JPS61182285A - Electrostrictive effect element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an element having large mechanical strength by using paste containing mutually entangled massive whisker-shaped crystal grains as a base when internal electrode paste is applied onto an electrostrictive material green sheet consisting of electrostrictive material powder, an organic binder and an organic plasticizer and the green sheets are laminated while repeating the application of the internal electrode paste. CONSTITUTION:An extremely small quantity of an organic binder is added to electrostrictive material baking powder mainly comprising magnesium lead niobate and a titanate, and the mixture is dispersed into an organic solvent, thus producing slurry. The slurry is applied onto Mylar films and dried by employing a casting film forming device, and peeled, thus manufacturing green sheets 11, 12, etc. A platinum base to which whisker-shaped crystals 16 having 10wt% silicon nitride are added is kneaded so that an entangled state is not disintegrated, the base is scree-printed on the sheets 11, 12, etc. to form internal electrodes 13, and the bases and the sheets are hot-pressed alternately only by several hundred numbers and baked at 1,240 deg.C. Accordingly, the protruding crystals 16 are intruded into each sheet.

Description

Detailed Description of the Invention (Industrial Field of Application) The device and the manufacturing method of the present invention are applicable to electromechanical devices such as driving devices and minute displacement devices that utilize the electrical skewer mechanical energy conversion ability of piezoelectric or electrostrictive materials. It concerns force/cal devices.

(Prior Art) When classifying electrostrictive effect elements, it seems that there are two types, focusing first on their driving methods.

One is to precisely control minute force displacement at a relatively slow speed. An example of this would be a device that controls the direction of a mirror. The other type uses an electrostrictive element to generate vibrations with a relatively large amplitude and a considerable frequency, and uses the kinetic energy of the vibrations. In this case, the element is used by incorporating it into some kind of mechanical force displacement amplifying mechanism. An example of this is an impact type printer head.

(Problem to be Solved by the Invention) In the former case, the force applied to the element K is usually weak, so the mechanical strength of the element is not much of a problem. On the other hand, in the latter case, various impulse types of forces such as compressive force, tensile force, bending force, twisting force, etc. are applied to the element. Naturally, an element with high mechanical strength is required. In an internal electrode type electrostrictive effect element, the weakest part is the interface between the electrostrictive ceramic material and the internal electrode material metal. Usually, several tens to hundreds of layers of internal electrodes are embedded inside the device, so the tensile strength and bending strength of the device are mainly weakened due to the weak bonding force at the interface.

FIG. 8 is a sectional view of a conventional internal electrode type electrostrictive effect element. A large number of internal electrodes are embedded in the longitudinal direction of the element, and therefore there are many interfaces where the bonding force between the internal electrodes and the electrostrictive ceramic material is weak.

Therefore, the bending strength of the element is about 40% to 60 inches of the bending strength of the electrostrictive ceramic material. When performing a destructive test to measure bending strength, the internal electrode and the electrostrictive ceramic material crack at the interface. FIG. 9 is an external view showing the bending strength test of the element. FIG. 10 is an external view showing the state of destruction of the element in the bending strength test of the element.

In the figure, numbers 11 and 12 indicate electrostrictive materials, and 13 indicates internal electrodes. 15 indicates the support stand of the 14-digit bending strength tester as well.

The mechanical strength of the element is not much of a problem. On the other hand, in the latter case, various impulse types of forces such as compressive force, tensile force, bending force, twisting force, etc. are applied to the element. Naturally, an element with large mechanical strength is required. In an internal electrode type electrostrictive effect element, the weakest part is the interface between the electrostrictive ceramic material and the internal electrode material metal. Usually, several tens to hundreds of layers of internal electrodes are embedded inside the device, so the tensile strength and bending strength of the device are mainly weakened due to the weak bonding force at the interface.

To solve this problem, we created a fine mesh structure for the internal electrode layer to create bonds between the ceramic particles on both sides of the electrode.
Attempts have been made to improve the bonding force at the interface by introducing glass or ceramic particles of other compositions into the internal electrodes, but these efforts have not been satisfactory.

