KR100569882B1 - Methods of surface modification in oxygen permeable membrane composed of mixed conducting perovskite - type multi - component metal oxide - Google Patents

Abstract

The present invention is a film capable of separating oxygen from an oxygen-containing gas mixture formed of a multi-component metal oxide capable of conducting electrons and oxygen ions at a temperature of about 500 ° C. or more, wherein the oxygen ion conductivity is less than the electron conductivity and oxygen In a membrane whose permeate flux is determined by the rate of oxygen-ion exchange reaction at the membrane surface, in order to enhance the oxygen permeate flux, a multicomponent metal oxide capable of conducting electrons and oxygen ions is interposed on the membrane surface. The present invention relates to a method for surface modification of an oxygen permeable separator composed of a multi-component metal oxide represented by La _1-x A _x Ga _y Fe _1-y O _3-δ .

Mixed Conductive Perovskite Multicomponent Metal Oxide, Surface Modified Layer, Oxygen Permeation Membrane

Description

Methods of surface modification in oxygen permeable membrane composed of mixed conducting perovskite-type multi-component metal oxide}             

1 is a scanning electron micrograph of an oxygen permeable membrane coated with a porous surface layer on a surface of a dense mixed conductive multicomponent metal oxide

Figure 2 is a graph of the X-ray diffraction results of the membrane modified the surface layer using the atmosphere powder

3 is a La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ separator and La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ separator and each of them when the surface layer is modified with La _0.6 Sr _0.4 CoO _3-δ composition Oxygen Permeation Velocity Graph with Temperature

4 is a graph showing X-ray diffraction results of a La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ separator having a surface modified with La _0.6 Sr _0.4 CoO _3-δ composition

5 is a graph of oxygen permeation flux according to the temperature of a membrane having a surface modified with a dense structure or a porous structure with a La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ separator and a La _0.6 Sr _0.4 CoO _3-δ composition, respectively.

FIG. 6 is a scanning electron micrograph at a portion close to the surface of a separator in which a surface modification layer having a composition of La _0.6 Sr _0.4 CoO _3-δ is coated with a double layer such as a dense structure and a porous structure.

FIG. 7 is a scanning electron micrograph at a part far from (close to the inside) of a separator in which a surface modified layer having a composition of La _0.6 Sr _0.4 CoO _3-δ is coated with a double layer such as a dense structure and a porous structure.

The present invention relates to an oxygen permeation membrane composed of a mixed conductive perovskite multicomponent metal oxide capable of selectively separating oxygen molecules from a gas mixture containing oxygen at a high temperature in a system having a relatively low oxygen partial pressure. The present invention relates to a method of modifying a surface for improvement, and more particularly, to an oxygen permeation membrane composed of a multi-component metal oxide represented by La _1-x A _x Ga _y Fe _1-y O _3-δ and a surface modification method thereof.

A separator is a barrier located between two systems in which one fluid selectively penetrates from one system to another by a driving force such as a gradient of pressure or electromotive force. Separation membranes can be classified into metals, polymers, ceramics, etc. according to the material, and depending on the structure can be divided into porous structure and dense structure, the present invention has a compact structure with a relative density of 95% or more, the volume of oxygen ions In a ceramic membrane having a function of selectively permeating oxygen by diffusion and separating the same, the present invention relates to a method of modifying a surface for improving an oxygen permeation rate. Particularly, an oxygen molecule is selectively selected through a membrane having a compact structure. In order to separate the oxygen, oxygen must be transported through the membrane in the form of ions, not in the molecular form, so the membrane must be basically an ion conductor. Yttria stabilized zirconia (YSZ) is the most widely used material as an ion conductor. Since it exhibits high ion conductivity, it has been used for a long time as an electrolyte of a solid oxide fuel cell (SOFC). In order for spontaneous and continuous movement of oxygen ions through YSZ, electrical neutrality must be maintained, and for this, electrons must be continuously supplied to the surface of the film exposed to the high oxygen partial pressure system. Therefore, in order to use yttria stabilized zirconia having a high ion conductivity but a very low electron conductivity as an oxygen permeation membrane, both surfaces of the membrane must be externally connected by an electric conductor.

