JP5376500B2 - Oxygen ion conductive ceramic membrane material and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic film material which is composed of a perovskite type oxygen-ion conductive body and can further improve oxygen-ion conduction. <P>SOLUTION: The method of manufacturing oxygen-ion conductive ceramic film material comprises: a process of preparing a substrate oriented in a predetermined crystalline face; a process of preparing a raw material for constituting a perovskite type ceramic film represented by a general formula: A<SB>1-x</SB>Ae<SB>x</SB>BO<SB>3-&delta;</SB>; and a process of forming the ceramic film on the crystalline face of the substrate while performing crystal alignment according to a vapor deposition method. Therein, A presents at least one kind element selected from Ln (lanthanoid), Ae presents one or more kinds of elements selected from a group consisting of Sr, Ba and Ca, B presents one or more kinds of metal elements capable of constituting a perovskite type structure, 0&le;x&le;1 holds and &delta; satisfies charge neutral condition. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a ceramic membrane material including a ceramic membrane excellent in oxygen ion conductivity. Specifically, the present invention relates to a ceramic film material provided with a crystallographically oriented ceramic film oriented in a specific crystal orientation on a substrate having a specific crystal plane, and a method for manufacturing the same.

As an oxygen ion conductor having oxygen ions (typically also called O ²⁻ ; oxide ions), oxide ceramics having a so-called perovskite structure are known. Since the perovskite oxide is an oxygen ion conductor, it is an oxygen ion-electron mixed conductor (hereinafter, simply referred to as “mixed conductor”) having electron conductivity. A dense ceramic material, typically a ceramic material (ceramic film) formed in a film shape, for example, selectively transmits oxygen from an oxygen-containing gas (such as air) supplied to one surface to the other surface. It can be suitably used as an oxygen separation membrane material.
An oxygen separation membrane composed of a perovskite oxide can be formed on a substrate (typically a membrane support having a porous structure) and used as an oxygen separation membrane element. The oxygen separation membrane element having such a structure oxidizes hydrocarbons (such as methane gas) supplied to the other surface by oxygen ions supplied from one surface to the other surface, thereby producing a synthetic liquid fuel (such as methanol). Can be suitably used in the GTL (Gas To Liquid) technology for manufacturing the fuel cell, or in the fuel cell field (see Patent Documents 1 to 5).

  As a method for forming a ceramic film comprising a perovskite oxide on a substrate, typically, a dip coating method in which the substrate is immersed in a slurry prepared using the constituent material of the ceramic film, or sheet molding, Examples include press molding or extrusion molding. The ceramic film obtained by such a method has a randomly oriented (non-oriented) polycrystalline structure in which a plurality of crystal orientation planes are mixed. However, in a crystal structure with non-orientation or low orientation, the conduction path of ions and electrons becomes long, so that the conduction of ions and electrons can be inefficient. Therefore, in the ceramic film having such a structure, the high mixed conductivity that the perovskite oxide can have is hardly exhibited to the maximum extent.

Japanese Patent No. 2813596 Japanese Patent Laid-Open No. 8-173776 Japanese Patent No. 3456436 JP 2001-93325 A JP 2002-12472 A JP-A-10-279355 JP 2000-351665 A JP 2005-97041 A JP 2006-280001 A JP 2006-137657 A JP-A-9-293520 JP 2005-171269 A

Here, by aligning a specific crystal plane or crystal axis in a polycrystalline ceramic made of a perovskite oxide, characteristics dependent on the specific crystal plane or crystal axis (crystal orientation dependency such as ion conductivity and piezoelectricity). For example, Patent Documents 6 to 10 have proposed various techniques for improving the properties and the like or crystal orientation ceramics having such characteristics. However, the application object of such a technique is a powder or a bulk body, and is not suitable for a ceramic film having a film thickness of, for example, several hundred nm to several μm.
Patent Documents 11 and 12 describe a method of forming an ion (or electron) conductive ceramic film by employing a pulse laser ablation deposition method. However, since the crystal orientation of the ceramic film obtained by this technique is not specified, there is a high possibility that it is not oriented in a crystal orientation that can greatly improve ionic conductivity, and such ionic conductivity is sufficiently exhibited. Not.

  Accordingly, the present invention was created to solve the above-described problems, and an object thereof is to provide a ceramic membrane material that is composed of a perovskite-type oxygen ion conductor and that can further improve oxygen ion conductivity. And

