JPH0828540B2 - Electrostrictive ceramic material body and polarization operating method thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electrostrictive ceramic material body and a polarization operating method thereof, and more particularly to a lateral effect by one integral electrostrictive ceramic material body itself. The present invention relates to an improvement for causing the bending mode to be deformed by vibration due to, and a polarization operation method for obtaining such an electrostrictive ceramic material body.

[Prior Art] Conventionally, actuators utilizing the electrostrictive effect have been used in fields such as relays, fans, pumps, and VTR tracking. Typically, such an actuator has a unimorph structure in which a lateral effect electrostrictive material plate is bonded to a metal plate, or two electrostrictive material plates are bonded via a metal plate. It is known that it has a bimorph structure.

By the way, it has been a long time since a specific ceramic material was found to exhibit an electrostrictive effect, but such an electrostrictive ceramic material does not exhibit an electrostrictive effect as a whole when it is simply fired. Because, as shown by the arrow in FIG. 11, the spontaneous polarization in the ceramic material in the stage just fired, when viewed on the grain scale, is oriented in all directions due to the structure of the grains and domains, This is because the directions of these spontaneous polarizations cancel each other out.

Therefore, when the electrostrictive ceramic material body is used as the actuator described above, for example, as shown in FIG. 12, electrodes 1 and 2 are attached to the upper and lower surfaces thereof, and a high electric field is applied through these electrodes 1 and 2. Must be applied to perform polarization processing for aligning the polarization direction in one direction.

[Problems to be Solved by the Invention] However, as can be seen from FIG. 12, the mode of the overall polarization applied to the electrostrictive ceramic material body is substantially the same between the paired electrodes 1 and 2. It is like. Therefore, in such an electrostrictive ceramic material body, for example, an electrode
Even if the drive voltage is applied via 1 and 2, only the longitudinal effect vibration is applied in the direction of the electric field application. Further, when viewed in a direction perpendicular to the direction of application of such an electric field, only lateral effect vibration is applied. The point is that a single plate alone does not bend. Therefore, when constructing an actuator that performs the bending mode deformation as described above, be sure to use a unimorph structure in which a metal plate or another electrostrictive ceramic material body and a metal plate are combined with an electrostrictive ceramic material body. Or it must have a bimorph structure.

Thus, the conventional unimorph structure or bimorph structure actuator always involves adhesion between the ceramic material and the metal. Then, this adhesion causes the following problems.

First, due to the difference in the coefficient of thermal expansion between a metal and a ceramic material, deformation may occur only due to a temperature change. Since such deformation occurs regardless of the application of the driving electric field, the precision with respect to the deformation amount is lowered.

In addition, during the deformation in the bending mode, stress concentrates near the adhesive layer, thereby causing cracks in the electrostrictive ceramic material or peeling between the metal plate and the electrostrictive ceramic material. May be caused.

Further, it is relatively difficult to make not only the adhesive strength at the adhesive portion of one actuator but also the overall adhesive strength between the actuators as a whole. Therefore, an actuator with extremely low mechanical strength may be obtained, or an actuator with an extremely small displacement amount may be obtained. In this case, the characteristics must be individually grasped in advance, which complicates a preliminary operation for using the characteristics.

Also, due to the temperature characteristics of the adhesive used for bonding,
The characteristics of the actuator also change. In particular, the upper limit temperature of the actuator is determined by the properties of the adhesive, which also results in limiting the range of use of the actuator.

As an actuator that operates on substantially the same principle as the above-described actuator having a bimorph structure, an actuator made of a ceramic material integrally formed after forming an internal electrode has been proposed. However, in this case, a noble metal capable of withstanding the firing temperature of the ceramic has to be used as the internal electrode, which causes an increase in cost.

Therefore, the present invention intends to provide an electrostrictive ceramic material body which is not only costly but also has high mechanical and thermal reliability and which is suitable for use as a lateral effect actuator. It is a thing.

