JPH0371681A - Manufacture of composite piezoelectric ceramic element - Google Patents

Abstract

PURPOSE:To simplify the manufacture of even a composite piezoelectric ceramic element where polarization directions intersect each other on the same plane by a method wherein two or more types of piezoelectric materials different in intensity of polarization electric field are burned in one piece and subjected to a polarizing process twice or more times. CONSTITUTION:Two types of ceramic materials 20 and 22 different from each other in polarization electrical field value and Curie temperature are burned in one piece, the burned body 26 is subjected to a polarizing process only twice, whereby two piezoelectric ceramic phases whose polarizing directions intersect each other at a right angle or a composite piezoelectric ceramic element 10 composed of piezoelectric ceramics, 12 and 16, and 14 and 18, is manufactured. Therefore, it is simplified in manufacture, sharply lessened in manufacturing cost, and miniaturized. By this setup, eve if the polarizing directions of two or more piezoelectric ceramic regions intersects each other, a composite piezoelectric ceramic element composed of ceramic regions can be easily formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a composite piezoelectric ceramic element having a plurality of piezoelectric ceramic phases having different polarization directions.

BACKGROUND ART Piezoelectric ceramic elements are often used as various sensors and actuators, and one type of piezoelectric ceramic element that has a plurality of piezoelectric ceramic regions with polarization directions opposite to each other has been proposed in recent years. This involves forming a pair of polarizing electrodes on the side surface of a homogeneous piezoelectric ceramic by dividing them into sections corresponding to the plurality of piezoelectric ceramic regions, and applying an electric field in a predetermined direction between the polarizing electrodes. It is manufactured by applying an electric current, and is used, for example, in various piezoelectric actuators. Further, the polarization direction is not limited to simply the opposite direction, but may be any direction depending on the position where the polarization electrode is formed.

Problems to be Solved by the Invention However, in such a conventional piezoelectric ceramic element, each piezoelectric ceramic region occupies from one end of the element to the other end in its polarization direction, and piezoelectric ceramic regions whose polarization directions are orthogonal to each other could not be established. In other words, although the polarization direction can be set to any direction, this is achieved by the relationship between the twist positions, and it is impossible to form piezoelectric ceramic regions in which the polarization directions intersect within the same plane. It cannot be done. For this reason, when manufacturing such piezoelectric ceramic elements, it is necessary to bond a plurality of piezoelectric ceramics that have been polarized in advance using an adhesive, etc., which increases manufacturing costs and does not provide sufficient bonding strength. There were other problems.

The present invention has been made against the background of the above-mentioned circumstances, and its purpose is to enable easy manufacturing even when the polarization directions of a plurality of piezoelectric ceramic regions cross each other.

Means for Solving the Problems In order to achieve the object, the present invention provides a method for manufacturing a composite piezoelectric ceramic element having a plurality of piezoelectric ceramic phases having different polarization directions, the method comprising: (a) polarization electric field necessary for polarization; (b) integrating and molding the plurality of piezoelectric ceramic materials according to the configuration of the composite piezoelectric ceramic element; (C) The integrally fired fired body is subjected to a predetermined first polarization electric field of 4fi or more, which is the highest among the polarization electric field values of the plurality of types of piezoelectric ceramics constituting the fired body. (d) applying a first polarization treatment to the fired body subjected to the first polarization treatment in a direction in which the polarization electric field value is equal to or higher than the second highest first polarization electric field 4fi; The method is characterized by comprising a step of performing a second polarization process in a predetermined direction with an electric field lower than one polarization electric field 4fi E r.

Here, the reason why the regions with different polarization directions are defined as the piezoelectric ceramic phase is that the ceramic materials of each phase are different from each other, which is essentially different from the piezoelectric ceramic region of a conventional piezoelectric ceramic element, which is made of homogeneous piezoelectric ceramic. For the same reason, such a piezoelectric ceramic element is called a composite piezoelectric ceramic element.

Further, the polarization electric field value is an electric field value that can bring the polarization of the piezoelectric ceramic to a substantially saturated state or change the polarization direction that has been once polarized to a new polarization direction.

Further, as the piezoelectric ceramic material, for example, P
L Z T ((Pb, La) (Zr, Ti)Os)
Ceramic materials having ferroelectric properties such as PZT (Pb(Zr,Ti)Oi) and PZT (Pb(Zr,Ti)Oi) systems are used, and a plurality of types of ceramic materials having different polarization electric field values depending on M are appropriately selected.

