JP5922576B2 - Crystal-oriented ceramics and method for producing the same - Google Patents

Description

  The present invention relates to a crystallographically oriented ceramic and a method for producing the same, and more particularly to a crystallographically oriented ceramic in which a specific crystal axis is oriented in one direction and a method for producing the same. A dielectric element, a microwave dielectric element, a thermoelectric element, a pyroelectric element, a magnetoresistive element, a magnetic element, a piezoelectric element, an electrolytically driven displacement element, a resistance element, an electron conduction element, and a thermistor element can be configured.

The general formula is Ln _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} (where Ln is one or more elements selected from rare earth elements, and x is a number in the range of −0.10 ≦ x ≦ 0.33). The rare earth silicate having an apatite-type crystal structure represented by) is relatively excellent in oxide ion conductivity even in the intermediate temperature range of about 500 ° C. to 700 ° C. in Patent Document 1 and Patent Document 2. It has been reported to show. When the oxide ion conductor composed of such an apatite type compound is used as the electrolyte of a solid electrolyte fuel cell, YSZ (yttria stabilized zirconia), SDC (scandina doped ceria), LSGM (lanthanum gallate oxide) Compared to a fuel cell as an electrolyte, there is an advantage that the operating temperature can be lowered and the energy required for heating can be saved. Oxide ion conductors composed of rare earth silicates having such an apatite-type crystal structure are conventionally formed by mixing raw material powders using oxides such as Ln ₂ O ₃ and SiO ₂ as starting materials.・ Using a firing method and using oxides such as Ln ₂ O ₃ and SiO ₂ as starting materials, a powder composed of apatite-type rare earth silicate was synthesized by a solid phase reaction method, and then the synthesized powder was In general, it was produced by a method of molding and sintering.

  On the other hand, the oxide ion conduction characteristics of the apatite-type compound extend in a parallel direction along the c-axis from a single crystal produced by the Bernoulli method, the chocolate ski method, or the like in Patent Document 3 and Non-Patent Document 1. Comparing the oxide ion conductivity of the sample cut out from the location and the location extending in the direction orthogonal to the c-axis, the sample cut out from the location extending in the parallel direction along the c-axis is superior The oxide ion conductivity is high in the parallel direction along the c-axis direction.

In Patent Document 3, after adding apatite-type compound crystal powder to a solvent to form a slurry, the slurry is placed in the presence of a magnetic field, whereby crystals in the slurry are generally oriented. As a result, a molded body having crystals oriented in a specific direction is obtained. By firing such a molded body, a crystal made of an apatite type compound (La ₁₀ Si ₆ 0 ₂₇ ) and having an orientation degree of 42% by Lotgering method and showing anisotropy in oxide ion conductivity Oriented ceramics can be obtained.

  In the method for producing a crystallographically-oriented ceramic disclosed in Patent Document 3, it is necessary to prepare a slurry having an appropriate viscosity, and it is necessary to leave the slurry in a magnetic field together with the container, so that the production process is complicated. There was a problem of becoming.

In Patent Document 4, Bi ₂ O ₃ , Na ₂ CO ₃ , and TiO ₂ are mixed at a predetermined ratio with powder made of plate-like template particles made of bismuth titanate (Bi ₄ Ti ₃ 0 ₁₂ ). By molding and sintering the mixture so that the plate-like powder is oriented, crystal oriented ceramics made of bismuth titanate (Bi _0.5 Na _0.5 Ti0 ₃ ) and having an orientation degree of 34% by the Lotgering method is obtained. be able to.

  In the case of the method disclosed in Patent Document 4, it is necessary to use a large amount of plate-like template particles in order to obtain a crystal-oriented ceramic having a high degree of orientation. However, this method has a problem that it is necessary to synthesize a large amount of well-shaped template particles, which complicates the manufacturing process.

JP-A-8-208333 JP-A-11-130595 JP 2004-244282 A JP-A-10-139552

M. Higuchi, Y. Masubuchi, S. Nakayama, S. Kikkawa, K. Kodaira, K., Solid State Ionics 174, 73-80 (2004). T. Iwata, E. Bechade, K. Fukuda, O. Masson, I. Julien, E. Champion, P. Thomas, J. Am. Ceram. Soc. 91, 3714-3720 (2008). R. Ali, M. Yashima, Y. Matsushita, H. Yoshioka, F. Izumi, J. Solid State Chem. 182, 2846-2851 (2009).

  The present invention provides a crystallographically-oriented ceramic having crystal axes oriented in one direction, and a method for producing a crystallographically-oriented ceramic capable of producing such a crystal-oriented ceramic without going through a complicated process. The purpose is to provide.

The present invention for solving the above problems is as follows.
(1) A crystal-oriented ceramic, in which a compound is formed in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other, and the crystal of the compound is vertically aligned with respect to the original bonding interface. A crystallographically-oriented ceramic characterized in that

(2) A method in which a plurality of substances having different average chemical compositions are brought into contact with each other to have a bonding interface, and this is heated at a predetermined temperature to produce crystal-oriented ceramics, wherein the predetermined temperature is A crystal-oriented ceramic characterized in that element diffusion occurs between a plurality of substances and a temperature at which a new compound is generated, and crystals of the generated compound are vertically aligned with respect to the original bonding interface Manufacturing method.

(3) Lanthanum having an apatite-type crystal structure in the vicinity of the bonding interface where the first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other. A crystal-oriented ceramic, characterized in that an acid salt is formed and the crystal of the lanthanum silicate is oriented along the direction perpendicular to the c-axis with respect to the original bonding interface.

(4) The first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other to have a bonding interface and heated at a predetermined temperature. Thus, a method for producing a crystallographically-oriented ceramic, wherein the predetermined temperature causes element diffusion between the first layer and the second layer, thereby producing a lanthanum silicate having an apatite type crystal structure. A method for producing a crystallographically-oriented ceramic, characterized in that the generated lanthanum silicate crystals are oriented along a direction perpendicular to the original c-axis with respect to the original bonding interface.

(5) A lanthanum silicate having an apatite-type crystal structure is formed in the vicinity of the bonding interface where the first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of SiO ₂ are brought into contact with each other. The crystal of the lanthanum silicate is characterized in that the c-axis is oriented along the direction perpendicular to the original bonding interface.

(6) A structure in which a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of SiO ₂ are brought into contact with each other to form a bonding interface, and this is heated at a predetermined temperature. In the method for producing oriented ceramics, the predetermined temperature is a temperature at which element diffusion occurs between the first layer and the second layer and a lanthanum silicate having an apatite type crystal structure is generated. A method for producing a crystallographically-oriented ceramic, wherein the produced lanthanum silicate crystal has a c-axis oriented along a direction perpendicular to the original bonding interface.

(7) A lanthanum crystal having an apatite-type crystal structure in the vicinity of the bonding interface where the first layer mainly composed of La ₂ O ₃ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other. A crystal-oriented ceramic, characterized in that an acid salt is formed and the crystal of the lanthanum silicate is oriented along the direction perpendicular to the c-axis with respect to the original bonding interface.

(8) The first layer mainly composed of La ₂ O ₃ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other to have a bonding interface and heated at a predetermined temperature. Thus, a method for producing a crystallographically-oriented ceramic, wherein the predetermined temperature causes element diffusion between the first layer and the second layer, thereby producing a lanthanum silicate having an apatite type crystal structure. A method for producing a crystallographically-oriented ceramic, characterized in that the generated lanthanum silicate crystals are oriented along a direction perpendicular to the original c-axis with respect to the original bonding interface.

(9) A lanthanum silicate having an apatite-type crystal structure is formed in the vicinity of the bonding interface where the first layer mainly composed of SiO ₂ and the second layer mainly composed of La ₂ SiO ₅ are brought into contact with each other. The crystal of the lanthanum silicate is characterized in that the c-axis is oriented along the direction perpendicular to the original bonding interface.

