JPH101367A - Manufacturing method of crystal oriented ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a crystallographically oriented ceramic which is excellent in various characteristics depending on a specific crystal orientation and can easily and inexpensively produce a ceramic in a thick film state. thing. SOLUTION: Using a solution containing a metal element constituting oxide polycrystalline ceramics or a viscous sol formed from the solution, a film-shaped molded body having a width of 2 mm or more and a thickness of 500 μm or less is formed. And a second step of heat-treating the film-shaped body. According to this method, it is a crystallographically-oriented ceramic having a specific crystal plane composed of oxide polycrystalline ceramics, and the degree of orientation of the crystallographically-oriented ceramic is 10% or more as calculated by Lotgering method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing crystal oriented ceramics composed of oxide ceramics, which can be used for acceleration sensors, ultrasonic sensors, infrared sensors utilizing a pyroelectric effect, etc. utilizing a piezoelectric effect.

[0002]

2. Description of the Related Art Several techniques for orienting the crystal plane or crystal axis of polycrystalline ceramics have been proposed. By orienting a specific crystal plane or crystal axis of the polycrystalline ceramic, a polycrystalline ceramic having a composition close to a single crystal can be produced. Thereby, characteristics dependent on a specific crystal plane or crystal axis can be greatly improved.

[0003] In particular, ferroelectric polycrystalline ceramics whose properties largely depend on a crystal axis having polarity have a higher electric property than non-oriented polycrystalline ceramics in which crystals are not oriented by orienting the crystals. Patent applications and technical reports have been filed for improving characteristics derived from polarity such as the mechanical coupling coefficient and the amount of remanent polarization. Also, it has been reported that the use of ferrite ceramics in which crystals are oriented improves the abrasion resistance of magnetic materials and extends the life of magnetic heads (powder and powder metallurgy, Vol. 26, No. 4, No. 4). Pp. 123-130, 1979).

Conventionally, various methods have been disclosed as means and methods for orienting the crystals of polycrystalline ceramics. Some of them are exemplified below. For example, a polycrystalline ceramic having a specific crystal plane whose surface energy is significantly smaller than that of other crystal planes, such as a layered perovskite structure represented by bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ), is heated. A dense crystal-oriented ceramic in which crystals are uniaxially oriented can be obtained by a hot forging method in which a uniaxial pressure is applied (Jpn. J. Appl. P.
hys. , Vol. 19, no. 1, pp31-39,
1980).

A substance having a strong crystal anisotropy, such as the above-mentioned bismuth titanate, is capable of synthesizing a plate-like or needle-like powder. There is also known a method in which these anisotropically shaped powders are oriented by molding or extrusion, and then sintered by heat treatment to prepare crystallographically oriented ceramics (J. Am. Ceram. Soc., Vol. 7
2, No. 2, pp 289-93, 1989).

[0006] Further, a molding method for increasing the degree of orientation (the degree of crystal orientation) using plate-like powder (typically α-type iron oxide) as a raw material for forming a skeleton, such as ferrite having a spinel structure, has also been proposed. It was possible to produce crystallographically oriented ceramics by a so-called topokitacy method, in which the product takes over the orientation axis of the raw material during synthesis (Electronic Ceramics, July 1991, pp. 56-
63, 1991). However, this method is effective only when there is a combination of a raw material and a product having a steric lattice matching property such as iron oxide as a raw material and ferrite as a ceramic capable of performing a topotaxic reaction.

[0007]

[Problems to be Solved] However, a material whose crystal type is isotropic (cubic system) or quasi-isotropic (slightly distorted cubic system), and which has a three-dimensional lattice matching capable of a topotaxy reaction. Crystal-oriented ceramics made of a material that does not have anisotropic raw materials have been difficult to fabricate unless relying on single crystal growth that is expensive and inferior in productivity.

For example, a perovskite-type structure, which is a crystal type taken by many engineeringly important ferroelectrics such as PZT (compound name: lead zircon / titanate) and barium titanate, has a cubic structure or a cubic structure. It has a slightly distorted cubic structure, and exhibits large anisotropy of characteristics depending on the direction of the distortion. However, the crystal anisotropy of these materials is extremely small, and it is therefore extremely difficult to synthesize a single crystal powder having an anisotropic shape. In addition, since the oxides such as Ti, Zr, and Nb constituting the skeleton have a similar long-period structure to the skeleton structure of the perovskite type, a powder having an anisotropic shape cannot be synthesized. Did not.

Hitherto, a patent has been published for a technique for producing oriented ceramics such as lead titanate and barium titanate using potassium titanate fiber or its derivative, fibrous titanium oxide or fibrous hydrated titanium oxide, as a raw material. (Japanese Patent Publication No. 63-24949, Japanese Patent Publication No. 63-2
4950, JP-B-63-43339, JP-B-63-
No. 43340, JP-B-63-43341), and it is extremely difficult in principle to produce crystallographically-oriented ceramics using potassium titanate fibers having a Ti—O bond skeleton different from the perovskite structure and derivatives thereof. This difficulty in principle means that if the Ti—O bond skeleton in the potassium titanate fiber or its derivative is not rearranged, it will not become the Ti—O bond skeleton in the perovskite-type structure. Is difficult to hold.

Another method for obtaining a crystallographically oriented ceramic having a perovskite type structure in which crystals are oriented is to form a thin film on a substrate by a method such as sputtering, chemical vapor deposition (CVD), or sol-gel. Epitaxy, which uses a substrate surface with good lattice matching with a specific crystal plane of the structure, and self-texture, in which a specific crystal plane is oriented due to a difference in surface energy or a difference in the supply of atoms, regardless of the crystal orientation of the substrate It has been known.

