JPH0397662A - Dielectric porcelain composition having high dielectric constant and production thereof - Google Patents

Abstract

PURPOSE:To obtain a dielectric porcelain compsn. having a high dielectric constant, a high relative dielectric constant, high insulation resistance and high deflective strength by mixing BaTiO3 with ZnNb2O6, Nd2O3 and MnO in a prescribed ratio, pulverizing the mixture to a proper particle size and sintering the resulting powder. CONSTITUTION:96-99wt.% BaTiO3 is mixed with 0.5-3.75wt.% ZnNb2O6, 0.1-1.25wt.% Nd2O3 and <=0.2wt.% MnO. This mixture is pulverized to 0.1-1.3mum particle size and the resulting powder is sintered at a prescribed temp. to obtain a dielectric porcelain compsn. having a high dielectric constant. The dielectric constant of this porcelain compsn. hardly undergoes a change over a wide temp. range, the dielectric loss is small, the relative dielectric constant is as high as about 2,000-4,500 and the insulation resistance is as high as 2X10<11>-7X10<11> OMEGA. Since the compsn. does not contain Bi liable to react with Pd, in the case where the compsn. is used as the dielectric substance of a laminate type capacitor, etc., an electrode made of only Pd can be used as an internal electrode.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a high dielectric constant dielectric ceramic composition, which has a small change in dielectric constant over a wide temperature range, low dielectric loss, and low element strength. This invention relates to a strong and excellent high dielectric constant dielectric ceramic composition.

? Conventional technology) Barium titanate (B a Ti O
3) Add a bismuth compound, such as BizOi/SnO■
or Bi4Ti+: +O+3, Bi. 03・ZrO. and T
It has been known to add azOs, NbzO5, etc. to reduce the rate of change in temperature characteristics.

Also, (B a- S r) T i O 3 and B a
The Curie point of B a T f O z was lowered to around room temperature by forming it into a solid solution such as (T i S n ) 0 3 .

Furthermore, recent ceramic capacitors are often required to be small in size, large in capacity, and have excellent high frequency characteristics.

However, the dielectric ceramic compositions described above do not yet satisfy this requirement.

That is, it is advantageous for small and large-capacity devices to have a large dielectric constant, but generally speaking, as the dielectric constant increases, its change due to temperature increases, so there is a natural limit to increasing the dielectric constant.

In order to solve these difficulties, a method is known in which the thickness of the dielectric is reduced to increase the capacitance. This involves forming a dielectric into a green sheet with a thickness of about 0.1 to 0.2 nm, punching it into a predetermined shape, and then burning it. and,
A laminated ceramic capacitor having a predetermined large capacity is obtained by stacking the ceramic composition formed into a 'R film and the electrode in multiple layers.

[Problem to be solved by the invention]

However, if a bismuth compound is included in the composition of the thinned porcelain composition, the bismuth will evaporate during the firing process, causing bends and holes in the porcelain composition, resulting in the formation of dense porcelain compositions. was difficult to obtain.

As a result, the strength of the ceramic body (the inherent strength of the ceramic body) was also low.

Furthermore, after the firing, a bismuth atmosphere remains in the firing furnace, the lid, the bedding powder, etc., which has a negative effect on the firing process of other porcelain compositions.

Furthermore, if a multilayer ceramic capacitor is made using barium titanate containing bismuth as a dielectric, the palladium or platinum-palladium alloy that is the internal electrode reacts with the bismuth dielectric and loses its function as an electrode. This requires the use of expensive platinum, which increases the cost of multilayer ceramic capacitors.

Moreover, it is a cause for concern in terms of dielectric strength and voltage, and has the problem of large dielectric loss at high frequencies.

Therefore, the objects of the present invention are to have a structure with little change in dielectric constant over a wide temperature range, low dielectric loss, and strong elemental strength.
The object of the present invention is to provide a high dielectric constant ceramic composition that does not contain bismuth in its composition.