Deraoka et al., Chemical Letter, pp. 1743 (1985)] La _1-x A _x Co _1-y Fe _y O _{3- ??} (A is a cation such as Ba, Sr, x is in the range of 0.1 to 1.0, y is in the range of 0.05 to 1.0.) Perovskite oxide (typically a multicomponent metal oxide represented by ABO ₃ ) Where A is selected from Groups 2 or 3 according to the Periodic Table of Elements employed by IUPAC, and B is selected from Group 3 or 4, in particular among D block transition metals. Has been reported to have higher ionic conductivity than yttria stabilized zirconia. Is a mixed conductor that exhibits high electronic conductivity as well as high ionic conductivity, so unlike Yttria stabilized zirconia, there is no need to connect electrical conductors externally. The advantage is that the configuration is simplified. In addition, partial oxidation of natural gas containing methane in the same reactor as oxygen that has passed through the membrane facilitates the production of industrially useful mixed gas (syngas, CO + H ₂ ).

Oxygen permeation through the perovskite oxide separator is characterized by the rate of diffusion of oxygen ions through the bulk of the membrane material and the rate of exchange of oxygen molecules to the ions into the membrane and the reverse reaction rate through the bulk of the membrane material. Will be determined. There has been a lot of research on the diffusion mechanism of oxygen ions in ion conductors, and while it has been established theoretically, a clear theory has not yet been established for the reactor mechanism at the surface of the separator, and also has high permeability. The problem of phase separation and cracking of the separator due to chemical instability of the constituent elements, which is pointed out as a limitation in the practical application of the perovskite separator, is only a phenomenon of observation. In particular, La _1-x A _x Co _1-y B _y O _3-δ , a perovskite multi-component metal oxide known to have excellent oxygen permeability, where A is selected from Group 2 according to the periodic table of elements employed by IUPAC. B is selected from D block transition metals, 0 <x <1.0, 0 <y <1.0, and δ is a number that neutralizes the charge of the compound). Under low conditions, the gradient of the lattice constant along the thickness direction of the film is generated, resulting in a crack and eventually unable to function as a selective separation.

See Ishihara et al., J. Am. Chem. Soc., Vol. 116, pp. 3801-3803 (1994) reported high ionic conductivity in multi-component oxides of perovskite structures based on LaGaO ₃ and partially substituted with cations such as Sr and Mg. Et al., Electrochemical and Solid state letters, Vol. 4, pp. E13-E15 (2001)] shows a higher ionic conductivity than when the cations such as Sr and Mg are partially substituted when the cations such as Sr and Fe are partially substituted on the basis of LaGaO ₃ . It has been reported to be structurally stable, but the perovskite multicomponent oxide of La _1-x Sr _x Ga _y Fe _1-y O _3-δ composition has a low rate of oxygen-ion exchange reaction at the membrane surface. There is a problem in itself that is difficult to use in the separator [Kim et al., J. Electrochem. Soc., Vol. 147 pp. 2398-2406 (2000).

As described above, in the separation membrane of La _1-x Sr _x Ga _y Fe _1-y O _3-δ composition which has excellent structural stability and ion conductivity but low exchange reaction rate on the surface, Means for modifying the surface of the mixed conductive perovskite-based multi-component metal oxides having the same structure and modifying the surface while providing an oxygen permeation membrane having improved overall permeate flow rate while maintaining the advantages of high stability. Its features are provided.

In the present invention, the dense film intended to modify the surface is La _1-x A _x Ga _y Fe _1-y O _3-δ (where A is selected from group 2 according to the periodic table of elements employed by IUPAC, where 0 <x <1.0, 0 <y <1.0, and δ is a number that makes the charge of the compound neutral. The powder is solid phase reaction method, coprecipitation method, neutralization precipitation method, citric acid method, combustion synthesis method, etc. It can be synthesized by the method of. The synthesized powder was uniaxially pressed using a disk or square metal mold, and cold hydrostatic pressure (CIP) was applied at a pressure of 140 MPa or more. Molded green compacts having a molding density of 55 to 60% of the theoretical density may be prepared, or mixed with an organic binder, etc., extruded or injected to form a tube. In order to selectively separate pure oxygen from the oxygen-containing gas mixture, the membrane must be dense with a porosity of less than 5%. This is to prevent gas other than oxygen from permeating through the internal pores in molecular form.