However, such a method requires a long film forming time and a high manufacturing cost in order to form a thick film, and furthermore, the film is restrained by the substrate.
If the film thickness is to be increased, cracks occur in the film due to the stress caused by crystallization and densification during heat treatment and the difference in the coefficient of thermal expansion with the substrate, and the film peels off from the substrate. Occurs and the film is likely to be destroyed. Therefore, it is extremely difficult to obtain a crystallographically-oriented ceramic having a thickness exceeding 5 μm by such a method. Therefore, the above method is not suitable as a method for obtaining a bulk material.

Further, as another technique, there is a technique of spinning a viscous solution containing a metal element, for example, Pb, Ti, Zn, and applying a heat treatment to produce a polycrystalline PZT fiber (Yoshikawa, et al.). ., Proce
edings of theEightth IEEE
International Symposium
Applications of Ferroele
ctrics, pp. 269-272, 1992).

However, since the polycrystalline PZT fiber is formed by being extruded from a circular hole, the shape of the polycrystalline PZT fiber is a circular cross-sectional fiber shape having no large flat surface. Therefore, even if nucleation and growth occur on the surface of the fiber and there are grains having a self-texture, their crystal axes are not commonly oriented, and the polycrystalline PZT fiber is a special type. No orientation is shown.

Japanese Patent Publication No. Hei 7-115935 discloses a method for producing a ceramic precursor thin film in which a viscous liquid prepared by uniformly mixing a sol formed from a metal compound with an organic polymer is discharged from a slit. A method for producing a ceramic precursor thin film characterized by forming a continuous thin film is described. Although this published patent also includes a fabricated example, it does not disclose the crystal orientation, and it is unknown whether the crystal of the ceramic precursor thin film obtained by this is oriented.

In addition, a patent application has been filed for a method of producing a piezoelectric ceramic in which crystals are oriented by attaching crystal seeds to the surface when crystallizing an amorphous piezoelectric ceramic powder compact by heat treatment. Japanese Patent Publication No. 62-72560). However, in this method, the crystal nucleus itself growing from the place where the seed crystal is attached is not crystal-oriented. Thus, even if these crystal nuclei collide laterally (as described in the above specification) and crystal growth occurs only in the vertical direction, the grown crystal is still not crystallographically oriented.

In view of the above problems, the present invention provides a method for producing a crystallographically oriented ceramic, which is excellent in various characteristics depending on a specific crystal orientation and can easily and inexpensively produce a ceramic in a thick film state. It seeks to provide a way.

[0017]

A first aspect of the present invention is to use a solution containing a metal element constituting oxide polycrystalline ceramics, or a viscous sol-like material prepared from the solution, to form a polycrystalline ceramic having a width of 2 mm.
A method for producing a crystallographically-oriented ceramic, comprising: a first step of forming a film-shaped molded body having a thickness of not less than mm and a thickness of not more than 500 μm; and a second step of heat-treating the film-shaped molded body.

In the above manufacturing method, a solution containing a metal element constituting the oxide polycrystalline ceramics, or a sol formed from the solution is formed into a film-shaped molded body. By subjecting this to a heat treatment, the film-shaped molded body is thermally decomposed and oxidized, and the contained organic components and the like are removed and crystallized. As described above, the film-shaped molded body can be formed into a tape-like or flaky sintered body, and this sintered body becomes a crystal-oriented ceramic.

In the above crystallographically-oriented ceramics, the crystal plane having the smallest surface energy is oriented in parallel on the flat surface in the width direction of the tape-shaped or flake-shaped sintered body, and the orientation state is tape-shaped or flake-shaped sintered body. It has been taken over by the union. Note that the crystal plane having the smallest surface energy generally means a continuous strongest binding chain as 2
This is a pseudo-cubic {100} plane in a crystallographically oriented ceramic which is a compound having a perovskite structure. The strongest binding chain (Pe
“Riodic Bond Chain” refers to a continuous row of atoms or ions having the strongest binding energy in the crystal structure.

In the above-mentioned manufacturing method, the process of turning the film-shaped molded body into a crystallographically-oriented ceramic will be described. First, the film-like molded product obtained in the first step is crystallized in the second step to form a sintered body. The heat treatment in the second step mainly consists of two processes, the first step and the second step. Consisting of In the first step, a solvent or the like is removed from the film-shaped molded body, and in addition to the progress of thermal decomposition, oxidation, and polymerization, a crystal is formed on at least a flat surface that is a surface in the width direction of the film-shaped molded body. Nuclei form.

When the crystal nuclei grow into crystal grains, a crosslinked network develops preferentially with other crystal nuclei on a flat surface as compared with other portions of the film-shaped molded body. . At this time, the densification of the film-shaped molded body is partially started. As described above, the adjacent crystal nuclei on the flat surface are formed while the crystal planes are oriented in substantially the same direction.

Next, in the second stage, the above-mentioned crystal grains grow toward the inside of the film-shaped formed body and become crystal grains. Then, the densification of the film-shaped molded body proceeds. In the above-mentioned grain growth, relatively large crystal grains on the flat surface are
This is based on so-called Ostwald growth, in which amorphous or fine crystal grains existing inside the film-like molded body are taken in. At this time, fine crystal grains and the like inside the film-shaped molded body are taken in so as to have the same orientation as the crystal nuclei on the flat surface. As described above, the crystallization of the film-shaped molded body proceeds while inheriting the orientation of the crystal plane on the flat surface, and thus the obtained sintered body is a crystal-oriented ceramic.

The above-mentioned production method described above comprises very simple operations such as liquefaction or solification of raw materials, molding of a film-like molded product, and heat treatment of the film-like molded product. Crystal oriented ceramics can be manufactured without using equipment, equipment, technology, and the like. Further, in the conventional method, it was difficult to obtain a crystallographically-oriented ceramic having a thickness of 5 μm or more. However, according to the above-described manufacturing method, a thick-film crystallographically-oriented ceramic can be easily and inexpensively obtained as described above. Therefore, according to the above manufacturing method, it is possible to provide a method for manufacturing a crystallographically-oriented ceramic which can be easily and inexpensively manufactured.

