JPS62276887A - Manufacture of piezoelectric ceramic laminate - Google Patents

Abstract

PURPOSE:To improve reliability of a piezoelectric ceramic laminate by preparing a laminate where ceramic layers and porous layers are reciprocally laminated and providing porous layers with specific conductance. CONSTITUTION:A laminate arranged by laminating reciprocally ceramic layers and porous layers which are used for electrode layers 3 provides porous layers with specific conductance. As a result, the laminate eliminates the need for the use of expensive conductive materials for forming electrodes and is capable of manufacturing the inexpensive piezoelectric ceramic laminate which is driven at a low voltage. Further, the formation of porous layers that are turned into electrode layers 3 at a process prior to using the conductive materials permits the ceramic layers 2 and porous layers to be laminated in a favorable state irrespective of the conductive materials. Thus, this process improves reliability of the piezoelectric ceramic laminate.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Technical Field] The present invention relates to a method for manufacturing a piezoelectric ceramic body in which ceramic layers and electrode layers are alternately laminated.

[Background Art] A piezoelectric ceramic body in which ceramic layers and electrode layers are alternately laminated has conventionally been manufactured by the following method.

A binder and the like are added to ceramic calcined powder having a desired composition, and the resulting slurry is mixed, pulverized, and defoamed to form a green sheet using a doctor blade method or an extrusion method. After cutting this green sheet, a plurality of green sheets having electrode patterns printed on their surfaces using conductive paste are stacked one on top of the other, and are bonded and laminated by thermocompression at a temperature of 60 to 15 G'C. Thereafter, the laminate is sintered to obtain a piezoelectric ceramic body in which piezoelectric ceramic layers and electrode layers made of conductive paste are alternately laminated. The binder is removed during the sintering process. The external electrodes are attached after sintering.

This conventional manufacturing method has the advantage that it is excellent in mass production, and that the thickness of each ceramic layer can be made thinner so that the driving voltage can be lowered. However, since the electrode layer and the ceramic layer are simultaneously fired at a high temperature of approximately 1300° C., the material for forming the electrode must be able to withstand the high sintering temperature. Therefore, an expensive Ag-Pd material with a high content of Pd is used. Therefore, the cost becomes extremely high when the layer is multi-layered. Moreover, due to the difference in thermal expansion history between the ceramic layer and the electrode layer in the obtained piezoelectric ceramic body (strain remains, the strength of the piezoelectric ceramic body deteriorates, and the adhesion strength between the electrode layer and the ceramic layer However, since it is not strong enough, it is not reliable enough to be used in functional elements that involve dynamic movement, such as piezoelectric elements.

In order to overcome these shortcomings, efforts have been made to mix ceramic powder into the electrode forming material and create small holes in the electrode pattern to increase adhesion strength, but these efforts have not produced the desired effect. .

A method using a ceramic electrode layer has also been proposed. A method of sintering a material with a BaTi0z (barium titanate) composition and a material with a semiconductive BaTiO3 composition has some effects, but Semiconductive BaTi0. In a combination of materials with the same composition, PB quickly diffuses into the material with the semiconductive l3aTiOz composition, so the conductive ceramic layer that is the electrode layer disappears (no longer has conductivity).
There is a problem.

[Purpose of the invention]

In view of the above circumstances, this invention eliminates the need for expensive electrode forming materials, eliminates the adhesion strength between the ceramic layer and the electrode layer, and eliminates the distortion associated with electrode layer formation, and is suitable for low voltage driving. The purpose of this invention is to provide a method for manufacturing a piezoelectric ceramic body having a multilayer structure.

[Disclosure of the invention]

In order to achieve the above object, the present invention provides a method for obtaining a piezoelectric ceramic body in which ceramic layers and electrode layers are alternately laminated, wherein the ceramic layers and porous layers serving as the electrode layers are alternately laminated. The gist of the present invention is a method for manufacturing a piezoelectric ceramic body, which comprises preparing a laminate and imparting conductivity to the porous layer.

The method for manufacturing the piezoelectric ceramic body according to the present invention will be described below.
A detailed description will be given of one embodiment thereof.

A piezoelectric ceramic calcined powder with a desired composition is mixed with a binder, plasticizer, and solvent as necessary.
Grind and slurry. The obtained slurry is made into a green sheet using a doctor blade method or an extrusion method, and this green sheet is cut into a desired size.

Next, a material for forming a porous layer that will become an electrode layer is applied onto this green sheet by screen printing. As the material for forming the porous layer, a paste made by adding a binder, a plasticizer, a solvent, and graphite powder for creating voids to piezoelectric ceramic calcined powder is used.

Graphite powder starts thermal decomposition at about 700°C and releases CO
It became 2 and he was eliminated. Amorphous carbon can also be used although its decomposition temperature is low. Multiple green sheets printed with a paste for forming a porous layer are stacked and bonded together by applying heat and pressure (thermocompression bonding). The thus obtained laminate (green chip) is sintered. The binder is gradually removed in air and then sintered at a temperature of about 1300°C. Once sintering is complete, the graphite is removed and the paste printing layer becomes a porous layer. In this way, a laminate in which ceramic layers and porous layers are alternately stacked is prepared.