La _1-x A _x Co _y B _1-y O _3-δ , consisting of components to modify the surface with some metal cations substituted in the separator composition, where A is 2 according to the periodic table of elements employed by IUPAC Selected from the group, B is selected from the D block transition metals, 0 <x <1.0, 0 <y <1.0, and δ is a number that neutralizes the charge of the compound). The multicomponent metal oxide capable of conducting can be synthesized by a solid phase reaction method, a liquid phase method, a combustion synthesis method, or the like. In the solid phase reaction method, each constituent metal oxide or metal salt having a purity of 99% or more is mixed according to the molar ratio of the final compound, and synthesized by reaction by heating at 800 ° C. or higher for 5 hours or more. Whether the synthesized powder formed a single-phase perovskite structure can be confirmed by X-ray diffraction. If the constituent metal oxide or the like does not form a perovskite single phase even after heat treatment and does not react, it does not exhibit mixed conductivity, and thus is unsuitable for the surface exchange reaction, thereby reducing the overall oxygen permeation flow rate. Therefore, the perovskite single phase must be heated to a temperature at which it can be formed and heat treated, and may vary depending on the composition, but the single phase is formed at about 800 ° C. or more.

La _0.6 Sr _0.4 CoO _3-δ Perovskite Single phase La ₂ O ₃ , SrCO ₃ , Co (NO) ₂ · 6H ₂ O were weighed according to the molar ratio, and then the polypropylene vessel and the zirconia ball were Isopropyl alcohol (2-PrOH) is used as a solvent for milling and mixing for 24 hours. The mixed powder is kept in the hood for 24 hours to evaporate the solvent, then dried in a drier maintained at 110 ° C. for at least 24 hours, milled in mortar and heated at 1000 ° C. for at least 5 hours. The heat-treated powder was again milled for 24 hours using isopropyl alcohol as a solvent using a polypropylene container and a zirconia ball, followed by drying to obtain a synthetic powder. The synthesis of perovskite single phase is confirmed using X-ray diffraction.

<Surface Modification Using Screen Printing>

As an example of surface layer modification using the screen printing method of this invention, the series structure is as follows. A slurry was prepared by mixing the synthesized La _0.6 Sr _0.4 CoO _3-δ powder with an organic binder. The solvent uses alpha-Tepineol (α-Terpineol) having high volatilization temperature and excellent solubility, and ethyl cellulose (Ethyl cellulose) having high solubility and printing property in α-Terpineol is used as a binder. Fish oil is used as a dispersant and polyethylene glycol (PEG) and dibutyl phthalate (DBP) are used as a plasticizer. The relative proportions of the organic powders such as the solvent and the binder and the ceramic powder and the particle size distribution of the ceramic powder affect the viscosity of the printing slurry, and thus determine the porosity and shape of the surface modification layer. In addition, the thickness and density of the surface modification layer can be adjusted according to the number of times of printing. As a result of the practice for the present invention, the composition ratios shown in Table 1 were determined to be the most desirable for controlling the drying speed and the shape of the printing layer.

Table 1

function material % By mass (for organic matter) % By mass (total) menstruum α-Terpineol 85 60 Binder Ethylene glycol 7 Dispersant Fish oil 2 Plasticizer PEG + DBP 6 Ceramic powder 40

After polishing both surfaces of the separator to 10 μm, the mixed slurry is printed on both surfaces of the separator using a 200 mesh screen and then dried. Heat treatment is performed at a temperature of 700 ° C. or higher to remove organic matter remaining on the printed surface layer. The porosity of the surface layer is changed according to the heat treatment temperature, and thus the composition is changed at the surface of the separator, and the composition is gradually changed toward the inside of the separator, and the heat treatment is performed at 1,300 ° C. or lower to prevent excessive oversintering. The grain size of the surface modification layer is excessively increased to prevent uneven cracking and peeling from the separator.

<Surface layer reforming method using atmosphere powder>

As an embodiment of the surface layer modification using the atmosphere powder of the present invention, La _1-x A _x Ga _y Fe _1-y O _3-δ to modify the surface, where A is a group according to the periodic table of elements employed by IUPAC Is selected from 0 <x <1.0, 0 <y <1.0, and δ is a number to neutralize the charge of the compound), a multicomponent metal oxide composition, solid state reaction, coprecipitation method, neutralization precipitation method, citric acid method , The powder synthesized by the method of combustion synthesis, etc. is uniaxially press-molded using a disk-shaped or square metal mold, and subjected to cold hydrostatic pressure (CIP) at a pressure of 140 MPa or more, which corresponds to 55-60% of the theoretical density. A molded green compact having a porosity (35% -45%) is prepared, or mixed with an organic binder or the like to be extruded or injected to form a tube or the like.