Further, the present invention is intended to provide a polarization operating method for advantageously obtaining an electrostrictive ceramic material body capable of satisfying the above-mentioned demands.

[Means for Solving Problems] An electrostrictive ceramic material body according to the present invention is made of an integrally sintered ceramic material having a dimension in the thickness direction and exhibiting an electrostrictive effect. , It is not necessary to form internal electrodes. Then, in order to solve the above-mentioned technical problem, the electrostrictive ceramic material body has at least one of the degree of polarization orientation as a whole and the direction of polarization as a whole when viewed in the thickness direction in at least a part thereof. Are different from each other in the first and second regions dividing the thickness direction.

In the electrostrictive ceramic material body made of the integrally sintered ceramic material as described above, the aspect of polarization when viewed in the thickness direction is made different in the first and second regions dividing the thickness direction. As a method of operating the polarization of, the first property is that the ease of polarization varies depending on the temperature condition given to the electrostrictive ceramic material body.
And the second method which utilizes the property of depolarizing the electrostrictive ceramic material body once subjected to polarization treatment when a high temperature above the Curie point is applied.

In both the first and second methods, first, an electrostrictive ceramic material body having a dimension in the thickness direction and made of an integrally sintered ceramic material that exhibits an electrostrictive effect by a polarization operation is prepared.

Next, in a first method, a first method of dividing the thickness direction in at least a part of the electrostrictive ceramic material body is performed.
The first electric field is applied to the second region in the thickness direction while providing the temperature difference in which the former is higher than the latter, whereby the degree of polarization orientation as a whole of the first region is increased. And, at least one of the directions of polarization as a whole is changed more than the second region.

In the first method, the electrostrictive ceramic material body used in the step of applying the first electric field may include the following two types. The first is that, at least in part, a second electric field directed in a direction opposite to the first electric field is previously applied, whereby the polarization of the entire part to which the second electric field is applied is polarized. Is already oriented in one direction in the thickness direction. On the other hand, the second one is one which is not subjected to any polarization treatment after the stage of being integrally sintered. In this case, by applying the first electric field,
The direction of polarization as a whole of the first region is oriented in one direction in the thickness direction.

On the other hand, in the second method, after preparing the electrostrictive ceramic material body described above, (1) at least a part of the electrostrictive ceramic material body,
Applying an electric field directed in the thickness direction, thereby directing the polarization direction of the entire portion to which the electric field is applied to one direction in the thickness direction, (2) the direction of the overall polarization is One of the electric field ceramic material body having a portion oriented in one thickness direction,
Of the first and second regions that divide the thickness direction,
Applying a high temperature equal to or higher than the Curie point only to the first region, thereby changing the degree of polarization orientation as a whole of the first region.

[Operation and Effect of the Invention] According to the electrostrictive ceramic material body of the present invention, when viewed in the thickness direction, the degree of polarization orientation as a whole in the first and second regions dividing the thickness direction. Since the modes of polarization as a whole, such as the direction of polarization as a whole and the direction of polarization as a whole, are different from each other, when a predetermined driving electric field is applied in the thickness direction of such an electrostrictive ceramic material body, it expands and contracts due to the lateral effect. Degree or direction is first
And the second region can be different from each other. Therefore, it is possible to construct an actuator that deforms in a bending mode only by using the electrostrictive ceramic material body alone.

As described above, since the electrostrictive ceramic material body that can constitute the actuator alone does not have an adhesive portion, all the conventional problems caused by the use of the adhesive agent or the presence of the adhesive layer can be solved. That is, the inconvenience of deformation due to temperature change even when no electric field is applied is eliminated. Further, when the deformation is caused, stress is concentrated in the vicinity of the adhesive layer, thereby causing cracks in the electrostrictive ceramic material body or causing peeling between the metal plate and the electrostrictive ceramic material body, Problems such as are solved. Furthermore, since the electrostrictive ceramic material is sintered integrally, the mechanical strength is increased, and such a variation in mechanical strength can be reduced. In addition, variation in deformation or displacement characteristics among products can be suppressed, and deterioration of such characteristics due to a temporal change in the deformation or displacement characteristics or repetition of the deformation or displacement can be reduced. Further, since the operating temperature range is not limited by the adhesive or the like, the operating temperature range can be expanded to a wider range, that is, to a higher temperature.