(10) A structure in which a first layer mainly composed of SiO ₂ and a second layer mainly composed of La ₂ SiO ₅ are brought into contact with each other to have a bonding interface, and this is heated at a predetermined temperature. In the method for producing oriented ceramics, the predetermined temperature is a temperature at which element diffusion occurs between the first layer and the second layer and a lanthanum silicate having an apatite type crystal structure is generated. A method for producing a crystallographically-oriented ceramic, wherein the produced lanthanum silicate crystal has a c-axis oriented along a direction perpendicular to the original bonding interface.

(11) A crystallographically-oriented ceramic comprising a compound produced in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other and having a crystal structure perpendicularly oriented with respect to the original bonding interface.

(12) The compound according to (11), wherein the compound is a lanthanum silicate having an apatite-type crystal structure and has a crystal structure in which a c-axis is oriented along a vertical direction with respect to the original bonding interface. Crystal oriented ceramics.

(13) The plurality of substances include a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of La ₂ Si ₂ O ₇ . Crystalline oriented ceramics.

(14) The crystal-oriented ceramic according to (12), wherein the plurality of substances include a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of SiO ₂ .

(15) The plurality of substances includes a first layer mainly containing La ₂ O ₃ and a second layer mainly containing La ₂ Si ₂ O ₇ . Crystalline oriented ceramics.

(16) A step of bringing a plurality of substances having different average chemical compositions into contact with each other to have a bonding interface, and heating the plurality of substances having the above-described structure at a temperature at which element diffusion occurs between the plurality of substances. And producing a crystallographically-oriented ceramic in the vicinity of the bonding interface,
The method for producing a crystallographically-oriented ceramic, wherein the crystallographically-oriented ceramic is made of a compound having a crystal structure that is vertically aligned with respect to the original bonding interface.

(17) The compound according to (16), wherein the compound is a lanthanum silicate having an apatite-type crystal structure, and has a crystal structure in which a c-axis is oriented along a vertical direction with respect to the original bonding interface. A method for producing crystal-oriented ceramics.

(18) The plurality of substances according to (17), wherein the plurality of substances are a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of La ₂ Si ₂ O ₇ . A method for producing crystal-oriented ceramics.

(19) The crystal-oriented ceramic according to (17), wherein the plurality of substances are a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of SiO ₂ . Production method.

(20) The plurality of substances according to (17), wherein the plurality of substances are a first layer mainly composed of La ₂ O ₃ and a second layer mainly composed of La ₂ Si ₂ O ₇ . A method for producing crystal-oriented ceramics.

(21) The method for producing a crystallographically-oriented ceramic according to (16), further comprising a step of removing a substance other than the produced crystallographically-oriented ceramic.

(22) The method for producing a crystal-oriented ceramic according to any one of (17) to (20), further comprising a step of removing a substance other than the produced lanthanum silicate crystals.

(23) A plate-like body composed of lanthanum silicate having an apatite-type crystal structure, wherein the c-axis of the lanthanum silicate has a crystal structure oriented along a direction perpendicular to the main surface of the plate-like body A plate-like body.

(24) The plate-like body according to (23), wherein the main surface of the plate-like body is a flat surface or a curved surface.

(25) Diffusion by bringing a substance composed of at least one selected from La ₂ SiO ₅ and La ₂ O ₃ into contact with a substance consisting of at least one selected from La ₂ Si ₂ O ₇ and SiO ₂ A plate-like body made of lanthanum silicate having an apatite type crystal structure according to (23), wherein the main surface is formed by heating the diffusion pair and then removing the surface thereof.

(26) The plate-like body according to (23), wherein the lanthanum silicate having an apatite-type crystal structure has a crystal orientation of 49% or more.

  According to the present invention, it is possible to provide a crystallographically-oriented ceramic in which the crystal axis is oriented in one direction, and a crystal-oriented ceramic that can produce such a crystal-oriented ceramic without going through a complicated process. A manufacturing method can be provided.

2 is a reflection micrograph of a diffusion pair sample obtained in Example 1. 2 is a microscopic Raman spectrum of a diffusion pair sample obtained in Example 1. FIG. (A) is a Raman spectrum from La ₂ SiO ₅ , (b) is a Raman spectrum from apatite-type lanthanum silicate, and (c) is a Raman spectrum from La ₂ Si ₂ O ₇ . FIG. 3 is a polarization micrograph of the diffusion pair sample obtained in Example 1, in which almost all columnar crystals of apatite-type lanthanum silicate are in a diagonal position. Arrow P represents the vibration direction of the polarizer, and arrow A represents the vibration direction of the analyzer. FIG. 2 is a polarization micrograph of a diffusion pair sample obtained in Example 1, and almost all columnar crystals of apatite-type lanthanum silicate are in the extinction position. Arrow P represents the vibration direction of the polarizer, and arrow A represents the vibration direction of the analyzer. 2 is an X-ray powder diffraction pattern of the crystallographically-oriented ceramic obtained in Example 1. FIG. 3 is an X-ray powder diffraction pattern of the crystallographically-oriented ceramic obtained in Example 2. 4 is an X-ray powder diffraction pattern of the crystallographically-oriented ceramic obtained in Example 3. 4 is a reflection micrograph of a diffusion pair sample obtained in Example 3. It is a polarization microscope photograph of the diagonal position of the diffusion pair sample obtained in Example 3, and almost all columnar crystals of the apatite type lanthanum silicate are in the diagonal position. Arrow P indicates the vibration direction of the polarizer, and arrow A indicates the vibration direction of the analyzer. It is a polarization microscope photograph of the extinction position of the diffusion pair sample obtained in Example 3, and almost all columnar crystals of the apatite type lanthanum silicate are in the extinction position. Arrow P indicates the vibration direction of the polarizer, and arrow A indicates the vibration direction of the analyzer. 4 is an X-ray powder diffraction pattern of the crystallographically-oriented ceramic obtained in Example 4. 4 is a reflection micrograph of a diffusion pair sample obtained in Example 4. It is a polarization microscope photograph of the diagonal position of the diffusion pair sample obtained in Example 4, and almost all columnar crystals of the apatite type lanthanum silicate are in the diagonal position. Arrow P indicates the vibration direction of the polarizer, and arrow A indicates the vibration direction of the analyzer. FIG. 6 is a polarization micrograph of the extinction position of the diffusion pair sample obtained in Example 4, and almost all of the columnar crystals of apatite type lanthanum silicate are in the extinction position. Arrow P indicates the vibration direction of the polarizer, and arrow A indicates the vibration direction of the analyzer. 6 is a reflection micrograph of a diffusion pair sample obtained in Example 5. It is a polarization microscope photograph of the diagonal position of the diffusion pair sample obtained in Example 5, and almost all columnar crystals of the apatite type lanthanum silicate are in the diagonal position. Arrow P indicates the vibration direction of the polarizer, and arrow A indicates the vibration direction of the analyzer. FIG. 6 is a polarization micrograph of the extinction level of the diffusion pair sample obtained in Example 5, and almost all of the columnar crystals of apatite type lanthanum silicate are in the extinction position. Arrow P indicates the vibration direction of the polarizer, and arrow A indicates the vibration direction of the analyzer. 7 is an X-ray powder diffraction pattern of the crystallographically-oriented ceramic obtained in Example 5. 7 is an X-ray powder diffraction pattern of the crystallographically-oriented ceramic obtained in Example 6. It is a chart which shows the EPMA measurement result of the crystal orientation ceramics to which this invention is applied. It is the figure which added the regression line to the chart which shows the EPMA measurement result of FIG.

