JPS58196079A - Electrostrictive effect element - Google Patents

Abstract

PURPOSE:To increase the adhesion strength by a method wherein ceramics material sintered at a low temperature is used as internal electrodes beside metallic constituents, in an electrostrictive effect element having the ceramics material showing electrostrictive effect and the internal electrodes. CONSTITUTION:The paste which turns the internal electrode 2 is printed over a film of the electrostrictive material 1 composed of lead magnesiumniobate and lead titanate by a screen printing method. As the material for the electrode 2, the mixture of the platinum paste and ceramics powder is used. For this powder, that which can be sintered at a temperature lower than that for the electrostrictive material 1 is used. Next, the material 1 whereon the electrode 2 is printed is instered. Then, the electrodes 2 are connected by lead wires 3, and thus the electrode terminals A and B are taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer ceramic capacitor type electrostrictive element.

An electrostrictive effect element is an element that generates mechanical strain by applying voltage to a material that exhibits a large electrostrictive effect.

There are two types of electrostrictive effects: a longitudinal effect and a transverse effect. When strain occurs in a direction parallel to the electric field, it is called a longitudinal effect, and when strain occurs in a direction perpendicular to the electric field, it is called a transverse effect.

And in general, the vertical effect is larger. In order to generate a large strain at low voltage using the longitudinal effect, the distance between opposing electrodes provided on a material exhibiting an electrostrictive effect may be shortened. However, simply shortening the distance between the electrodes cannot increase the total amount of displacement even if the strain can be increased. In order to improve this drawback and obtain a large amount of displacement at low voltage, a multilayer ceramic capacitor type structure has been proposed.

Figure 1 (a) and (bl) show an example of the structure of the electrostrictive effect element having the above-mentioned laminated ceramic capacitor type structure, which was proposed by E!A et al. The porcelain material I and the internal electrode 2 are alternately laminated, and the lead I
fij3 shows a state in which each internal electrode is electrically connected every other layer.

Figure 1 (ml is a side view of the element, and Figure 1 (b) shows the internal electrodes that have the same shape as the cross section of the element. When a direct current bias is applied between electrode terminals A and B, this element In an element having such a structure, it is easy to set the distance between the electrodes to several micrometers to several 10 micrometers at 8 degrees, and the height l can be increased by increasing the number of stacked layers.

Therefore, it becomes an electrostrictive element that can obtain a large amount of displacement with a low voltage.

However, metal materials such as platinum and palladium are usually used as materials for internal electrodes, but these metal materials generally do not cause chemical reactions with porcelain materials that exhibit electrostrictive effects, so the bond between the internal electrodes and the porcelain is strong. Usually, it is not strong. Therefore, if the electrostrictive effect element is greatly deformed or if it is driven intermittently for a long period of time, it may be mechanically destroyed at the bonding surface between the internal electrode and the ceramic material.

The purpose of the present invention is to increase the adhesive strength between the internal electrodes and the i-shape, and to extend the life of an electrostrictive element in which internal electrodes and ceramics are alternately laminated until mechanical breakdown occurs. In a four-way laminated porcelain capacitor, the same porcelain powder as the electric porcelain of the capacitor is mixed into the internal electrode to approximate the coefficient of thermal expansion of the internal i-electrode and the porcelain. A method for suppressing the occurrence is known, and in this case, it has been reported that another effect is an increase in the adhesive strength between the internal electrode and the porcelain. (% Kaisho 56-1628
21) However, it is completely unclear whether such an internal electrode is effective in an electrostrictive element having a structure as shown in FIG. 1, in which mechanical displacement is repeated in the stacking direction.

That is, the present inventors have developed an electrostrictive element having a structure in which ceramic materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated, and the internal electrodes are connected every other layer. In addition, by using an internal electrode mixed with porcelain material powder that is sintered at a lower temperature than the porcelain material constituting the element, it is possible to construct the element in the internal electrode more easily than when using the conventional internal electrode as it is. It has been discovered that even when the same powder as used in porcelain is mixed in, the lifespan of the electrostrictive element until mechanical destruction can be significantly improved. When porcelain material powder that is sintered at a lower temperature than the porcelain material constituting the electrostrictive element is mixed into the internal electrode, part or all of the porcelain powder in the electrode becomes a liquid phase during firing. Compared to the case where the same powder as the porcelain constituting the element is mixed, diffusion becomes easier and the adhesion between the internal electrode and the porcelain increases.