In addition, when there are three or more piezoelectric ceramic phases, the n-th (≧3)-th n-th polarization electric field value is Eti + the (n-1)-th (n-1)-th polarization above it. The electric field value is En
If it is set to -1, the third and subsequent polarization treatments will be sequentially performed with an electric field of 87 or more and lower than En-+.

On the other hand, if the Curie temperatures, that is, the temperatures at which ferroelectricity disappears, of the piezoelectric ceramics constituting the fired body are different from each other, and the Curie temperatures decrease in the same order as the polarization electric field values decrease, that is, The Curie temperature of the piezoelectric ceramic having the first polarization electric field 4fi is TI, the Curie temperature of the piezoelectric ceramic having the first polarization electric field 4fi is T2, and if the piezoelectric ceramic contains 3 or more piezoelectric ceramics, the polarization electric field value becomes lower. The Curie temperatures of ceramics are Tff and T.

..., then the Curie temperature is TI > T2 > T
, >..., the first polarization treatment is performed at a temperature between the Curie temperatures T and Tt, and at a temperature between the Curie temperatures Tt and T3 (the piezoelectric ceramic phase is In the case of two cases, a second polarization treatment is performed at a temperature lower than T2), and thereafter, as necessary, T7 and T n *
It is desirable to perform the polarization treatments after 3 in sequence at a temperature between 1 and 2.

Function: In such a manufacturing method, multiple types of piezoelectric ceramic materials having different polarization electric fields are integrally molded according to the configuration of a composite piezoelectric ceramic element, and then integrally fired. By performing the second polarization treatment, two piezoelectric ceramic phases are formed, the polarization directions of which can be set arbitrarily during the polarization treatment. That is, in the first polarization process, the first polarization electric field value E,
Polarization processing is performed with the above electric field, and in the second polarization processing, the first polarization electric field value E2 or more and the first polarization electric field (I!
Since polarization treatment is performed with an electric field lower than El, piezoelectric ceramics having a first polarization electric field value EI (hereinafter referred to as first piezoelectric ceramics) are polarized in the polarization direction during the first polarization treatment, and The piezoelectric ceramic having two polarization electric field values E2 (hereinafter referred to as second piezoelectric ceramics) is polarized in the polarization direction during the second polarization treatment.

Here, the Curie temperature T1 of the first piezoelectric ceramics is
is higher than the Curie temperature Tt of the second piezoelectric ceramics, and performing the first polarization treatment at a temperature between them,
If the second polarization treatment is performed at a temperature lower than the Curie temperature T2, only the first piezoelectric ceramic is polarized during the first polarization treatment, and the second piezoelectric ceramic is polarized only during the second polarization treatment. be done. Note that during the second polarization process, an electric field is also applied to the first piezoelectric ceramics, but since this electric field is lower than the first polarization electric field value E1 that can polarize the first piezoelectric ceramics, The polarization state obtained by the first polarization treatment is maintained well.

In this case, the first polarization electric field value E+, which determines the electric field during the first polarization process, is strictly speaking an electric field value that can bring the polarization of the first piezoelectric ceramic into a substantially saturated state, and the second
The first polarization electric field value E! determines the electric field during the polarization process. teeth,
Strictly speaking, it is an electric field value that can bring the polarization of the second piezoelectric ceramic into a saturated state.

On the other hand, if the first and second polarization treatments are performed independently of the Curie temperature, that is, at a temperature lower than the Curie temperatures of all the piezoelectric ceramics constituting the fired body, the first polarization treatment Not only the first piezoelectric ceramic but also the second piezoelectric ceramic ξ is polarized, but since the second polarization treatment is performed with an electric field higher than the polarization electric field value E2 of the second piezoelectric ceramic ξ, the second piezoelectric ceramic This second
It will be polarized in the polarization direction during the polarization process. As for the first piezoelectric ceramic, as described above, the polarization state obtained by the first polarization treatment is maintained regardless of the second polarization treatment.

In this case, the first polarization electric field value E+, which determines the electric field during the first polarization process, is strictly speaking an electric field value that can bring the polarization of the first piezoelectric ceramic into a substantially saturated state, and the second polarization Strictly speaking, the second polarization electric field value E2 that determines the electric field during the treatment is an electric field value that can change the polarization direction of the second piezoelectric ceramic that has been once polarized.