The present invention is a crystal-oriented ceramic, in which a compound is formed in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other, and the crystal of the compound is oriented vertically to the original bonding interface. It is characterized by. Further, the present invention is a method for producing a crystallographically-oriented ceramic by bringing a plurality of substances having different average chemical compositions into contact with each other and having a bonding interface and heating the material at a predetermined temperature. The temperature is a temperature at which element diffusion occurs between the plurality of substances and a new compound is formed, and crystals of the generated compound are vertically oriented with respect to the original bonding interface. .
Here, “ceramics” in the present invention refers to a substance having a crystal structure by heating.

  Specifically, diffusion is performed using two substances whose average chemical compositions are different from each other (however, the shape and state of this substance are arbitrary and are not particularly specified such as a green compact or a sintered body). By forming a pair and heating these diffusion pairs at a high temperature, a new compound is formed in the vicinity of the bonding interface, so that the specific crystal axis of this compound is in a direction perpendicular to the original bonding interface. A crystallographically-oriented ceramic is provided that is oriented in one direction along.

In the present invention, the diffusion pair is heated at a predetermined temperature to produce crystal oriented ceramics. The predetermined temperature is preferably 1300 ° C. or higher, and more preferably 1400 ° C. or higher. However, it is preferable to appropriately set the heating temperature and the like in consideration of the correlation between the heating temperature and the heating time and the thickness of the layer of the crystal oriented ceramics to be generated. Specifically, in order to obtain crystal-oriented ceramics with a constant thickness, the heating time may be short at high temperatures, whereas the heating time needs to be long at low temperatures. It is preferable to set the heating temperature in consideration of the relationship.
In Table 1 below, La ₂ SiO ₅ and La ₂ Si ₂ O ₇ are used as two substances having different average chemical compositions, and a layer of crystallographically oriented ceramics is produced by changing the heating temperature and heating time. Show. As shown in Table 1, based on the correlation between the heating temperature and the heating time and the thickness of the crystal oriented ceramic layer to be produced, the crystal oriented ceramic having a desired thickness can be obtained by appropriately setting the heating temperature and the heating time. Can be generated. In Table 1, “La ₂ SiO ₅ side” and “La ₂ Si ₂ O ₇ side” mean the thickness of the produced crystal-oriented ceramic layer on the La ₂ SiO ₅ side and La ₂ Si ₂ O _{7, respectively.} The “thickness” is the sum of “La ₂ SiO ₅ side” and “La ₂ Si ₂ O ₇ side”, and is a one-dimensional oriented crystal layer (crystal oriented ceramic layer) of an apatite structure Indicates the thickness. Also, in Table 1, the sum of the thickness of “La ₂ SiO ₅ side” and the thickness of “La ₂ Si ₂ O ₇ side” and the thickness of the layer of crystallographically oriented ceramics are completely rounded off to the nearest whole number. Does not match.
The heating temperature is preferably 1400 to 1600 ° C., preferably 1500 ° C. to 1600 ° C., and the heating time is preferably 5 hours to 100 hours, and preferably 25 hours to 50 hours. The heating atmosphere is air or an oxygen atmosphere. The reason why such conditions are desirable is that the desired apatite structure layer (crystal-oriented ceramic layer) is formed and that the amount of oxygen in the crystal is insufficient and the ionic conductivity is not lowered.

In the present invention, the new compound generated near the bonding interface may be generated not only on both sides of the bonding interface but also on one side.
Furthermore, in the present invention, a substance having a chemical composition different from the chemical composition of the substrate is dispersed in close contact with the surface of the substrate having a certain chemical composition by a method such as spray coating or dip coating, and heated at a high temperature. By doing so, highly oriented ceramics may be generated on the substrate surface. This method is similar to the diffusion pair method described above in that a new compound is generated in the vicinity of the bonding interface between two substances having different average chemical compositions.

More specifically, diffusion is performed using a substance composed of a single or plural phases whose average chemical composition is represented by A and a substance composed of a single or plural phases whose average chemical composition is represented by B. By forming a pair and heating at a high temperature, element diffusion occurs in the vicinity of the bonding interface, and the general formula is A _x B _1-x (where x is a number in the range of 0 <x <1). The specific crystal axis of the compound A _x B _1-x is oriented in one direction along the direction perpendicular to the original bonding interface by generating a new compound represented by It is to provide crystal-oriented ceramics.

According to Non-Patent Document 2 and Non-Patent Document 3, the general formula of lanthanum silicate having an apatite crystal structure is La _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} (where x is −0.10 ≦ x ≦ It is a number in the range of 0.33.) Therefore, lanthanum silicate having an apatite type crystal structure is produced by reacting La ₂ SiO ₅ and La ₂ Si ₂ O ₇ at a high temperature, reacting La ₂ SiO ₅ and SiO ₂ at a high temperature, or Since La ₂ Si ₂ O ₇ and La ₂ O ₃ are produced by a reaction at a high temperature, these three kinds of combinations were selected as a combination of diffusion pairs in Examples described later.
In the present invention, a compound containing a rare earth element other than lanthanum can also be used.

According to another expression, the crystal-oriented ceramic of the present invention is composed of a compound formed in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other, and is vertically aligned with respect to the original bonding interface. It is characterized by having a crystal structure. That is, as described above, the crystal oriented ceramic is a crystal oriented ceramic in which a specific crystal axis is oriented in one direction along a direction perpendicular to the original bonding interface. In addition, the degree of orientation of the crystal-oriented ceramic of the present invention is 49% or higher, which is higher than that of the conventional one. The reason why the degree of orientation is desirably 49% or more is that the oxygen ion conductivity of the entire structure is improved when the degree of orientation with respect to the c-axis, which is the moving direction of oxygen ions, is increased.
The compound can be a lanthanum silicate having an apatite-type crystal structure, and in this case, has a crystal structure in which the c-axis is oriented along the vertical direction with respect to the original bonding interface.

The crystal-oriented ceramic of the present invention includes (1) a first layer mainly composed of La ₂ SiO ₅ and a main component composed of La ₂ Si ₂ O ₇ as a plurality of substances having different average chemical compositions. An aspect including the second layer, (2) an aspect including the first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of SiO ₂ , or (3) La ₂ O _An embodiment including a first layer mainly containing 3 and a second layer mainly containing La ₂ Si ₂ O ₇ is preferable. In any embodiment, the compound generated at the bonding interface between the first layer and the second layer is a compound having a crystal structure in which the c-axis is vertically aligned with respect to the bonding interface, that is, the crystal orientation of the present invention. Ceramics.

Since the crystallographic ceramics of the present invention have crystal axes oriented in one direction, the ion conductivity in the direction along the direction is high, and are useful as an ion conductor.
As a specific example, the ionic conductivity of lanthanum silicate (La _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} (0.02 ≦ x ≦ 0.13)) having an apatite-type crystal structure as the crystal-oriented ceramic of the present invention is shown. When measured, it was 5.0 × 10 ⁻³ (S / cm) at 400 ° C., whereas the ionic conductivity of La _9.33 (SiO ₄ ) ₆ O ₂ outside the scope of the present invention is a literature value. It is about 5.33 × 10 ⁻⁶ (S / cm) at 300 ° C. and about 2.31 × 10 ⁻⁴ (S / cm) at 500 ° C. (S. Tao and JTS Irvine, Materials Research Bulletin 36, 1245-1258 (2001)). That is, the ionic conductivity (5.0 × 10 ⁻³ (S / cm)) at 400 ° C. of the crystal-oriented ceramic of the present invention is the ionic conductivity at 500 ° C. (about 2.31 × 10 ⁻⁴ (S In other words, the crystal-oriented ceramic of the present invention is 400 ° C. lower than the reference value of 500 ° C., but the ionic conductivity is one order of magnitude higher than the reference value. A large value was shown.
Here, the ionic conductivity of the crystal-oriented ceramic of the present invention was obtained as follows. First, after a sample was formed into a 3 mm × 3 mm test piece (thickness 0.4 mm), a platinum thin film (thickness: 0.4 μm) was formed on the front and back surfaces of the test piece by sputtering. Next, using the formed platinum thin film as an electrode, the bulk resistance between the electrodes was measured by the AC impedance method, and the ionic conductivity was calculated from the bulk resistance and the size of the test piece. The platinum thin film can also be formed by baking a platinum paste.
In addition, unreacted layers, that is, layers other than the crystal-oriented ceramics were removed by grinding (sandpaper # 200), and further, grinding (sandpaper # 200, sandpaper # 1200) was advanced until the original bonding interface could be removed. .
Measurement conditions and equipment used are as follows.
[Measurement conditions and equipment used]
・ Measurement frequency: 0.1-1MHz
Measurement temperature: room temperature to 400 ° C
-Furnace atmosphere: Atmosphere-PC software: Toyo Technica Co., Ltd., ZPlot
-Frequency response analyzer: manufactured by Toyo Technica Co., Ltd., 1260 type-Desktop lamp heating furnace: manufactured by ULVAC-RIKO, Inc., MILA-3000