According to the production method of the present invention, the following crystallographically-oriented ceramics can be obtained. It is a crystallographically-oriented ceramic composed of oxide polycrystalline ceramics whose crystal faces are oriented, and the degree of orientation of the crystallographically-oriented ceramic is Lotgeri.
It is a crystallographically-oriented ceramic that is 10% or more as calculated by the ng method. Further, in the present invention, it is possible to produce a crystallographically-oriented ceramic having the above-described degree of orientation even if the oxide polycrystalline ceramic is other than ferrite or ferrite.

The function of the crystallographically-oriented ceramic will be described below. This crystallographically oriented ceramic
This is a so-called oriented oxide polycrystalline ceramic having a microstructure in which single crystal grains constituting the crystal are arranged on a specific single crystal plane. For this reason, the characteristics of the above crystallographically oriented ceramics greatly depend on a specific crystal orientation, as compared with non-oriented oxide polycrystalline ceramics. Specific examples of the above characteristics include, for example, magnetic susceptibility, dielectric constant, electromechanical coupling constant,
Examples include a residual polarization amount, a pyroelectric coefficient, a piezoelectric g constant, and the like (Tables 2, 4, and 5 described later).

Further, for example, the following can be cited as characteristics to be improved by orientation and its applied technology. Pyroelectric-pyroelectric sensor, piezoelectric-acceleration sensor, piezoelectric transformer or substrate for surface acoustic wave, thermoelectric-electronic refrigeration or thermoelectric power generation, ionic conductivity-gas sensor or solid electrolyte, electricity storage-capacitor, electron conductivity- Superconducting device, electrical insulating-insulating substrate, thermal conductive-substrate or heat sink.

Therefore, various sensors and devices made by utilizing the above-described characteristics of the oxide polycrystalline ceramics use the non-oriented oxide polycrystalline ceramics by using the crystal oriented ceramics. The performance is greatly improved as compared with the case. The various sensors include a high-sensitivity pyroelectric sensor and a high-sensitivity acceleration sensor, and the various devices include a high-efficiency resonator, a high-efficiency piezoelectric transformer, and the like.

As described above, according to the present invention, it is possible to provide a crystallographically-oriented ceramic excellent in various characteristics depending on a specific crystal orientation.

When the degree of orientation is less than 10%, there is a possibility that no remarkable improvement in characteristics is not recognized (Tables 2, 4 and 5 described later). Further, when the degree of orientation is 20
% Is preferable. If the degree of orientation is in this range, further improvement in characteristics can be recognized. Examples of the polycrystalline oxide ceramics include those having a perovskite structure, such as lead zirconate titanate shown below.

In addition, regarding the Lotgering method,
This will be described below. That is, the degree of orientation Q (HKL) of the crystallographically-oriented ceramic obtained by the Lotgering method is:
It is defined by the following Equation 1.

[0031]

(Equation 1)

Here, I (HKL) is the X-ray diffraction intensity from the crystal plane (HKL) in the crystallographically-oriented ceramic. On the other hand, I ₀ (HKL) is the X-ray diffraction intensity from the crystal plane (HKL) of the non-oriented oxide polycrystalline ceramic having the same composition as the above-mentioned crystal-oriented ceramic. Σ′I (HKL) is I (100), I (2
00), I (300), etc. are the sum of the X-ray diffraction intensities from each crystallographic plane of the crystallographically-oriented ceramic. On the other hand, ΔI ₀ (hkl) is the sum of the X-ray diffraction intensities from all crystal planes (hkl) in the non-oriented oxide polycrystalline ceramic. The value of Q (HKL) is standardized to be 0% in the case of no orientation and 100% in the case where all the crystal grains are oriented.

In order to measure the X-ray diffraction intensity for obtaining the degree of orientation, the measurement sample is rotated eccentrically from the center of rotation to irradiate a large area, and as many crystal grains as possible are captured. Is preferably improved. This is particularly effective when the crystal grains are large.

Preferably, the oxide polycrystalline ceramic has a perovskite structure as a main phase, and the oriented crystal plane is a {100} plane when the perovskite is regarded as a pseudo-cubic crystal. In the perovskite-type structure, the crystal structures are usually cubic, tetragonal, hexagonal, and orthorhombic. These structures are regarded as pseudo-cubic crystals slightly distorted from cubic crystals. Advance. For example, in the case of a tetragonal perovskite structure, the {100} plane and the {001} plane in the tetragon become the pseudo-cubic {100} plane.

By orienting using this surface having a low surface energy, the direction of polarity is more uniform than that of non-oriented ceramics. Can be obtained. Examples of the oxide polycrystalline ceramics having a perovskite structure include ceramics such as lead zirconate titanate, lead titanate, and barium titanate.

Next, the first step will be described in detail. The solution or sol can be prepared by a so-called sol-gel method or complex polymerization method using an organic metal compound such as an alkoxide of a metal element or a metal salt of a metal element as a raw material. In particular, when preparing a solution or sol using the sol-gel method, it is preferable to perform hydrolysis in the preparation process to prepare a solution or sol having at least partially crosslinked in its molecular structure. . Thereby, the effect that the network of the strongest binding chain easily develops on the surface can be obtained.

It is preferable to adjust the viscosity and the degree of cross-linking to the solution or sol by adding an organic solvent, water, a thickener, and the like, if necessary. Thereby, the effect of keeping the surface of the film-shaped molded body smooth can be obtained.

The above-mentioned organometallic compounds and metal salts include Ti, Nb, Zr, Fe, Ba, Pb, Bi, S
alkoxides such as ethoxide, methoxide, propoxide, butoxide, carboxylate, etc. of a wide range of elements including r, La, Ge, Si, Al, Zn, and Mg.
Nitrate, chloride and the like can be used, but are not limited to the above ranges.

Next, the film-shaped molded body has a width of 2 mm or more and a thickness of 500 μm or less. If the width is less than 2 mm, a flat surface having a sufficient area may not be obtained, and the degree of orientation may be reduced. The width is preferably 1 m or less. If the width is larger than 1 m, it may be costly to form the film-shaped molded body.

