JPH04108655A - Porcelain composition - Google Patents

Abstract

PURPOSE:To improve the temp. dependency of dielectric constant and stability to a firing atmosphere by substituting Ba or Sr ions for a specified amt. of Pb ions in a specified compsn. consisting of magnesium lead tungstate, lead titanate and nickel lead niobate. CONSTITUTION:When a compsn. consisting of Pb(Mg1/2W1/2)O3, PbTiO3 and Pb(Ni1/3Nb2/3)O3 is represented by a formula >>Pb(Mg1/2W1/2)O3]x>>PbTiO3]y>>Pb(Ni1/3Nb2/3)O3]z (where x+y+z=1.0), a compsn. present on a line connecting points (a) (x=0.693, y=0.297, z=0.01), (b) (x=0.495, y=0.495, z=0.01), (c) (x=0.195, y=0.455, z=0.35), (d) (x=0.10, y=0.40, z=0.50) and (e) (x=0.06, y=0.24, z=0.70) or within the range defined by the five points is used and Ba<2+> and/or Sr<2+> is substd. for 0.5-30mol% of Pb<2+> in the used compsn. to obtain the porcelain compsn.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a porcelain composition, particularly a porcelain composition that has high dielectric constant, high insulation resistance, low dielectric loss, and can be sintered at a temperature of 1050'C or less. It is about things.

[Prior Art] Conventionally, barium titanate [BaTj03] system is well known as a high dielectric constant ceramic composition, calcium titanate [CaT i 03 ], lead titanate [PbT
Although the temperature characteristics are improved by adding or substituting substances such as iO3, the sintering temperature is as high as 1300°C or higher, so when used in multilayer ceramic capacitors,
Platinum for internal electrodes.

Only expensive precious metals such as palladium could be used.

[Problem to be solved by the invention] When a material with a small temperature change rate is realized using conventional materials,
The dielectric constant obtained is only about 2000 at most, which is too small to be used as a material for capacitors.

In recent years, lead-based composite perovskite compounds have been reported as materials that sinter at low temperatures and have a high dielectric constant. Among them, in JP-A-58-161972, magnesium lead tungstate [Pb (MC11/2 W1/
2 > 03, lead titanate [PbTiO3] and nickel lead niobate [Pb(N i 1/3 N b2
It has been reported that a three-component composition consisting of 03] can have a dielectric constant as high as 10,000 or more. However, this three-component system has a problem in that the change in dielectric constant with temperature is relatively large.

Furthermore, dielectric materials using lead-based composite perovskite compounds have the problem of being greatly affected by the firing atmosphere due to the high vapor pressure of lead oxide. Therefore, stable characteristics cannot be obtained when firing a multilayer ceramic capacitor unless the firing atmosphere is controlled.

An object of the present invention is to provide a ceramic composition that improves the temperature characteristics of the dielectric constant of the above-mentioned composition and has high stability in a firing atmosphere.

[Means for Solving the Problems] The present invention provides magnesium lead tungstate [Pb (
MC11/2 W1/2) 03], Titanium W1
Lead [PbT i 03 ]; 13 and nickel/niobium! l Lead [Pb (N i 1/3 Nb2/3 >
[P b (Mg1/
2 W172 ) 03 ] x [PbTiO3,
[Pb (N i 1/3 Nb 273 )03
] (However, when expressed as x + y + z = 1.0 >, the following composition point, (x = 0.893. y = Q, 297. z = 0
．． 01>-a(x=0.495.y=0.49
5. z = 0.01 house - b (x = 0.195. y
= 0.455. z=0.35)-c(x=0
．． 10, y=0.40, z=0.50>
−d(x=0.06, y=0.24, z=
0.70) ・In the main component composition on the line connecting e and within the composition range surrounded by these five points, lead ion (Pb2+) is replaced by at least one of barium ion (Ba2+) and strontium ion (Sr''). This is a ceramic composition characterized by 0.5 to 30 mo of 1% substitution with different types of ions.

A three-component composition diagram showing the main component composition range in the present invention is shown in FIG. In the figure, (a) to (e) represent each composition point, and the composition range included in the present invention is the shaded range in the figure,
And borderline.

[Example] Examples of the present invention will be described in detail below.

Examples 1-20. Comparative Examples 1 to 10 Lead oxide (PbO), tungsten oxide (WO3), magnesium oxide (MgO), niobium oxide (Nb205), nickel oxide (NiO), titanium oxide (Ti02), strontium carbonate (SrCO3) as starting materials
and barium carbonate (<BaCO3) were used, and each was weighed so as to have the compounding ratio shown in Table 1.

Next, the weighed materials were wet-mixed in a ball mill, then calcined at 800-850°C, and this powder was ground in a ball mill, filtered, and dried. After adding an organic binder and sizing, the powder was pressed. Approximately 161!1I11, two disks approximately 2m thick and approximately 16 in diameter! II! ! I, thickness approximately 10IM4
A cylinder was made.

Next, for samples in the composition range of the present invention, 950 to 105
Firing was performed at a temperature of 0° C. for 1 hour. Silver electrodes were baked on the top and bottom surfaces of the fired disk at 600°C, and the capacitance and dielectric loss were measured using a digital LCR meter at a frequency of 1 kHz, a voltage of 1 Vr, tS, and room temperature, and the dielectric constant and the rate of change of the dielectric constant with respect to temperature were determined. I asked for it.

The main component of the porcelain thus obtained [Pb(Mg1/
2 W172 ) Oa ] [PbT i Oa
].

× [Pb (N i 173 N b2/3 ) 03
] Mixing ratio X of 2.

y, z and Sr'', Ba2+ (7) substitution amount, dielectric constant (ε), dielectric loss (tan δ) and -3 at room temperature.
Table 1 shows the rate of change in dielectric constant at 0°C and 85°C (based on the dielectric constant at 20°C).