On the other hand, the EPMA analysis result of the lanthanum silicate which is the crystal-oriented ceramic of the present invention is shown. Specifically, a diffusion composed of a first layer mainly composed of La ₂ SiO ₅ as a plurality of substances having different average chemical compositions and a second layer mainly composed of La ₂ Si ₂ O ₇ The results of EPMA analysis of the laminate after forming a pair and heating the diffusion pair at a high temperature to form lanthanum silicate in the vicinity of the bonding interface are shown. FIG. 20 is a chart showing the results of the EPMA analysis. In FIG. 20, the horizontal axis indicates the distance (μm) from the end face of La ₂ SiO ₅ , and the vertical axis indicates the value of the ratio of La to Si (La / Si). That is, FIG. 20 shows the La / Si ratio at a predetermined distance from the end face of La ₂ SiO ₅ , the points distributed on the left are La ₂ SiO ₅ analysis points, and the points distributed on the right are La ₂ Si _2. The analysis points of O _{7 and} the points distributed in the middle are the analysis points of lanthanum silicate produced.
FIG. 20 shows that lanthanum silicate has a high La / Si ratio on the La ₂ SiO ₅ side and gradually decreases toward the La ₂ Si ₂ O ₇ side. FIG. 21 shows a regression line added to the points distributed in FIG. As shown in FIG. 21, the regression line of La ₂ SiO ₅ and La ₂ Si ₂ O ₇ was a straight line with a slope of 0, whereas the regression line of lanthanum silicate was y = (− 1 .12 × 10 ⁻⁴ ) x + 1.636.

The composition formula of lanthanum silicate having an apatite structure is represented by La _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} , and the ionic conductivity is higher when the value of x is larger than 0. That is, the ionic conductivity is higher when the La / Si ratio in lanthanum silicate is larger than 1.555 (= 9.33 / 6). As shown in FIG. 20 and FIG. 21, the lanthanum silicate, which is the crystal-oriented ceramic of the present invention, is presumed to exhibit high ionic conductivity because the La / Si ratio is larger than 1.555. It is clear that the ionic conductivity is high.

On the other hand, according to another expression, the method for producing a crystal-oriented ceramic according to the present invention includes a step of bringing a plurality of substances having different average chemical compositions into contact with each other to have a bonding interface, and the plurality of substances having the above-described configuration. Heating at a temperature at which element diffusion occurs between the plurality of substances to produce crystal oriented ceramics in the vicinity of the joint interface, wherein the crystal oriented ceramics are vertically oriented with respect to the original joint interface It is characterized by comprising a compound having a crystal structure. According to the manufacturing method of the present invention, a crystal-oriented ceramic having a high degree of orientation can be obtained without complicating the manufacturing process as in the prior art.
The compound can be a lanthanum silicate having an apatite-type crystal structure, and in this case, has a crystal structure in which the c-axis is oriented along the vertical direction with respect to the original bonding interface.

  The plurality of substances having different average chemical compositions are the same as those of the crystal-oriented ceramic of the present invention described above, and preferred examples are also the same.

In the method for producing a crystal-oriented ceramic according to the present invention, a substance other than the crystal-oriented ceramic generated near the bonding interface of the plurality of substances or a substance other than lanthanum silicate having an apatite-type crystal structure is unnecessary. It is preferable to provide a step of removing the substance.
The removing means is not particularly limited, and examples thereof include mechanical means such as polishing and grinding, chemical means such as etching, and peeling due to a difference in thermal expansion coefficient.

The crystal-oriented ceramic of the present invention is preferably made into a plate-like body by removing a reaction raw material such as La ₂ SiO ₅ . That is, a plate-like body made of lanthanum silicate having an apatite-type crystal structure, wherein the lanthanum silicate has a crystal structure in which the c-axis of the lanthanum silicate is oriented in a direction substantially perpendicular to the main surface of the plate-like body. Is a plate-like body. The reason why the crystal-oriented ceramic is a plate-like body is that it is a suitable shape when used as a solid electrolyte such as an oxygen sensor.

The main surface of the plate-like body may be either a flat surface or a curved surface, but it is desirable that the normal direction of the main surface coincides with the orientation direction of the c-axis.
The plate-like body includes a substance A composed of at least one selected from La ₂ SiO ₅ and La ₂ O ₃ and a substance B composed of at least one selected from La ₂ Si ₂ O ₇ and SiO _2. To obtain a lanthanum silicate polycrystal having an apatite-type crystal structure by heating the diffusion pair, and then the substances A and / or remaining on the surface of the lanthanum silicate polycrystal Alternatively, the main surface of the plate-like body is formed by removing the substance B.
As described above, the removing method is not particularly limited, and examples thereof include mechanical means such as polishing and grinding, chemical means such as etching, and peeling due to a difference in thermal expansion coefficient.
The crystal orientation degree of the lanthanum silicate having the apatite type crystal structure is preferably 49% or more. This is because the oxygen ion conductivity of the entire structure is improved when the degree of orientation with respect to the c-axis, which is the moving direction of oxygen ions, is increased.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following examples, a diffusion pair is prepared using raw powders of La ₂ SiO ₅ and La ₂ Si ₂ O ₇ , SiO ₂ , and La ₂ O ₃ , and these are heated at a high temperature so that the c-axis is A method for producing a lanthanum silicate polycrystal having an apatite-type crystal structure oriented in one direction will be described. These are examples, and La ₂ SiO ₅ and La ₂ Si ₂ O ₇ , SiO ₂ , La ₂ Needless to say, the present invention can be realized even when a highly oriented ceramic having a chemical composition and crystal structure different from that of lanthanum silicate is manufactured using a diffusion pair having a chemical composition different from that of O ₃ .

  In Examples 1 to 5 of the present invention, a diffusion pair is prepared using two green compacts having different chemical compositions, and heated at a high temperature to generate highly oriented ceramics in the vicinity of the bonding interface. However, as described in Example 6, a substance having a chemical composition different from the chemical composition of the substrate is dispersed and closely adhered to the surface of the substrate having a certain chemical composition by a method such as spray coating or dip coating. Needless to say, the present invention is realized even when highly oriented ceramics are produced on the substrate surface by heating at a high temperature.

Example 1
In this example, it has an apatite type crystal structure obtained by diffusion pair using a green compact whose chemical formula is represented by La ₂ SiO ₅ and a green compact whose chemical formula is represented by La ₂ Si ₂ O _7. A method for producing c-axis oriented ceramics of lanthanum silicate will be described.

