JPH02267977A - Laminated ceramic element and manufacture thereof - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a multilayer ceramic element having an electrostrictive effect and a method for manufacturing the same, and more particularly to a multilayer ceramic element having an electrostrictive effect and a method for manufacturing the same. The present invention relates to a multilayer ceramic element with excellent durability and a method of manufacturing the same, which is suitable for use in applications such as the above.

TECHNICAL BACKGROUND OF THE INVENTION A multilayer ceramic element having an electrostrictive effect is suitably used for applications such as actuators. An example of a laminated ceramic element used as an actuator is shown in FIG.

In the laminated ceramic element 2 shown in FIG.
It is laminated through. The internal electrodes 6a and 6b are arranged in a staggered manner when viewed from the longitudinal cross-sectional view (FIG. 4(^)), with one internal electrode 6a in every other layer.

6b are connected to common external electrodes 8a and 8b, respectively. In this way, the internal electrodes 6a, 6b and the external electrode 8a
, 8b, when a voltage is applied between the external electrodes 8a and 8b, the ceramic sea! - An electric field is generated in the stacking direction of 4, and the ceramic element 2 is displaced in the direction of arrow A, thereby functioning as an actuator.

Such a laminated ceramic element 2 has a structure in which the laminated ceramic sheets 4 are integrated at a portion 10 where no internal electrode 6a6b is interposed.

However, in such a conventional multilayer ceramic element 2, the upper and lower internal electrodes 6a.

A strong electric field is applied in the part 12 where the 6b overlaps, but the electric field strength is weak in the other part 10, and this part 10
Since the displacement of the overlapping portion 12 is extremely small compared to the displacement of the overlapping portion 12, stress concentration occurs at the boundary between the portion 12 and the portion 10, which may reduce the durability of the element 2.

In order to eliminate such inconvenience, Japanese Patent Laid-Open No. 58-19
As shown in No. 6068, Japanese Unexamined Patent Publication No. 59-175176, and FIG. A laminated ceramic element 2a has been developed in which an insulating layer 14 is provided at the end of the insulating layer 14, and external electrodes 8a and 8b are formed thereon.

According to such a ceramic element 2a, since the internal electrodes 6 are provided on the entire surface between the ceramic sheets 4, a uniform electric field is applied in the stacking direction of the ceramic sheets 4,
It is possible to prevent stress concentration that may occur in the ceramic element 2 as shown in FIG. 4, and to improve the durability of the element.

However, the laminated ceramic element 2 as shown in FIG.
In case a, there is a problem that the work of forming the insulating layer 14 at the end of every other internal electrode 6 is complicated and the manufacturing cost is high. Furthermore, if the insulating layer 14 is incompletely formed, there is a risk that the amphoteric electrodes 8a and 8b may be short-circuited, resulting in defective products.

Purpose of the Invention The present invention has been made in view of the above circumstances, and is capable of preventing the occurrence of stress concentration due to non-uniformity of electric field-induced strain, and is particularly suitable for use in actuators, etc. The purpose of the present invention is to provide a multilayer ceramic element with excellent durability and productivity.

Summary of the Invention In order to achieve the above object, a multilayer ceramic element according to the present invention includes a ceramic sheet having an electrostrictive effect, a film-like internal electrode laminated between the ceramic sheets, and the internal electrode. a block layer laminated between the end portions of the ceramic sheets at a predetermined pressure MM; a cavity formed between the ceramic sheets and between the internal electrode and the block layer; The external electrode extends in the stacking direction so as to connect each block layer, and connects the end of the internal electrode located between every other block layer in the stacking direction every other block layer. It is a feature.

The method for manufacturing a laminated ceramic element according to the present invention includes an internal electrode and a block layer located at a predetermined distance from the internal electrode on one side of a pre-fired ceramic sheet mainly composed of a material having an electrostrictive effect. After forming the internal electrode and the vacant space located between the block layer, the pre-fired ceramic sheet is placed in a position where the block layer is separated between the adjacent ceramic sheets in the stacking direction, and the ceramic sheet is formed in every other layer. A plurality of sheets are stacked at the same position between the sheets, and the internal electrodes are fired at the same time as the ceramic sheets are fired to form voids in the planned spaces between the ceramic sheets. It is characterized in that the ends of the internal electrodes located at are connected by external electrodes in the stacking direction.

In the present invention, the electrostrictive effect refers to the effect of strain induced by an electric field, and more specifically refers to the inverse piezoelectric effect and/or the strain proportional to the applied electric field. It refers to the electrostrictive effect in the narrow sense of producing a strain proportional to the square of the square.