Further, when the thickness is greater than 500 μm, it may be difficult for crystal nuclei generated on the flat surface to grow inside the film-shaped molded body. Note that the thickness is preferably 1 μm or more. 1μ thick
When it is less than m, there is a possibility that cost is required for molding the film-shaped molded body.

Next, the first step will be described in detail. The formation of the film-shaped molded body may be performed in any atmosphere such as the air, or may be performed in a liquid. In the case of a solution or sol in which the cross-linking network of crystal nuclei is incompletely developed on the flat surface of the film-like molded product, a method of forming the molded product in an atmosphere containing water vapor or in water or an organic solvent in order to promote the development. It is preferable to form the above-mentioned film-shaped molded body by using the above method. When the solution or sol contains an alkaline earth, alkali, or rare earth element, the film-like molded body is placed in an atmosphere containing no carbon dioxide, or in water or an organic solvent liquid containing no carbon dioxide. It is preferred to mold. As a result, Ba and L
An element in which a stable carbonate exists, such as a, can be prevented from forming a carbonate.

Although the dimensions of the film-like molded body are almost equal to the dimensions of the slit immediately after molding, the dimensions shrink due to evaporation of water and an organic solvent. Therefore, the dimensions of the film-shaped molded article in the present invention are those of the film-shaped molded article immediately after molding.

Further, in order to increase the flatness of the flat surface of the obtained film-shaped molded product, the flat surface may be subjected to a rolling treatment. Thereby, the degree of orientation can be further increased.

Next, the details of the second step will be described. The heat treatment in the second step can be mainly divided into two processes, a first stage and a second stage. One of the first stages will be described below. The temperature of the heat treatment in the first stage is preferably 500 ° C. or less. When the crystallographically-oriented ceramic to be obtained has a perovskite-type structure, such as barium titanate, which has a hardly crystallizable perovskite-type structure as a main phase, the temperature is preferably 700 ° C. or lower.

As a result, crystal nuclei can be preferentially generated on the flat surface of the film-shaped molded body together with the thermal decomposition of the organic component. Since a rapid thermal decomposition reaction easily occurs and the film-like molded body is easily broken, it is preferable to perform a gradual temperature increase. Further, in order to reduce the density of generated crystal nuclei, it is preferable that the rate of temperature rise of the film-shaped molded body in the first stage is 10 ° C. or less per minute. Further, as the heating means in the first stage, an electric furnace, an infrared heating furnace, or the like can be used. However, in order to preferentially generate crystal nuclei on the flat surface of the film-shaped molded body, a means capable of applying heat from the outside of the film-shaped molded body by radiation and heat transfer is preferable.

The temperature of the first heat treatment is 30.
The temperature is preferably set to 0 ° C. or higher. If the temperature is lower than this temperature, crystallization may not proceed. Further, the progress of crystallization may be slowed down.

When the crystallographically-oriented ceramic to be obtained contains a volatile substance such as lead (including lead oxide), heat treatment is performed in an atmosphere containing the volatile substance. It is necessary to take measures to prevent volatile substances from being lost from the film-shaped molded body. In addition, in the second step of the above-mentioned film-like molded article containing a volatile substance, in order to prevent the volatile substance from being volatilized, a precursor solution containing this volatile substance is applied to the surface of the above-mentioned film-shaped molded article by flattening. It is preferable to apply it to the surface in advance.

Next, the second stage will be described. The temperature of the heat treatment according to the second step is 600 ° C to 1500 ° C.
It is preferable that As a result, diffusion of atoms necessary for grain growth and densification of the film-shaped molded body is likely to occur. If the temperature of the heat treatment is lower than 600 ° C., improvement in the degree of orientation due to grain growth may be hindered. On the other hand, 150
If the temperature exceeds 0 ° C., the irregularity of the surface becomes severe due to abnormal growth of the particles, and the degree of orientation may decrease again. Note that the temperature of the heat treatment in the second stage slightly varies depending on the type of the metal element and the thickness of the film-shaped molded body. The thicker the film-shaped molded body, the higher the heat treatment required.

For example, when the crystallographically-oriented ceramic to be obtained contains a volatile substance (lead in this case) such as zircon / lead titanate, heat treatment is performed in an atmosphere containing this volatile substance. It is preferred to do so. Further, in order to make it difficult for volatile substances to be lost from the film-shaped molded body, it is preferable to perform the heat treatment at a temperature in the range of 600 ° C to 1350 ° C. Also, as in the first step, it is necessary to devise a means such that the volatile substance is not lost from the film-shaped molded body by means such as heat treatment in an atmosphere containing the volatile substance. If the crystallographically-oriented ceramic to be obtained is difficult to crystallize, especially barium titanate, the heat treatment is performed at a temperature of 700 ° C.
It is preferable to carry out in the range of 1500 ° C.

By adding an external field to the crystallographically-oriented ceramic obtained by the above manufacturing method,
Various characteristics related to the external field can be enhanced. For example, for a crystallographically-oriented ceramic having a performance as a ferroelectric substance, the polarization amount can be increased by performing a polarization process to make the direction of the polarity uniform by applying an electric field.

For example, in a crystal oriented ceramic having a tetragonal perovskite structure such as lead titanate or barium titanate, the {001} crystal plane is oriented parallel to the flat surface by such a treatment. Not only the degree of orientation as a pseudo-cubic crystal but also the degree of orientation as a tetragonal crystal is increased. Also, when the flat surface is polished in parallel and an electrode is provided on this surface, the characteristics derived from polarization are increased on this surface, and the electromechanical coupling coefficient and the pyroelectric coefficient are further increased. preferable. Further, the piezoelectric g constant is also preferable because it greatly increases.

By the manufacturing method according to the present invention, it is also possible to produce a crystal-oriented ceramic composed of a polycrystalline oriented ceramic other than a ferrite-based oxide or a ferrite-based crystal-oriented ceramic.

