JP4366913B2 - Method for producing oriented ceramics - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing oriented ceramics, and more particularly to a method for producing piezoelectric oriented ceramics.
[0002]
[Prior art]
As one of the methods for orienting the crystal direction of the polycrystalline ceramic, ceramic powder particles containing crystal grains having shape anisotropy and a flexible oriented ceramic sheet (oriented ceramic green sheet) containing an organic binder are laminated, A method of firing this is conventionally known (for example, see Non-Patent Document 1).
In this method, crystal grains having large shape anisotropy are prepared in advance, mixed with an organic binder, water, etc. to form a slurry or slip, and then tape-molded to form crystal grains. The oriented ceramic sheets are manufactured using the above, and the oriented ceramic sheets are stacked to a desired thickness, pressure is applied, the ceramic sheets are fixed to each other by an adhesive effect such as an organic binder, and then fired to obtain the oriented ceramics. How to get.
[0003]
[Non-Patent Document 1]
“Ceramic Association Magazine” (1985) Vol. 93, no. 9, P.I. 485-490
[0004]
[Problems to be solved by the invention]
By the way, in order to obtain oriented ceramics having a large thickness by this method, it is necessary to increase the number of laminated oriented ceramic sheets. However, when the number of oriented ceramic sheets is increased, the orientation degree is reduced in the vicinity of the center portion of the oriented ceramic obtained through the firing step, and the orientation degree may vary in the whole oriented ceramic. This is because when a large number of oriented ceramic sheets are stacked to increase the thickness of the laminate, the pressure applied in the crimping process is absorbed by the elasticity of the oriented ceramic sheet itself, compared to the surface portion at the center. It is assumed that this is because only a low pressure is applied.
[0005]
Furthermore, since it is considered that the pressurizing operation at the time of pressure bonding has an effect of increasing the degree of orientation of the oriented ceramic sheet, in order to obtain oriented ceramics having a large thickness and a small variation in the degree of orientation as a whole It is considered that it is necessary to apply pressure evenly to the center of the laminate.
[0006]
On the other hand, even if it is possible to obtain an orientation degree of a certain value or more overall by increasing the pressure applied at the time of crimping and increasing the pressure applied to the central portion, as described above. Since the pressure applied to the central portion is smaller than the pressure applied to the surface portion, it is difficult to eliminate the variation in the degree of orientation itself. In addition, if the pressure is increased, it is necessary to increase the pressure of the crimping machine and to improve the strength of the crimping die, resulting in an increase in manufacturing cost.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing oriented ceramics that can obtain oriented ceramics having a large thickness and a small variation in the degree of orientation as a whole. To do.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the inventors previously laminated oriented ceramic sheets to a thickness that does not cause significant variation in pressure due to thickness, and produced a plurality of pressure-bonded laminates. Furthermore, a large-sized laminate (oriented ceramic) was produced by stacking a plurality of sheets and pressing them.
[0009]
However, with this method, it was not possible to obtain oriented ceramics having a large thickness and a small variation in the degree of orientation. This is presumably due to the fact that in the laminated body once pressed, the organic binder considered to play the role of fixing the oriented ceramic sheets loses its elasticity, and good pressure bonding is not realized.
Based on this knowledge, the inventors have further experimented and studied to complete the present invention.
[0010]
That is, the method for producing an oriented ceramic according to the present invention (Claim 1)
Polyester having an adhesive layer on both sides of a laminated oriented ceramic sheet formed by laminating and pressing a plurality of oriented ceramic sheets containing ceramic powder particles containing crystal grains having shape anisotropy and an organic binder A step of forming a laminated molded body by bonding with an adhesive tape mainly composed of an organic substance selected from polyimide and polyethylene terephthalate ;
Heat-treating the multilayer molded body, removing the adhesive tape from the multilayer molded body , and then firing to sinter the multilayer molded body to obtain an integrated oriented ceramic. Yes.