In the laminated ceramic element and the manufacturing method thereof according to the present invention, a block layer is formed at the end of the internal electrode interposed between the ceramic sheets with a space therebetween,
Since this block layer is electrically conductive with the internal electrode, an external electrode is provided to connect this block layer every other layer in the stacking direction. However, in the present invention, in order to form a block layer, when coating and forming an external electrode on the first side of the element, this external electrode is formed. Effectively prevents the material from flowing into the internal electrode side and prevents a pair of external electrodes from shorting through the internal electrode at 1-2.
1- It is possible. Furthermore, the space provided between the block layer and the internal electrode makes it possible to prevent stress concentration due to non-uniform electric field-induced strain, improving durability and improving the laminated ceramic according to the present invention. The element can be suitably used for applications such as actuators. Further, according to the present invention, electric field induction can be applied not only to multilayer actuators that utilize electrostrictive effects, but also to ceramic multilayer elements that also have electrostrictive effects other than electrostrictive effects, such as electro-optic effects. It is also beneficial in that it prevents stress concentration due to non-uniform strain.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a longitudinal sectional view of a multilayer ceramic element according to an embodiment of the present invention, FIG. 2 is a perspective view of a ceramic sheet used in the same embodiment, and FIG. 3 is a ceramic sheet according to another embodiment of the present invention. FIG. 3 is a perspective view of the sheet.

The laminated ceramic element 20 shown in FIG.
This is an element used in 17th. This ceramic element 2
0 indicates a structure in which a ceramic sheet 22 exhibiting an electrostrictive effect a and a film-like internal electrode 24 are alternately laminated (-4L, - a1~).

The film-like internal electrode 24 is, for example, as shown in FIG.
It is formed by shaking a metal paste on the surface of the ceramic sheet 22 before lamination.

Internal fit! Metals for configuring i24 and 1~,
Examples include platinum, palladium, silver-palladium, and silver. Since the ceramic sheets 22 are fired in a laminated state, it is preferable to select a metal paste that can be fired at the ceramic firing temperature as the metal paste for forming the internal electrodes 24. ,
Zirconia powder, glass powder, calcined powder of the present electrostrictive ceramic, etc. may be mixed into the metal paste in order to equalize the adhesion strength between the ceramic sheet 22 and the internal electrode 24 after firing.

When applying and forming the metal base on the surface of the ceramic sheet 22, as shown in FIG. The predetermined type M is determined by this blank space 26.
A block layer 2 is formed on the surface of one end of the sheet 22 separated by U.
form one.

Although it is economical to form the block layer 29 using the same metal paste as the internal electrode 24, the block layer 29 is not limited to this, and may be formed from other materials, such as a non-conductive material.1. But it's okay. It is preferable that the film thickness of the cover 12 and the block layer 29 be approximately the same as the film thickness of the internal electrode 24 . This is to ensure flatness when laminating ceramic sheets.

The shape and position of the block layer are not particularly limited. For example, as shown in FIG. 3, the block layer may be formed on the surface of one corner of the ceramic sheet 22. In this embodiment, the block layer 29 has a triangular shape. Also in this embodiment, the internal electrode 24 and the block layer 29 are in a non-conducting state.

The film thickness of such block layer 29 and internal electrode 24 is not particularly limited, but is the film thickness after firing, and is preferably 0.
．． 5 to 20 μm, more preferably 1 to 10 μm. The metal paste is applied using screen printing method,
This can be done by a method such as a roller printing method.

The ceramic sheet 22 is made of PbTiO3, PbZr0
, Pb (MgNb)
0. 3 1/3 2
/3 3 Pb (Ni Nb ) 03 as a main component, and is made of a material that has an electrostrictive effect after 173 2/3 firing.

The ceramic sheet 22 before being laminated and fired is manufactured, for example, as follows.

First, when water is used as a solvent for the calcined powder of the ceramic, which is the main component, a binder such as hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol, wax-based lubricant, carboxymethyl cellulose, etc., and glycerin, polyalkyl glycol, sorbitan acid, etc. After adding a plasticizer such as esters, triethylene glycol, petriol, or polyol, these are mixed to produce a molded precursor. In addition, when using an organic solvent such as ethyl alcohol, methyl ethyl ketone, benzene, or toluene, a binder such as polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, or cellulose acetate, dibutyl phthalate,
After adding a plasticizer such as polyethylene glycol or glycerin, these are mixed to produce a molded precursor.

The pre-fired ceramic sheet 22 can be obtained by molding such a molded precursor to a desired thickness by a method such as a doctor blade method or an extrusion molding method, and cutting it into a predetermined shape after drying. The thickness of the pre-fired ceramic sheet 22 is not particularly limited, but is preferably 0.02 to 2 m+s,
More preferably, it is 0.05 to 0.5 degrees. after that,
As shown in FIG. 2, internal electrodes 24 and a block layer 29 are coated on the surface of the ceramic sheet 22 before firing.