In order to achieve the above object, the present invention provides a method for producing an oxygen ion conductive ceramic membrane material comprising a substrate and a ceramic membrane made of an oxygen ion conductor formed on the substrate. This method is characterized by including the following steps (I) to (III). That is, (I) a step of preparing the substrate is included. Here, the substrate is made of a metal material or a ceramic material oriented in a predetermined crystal plane. (II) The process of preparing the raw material for comprising the said ceramic membrane is included. Here, the ceramic membrane has the general formula:
A1-xAexBO _3-δ (1)
(However, A is at least one element selected from Ln (lanthanoid), and Ae is one or two selected from the group consisting of Sr (strontium), Ba (barium) and Ca (calcium). a kind or more elements, B is two or more metal elements that give constitute a perovskite structure including at least Fe and Ti, a 0 ≦ x ≦ 1, δ is the charge neutrality condition is satisfied (The value is determined as follows.)
It is characterized by comprising a perovskite type oxygen ion conductor represented by And (III) a step of forming the ceramic film on the crystal plane of the substrate in a crystal orientation state so that the degree of orientation is 20% or more by the vapor deposition method. Here, the vapor deposition method is one of a pulsed laser ablation deposition method and an ion beam vapor deposition method.
In the oxygen ion conductive ceramic film material obtained by such a method, since the ceramic film is formed on the substrate in a crystal orientation state, the oxygen ion conduction path is shortened as compared with the non-oriented film. Efficiency of conduction can be achieved. As a result, in the oxygen ion conductive ceramic membrane material obtained by the method according to the present invention, oxygen ion conduction is higher than that of a ceramic membrane material provided with a non-oriented ceramic membrane obtained by a conventional film formation method (eg, dip coating). The performance (performance) can be improved. In the present specification, the term “film” is not limited to a specific thickness, and a film-like or layer-like portion functioning as an “oxygen ion conductor” in the oxygen ion conductive ceramic film material disclosed herein is used. Say. In addition, the “substrate” in the present specification is not limited to a specific thickness or shape, and refers to a portion that serves as a base for forming the ceramic film in the oxygen ion conductive ceramic film material.

  Moreover, as a method used when forming the said ceramic film | membrane on the said board | substrate, a physical vapor deposition method (PVD) or a chemical vapor deposition method (CVD) can be employ | adopted preferably. Preferable examples of the physical vapor deposition method include a pulse laser ablation deposition method (hereinafter referred to as “PLD method”), an ion beam deposition method, and the like. By using this method, a ceramic film having a crystal orientation can be preferably formed on the substrate.

Further, the oxygen ion conductor is characterized in that it comprises at least Fe (iron) and Ti as metal elements capable of constituting a perovskite structure.
According to this aspect, Fe is incorporated into a part of the perovskite crystal structure (part of the B site) in the oxygen ion conductor constituting the ceramic film. This can further improve the oxygen ion conductivity of the oxygen ion conductor (that is, the ceramic film).

In a preferred embodiment of the manufacturing method disclosed herein, the substrate is a nickel substrate, and its {100} plane (typically having a face-centered cubic structure) is parallel to the rolling surface <001 > A substrate having a structure in which the axis is parallel to the rolling direction is used. The ceramic film can be formed on the {100} face of such a substrate.
Alternatively, in another preferable aspect of the production method disclosed herein, the substrate is a substrate made of strontium titanate and oriented in the (100) plane of the perovskite structure. It is characterized by. The ceramic film can be formed on the (100) plane of such a substrate.
According to this aspect, by using any of the above substrates, the ceramic film can be formed (grown) in a state in which the ceramic film is oriented in a crystal orientation that can improve oxygen ion conductivity.
Hereinafter, when describing the crystal plane (lattice plane) and orientation (direction) in the crystal structure of the substrate and the ceramic film, the plane index and orientation index of the Miller index are used. The crystal plane is represented by (hkl) (where h, k, and l are integers). In the cubic structure, the six planes that are equivalent from the viewpoint of space group symmetry are collectively referred to as {hkl}. Similarly to the plane index, the orientation index is represented by [uvw] (where u, v, and w are integers), and the six directions equivalent in the cubic system are collectively referred to as <uvw>.

  By the method according to the present invention, it is possible to produce a ceramic film material that has the crystallographically oriented ceramic film as described above and has improved oxygen ion conductivity. That is, this invention provides the preferable oxygen ion conductive ceramic membrane material which has high oxygen ion conductivity as another side surface.

In a preferred embodiment of the oxygen ion conductive ceramic membrane material disclosed herein, the substrate is made of nickel, and has a structure in which the {100} plane is parallel to the rolling surface and the <001> axis is parallel to the rolling direction. A nickel substrate provided; and a ceramic film made of an oxygen ion conductor formed on a {100} plane of the substrate. The ceramic film has a general formula: A _1-x Ae _x BO _3-δ (where A is at least one element selected from Ln (lanthanoid), and Ae is Sr, Ba and Ca). is one or more elements selected from the group consisting of, B is two or more metal elements that give constitute a perovskite structure including at least Fe and Ti, 0 ≦ x ≦ 1 And δ is a value determined so as to satisfy the charge neutrality condition.) And is composed of a perovskite type oxygen ion conductor represented by (a00) plane and / or (aa0) plane (where a is 1). It is an integer of the above), and is characterized by being oriented at an orientation degree of 20% or more.
In the oxygen ion conductive ceramic membrane material having such a configuration, a ceramic membrane in a state of being selectively oriented on the (a00) plane or the (aa0) plane is formed, and has higher oxygen ion conductivity. Therefore, according to the oxygen ion conductive ceramic membrane material having such a configuration, good oxygen ion conductivity can be exhibited.