[0011]
Polyester having an adhesive layer on both sides of a laminated oriented ceramic sheet formed by laminating and pressing a plurality of oriented ceramic sheets containing ceramic powder particles containing crystal grains having shape anisotropy and an organic binder Bonding with an adhesive tape mainly composed of an organic substance selected from polyimide and polyethylene terephthalate , heat treating the resulting laminated molded body, removing the adhesive tape from the laminated molded body, and then firing to obtain a large orientation Even when producing ceramics, it is possible to efficiently produce oriented ceramics having a uniform degree of orientation.
That is, the method for producing oriented ceramics according to the present invention does not depend on pressure bonding to form a laminated molded body, so that there is no variation in the applied pressure between the central portion and the surface portion. It is possible to prevent the occurrence of variation in the orientation degree due to the difference.
Therefore, according to the present invention, it is possible to efficiently produce oriented ceramics having a large thickness and a uniform orientation.
[0012]
However, in the present invention, a laminated oriented ceramic sheet formed by laminating and pressing a plurality of oriented ceramic sheets may be bonded with an adhesive tape by combining the method of pasting with an adhesive tape and the method of crimping. .
[0013]
However, it is desirable that a plurality of oriented ceramic sheets are laminated and pressure-bonded within a range in which variations in the orientation degree of the finally obtained oriented ceramics do not become a problem, and the obtained laminated oriented ceramic sheets are bonded to each other with an adhesive tape. . This makes it possible to efficiently produce oriented ceramics having a constant overall orientation and a large orientation.
[0014]
In addition, when all the oriented ceramic sheets are bonded together without combining the method of bonding and bonding, it is possible to obtain oriented ceramics with a constant overall orientation and a low degree of orientation. it can.
Therefore, by combining the method of pressure-bonding the oriented ceramic sheet and the method of bonding together, and adjusting the combination mode, it becomes possible to control the uniformity of the degree of orientation, the height of the degree of orientation, and the like.
[0015]
Moreover, the electrode material used as an internal electrode may be apply | coated to each oriented ceramic sheet.
[0016]
In the method for producing oriented ceramics according to the present invention, for example, a polyacrylic adhesive or the like can be used as a constituent material of the adhesive layer constituting the adhesive tape. Further, polyester, polyimide, polyethylene terephthalate (PET), or the like can be used as a constituent material of the core material (tape portion) of the adhesive tape, but it is usually preferable to use polyester.
[0017]
Moreover, in the method for producing oriented ceramics of the present invention, the constituent material of the adhesive tape in the laminated molded body is removed in a step of performing a heat treatment on the laminated molded body.
The heat treatment for removing the constituent material of the adhesive tape may be performed at the same time as the binder removal process when the oriented ceramic is fired, or may be performed in another process.
[0018]
In the method for producing oriented ceramics of the present invention, it is desirable to use a material having a layered perovskite structure as a main component as the material having shape anisotropy. Examples of the compound having a layered perovskite structure include BiWO ₆ , CaBi ₂ Nb ₂ O ₉ , SrBi ₂ Nb ₂ O ₉ , BaBi ₂ Nb ₂ O ₉ , PbBi ₂ Nb ₂ O ₉ , CaBi ₂ Ta ₂ O ₉ , SrBi ₂ Ta ₂ O ₉ , BaBi ₂ Ta ₂ O ₉ , PbBi ₂ Ta ₂ O ₉ , Bi ₃ TiNbO ₉ , Bi ₃ TiTaO ₉ , Bi ₄ Ti ₃ O ₁₂ , SrBi ₃ Ti ₂ NbO ₁₂ , BaBi ₃ Ti ₂ NbO ₁₂ PbBi ₃ Ti ₂ NbO ₁₂ , CaBi ₄ Ti ₄ O ₁₅ , SrBi ₄ Ti ₄ O ₁₅ , BaBi ₄ Ti ₄ O ₁₅ , PbBi ₄ Ti ₄ O ₁₅ , Na _0.5 Bi _4.5 Ti ₄ O ₁₅ , K _0.5 Bi _4.5 Ti ₄ O ₁₅ , Ca ₂ Bi ₄ Ti ₅ O ₁₈ , Sr ₂ Bi ₄ Ti ₅ O ₁₈ , Ba ₂ Bi ₄ Ti ₅ O ₁₈ , Pb ₂ Bi ₄ Ti ₅ O ₁₈ , Bi ₆ Ti ₃ WO ₁₈ , Bi ₇ Ti ₄ NbO _21,及, Compounds such as Bi ₁₀ Ti ₃ W ₃ O ₃₀ and the like.