As starting materials, a lanthanum oxide (La ₂ O ₃ ) reagent and a silicon oxide (SiO ₂ ) reagent were weighed in such a ratio that a composition having a chemical composition represented by La ₂ SiO ₅ was produced to prepare a raw material mixed powder. This raw material mixed powder was uniaxially pressed into a pellet having a diameter of about 12 mm and a height of about 3 mm, heated in an electric furnace at 1200 ° C. for 1 hour, then taken out of the electric furnace and cooled. The obtained sample is pulverized and mixed, and this powder sample is uniaxially pressed into a pellet with a diameter of about 12 mm and a height of about 3 mm, heated in an electric furnace at 1600 ° C. for 3 hours, and then removed from the electric furnace. And cooled. The obtained sample was pulverized to obtain a powdery La ₂ SiO ₅ sample.

In addition, lanthanum oxide (La ₂ O ₃ ) and silicon oxide (SiO ₂ ) were weighed as starting materials at a rate that a composition represented by a chemical composition represented by La ₂ Si ₂ O ₇ was produced to prepare a raw material mixed powder. . This raw material mixed powder was uniaxially pressed into a pellet having a diameter of about 12 mm and a height of about 3 mm, heated in an electric furnace at 1200 ° C. for 1 hour, then taken out of the electric furnace and cooled. The obtained sample is pulverized and mixed, and this powder sample is uniaxially pressed into a pellet with a diameter of about 12 mm and a height of about 3 mm, heated in an electric furnace at 1600 ° C. for 3 hours, and then removed from the electric furnace. And cooled. The obtained sample was pulverized to obtain a powdery La ₂ Si ₂ O ₇ sample.

A powdery La ₂ SiO ₅ sample (about 0.63 g) was uniaxially pressed to produce a pellet-shaped green compact having a diameter of about 12 mm and a height of about 2 mm. Further, a powdery La ₂ Si ₂ O ₇ sample (about 0.54 g) was uniaxially pressed to produce a pellet-shaped green compact having a diameter of about 12 mm and a height of about 2 mm. A plurality of diffusion pairs in which these two green compacts were superimposed were prepared, heated in an electric furnace at 1600 ° C for 25 hours, and then cooled to room temperature with the furnace turned off for about 3 hours. .

One of the heat-treated diffusion pair samples was cut out with a diamond cutter in a direction perpendicular to the original bonding surface, and the cross section was mirror-polished with a diamond paste to produce a polished piece. When the polished surface was observed with a reflection microscope, a strip-shaped reaction product having a thickness of about 380 μm was observed on both sides of the original bonding interface (FIG. 1). This reaction product is generated on both sides of the original bonding interface, the thickness of the band-like product on the La ₂ SiO ₅ side is about 230 μm, and the band-like product on the La ₂ Si ₂ O ₇ side is The thickness is about 150 μm. When this reaction product was identified using micro-Raman spectroscopy (Fig. 2), it was lanthanum silicate having an apatite-type crystal structure on both sides of the bonding interface, so (10 + 6x) La ₂ SiO ₅ + ( 4-3x) La ₂ Si ₂ O ₇ → 3La _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} (where x is a number in the range of −0.10 ≦ x ≦ 0.33) It is considered that apatite-type lanthanum silicate was generated from La ₂ SiO ₅ and La ₂ Si ₂ O ₇ .

The polishing surface of the polishing piece was attached to a slide glass using an epoxy resin, and an excess portion was cut off using a diamond cutter, and then polished with emery paper and diamond paste to produce a thin piece. When the microstructure was observed with an orthogonal polar using a polarizing microscope (Fig. 3), a columnar crystal with a height of about 230μm and a width of about 45μm was found at the interface on the La ₂ SiO ₅ side of the original bonding interface. It is observed that the crystals grow and gather vertically, and a columnar crystal with a size of about 150 μm in height and about 45 μm in width is formed at the interface on the La ₂ Si ₂ O ₇ side of the original junction interface. It was observed that the crystals grew vertically and assembled. When the state of quenching was observed with an orthogonal polar (FIG. 4), it was confirmed that the entire columnar crystal of apatite-type lanthanum silicate was directly quenched. Since the crystal structure of apatite-type lanthanum silicate belongs to the hexagonal system, it is optically uniaxial, and its optical axis coincides with the crystallographic c-axis. Therefore, it is expected that the apatite-type lanthanum silicate polycrystal formed in the vicinity of the original bonding interface of the diffusion pair substantially matches the c-axis direction of the individual crystal grains. Therefore, the crystallographic orientation of the apatite-type lanthanum silicate polycrystal was investigated by X-ray diffraction.

One of the heat treated diffusion pair samples was cut with a diamond cutter in a direction parallel to the original bonding interface so that the apatite-type lanthanum silicate polycrystal was exposed, and the cross section was mirror-polished using a diamond pace. Thus, a polished piece was produced. In order to investigate the crystallographic orientation of the apatite-type lanthanum silicate polycrystal exposed on the polished surface, a high-resolution X-ray powder diffractometer using CuKα ₁ line (45kV × 40mA) as incident light was used. The profile intensity of the diffracted X-rays in the 2θ range from ° to 90.0 ° was measured (FIG. 5). In the X-ray powder diffraction pattern, reflections with diffraction plane indices of 002, 004, and 006 are remarkably observed. Therefore, the apatite-type lanthanum silicate polycrystal has a c-axis along the direction perpendicular to the original bonding interface. Were confirmed to be oriented.

  The degree of orientation of this polycrystal can be calculated from the Lotgering equation shown in Equation (1).

In the formula (1), ρ ₀ is the sum of the intensities of all diffracted reflections that appear between 10.0 ° and 90.0 ° in the 2θ range of diffracted X-rays in the unoriented apatite-type lanthanum silicate, and the diffraction plane index Is obtained by equation (2) using the sum of the diffraction reflection intensities of 002 and 004, 006.

However, ΣI ₀ (hkl) in equation (2) represents the total intensity of total diffraction reflections that appeared in the 2θ range between 10.0 ° and 90.0 °, and ΣI ₀ (00l) in equation (2) is the diffraction plane index. Represents the sum of the diffraction reflection intensities of 002 and 004, 006.

  On the other hand, ρ in the formula (1) is the sum of the total diffraction reflection intensities appearing when the 2θ range of diffracted X-rays is between 10.0 ° and 90.0 ° in the oriented apatite-type lanthanum silicate, and the diffraction plane index is Using the sum of the diffraction reflection intensities of 002, 004, and 006, it is obtained by equation (3).

  However, ΣI (hkl) in equation (3) represents the total intensity of all diffraction reflections that appeared in the 2θ range between 10.0 ° and 90.0 °, and Σ (00l) in equation (3) has a diffractive surface index of 002. And the sum of the diffraction reflection intensities of 004 and 006. Using the above formulas (1) to (3), the degree of orientation of this polycrystal is found to be 79%, which is an extremely high degree of orientation.

  The reason why the c-axis of the apatite-type lanthanum silicate crystal is oriented along the direction perpendicular to the original bonding interface is not yet elucidated, but the growth rate of the crystal plane perpendicular to the c-axis is different from that of other crystals. It is considered that a columnar crystal extending in the c-axis direction is generated because it is faster than the growth rate of the surface.

(Example 2)
In the present example, similar to Example 1, it is obtained by a diffusion pair using a green compact whose chemical formula is represented by La ₂ SiO ₅ and a green compact whose chemical formula is represented by La ₂ Si ₂ O _7. A method for producing a highly oriented ceramic of apatite type lanthanum silicate will be described. In this example, the thickness of the La ₂ SiO ₅ compact forming the diffusion pair is thinner than that used in Example 1, and the La ₂ SiO ₅ layer is completely formed after the diffusion pair is heat-treated. The apatite-type lanthanum silicate is exposed on the surface.

