Non-reducable, low temperature dielectric ceramic...

Details Non-reducable, low temperature dielectric ceramic... Non-reducable, low temperature dielectric ceramic...

2002-12-19

2004-08-17

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Titanate, zirconate, stannate, niobate, or tantalate or...

C501S138000

Reexamination Certificate

active

06777363

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-reducible dielectric ceramic composition, and more particularly to a non-reducible dielectric ceramic composition which has a high dielectric constant when sintered at a low temperature and satisfies X5R characteristics (−55 to 85° C., &Dgr;C=±15%), a multilayer ceramic chip capacitor using the composition and a method for preparing the multilayer ceramic chip capacitor.
2. Description of the Related Art
Multilayer ceramic chip capacitors are widely used as electronic parts featuring a small size, high capacitance and high reliability, with a number of such capacitors being employed in one electronic device. In the recent drive toward small-size, high-performance devices, there is an increasing requirement to develop multilayer ceramic chip capacitors of smaller size, higher capacitance, lower cost, and higher reliability. The multilayer ceramic chip capacitors are generally manufactured by alternately stacking dielectric layers and internal electrode layers, followed by sintering.
Palladium or palladium alloys have generally been used as the conductor of an internal electrode. Recently, use of relatively inexpensive base metals such as nickel or nickel alloys as the conductor of an internal electrode has increased. In the event that base metals are used as the conductor of an internal electrode, the internal electrodes may be oxidized upon being sintered in air. Therefore, co-sintering of dielectric layers and internal electrode layers must be effected in a reducing atmosphere. However, sintering in a reducing atmosphere causes the dielectric layers to be reduced, resulting in a lower resistivity. Non-reducible dielectric ceramic materials were thus proposed.
However, multilayer dielectric ceramic chip capacitors using non-reducible dielectric ceramic materials have a remarkably deteriorated insulation resistance (IR) when an electric field is applied. That is, they have problems including a short lifetime of IR and low reliability. When the dielectric materials are subject to a direct current electric field, there arises another problem that their dielectric constant (&egr;
r
) is reduced with time. If thinner dielectric ceramic layers are used in order to provide chip capacitors of a smaller size and greater capacitance, application of direct current voltage across the capacitors causes the dielectric ceramic layers to receive a stronger electric field, resulting in a greater change of dielectric constant &egr;
r
with time (that is, a greater change of capacitance with time). Capacitors are also required to have an excellent temperature characteristic of capacitance (TCC). Capacitors used for particular purposes are required to have a stable temperature characteristic of capacitance under severe conditions. Exemplary temperature-compensating dielectric ceramic materials which are excellent in a temperature characteristic of capacitance are compositions of (Sr, Ca) (Ti, Zr)O
3
, Ca(Ti, Zr)O
3
, Nd
2
O
3
-2TiO
2
, and La
2
O
3
-2TiO
2
. However, these materials have a very low dielectric constant (generally, 100 or less) and thus cannot be used in preparing capacitors with a high capacitance.
A composition having BaTiO
3
as a major component with Nb
2
O
5
—Co
3
O
4
, MgO—Y, a rare earth element (Dy, Ho, etc.), BaTiO
3
—TiO
2
, etc. added is disclosed, which has a high dielectric constant and a fixed temperature characteristic of capacitance. However, the dielectric ceramic composition including BaTiO
3
as a major component fails to satisfy XR characteristics (&Dgr;C=±15%) at a high temperature, because a Curie temperature of BaTiO
3
is about 130° C.
Exemplary dielectric ceramic compositions with BaTiO
3
as a major component are disclosed in U.S. Pat. No. 5,668,694; U.S. Pat. No. 5,862,034; Japanese Patent Application Laid-Open Publication No. 6-215979; Japanese Patent Application Laid-Open Publication No. 2000-311828 and Korean Patent Application Laid-Open Publication No. 2000-0012080.