[0019]
In addition, the present invention is applied when the crystal grains having shape anisotropy have at least one shape of a plate shape, a rod shape, a strip shape, a flake shape, a column shape, a scale shape, and a needle shape. As a result, it is possible to efficiently produce oriented ceramics having a large thickness and a small variation in the degree of orientation as a whole.
In addition, it is known that the compound showing a layered perovskite structure has a crystal grain shape of a plate shape, a rod shape, or a needle shape.
[0020]
In addition, by applying the present invention to the manufacture of piezoelectric ceramics using an oriented ceramic material as the piezoelectric material, it is possible to efficiently manufacture piezoelectric ceramics having a large thickness and a small variation in the degree of orientation as a whole. become.
[0021]
【Example】
Hereinafter, examples of the present invention will be shown and the features thereof will be described in more detail.
[0022]
[Production of oriented ceramics]
(1) SrCO ₃ , Bi ₂ O ₃ , Nb ₂ O ₅ , Nd ₂ O ₃ , and MnCO ₃ are prepared as starting materials, and these are represented by the following formula (1):
Sr _0.8 Nd _0.2 Bi ₂ Nb ₂ O ₉ +0.5 wt% MnCO ₃ (1)
The mixture was weighed so as to have the composition represented by the following formula and wet-mixed for about 16 hours using a ball mill to obtain a mixture. In addition, it is known that the material of this composition is useful as a piezoelectric material.
(2) The obtained mixture was dried and calcined at 800 ° C. for 2 hours to obtain a calcined powder of a ceramic material.
(3) The calcined powder and KCl were mixed at a weight ratio of 1: 1 and heat-treated at 900 ° C. to 1100 ° C. for 10 hours. After the heat treatment, KCl was removed by washing with water to obtain a ceramic powder of Sr _0.8 Nd _0.2 Bi ₂ Nb ₂ O ₉ .
It was confirmed with a scanning electron microscope that this ceramic powder had anisotropy in shape and was plate-shaped. The plate-like ceramic powder had a ratio φ / H (aspect ratio) of the maximum diameter φ to the height H of about 5.
(4) Then, a mixed powder of 50 parts by weight of the plate-like ceramic powder and 50 parts by weight of the calcined powder and an appropriate amount of an organic binder, a dispersant, an antifoaming agent, and a surface active agent are mixed to prepare a ceramic slurry. Got.
(5) Then, this ceramic slurry was formed into a sheet by a doctor blade method to obtain an oriented ceramic sheet as a formed body. The oriented ceramic sheet had a thickness of about 60 μm.
(6) This oriented ceramic sheet is cut into a size of about 30 mm × 20 mm, laminated a predetermined number of times, and then subjected to pressure bonding under conditions of 60 ° C., 30 MPa, pressure for 30 seconds, for example, a thickness of 5 mm (sample in Table 1). A primary laminated molded body (laminated oriented ceramic sheet) of No. 1) was obtained.
(7) And, as shown in FIG. 1 (a), a predetermined number of primary laminated molded bodies (laminated oriented ceramic sheets) 1a, 1b are provided on both sides of a core material (tape portion) 2, and adhesive layers 3a, 3b are provided. The laminated molded body 5 having a total thickness of 10 mm was formed by bonding with an adhesive tape 4 mainly composed of organic matter. In addition, as the adhesive tape 4, the adhesive layers 3a and 3b were made of polyacrylic adhesive and the core material (tape portion) 2 was made of polyester, and the thickness was 48 μm.
