganese, cobalt, nickel, or chromium in the range of the ceramic composition of the present invention in terms of oxide, dielectric loss is reduced. It is possible to improve sinterability and obtain effective properties. However, it can be seen that if it exceeds 1 moρ%, as seen in Reference Example 9, it causes an extreme decrease in the dielectric constant and a decrease in insulation resistance especially at high temperatures, which is not preferable.

Example 27 A disc-shaped element (
A diameter of 17 mm and a thickness of about 2 mm was formed. After degreasing this disk at 500℃, the oxygen partial pressure t, OX100-5
Baked at 900°C for 30 minutes in a nitrogen atmosphere,
Each characteristic of gold electrodes deposited on the amphiboid surfaces was measured in the same manner as in Examples 1 to 12.

x=0.3, y=o, s, z=0.2, a Maro 0.1%
When A/B=1.03 and 1 moJ% of MnO was added, the following properties were obtained for the composition.

Relative permittivity K-”0 8300 Dielectric loss 1.2% Insulation resistance ρ 'C1,5X 10' Ω National CR value
25℃ 11000ΩF Capacitance temperature change rate -80℃ -44%+85℃ -
38% Also, during firing, Cu powder was placed on the alumina substrate and placed in the furnace, but it still had the luster of Cu metal powder after firing.

As described above, according to the present invention, sufficient sintering is possible even in an atmosphere with a low oxygen partial pressure.

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a high dielectric constant ceramic composition that has a high dielectric constant and insulation resistance, can be sintered at low temperatures, and has excellent electrical properties. be able to.

[Brief explanation of drawings]

FIG. 1 is a ternary system composition diagram showing the composition range of the present invention.

Claims (1)

[Claims] (1) General formula x・Pb(Zn_1_/3Nb_2_/_3)O_3-
y・Pb(Mg_1_/_3Nb_2_/_3)O_3
-z・PbZrO_3, a of the ternary diagram with each component as the vertex (x=0.60, y=0.39
, z=0.01) b(x=0.60, y=0.05, z
=0.35) c(x=0.45, y=0.05, z=0
．． 50) d(x=0.01, y=0.49, z=0.5
0) e(x=0.01, y=0.85, z=0.14)
A portion of Pb with a composition within the line connecting each point indicated by f (x = 0.14, y = 0.85, z = 0.01) is 2 to 30 m
A high dielectric constant ceramic composition characterized in that ol% of Ca is substituted. (2) Pb and Ca elements are replaced by A, Zn, Mg, Nb, Z
Let the r element be B, and the chemical formula of these composite compounds is ABO.
3. The high dielectric constant ceramic composition according to claim 1, wherein the molar ratio of A/B is within the range of 1.00≦A/B<1.10. (3) MnO, CoO, NiO, Cr_2O_ at least one of manganese, cobalt, nickel and chromium
The high dielectric constant ceramic composition according to claims 1 and 2, characterized in that the composition contains 1.0 mol% or less in terms of 3%.