JP2616220B2 - Porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a porcelain composition, and more particularly to a porcelain composition having a high dielectric constant, a high insulation resistance, a small dielectric loss, and which can be sintered at a temperature of 1000 ° C. or lower. It is about.

[Prior art] Conventionally, barium titanate [BaTiO ₃ ] is well known as a high dielectric constant porcelain composition, and calcium titanate [CaTiO ₃ ], lead titanate [PbTiO ₃ ], etc. are added. The temperature characteristics are improved by replacement, but since the sintering temperature is as high as 1300 ° C or more, when used for multilayer ceramic capacitors, only expensive noble metals such as platinum and palladium are used for the internal electrodes. Not available.

[Problem to be Solved by the Invention] When a material having a small temperature change rate is realized by a conventional material, the obtained dielectric constant is only about 2000 at most, and is too small as a material for a capacitor. In recent years, a lead-based composite perovskite compound has been reported as a material which is sintered at a low temperature and has a high dielectric constant. For example, lead magnesium / niobate [Pb (Mg _1/3 Nb _2/3 ) O ₃ ], lead titanate [PbTi
It has been reported that a three-component composition comprising O ₃ ] and nickel nickel niobate [Pb (Ni _1/3 Nb _2/3 ) O ₃ ] can have a dielectric constant as high as 20,000 or more at room temperature. Have been. However, this three-component system has a problem that the temperature change of the dielectric constant is large and the capacitance decreases greatly when a DC bias is applied. Therefore, the range of use has been practically limited.

An object of the present invention is to provide a porcelain composition which improves the temperature characteristics of the dielectric constant of the above composition and reduces the capacity when applying a DC bias as little as possible.

[Means for Solving the Problems] The present invention relates to a magnesium / lead tungstate [Pb (Mg
_1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ] and zinc / niobate lead [Pb (Zn _1/3 Nb _2/3 ) O ₃ ]. (Mg _1/2 W _1/2 ) O ₃ ] _x [PbTiO ₃ ] _y [Pb (Zn
When expressed as _1/3 Nb _2/3 ) O ₃ ] _z (where x + y + z = 1.0), the following composition points (x = 0.40, y = 0.20, z = 0.40) (x = 0.40, y = 0.50, z = 0.10) (x = 0.20, y = 0.20, z = 0.60) and within a composition range surrounded by these three points, and x ≠ 2z / 3. It is a porcelain composition.

The three-component composition diagram representing the composition range in the present invention is shown in FIG. The composition range included in the present invention is a range indicated by oblique lines in the figure (however, limited to a composition satisfying x ≠ 2z / 3) and a boundary thereof. In JP-B-58-074569, [Pb (Mg _1/2 W _1/2 ) O ₃ ]-[PbTiO ₃ ]-[Pb (Zn _{1 /} ) is the same composition system as the porcelain composition of the present invention. ₃ N
b _2/3 ) O ₃ ] has been reported, but this composition system is a region indicated by dots in FIG. The present invention relates to Japanese Patent Publication No. 58-074569.
This is a porcelain composition improved in that the dielectric constant is higher than that of the porcelain composition in the composition range reported in Japanese Patent Publication No.

[Examples] Hereinafter, examples of the present invention will be described in detail.

Example 1 Lead oxide (PbO), tungsten oxide (W
O ₃ ), magnesium oxide (MgO), niobium oxide (Nb
₂ O ₅ ), zinc oxide (ZnO), and titanium oxide (TiO ₂ ) were weighed so as to have the compounding ratios shown in Table 1.

Next, the weighed materials are wet-mixed in a ball mill, then calcined at 800 to 850 ° C., the powder is pulverized in a ball mill, filtered, dried, put in an organic binder, sized, and pressed. Approximately 16mm, thickness of about 2mm two discs, diameter of about 1
A cylinder having a thickness of 6 mm and a thickness of about 10 mm was produced.

Next, the sample in the composition range of the present invention was fired at a temperature of 900 to 1000 ° C. for 1 hour. Silver electrodes are baked at 600 ° C on the upper and lower surfaces of the baked disk, and the frequency is 1 kHz with a digital LCR meter.
The capacitance and the dielectric loss were measured at a voltage of 1 Vr.ms and room temperature, and the permittivity and the rate of change of the permittivity with respect to the temperature were obtained. 50 more
The current value when a DC voltage of V was applied for one minute was measured with an insulation resistance meter to determine the specific resistance of the sample.

The main component of the porcelain thus obtained [Pb (Mg _1/2 W
_{1/2) O 3] x [PbTiO} 3] y [Pb (Zn 1/3 Nb 2/3) O 3] mixing ratio of _z x, y, z and dielectric constant at room temperature, the dielectric loss and -30 ° C., Table 1 shows the rate of change of the dielectric constant at 85 ° C. (based on the dielectric constant at 20 ° C.).