A powdery La ₂ SiO ₅ sample and a powdery La ₂ Si ₂ O ₇ sample were synthesized in the same manner as described in Example 1, respectively. A powdery La ₂ Si ₂ O ₇ sample (about 0.54 g) was uniaxially pressed to produce a pellet-shaped green compact having a diameter of about 12 mm and a height of about 2 mm. Further, a powdery La ₂ SiO ₅ sample (about 0.16 g) was uniaxially pressed to produce a pellet-shaped green compact having a diameter of about 12 mm and a height of about 0.5 mm. A plurality of diffusion pairs in which these two green compacts were superimposed were produced, heated in an electric furnace at 1600 ° C for 100 hours, and then cooled to room temperature with the furnace turned off for about 3 hours. .

When the surface of the above-mentioned heat-treated diffusion pair sample was examined by micro-Raman spectroscopy, it was confirmed that La ₂ SiO ₅ had completely disappeared and fine apatite-type lanthanum silicate crystals were exposed on the surface. It was.

  For the purpose of investigating the crystallographic orientation of the apatite-type lanthanum silicate polycrystal formed on the surface of the diffusion pair, the diffraction X of this polycrystal was analyzed in the same manner as described in Example 1. The line profile intensity was measured (FIG. 6). In the X-ray powder diffraction pattern, reflections with diffraction plane indices of 002, 004, and 006 were remarkably observed. Therefore, the apatite-type lanthanum silicate polycrystal exposed on the surface of the diffusion pair was perpendicular to the surface. It was confirmed that the c-axis was oriented along the direction. The degree of orientation of this polycrystal is 93% when calculated from the Lotgering equation in the same manner as in Example 1, which is an extremely high degree of orientation.

(Example 3)
In this example, lanthanum silicate having an apatite type crystal structure obtained by a diffusion pair using a green compact having a chemical formula represented by La ₂ SiO ₅ and a green compact having a chemical formula represented by SiO ₂ . A method for producing c-axis oriented ceramic will be described.

A powdery La ₂ SiO ₅ sample was synthesized by the same method as described in Example 1. This powder sample (about 0.63 g) was uniaxially pressed to produce a pellet-shaped green compact having a diameter of about 12 mm and a height of about 2 mm. Further, a powdered silicon oxide (SiO ₂ ) reagent (about 0.27 g) was uniaxially pressed to prepare a pellet-shaped green compact having a diameter of about 12 mm and a height of about 2 mm. A plurality of diffusion pairs were produced by superimposing these two green compacts, and these were heated in an electric furnace at 1600 ° C for 25 hours, and then the furnace was turned off and cooled to room temperature over about 3 hours. . A sample similar to the diffusion pair described in Example 1 was obtained, but during the process of cooling to room temperature, the unreacted SiO ₂ portion was peeled off and missing. When the surface exposed by peeling off the unreacted SiO ₂ portion was examined by microscopic Raman spectroscopy, it was confirmed that the fine apatite-type lanthanum silicate polycrystal was covering the surface.

For the purpose of investigating the crystallographic orientation of the above apatite-type lanthanum silicate polycrystal, the intensity of the diffracted X-ray profile in the 2θ range from 10.0 ° to 90.0 ° was determined in the same manner as described in Example 1. Was measured (FIG. 7). In the X-ray powder diffraction pattern, reflections with diffraction surface indices of 002, 004, and 006 are remarkably observed, so this apatite-type lanthanum silicate polycrystal is exposed by peeling off the unreacted SiO ₂ portion. It was confirmed that the c-axis was oriented along the direction perpendicular to. The degree of orientation of this polycrystal is 53% when calculated from the Lotgering equation, which is an extremely high degree of orientation.

One of the heat treated diffusion pair samples was processed into a polished piece having a polished surface perpendicular to the original bonded interface in the same manner as described in Example 1. When the polished surface was observed with a reflection microscope, a strip-shaped reaction product having a thickness of about 290 μm was observed on both sides of the original bonding interface (FIG. 8). This reaction product is formed on both sides of the original bonding interface, the thickness of the strip-like product on the La ₂ SiO ₅ side is about 240 μm, and the strip-like product on the side where SiO ₂ was present Is about 50 μm thick. When this reaction product was identified using micro-Raman spectroscopy, it was a lanthanum silicate having an apatite-type crystal structure on both sides of the bonding interface, so (14 + 3x) La ₂ SiO ₅ + (4-3x) SiO ₂ → 3La _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} (where x is a number in the range of −0.10 ≦ x ≦ 0.33) occurs near the original junction interface, and La ₂ SiO ₅ It is considered that apatite-type lanthanum silicate was formed from SiO ₂ and SiO ₂ .

The polished piece was processed into a thin piece by the same method as described in Example 1. When a microstructure was observed with an orthogonal polar using a polarizing microscope (FIG. 9), a columnar crystal having a size of about 240 μm in height and about 45 μm in width was found at the interface on the La ₂ SiO ₅ side of the original bonding interface. It is observed that the crystal grows vertically and aggregates, and on the SiO ₂ side of the original bonding interface, a columnar crystal with a size of about 50 μm height × about 45 μm width grows perpendicularly to the interface The state of gathering was observed. When the state of quenching was observed with an orthogonal polar (FIG. 10), it was confirmed that the entire columnar crystal of apatite-type lanthanum silicate was directly quenched. Therefore, it was confirmed that the apatite-type lanthanum silicate polycrystal formed in the vicinity of the original bonding interface of the diffusion pair almost matches the c-axis direction of the individual crystal grains.

Example 4
In this example, it has an apatite type crystal structure obtained by diffusion pair using a green compact whose chemical formula is represented by La ₂ Si ₂ O ₇ and a green compact whose chemical formula is represented by La ₂ O _3. A method for producing c-axis oriented ceramics of lanthanum silicate will be described.

A powdery La ₂ Si ₂ O ₇ sample was synthesized by the same method as described in Example 1. This powder sample (about 0.54 g) was uniaxially pressed to produce a pelletized green compact having a diameter of about 12 mm and a height of about 2 mm. Further, a powdery lanthanum oxide (La ₂ O ₃ ) reagent (about 0.75 g) was uniaxially pressed to produce a pellet-shaped green compact having a diameter of about 12 mm and a height of about 2 mm. A plurality of diffusion pairs in which these two green compacts were superimposed were prepared, heated in an electric furnace at 1600 ° C for 25 hours, and then cooled to room temperature with the furnace turned off for about 3 hours. . A sample similar to the diffusion pair described in Example 1 was obtained, but the unreacted La ₂ O ₃ portion reacted with moisture in the air and peeled off. When the surface exposed by peeling off the unreacted La ₂ O ₃ portion was examined by micro-Raman spectroscopy, it was confirmed that the surface was covered with fine apatite-type lanthanum silicate crystals.

For the purpose of investigating the crystallographic orientation of the above apatite-type lanthanum silicate polycrystal, the intensity of the diffracted X-ray profile in the 2θ range from 10.0 ° to 90.0 ° was determined in the same manner as described in Example 1. Was measured (FIG. 11). In the X-ray powder diffraction pattern, reflections with diffraction plane indices of 002, 004, and 006 are remarkably observed, so this apatite-type lanthanum silicate polycrystal is exposed by peeling off the unreacted La ₂ O ₃ portion. It was confirmed that the c-axis was oriented along a direction perpendicular to the surface. The degree of orientation of this polycrystal is 49% when calculated from the Lotgering equation, which is an extremely high degree of orientation.