The laminated molded body 5 is heat-treated at 350 ° C. for 5 hours and at 500 ° C. for 2 hours, and after removing the binder and the adhesive tape, firing is performed at 1150 ° C. for 2 hours. By doing so, as shown in FIG.1 (b), oriented ceramics (laminated molded object after baking) 5a was obtained. The dimension of the obtained oriented ceramics was 24 mm × 16 mm × 8 mm, and was shrunk to about 80% of the size of the primary laminated molded body before firing.
[0023]
Similarly, a primary laminated molded body (laminated oriented ceramic sheet) having a thickness of 6 mm (sample number 2), 7 mm (sample number 3), and 8 mm (sample number 4) is formed, and a predetermined number of these are laminated. A laminated molded body having a full thickness as shown in Sample Nos. 2, 3 and 4 in Table 1 was formed and fired to obtain oriented ceramics (laminated molded body after firing).
[0024]
Further, the oriented ceramic sheets obtained in (5) above are bonded one by one with an adhesive tape to form a laminated molded body having a total thickness of 10 mm, and this is fired to obtain oriented ceramics (laminated molded body after firing). (Sample No. 5 in Table 1).
[0025]
[Production of Oriented Ceramics of Comparative Examples (Sample Nos. 6 and 7 in Table 1)]
As Comparative Example 1 (Sample No. 6 in Table 1), after laminating a predetermined number of oriented ceramic sheets, pressure bonding was performed under the conditions of 60 ° C., 30 MPa, and pressurization for 30 seconds to form a laminated molded body 5 having a thickness of 10 mm. This was heat-treated under the same conditions as in the above example to produce oriented ceramics (laminated molded body after firing) 5a as shown in FIG.
[0026]
Furthermore, as Comparative Example 2 (Sample No. 7 in Table 1), a predetermined number of oriented ceramic sheets were laminated and then subjected to pressure bonding under the conditions of 60 ° C., 30 MPa, and pressurization for 30 seconds. After the multilayer molded body 5 is formed by press-bonding the multilayer molded bodies (laminated oriented ceramic sheets) 11a and 11b again under the conditions of 30 MPa and 30 seconds pressurization at 60 ° C., this is the same as in the case of the above embodiment. The orientation ceramics (laminated molded body after firing) 5a as shown in FIG.
In addition, Table 1 collectively shows a manufacturing method (manufacturing conditions) of each sample.
[0027]
[Table 1]
[0028]
[Observation of the adhesion surface of oriented ceramics and measurement of orientation]
Each sample in Table 1 was cut in a direction perpendicular to the surface bonded by the adhesive tape, and the state of the bonded surface was observed. The results are shown in Table 2.
[0029]
In addition, an X-ray pattern is obtained for the exposed surface area of the surface exposed by polishing the surface of each sample and the exposed internal area of the surface exposed by polishing the surface of the sample in parallel with the surface bonded by the adhesive tape. The peak intensity of each crystal plane was measured by an analysis method (ray source CuKα, 30 kV, 15 mA). For comparison, the peak intensity of each crystal plane of a powder sample obtained by pulverizing each sample was also measured. The degree of orientation F was measured by the Lotgering method using each powder sample as a reference. The results are also shown in Table 2.
[0030]
[Measurement of electromechanical coupling coefficient of oriented ceramics]
As shown in FIGS. 3A and 3B, the size of 1 mm × 1 mm × 5 mm from the surface region 21 a and the inner region 21 b of oriented ceramics (laminated molded body after firing) 5 a (24 mm × 16 mm × 8 mm), respectively. The ceramic bodies 22 (22a) and 22 (22b) were cut out.
[0031]
In this way, silver electrodes are baked on both end surfaces (1 × 1 mm surface) of the ceramic body 22 (22a, 22b) cut out from the surface region 21a and the internal region 21b, and in silicon oil at 100 to 200 ° C. Polarization was performed by applying an electric field of 5 kV / mm between the silver electrodes.
The electromechanical coupling factor k ₃₃ in the polarization already ceramic body using an impedance analyzer was measured by a resonance-antiresonance method. The results are also shown in Table 2.