Following sintering, the porous layer is rendered electrically conductive.

In this embodiment, a conductive material is impregnated into the porous layer to provide conductivity. A conductive substance is included in the resin liquid, and the resin liquid becomes conductive under reduced pressure. I.J.
impregnate the material into the pores. The porous layer imparted with electrical conductivity becomes an electrode layer. The conductive substance is carbon (C), Aj
! , Ag, Ni, Cu, anything is fine.
Different types of substances may be placed in the porous layer at the same time. Usually, the above-mentioned types of conductive substances are contained in the resin liquid in the form of fine particles. The resin liquid is also desirably an epoxy resin liquid with adhesive strength, but is not limited thereto. However, in the case of resin liquid, it tends to harden within the porous layer and increase the strength of the porous layer. Furthermore, it does not have to be a resin liquid, but any material that contains a conductive substance in a dispersed manner and can introduce the conductive substance into the porous layer may be used. After introducing the conductive resin liquid, heat treatment at about 100° C. may be further performed for curing.

In the above manner, as shown in FIG. 1, a piezoelectric ceramic body 1 in which ceramic layers 2 and electrode layers 3 are alternately laminated is obtained. This piezoelectric ceramic body 1
The thickness of the ceramic layer 2 or the thickness of the electrode layer 3 is determined depending on the thickness of the green sheet or the thickness of paste printing, and can be adjusted appropriately. However, considering that piezoelectric ceramics with a laminated structure are used for small-sized, low-voltage-driven functional elements, the thickness of the ceramic layer 2 is preferably about 50 to 300 μm because the thinner it is, the easier it is to displace. Also, it is better for the electrode layer 3 to be as thin as possible;
From the viewpoint of ensuring reliability, it is desirable to keep the thickness around 10Al.

As is clear from the above explanation, since the conductive material is placed in the porous layer between the sintered ceramic layers, the conductive material is not exposed to any high temperature.

Therefore, there is no need to use any expensive conductive material for electrodes. Since the porous layer is also made of a material similar to the ceramic layer, the problems of distortion and weak adhesive strength due to differences in thermal expansion coefficients are also solved. Therefore, even if the ceramic layer is made thinner and driven at a lower voltage, it still has sufficient strength. In other words, it can be made inexpensive and sufficiently reliable.

In addition, a laminate consisting of a ceramic layer and a porous layer is
J, (In order to perform JN, a plurality of green sheets with patterns for porous layers printed on them were stacked one on top of the other, and all the layers were sintered at the same time, but the method is not limited to this.

Pre-sintered ceramic layers are obtained by slicing a bulk sintered body or by sintering only green sheets, and porous layers are layered so that porous layers are alternately laminated on top of these ceramic layers. may be formed in a separate process. However, it is not easy to cut a very thin ceramic layer from a bulk sintered body or to handle a thin ceramic layer, and the number of steps increases. It is desirable to form the layers simultaneously. Further, conductivity may be imparted by a method other than impregnation.

Next, more specific examples and comparative examples will be shown.

(Example 1) Special grade reagents P bO1, Z r O2,
T IO2 is weighed, wet mixed and pulverized, filtered, and further calcined in an alumina crucible at a temperature of 850°C to obtain a calcined product. This calcined product is wet-pulverized, filtered and dried to obtain a calcined powder.

Next, to 100 parts by weight of this calcined powder, 8 parts by weight of polyvinyl butyral resin as a binder, 4 parts by weight of phthalate ester as a plasticizer, and 2 parts by weight of butanol as a solvent.
0 parts by weight and 50 parts by weight of trichlorethylene were mixed in a dispenser to form a slurry. This slurry was made into a thickness of 300 μm using the doctor blade method.
A green sheet was created. This green sheet 3
It was cut to the QB angle.

A porous material was prepared as follows. P
b Z r , 53T i , 7Q For a total of 100 parts by weight of 30 parts by weight of calcined powder and 70 parts by weight of graphite powder, 8 parts by weight of polyvinyl butyral resin as a binder and phthalic acid as a plasticizer. 4 parts by weight of ester, 25 parts by weight of butanol and 55 parts by weight of trichlorethylene as solvents were mixed in a dispenser to form a slurry.

This slurry (material for forming a porous layer) was applied to both sides of the green sheet by screen printing. The thickness was 20 μm. Stacking 50 printed green sheets at 100°C, 500kg/c
Thermocompression bonding was carried out at a pressure of 11.

Thereafter, the laminated green sheets were sintered as follows. The temperature was raised to 300°C at a rate of 100°C/hour, held at 300°C for 24 hours to degrease (remove binder, etc.), and then raised to 1260°C at a rate of 200°C/hour. , maintain this temperature for 1 hour,
Next, the temperature is lowered at a rate of 300°C/hour. In this case, the stacked green sheets are placed in a sagger made of MgO, but are surrounded by a dummy material made of the same piezoelectric ceramic to prevent evaporation of PbO. Also, when degreasing, leave the lid of the sagger pot open to allow air to flow in and out. In this way, a laminate in which ceramic layers and porous layers are alternately laminated is obtained. The thickness of the porous layer is 15μ
It was m.

