JPS63108611A - Dielectric ceramic composition - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high dielectric constant dielectric ceramic composition that is fired at a temperature of 1100°C or lower, and in particular a composition that can be fired in a low oxygen partial pressure atmosphere and has a high resistivity. It also relates to dielectric ceramics with high mechanical strength.

BACKGROUND OF THE INVENTION In recent years, multilayer ceramic capacitors are rapidly becoming popular due to the demand for smaller elements and larger capacitance in ceramic capacitors. Multilayer ceramic capacitors are typically manufactured by a process of integrally firing internal electrodes and ceramics. Barium titanate-based materials have traditionally been used as high-permittivity ceramic capacitor materials, but
Since the firing temperature is as high as about 1300° C., it is necessary to use expensive metals such as Pi and Pd as internal electrode materials.

On the other hand, there are lead composite perovskite materials that can be fired in air at temperatures below 1000°C and inexpensive Ag-based materials can be used as internal electrodes, and N-based composite materials that can be fired in a low oxygen partial pressure atmosphere.
Barium titanate-based materials have been developed in which base metal materials such as i can be used as internal electrodes. Regarding the former, as a system similar to the present invention, PbTi0*Pb(Njt/2Nb*,s
) Os Pb(N i 1/2 Wst2) Os
A dielectric ceramic composition containing the following is known. Regarding the latter, materials such as those described in Japanese Patent Publication No. 56-46641 are known.

Furthermore, the inventors have discovered that PbTiO3-Pb (Ni violet/I
Nbzzs)O! J-Pb (Nitz2W1/2)
As a composition that further improves the O2) Os-based solid solution,
(Pb a Me b) 1 (Nis/2Nb2t3)
x Ti y (Nitz2W1/2)O2 )Z10
We propose a composition represented by 2+a+b in which Me is at least one selected from the group consisting of Ca, Sr, and Ba. This composition has the property of being able to be fired at low temperatures and exhibiting high resistivity when fired under low oxygen partial pressure, and is an excellent material that can be used in multilayer capacitor elements that use copper or copper-based internal electrodes. It is a dielectric ceramic composition. However, dielectric ceramics after firing have low mechanical strength, and when used as a multilayer capacitor element, there is a problem in that the bending strength of the element becomes low. Ceramic multilayer capacitor elements are often used as surface-mounted components that are mounted on a circuit board using an insert machine, and if the element has low bending strength, the element will be damaged. For this reason, dielectric ceramics used in multilayer capacitor elements are required to have as high mechanical strength as possible.

Problems to be solved by the invention (Pb a Me b) l (Nltz2Nbqts
) x Ti y(Ni1z* W1/2)O2
) zl 02 +a+b, Me is Ca, Sr
A dielectric ceramic composition comprising at least one selected from the group consisting of , Ba, has a problem in that the mechanical strength of the dielectric ceramic after firing is weak.

The present invention provides a dielectric porcelain composition that can obtain dielectric porcelain with high mechanical strength without impairing the low-temperature sinterability, dielectric properties, and high resistivity properties of the above composition when fired under low oxygen partial pressure as much as possible. The purpose is to provide something.

Means to solve problems (Pba Meb) (Nitls Nb2t3) xT
iz (Nitz2W1/2)O2 ) 02 +s+b
For a composition in which Me is at least one component of the group consisting of Ca, Sr, and Ba, as a subcomponent,
0.06 to 0.4% by weight of at least one component selected from the group consisting of MnO2, Cr2O3゜MOO3
The composition contains 0%.

Effect In the dielectric ceramic composition system of the present invention, the fracture surface in a normal three-point bending test shows intergranular fracture over the entire range in the composition not containing the subcomponent, whereas the composition containing the subcomponent shows intergranular fracture over the entire range. Partially shows intragranular fracture. That is, in the composition of the present invention, the bonding strength of the grain boundaries of the dielectric ceramic after firing increases, and therefore the mechanical strength of the dielectric ceramic increases.

Example Starting materials include chemically highly pure PbO and Nip.

MeCOs (Me:Ca, Sr, Ba), Nb
s+Os.

TiO2, Nip, WO+3. MnO2, Cr20a.

MoO+1 was used. After correcting the purity of these, a predetermined amount was weighed and mixed in a ball mill for 5 hours using zirconia cobblestones and pure water as a solvent. This was suction filtered to remove most of the water, then dried, and then thoroughly crushed in a Raikai machine. 5 wt% of water was added to the powder amount, and the powder was molded into a cylindrical shape with a diameter of 60 mm and a height of about 50 mm. It was molded at 500 kg/cl. This was placed in an alumina crucible, covered with a homogeneous lid, and calcined at 750°C to 880°C for 2 hours. Next, the calcined product is roughly crushed in an alumina mortar, and then crushed in a ball mill using zirconia cobblestones and pure water as a solvent.
The mixture was ground for 7 hours, filtered under suction to remove most of the moisture, and then dried. After repeating the above calcining, crushing, and drying several times, a 6 wt% aqueous solution of polyvinyl alcohol was added to the powder in an amount of 6 wt% of the powder amount, granulated through a 32-mesh sieve, and molded at a molding pressure of 1000 kg/cm2. did. The molded product was heated to 700° C. in air and held for 1 hour to burn out the polyvinyl alcohol content. This was transferred to a Magnesia porcelain container on which about 1/3 of the calcined powder was spread, and 200 mesh Zro2 was spread about 1 mm thick, the container was covered with a homogeneous lid, and the container was inserted into the core tube of a tubular electric furnace. After deaerating the inside of the reactor core tube with a rotary pump, N2-
82 mixed gas, and the oxygen partial pressure (PO2) was 1. O
Flow the mixed gas while adjusting the mixing ratio of N2 and H2 gas so that it becomes
The temperature was raised at a rate of 400°C/hr, held for 2 hours, and then lowered at a rate of 400°C/hr. Po2 in the reactor core tube was measured by an inserted stabilized zirconia oxygen sensor. FIG. 2 shows the structure of the Magnesia porcelain container during firing, and FIG. 3 shows a cross-sectional view of the inside of the furnace tube.