Next, a plurality of crystallographically-oriented ceramics obtained by heat-treating the film-shaped molded body are laminated to form a laminate, and the laminate is subjected to uniaxial pressing. It is preferable to perform heat treatment in the added state.

In the present invention, a film-shaped or tape-shaped crystallographically-oriented ceramic obtained by heat-treating a film-shaped molded body is uniaxially applied to a laminate obtained by laminating a plurality of such ceramics with their flat surfaces facing each other. The heat treatment is performed while applying pressure. Thereby, bulk-shaped or pellet-shaped crystallographically-oriented ceramics can be easily produced.

In the biaxial pressing and heat treatment, the uniaxial pressing and heat treatment are carried out at a temperature similar to or higher than that of the first step in the above-mentioned second step using a usual hot press furnace. It is preferable to apply. That is, the temperature of the heat treatment is preferably in the range of 600 to 1500 ° C. Further, when the crystallographically-oriented ceramic to be obtained has a perovskite-type structure which is difficult to crystallize, such as barium titanate, as a main phase, 700 to 1500
C. is preferred.

As a result, excellent adhesion can be obtained between the stacked crystal oriented ceramics. In addition, it is preferable that the uniaxial pressing is performed gradually from a direction perpendicular to the plane on which the crystallographically-oriented ceramics are laminated. As a result, a crystallographically oriented ceramic having a large thickness can be obtained without significantly lowering the degree of orientation or causing cracks.

The pressure in the uniaxial pressing is 5 k
It is preferably from g / cm ^{2 to} 500 kg / cm ² . When the pressure is lower than 5 kg / cm ² , the layers are hardly adhered to each other. On the other hand, when the pressure is higher than 500 kg / cm ² , the laminate may be thinned again.

In order to obtain bulk or pellet-shaped crystallographically-oriented ceramics with built-in electrodes, they can be prepared by the following procedure. First,
An electrode paste is applied to one or both flat surfaces of one or more crystal-oriented ceramics.

Thereafter, the crystal oriented ceramics coated with the electrode paste and the normal crystal oriented ceramics are appropriately laminated to form a laminate, and as described above, heat treatment is performed while uniaxial pressure is applied. According to this procedure, various sensor elements and various devices made of crystallographically-oriented ceramics can be easily produced.

Further, an arbitrary powder or an arbitrary sintered body, a green sheet, or the like may be inserted between the crystallographically oriented ceramics to be laminated to form a laminated body, and as described above, heat treatment may be performed in a state where uniaxial pressure is applied. it can. Thus, various sensor elements, various devices, and the like made of crystallographically-oriented ceramics can be easily produced.

Next, as in the third aspect of the present invention, a plurality of the film-like molded bodies are laminated and uniaxially pressed to form a laminated body.
It is preferable to perform heat treatment after heating and pressing the laminate as needed. According to the present invention, the laminated body obtained by laminating a plurality of film-shaped molded bodies with their flat surfaces facing each other is heated and crimped, if necessary, in a state where uniaxial pressure is applied, followed by heat treatment. Is what you do.
Thereby, bulk-shaped or pellet-shaped crystallographically-oriented ceramics can be easily produced.

The heating performed in the state where the uniaxial pressure is applied is preferably performed in a temperature range of 300 ° C. or less.
This makes it easy for the film-shaped molded articles to adhere to each other, and also prevents full-scale thermal decomposition of the organic components contained in the film-shaped molded articles. In addition, a more preferable temperature range has a lower limit of 50 ° C. and an upper limit of 150 ° C.

The pressure in the uniaxial pressurization is 10
It is preferably from g / cm ^{2 to 1} kg / cm ² . When the above pressure is less than 10 g / cm ² , the film-like molded product is not pressed, while when it is more than 1 kg / cm ² , the thickness of the laminate decreases and the shape of the laminate becomes bulky or pellet-like. May not be able to be obtained. The lower limit of the above pressure is more preferably 20 g / cm ² , and the upper limit is 100 g / cm ² .

The heat treatment in a state where uniaxial pressure is applied to the laminate is performed with the laminate inserted between metal plates or the like via a polymer film such as tetrafluoroethylene. Is preferred. Thereby, adhesion with a metal plate can be prevented. The surface of the metal plate facing the laminate is preferably smooth. Thereby, it is possible to obtain a uniaxially crystallographically-oriented ceramic having a high degree of orientation while maintaining a smooth surface of the molded body. The heat treatment for this laminate is the same as the heat treatment conditions in the first and second stages in the above-described second step.

Next, as in the fourth aspect of the present invention, the film-shaped molded product is formed by extruding a solution or sol having a viscosity adjusted to 100 poise or more through a slit of an extrusion die. Is preferred. Thereby, the film-shaped molded body can be easily formed.

The slit preferably has an average roughness in the width direction of 50 μm or less. When the average roughness is 50 μm or less, the obtained crystallographically-oriented ceramic can have an orientation degree of 20% or more as calculated by the Lotgering method described above. Note that a more preferable upper limit of the average roughness is 10 μm or less.

When the solution or sol is extruded, the solution or sol is passed through the slit by mechanical means such as a piston or by air pressure. The viscosity of the solution or sol must be high enough to allow passage through the slit, in which case the viscosity is 100 poise or more. If the above viscosity is less than 100 poise, the film-like molded product cannot maintain its shape,
There is a risk of deformation due to flow. In addition, there is a possibility that unevenness may occur on the flat surface of the surface of the film-shaped molded body. In addition, more preferable viscosity is 500 poise or more.

When a solution or a sol made of a material containing a volatile substance such as lead is formed,
It is preferable to extrude the film-shaped molded body into a solution containing the above-mentioned volatile substance. Thus, the volatile substance can be present in excess on the surface of the film-shaped molded body, and the volatile substance can be prevented from being lost from the film-shaped molded body during the heat treatment. Note that water and an organic solvent can be used as the solvent of the above solution.