One of the above heat-treated diffusion pair samples is a polishing piece having a polishing surface perpendicular to the surface exposed by peeling off the unreacted La ₂ O ₃ portion in the same manner as described in Example 1. It was processed into. When the polished surface was observed with a reflection microscope, a strip-like reaction product having a thickness of about 230 μm was observed (FIG. 12). Since the original bonding interface could not be confirmed, it is considered that the region including the original bonding interface was peeled off when the unreacted La ₂ O ₃ portion was peeled off. When this reaction product was identified using microscopic Raman spectroscopy, it was a lanthanum silicate having an apatite-type crystal structure, so (5 + 3x) La ₂ O ₃ + 9La ₂ Si ₂ O ₇ → _{3La 9.33+} A reaction of _2x (SiO ₄ ) ₆ O _{2 + 3x} (where x is a number in the range of −0.10 ≦ x ≦ 0.33) occurs in the vicinity of the original junction interface, and La ₂ O ₃ and La ₂ Si ₂ O _It is thought that apatite-type lanthanum silicate was produced from ₇ .
The above-mentioned polishing piece was processed into a thin piece by the same method as described in Example 1. When a microstructure was observed with an orthogonal polar using a polarizing microscope (FIG. 13), a columnar crystal having a height of about 230 μm and a width of about 45 μm was found on the La ₂ Si ₂ O ₇ side of the original bonding interface. It was observed that the crystals grew and assembled perpendicularly to the interface. When the state of quenching was observed with an orthogonal polar (FIG. 14), it was confirmed that the entire columnar crystal of the apatite-type lanthanum silicate was directly quenched. Therefore, it was confirmed that the apatite-type lanthanum silicate polycrystal formed in the vicinity of the original bonding interface of the diffusion pair almost matches the c-axis direction of the individual crystal grains.

(Example 5)
In the present example, similar to Example 1, it is obtained by a diffusion pair using a green compact whose chemical formula is represented by La ₂ SiO ₅ and a green compact whose chemical formula is represented by La ₂ Si ₂ O _7. A method for producing a highly oriented ceramic of apatite type lanthanum silicate will be described. In this example, a single layer of La ₂ SiO ₅ compact (0.80 mm thickness) was sandwiched between two layers of La ₂ Si ₂ O ₇ compact and a diffusion layer consisting of three layers was used. After this diffusion pair is heat-treated, the intermediate La ₂ SiO ₅ layer disappears completely, and apatite-type lanthanum silicate is generated between the La ₂ Si ₂ O ₇ sintered body layers.

A powdery La ₂ SiO ₅ sample and a powdery La ₂ Si ₂ O ₇ sample were synthesized in the same manner as described in Example 1, respectively. A powdery La ₂ Si ₂ O ₇ sample (about 0.90 g) was uniaxially pressed to produce two pellets of green compact with a diameter of about 20 mm and a height of about 1 mm. Further, a powdery La ₂ SiO ₅ sample (about 1.30 g) was uniaxially pressed to prepare a pellet-shaped green compact having a diameter of about 20 mm and a height of about 0.80 mm. A plurality of diffusion pairs were produced by laminating these three green compacts in the order of La ₂ Si ₂ O ₇ / La ₂ SiO ₅ / La ₂ Si ₂ O ₇ , and these were formed in an electric furnace at 1600 ° C. for 200 After heating for an hour, the furnace was turned off and cooled to room temperature over about 3 hours.

One of the heat-treated diffusion pair samples was cut out with a diamond cutter in a direction perpendicular to the original bonding surface, and the cross section was mirror-polished with a diamond paste to produce a polished piece. When the polished surface was observed with a reflection microscope, the original La ₂ SiO ₅ layer disappeared completely, and a band-shaped reaction product was observed between the _two La ₂ Si ₂ O ₇ layers with a thickness of about 1500 μm. (FIG. 15). When this reaction product was identified using microscopic Raman spectroscopy, it was found to be (10 + 6x) La ₂ SiO ₅ + (4-3x) La ₂ Si ₂ O because it is a lanthanum silicate having an apatite-type crystal structure. ₇ → 3La _{9.33 + 2x} (SiO ₄ ) ₆ O _{2 + 3x} (where x is a number in the range of −0.10 ≦ x ≦ 0.33)
It is considered that the reaction represented by the following occurs in the vicinity of the original bonding interface, and all La ₂ SiO ₅ reacted with La ₂ Si ₂ O ₇ to form apatite-type lanthanum silicate.

The polishing surface of the polishing piece was attached to a slide glass using an epoxy resin, and an excess portion was cut off using a diamond cutter, and then polished with emery paper and diamond paste to produce a thin piece. When a microstructure was observed with an orthogonal polar using a polarizing microscope (FIG. 16), an apatite-type lanthanum silicate having a height of about 400 μm and a width of about 45 μm was formed on the La ₂ SiO ₅ side of the original bonding interface. It is observed that the columnar crystals grow and gather perpendicular to the interface, and the La ₂ Si ₂ O ₇ side of the original junction interface has a height of about 350 μm × width of about 45 μm. It was observed that the columnar crystals grew and assembled perpendicularly to the interface.
These apatite-type lanthanum silicate columnar crystals reached a total thickness of about 1500 μm.

  When an aggregate of columnar crystals of apatite lanthanum silicate was observed in an orthogonal polar state (FIG. 17), it was confirmed that the entire columnar crystals of apatite lanthanum silicate were directly quenched. Since the crystal structure of apatite-type lanthanum silicate belongs to the hexagonal system, it is optically uniaxial, and its optical axis coincides with the crystallographic c-axis. Therefore, it is expected that the apatite-type lanthanum silicate polycrystal formed in the vicinity of the original bonding interface of the diffusion pair substantially matches the c-axis direction of the individual crystal grains. Therefore, the crystallographic orientation of the apatite-type lanthanum silicate polycrystal was investigated by X-ray diffraction.

One of the heat-treated diffusion pair samples was cut out with a diamond cutter in a direction parallel to the original bonding interface so that the apatite-type lanthanum silicate polycrystal was exposed, and the cross section was mirror-polished using diamond paste. Thus, a polished piece was produced. In order to investigate the crystallographic orientation of the apatite-type lanthanum silicate polycrystal exposed on the polished surface, a high-resolution X-ray powder diffractometer using CuKα ₁ line (45kV × 40mA) as incident light was used. The profile intensity of the diffracted X-rays in the 2θ range from ° to 90.0 ° was measured (FIG. 18). In the X-ray powder diffraction pattern, reflections with diffraction plane indices of 002, 004, and 006 are remarkably observed. Therefore, the apatite-type lanthanum silicate polycrystal has a c-axis along the direction perpendicular to the original bonding interface. Were confirmed to be oriented. The degree of orientation of this polycrystal is 91% when calculated from the Lotgering equation, which is an extremely high degree of orientation.

(Example 6)
In this example, the c-axis of lanthanum silicate having an apatite type crystal structure obtained by a diffusion pair using a sintered body having a chemical formula represented by La ₂ SiO ₅ and a thin film having a chemical formula represented by SiO ₂ A method for manufacturing oriented ceramics will be described.

In this example, a powdery La ₂ SiO ₅ sample was synthesized by the same method as described in Example 1. This powder sample (about 2.50 g) is uniaxially pressed to produce a number of pellet-shaped green compacts with a diameter of about 20 mm and a height of about 2 mm, and these are heated in an electric furnace at 1600 ° C for 2 hours. Thereafter, it was taken out from the electric furnace and cooled.

In addition, the ratio of silicon oxide (SiO ₂ ) gel that produces ethyl silicate (Si (OC ₂ H ₅ ) ₄ ), ethanol (C ₂ H ₅ OH), water (H ₂ O) and hydrochloric acid (HCl) as starting materials To prepare a raw material solution. This raw material solution was stirred for 2 hours while warming at about 60 ° C.

The obtained gel was applied to a La ₂ SiO ₅ sintered body by a dip coating method. This was heated in an electric furnace to 500 ° C. at a heating rate of 50 ° C. per hour, held for 1 hour, cooled at a cooling rate of 50 ° C. per hour to form a La ₂ SiO ₅ sintered body with silicon oxide A (SiO ₂ ) thin film was formed. These were heated in an electric furnace at 1600 ° C. for 25 hours, and then the furnace was turned off and cooled to room temperature over about 3 hours.