Therefore, when the electrostrictive ceramic material according to the present invention is used as an actuator, high reliability can be obtained.

Further, according to the method for operating the polarization of the electrostrictive ceramic material body according to the present invention, in the electrostrictive ceramic material body made of the integrally sintered ceramic material without using the internal electrode, the first direction is divided. And, in the second region, the respective polarization modes as a whole can be different from each other. Therefore, there is no increase in cost due to the formation of the internal electrodes, and the electrostrictive ceramic material having such a special polarization mode can be efficiently obtained.

In particular, in the polarization operation method according to the present invention, a two-step polarization operation, that is, an electric field oriented in the thickness direction is applied to the electrostrictive ceramic material body, whereby the direction of polarization as a whole is adjusted in this thickness direction. After turning in the direction
An electric field directed in the direction opposite to the above-mentioned electric field is applied to the thickness direction while applying a temperature difference in which the former is higher than the latter to the first and second regions dividing the thickness direction, whereby the first The direction of the overall polarization of the first region is made opposite to the direction of the previous polarization, and the directions of the overall polarization of the first and second regions are both directed in the thickness direction but opposite to each other. When the electrostrictive ceramic material body is used as an actuator, a large amount of deformation or displacement with respect to the magnitude of the driving electric field can be obtained.

[Embodiment] An electrostrictive ceramic material body as one embodiment of the present invention and a method of operating polarization thereof will be described with reference to FIGS. 1 to 3.

First, as shown in FIG. 2, an electrostrictive ceramic material body 10 having a dimension in the thickness direction and made of an integrally sintered ceramic material that exhibits an electrostrictive effect by a polarization operation is prepared. When the electrostrictive ceramic material body 10 is prepared, the direction of spontaneous polarization is completely random, as shown in FIG. 11 described above.

Next, in order to apply an electric field in the thickness direction of the electrostrictive ceramic material body 10, electrodes 11 and 12 are formed on the upper and lower surfaces of the electrostrictive ceramic material body 10. When a voltage is applied via these electrodes 11 and 12, the polarization directions are aligned in one direction as shown in FIG. Such a polarization mode as shown in FIG. 12 will be simply represented by an arrow 13 shown in FIG. That is, in FIG.
In the electrostrictive ceramic material body 10, the polarization direction as a whole is oriented in one direction in the thickness direction.

Next, as shown in FIG. 3, the electrostrictive ceramic material body 10
Are sandwiched by the heating head 14 and the cooling head 15. Although not shown, the heating head 14 has a built-in heater or a pipe for passing a heating medium, and the like, and the cooling head 15 has a built-in pipe for passing a cooling medium such as liquid nitrogen, and is further provided with a radiator plate. Good. In the state of FIG. 3, when the electrostrictive ceramic material body 10 is viewed in the thickness direction, the first and second regions 16 that divide the thickness direction are divided.
For and 17, the temperature difference that the former is higher than the latter is given. Then, while maintaining this state, the electrostrictive ceramic material body 10 from the polarization power source 18 via the electrodes 11 and 12.
An electric field is applied in the thickness direction of the. This electric field is applied in a direction that causes polarization in a direction opposite to the polarization direction indicated by the arrow 13 in FIG. When an electric field is applied in this manner, it is likely that the polarization mode is affected thereby.
It is the first region 16 on the higher temperature side. Therefore, in the first region 16, the polarization direction is reversed as shown by the arrow 19 shown by the dotted line. Second region on the low temperature side
At 17, an arrow pointing in the same direction as arrow 13 in FIG.
The polarization direction indicated by 20 is maintained.