[0032]
[Table 2]
[0033]
As shown in Table 2, in the sample of sample number 6 (Comparative Example 1), the appearance property of the adhesion surface was good, but the variation in the degree of orientation was large, and the degree of orientation was reduced in the internal region. confirmed.
Further, the sample of the sample No. 6 (Comparative Example 1), although the electromechanical coupling coefficient k ₃₃ of the ceramic body cut from the surface area is as large as 30.5, the electromechanical coupling coefficient of a ceramic body cut from the interior region k ₃₃ is as small as 16.1, it was confirmed variation of the electromechanical coupling factor k ₃₃ in the surface region and the inner region is large.
[0034]
Further, in the sample of Sample No. 7 (Comparative Example 2), the variation in orientation between the surface region and the internal region is relatively small, and the electrical properties of the ceramic body cut out from the surface region and the ceramic body cut out from the internal region are The variation of the mechanical coupling coefficient k ₃₃ is small (electromechanical coupling coefficient k ₃₃ = 31.5 in the surface region, electromechanical coupling coefficient k ₃₃ = 27.1 in the inner region), but the adhesive surface is partially cracked Therefore, it was confirmed that the reliability of the product was low and good oriented ceramics could not be obtained.
[0035]
In contrast, Oite the sample of the sample No. 1-5, it was confirmed appearance properties of the adhesive surface is good.
Particularly, in the samples with a 5mm thickness of the primary molded laminate of Sample No. 1, less variation in the degree of orientation and the electromechanical coupling coefficient k ₃₃ in the surface region and the inner region is obtained oriented ceramics having good properties It was confirmed.
On the other hand, in the samples in which the primary laminate moldings of sample numbers 2, 3, and 4 are 6 mm, 7 mm, and 8 mm, the variation in the degree of orientation and the electromechanical coupling coefficient k ₃₃ between the surface region and the inner region is slightly large. Under the conditions of this embodiment, it was confirmed that the thickness of the primary laminated molded body is preferably less than 6 mm.
Further, in Sample No. 5, the sample was adhered to form a primary laminated article with adhesive tape one by one orientation ceramic sheets, the variation of the orientation degree and the electromechanical coupling coefficient k ₃₃ in the surface region and the inner region is small, Although favorable results were obtained, it was confirmed that the value was slightly small.
[0036]
From the above results, a plurality of oriented ceramic sheets are pressure-bonded to form a primary laminated molded body having a thickness of less than 6 mm, and the degree of orientation in the surface region and the inner region is adopted by adopting a method of bonding them with an adhesive tape. and the electromechanical coupling coefficient variation in k ₃₃ is small and large value, it can be seen that the oriented ceramic having good characteristics can be obtained.
[0037]
[Production of electronic components (piezoelectric ceramic hydrophones)]
An electronic component (piezoelectric ceramic hydrophone) was produced using the oriented ceramics (laminated molded body after firing) of sample number 1 in Table 2.
This piezoelectric ceramic hydrophone is an electronic component that is used as an underwater microphone that sends out sound waves or ultrasonic waves into water or receives sound waves or ultrasonic waves that propagate in water, and applies a pulse voltage between electrodes. It is used to send a sound wave or an ultrasonic wave by driving, or to detect a current or a voltage generated when a sound wave or an ultrasonic wave is received.
[0038]
Hereinafter, the manufacturing method of this piezoelectric ceramic hydrophone will be described.
(1) First, a plurality of ceramic bodies having a size of 1 mm × 1 mm × 5 mm are cut out from the oriented ceramics (laminated molded body after firing) (24 mm × 16 mm × 8 mm) of Sample No. 1 in Table 2.
(2) Next, as shown in FIG. 4, a plurality of ceramic bodies 22 are arranged at predetermined intervals using a jig so that the upper and lower end faces of each ceramic body 22 are exposed. After filling the space between the ceramic bodies with a liquid resin 23 such as epoxy, the liquid resin 23 is cured to form the hydrophone main body 24.
(3) Then, as shown in FIG. 5, silver electrodes 25 are formed by sputtering on both main surfaces of the hydrophone body 24 where the upper and lower end faces of the ceramic body 22 are exposed, and a voltage is applied between the silver electrodes 25. The piezoelectric ceramic hydrophone was obtained by applying and polarizing.