In another preferred embodiment of the oxygen ion conductive ceramic membrane material disclosed herein, a substrate made of strontium titanate and oriented in the (100) plane of a perovskite structure, And a ceramic film made of an oxygen ion conductor formed on the (100) plane. The ceramic film has a general formula: A _1-x Ae _x BO _3-δ (where A is at least one element selected from Ln (lanthanoid), and Ae is Sr, Ba and Ca). is one or more elements selected from the group consisting of, B is two or more metal elements that give constitute a perovskite structure including at least Fe and Ti, 0 ≦ x ≦ 1 And δ is a value determined so as to satisfy the charge neutrality condition.) (A00) plane (where a is an integer of 1 or more). It is characterized by having an orientation degree of 20% or more.
In the oxygen ion conductive ceramic membrane material having such a configuration, a ceramic membrane in a state of being selectively oriented on the (a00) plane is formed, and has higher oxygen ion conductivity. Therefore, according to the oxygen ion conductive ceramic membrane material having such a configuration, good oxygen ion conductivity can be exhibited.

  An oxygen ion conductive ceramic membrane material having such a configuration can be used as an oxygen separation membrane element by including a porous support that supports the membrane material. That is, the oxygen separation membrane element includes the oxygen ion conductive ceramic membrane material disclosed herein and a porous support formed on the ceramic membrane surface on the side where the substrate of the membrane material is not formed. The oxygen separation membrane element is an oxygen separation membrane element with further improved oxygen ion conductivity.

  Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than the matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, a raw material powder mixing method or molding method at the time of target production, or a molding body firing method) Therefore, it can be grasped as a design matter of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

A manufacturing method provided by the present invention is a method for manufacturing an oxygen ion conductive ceramic film material including a substrate and a ceramic film made of an oxygen ion conductor formed on the substrate, wherein the crystal surface has a predetermined crystal plane. This is a manufacturing method characterized by forming a ceramic film in a crystal-oriented state on a substrate made of a metal material or ceramic material oriented in the above manner. As described above, the manufacturing method includes the step of preparing the substrate, the step of preparing a raw material for forming the ceramic film, and the ceramic on the crystal plane of the substrate by a predetermined vapor deposition method. Forming the film in a crystal oriented state.
The ceramic film is a perovskite-type oxygen ion conductor represented by the general formula (1): A _1-x Ae _x BO _3-δ (hereinafter simply referred to as “general formula (1)”) with crystal orientation. It is a film characterized by comprising. Here, A is at least one element selected from Ln (lanthanoid) (for example, La (lanthanum)), and Ae is one or two selected from the group consisting of Sr, Ba, and Ca. These elements are the above elements (for example, Sr), and the above B is one or more metal elements (for example, Ti (titanium) and / or Fe) that can form a perovskite structure. Further, 0 <x <1, and δ is a value determined to satisfy the charge neutrality condition.
Further, the oxygen ion conductive ceramic membrane material provided by the present invention has a ceramic film oriented in a predetermined crystal plane, so that it is compared with a ceramic membrane formed by a conventional film forming technique such as dip coating. It is a membrane material characterized by having further improved oxygen ion conduction performance.

The substrate suitably used in the technology disclosed herein is preferably a substrate made of a metal or ceramic solid material, and in a crystal (typically a polycrystal) constituting the solid material, A substrate made of a solid material in which predetermined (specific) crystal planes in the crystal structure are arranged with a certain directionality (that is, oriented in the specific crystal plane) is preferable. More preferably, the substrate is such that the ceramic film formed on the substrate is oriented in a crystal orientation capable of improving oxygen ion conductivity. As such a substrate, for example, a nickel substrate typically having a face-centered cubic structure, in which the {100} plane is parallel to the rolling surface and the <001> axis is parallel to the rolling direction. The board | substrate provided with is mentioned. Such a substrate is preferable because it can be easily manufactured by heat treatment. When this substrate is used, the ceramic film can be preferably formed on the {100} plane. Another preferred example is a substrate made of strontium titanate having a perovskite structure and oriented in the (100) plane. When such a substrate is used, the ceramic film can be preferably formed on the (100) plane. When a substrate such as these is used and a ceramic film is formed on a specific crystal plane (orientation plane) of the substrate, the ceramic film itself can also be oriented to a specific crystal plane.
The thickness of the substrate is preferably 50 μm to 10 mm, more preferably 100 μm to 5 mm, and still more preferably 200 μm to 1 mm.