In addition, as shown in FIG. 3, the conditions for reversing the polarization direction only in the first region 16 are as follows:
The electric field strength applied between the first and the second regions, the temperature difference between the first region 16 and the second region 17, the polarization operation time, and the like are parameters, and the ceramic that constitutes the electrostrictive ceramic material body 10 is also a parameter. It also depends on the material.

An electrostrictive ceramic material body 10 obtained through the steps shown in FIG. 3 is shown in FIG. As can be seen from the arrows 19 and 20 shown in FIG. 1, the first and second regions 16 and 17 of the electrostrictive ceramic material body 10 have their respective polarization directions both oriented in the thickness direction. It is said that they are opposite to each other. Thus, for example, electrode 1
When a driving voltage is applied via 1, 12, the bending mode is deformed due to the lateral effect of each of the first and second regions 16 and 17.

In addition, in the step of FIG. 3, when the polarization power supply 18 is applied to the electrostrictive ceramic material body 10, and when the heating head 14 and the cooling head 15 are made of a conductive material, the heads 14 and 15 are passed through these heads 14 and 15. An electric field for polarization may be applied. In this case, for example, electrodes 11 and 12 may not be formed.

The displacement characteristics of the actuator configured by using the electrostrictive ceramic material body obtained as described above will be compared with the conventional actuator having a laminated bimorph structure.

First, when the displacement amount with respect to the applied voltage was measured for the cantilever structure actuator having a thickness of 0.5 mm and an effective length of 25 mm, the results shown in FIG. 4 were obtained. In FIG. 4, the solid line shows the embodiment of the present invention, and the dotted line shows the conventional example. As can be seen from FIG. 4, the actuator according to the present invention exhibits a displacement amount substantially equal to or slightly larger than that of the conventional actuator, and is improved to 1/2 to 1/3 in terms of variation.

Also, comparing the change in displacement characteristics due to AC voltage drive,
The results are shown in FIG. In FIG. 5, the solid line shows the characteristics of the actuator according to the embodiment of the present invention, and the dotted line shows the characteristics of the conventional example. As can be seen from FIG. 5, the actuator according to the present invention is less deteriorated in displacement characteristics than the conventional example, and is also small in terms of variations.

6 and 7 are views corresponding to FIG. 1 showing another embodiment of the present invention.

In these embodiments, the degree of overall polarization orientation in the first and second regions 16 and 17 of the electrostrictive ceramic material body 10 is different from each other. In the embodiment shown in FIG. 6, the first region 16 as a whole does not exhibit piezoelectricity,
On the other hand, the second region 17 is polarized, as indicated by the arrow 21, and thus exhibits an overall piezoelectricity. Also,
In the embodiment shown in FIG. 7, the first area 16 has a small arrow.
22 is shown, and a thick arrow 23 is shown in the second area 17. As shown schematically by these arrows 22 and 23, in this embodiment the first and second regions 16 and 17 are
Although the direction of polarization in is the same, the degree of polarization orientation as a whole is larger in the second region 17 shown by the thick arrow 23.

In order to obtain the electrostrictive ceramic material body 10 of each embodiment shown in FIGS. 6 and 7, the polarization operation method as shown in FIG. 8 is carried out. That is, the electrostrictive ceramic material body 10
Are sandwiched between the heating head 24 and the cooling head 25. Incidentally, in a stage before being brought between such heads 24 and 25, the electrostrictive ceramic material body 10 is
It has a polarization mode as shown in the figure. Then, in FIG. 8, the heating head 24 is applied only to the first region 16 so as to give a high temperature above the Curie point, while the second region 17 is applied.
In, the cooling head 25 operates to avoid the temperature rise. When the electrostrictive ceramic material body 10 is exposed to such conditions, depolarization occurs in the first region 16 and, for example, the electrostrictive ceramic material body 10 as shown in FIG. 6 is obtained.