[Means to solve the problem]

In order to achieve the above object, the inventor has conducted extensive research and has
As the main component, 96.00-99.00% debt converted to BaTiOt
0.50 to 3.75% by weight in terms of ZnNbzO, 0.10 to 1 in terms of NdzOz
．． It has been found that a dielectric ceramic composition containing 25% by weight meets the above objective. In addition, in the above main component, O weight % to 0.2 weight % MnO
It has been found that the properties are further improved by containing.

Furthermore, by setting the particle size of the raw material powder before main firing for shaping this dielectric ceramic composition to 0.1 to 1.3 μm, the sintered body became dense and the bending strength was significantly improved.

As a result, in conventional multilayer capacitors, the thickness of the element body has been reduced to 2
Although mechanical strength was weak when the layer was made as thin as about 0 to 50 μm, these drawbacks can be improved.

In addition, when the Mi value of the dielectric ceramic composition of the present invention is expressed in the form of a simple oxide, it is as follows.

Barium oxide (Bad) 63.21-65.08
Weight% titanium oxide (T i O z) 32.8
4 to 33.92% zinc oxide (ZnO) 0
．． 12 ~0.88% Niobium Pentoxide (NbzOs)
0.38-2.87% by weight neodymium oxide (N
az○. ) 0.10 to 1.25% by weight [Function] By using the dielectric porcelain M product of the present invention,
It has a high dielectric constant of about 2000 to 4500 at room temperature, a small dielectric loss (tan δ) of 1.2% or less, and temperature change in dielectric constant is B as specified by JIS.
characteristics (within a temperature range of -25°C to +85°C, the change in dielectric constant is within ±10% with respect to 20°C) and the X7R characteristics (-55
It is possible to obtain a high-permittivity dielectric porcelain assembly with excellent properties that satisfies both characteristics: change in dielectric constant is within ±15% with respect to 25°C within a temperature range of ℃ to +125°C. Ta.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a ternary composition diagram of the high-permittivity dielectric porcelain assembly of the present invention, and FIG. 2 is an explanatory diagram of the manufacturing process of the high-permittivity dielectric porcelain Mi article of the present invention.

As starting materials, barium carbonate (BaCO:+) and titanium oxide (T i O t ) are prepared in a molar ratio of 1:1 (see FIG. 2 I).

The prepared starting materials are subjected to dehydration and drying treatment (see Figure 2 ■).

Next, these raw materials are temporarily shaped and calcined at 1000 to 1200°C for 2 hours to carry out a chemical reaction and form BaTi○,
(See Figure 2 ■).

This BaTiOs is pulverized using an atomizer or the like (see Figure 2).

Ground BaTiO. , Nbzos, Z n O XN
Weigh, add, and mix the powders of each raw material of d z O, and M n CO 3 so that the 'lJl weight after burning is as shown in Table 1, and the 50% particle size is 0.1~ Grind and dry to a powder of 1.3 μm (see Figure 2 V).

Add an appropriate amount of PVA binder to this, approximately 3 tons/cI.
Shaped with 12 degrees of pressure, diameter 16.5n, thickness approximately 0
．． It has a 6 mm disc-shaped proboscis. Next, this kimono is stabilized by heating at about 1,240 to 1,340°C for 2 hours to carry out main firing (see Figure 2 (■)).

Silver electrodes are baked on both ends of the obtained porcelain composition body to form a capacitor (see Figure 2).

The electrical characteristics of these capacitors are determined by the frequency IKII2,
Measurement is performed at a room temperature of 20°C (see Figure 2 ■).

Margin below The results of each measurement are shown in Table 1.

In addition, materials No. 4, 5, 6-5, 6-6 in Table 1,
6-11, 11, 12, and 13 are not included in the examples of the present invention.

As is clear from Table 1, the dielectric ceramic composition of the present invention has a BaTiO* ratio of 96.00 to 99. OQ weight%, ZnN
bzob: 0.50-3.75 heavy view%, Nd203
:0.10~l. The main component is 25% by weight, and if necessary, 0 to 0.2% by weight of MnO is contained based on the main component. FIG. 1 shows the composition of the above-mentioned main components, and the ternary components included in the area surrounded by straight lines connecting A, BSC, D, E, and F in the figure are the composition of the present invention. The number of each point in Figure 1 matches the document number in Table 1. Further, by adjusting the particle size of the raw material powder forming the dielectric ceramic composition of the present invention before main firing to 0.1-1.3 μm, the sintered body becomes dense.