In the present invention, the method for forming the pre-fired ceramic sheet 22 is not particularly limited, but preferably uses water as a solvent and obtains the sheet by extrusion.

According to such a forming method, it is easy to reduce the amount of binder and/or plasticizer, and the non-adhesiveness of the sheets obtained after drying is improved, and when these are laminated and fired, In addition, it is possible to prevent the upper and lower sheets 22 from adhering to each other in the intended void area 26 formed between the internal electrode 24 and the block layer 29, making it easier to form the void 30 in this area. Note that, depending on the type and amount of the binder and plasticizer, the non-adhesive ceramic for forming the cavity 30 may be formed by extrusion molding using an organic solvent or by a doctor blade method using an organic solvent or water. It is also possible to obtain a sheet 22.

The type and amount of the binder and plasticizer and the drying conditions of the ceramic sheets 22 are such that when the ceramic sheets 22 are pressed together under conditions of 150° C. or less and 200 kg/cd or less, the tensile shear adhesive strength is the same before firing. The tensile strength of the ceramic sheet 22 itself is preferably selected to be 10% or less, particularly preferably 5% or less.

When forming the pre-fired ceramic sheet 22 by extrusion using water as a solvent, the amount of binder added is preferably 1 to 10 parts by weight, when the calcined powder is 100 parts by weight. Particularly preferably 2 to 5 parts by weight. The amount of plasticizer added is preferably 1 to 10 parts by weight, particularly preferably 2 to 5 parts by weight.

After being formed and dried in this way, the internal electrode 24 and the block layer 29 are formed on one side of the pre-fired ceramic sheet 22 which is cut into a predetermined shape and spaced therefrom, as described above. Next, a plurality of ceramic sheets 22 on which internal electrodes 24 and block layers 29 have been formed are stacked so that the block layers 29 are alternately positioned on the left and right as shown in the perspective view shown in FIG. 2, and then heated in a hot press. After crimping and bonding, the ceramic sheet 22 is degreased and fired at a predetermined temperature, and at the same time, the internal electrodes 24 are baked to bond the ceramic sheet 22, the internal electrodes 24, and the block layer 29 together. Note that the laminate may be further cut into a predetermined size prior to degreasing, or may be cut after firing. Further, the block layers 29 do not necessarily need to be arranged alternately on the left and right, but may be arranged so that they are at different positions between adjacent ceramic sheets in the stacking direction, and at the same position between every other ceramic sheet.

In this way, when the laminate is fired, the upper and lower ceramic sheets 22 do not adhere to each other in the space 26 between the internal electrode 24 and the block layer 29.
A void 30 is formed in this portion.

Thereafter, a pair of external electrodes are connected so as to connect every other block layer 29 in the stacking direction, and to connect the ends of the internal electrodes 24 located between every other block layer 29. By forming the angle of 32° 32, the laminated ceramic element 20 according to the present invention can be obtained. For the external electrodes 32, 32 and 1°, for example, silver, gold or the like can be used, although there is no particular limitation. The method of forming the external electrodes 32 is not particularly limited either, but for example, a silver paste may be applied along the lamination direction and then baked. Note that the external electrode 32
The width of the block layer 29 is preferably smaller than the width of the block layer 29. If it is large, when forming the external electrode 32 by coating, there is a risk that the external electrode 32 will come into contact with the internal electrode 24 at a portion other than the block layer, and the inner and outer electrodes 32 and 32 may be sheeted through the internal electrode 24. be.

When a lead wire 34 is connected to the external electrode 32 (2) and a voltage is applied from a power source 36, an electric field is applied in the stacking direction of the ceramic element 20, causing displacement in the stacking direction and functioning as an actuator or the like.

DETAILED DESCRIPTION OF THE INVENTION 17 As described above, according to the present invention, a block layer is formed at the end of an internal electrode interposed between ceramic sheets through a cavity, and this block layer is electrically connected to the internal electrode. Therefore, by providing external electrodes so as to connect every other block layer in the stacking direction, it is possible to easily connect the ends of the internal electrodes every other layer. Moreover, since the present invention has a block layer, when forming the external electrode by coating on one side of the element, the material constituting the external electrode does not flow into the internal electrode side, and the pair of external electrodes is connected via the internal electrode. Short circuits can be effectively prevented by RF. Roughly speaking, the space provided between the block layer and the internal electrode reduces stress concentration due to non-uniformity of electric field-induced strain by 1! It has improved durability and is suitable for applications such as actuators. Further, according to the present invention, the electrostrictive effect is utilized 1. It is used not only for applications such as multilayer actuators, but also for non-uniformity of electric field-induced strain in ceramic multilayer elements that also have electrostrictive effects, such as electro-optical effects. This is also an advantage in that it also prevents stress concentration due to

[Examples] The present invention will be described below based on more specific examples.