[0069]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A method for producing a crystallographically-oriented ceramic according to an embodiment of the present invention and its performance evaluation will be described. The crystallographically-oriented ceramic of this example is a crystallographically-oriented ceramic made of La, Mn-added lead titanate and having a specific crystal plane oriented. The degree of orientation is 10% or more as calculated by the Lotgering method described above.

The method for producing a crystallographically-oriented ceramic according to the present embodiment comprises forming a film-shaped molded product having a width of 2 mm or more and a thickness of 500 μm or less using a viscous sol containing Pb, Ti, La and Mn. And a second step of heat-treating the film-shaped body. The film-shaped molded body is formed by extruding a sol having a viscosity adjusted to 100 poise or more through a slit of an extrusion mold.

Next, the production method will be described in detail, and the relationship between the viscosity of the sol-like material and the degree of orientation of the crystallographically-oriented ceramic obtained thereby will be shown in Table 1 below.
This will be described using 1 to A5.

First, the first step in the above manufacturing method will be described. Raw materials of lead acetate, titanium isopropoxide, lanthanum isopropoxide and manganese acetate were prepared. These raw materials were dissolved in 2-methoxyethanol such that the atomic molar ratio of Pb, Ti, La, and Mn was 98: 99: 2: 1. Thereafter, a half equivalent of water was added to this solution and heated at 120 ° C. to form a sol while measuring the viscosity.
The sol was sampled at 0, 1000, and 1500 poise.

The above sol-like material is 5 mm × 200 μm in size.
Extrusion molding was carried out through the slits to obtain a tape-like film-shaped molded product. However, it is difficult to extrude a sol having a viscosity of 1500 poise through a slit having the above-mentioned size.
Extrusion was performed using a 1 mm slit. The average roughness in the width direction of these slits was 5 μm. Next, the film-shaped molded body was dried at a temperature of 100 ° C. for 24 hours.

Next, the second step in the above manufacturing method will be described. The heat treatment in the second step was performed in a first step and a second step. First, the film-shaped molded body is subjected to a heat treatment in the first stage. The film-shaped molded body was heated to 450 ° C. at a rate of 5 ° C./min in an oxygen gas stream containing water vapor, and then kept at 450 ° C. for 1 hour.

Next, a second stage heat treatment is performed. The film-shaped molded body after the first step is heated to 1200 ° C. at a rate of 10 ° C./min in an oxygen stream,
Thereafter, the temperature was kept at 1200 ° C. for 30 minutes. Throughout the first and second steps, a mixed powder of lead oxide and lead zirconate was placed around the film-like molded body to prevent the lead component from scattering from the film-like molded body.

As described above, the crystal oriented ceramics of Samples A1 to A5 shown in Table 1 were obtained. The above viscosity 5
The crystallographically-oriented ceramic obtained from the 0-poise sol, that is, the sample A1 has a flat surface curved when the film-shaped molded body is dried, and the obtained crystallographically-oriented ceramic does not have a substantially rectangular cross section. The shape became almost elliptical. For other samples, tape-shaped crystal-oriented ceramics having a substantially rectangular cross section could be obtained.

Next, the sample A1 obtained as described above was used.
-Measure the degree of orientation of sample A5. First, the sample was subjected to X-ray diffraction to obtain a pattern of X-ray diffraction intensity. From the pattern of the X-ray diffraction intensity, it was found that all of the samples had a tetragonal perovskite structure as a main phase. Next, from the pattern of the X-ray diffraction intensity, the sample A1
Calculate the degree of orientation of the {100} plane of sample A5. In addition,
The plane orientation of each crystal plane was determined by assuming that the tetragonal bevelskite structure was pseudo-cubic. That is, although all of the samples A1 to A5 are tetragonal, the {100} and {001} planes of the tetragonal were both regarded as pseudo-cubic {100} planes.

Let Σ′I (HKL) / ΣI (hkl) be P according to the above equation (1). The value of P can be derived from the pattern of the X-ray diffraction intensity on the tape-like flat surface of each of the samples A1 to A5. Next, Σ′I ₀ (HKL) / ΣI ₀ (hkl) according to the above _equation 1 is defined as P ₀ . The value of P ₀ can be derived from the X-ray diffraction intensity pattern of the powder obtained by crushing each of the samples A1 to A5. From these, the degree of orientation can be calculated according to Q = (P−P ₀ ) / (1−P ₀ ) according to Equation 1 described above.

However, the diffraction plane (HKL) used in the above derivation was measured by using Cu-Kα as X-rays and changing the diffraction angle 2θ in the range of 20 to 50 degrees. The crystal planes are {100}, {110}, and {111} when A1 to A5 are assumed to be pseudo-cubic. Incidentally, these crystal planes are usually (100), (001), (110), (10) when the structure of the samples A1 to A5 is regarded as tetragonal.
1), (111), (200), and (002). As a result, the degree of orientation of the crystallographically-oriented ceramics of Samples A1 to A5 can be obtained, and this is shown in Table 1.

According to the table, it was found that Samples A1 to A5 had a degree of orientation of 10% or more and were crystal-oriented ceramics according to the present invention. Samples A2 to A4 had a high degree of orientation of 20% or more.

As described above, in the raw material and the manufacturing method according to the present example, when producing a tape-shaped crystal-oriented ceramic having a degree of orientation of 20% or more, the viscosity of the sol-like material needs to be 100 poise or more. I understood that.

Next, the relationship between the state of the slit for forming the film-shaped molded body and the degree of orientation of the obtained crystallographically-oriented ceramic will be described with reference to Samples A6 to A8. For sample A6, the above-mentioned sol having a viscosity of 500 poise was sized 1
A film having a width of 1 mm was formed using a slit of mm × 500 μm, and the film was formed into a crystal-oriented ceramic by the same method as described above.