The present invention will be described in detail below according to Examples.

Example Magnesium lead niobate pb (Mg, /sNb, l) 0. and lead titanate PbTi
The effects of the present invention were experimentally verified using a 0° solid solution.

Pb (Mg, , Nb, , ) 0. and PbT10.
The starting raw material powder was weighed so that the molar ratio was 65:35, and calcined at 800°C for 2 hours. An appropriate amount of organic binder was mixed with this calcined powder and dispersed in an organic solvent to obtain a slurry. The slurry was applied onto the Shimmerer film to a thickness of several 100 microns by a doctor blade method and then dried. After this green sheet was peeled from the Mylar film, it was cut into a predetermined size and a paste that would become the internal electrodes was printed using a screen printing method. As the material for the internal electrodes, a mixture of platinum paste and 25 weight percent of porcelain powder was used. The porcelain powder to be mixed into this platinum paste is Pb (Mg, , Nb, , ) 0.
The calcined powder is a mixture of PbTiO3 and PbTiO3 in a molar ratio of 9:1. This composition has the characteristic that it can be sintered at a temperature approximately 80° C. lower than the 65:35 composition mentioned above.

Next, the films printed with the electrode paste were stacked and integrally molded using a hot press, and then sintered at a temperature of 1280° C. for 1 hour. After sintering, it was cut into the shape shown in Figure 1 above. The dimensions of the obtained element are a-3msJx in Figure 1.
The distance between each internal electrode at lOim is 250 microns. The internal electrodes formed in a layered manner are connected in a layered manner with a TTCV-D wire, two electrode terminals A and B are taken out, and a half-wave rectified sine wave with a maximum voltage of 400 V and a frequency of 1000 Hz is generated. A life test of the device was conducted by applying a pulse. Further, an electrotactic strain effect element was prepared in the same manner using platinum paste mixed with calcined song having the same composition as the FF1 material constituting the element as the internal electrode material, and a life test was conducted in the same manner. FIG. 2 shows the relationship between the number of pulses applied until these electrostrictive elements reach mechanical breakdown and the amount of porcelain powder mixed into the internal electrodes.

In Fig. 2, 1 indicates Pb (Mg, , Nb, , )Ol and PbT, which are sintered at a lower temperature than the porcelain materials constituting the element.
Characteristics when using an electrode material mixed with a porcelain material calcined powder bed with a molar ratio of 9 to l with i0°, 1 sound '2
is the characteristic when using an electrode material in which the same calcined powder bed as the porcelain material constituting the element is mixed. As is clear from FIG. 2, when the method of the present invention is applied, the bonding strength between the internal electrode and the ceramic material is strengthened, and the life of the electrostrictive element is greatly extended. Further, it is desirable that the amount of porcelain powder mixed into the internal electrode paste at the time of preparation is 40% by weight or less. If more than this amount is mixed, the displacement of the element tends to decrease somewhat. Further, the particle size of the A-type powder is preferably 1 to 2 μm or less.

[Brief explanation of drawings]

Figure 1) and (b) show an example of the structure of an electrostrictive element in which materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated. In the figure, number 1 indicates a material exhibiting an electrostrictive effect, 2 indicates an internal electrode, and 3 indicates a lead wire that electrically connects the internal electrodes. FIG. 2 is a diagram showing the relationship between the amount of porcelain powder mixed into the internal electrode and the element life in the electrostrictive effect element having the structure shown in FIG. 1. Fang l Fig. 2 0 10 20 30 i counter*
Spun and combined tatami (weight%)

Claims (1)

[Claims] In an electrostrictive element having a structure in which ceramic materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated and the internal electrodes are connected every other layer, the internal electrodes include a main component other than the ceramic material. An electrostrictive effect element characterized by using an internal electrode mixed with porcelain material powder that is sintered at low temperatures.