[0039]
Small variations in the degree of orientation and the electromechanical coupling coefficient k ₃₃ in the surface region and the inner region, yet in this piezoceramic hydrophone using oriented ceramic sample No. 1 in Table 2 the value is large, achieve good properties We were able to.
[0040]
In the above embodiment, the case where the piezoelectric ceramic is manufactured using the oriented ceramic material useful as the piezoelectric material has been described as an example. However, the present invention is a case where the oriented ceramic is manufactured using another kind of material. It is also possible to apply widely.
[0041]
In the above embodiment, although the case of using the sheet-shaped ceramic powder _{(Sr 0.8 Nd 0.2 Bi 2 Nb} 2 O 9) has been described as an example, the present invention is other than plate-like, rod-like, strip-like, flake It can be widely applied when using ceramic powder having shape anisotropy such as a shape, columnar shape, scale shape, or needle shape.
[0042]
The present invention is not limited to the above embodiments in other points, and various applications and modifications can be made within the scope of the invention.
[0043]
【The invention's effect】
As described above, the method for producing oriented ceramics according to the present invention (Claim 1) includes laminating and pressing a plurality of oriented ceramic sheets containing ceramic powder particles containing crystal grains having shape anisotropy and an organic binder. The laminated orientated ceramic sheet formed by bonding is bonded with an adhesive tape mainly composed of an organic substance having an adhesive layer on both sides to form a laminated molded body, and the laminated molded body is heat treated to laminate the adhesive tape. After removing from the molded body, firing is performed to sinter the laminated molded body so as to obtain integrated oriented ceramics. Therefore, even when manufacturing oriented ceramics with a large thickness, lamination molding is performed only by pressure bonding. As in the case of the conventional method for forming the body, it is possible to suppress the occurrence of variation in the degree of orientation caused by not applying sufficient pressure to the central portion. To become.
Therefore, according to the present invention, it is possible to efficiently produce oriented ceramics having a large thickness and a uniform orientation.
[0044]
[Brief description of the drawings]
FIG. 1A is a cross-sectional view showing an unfired laminated molded body formed in one step of a method for producing oriented ceramics according to one embodiment of the present invention, and FIG. It is sectional drawing which shows ceramics.
2A is a cross-sectional view schematically showing a sample of a comparative example (sample number 6), and FIG. 2B is a cross-sectional view schematically showing a sample of a comparative example (sample number 7).
FIGS. 3A and 3B are diagrams for explaining a method of cutting a ceramic body from a surface region and an internal region of oriented ceramics, wherein FIG. 3A is a perspective front view and FIG. 3B is a perspective plan view.
FIG. 4 is a diagram for explaining a method of forming a hydrophone body using a plurality of ceramic bodies in a manufacturing process of a piezoelectric ceramic hydrophone.
FIG. 5 is a perspective view showing a piezoelectric ceramic hydrophone.
[Explanation of symbols]
1a, 1b, 11a, 11b Primary laminated molded body (laminated oriented ceramic sheet)
2 Core material (tape part)
3a, 3b Adhesive layer 4 Adhesive tape 5 Laminated molded body 5a Oriented ceramics (Laminated molded body after firing)
21a Surface area 21b Internal area 22 (22a, 22b) Ceramic body 23 Liquid resin 24 Hydrophone body 25 Silver electrode

Claims (1)

Polyester having an adhesive layer on both sides of a laminated oriented ceramic sheet formed by laminating and pressing a plurality of oriented ceramic sheets containing ceramic powder particles containing crystal grains having shape anisotropy and an organic binder A step of forming a laminated molded body by bonding with an adhesive tape mainly composed of an organic substance selected from polyimide and polyethylene terephthalate ;
Heat-treating the multilayer molded body, removing the adhesive tape from the multilayer molded body , and then firing to sinter the multilayer molded body to obtain an integrated oriented ceramic. A method for producing oriented ceramics.

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