The samples A7 and A8 had the above viscosity of 50.
A sol having a size of 0 poise was formed into a film-shaped molded product having a width of 5 mm using a slit having a size of 5 mm × 500 μm, and the film-shaped molded product was formed into a crystal-oriented ceramic by the same method as described above. However, the slit used to obtain the sample A8 was scratched in advance, and the average roughness in the width direction was 7 mm.
It was set to 0 μm. The average roughness in the width direction of the slit used for obtaining Samples A6 and A7 was 20 μm. Then, the orientation degree of each of Samples A6 to A8 was measured by the same method as described above.

According to the above, sample A6 did not show a clear flat surface, and the degree of orientation could not be measured. The degree of orientation of Sample A7 was 20%, and the degree of orientation of Sample A8 was 13%. Therefore, in order to prepare a crystalline ceramic having a degree of orientation of 20% or more by comparing Sample A6 with Sample A7,
It was found that the width of the film-shaped molded body was required to be 2 mm or more. Further, by comparing Sample A7 and Sample A8, it was found that, in order to produce a crystalline ceramic having a degree of orientation of 20% or more, the average roughness in the width direction of the slit needs to be about 50 μm or less. .

Next, the electromechanical coupling coefficient and the amount of polarization of the crystallographically-oriented ceramic having the degree of orientation according to the present example were compared between the crystallographically-oriented ceramic having a low degree of orientation and the non-oriented ceramic having the same components. did. First, sample A9
And Sample A10 are the above-described Sample A1 and Sample A, respectively.
This is a sample obtained by laminating 20 crystal-oriented ceramics according to No. 3 to form a laminate, and subjecting the laminate to uniaxial pressing and heat treatment by hot press sintering at 1200 ° C. for 15 minutes. Samples a1 and a2 were obtained by crushing the crystallographically oriented ceramics of Samples A1 and A3, forming them into a bulk, and performing hot press sintering under the same conditions as above. is there.

Electrodes are attached to the samples A9, A10, a1, and a2 by polishing the flat surfaces and depositing gold. Thereafter, polarization treatment was performed by applying an electric field in 100 ° C. silicon oil.
Then, the electromechanical coupling coefficient was measured by the resonance anti-resonance method, and the amount of remanent polarization was measured by the pyroelectric current detection method. The measurement results are shown in Table 2.

According to the table, the electromechanical coupling coefficient and the polarization amount of the samples A9 and A10 having the degree of orientation according to the present invention are higher than those of the samples a1 and a2 having no orientation (degree of orientation 0). I understood. Further, it was found that the electromechanical coupling coefficient and the polarization amount of Sample A10 were higher than those of Sample A9. Therefore, it was found that these characteristics had a positive correlation with the degree of orientation.

As described above, according to the raw material and the manufacturing method of this example, the electromechanical coupling constant is higher than that of the non-oriented one,
It was found that bulk crystallographically oriented ceramics having a polarization amount could be obtained. In addition, since this manufacturing method does not use a special technique or the like, a bulk crystallographically-oriented ceramic can be easily and inexpensively obtained.

[0089]

[Table 1]

[0090]

[Table 2]

Embodiment 2 The uniaxially crystallographically-oriented ceramic of this example is a crystallographically-oriented ceramic made of PZT (zircon / lead titanate) having a specific crystal plane oriented. And the degree of orientation is Lot
It is 10% or more as calculated by the geling method. The characteristics of this crystallographically-oriented ceramic will be described.

Next, the method for producing the crystallographically-oriented ceramic according to the present example will be described in detail, and the rate of temperature rise in the first stage of the second step in the production of the crystallographically-oriented ceramic and the obtained crystallographically-oriented ceramic will be described. The relationship with the degree of orientation will be described using samples B1 to B3 shown in Table 3.

First, the first step in the above manufacturing method will be described. Lead acetate, titanium isopropoxide and zirconium n-propoxide as raw materials were prepared. These raw materials were used when the atomic molar ratio of Pb, Zr, Ti was 100:
It was dissolved in 2-methoxyethanol to give a ratio of 52:48. Thereafter, diethanolamine and one equivalent of water required for hydrolysis were added to this solution, and the mixture was heated at 60 ° C. to form a sol while measuring the viscosity, and the sol when the viscosity reached 500 poise was sampled. .

The above sol-like material was sized 10 mm × 200 μm.
Extrusion molding was performed through a slit of m to obtain a tape-shaped film-like molded product. The average roughness in the width direction of the slit was 5 μm. Next, the film-shaped molded body was dried at a temperature of 100 ° C. for 24 hours.

Next, the second step in the above manufacturing method will be described. The heat treatment in the second step was performed in a first step and a second step. First, the film-shaped molded body is subjected to a heat treatment in the first stage. The above-mentioned film-shaped molded body is heated at 2, 5, 20 ° C. per minute in an oxygen stream containing steam.
The temperature was raised to 450 ° C. at the temperature rising rate, and then maintained at 450 ° C. for 1 hour.

Next, a heat treatment in the second stage is performed. The film-shaped molded body after the first step is heated to 1200 ° C. at a rate of 10 ° C./min in an oxygen stream,
Thereafter, the temperature was maintained at 120 ° C. for 30 minutes. Throughout the first and second steps, a mixed powder of lead oxide and lead zirconate was placed around the film-like molded body to prevent the lead component from scattering from the film-like molded body. Thus, Samples B1 to B3 according to Table 3 were obtained. Further, Embodiment 1
The degree of orientation was measured in the same manner as described above and described in Table 3.

According to the table, it was found that the degree of orientation of Samples B1 and B2 was higher than the degree of orientation of B3, which had a higher heating rate than these. Therefore, it was found that in order to obtain oriented ceramics having an orientation degree of 20% or more, it is necessary to set the heating rate of the heat treatment in the first step of the second step to 10 ° C. or less per minute.