When the surface of the above-mentioned heat-treated diffusion pair sample was examined by micro-Raman spectroscopy, it was confirmed that SiO ₂ was completely disappeared and fine apatite-type lanthanum silicate crystals were exposed on the surface.

  For the purpose of investigating the crystallographic orientation of the apatite-type lanthanum silicate polycrystal formed on the surface of the diffusion pair, the diffraction X of this polycrystal was analyzed in the same manner as described in Example 1. The line profile intensity was measured (FIG. 19). In the X-ray powder diffraction pattern, reflections with diffraction plane indices of 002, 004, and 006 were remarkably observed. Therefore, the apatite-type lanthanum silicate polycrystal exposed on the surface of the diffusion pair was perpendicular to the surface. It was confirmed that the c-axis was oriented along the direction. The degree of orientation of this polycrystal is 28% when calculated from the Lotgering equation, which is a high degree of orientation.

Claims (14)

A lanthanum silicate having an apatite-type crystal structure is formed in the vicinity of the bonding interface where the first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other. A crystallographically-oriented ceramic, characterized in that the produced lanthanum silicate crystal has a c-axis oriented along a direction perpendicular to the original bonding interface. A first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other to have a bonding interface, and this is heated at a predetermined temperature, A method for producing a crystallographically-oriented ceramic, wherein the predetermined temperature is a temperature at which element diffusion occurs between the first layer and the second layer, and a lanthanum silicate having an apatite-type crystal structure is generated. A method for producing a crystallographically-oriented ceramic, wherein the produced lanthanum silicate crystals have a c-axis oriented along a vertical direction with respect to the original bonding interface. A lanthanum silicate having an apatite-type crystal structure is formed in the vicinity of the bonding interface where the first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of SiO ₂ are brought into contact with each other. A crystallographically-oriented ceramic, wherein the lanthanum silicate crystals have a c-axis oriented along a direction perpendicular to the original bonding interface. The first layer mainly composed of La ₂ SiO ₅ and the second layer mainly composed of SiO ₂ are brought into contact with each other to form a bonding interface, and this is heated at a predetermined temperature, whereby the crystal-oriented ceramic is obtained. In the manufacturing method, the predetermined temperature is a temperature at which element diffusion occurs between the first layer and the second layer, and a lanthanum silicate having an apatite-type crystal structure is generated. A method for producing a crystallographically-oriented ceramic, characterized in that the lanthanum silicate crystals formed have a c-axis oriented along a direction perpendicular to the original bonding interface. A lanthanum silicate having an apatite-type crystal structure is formed in the vicinity of the bonding interface where the first layer mainly composed of La ₂ O ₃ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other. A crystallographically-oriented ceramic, characterized in that the produced lanthanum silicate crystal has a c-axis oriented along a direction perpendicular to the original bonding interface. The first layer mainly composed of La ₂ O ₃ and the second layer mainly composed of La ₂ Si ₂ O ₇ are brought into contact with each other to have a bonding interface, and this is heated at a predetermined temperature, A method for producing a crystallographically-oriented ceramic, wherein the predetermined temperature is a temperature at which element diffusion occurs between the first layer and the second layer, and a lanthanum silicate having an apatite-type crystal structure is generated. A method for producing a crystallographically-oriented ceramic, wherein the produced lanthanum silicate crystals have a c-axis oriented along a vertical direction with respect to the original bonding interface. A lanthanum silicate having an apatite-type crystal structure is formed in the vicinity of the bonding interface in which the first layer mainly composed of SiO ₂ and the second layer mainly composed of La ₂ SiO ₅ are brought into contact with each other. A crystallographically-oriented ceramic, wherein the lanthanum silicate crystals have a c-axis oriented along a direction perpendicular to the original bonding interface. The first layer mainly composed of SiO ₂ and the second layer mainly composed of La ₂ SiO ₅ are brought into contact with each other to form a bonding interface, and this is heated at a predetermined temperature, whereby the crystal-oriented ceramic is obtained. In the manufacturing method, the predetermined temperature is a temperature at which element diffusion occurs between the first layer and the second layer, and a lanthanum silicate having an apatite-type crystal structure is generated. A method for producing a crystallographically-oriented ceramic, characterized in that the lanthanum silicate crystals formed have a c-axis oriented along a direction perpendicular to the original bonding interface. A compound formed in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other, having a crystal structure perpendicularly oriented to the original bonding interface, and the compound is an apatite-type crystal A lanthanum silicate having a structure having a crystal structure in which a c-axis is oriented along a vertical direction with respect to an original bonding interface, and the plurality of substances are mainly composed of La ₂ SiO ₅ . first layer and the second layer and the including crystal oriented ceramics composed mainly of La ₂ Si ₂ O _7. A compound formed in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other, having a crystal structure perpendicularly oriented to the original bonding interface, and the compound is an apatite-type crystal A lanthanum silicate having a structure having a crystal structure in which a c-axis is oriented along a vertical direction with respect to an original bonding interface, and the plurality of substances are mainly composed of La ₂ SiO ₅ . a first layer, second layer and the including crystal oriented ceramics composed mainly of SiO _2. A compound formed in the vicinity of a bonding interface in which a plurality of substances having different average chemical compositions are in contact with each other, having a crystal structure perpendicularly oriented to the original bonding interface, and the compound is an apatite-type crystal A lanthanum silicate having a structure having a crystal structure in which a c-axis is oriented along a vertical direction with respect to an original bonding interface, and the plurality of substances are mainly composed of La ₂ O ₃ . first layer and the second layer and the including crystal oriented ceramics composed mainly of La ₂ Si ₂ O _7. A step of bringing a plurality of substances having different average chemical compositions into contact with each other to have a bonding interface; and
Heating the plurality of substances configured as described above at a temperature at which element diffusion occurs between the plurality of substances, and generating crystal-oriented ceramics in the vicinity of the bonding interface,
The crystallographically-oriented ceramic is composed of a compound having a crystal structure perpendicularly oriented with respect to the original bonding interface, and the compound is a lanthanum silicate having an apatite type crystal structure, The c-axis has a crystal structure oriented along the vertical direction, and the plurality of materials includes a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of La ₂ Si ₂ O ₇ . the method of manufacturing the layers and der Ru crystal oriented ceramics. A step of bringing a plurality of substances having different average chemical compositions into contact with each other to have a bonding interface; and
Heating the plurality of substances configured as described above at a temperature at which element diffusion occurs between the plurality of substances, and generating crystal-oriented ceramics in the vicinity of the bonding interface,
The crystallographically-oriented ceramic is composed of a compound having a crystal structure perpendicularly oriented with respect to the original bonding interface, and the compound is a lanthanum silicate having an apatite type crystal structure, The c-axis has a crystal structure oriented along the vertical direction, and the plurality of substances are a first layer mainly composed of La ₂ SiO ₅ and a second layer mainly composed of SiO _2. method of manufacturing a crystal-oriented ceramic Ru Oh. A step of bringing a plurality of substances having different average chemical compositions into contact with each other to have a bonding interface; and
Heating the plurality of substances configured as described above at a temperature at which element diffusion occurs between the plurality of substances, and generating crystal-oriented ceramics in the vicinity of the bonding interface,
The crystallographically-oriented ceramic is composed of a compound having a crystal structure perpendicularly oriented with respect to the original bonding interface, and the compound is a lanthanum silicate having an apatite type crystal structure, The c-axis has a crystal structure oriented along the vertical direction, and the plurality of substances are a first layer mainly composed of La ₂ O ₃ and a second layer mainly composed of La ₂ Si ₂ O ₇ . the method of manufacturing the layers and der Ru crystal oriented ceramics.