In addition, when manufacturing a composite piezoelectric ceramic element having three or more piezoelectric ceramic phases, following the second polarization treatment, the n-th polarization electric field value is 87 or more and the (n-1
) Three or more piezoelectric ceramic phases whose polarization directions can be arbitrarily set during each of these polarization treatments are formed by sequentially performing the third and subsequent polarization treatments at an electric field lower than the polarization electric field value Er1-1. Ru.

Effects of the Invention As described above, according to the method of the present invention, the polarization direction can be arbitrarily set by simply performing polarization treatment multiple times on a fired body obtained by integrally firing multiple types of piezoelectric ceramic materials with different polarization electric field values. Since a composite piezoelectric ceramic element having multiple piezoelectric ceramic phases can be obtained, the manufacturing process is simplified and the manufacturing cost is significantly reduced compared to the case where multiple piezoelectric ceramics that have been polarized in advance are fixed together with an adhesive or the like. In addition, it is possible to reduce the size of the composite piezoelectric ceramic element. In addition, since each piezoelectric ceramic phase is integrated by a single firing method, the bonding strength is high and excellent durability can be obtained.

In addition, since the method of the present invention allows the polarization directions of multiple piezoelectric ceramic phases to be set arbitrarily, it is possible to use not only composite piezoelectric ceramic elements whose polarization directions intersect within the same plane, but also cases where the polarization directions are opposite to each other. The present invention can be similarly applied to the production of composite piezoelectric ceramic elements that intersect with each other in a twisted positional relationship.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows an example of a composite piezoelectric ceramic element manufactured according to the method of the present invention. There is. The two piezoelectric ceramics 12 and 16 located diagonally have their polarization directions facing right, as indicated by → in the figure, whereas the other two piezoelectric ceramics 14 and 18 have their polarization directions facing right. In the figure, it is directed upward as indicated by ↑. That is, in this example, the piezoelectric ceramics 12 and 16 constitute one piezoelectric ceramic phase whose polarization direction is to the right, while the piezoelectric ceramics 14 and 18 constitute another piezoelectric ceramic phase whose polarization direction is upward. It is integrally equipped with two piezoelectric ceramic phases. Such a composite piezoelectric ceramic element 10 can be used, for example, in various piezoelectric actuators.

Next, an example of a method for manufacturing such a composite piezoelectric ceramic element IO will be described.

First, the ceramic material 20 of piezoelectric ceramic 12.16 constitutes one piezoelectric ceramic phase, and the piezoelectric ceramic 14.16 constitutes another piezoelectric ceramic phase.
Eighteen ceramic materials 22 are prepared, and as shown in FIG. 2, they are integrally molded by heat-pressing into the same cross-section shape as the composite piezoelectric ceramic element 10. The ceramic materials 20 and 22 are both piezoelectric ceramic materials having ferroelectricity such as PZT type, but
Those having different polarization characteristics and Curie temperatures are selected depending on their M values. Ceramic materials 20
The polarization characteristics of ceramic material 20 and 22 are shown by solid lines and dashed-dot lines in FIG. 6, respectively.
A polarization electric field value E that can bring the polarization of
is sufficiently higher than the polarization electric field value E2 that can bring the polarization of the ceramic material 22 into a substantially saturated state. Moreover, the Curie temperature T of the ceramic material 20 is the Curie temperature T of the ceramic material 22! higher than

The polarization electric field values El and EZ correspond to a first polarization electric field value and a second polarization electric field value, respectively.

Then, by integrally firing the molded rod 24 in which the ceramic materials 20 and 22 are integrally molded, a fired body having the same structure as the composite piezoelectric ceramic element 10 is obtained, as shown in FIG. 26 is obtained, but
At this stage, each piezoelectric ceramic 12, 14, 16 .
The direction of spontaneous polarization of 18 is random. Since the fired body 26 is integrated by a diffusion reaction occurring at the boundary between the ceramic materials 20 and 22 during firing, it has strength comparable to single-phase piezoelectric ceramics, and each piezoelectric ceramic material 12, 14°16.18 are bonded with extremely high bonding strength.