Next, the electromechanical coupling coefficient and the amount of polarization of the crystallographically-oriented ceramic according to this example were compared with those of a non-oriented ceramic having the same components. First, 20 film-like molded bodies produced for producing the above-mentioned samples B1 to B3 were laminated to form a laminate, and the laminate was inserted into a tetrafluoroethylene film, pressed at 100 g / cm ² , and heated at a temperature of 100 g / cm ^2. Heat treatment was performed at 60 ° C. for 1 minute. Thereafter, the temperature was raised to 1200 ° C. at 10 ° C./min in an oxygen gas flow, and then maintained at 1200 ° C. for 2 hours to obtain a bulk crystallographically-oriented ceramic for sample B4.

A sample b1, which is a non-oriented ceramic having the same components as the sample B4, was prepared by mixing powder of lead oxide, titanium oxide, and zirconium oxide with Pb: Ti: Zr = 1: 52: 4.
The mixture was mixed at an atomic ratio of 8, baked at a temperature of 1200 ° C. for 2 hours, and sintered.

The electromechanical coupling constants of the samples B4 and b1 were measured in the same manner as in the first embodiment.
Described in. According to the table, even in the ceramics having the components according to this example, the crystals are oriented,
It has been found that the electromechanical coupling coefficient increases.

A sample B5 obtained by a method different from that described above for producing the crystallographically-oriented ceramic according to this example will be described. In the first step of the method for producing sample B5,
First, a sol-like material similar to the above-mentioned samples B1 to B3 was prepared. The sol was extruded through a slit having a size of 10 mm × 200 μm to obtain a tape-like film-like molded product. However, at the time of the extrusion molding, the film-shaped molded body was extruded not into the air but into an aqueous solution of lead acetate.

[0102] The first stage in the subsequent second step was performed using samples B1 to B1 except that the heating rate was 10 ° C per minute.
Same as 3. The second stage was the same as the samples B1 to B3. Thus, Sample B5 was obtained. When the degree of orientation of the sample B5 was measured in the same manner as in Example 1, it was found to be 35%.

From the above, it can be seen that, when producing a crystallographically oriented ceramic containing a lead component which is easily volatilized, the degree of orientation is increased by forming the film-shaped molded body in a solution containing the lead component. Was.

[0104]

[Table 3]

[0105]

[Table 4]

Embodiment 3 The crystallographically-oriented ceramic of this example is a crystallographically-oriented ceramic made of barium titanate with a specific crystal plane oriented. The degree of orientation is 10% or more as calculated by Lotgering method. The method for producing the crystallographically-oriented ceramic was described in detail, and the electromechanical coupling coefficient and the amount of remanent polarization of the crystallographically-oriented ceramic were compared with those of a non-oriented ceramic having the same components.

First, the first step in the above manufacturing method will be described. A methoxy ethoxide of barium and titanium as raw materials was prepared. These raw materials are represented by an atomic ratio of Ba:
It was dissolved in 2-methoxyethanol so that Ti = 1: 1. The above operation was performed in a glove box in order to prevent the solution from absorbing carbon dioxide in the air. Thereafter, diethanolamine and one equivalent of water required for hydrolysis were added to this solution, and the mixture was heated at 120 ° C. to form a sol while measuring the viscosity.
The sol at the time of 0 poise was sampled.

The above sol was sized to 10 mm × 200 μm.
Extrusion molding was performed through a slit of m to obtain a tape-shaped film-like molded product. The average roughness in the width direction of the slit was 5 μm. Next, the film-shaped molded body was dried at a temperature of 100 ° C. for 24 hours.

Next, 20 sheets of the above film-like molded body were laminated to form a laminate, and the laminate was inserted into a tetrafluoroethylene film, pressed at 50 g / cm ² , and heated at a temperature of 80 g / cm ^2.
Heat treatment was performed at 5 ° C. for 5 minutes. Thereafter, the temperature of the laminated body was increased to 650 ° C. at 5 ° C./min in an oxygen gas stream containing water vapor, and maintained at 650 ° C. for 1 hour. Thereafter, the temperature was raised to 1350 ° C. at 10 ° C. per minute in an oxygen stream, and 1350 ° C.
C. for 2 hours to obtain a bulk crystallographically-oriented ceramic for sample C1. In addition, the degree of orientation was measured in the same manner as in Example 1 and described in Table 5.

A sample c1, which is a non-oriented ceramic having the same components as the sample C1, was manufactured by sintering barium titanate powder at a temperature of 1350 ° C. for 2 hours and sintering. Then, the electromechanical coupling constants of the samples C1 and c1 were measured in the same manner as in the first embodiment.
Described in. According to the table, even in the ceramics having the components according to this example, the crystals are oriented,
It has been found that the electromechanical coupling coefficient increases.

[0111]

[Table 5]

[0112]

As described above, according to the present invention, it is possible to easily and inexpensively manufacture a ceramic in a thick film state, which is excellent in various characteristics depending on a specific crystal orientation, Can be provided.

Claims (4)

[Claims] 1. A film-shaped molded product having a width of 2 mm or more and a thickness of 500 μm or less is prepared by using a solution containing a metal element constituting an oxide polycrystalline ceramic or a viscous sol-like material prepared from the solution. A method for producing a crystallographically-oriented ceramic, comprising: a first step of forming; and a second step of heat-treating the film-shaped formed body. 2. The laminate according to claim 1, wherein a plurality of crystallographically-oriented ceramics obtained by heat-treating the film-shaped molded body are laminated to form a laminate, and the laminate is subjected to uniaxial pressing. A method for producing a crystallographically-oriented ceramic, comprising performing a heat treatment. 3. The method for producing a crystallographically-oriented ceramic according to claim 1, wherein a plurality of the film-shaped molded bodies are laminated, a uniaxial pressure is applied to form a laminated body, and the laminated body is subjected to a heat treatment. 4. The method according to claim 1, wherein:
A method for producing a crystallographically-oriented ceramic, characterized in that the film-shaped molded body is formed by extruding a solution or sol having a viscosity adjusted to 100 poise or more through a slit of an extrusion mold.