JP3235343B2 - Dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric porcelain composition, and more particularly to a dielectric porcelain composition used as a material for a laminated ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, a dielectric porcelain composition having a small voltage dependency, a high strength of porcelain and a flat dielectric constant-temperature characteristic has a main component of BaTiO ₃ , which contains a bismuth compound and a rare earth element. A porcelain composition to which is added as an auxiliary component is widely known.

On the other hand, separately from the dielectric ceramic composition having the above composition, BaTiO ₃ is mainly used, and Nb ₂ O ₅ , a rare earth oxide and a transition metal oxide such as Cr, Mn, Fe, Co and Ni are used. It has been reported that a dielectric ceramic composition to which a substance is added as an auxiliary component can also obtain a flat dielectric temperature characteristic while having a high dielectric constant of 3000 or more.

The temperature characteristics of these dielectric ceramic compositions are as follows:
X7R characteristics of EIA standard, that is, -55 ° C to +125
In the temperature range of ° C., the capacitance change rate based on the capacitance at + 25 ° C. was within ± 15%.

[0005]

However, BaT
The dielectric ceramic composition containing iO ₃ as a main component and a bismuth compound added thereto had a low dielectric constant of about 1,000. In addition, when the dielectric constant is increased, the temperature change rate of the capacitance is increased. In addition, when firing at high temperature, Bi at the time of firing
There are problems that ₂ O ₃ evaporates and distortion occurs in the porcelain, the composition ratio changes, and the required electric characteristics and mechanical strength cannot be obtained, or variations occur.

On the other hand, BaTiO ₃ is used as a main component, and Nb ₂ O ₅ , a rare earth oxide and Cr, Mn, Fe, C
A dielectric porcelain composition to which a transition metal oxide such as o or Ni is added as a subcomponent has a dielectric constant of 3000 or more and has flat temperature characteristics. However, the firing temperature of this dielectric porcelain composition was as high as 1200 ° C. or higher.

Further, recent ceramic capacitors tend to be miniaturized. In particular, in a multilayer ceramic capacitor, the thickness of the ceramic dielectric layer is 5 μm to 15 μm in order to reduce the size and increase the capacity.
m. Therefore, it is desired that the dielectric ceramic composition has low voltage dependency.

However, the above-mentioned dielectric ceramic composition having a large dielectric constant has a large voltage dependency, so that it cannot cope with recent thinning, and a small-sized large-capacity ceramic multilayer capacitor cannot be produced. . In addition, the strength of the porcelain is low, so that the porcelain may be broken during mounting.

Therefore, an object of the present invention is to sinter at a temperature of 1160 ° C. or less, and to obtain a high dielectric constant of 1000 or more, while taking into account the capacitance at + 25 ° C.
The temperature change rate of the capacitance is flat within ± 15% over a wide range from 55 ° C. to + 125 ° C., the mechanical strength of the porcelain is high, and the thickness of the dielectric porcelain layer is 5 μm.
Even when the thickness is reduced to 15 μm, at a relatively high rated voltage, in accordance with the RB characteristic standard of JIS C6429,
It is an object of the present invention to provide a dielectric ceramic composition having a small capacitance temperature change rate when a DC voltage of 50% of a rated voltage is applied.

[0010]

In order to achieve the above object, the dielectric porcelain composition of the present invention has the general formula:
(A + b + c + d)｝ BaTiO ₃ + aZnO + b (2
Bi ₂ O ₃ .3ZrO ₂ ) + cTa ₂ O ₅ + dRe ₂ O
₃ (However, Re is La, Pr, Nd, Sm, Dy, E
at least one selected from r, and a, b, c and d are mol%) in a proportion of 97.5 to 99.9.
5% by weight, provided that a, b, c and d in the above general formula are in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4. 5 0.5 ≦ d ≦ 5.5 first subcomponent of SiO ₂ made of glass whose main component is 0.05 to 2.5 wt%, consisting of.

The dielectric porcelain composition of the present invention has a general formula {100- (a + b + c + d)} BaTiO ₃ + aZ
nO + b (2Bi ₂ O ₃ .3ZrO ₂ ) + cTa ₂ O ₅
+ DRe ₂ O ₃ (where Re is La, Pr, Nd, S
at least one selected from m, Dy, and Er;
a, b, c and d are mol%) and the main component is 9
7.0 to 99.94% by weight, provided that a,
b, c and d are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.5 0.5 ≦ d ≦ 5.5 SiO ₂ 0.05 to 2.5% by weight of a first sub-component composed of glass whose main component is a second sub-component composed of at least one selected from oxides of Cr, Mn, Fe, Co and Ni. 0.01 to 0.5% by weight.

[0012]

Industrial Applicability The dielectric porcelain composition according to the present invention comprises:
It can be fired at a low temperature of 1160 ° C. or less, and has a small capacitance temperature change rate (bias TC) when a DC voltage is applied. Therefore, the thickness of the dielectric ceramic can be reduced to 5 μm to 15 μm. As a result, the porcelain multilayer capacitor can be reduced in size and capacity.