In FIG. 2, 1 is a magnesia container, the upper part of which is sealed with a magnesia container lid 2. Calcined powder 3 was placed at the bottom of magnesia container 1, and zirconia powder 4 was placed on top of it. Further, sample 5 was placed on top of it. The magnesia container 1 prepared as shown in Fig. 2 is inserted into the furnace core tube 6 as shown in Fig. 3.
placed inside. 7 is a stabilized zirconia oxygen sensor.

The fired product was cut into a plate shape with a thickness of 1 mrr+, and both sides were coated with Cr-
Au was evaporated, the dielectric constant, tan δ was 1 kHz, IV/
Measurements were made under an electric field of mm. Also, the resistivity is 1kV/m
The voltage of m was determined from the value 1 minute after application.

The firing temperature was set at the temperature at which the density of the fired product was the highest.

The mechanical strength of dielectric porcelain is as follows:
mm, length 15+++m, each side was polished with alumina grain size of about 0.6μI, and the support point spacing was 1.
Using a three-point bending device of 01IIl, bending failure load (W
kg) was measured, and the mechanical strength was determined from this value using the following formula. Mechanical strength was determined from the average value of 2o samples.

a-33,3W (kg/cm2) Table 1 shows the composition range of the present invention and the surrounding composition components [a, b
, x, y, z are (Pba Meb) (N1tzzN
b2t3)xTiy(Nitz2W1/2)O2)Z
02 i”b], firing temperature when firing in a low oxygen partial pressure atmosphere, dielectric constant, tan δ,
Resistivity, density and mechanical strength were shown.

FIG. 1 shows the main composition of the present invention: (Pb a Me b) Ti02 +a+b; (Pb
a Me b) (Nixz* Nb2t3)02
J+ll; (Pb a Me b) (Nitz+ W1
/2)O2)02+*+b is shown in a triangular composition diagram as an end member, and the diagonally shaded range is the main composition range.

In a composition outside the scope of the invention, the amount of subcomponents is 0.06wt? , ;
If it is smaller than 0.40w, the effect of improving mechanical strength will not appear.
thicker than t% (if this happens, the mechanical strength will decrease again, or
Or, the dielectric properties (dielectric constant and resistivity decrease significantly).The composition within the scope of the invention overcomes all of the above problems.The range of the main components is This is limited by the density, resistivity, dielectric constant, and humidity change rate of the dielectric constant of the fired product.

The low oxygen partial pressure atmosphere selected as the firing atmosphere, PO
2; 1. OOxlo-8at is an oxygen partial pressure at which copper is hardly oxidized at the firing temperature, and satisfies the manufacturing conditions of a wall layer capacitor including copper or internal electrodes mainly composed of copper.

Effects of the Invention According to the present invention, a dielectric ceramic having a high dielectric constant, high density, high resistivity, and high mechanical strength can be obtained by firing at 1100° C. or lower in a low oxygen partial pressure atmosphere. Therefore, when the composition of the present invention is used as the dielectric of a multilayer capacitor element using Cu as the internal electrode, a large bending strength can be obtained without impairing the electrical characteristics, and the element can be easily removed when mounted on a circuit board. damage is prevented.

[Brief explanation of the drawing]

Fig. 1 is a triangular composition diagram showing the main component composition of the porcelain composition according to the present invention, Fig. 2 is a cross-sectional view of a magnesia container in which the porcelain is placed during firing, and Fig. 3 is a cross-sectional view of the furnace tube during firing. . 1...Magnesha container, 2...Magnesha container lid, 3...Calcined powder, 4...
・Zirconia powder, 5... Sample, 6...
・Magnesha container, 7...Furnace tube, 8...
...Stabilized zirconia oxygen sensor. Name of agent Patent attorney Toshio Nakao and one other person (PbaM
ebXNi +/3Nb2/3 )02+a+b Fig. 1

Claims (1)

[Claims] (Pb_aMe_b) {(Ni_1_/_3Nb_2_
/_3)xTiy(Ni_1_/_2W_1_/_2)
It has a composition represented by z}O_2_+_a_+_b, and (
However, x+y+z=1), Me is at least one selected from the group consisting of Ca, Sr, and Ba, and is in the range of 0.001≦b≦0.250 1.001≦a+b≦1.200; For each value of a and b within the range, (P
b_aMe_b)(Ni_1_/_3Nb_2_/_3
)O_2_+_a_+_b;Pb_aMe_b)TiO
_2_+_a_+_b; and (Pb_aMe_b)(
Ni_1_/_2W_1_/_2) O_2_+_a_+
In the triangular coordinates with _b as the vertex, the following composition points, A, B
, C, D, E, A; x=0.850y=0.149z=0.001B;
x=0.450y=0.549z=0.001C;x=
0.001y=0.750z=0.249D:x=0.
MnO
0.06 to 0.4% by weight of at least one component selected from the group consisting of _2, Cr_2O_3, and MoO_3.
A dielectric ceramic composition characterized by containing 0%.