  The ceramic film formed on the substrate as described above preferably has a perovskite structure that is an oxygen ion conductor. Such a ceramic membrane is not limited to a specific constituent element, but when such a ceramic membrane is applied as an oxygen separation membrane (in an oxygen separation membrane element described later), one side of the oxygen separation membrane (oxygen supply) Side) and the other side (oxygen permeation side) can be continuously permeated from one to the other without using an external electrode or an external circuit for short-circuiting, and the permeation rate of oxygen ions Can be increased, which is preferable. This type of ceramic is typically a perovskite oxide represented by the general formula (1). The number of oxygen atoms in the above general formula (1) varies depending on the type of atom that substitutes a part of the perovskite structure, the substitution ratio, and other conditions, so that it is difficult to display accurately. Therefore, a positive number δ (0 <δ <1) not exceeding 1 is adopted as a value that is determined so as to satisfy the charge neutrality condition, and the number of oxygen atoms is expressed as 3-δ in this specification. . In this field, the number of oxygen atoms may be indicated as 3 for convenience, but it does not represent a different compound.

A in the general formula (1) is an element constituting the A site of the perovskite oxide, and is a combination of at least one element selected from Ln (lanthanoid). La is preferred. Ae is a combination of one or more elements selected from the group consisting of Sr, Ca and Ba. In the general formula (C), x is preferably 0 ≦ x ≦ 1. By selecting two or more elements as A and Ae in the general formula (C) and substituting some atoms of the perovskite structure (that is, substituting part of the part that can be composed of A with Ae) , Lattice defects are introduced into the A site. The lattice defects at the A site contribute to the improvement of oxygen mobility in the crystal structure. The amount of substitution at the A site may be adjusted in consideration of the balance between the amount of lattice defects and the stabilization of the structure.
Further, B in the general formula (1) is an element constituting the B site of the perovskite oxide, and may be one or more metal elements that can constitute a perovskite structure. Examples of such B include Mg (magnesium), Mn (manganese), Ga (gallium), Ti (titanium), Co (cobalt), Ni (nickel), Al (aluminum), Cu (copper), and In (indium). , Sn (tin), Zr (zirconium), V (vanadium), Cr (chromium), Zn (zinc), Ge (germanium), Sc (scandium), and Y (yttrium). Can be mentioned. B preferably includes Fe. More preferably, it may contain Fe and Ti. By containing Fe in the B site, oxygen ion conductivity is improved. Moreover, the strength of the crystal structure is improved by including Ti at the B site. For this reason, the ceramic film disclosed here can achieve both oxygen ion conductivity and film strength at a high level by including Fe and Ti at the B site.
As such a perovskite type oxide, for example, a perovskite type represented by the formula: (La _1-p Sr _p ) (Ti _1-q Fe _q ) O _3-δ (where 0 <p <1, 0 <q <1) A composite oxide (hereinafter also referred to as “LSTF oxide”) is preferable. A specific example is La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ .

A ceramic film made of an oxygen ion conductor having a perovskite structure as described above can be formed on the substrate by using a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method. The PVD method is a method of forming a thin film by vaporizing a solid material, which is a thin film material, using a physical action (heat source) by heat, laser light, an electron beam or the like and depositing it on a substrate. Such PVD methods are roughly classified into an evaporation system and a sputtering system when classified according to the vaporization method of the thin film raw material. The evaporation PVD method is a method in which a thin film raw material is heated and evaporated to condense and solidify on a substrate surface having a temperature lower than the evaporation temperature to form a thin film. A preferred example of such a method is an ion beam deposition method. In the ion beam deposition method, a thin film material is ionized by an ion generator, and the ions are irradiated by irradiating the thin film material ions emitted from an ion gun (an apparatus that accelerates and emits ions generated by the ion generator). Can be deposited on the substrate to form a thin film.
On the other hand, the sputtering PVD method evaporates by heating the thin film material, and condenses and solidifies on the substrate surface at a temperature lower than the evaporation temperature to form a thin film, and targets high energy atoms and molecules. This is a method of depositing on the substrate surface by evaporating and sputtering (sputtering). A preferred example of such a method is a pulsed laser ablation deposition (PLD) method. The PLD method is sometimes called a pulse laser ablation method or a pulse laser deposition method. In the PLD method, a target is irradiated with a pulsed laser to sequentially generate vapor (typically molecules, atoms, ions, nano- or micron-sized particles (clusters) generated from the target by pulsed laser irradiation). And the vapor is deposited on a substrate maintained at a constant temperature to form a thin film containing a target material component.
The CVD method is a method of making a thin film using a chemical reaction using a compound gas containing thin film constituent atoms as a raw material, and includes thermal CVD, plasma CVD, or photo-CVD.

Hereinafter, as an example of the vapor deposition method, a case where the ceramic film having the crystal orientation is formed by using the PLD method will be described.
As a target that can be used to form the ceramic film, a ceramic film raw material that can be evaporated by irradiating a pulse laser and that is composed of a ceramic film raw material containing the constituent elements of the ceramic film is preferably used. Can do. In addition, such a target is obtained by mixing and firing an inorganic material (typically, an oxide or carbonate of the constituent element) containing a constituent element of the ceramic film at an appropriate blending ratio. A ligation can be preferably used. The blending ratio of each inorganic material is determined so that the ceramic film has a target composition ratio when the target vaporized by laser irradiation is deposited on the substrate. For example, when a thin film made of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ, which is one of LSTF oxides, is formed on the substrate as the ceramic film, lanthanum oxide ( Each raw material powder of La ₂ O ₃ ) powder, strontium carbonate (SrCO ₃ ) powder, titanium dioxide (TiO ₂ ) powder, and ferric trioxide (Fe ₂ O ₃ ) was added in an amount of 1 mol of the entire LSTF oxide. As a mixture, the mixing ratio was determined so that La contained in the constituent element was 0.6 mol, Sr was 0.4 mol, Ti was 0.1 mol, and Fe was 0.9 mol. Forming a target (ceramic body) having a desired shape by molding by a simple method (for example, press molding or extrusion molding) and firing in an oxidizing atmosphere (for example, in the air) or an inert gas atmosphere That. In such a case, the firing temperature is typically 1000 ° C. to 1800 ° C. (preferably 1200 ° C. to 1600 ° C.).