Further, since the porcelain has a high mechanical strength, when it is used as a porcelain multilayer capacitor, breakage such as cracking, chipping or the like does not occur when mounted on a substrate. Therefore, accidents such as short-circuit failure and burning due to heat generation can be prevented.

Further, when the capacitance at + 25 ° C. is referenced while having a high dielectric constant of 1000 or more, −
Over a wide temperature range from 55 ° C. to + 125 ° C., the temperature change rate of the capacitance is flat with ± 15% or less, and the temperature is stable. From the above, it can be used over a wide range as a dielectric porcelain for the industrial market or the consumer market.

[0015]

EXAMPLES The dielectric ceramic composition of the present invention is described below.
The embodiment will be described.

First, a method for adjusting the main components of the dielectric ceramic composition will be described. As starting materials, BaTiO ₃ , ZnO, Bi ₂ O ₃ , ZrO ₂ , Ta
₂ O ₅ , Re ₂ O ₃ (where Re is La, Pr, Nd,
Sm, Dy, Er) were prepared. These starting materials were weighed so that the porcelain composition shown in Table 1 was obtained, wet-mixed and crushed with a ball mill for 16 hours, and then dried by evaporation to obtain a mixed powder. The obtained mixed powder was placed in a zirconia box and calcined at 1000 ° C. for 2 hours in a natural atmosphere.
It was ground to pass through a 00 mesh sieve to obtain a raw material powder as a main component of the dielectric ceramic composition.

Next, a method for adjusting the first subcomponent of the dielectric ceramic composition will be described. In this embodiment, the firing temperature is set to 11
8BaO-6Sr as a first subcomponent to be 60 ° C or lower
_{O-6CaO-30Li 2 O-} 50SiO 2 ( mol%)
Was used. As starting materials, BaCO ₃ , SrCO ₃ , CaCO _{3 ,} L
i ₂ O and SiO ₂ were prepared. These starting materials were weighed so as to obtain the above composition, and were weighed with a ball mill.
After wet mixing and crushing for hours, the mixture was evaporated to dryness to obtain a mixed powder. The obtained mixed powder was put into an alumina crucible,
It was left at a temperature of 00 ° C. for 1 hour, and then rapidly cooled to vitrify. This was pulverized so as to pass through a 200-mesh sieve to obtain a raw material powder as a first subcomponent of the dielectric ceramic composition.

The raw material powder of the first subcomponent obtained as described above was added so as to have a weight ratio shown in Table 1 with respect to the raw material powder of the main component.

The second subcomponent is Cr ₂ O ₃ , MnO ₂ , Fe ₂ O ₃ , Co ₂ O ₃ , N ₂
iO was prepared. Then, the main component composition was 93.0.
BaTiO ₃ +1.5 ZnO + 1.5 ( ₂ Bi ₂ O _3.
3ZrO ₂ ) + 2.0Ta ₂ O ₅ + 2.0Nd ₂ O
_{At 3} (mol%), the above-mentioned first subcomponent was added in an amount of 1.0% by weight so that the porcelain composition shown in Table 2 was obtained.

To these were added a polyvinyl butyral-based binder and an organic solvent such as toluene and ethyl alcohol, and the mixture was wet-mixed in a ball mill for 16 hours, and then formed into a sheet by a doctor blade method to obtain a green sheet. The thickness of the obtained green sheet was 19 μm. An internal electrode pattern is formed on this green sheet by Ag.
After printing using a paste of / Pd = 70/30 (% by weight), they are stacked in six layers and thermocompression-bonded together with a dummy sheet.
mm and a 1 mm thick molded body were cut out. Thereafter, this molded body was fired at the firing temperatures shown in Tables 3 and 4 for 2 hours to obtain a fired body. The dielectric thickness after firing was 13 μm.

Then, a silver electrode was baked on the end face of the obtained sintered body, and a dielectric constant (ε), a dielectric loss (tan δ), a TC and a bias TC at room temperature were measured as a measurement sample (multilayer capacitor). .

In this case, the dielectric constant (ε) and the dielectric loss (tan δ) were measured at a temperature of 25 ° C., 1 kHz, and 1 Vrms. TC is the absolute value of the value at which the rate of temperature change is maximum between −55 ° C. and + 125 ° C., based on the capacitance at 25 ° C., so-called maximum rate of change (| △ C /
C | _max ). As for the bias TC,
The capacitance was measured while a DC voltage of 25 V was superimposed on the measurement sample in the above temperature range.
The maximum rate of change (△
C _maxB ) was determined.

Further, the bending strength of the porcelain was measured by three-point bending. That is, first, the raw materials having the respective compositions shown in Tables 1 and 2 were prepared by 35 mm in length, 7 mm in width, and 1.2 m in thickness.
m to obtain a molded body. After that, it was fired at the firing temperatures shown in Tables 3 and 4 for 2 hours to obtain strip-shaped porcelain. Thereafter, the flexural strength was measured for 20 samples of each composition, and the average was taken as the flexural strength of each composition.

For each of the above tests, the results for the compositions in Table 1 are shown in Table 3, and the results for the compositions in Table 2 are shown in Table 4.

