JPH0419909A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To make capacitance characteristic to temperature flat over a wide temperature range and reduce dielectric loss by making (Ba1-xPbx)yTiO3 containing alkali metal oxide as impurity contain respectively specified quantity of Nb2O5, Nb2O5, Nd2O3, ZnO, MnO2, Ta2O5 and CaZrO3. CONSTITUTION:100 parts by weight of (Ba1-xPbx)yTiO3 (where x=0.01-0.05, y=0.98-1.02) containing less than 0.04weight% of alkali metal oxide as impurity is made to contain respectively specified quantity of Nb2O5, Nd2O3, ZnO, MnO2, Ta2O5 and CaZrO3. Here, contained Nb2O5 is to be 0.25-3.50 parts by weight, Nd2O3, 0.25-1.50 parts by weight, ZnO, 0.50-2.50 parts by weight, MnO2, 0.06-0.25 parts by weight, Ta2O5, 3.30 parts by weight or less and CaZrO3, less than 6.30 parts by weight. Thereby the capacitance at +25 deg.C is taken as the standard, a capacitance temperature characteristic is flat as staying within + or -15% and dielectric loss is small in a wide temperature range as -55-+150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dielectric ceramic composition, and more particularly to a dielectric ceramic composition used as a material for laminated capacitors and the like.

(Prior Art) Conventionally, as a dielectric ceramic composition having a high dielectric constant and a small change in dielectric constant with temperature, for example, BaTi 03 B
i 203 S n Oz series, BaTiC) + BI
203 TiO2 system, BaTi0. , -Bi203-
ZrO□ system and BaTi0. -PbO3nO□ type.

When these materials are used as a multilayer ceramic capacitor, since they contain Bi2O3 and PbO in their composition,
For the internal electrodes, it was necessary to use a pt-based metal that does not react with Bi2O3 and PbO during sintering. However, this Pt is originally expensive and accounts for a large proportion of the price of the multilayer capacitor, which is a factor in the cost amplifier of the multilayer capacitor. Furthermore, since PT-based metals have a high resistance value, it is necessary to increase the area of the internal electrodes in order to obtain a large capacity. This leads to an increase in the size of the multilayer capacitor itself, which hinders miniaturization.

On the other hand, B i20. , BaTi0. as a pbo-free composition. -Nb205MnO2. The composition of this composition is said to have a high dielectric constant, a particularly small temperature change in the dielectric constant, and a good dielectric loss tangent at high frequencies. Actually, with a certain composition, the dielectric constant ε is 2966 and the dielectric loss tangent tan δ is 65 (
Xi O-'), dielectric constant s>B.

The rate of change TC is 5.5 at -55℃ based on +20℃
%, and +1.2% (-7.3%) characteristics can be obtained at +125°C. Also, IM with this composition)
The dielectric loss tangent tan δ of Iz is 144 (X 10-')
It is said that it is.

However, this composition is intended to reduce the dielectric loss tangent tan δ especially at high frequencies, and the firing temperature is in the range of 1280 to 1400°C, so it is used as a material for multilayer capacitors as mentioned above. Therefore, it cannot be said that it has sufficiently satisfactory characteristics as a material for multilayer capacitors, for reasons such as the inability to use Ag/Pd internal electrodes with a high silver content. be.

Therefore, as a method for solving such problems, ceramic compositions disclosed in Japanese Patent Publication No. 61-20084 and Japanese Patent Application Laid-open No. 59152265 have been proposed.

(Problems to be Solved by the Invention) However, as for the characteristics obtained by the compositions shown in these publications, the temperature characteristics of the capacity are within the temperature range of -55°C to +125°C when +25°C is the standard. Then ±
Although it is very small at 15% or ±7.5%, 125℃
If the ratio exceeds 100%, the rate of change in capacity becomes extremely large, reaching several tens of percent in any composition system.

Therefore, there was a limit to its use at high temperatures.