Example 1 PbT to , PbZ ro , P b (
Methylcellulose as a binder and glycerin as a plasticizer were added to a calcined powder of an electrostrictive ceramic material containing Mg173Nb )0 as a main component using water as a solvent, and then mixed well to prepare a molded precursor. This molded precursor was molded into a 120 μm thick green sheet 12 by extrusion molding and dried. This is cut into a predetermined shape 12, and a silver-palladium paste is applied to one side by screen printing, and the internal electrode 24 and the width g are formed as shown in FIG.
At the same time, a block layer 29 was formed, which was separated from the block layer 29 via a planned void area 26 which was a 0.5 mm non-base coated area.

Laminate 100 printed green sheets and press them together using a hot press (also, when laminating, block layer 29
are located alternately on the left and right between adjacent sheets in the stacking direction, and are located at the same position between every other sheet. The obtained laminate was degreased at 500°C, then fired at 1100°C, and then cut into - elements.

When the cross section of the thus obtained laminated sintered body was observed with a scanning electron microscope, it was found that the internal electrodes 24 and the block layer 2
It was confirmed that the film thickness of No. 9 was 2 to 3 μm, and a void 30 with a height of 2 to 3 μm was formed in the gap between the internal electrode 24 and the block layer 29.

Next, as shown in FIG. 2, external electrodes 32° 32 were formed by applying and baking silver paste, and the ends of the internal electrodes 24 located between the alternate block layers were electrically connected in the stacking direction. . Further, lead wires were attached to the external electrodes by soldering, and polarization was performed by applying a predetermined DC voltage through the lead wires to obtain a multilayer ceramic element 20 as shown in FIG.

The dimensions of this laminated ceramic element are length x width x height.
When a DC voltage of 100 V was applied to this, a displacement of 10 μm was observed. moreover,
When we conducted a life test of this element by continuously applying sinusoidal voltage pulses with a maximum voltage of 100 V and a frequency of 1 kHz, there was no decrease in displacement even after applying voltage pulses approximately 100 million times, and the element remained stable. No destruction was recognized. On the other hand, in a similar life test, the conventional multilayer device shown in FIG. 4 was found to be destroyed after approximately 10,000 voltage pulses were applied.

Therefore, when compared with the multilayer ceramic element as shown in FIG. Since stress concentration can be prevented, the durability is significantly improved. In addition, when compared with the multilayer ceramic element shown in Fig. 5, there is no need to form the ends of internal electrodes for every other insulating layer, and the product is defective due to defects in the formation of the insulating layer. Since problems such as the occurrence of problems can be avoided, the method is characterized in that it is easy to produce and can be produced with a high yield.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a multilayer ceramic element according to an embodiment of the present invention, FIG. 2 is a perspective view of a ceramic sheet used in the same embodiment, and FIG. 3 is a ceramic sheet according to another embodiment of the present invention. FIG. 4.5 is a perspective view of the sheet, and FIG. 4.5 is a sectional view of a laminated ceramic element according to a conventional example.
B) is a cross-sectional view. 20... Laminated ceramic element 22... Ceramic sheet 24... Internal electrode 2
6... Blank space planned 29... Block layer 3
0...Vacancy 32...External electrode No.
1 Figure 2゜

Claims (1)

[Scope of Claims] 1) A ceramic sheet having an electrostrictive effect, a film-like internal electrode laminated between the ceramic sheets, and a ceramic sheet between the ends of the ceramic sheet at a predetermined distance from the internal electrode. extending in the stacking direction so as to connect the block layers to be stacked, the voids formed between the ceramic sheets and between the internal electrodes and the block layers, and every other block layer; Moreover, the multilayer ceramic element has external electrodes that connect the ends of the internal electrodes located between every other block layer in every other layer in the stacking direction. 2) An internal electrode, a block layer located a predetermined distance from the internal electrode, and a block layer located between the internal electrode and the block layer on one side of a pre-fired ceramic sheet whose main component is a material having an electrostrictive effect. After forming the blank space to be
This pre-fired ceramic sheet is placed in a position where the block layer is separated between adjacent ceramic sheets in the stacking direction,
A plurality of ceramic sheets are stacked at the same position between every other ceramic sheet, and the internal electrodes are fired at the same time as the ceramic sheets are fired to form a void between the ceramic sheets. A method for manufacturing a multilayer ceramic element, characterized in that ends of internal electrodes located between alternate block layers are connected by external electrodes in the stacking direction.