  The size of the target is not particularly limited, but in order to be suitably used for a general vapor deposition apparatus (PLD apparatus), the diameter is about 1 mm to 1000 mm, particularly 100 mm to 500 mm, and the thickness is 0.5 mm. It is preferably a disc shape of about 10 mm, particularly about 2 mm to 5 mm.

  Further, the surface roughness (Ra value) of the target is preferably 100 μm or less, more preferably about 1 nm to 50 μm, more preferably about 1 nm to 10 μm, and particularly preferably about 1 nm to 5 μm. be able to. Moreover, the maximum value (Rmax value) of the surface roughness is preferably 100 μm or less, more preferably 1 nm to 50 μm, and still more preferably 1 nm to 10 μm.

  The pulse laser that can be used for forming the ceramic film is a laser having a power capable of generating a vapor (typically a microcluster) of a ceramic film material from the target by irradiating the target. Any material having a frequency within the range can be appropriately selected and used according to the application without any particular limitation. For example, a nanosecond pulse laser can be used, and among these, an excimer laser such as a KrF laser, an ArF laser, or a XeCl laser, a YAG laser, or a ruby laser is preferable.

The frequency of the pulse laser is preferably in the range of approximately 500 Hz or less. More preferably, it is 1 Hz-100 Hz, More preferably, it is 1 Hz-80 Hz, Especially preferably, it is 1 Hz-50 Hz.
The irradiation energy (energy density) is not particularly limited, but a range used in a general PLD method is preferable. For ^{example, 100mJ / cm 2 ~2000mJ / cm} 2, preferably ^{500mJ / cm 2 ~1500mJ / cm 2} , more preferably ^{500mJ / cm 2 ~1000mJ / cm 2} , for example, ^{800mJ / cm 2 ± 100mJ / cm} 2. However, higher energy can be used if the device can use higher energy.

The film atmosphere of the ceramic film, about 1 × ¹⁰ -6 Pa to about 1 × ¹⁰ 3 Pa (e.g., 5 × ¹⁰ -7 Torr~1Torr) is preferably within, and more preferably 1 × 10 ^- Low pressure (vacuum) such as ⁴ Pa to 1 × 10 ² Pa, more preferably 1 × 10 ⁻³ Pa to 50 Pa, particularly preferably 2 × 10 ⁻³ Pa to 30 Pa (for example, 0.02 mTorr to 0.2 Torr). ) The atmosphere.
The atmosphere gas at this time is not particularly limited. For example, it may be an oxidizing gas such as oxygen gas or air, or an inert gas such as nitrogen (N ₂ ) gas or argon (Ar) gas. Of these, an inert gas, particularly Ar gas is preferred.

  The irradiation time of the pulse laser can be appropriately selected depending on the desired thickness of the ceramic film, the number of irradiation times of the pulse laser, the frequency, and the like. For example, it is 1 second to 30000 seconds, preferably 10 seconds to 10000 seconds, more preferably 50 seconds to 5000 seconds, and still more preferably 100 seconds to 3000 seconds.

  The temperature of the substrate when depositing the ceramic film component evaporated from the target is not particularly limited as long as the mechanical strength of the substrate can be maintained, but is preferably 1000 ° C. or less, more preferably 500 ° C. to 1000 ° C. More preferably, it is 600 ° C. to 900 ° C., for example, 750 ° C. ± 50 ° C. Moreover, by maintaining such a temperature substantially constant, the ceramic film can be formed while controlling the crystal orientation.

  The thickness of the ceramic film formed by deposition on the substrate is not particularly limited, and various thicknesses can be taken depending on the application. For example, when such a ceramic membrane is used as an oxygen separation membrane, the thickness is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm, and still more preferably 0.3 μm to 2 μm. Within these ranges, the film thickness is thin enough to maintain the denseness of the oxygen separation membrane in the oxygen separation membrane element, so the film thickness does not become the rate limiting rate of oxygen transmission. .