Conductivity is imparted to the porous layer of this laminate. An epoxy resin containing Ag as a conductive substance (conductive epoxy resin N2762AB manufactured by Shoei Kagaku Kogyo ■) was diluted with butyl glycidyl ether to 200 cps (60 rp with a B-type viscometer).
The sintered laminate was submerged therein, the pressure was reduced to 10-3 torr, and the epoxy resin containing Ag was impregnated into the porous layer. After resin impregnation,
It was cured at a temperature of 100°C. After the resin had hardened, a polishing process was performed to remove the resin that had adhered to areas other than where it was needed, completing the piezoelectric ceramic body.

(Example 2) In Example 1, an epoxy resin containing C (carbon) as a conductive substance (conductive epoxy resin Dotite 5H3A manufactured by Fujikura Kasei ■) was used instead of the epoxy resin containing Ag as a conductive substance. , diluted thinner SH of the same resin
A piezoelectric ceramic body was completed in exactly the same manner as in Example 1, except that the viscosity was adjusted to 200 cps (6 Orpm using a B-type viscometer) by diluting the mixture.

(Example 3) Instead of epoxy resin containing Ag as a conductive substance,
Ni particles (particle size of 2 μm or less) are used as the conductive material, and Araldite AZ15 (C
IBA-GEIGY (manufactured by IBA-GEIGY) and a curing agent were mixed together so that the weight ratio of resin and Ni particles was about 1:2, and this mixture was diluted with acetone. The viscosity was adjusted to 200 cps (60 rpm using a B-type viscometer). After impregnating the porous layer with an epoxy resin containing N1, it was cured at a temperature of 180°C.

Other than that, a piezoelectric ceramic body was completed in the same manner as in Example 1.

(Comparative Example 1) PT paste (A-3444 manufactured by Engelhall) was applied to both sides of the 3Qii square green sheet obtained in Example 1 by screen printing. The thickness was 10 μm.

Fifty printed green sheets were stacked, thermocompression bonded at a temperature of 100°C and a press pressure of 500 kg/crA, and sintered under the same conditions as in Example 1 to complete a piezoelectric ceramic body.

The resistance values of the electrodes of Examples 1 to 3 and Comparative Example 1 were sufficiently low as 10' Ω·0ffl or less in terms of specific resistance.

The adhesion strength between the electrode layer and the ceramic layer was measured as follows. The completed piezoelectric ceramic body had a size of 25 m x 25 mm x 15 mm. From now on 2.
A piece with a size of 5mm x 2.5*nxl was cut out using a diamond cutter, and the bending strength in the direction parallel to the electrode layer and the fracture location were measured.

The results are as follows.

Example 1 Breaking strength: 830 kg/cut at the fracture location Ceramic interlayer Example 2 Breaking strength: 750 kg/cut at the fracture location Ceramic interlayer Example 3 Breaking strength: 950 kg/cnl at the fracture location Comparative example 1 between ceramic layers Breaking strength: 360,,/ant at the fracture location
Electrode-ceramic layer interface As is clear from the above measurement results, in the piezoelectric ceramic bodies of Examples 1 to 3, no peeling occurs at the electrode-ceramic layer interface, so the adhesion strength between the electrode layer and the ceramic layer is sufficiently strong. It can be seen that it is. Furthermore, the strength at which the breakage occurred was significantly greater than that of Comparative Example 1, indicating that no distortion occurred.

〔Effect of the invention〕

As described in detail above, the method for obtaining a piezoelectric ceramic body according to the present invention involves preparing a laminate in which ceramic layers and porous layers serving as electrode layers are alternately laminated, and It has a structure that provides conductivity.

Therefore, there is no need to use expensive conductive materials for electrode formation, and a piezoelectric ceramic body that can be driven at low voltage can be manufactured at low cost. Furthermore, since a porous layer that becomes an electrode layer is formed in the process before using the conductive material,
Since the ceramic layer and the porous layer can be laminated in a preferable manner regardless of the conductive material, the resulting piezoelectric ceramic body has high reliability.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a piezoelectric ceramic body manufactured by an embodiment of the piezoelectric ceramic body manufacturing method according to the present invention. 1... Piezoelectric ceramic body 2... Ceramic layer 3... Electrode layer Fig. 1

Claims (2)

[Claims] (1) In a method for obtaining a piezoelectric ceramic body in which ceramic layers and electrode layers are alternately laminated, a laminate in which the ceramic layers and the porous layers serving as the electrode layers are alternately laminated is prepared. . A method for producing a piezoelectric ceramic body, which comprises imparting conductivity to the porous layer. (2) A method for manufacturing a piezoelectric ceramic body according to claim 1, wherein conductivity is imparted by introducing a conductive substance into the porous layer by impregnation.