The molded green compact is charged into an alumina crucible and heat-treated, and the single-component or multi-component metal oxide composed of a component which is partially replaced by metal cations in the green compact composition is surrounded by the molded green compact and then subjected to electrical resistance. Heat in air at a temperature of 1200 ~ 1600 ℃ using. In other words, it is possible to obtain a perovskite single phase that can perform the function of the surface modification layer only when the heat treatment is performed at a temperature of 1200 ° C. or higher, and when the heat treatment is performed at a temperature of 1600 ° C. or higher, the surface modified layer is oversintered. Grain size increases excessively, density decreases remarkably, and mechanical properties become poor, making it unsuitable for use as a separator.
In this case, the atmosphere powder around the molding compact should have a molding density of less than 30% to prevent densification by heat treatment. In this case, the composition distribution on the surface of the separator densified from the molding compact is determined by the heat treatment temperature and the porosity of the atmospheric powder.

When a green compact of La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ is enclosed with an oxide powder of ZrO ₂ and heat-treated at 1500 ° C., Zr, a transition metal, is substituted at the B site of the perovskite structure. Thus, the surface layer of the densified membrane has a composition of La _0.7 Sr _0.3 Ga _{1-y-y '} Fe _y' Zr _y O _3-δ . This can be verified through X-ray diffraction analysis. In FIG. 2, the vertical line on the left is the position of 2θ corresponding to the (311) plane of the Si metal used as a reference material for correction of the measured value, and the right side is a _{ferof having a} composition of La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ. It is the position of 2θ corresponding to the (211) plane of the skytecture. As shown below, the result of the membrane with the unmodified La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ composition clearly shows that one peak corresponding to the (211) plane is measured, but the top surface is shown above. On the surface of this modified separator, many peaks with different peak positions are measured. The change in the position of the peak means that cations with different ionic radii are substituted.

The oxygen permeation flow rate of the membrane is measured at high temperature using a heating furnace using a heating element capable of heating up to at least 1000 ° C. The surface-modified separator specimen is bonded to a support mounted inside the heating furnace, and ring-shaped gold or silver is used as the sealing material to prevent gas leakage. The sealing of both systems centered on the membrane specimen is carried out by nitrogen gas, etc., flowing in one system and the inert, high-purity gas (Ar or He, etc.) flowing in one system at the maximum temperature measured. Judgment is made using a detection apparatus such as gas chromatography.

In order to measure the amount of oxygen permeated through the membrane, the following method is used. Measure the oxygen partial pressure in the region with high oxygen partial pressure and adjust it to have a constant flow rate. In the low oxygen partial pressure region, the oxygen partial pressure of the inert, high-purity carrier gas is measured and adjusted using a mass flow controller to achieve a constant flow rate. Record the value when the oxygen permeation flow is steady at a constant temperature and pressure.

After the measurement of the permeation flux, the specimens are visually observed after cooling to determine the formation of cracks, and after the specimens are separated from the reactor, the microstructure is observed using a scanning electron microscope. In addition, X-ray diffraction is used to determine whether a new phase is generated and the change of lattice constant.

