JPS6325912A - Ceramic capacitor - 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] [Industrial application field] The present invention relates to ceramic capacitors.

[Conventional technology]

The conventional technology will be explained using figures.

Figure 2 (ah) shows a conventional ceramic capacitor, Figure 2 (a) is a cross-sectional view, and Figure 2 (b) shows a
It is an enlarged view of part B in figure (a). A pair of baked electrodes 1 are provided on a dielectric body made of a ceramic sintered body 2.

In a single disk type ceramic capacitor, the fired ceramic sintered body is parallel-polished so that the electrodes are parallel to each other, then silver paste is applied and the electrodes are fired in an electric furnace. In addition, in multilayer ceramic capacitors, the pre-fired dielectric is made into a thin sheet using a blade, this sheet is coated with metal paste, then stacked in several layers and placed in an electric furnace to perform main firing and electrode baking at the same time. .

[Problem that the invention seeks to solve]

The above-described conventional ceramic capacitors had a drawback in that when the electrodes were baked, the components of the electrodes diffused along the grain boundaries of the ceramic sintered body, resulting in an increase in dielectric loss compared to the designed value.

[Means for solving problems]

In the ceramic capacitor of the present invention, another ceramic sintered body whose crystal grain boundaries are filled with a transition element oxide is interposed between the baked electrode and the ceramic sintered body.

〔Example〕

Next, embodiments of the present invention will be described with reference to figures.

Figure 1 (a> is a sectional view of an embodiment of the present invention, Figure 2 (b)
) is an enlarged view of part A in FIG. 1(a).

In this example, the baking is made of electrode 1 and PZT with a thickness of 50 mm.
A ceramic sintered body 3 having a thickness of 50 to 100 μm and having crystal grain boundaries filled with Mn oxide is interposed between the ceramic sintered body 2 having a thickness of 0 to 700 μm. PZT
(Pb (Ti xZrl-x)○s, o<x<1), with a composition where X is around 0.4 to 0.6, the Curie point is 3
00° C., and the dielectric constant near room temperature is about 1000.

The main firing temperature is about 1200℃, but since lead evaporates from the surface, a lead-deficient state tends to occur on the surface.
When Ag-Pd is baked at 0°C, the electrode components are slightly diffused. For this reason, if a thin dielectric layer is formed between Ag-Pd and PZT by mixing 1 to 2% by weight of an oxide of a PZT transition element, the intrusion of Ag-Pd will be prevented and the dielectric loss will increase. can be prevented. Since the oxide of the transition element covers the grain boundaries of PZT, it functions to prevent the diffusion of electrode components from the electrode baked portion. The transition element oxide is blended in an amount of about 1 to 2% by weight to sufficiently cover the grain boundaries. On the other hand, if it is added too much, the overall dielectric constant decreases and the capacitance decreases. Therefore, the ceramic sintered body 3, which is a dielectric layer containing a transition element oxide, is made thinner than the ceramic sintered body 2, which is a dielectric layer of the main body, to achieve the minimum thickness necessary to prevent diffusion of electrode components. Set aside.

Note that the transition element oxide does not need to completely fill the grain boundaries.

Next, the manufacturing method of this example will be explained.

The powder raw materials PbO, TiO2, and ZrO2 are weighed using a high precision balance that matches a predetermined stoichiometric ratio, and then they are stirred in a mill. After that, a binder such as polyvinyl alcohol (PVA) is added to the matrix, which is then pressed with a mold to an appropriate size, and then pre-sintered in an electric furnace at 850°C for 2 hours to produce pre-sintered PZT. First, the powdered PZT is pulverized into powder and divided into two containers.

The weight of the PZT powder in one container is weighed, and 1 to 2% by weight of MnO2 is added to the weight, followed by stirring. Then add PVA to each container. After addition, first put the Mn○2 PZT powder into the bottom of the mold, then add the PZT powder.
PZT powder was further put on top of it, pressed and molded, and then heated in an electric furnace at 1200℃ for 2 hours.
Since the melting point of MnO2 is 535° C., this main firing produces a ceramic sintered body sandwiched between other ceramic sintered bodies in which the grain boundaries are filled with Mn oxide.

〔Effect of the invention〕

As explained above, in the present invention, baking can be prevented by providing another ceramic sintered body layer between the electrode and the ceramic sintered body in which the grain boundaries are filled with transition element oxide. This has the effect of preventing components from diffusing into the interior and suppressing an increase in dielectric loss of the ceramic capacitor.

[Brief explanation of the drawing]

Figure 1 (a> is a sectional view of one embodiment of the present invention, Figure 1 (b)
) is an enlarged view of section A in FIG. 1(a), FIG. 2(a) is a sectional view of the conventional example, and FIG. 2(b) is an enlarged view of section B in FIG. 2(a).

Claims (1)

[Claims] A ceramic capacitor characterized in that another ceramic sintered body whose crystal grain boundaries are filled with a transition element oxide is interposed between the baked electrode and the ceramic sintered body.