By controlling the heating temperature or time in the depolarization operation shown in FIG. 8, the depolarization in the first region 16 can be partially caused. In this case, in FIG. It is possible to obtain the electrostrictive ceramic material body 10 having the polarization mode as shown in FIG.

Further, in the initially extended embodiment, a partial depolarization operation step as shown in FIG. 8 may be carried out before the polarization operation shown in FIG. 3 is carried out.

Further, the electrostrictive ceramic material body 10 having the polarization mode shown in FIG. 6 has the heating head 14 and the cooling head shown in FIG.
It is also possible to create it by using 15 and the polarization power supply 18. That is, in FIG. 3, the electrostrictive ceramic material body 10 sandwiched by the heating head 14 and the cooling head 15 is, for example, a material after simple firing in which the spontaneous polarization shown in FIG. 11 is oriented in all directions. What has not been subjected to any polarization treatment may be used. by this,
When the polarization operation shown in FIG. 3 is performed, the polarization direction as indicated by the arrow 19 is given only in the first region 16 in this drawing, and in the second region 17, the polarization direction remains unpolarized because of the low temperature. Keep the state of. Therefore, as a result, a polarization mode substantially similar to that of the electrostrictive ceramic material body 10 shown in FIG. 6 can be realized.

Further, by appropriately selecting the heating and cooling conditions, the intensity of the electric field for polarization, etc., the electrostrictive ceramic material body 10 having the polarization mode as shown in FIG. 7 can also be obtained by the method shown in FIG. Can be obtained by

In the electrostrictive ceramic material body according to the present invention, when viewed in the thickness direction in at least a part thereof, at least one of the degree of polarization orientation as a whole and the direction of polarization as a whole divides the thickness direction into first and It is a condition that they are different from each other in the second region, and in regard to the direction orthogonal to the thickness direction, no matter how the polarization mode is the same or how it changes, in defining the scope of the present invention. Irrelevant. In this sense, Figures 9 and 10
The embodiments shown in the drawings are also within the scope of the present invention.

In FIG. 9, the first and second regions 16 and 17 are shown.
In each of the above, when viewed in a direction orthogonal to the thickness direction, the degree of polarization orientation changes, as schematically shown by arrows 26, ..., 27 and 28 ,.

Further, in the embodiment shown in FIG. 10, when viewed in a direction orthogonal to the thickness direction, the region 3 that does not exhibit piezoelectricity as a whole
0, 31, 32 exist, and when viewed in the thickness direction only partially, at least one of the degree of polarization orientation and the polarization direction divides the thickness direction into first and second regions 16
And 17 are different from each other.

The distribution state of the polarization mode in the direction orthogonal to the thickness direction is not directly related to the gist of the present invention.
Further modifications could be made other than the embodiment shown in Figures and 10.

Although no specific examples have been given as the electrostrictive ceramic material having the electrostrictive effect used in the present invention, it goes without saying that conventionally known electrostrictive ceramic materials can be applied to the present invention.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an electrostrictive ceramic material body 10 according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing the electrostrictive ceramic material body 10 in a state where the direction of polarization as a whole is directed in one direction in the thickness direction.
FIG. 3 is a diagram for explaining one step of a method for obtaining the electrostrictive ceramic material body 10 shown in FIG. 1 from the electrostrictive ceramic material body 10 shown in FIG. FIG. 4 is a graph showing the characteristic of the amount of displacement with respect to the applied voltage in the actuator using the electrostrictive ceramic material body of the embodiment of the present invention in comparison with the conventional example. FIG. 5 is a graph showing changes in displacement characteristics of an actuator using the electrostrictive ceramic material body according to the example of the present invention, in comparison with the conventional example. FIG. 6 is a diagram schematically showing an electrostrictive ceramic material body 10 as another embodiment of the present invention. FIG. 7 is a diagram schematically showing an electrostrictive ceramic material body 10 as still another embodiment of the present invention. FIG. 8 is a view for explaining another embodiment of the polarization operating method of the present invention. 9 and 10 are diagrams schematically showing still another embodiment of the present invention. FIG. 11 is a schematic diagram showing the state of spontaneous polarization in the electrostrictive ceramic material after firing on a grain scale. First
FIG. 12 is a schematic view of a state where the electrostrictive ceramic material shown in FIG. 11 is polarized. In the figure, 10 is an electrostrictive ceramic material, 11, 12 are electrodes, 13, 19-23, 26-29 are arrows indicating the degree of polarization orientation and / or the direction of polarization, 14 and 24 are heating heads, 15 Reference numerals 25 and 25 are cooling heads, 16 is a first area, 17 is a second area, and 18 is a power supply for polarization.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Iwatsubo 2-26-10 Tenjin Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd. (72) Inventor Katsuhiro Uemura 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Stock Company Murata Manufacturing Co., Ltd. (56) References Japanese Patent Publication Sho 51-1040 (JP, B1)