In order to compare the effects of the present invention, as a mixed conductive multicomponent metal oxide, Stevenson et al., J. Electrochem. Soc., Vol. 143, pp.2722 (1996)], and the oxygen permeation characteristics of the La _1-x Sr _x Co _y Fe _1-y O _3-δ composition separation membrane reported to have a high oxygen permeation flux as a comparative example. 3 is a La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ separator and La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ separator and each of them La _0.6 Sr _0.4 CoO _3-δ composition is modified by screen printing method The oxygen permeation flow rate measured according to the reaction temperature is shown. La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ is LSCF, La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ is LSGF, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _{3- δ} If the modification of the surface with La _0.6 Sr _0.4 CoO _3-δ is LSC / LSCF, and _{La 0.7 Sr 0.3 Ga 0.6 Fe 0.4} O 3-δ the surface of the membrane La _0.6 Sr _0.4 CoO when the modification to the _3-δ is LSC / LSGF. For specimens without surface modification, LSCF showed a higher oxygen permeation rate than LSGF and a value of 0.25 ml / cm ² min at the highest measurement temperature of 950 ° C. But La _0.6 Sr _0.4 CoO _{3- ??} When the surface is modified by the composition, La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ shows a significant increase in oxygen permeation flow rate and a value of 0.48 ml / cm ² min at 950 ° C. On the other hand, the membrane having the composition of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ exhibited almost similar oxygen permeation flux over the entire range of the measured temperature and unmodified surface even when the surface was modified. It can be seen that it does not receive.

Therefore, La _1-x A _x Co _y Fe _1-y O _3-δ (where A is selected from group 2 according to the periodic table of elements, such as Ba, Sr, Ca, and 0 <x <1.0, 0 <y <1.0) The separation membrane of the composition is one of the two factors that determine the oxygen permeation flux, and since the diffusion rate of oxygen ions through the bulk determines the overall oxygen permeation flux, the effect of surface modification does not occur, while La _{1- x} A _x Ga _y Fe _1-y O _3-δ (where A is selected from group 2 according to the periodic table of elements, such as Ba, Sr, Ca, etc., and 0 <x <1.0, 0 <y <1.0) As described above, the Ropezite multi-component metal oxide has a high conductivity of oxygen ions through the bulk and a relatively low exchange reaction rate on the surface, thereby determining the flow rate of the total oxygen permeation, thereby increasing the surface exchange reaction rate. When the surface is modified with La _0.6 Sr _0.4 CoO _3-δ composition, the oxygen permeation rate may be increased.

The shape and density of the surface layer can be adjusted according to the method of manufacturing the surface modification layer, and the composition can be continuously changed from the surface of the separator to the inside. As the composition of the surface modification layer and the membrane changes, chemical and structural stability in a high temperature reducing atmosphere changes, so it is important to control the shape and density of the surface layer through various manufacturing methods.

The change in composition can be judged from the result of X-ray diffraction. In FIG. 4, the three vertical lines correspond to the (211) planes of La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _3-δ, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ, and La _0.6 Sr _0.4 CoO _3-δ , respectively. Is the position of the peak. The X-ray diffraction peak shown below is a thick film having a porous La _0.6 Sr _0.4 CoO _3-δ composition on the surface, and in addition to the La _0.6 Sr _0.4 CoO _3-δ peak, a peak is observed near 58 degrees. . The X-ray diffraction peak shown at the top is measured at the boundary between the separator and the surface modified layer by artificially removing the La _0.6 Sr _0.4 CoO _3-δ modified layer from the surface, La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _{3 The} main peak is observed between the _-δ characteristic peak position and La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3-δ characteristic peak position, and many peaks are observed near the high angle near 58.5 °. This composition of the membrane _{La 0.7 Sr 0.3 Ga 0.6 Fe 0.4} O 3-δ and surface modification layer of La _0.6 Sr _0.4 CoO _3-δ between B- seat (-site) by substitution of the cationic La _1-x Sr _x Co _y Ga _{y '} Fe _1-y-y' O _3-δ means that the modified to the composition, the surface layer of this composition is acting in the surface exchange step of the membrane.

By adjusting the porosity of the surface modification layer, the oxygen permeation flow rate can be varied. 5 is _{La 0.7 Sr 0.3 Ga 0.6 Fe 0.4} O 3- _δ of the membrane composition of La _0.6 Sr _0.4 CoO _3-δ composition but modifying the surface using a screen printing method to, by varying the heat treatment temperature, the surface modification layer Oxygen permeation flux was measured for the specimens prepared by adjusting the porosity. The oxygen permeation flux was observed to be increased when the surface was modified. In particular, when the dense coating was applied, the oxygen permeation flux was 0.16 ml / cm ² min at 950 ° C. ), The coating showed a high flow rate of 0.48 ml / cm ² min . Therefore, when the effective surface area of a surface modification layer is large, it turns out that the effect of surface modification is remarkable.