  By using the PLD method under the above conditions, a ceramic film having the following crystal orientation can be obtained on the substrate. In such a ceramic film, all or part of the perovskite type polycrystals constituting the film are arranged so that a specific crystal plane (crystal axis) of the structure is aligned in a specific direction (that is, Oriented on the crystal plane). Typically, this specific crystal plane is oriented so as to be parallel to the surface of the ceramic film. The crystal plane (orientation plane) on which the ceramic film is oriented can be influenced by the orientation (orientation plane) of the crystal plane on the substrate surface on which the ceramic film is formed (grown). Therefore, a substrate having a surface having a crystal orientation in which the ceramic film can improve oxygen ion conductivity can be preferably selected. For example, when using the above-described nickel substrate having a structure in which the {100} plane is parallel to the rolled surface and the <001> axis is parallel to the rolling direction, the {100} plane of the substrate is used. The ceramic film formed thereon is oriented in the (a00) plane and the (aa0) plane. Here, each degree of orientation of the (a00) plane and the (aa0) plane in this ceramic film is 10% or more (typically 20% or more). Further, when a substrate made of strontium titanate having the above-described perovskite structure and oriented in the (100) plane is used, the ceramic film formed on the (100) plane of the substrate is aligned. Oriented to the (a00) plane at a degree of 100%. In addition, said a is an integer greater than or equal to 1, and the said orientation degree means the average orientation degree computed by the conventionally well-known Lottgering method from the X-ray-diffraction intensity (measured value) of the said ceramic film (patent document 8). reference).

  As described above, by forming the ceramic film oriented in a predetermined crystal plane, it is possible to obtain a ceramic film having even higher oxygen ion conductivity than a non-oriented ceramic film. That is, a ceramic membrane having such crystal orientation can be preferably used as a membrane (for example, an oxygen separation membrane) that requires high oxygen ion conductivity (oxygen permeability). Therefore, according to the technology disclosed herein, a ceramic film material composed of the substrate and a ceramic film having crystal orientation formed on the substrate, and having a higher oxygen ion conductivity A membrane material can be obtained.

An oxygen ion conductive ceramic membrane material having such a configuration can be used as an oxygen separation membrane element by including a porous support that supports the membrane material. That is, the oxygen ion conductive ceramic membrane material disclosed here is a membrane material suitable for applications requiring high oxygen ion conductivity, such as an oxygen separation membrane element.
In this oxygen separation membrane element, a part or the whole of the surface of the oxygen separation membrane made of the oxygen ion conductive membrane material is supported by a porous support. Even if this porous support is provided, the gas can easily permeate the inside thereof, so that the mechanical strength of the entire oxygen separation membrane element can be increased without lowering the oxygen permeation rate.
As the porous support, it is possible to use ceramic porous bodies having various properties that are employed in this type of conventional membrane element. Further, a material made of a material having stable heat resistance in the use temperature range of the membrane element (usually 500 ° C. or higher, typically 800 ° C. to 1000 ° C.) is preferably used. For example, a ceramic porous body having the same composition as the oxygen separation membrane having a perovskite structure, or a ceramic porous body mainly composed of magnesia, zirconia, silicon nitride, silicon carbide, or the like can be used. Alternatively, a metallic porous body mainly composed of a metal material may be used. Although not particularly limited, the average pore diameter based on the mercury intrusion method of the porous support to be used is suitably about 0.1 μm to 20 μm, and the porosity based on the mercury intrusion method is suitably about 5% to 60%. .
For the production of the oxygen separation membrane element, for example, it is necessary after joining the porous support to the surface on the ceramic membrane side in the above oxygen ion conductive ceramic membrane material so as to be bonded by a conventionally known method (for example, diffusion bonding). Accordingly, the oxygen separation membrane element provided with the ceramic membrane on the porous support can be obtained by removing the substrate constituting the oxygen ion conductive ceramic membrane material. Alternatively, it can be used without removing the substrate. For example, when the nickel substrate, which is one of the preferred examples, is used as the substrate, nickel oxide is generated when the surface of the substrate is oxidized. In the oxygen separation membrane element having such a substrate, the surface layer portion on the substrate side where the nickel oxide is present can function as an oxidation catalyst layer that promotes an oxidation reaction (for example, hydrocarbon). Therefore, a preferable oxygen separation membrane element having a configuration in which the substrate can be used as an oxidation catalyst layer can be obtained.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples.

<Example 1>
As a substrate, a substrate made of nickel having a structure in which the {100} plane in the face-centered cubic structure is parallel to the rolling surface and the <001> axis is parallel to the rolling direction (hereinafter, “Ni {100} <001> substrate ”).
Subsequently, the target was produced as follows. That is, lanthanum oxide (La ₂ O ₃ ) powder, strontium carbonate (SrCO ₃ ) powder, dioxide dioxide at a blending ratio such that La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ is obtained. Each of titanium (TiO ₂ ) powder and Fe ₂ O ₃ powder was mixed. Next, this mixture was formed into a shape that can be set in a PLD apparatus, and fired in an oxidizing atmosphere (in the air). The firing temperature was 1400 ° C to 1600 ° C.
Next, the substrate and the target were set at predetermined positions in the PLD apparatus, and the target was irradiated with a pulse laser. Thus, the vaporized target component was deposited on the substrate to form a ceramic film on the substrate. As the pulse laser, a KrF laser having a wavelength of 248 nm and a pulse width of 30 ns was used. Further, the pulse energy of the laser was 450 mJ / pulse and its frequency was 30 Hz. Film formation conditions were as follows: the target was irradiated with the laser at an energy density of 0.8 J / cm ² for 20 minutes in an Ar atmosphere of 0.04 Pa. The substrate was maintained at 750 ° C. The thickness of the ceramic film was 0.9 μm.