In the present invention, the reason why the ranges of the main component amount, the first subcomponent amount, and the second subcomponent amount are limited will be described.

First, the reason for limiting the range of the main component composition will be described. As shown in Sample No. 9 in Table 1, when the value of a, that is, ZnO is less than 0.5 mol%, the TC changes by more than 15%, and the bending strength is also 1500 k.
g / cm ² or less, which is not preferable.
On the other hand, as shown in Sample No. 10, when the value of a exceeds 4.5 mol%, the bias TC changes more than −40%, and the TC also exceeds 15%, which is not preferable.

As shown in Sample No. 11 in Table 1, when the value of b, ie, 2Bi ₂ O ₃ .3ZrO _2, is less than 0.5 mol%, the TC changes by more than 15%, and the bending strength also becomes 1500 kg / The value is undesirably a low value of not more than cm ² . On the other hand, as shown in Sample No. 12, when the value of b exceeds 4.5 mol%, ε becomes less than 1000, which is not preferable.

As shown in Sample No. 13 in Table 1, the value of c, that is, Ta ₂ O ₅ is less than 0.5 mol%, or as shown in Sample No. 14, the value of c is 4.5 mol%. Is not preferable because TC exceeds 15%.

As shown in Sample No. 15 in Table 1, the value of d, ie, Re ₂ O _3, was less than 0.5 mol%, or as shown in Sample No. 16, the value of d was 5.5 mol%. %
Exceeds TC, the TC changes by more than 15%.
The bias TC also changes more than -40%, which is not preferable.

Next, the reason for limiting the range of the first subcomponent will be described. As shown in Sample No. 17 in Table 1, if the amount of the first subcomponent is less than 0.05% by weight, the firing temperature exceeds 1160 ° C., which is not preferable. On the other hand, as shown in Sample No. 20, when the addition amount of the first subcomponent exceeds 2.5% by weight, ε is less than 1,000, which is not preferable.

Next, the reason for limiting the second subcomponent will be described. As shown in Sample No. 30 in Table 2, when the added amount of the second subcomponent exceeds 0.5% by weight, tan δ becomes 2.%.
It is not preferable because it becomes a large value exceeding 5%.

In the above embodiment, BaO—SrO—CaO—Li ₂ O—SiO ₂ -based oxide glass was used as an auxiliary component. However, as a sintering aid for lowering the firing temperature to 1160 ° C. or less, is not limited to this, for example, _{BaO-Li 2 O-B 2} O 3 - may be an oxide glass containing boron such as SiO ₂ system, a system containing SiO ₂ -B ₄ C such non-oxide There may be.

In the above embodiment, the first subcomponent prepared in advance at a predetermined composition ratio, heat-treated at a high temperature, melted, pulverized and vitrified was added to the main component of the porcelain composition. . However, as a method for adding the main component and the first subcomponent, a method in which a starting material is reformed by heating it to such an extent that it is not melted by mixing it in a predetermined ratio in advance, such as Bi ₄ Zr ₃ O ₁₂ , Alternatively, a solid solution may be added, or each constituent element of the first subcomponent may be individually added to the main component in an arbitrary compound state such as a metal alkoxide.

In the above embodiment, the second subcomponent was also added in the form of an oxide from the beginning. However, as a starting material at the time of preparing the raw material, carbonate such as each element was used in the stage of calcination and firing. An oxide can be used.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

Continuation of the front page (56) References JP-A-7-315921 (JP, A) JP-A-52-92400 (JP, A) JP-A-7-73734 (JP, A) JP-A-7-37428 (JP) JP-A-7-37427 (JP, A) JP-A-7-37426 (JP, A) JP-A-5-178660 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C04B 35/42-35/50 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. The following general formula: {100− (a + b + c + d)} BaTiO ₃ + aZn
O + b (2Bi ₂ O ₃ .3ZrO ₂ ) + cTa ₂ O ₅ +
dRe ₂ O ₃ (where Re is La, Pr, Nd, Sm, Dy, Er
Wherein at least one member selected from the group consisting of a, b, c and d is mol%) is 97.5 to 99.95.
%, Wherein a, b, c and d in the above general formulas are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.5 0.5 ≦ d ≦ 5.5 A dielectric ceramic composition comprising 0.05 to 2.5% by weight of a first subcomponent made of glass containing SiO ₂ as a main component. 2. The following general formula: {100− (a + b + c + d)} BaTiO ₃ + aZn
O + b (2Bi ₂ O ₃ .3ZrO ₂ ) + cTa ₂ O ₅ +
dRe ₂ O ₃ (where Re is La, Pr, Nd, Sm, Dy, Er
Wherein at least one selected from the group consisting of a, b, c and d is mol%) is 97.0 to 99.94.
%, Wherein a, b, c and d in the above general formulas are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.5 0.5 ≦ d ≦ 5.5 The first subcomponent composed of glass containing SiO ₂ as a main component is selected from 0.05 to 2.5% by weight and oxides of Cr, Mn, Fe, Co and Ni. A dielectric ceramic composition comprising 0.01 to 0.5% by weight of at least one second subcomponent.