Therefore, the main object of the present invention is to maintain a flat capacitance temperature characteristic within ±15% over a wide temperature range of -55°C to +150°C when the temperature characteristic of the capacitance is based on +25°C, and to achieve dielectric loss. It is an object of the present invention to provide a dielectric ceramic composition having a small amount of porcelain.

(Means for Solving the Problems) This invention provides (B a , -8Pbx)
TiO+ (where x=0.01~005, y=0
．． 98-1.02) 0.25-3.50 parts by weight of Nb2O5 and 0.25-3.50 parts by weight of Nd2O3 per 100 parts by weight
1.50 parts by weight, 0.50 to 2.50 parts by weight of ZnO'c, 006 to 0.25 parts by weight of MnO2, and Ta2O
, 3.30 parts by weight or less, and CaZr0. This is a dielectric ceramic composition containing 6.30 parts by weight or less of.

(Function) By solidifying PbTi0:+ in BaTiO3, the Curie point of BaTiO3 shifts to the high temperature side.

(Effects of the Invention) According to the present invention, when the capacitance at +25"C is taken as a reference, the capacitance-temperature characteristic is flat within ±15% over a wide temperature range of -55°C to -150°C, and the dielectric loss is It is possible to obtain a dielectric ceramic composition with a small temperature characteristic.Also, despite such a flat temperature characteristic, its dielectric constant is as high as 2000 or more.
It is possible to sinter at temperatures as low as below.

Therefore, conventional multilayer capacitors using dielectric ceramic compositions have a large rate of change in capacitance with temperature, making them unusable in high-temperature environments such as in automobile engine compartments or in heat-generating power supply circuits. can meet the demand for use.

The above objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the following embodiments.

(Example) First, as raw materials, B a C03 with an alkali metal content of 0.001% or less, an alkali metal content of 0.001%
PBO and alkali metal content below 0.001%
The following TiO2 was prepared, and these raw materials were weighed to obtain a P b T i 03 substitution ratio as shown in Table 1 to obtain a weighed product. This weighed product was wet-mixed for 16 hours in a ball mill using zirconia balls to obtain a mixture.

Next, after exploding the dispersion medium in the obtained mixture, 1
000~1100℃ for 2 hours and calcined (BaP
b) A solid solution of TiO2 was obtained.

Then, this solid solution of (B a P b) T i 03 and Nb2O5, Nd2O3, ZnO, MnO2, T
a205 and CaZrO3 were weighed to have the composition ratio shown in the table, mixed for 16 hours in a ball mill using zirconia balls, and then evaporated to dryness to obtain a mixed powder.

Further, the obtained mixed powder was kneaded with a vinyl acetate-based indah, granulated, and then press-molded into a disk shape with a diameter of 10 n2 and a thickness of 11 at a pressure of 2 tOn/cIII to obtain a molded body. Thereafter, this molded body was fired in an electric furnace at the firing temperature shown in Table 2 for 2 hours to obtain porcelain.

Silver paste is coated on both sides of the resulting porcelain and baked to form silver electrodes to form a capacitor, and the dielectric constant (ε) at room temperature is
, dielectric loss (tarz5), volume resistivity (ρ), and rate of change in capacitance with temperature were measured.

In this case, the dielectric constant (ε) and dielectric loss (tan δ) were measured at a temperature of 25° C. and a frequency of 1 k)lz.

In addition, regarding the temperature change rate of capacity (ΔC/Czs), the temperature change rate at -55℃ (8C-5s/C25) and +15℃ are based on the capacity (Cps) at 25℃.
Temperature change rate at 0℃ (8C+so/C25) and =
The absolute value of the value at which the rate of temperature change is maximum between 55°C and +150°C, the so-called maximum rate of change (ΔC/C25
) are shown in Table 2. In addition, the volume resistivity (
ρ) was calculated from the current value 120 seconds after voltage application under the conditions of 25°C, 1kHz, and 500μ, and its logarithm value is shown.

Furthermore, as a comparative example for the content of alkali metal oxides, the results are shown when sample numbers 27 and 28 contain a total of 0.06% by weight of alkali metal oxides. In addition, the sample numbers marked with * in Tables 1 and 2 are
It is outside the scope of this invention.