In the film material in which the ceramic film is formed on the substrate, the substrate side is made of a perovskite oxide (LSTF oxide) of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ. The plate-like porous support was bonded by diffusion bonding.
When the composition of the ceramic film was examined by EDX composition analysis, it was confirmed that the ceramic film was composed of a perovskite oxide of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ .

Next, the ceramic film was measured using an X-ray diffractometer (XRD), and the crystal structure of the film was analyzed. The result is shown in FIG. As shown in FIG. 1, in the ceramic film, a peak on the (a00) plane and a peak on the (aa0) plane appeared. Therefore, it was found that the ceramic film was formed on the Ni {100} <001> substrate in a state of being oriented on the two crystal planes. Note that a in the crystal plane indicates a = 1 or 2 in FIG. Further, the horizontal axis of FIG. 1 indicates the diffraction angle [degree], and the vertical axis indicates the diffraction line intensity (arbitrary unit).
Further, from the X-ray diffraction intensity obtained by this XRD measurement, the degree of orientation [%] of the (a00) plane and the (aa0) plane of the ceramic film was calculated using the Lottgering method. As a result, the orientation degree of the (a00) plane was 20%, and the orientation degree of the (aa0) plane was 25%.
From the above, it was found that the ceramic film formed on the Ni {100} <001> substrate using the PLD method is composed of the LSTF oxide oriented in the (a00) plane and the (aa0) plane.

<Example 2>
As the substrate, a substrate made of strontium titanate and oriented in the (100) plane in the perovskite structure (hereinafter referred to as “SrTiO ₃ (100) substrate”) was used. Otherwise, a ceramic film was formed on the SrTiO ₃ (100) substrate using the PLD method in the same procedure as in Example 1. Further, in the obtained film material, perovskite oxide _{La 0.6 Sr 0.4 Ti 0.1 Fe 0.9} O 3-δ on the substrate side made of (LSTF oxide) plate-shaped porous The support was bonded by diffusion bonding.
When the composition of the ceramic film was examined by EDX composition analysis, it was found to be composed of a perovskite oxide of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ , as in Example 1. confirmed.

Next, the ceramic film was measured using an X-ray diffractometer (XRD), and the crystal structure of the film was analyzed. The result is shown in FIG. As shown in FIG. 2, the (a00) plane peak appeared in the ceramic film. Therefore, it was found that the ceramic film was formed on the SrTiO ₃ (100) substrate in a state oriented to the (a00) plane. Note that a in the crystal plane indicates a = 1 or 2 in FIG. The horizontal axis in FIG. 2 indicates the diffraction angle [degree], and the vertical axis indicates the diffraction line intensity (arbitrary unit).
Further, from the X-ray diffraction intensity obtained by the XRD measurement, the degree of orientation [%] of the (a00) plane of the ceramic film was calculated using the Lottgering method. As a result, the degree of orientation of the (a00) plane was 100%. there were.
From the above, it was found that the ceramic film formed on the SrTiO ₃ (100) substrate using the PLD method is made of LSTF oxide oriented in the (a00) plane.

<Comparative example>
First, a porous support was produced. That is, an appropriate amount of a general binder and a dispersing agent was added to commercially available La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ powder (average particle diameter of about 50 μm), and these were kneaded. . Next, the kneaded product was formed into a cylindrical shape having an outer diameter of about 20 mm and a thickness of about 3 mm by press molding, and fired at 1400 ° C. Thus, a porous support made of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ (hereinafter referred to as “LSTF support”) was produced.
Next, commercially available La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ powder (average particle size of about 1 μm) is added with appropriate amounts of general binder, dispersant, plasticizer and solvent, respectively. The LSTF support was immersed in the slurry mixture and dip coated. And after drying at 80 degreeC, it heated up to 1400 degreeC by air | atmosphere atmosphere, and the baking which hold | maintains at the said temperature for 3 hours was performed. Thereby, a La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ film (LSTF film) was formed on the LSTF support.

  Next, the LSTF film (ceramic film) was measured using an X-ray diffractometer (XRD), and the crystal structure of the film was analyzed. The result is shown in FIG. The horizontal axis in FIG. 3 indicates the diffraction angle [degree], and the vertical axis indicates the diffraction line intensity (arbitrary unit). As shown in FIG. 3, in the ceramic film, peaks derived from various crystal faces appeared, and it was found that the film was not oriented on a specific crystal face and was a non-oriented film.