U.S. Pat. Nos. 5,668,694 and 5,862,034 disclose a multilayer ceramic chip capacitor that contains BaTiO
3
as a major component and MgO, Y
2
O
3
, BaO, CaO, SiO
2
, MnO, V
2
O
5
, and MoO
3
as minor components in such a proportion that there are present MgO: 0.1 to 3 mol, Y
2
O
3
: 0 to 5 mol, BaO+CaO: 2 to 12 mol, SiO
2
: 2 to 12 mol, MnO: 0 to 0.5 mol, V
2
O
5
: 0 to 0.3 mol, MoO
3
: 0 to 0.3 mol, and V
2
O
5
+MoO
3
: more than 0 mol, per 100 mol of BaTiO
3
. This capacitor satisfies X7R characteristics but has disadvantages in that its dielectric constant is as low as 2,600 and it must be sintered at a high temperature of 1,300° C.
Japanese Patent Application Laid-Open Publication No. 6-215979 discloses a dielectric ceramic composition which comprises, BaTiO
3
: 86.32 to 97.64 mol, Y
2
O
3
: 0.01 to 10.00 mol, MgO: 0.01 to 10.0 mol, V
2
O
5
: 0.001 to 0.200 mol, at least one selected from MnO, Cr
2
O
3
and Co
2
O
3
: 0.01 to 1.0 mol, and BaxCa(1−x)SiO
3
(provided that 0≦x≦1): 0.5 to 10 mol. This dielectric composition has a dielectric constant of 2,560 to 3,850 and satisfies X7R characteristics, but has a sintering temperature of as high as 1,300 to 1,380° C.
Japanese Patent Application Laid-Open Publication No. 2000-311828 discloses a dielectric ceramic composition which comprises, BaTiO
3
: 100 mol, at least one selected from MgO and CaO: 0.1 to 3 mol, MnO: 0.05 to 1.0 mol, Y
2
O
3
: 0.1 to 5 mol, V
2
O
5
: 0.1 to 3 mol and BaxCa(1−x)SiO
3
(provided that 0≦x≦1): 2 to 12 mol. This dielectric composition satisfies X7R characteristics, but has a dielectric constant of less than 3,000 and a sintering temperature of as high as 1,270° C.
Korean Patent Application Laid-Open Publication No. 2000-0012080 discloses a dielectric ceramic composition which comprises, per 100 mol of BaTiO
3
as a major component, Cr
2
O
3
: 0.1 to 3 mol, V
2
O
5
: 0.01 to 0.5 mol, an oxide of R1 (R1: Y, Ho or Dy): 0.7 to 7 mol and MnO: 0.5 or less. This dielectric composition has a dielectric constant of 1,473 to 3,086 and satisfies X8R characteristics (−55 to 150° C., &Dgr;C=±15%) but is required to have a sintering temperature of as high as 1,280 to 1,300° C.
These BaTiO
3
-based dielectric ceramic compositions satisfy X7R characteristics (—55 to 125° C., &Dgr;C=±15%) stipulated under the EIA standard but have a low dielectric constant. Especially, in the case that a dielectric constant is 3,000, a sintering temperature is too high, for example, 1,300° C. or more. If the sintering temperature is as high as 1,300° C., an internal electrode layer shrinks at a lower temperature than a dielectric ceramic layer, thereby interfacial delamination of the two layers occurring. Furthermore, at higher sintering temperatures, lumping or break between internal electrode layers frequently occurs, thereby the reduction of capacitance and the short circuit between internal electrodes being liable to occur.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a dielectric ceramic composition which has a high dielectric constant even at a low sintering temperature, satisfies X5R characteristics (−55 to 85° C., &Dgr;C=±15%), can be sintered under a reducing atmosphere and shows a long lifetime of IR. Another object of the invention is to provide a multilayer ceramic chip capacitor using the composition and a method for preparing the multilayer ceramic chip capacitor.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by providing a dielectric ceramic composition which comprises, BaTiO
3
; MgCO
3
: 0.2 to 3.0 mol; at least one selected from Y
2
O
3
, Ho
2
O
3
, Dy
2
O
3
and Yb
2
O
3
: 0.05 to 1.5 mol; Cr
2
O
3
: 0.1 to 1.5 mol; BaxCa(1−x)SiO
3
(provided that 0≦x≦1): 0.2 to 3.0 mol; and Mn
2
V
2
O
7
: 0.01 to 1.5 mol, per 100 mol of BaTiO
3
.
In ac

Affiliated with

Also associated with

Rating

Non-reducable, low temperature dielectric ceramic... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Non-reducable, low temperature dielectric ceramic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-reducable, low temperature dielectric ceramic... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3292614