Next, as shown in FIG. 4, a pair of polarization electrodes 28 are formed on both left and right sides of the fired body 26, and polarization is performed in an oil bath (not shown) filled with silicone oil or the like. An electric field is applied between the pair of polarization electrodes 28 by a power source 30. The temperature of the oil bath at this time is between the Curie temperature T and T2, and the piezoelectric ceramics 12 and 16 made of the ceramic material 20 are
still has ferroelectricity, but piezoelectric ceramics 14 and 18 made of ceramic material 22 have lost their ferroelectricity. In addition, the applied electric field is the polarization electric field value of 85
That's all. Therefore, in such polarization treatment,
Only the piezoelectric ceramic 12 and the ceramic 6 having ferroelectricity are polarized to the right. This step is the step of performing the first polarization treatment.

Subsequently, after removing the polarization electrodes 2, as shown in FIG. 5, a pair of polarization electrodes 32 are formed on both upper and lower sides of the fired body 26, and the first polarization treatment is performed. Similarly, an electric field is applied between a pair of polarization electrodes 32 by a polarization power source 30 in an oil bath. The temperature of the oil bath at this time is lower than the Curie temperature T2,
The piezoelectric ceramics 12, 14, 16.18 are all maintained in a ferroelectric state. Further, the applied electric field is greater than or equal to the polarization electric field value 82 and lower than the polarization electric field value EI. Therefore, in this polarization treatment, only the piezoelectric ceramics 14 and 18 whose polarization electric field value is E2 are polarized upward, and the piezoelectric ceramics 12 and 16 whose polarization electric field value is E are polarized in the polarization state due to the first polarization treatment. maintained. Incidentally, the polarization electric field value EI that determines the applied electric field in this case is, strictly speaking, an electric field value that can change the polarization direction of the piezoelectric ceramic soft 12, 16 once polarized. This step is the step of performing the second polarization treatment.

Thereafter, by removing the polarization electrode 32, the composite piezoelectric ceramic element 10 is obtained.

In this way, in this example, after the two types of ceramic materials 20 and 22 having different polarization electric field values and Curie temperatures are fired together, the polarization direction can be changed by simply subjecting the fired body 26 to two polarization treatments. Two orthogonal piezoceramic phases, namely piezoceramics 12 and 16
．． Composite piezoelectric ceramic element 1 having 14 and 18
0 is produced. Therefore, compared to the case where a plurality of piezoelectric ceramics that have been polarized in advance are fixed together using an adhesive or the like, the manufacturing process is simplified, the manufacturing cost is significantly reduced, and the composite piezoelectric ceramic element 10 is made smaller. It is possible to achieve this. Furthermore, since the piezoelectric ceramics 12, 14, 16, and 18 are integrated by integral firing, their bonding strength is high and excellent durability can be obtained.

Note that the above is just one specific example of the present invention, and for example, the first polarization treatment may be performed at a temperature lower than the Curie temperature T2. The present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art, such as that the present invention can be applied to the manufacture of piezoelectric ceramic elements.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a composite piezoelectric ceramic element manufactured according to the method of the present invention. 2 to 5 are diagrams explaining the manufacturing process of the composite piezoelectric ceramic element shown in FIG. is a fired body obtained by integrally firing the formed rod, FIG. 4 shows the step of subjecting the fired body to the first polarization treatment, and FIG. 5 shows the step of subjecting the fired body to the second polarization treatment. . FIG. 6 is a diagram showing the polarization characteristics of two types of piezoelectric ceramic materials. 10: Composite piezoelectric ceramic element 12.16: Piezoelectric ceramic (one piezoelectric ceramic phase) 14.18: Piezoelectric ceramic (another piezoelectric ceramic phase) 20.22: Piezoelectric ceramic material 26: Sintered body

Claims (1)

[Scope of Claims] A method for manufacturing a composite piezoelectric ceramic element having a plurality of piezoelectric ceramic phases having different polarization directions, wherein a plurality of types of piezoelectric ceramic materials having different polarization electric field values necessary for polarization are used to form a plurality of piezoelectric ceramics. a step of preparing the plurality of types of piezoelectric ceramic materials as a constituent material of the phase; a step of integrally molding the plurality of types of piezoelectric ceramic materials according to the configuration of the composite piezoelectric ceramic element and then firing them together; performing a first polarization treatment in a predetermined direction with an electric field equal to or higher than the highest first polarization electric field value among the polarization electric field values of the plurality of types of piezoelectric ceramics constituting the body; and the first polarization treatment is performed. In the fired body, the polarization electric field value is equal to or higher than the second highest polarization electric field value and the first
A method for manufacturing a composite piezoelectric ceramic element, comprising the step of performing a second polarization treatment in a predetermined direction with an electric field lower than a polarization electric field value.