In addition, although the data shown in Tables 1 and 2 are all results obtained for single-plate capacitors, multilayer capacitors made of the same composition into sheets using the doctor blade method and made into flIi also differ from those of single-plate capacitors. Similar properties are obtained.

Next, in this invention, the solid solution ratio of pbTio:+,
The reason for limiting the range of the (BaPb)/Ti molar ratio and the amount of oxides such as Nb2O5 added will be explained.

That is, like sample number 1, (Bad-XPb
) In y T i O3, if X is 0.01 or less, the capacitance temperature change rate at 150° C. greatly deviates to 115% or less. Conversely, as in sample number 4, X is 0.0
If it is 5 or more, the capacitance temperature change rate at the Curie point is +1
This is because it deviates by 5% or more.

Further, as in sample number 26, when the (Bapb)/Ti molar ratio y is larger than 1.02, the sinterability deteriorates and a dense sintered body cannot be obtained. On the contrary, like sample number 25, (
This is because if the BaPb)/Ti molar ratio y is smaller than 0.98, excess TiOz tends to form a secondary phase and the sinterability also deteriorates.

Next, the reason why the range of the amount of the oxide added as an additive is limited will be explained.

That is, for Nb2O, the range is 025 to 3
．． The reason for setting the value to 50 parts by weight is that within this composition range, the dielectric constant (
(electrostatic capacitance) and insulation resistance increase, but if it is less than 0.25 parts by weight, as in sample number 5, insulation resistance decreases,
As in Sample No. 6, when the amount exceeds 3.50 parts by weight, the dielectric constant decreases.

For N d 203, the range is 0.25 to 150
The sinterability is improved within this composition range, but as in Sample No. 8, the sinterability deteriorates below 0.025 parts by weight, and as in Sample No. 11, the sinterability is reduced to 1.50 parts by weight. If it exceeds parts by weight, the temperature characteristics of the dielectric constant will deteriorate.

The reason for setting the range of ZnO to 0.50-2.50 parts by weight is that within this composition range, sinterability is improved, and 1.
Sintering at temperatures between 200°C and 1240°C becomes possible, and the temperature characteristics of the dielectric constant become flat. However, as in sample number 12, low-temperature sintering becomes impossible at less than 0.50 parts by weight, and sample number 14 As shown in the figure, when the amount exceeds 2.50 parts by weight, a decrease in dielectric constant is observed.

The reason for setting the composition of MnO2 to 0.06 to 0.25 parts by weight is that within this composition range, the dielectric constant (capacitance) and insulation resistance become large, but as in sample number 15, If the amount is less than .06 parts by weight, or if it exceeds 0.25 parts by weight as in sample number 17, the insulation resistance will decrease.

By including Ta and O, the sinterability is improved and the temperature characteristics of the dielectric constant become flat, but as in sample number 20, when the content exceeds 3.30 parts by weight, the dielectric constant tends to decrease. Become.

By including CaZrO3, the dielectric constant increases and the temperature characteristic of the dielectric constant becomes flat, but if it exceeds 6.30 parts by weight as in Sample No. 24, the sinterability decreases.

Furthermore, the alkali metal content was set to 0.04% by weight or less, as in sample numbers 27 and 28.
This is because if it exceeds % by weight, the dielectric constant decreases to 2000 or less.

Claims (1)

[Claims] The content of alkali metal oxide as an impurity is 0.04.
(Ba_1_−_xPb_x)yTiO_ in weight% or less
3 (however, x=0.01~0.05, y=0.98~
1.02) For 100 parts by weight, 0.25 to 3.50 parts by weight of Nb_2O_5, 0.25 to 1.50 parts by weight of Nd_2O_3, 0.50 to 2.50 parts by weight of ZnO, and 0.2 parts by weight of MnO_2. 06 to 0.25 parts by weight, 3.30 parts by weight or less of Ta_2O_5, and 6.30 parts by weight or less of CaZrO_3,
Dielectric porcelain composition.