As is clear from Table 1, [Pb (Mg _1/2 W _1/2 )
The porcelain composition in the composition range of the present invention in the O ₃ ]-[PbTiO ₃ ]-[Pb (Zn _1/3 Nb _2/3 ) O ₃ ] ternary composition has high dielectric constant and specific resistance. It has a small change in dielectric constant with temperature, and can satisfy the Y5U characteristics and the Y5T characteristics of the EIA standard. Further, the porcelain composition of the present invention is 1000
Since sintering can be performed at a low temperature of not more than ℃, an inexpensive silver / palladium alloy can be used for the internal electrodes of the multilayer ceramic capacitor.

Example 2 [Pb (Mg _1/2 W _1/2 ) O ₃ ] _x [PbTiO ₃ ] _y [Pb (Zn _1/3 N
b _2/3 ) O ₃ ] _z (where x + y + z = 1.0) In a three-component porcelain composition, (x, y, z) = (0.40,0.30,0.30),
(0.30, 0.20, 0.50) Lead oxide, magnesium oxide, tungsten oxide, titanium oxide, zinc oxide, and niobium oxide were accurately weighed, and the dielectric material was obtained in the same manner as described in Example 1. A powder was synthesized.

The obtained dielectric powder was dispersed in an organic solvent, kneaded with an organic binder to prepare a slurry, and the slurry was formed into a film having a thickness of 40 μm using a normal doctor blade method.
Further, the internal electrode paste was printed by a normal screen printing method, punched into a predetermined shape, and then laminated and hot-pressed, and the obtained laminate was cut into a predetermined shape to produce a capacitor green chip. The green chip was subjected to binder removal and firing under a predetermined temperature condition, and an external electrode was attached and formed using a silver paste.

Use a digital LCR meter while applying a current bias of 0 to 50 V to the capacitor with a digital multimeter.
The capacity of the capacitor was measured at room temperature with an alternating current of 1 Hz and KHz. The measurement results are shown in FIG. In the figure, A is (x, y,
z) = (0.30,0.20,0.50) composition, B is (x, y, z) =
(0.40, 0.30, 0.30).

Comparative Example [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] _x [PbTiO ₃ ] _y [Pb (Ni _1/3 N
b _2/3) O _{3] 3} represented by _z (provided that x + y + z = 1.0)
In the component-based porcelain composition, x = 0.20, y = 0.20, z = 0.60
Using such a composition, a capacitor was produced by the method shown in Example 2, and the capacitance when a DC bias was applied was measured in the same manner. FIG. 2 shows the measurement results together with the results of Example 2.

As shown in FIG. 2, the capacitor using the porcelain composition having the composition shown in the comparative example has a remarkable decrease in capacity when a DC bias is applied, whereas the capacitor using the porcelain composition of the present invention has a direct current. It can be seen that the capacitance decrease during bias application is small.

In addition, in a composition outside the range of the present invention, the Curie point deviates too much from the room temperature to the high temperature side or the low temperature side to deteriorate the temperature characteristics of the capacitor, increase the dielectric loss, or reduce the specific resistance. Therefore, it is not suitable as a porcelain composition for capacitors.

[Effect of the Invention] The porcelain composition of the present invention has a high dielectric constant, a small change in the dielectric constant with temperature, and a small decrease in capacity when a DC bias is applied. In addition, it has a good dielectric loss value and can be sintered at a low temperature. Therefore, a multilayer ceramic capacitor having excellent temperature characteristics can be manufactured, and inexpensive silver-palladium can be used for the internal electrodes of the capacitor.

Furthermore, since the capacity decrease when DC bias is applied is small,
It can be used as a porcelain composition for a multilayer ceramic capacitor used under conditions where a DC bias is applied, such as a switching electrode.

[Brief description of the drawings]

FIG. 1 is a three-component composition diagram showing the composition range of the present invention, and FIG. 2 is a graph showing an example of a multilayer ceramic capacitor using the composition of the present invention. FIG. 5 is a diagram plotted against the DC electric field intensity of FIG.

Claims (1)

(57) [Claims] Claims: 1. Magnesium lead tungstate [Pb (Mg
_1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ] and zinc / niobate lead [Pb (Zn _1/3 Nb _2/3 ) O ₃ ]. (Mg _1/2 W _1/2 ) O ₃ ] _x [PbTiO ₃ ] _y [Pb (Zn
When expressed as _1/3 Nb _2/3 ) O ₃ ] _z (where x + y + z = 1.0), the following composition points (x = 0.40, y = 0.20, z = 0.40) (x = 0.40, y = 0.50, z = 0.10) (x = 0.20, y = 0.20, z = 0.60) and within a composition range surrounded by these three points, and x ≠ 2z / 3. Porcelain composition.