Claims (8)

[Claims] 1. An electrostrictive ceramic material body having a dimension in the thickness direction and made of an integrally sintered ceramic material exhibiting an electrostrictive effect, wherein at least a part of the body is viewed in the thickness direction.
At least one of the degree of polarization orientation and the direction of polarization as a whole divides the thickness direction.
And an electrostrictive ceramic material body which is different from each other in the second region. 2. The electrostriction according to claim 1, wherein the polarization directions of the first and second regions as a whole are oriented in the thickness direction but opposite to each other. Ceramic material body. 3. The electrostrictive ceramic material according to claim 1, wherein the first and second regions have different degrees of polarization orientation as a whole. 4. The first region does not exhibit piezoelectricity as a whole, while the second region exhibits piezoelectricity as a whole.
An electrostrictive ceramic material body according to claim 3. 5. An electrostrictive ceramic material body having a dimension in the thickness direction and made of an integrally sintered ceramic material exhibiting an electrostrictive effect by a polarization operation is prepared, and at least a part of the electrostrictive ceramic material body is prepared. ,
A first electric field is applied in the thickness direction while giving a temperature difference in which the former is higher than the latter to the first and second regions dividing the thickness direction, whereby the first region is applied. The method of operating polarization of an electrostrictive ceramic material body, comprising the steps of changing at least one of the degree of polarization orientation as a whole and the direction of polarization as a whole larger than that in the second region. 6. The electrostrictive ceramic material body to which the first electric field is to be applied is previously applied with a second electric field in a direction opposite to the first electric field in at least a part thereof. The polarization of the electrostrictive ceramic material body according to claim 5, wherein the polarization direction of the entire portion to which the second electric field is applied is already oriented in one direction in the thickness direction. Method of operation. 7. The electrostrictive ceramic material body to which the first electric field is applied is not subjected to any polarization treatment after the step of integrally sintering, and the electrostrictive ceramic material body The method for operating polarization of an electrostrictive ceramic material body according to claim 5, wherein the direction of polarization as a whole of the first region is directed to one direction in the thickness direction by application. 8. An electrostrictive ceramic material body having a dimension in the thickness direction and made of an integrally sintered ceramic material exhibiting an electrostrictive effect by a polarization operation is prepared, and at least a part of the electrostrictive ceramic material body is provided. , Applying an electric field directed in the thickness direction, thereby directing the direction of polarization as the entire portion to which the electric field is applied in one direction in the thickness direction, and the direction of polarization as a whole is in the one thickness direction. Of the first and second regions of the electrostrictive ceramic material body having the directed portion, which divide the thickness direction, only the first region is subjected to a high temperature equal to or higher than the Curie point, whereby the first region is provided. 1. A method for manipulating polarization of an electrostrictive ceramic material body, which comprises the steps of changing the degree of polarization orientation as a whole of region 1.