As is clear from Table 1, [Pb (Mg1/2W1/2)03] [PbTiO3]-
[Pb (Ni1/3 Nb2/3 >03] Porcelain composition of the present invention in which 0.5 to 30 mo 1% of Pb is replaced by at least one ion of Sr2+, Ba2, and at least one type of 2+ in the three-component composition. The ceramic composition of the present invention maintains a high dielectric constant, has a small change in dielectric constant due to temperature, and can satisfy the Y5T characteristics of the EIA standard.Furthermore, the porcelain composition of the present invention can be used at a low temperature of 1050°C or less. Because it can be sintered,
An inexpensive silver-palladium alloy can be used for the internal electrodes of multilayer ceramic capacitors.

(Left below) Example 21 E P b (M Q 1/2 W 1/2)
03 Ko. [PbT i03 Koy [Pb
(N 1173 Nb273 >03 ]Z
In the main composition expressed by the composition formula, x=0.
3゜Pb2+ is S with y=0.4 and z=0.3
A composition in which 15 mo1% of r2+T was substituted was selected, and dielectric powder was synthesized by the method shown in Examples 1 to 20. The obtained dielectric powder was dispersed in an organic solvent and kneaded with an organic binder to prepare a slurry, and the slurry was formed into a film using a conventional doctor blade method. Furthermore, after printing the internal electrode paste using the normal screen printing method and punching it out,
The laminate obtained by laminating and hot pressing was cut into a predetermined shape to produce a capacitor green chip. After removing the binder from the green chip using a predetermined temperature cycle, it was fired using a predetermined method.

A schematic diagram of the firing method at this time is shown in FIG. Figure 2 (a
) shows a method in which 50 capacitor green chips 5 are placed on a magnesia setter 4 and fired in a closed atmosphere in a magnesia sagger made of a lower lid 1, a frame 2, and an upper lid 3, and is referred to as method 1. . FIG. 2(b) shows a method in which 150 chips 5 are placed on a magnesia setter 4 and fired in the same manner as method @1, which is referred to as method 2. Fig. 2 (C) shows that the magnesia setter 4 has lead zirconate (
This is method 3, in which PbZI''03) powder is spread, 50 chips 5 are placed on top of it, and fired in an open atmosphere.

External electrodes were formed on each of the obtained sintered bodies using silver paste, and baking was performed using a fixed firing profile.

The electrical characteristics of the multilayer ceramic capacitor produced as described above were measured by the method shown in Examples 1-20.

The results are shown in Table 2.

Comparative Example 11 [Pb (Mg1/2 Wl/2) 03]X [P
bT 103 Koy [Pb (N 11 /3
In the main composition expressed by the composition formula Nb273 >03 ]Z, x=0.3° y=0.4,
A green chip was prepared by the method shown in Example 21 using a composition in which z = 0.3 and Pb2+ was not substituted, and then baked in the same manner as in Example 21, and the electrical characteristics were measured. The properties are shown in Table 2 together with the properties measured in Example 21.

As shown in Table 2, the electrical characteristics of the multilayer ceramic capacitor fired in Example 21 are almost the same regardless of the number of capacitors fired and the firing method, whereas the multilayer ceramic capacitor fired in Comparative Example 11 The electrical characteristics of ceramic capacitors are greatly affected by the firing quantity and firing method.

Incidentally, outside the range of the main components of the present invention, the Curie point is significantly shifted toward the high temperature side or the low temperature side, resulting in a low dielectric constant and impractical. Furthermore, if the amount of Sr2+ or Ba"o substitution exceeds 30mo1%, the firing temperature will exceed 1100°C, making it impossible to use an inexpensive silver-palladium alloy for the internal electrodes. Therefore, the range of the ceramic composition of the present invention is Limited as above.

(The following is a blank space) Table 2 [Effects of the Invention] The ceramic composition of the present invention has a high dielectric constant and a small change in dielectric constant due to temperature. It also has a good dielectric loss value and can be sintered at low temperatures. Therefore, it is possible to manufacture a multilayer ceramic capacitor with excellent temperature characteristics, and inexpensive silver and palladium can be used for the internal electrodes of the capacitor.

Further, the multilayer ceramic capacitor manufactured using the ceramic composition of the present invention can obtain stable characteristics with respect to the firing atmosphere and firing method, and the firing process can be easily managed during mass production.

[Brief explanation of the drawing]

FIG. 1 is a three-component composition diagram showing the main component composition range of the present invention,
FIG. 2 is an explanatory diagram for explaining the firing method used in Examples and Comparative Examples. 1...Lower lid of magnesia sagger 2...Frame of magnesia sagger 3...Top lid of magnesia sagger 4...Magnesia sagger 5...Capacitor green chip

Claims (1)

[Claims] (1) Magnesium lead tungstate [Pb(Mg_
1_/_2W_1_/_2)O_3], lead titanate [P
bTiO_3] and nickel lead niobate [Pb(N
i_1_/_3Nb_2_/_3)O_3]
The component composition is [Pb(Mg_1_/_2W_1_/_2
1/2)O_3]_x[PbTiO_3]_y[Pb(
When expressed as Ni_1_/_3Nb_2_/_3)O_3]_z (where x+y+z=1.0), the following composition point, (x=0.693, y=0.297, z=0.01)(
x=0.495, y=0.495, z=0.01) (x
=0.195, y=0.455, z=0.35) (x=
0.10, y=0.40, z=0.50) (x=0.0
6, y=0.24, z=0.70) and within the composition range surrounded by these five points, lead ions (Pb^2^+) are replaced by barium ions (B
a^2^+), strontium ion (Sr^2^+)
0.5 to 30 mol of at least one type of ion
% substitution.