A first object of the present invention is to provide an internal electrode type electrostrictive effect element that has high mechanical strength and therefore does not break mechanically even when driven with large vibrations and high frequencies.

A second object of the present invention is to provide a method for manufacturing an internal electrode type electrostrictive effect element with significantly increased mechanical strength.

(Means for Solving the Problems) First, the first invention is an electrostrictive effect element having a laminate in which electrostrictive material layers and internal electrode layers are alternately laminated. This is an electrostrictive effect element having a large number of whisker-like crystal particles arranged so as to span both the internal electrode layer and the internal electrode layer.

A second invention is a method for manufacturing an electrostrictive effect element comprising a step of applying an internal electrode paste on an electrostrictive material green sheet comprising an electrostrictive material powder, an organic binder, and an organic plasticizer. The present invention is characterized by the use of an internal electrode paste that is made of a material that is less reactive to the metal material for the electrodes and that contains lump-like whisker-like crystals or needle-like crystals that are entangled with each other.

(Function) As a method of improving the bonding force at the interface, it is conceivable to introduce a large number of whisker-like crystals or needle-like crystals penetrating the internal electrode layer to bond the electrostrictive material ceramics on both sides. FIG. 4 is a sectional view of an electrostrictive effect element having such a force structure. The electrostrictive ceramic material on both sides is bonded by whisker-like crystals that are slightly longer than the thickness of the internal electrode layer and run vertically through the structure.

Number 16 in the figure indicates a whisker-like crystal.

The first possible method for realizing such a structure is to disperse and knead whisker-like crystals with good dispersibility in the internal electrode paste in advance. However, with this method, when the paste is applied to the electrostrictive material green sheet, the whiskers are oriented along the applied surface. Even if it is fired after lamination and compression, it is oriented parallel to the internal electrode layer and is useful for improving the strength of the device. FIG. 5 is a cross-sectional view of a green sheet containing electrostrictive material powder coated with an internal electrode paste containing whisker-like crystals with good dispersibility. Figure 6 shows how many green sheets are stacked together.
7 is a cross-sectional view of an electrostrictive effect element produced by cutting after firing. In the figure, numeral 17 indicates a green sheet containing electrostrictive material powder, 18 indicates internal electrode paste, and 19 indicates whisker-shaped crystals with good dispersibility. It is clear that such a force structure does not significantly improve the element strength.

Therefore, it is effective to use so-called entangled whisker-like crystals as a method for orienting part of the whisker-like crystals perpendicularly to the internal electrode layer. In the production of whiskers, various conditions may cause the whiskers to be poorly separated and stuck to each other, resulting in so-called tangles. If this aggregate of whisker-like crystals is used, some of the whiskers will be oriented perpendicularly to the internal electrode layer, which will help improve the strength of the device.

Figure 7 is a cross-sectional view of a green sheet coated with an inner chamber "pole paste" containing aggregates of tangled, lumpy, whisker-like crystal particles. Figure 1 shows a large number of these green sheets stacked, pressed together, and fired. It is a cross-sectional view of an electrostrictive effect element produced by cutting.No. 20 in the figure shows a whisker-like crystal in which entanglement has occurred.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

Adding a small amount of organic binder to electrostrictive material pre-fired powder whose main components are magnesium lead niobate and lead titanate A
'i A slurry dispersed in an organic solvent was prepared. This slurry is applied onto a Mylar film to a thickness of about 100 microns using a casting film forming apparatus commonly used in the manufacture of multilayer ceramic capacitors and dried. This is peeled off from the film to obtain an electrostrictive material green sheet.

Next, the whisker-like crystals used will be described.

The whiskers are silicon nitride whiskers with a diameter of 02 μm and a length of approximately 1
A lumpy and tangled material with a diameter of 0 μm was used.

The reason for using silicon nitride is that it has low reactivity with electrostrictive ceramics and internal electrode materials that will be described below.

Strong strength. Thermal expansion must be appropriate.