  About each film material obtained by the said Example 1, Example 2, and the comparative example, each oxygen ion conductivity was evaluated by measuring each electric conductivity. First, after applying a platinum paste as an electrode to each film surface of the film materials according to Examples 1 and 2 and the comparative example, a platinum wire for connecting a current terminal and a voltage terminal to the electrode part is attached 850. C. to 1100.degree. C. for 10 to 60 minutes, and by measuring the conductivity with respect to each oxygen partial pressure by the DC four-terminal method in an apparatus that can be adjusted to any oxygen partial pressure and temperature, the oxygen ion conductivity [ S / cm] was determined. Table 1 shows the measurement results of electrical conductivity under a constant temperature condition (900 ° C.).

  As shown in Table 1, it was confirmed that in Example 1 and Example 2 in which the ceramic film was oriented in a predetermined crystal plane, the oxygen ion conductivity was nearly twice as high as that in the comparative example. . Thereby, it was found that the oxygen ion conductivity was further improved in the ceramic film oriented in the crystal plane than in the non-oriented ceramic film.

  Although the present invention has been described in detail above, these are merely examples, and the present invention can be implemented in other modes, and various modifications can be made without departing from the spirit of the present invention.

2 is an X-ray diffraction spectrum of a ceramic film of an oxygen ion conductive ceramic film material according to Example 1. FIG. 3 is an X-ray diffraction spectrum of a ceramic film of an oxygen ion conductive ceramic film material according to Example 2. FIG. 3 is an X-ray diffraction spectrum of a ceramic film according to a comparative example.

Claims (7)

A method for producing an oxygen ion conductive ceramic membrane material comprising a substrate and a ceramic membrane made of an oxygen ion conductor formed on the substrate, comprising:
Preparing the substrate, wherein the substrate is made of a metal material or a ceramic material oriented in a predetermined crystal plane;
Preparing a raw material for constituting the ceramic film, wherein the ceramic film has the general formula:
A _1-x Ae _x BO _3-δ (1)
(However, A is at least one element selected from Ln (lanthanoid), Ae is one or more elements selected from the group consisting of Sr, Ba and Ca, and B is a two or more metal elements that give constitute a perovskite structure including at least Fe and Ti, a 0 ≦ x ≦ 1, δ is a value determined in the charge neutrality condition is satisfied.)
And a perovskite-type oxygen ion conductor represented by:
Forming the ceramic film on the crystal plane of the substrate by a vapor deposition method in a state of crystal orientation so that the degree of orientation is 20% or more, wherein the vapor deposition method includes a pulse laser ablation deposition method and an ion One of the beam evaporation methods;
Manufacturing method. The vapor deposition method is a pulse laser ablation deposition method, in an inert gas atmosphere of 1 × 10 ⁻⁶ Pa to 1 × 10 ³ Pa, a frequency of 1 Hz to 100 Hz, and an energy density of 100 mJ / cm ^{2 to} 2000 mJ /. It performed using a pulsed laser of cm ^2, the method according to claim 1.   As the substrate, a substrate made of nickel, which has a structure in which a {100} plane is parallel to a rolling surface and a <001> axis is parallel to a rolling direction, is used. Item 3. The method according to Item 1 or 2.   3. The method according to claim 1, wherein the substrate is a substrate made of strontium titanate and oriented to the (100) plane of the perovskite structure. 4.   An oxygen ion conductive ceramic membrane material manufactured by the method according to claim 1. A nickel substrate having a structure in which the {100} plane is parallel to the rolling surface and the <001> axis is parallel to the rolling direction, and formed on the {100} plane of the substrate An oxygen ion conductive ceramic membrane material comprising a ceramic membrane made of an oxygen ion conductor,
The ceramic membrane is
General formula:
A _1-x Ae _x BO _3-δ (1)
(However, A is at least one element selected from Ln (lanthanoid), Ae is one or more elements selected from the group consisting of Sr, Ba and Ca, and B is a two or more metal elements that give constitute a perovskite structure including at least Fe and Ti, a 0 ≦ x ≦ 1, δ is a value determined in the charge neutrality condition is satisfied.)
Consisting of a perovskite oxygen ion conductor represented by
An oxygen ion conductive ceramic membrane material characterized by being oriented at an orientation degree of 20% or more on the (a00) plane or the (aa0) plane (where a is an integer of 1 or more). An oxygen comprising a substrate made of strontium titanate and oriented in the (100) plane of a perovskite structure, and a ceramic film made of an oxygen ion conductor formed on the (100) plane of the substrate. An ion conductive ceramic membrane material,
The ceramic membrane is
General formula:
A _1-x Ae _x BO _3-δ (1)
(However, A is at least one element selected from Ln (lanthanoid), Ae is one or more elements selected from the group consisting of Sr, Ba and Ca, and B is a two or more metal elements that give constitute a perovskite structure including at least Fe and Ti, a 0 ≦ x ≦ 1, δ is a value determined in the charge neutrality condition is satisfied.)
Consisting of a perovskite oxygen ion conductor represented by
An oxygen ion conductive ceramic membrane material characterized by being oriented at a degree of orientation of 20% or more on the (a00) plane (where a is an integer of 1 or more).

Images