Next, the reason for limiting the Mi range of the present invention will be explained with reference to Table 1.

When BaTi○, is less than 96.00% by weight, the relative dielectric constant (ε
S) becomes smaller (see Table 1 Materials Nos. 012 and 13),
If it exceeds 99.00% by weight, the relative dielectric constant becomes high, but the temperature characteristics of the dielectric constant (TC) deteriorate, tan δ increases, and sinterability deteriorates (see Table 1, Material No. 1).

Also, ZnNb. 0. is less than 0.50% by weight, T-C
, Lan δ increases and sinterability deteriorates (see Table 1 Material No. 1), and when the amount exceeds 3.75 iU, εS decreases and TC increases (see Table 1 Material No. 3).

Furthermore, if Nd203 is less than 0.10%, the bending strength will be weak and the sinterability will be poor (see Table 1, Material No. 4).
．． If it exceeds 25% by weight, T-C becomes large and practicality becomes poor (see Materials Nos. 5 and 11 in Table 1).

Although practically satisfactory properties can be obtained even without the addition of MnO, sinterability and tan δ are improved by adding up to 0.20% (Material No. 6-2 in Table 1).
, 6-3, 6-4). However, if it exceeds 0.20% by weight, the sintering properties will be poor and a dense porcelain composition will not be obtained, the bending strength will be weak, the insulation resistance (rR) will also decrease, and the T-C will increase, making it impractical for practical use. (Table 1 Material N
(See o6-5).

In addition, if the particle diameter of the raw material powder forming the dielectric ceramic U-Kaimono of the present invention before main firing is less than 0.10 μm, εS becomes small, and tan δ and T-C become large (Table 1 Material No.
6-6), if it exceeds 1.30 pm, the sinterability deteriorates and the bending strength also becomes weak (see Material No. 6-11 in Table 1).

〔Effect of the invention〕

The dielectric ceramic composition of the present invention has a dielectric constant of about 2000 to 4.
It shows a high value of 500, and the insulation resistance is 2 x 10" to 7 x 1.
It has a high resistance of 0''Ω and a strong bending strength.

The temperature change characteristics of capacitance are B characteristics and E specified by JTS.
It has extremely excellent characteristics that satisfy the X7R characteristics specified by IAJ.

Furthermore, since the assembly does not contain bismuth, which easily reacts with palladium, when the dielectric ceramic assembly of the present invention is used as a dielectric to manufacture a capacitive element such as a multilayer capacitor, palladium alone can be used as the internal electrode. It becomes possible to use it.

Therefore, there is no need to use expensive platinum or platinum-palladium alloy, and the cost of the product can be significantly reduced, resulting in immeasurable industrial benefits.

[Brief explanation of drawings]

FIG. 1 is a diagram of a ternary set of the dielectric ceramic composition of the present invention, and FIG. 2 is a diagram of the manufacturing process of the dielectric ceramic composition of the present invention.

Claims (3)

[Claims] (1) As a main component, 96.00 to 99.00% by weight in terms of BaTiO_3, 0.50 to 3.75% by weight in terms of ZnNb_2O_6, and 0.10 to 1.25% by weight in terms of Nd_2O_3. A high dielectric constant dielectric ceramic composition comprising: (2) The high dielectric constant according to claim (1), wherein the main component contains 0.2% by weight or less (excluding 0% by weight) as an additive in terms of MnO. Dielectric porcelain composition. (3) BaTiO_3, ZnNb_2O_6, Nd_2
Claim (1) characterized in that after mixing O_3 and MnO in a predetermined ratio, the powder is pulverized so that the powder particle size before main firing is in the range of 0.1 to 1.3 μm, and then fired at a predetermined temperature.
) A method for producing a high dielectric constant ceramic composition according to (2).