This silicon nitride whisker was added to the platinum paste at 10 w.
Add only t% and knead without disturbing the entangled state too much. The internal electrode paste thus obtained is screen printed on the electrostrictive material green sheet. Several hundred sheets of this green sea) are stacked, pressed together by a hot press, and then fired at 1240° C. to obtain an electrostrictive material laminate. This is cut into element shapes. FIG. 1 is a cross-sectional view of the electrostrictive element produced in this manner. The number 20ij in the figure is a lumpy, whisker-like crystal grain with entanglements.

The bending strength of this element was measured using a conventional three-point bending strength tester. The measured value was 900 KP/cd, which was 90% of the electrostrictive material ceramic's own value of 1000 Ky/cd. In addition, no breakage occurred at the interface between the Hiko internal electrode and the electrostrictive material as in the conventional case. FIGS. 2 and 3 show a cross-sectional view of the device and element in a bending strength test, and a cross-sectional view showing the state of destruction thereof. In the figure, numbers 11 and 12 indicate electrostrictive materials, and 13 indicates internal electrodes. 14 is a support stand 15Fi
Showing knife edge. 20 indicates entangled whisker-like crystals.

(Effects of the Invention) The element of the present invention has greatly improved mechanical strength, which is a drawback of internal electrode type electrostrictive elements, and has achieved 90% of the strength of the electrostrictive material itself. Furthermore, if a chemically stable, high-temperature-resistant, and high-strength material such as silicon nitride whiskers is used, it is a highly versatile method that can be applied to all conventional electrostrictive materials, ceramics, and metal materials for internal electrodes.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the electrostrictive effect element of the present invention. FIG. 2 is an external view showing the bending strength test of the device. FIG. 3 is an external view showing how the device breaks down in the bending strength test of the device. FIG. 4 is a cross-sectional view of an internal electrode type electrostrictive effect element having a large number of whisker-like crystals penetrating the internal electrode layer. FIG. 5 is a cross-sectional view of an internal electrode paste containing whisker-like crystals with good dispersibility applied onto a green sheet containing electrostrictive material powder. FIG. 6 is a sectional view of an electrostrictive effect element manufactured by laminating a large number of Green Sea 1rs shown in FIG. 5, press-bonding them, firing them, and then cutting them. FIG. 7 is a cross-sectional view of a green sheet coated with an internal electrode paste containing agglomerated whisker-like crystal particles. FIG. 8 is a sectional view of a conventional electrostrictive effect element. FIG. 9 shows a cross-sectional view of an apparatus and an element used in a conventional bending strength test of an electrostrictive element. FIG. 10 is a cross-sectional view showing how the element breaks down in the same bending strength test. In the figure, numbers 11 and 12 are electrostrictive materials, 13 is an internal electrode, and 14
．． 15 is a support base and knife, 16, 19U Wiss force-shaped crystal particles, 17 is a green sheet, 18 is an internal electrode paste, 20 is a lumpy tangled whisker shape 11 electrostrictive material 12 electrostrictive material 13 internal electrode 20 whisker Crystal in the form of m-~ N ~ SaN N 11 Electrostrictive material 12 Electrostrictive material 13 Internal electrode 16 Whisker-shaped crystal \NoOCy> 11 Electrostrictive material 12 Electrostrictive material 13 Internal electrode 19 Whisker-shaped crystal 11 Electrostrictive material 12 electrostrictive material

Claims (2)

[Claims] (1) It has a laminate in which electrostrictive material layers and internal electrode layers are alternately laminated, and has a plurality of whisker-like crystal particles arranged across both the electrostrictive material layer and the internal electrode layer. An electrostrictive effect element characterized by: (2) In a method for manufacturing an electrostrictive effect element comprising a step of applying an internal electrode paste on an electrostrictive material green sheet comprising an electrostrictive material powder, an organic binder, and an organic plasticizer, the electrostrictive material and the internal electrode A method for producing an electrostrictive effect element, characterized in that an internal electrode paste is made of a material that is less reactive with respect to the metal material used for the electrostrictive element, and further includes lump-like whisker-like crystal particles or needle-like crystal particles entangled with each other.