From the X-ray diffraction results at the interface between the separator and the surface modification layer, it can be seen that when the dense coating is applied, the degree of modification of the cation into the separator and the composition thereof is large. On the other hand, a change in the composition of the surface modification layer causes a change in the fracture pattern.

In the case of La _1-x Sr _x MnO _3-δ , which is used as a cathode electrode material of a solid oxide fuel cell (SOFC), a major surface exchange reaction occurs at a triple point where an electrolyte, an electrode, and a gas phase come into contact with each other. It is known that the material should be porous. In order to obtain an efficient oxygen permeation flux using a surface modification layer having a La _1-x Sr _x CoO _3-δ composition, it is necessary to confirm whether or not the same mechanism as in the case of La _1-x Sr _x MnO _3-δ is used. La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O _{3-δ on} the separator with the composition La _0.6 Sr _0.4 CoO _3-δ to modify the surface by screen printing method, by controlling the heat treatment temperature, the compact and porous modified layer Oxygen permeation characteristics were evaluated after two layers of were coated successively. In the region adjacent to the boundary between the membrane and the surface modification layer, there is a tendency of transgranular fracture (FIG. 6), while internally there is a tendency of intergranular fracture (FIG. 7), which is due to the difference in composition. It is.

It is a photograph of LSCF membrane which cracked at 850 ℃ after performing oxygen permeation experiment at 950 ℃ for over 100 hours. The crack formation is similar to that of a typical biaxial fracture specimen, and the fracture occurs at the top of the specimen (He-side).

Substitution of a divalent cation in the A-site of the perovskite structure increases the oxidation number of the oxygen vacancy or B-site cation in a high-temperature reducing atmosphere. When the concentration of oxygen vacancy increases at high temperature, the B-site cation Is reduced again by giving off electrons, which causes the lattice to expand. As described above, in the system containing Co, such as La _1-x A _x Co _y B _1-y O _3-δ , chemical separation is possible under a high temperature reducing atmosphere, and phase separation is likely to occur. The flow rate is reduced or the mechanical strength is reduced. On the other hand, a system containing Ga is relatively stable. Therefore, as in the present invention, when the Co-based surface having excellent surface reaction rate is interposed with a surface modification layer having a porosity-controlled form rather than a bulk form, the chemical stability at the surface can be improved and the possibility of cracking can be lowered. Can maintain structural stability. In addition, the high bulk ion conductivity of the separator having a low surface exchange rate of La _1-x A _x Ga _y Fe _1-y O _3-δ can be effectively used through surface modification.

Claims (3)

La _1-x A _x Ga _y Fe _1-y O _3-δ (where A is selected from group 2 according to the periodic table of elements employed by IUPAC, 0 <x <1.0, 0 <y <1.0, and σ is Oxygen as a dense membrane made by sintering a green compact synthesized by uniaxial or hydrostatic pressure from a powder synthesized as a single-phase perovskite single phase, a multi-component metal oxide, which neutralizes the charge of a compound). In the permeable membrane, La _1-x A _x Co _y B _1-y O _3-δ on the surface of the sintered dense membrane, where A is selected from group 2 according to the periodic table of elements employed by IUPAC, and B is Selected from D block transition metals, where 0 <x <1.0, 0 <y <1.0, and σ is a number that neutralizes the charge of the compound) and La _1-x A _x Co _y Ga _{y '} B _y Fe _{1-y-y'-y "} O to form a modified surface layer consisting of two layers each having a composition represented by _3-δ , La _1-x A _x Co _y Ga _{y '} B _y" Fe _{1- y-y'-y "O 3-} The composition layer forms the boundary layer surface and the surface layer of the sintered body in contact with _{La 1-x A x Co y} B 1-y O 3-δ composition layer is an oxygen permeable membrane having a modified surface layer formed in the outermost surface layer made of the surface layer. La _1-x A _x Ga _y Fe _1-y O _3-δ (where A is selected from group 2 according to the periodic table of elements employed by IUPAC, 0 <x <1.0, 0 <y <1.0, and σ is A compacted film prepared by uniaxially or hydrostatically press-molding a powder formed of a powder composed of a single-phase perovskite single phase, a multi-component metal oxide represented by the neutral charge of a compound, is prepared. In the method of modifying the surface layer of the oxygen permeation membrane, La _1-x A _x Co _y B _1-y O _3-δ in which the metal cation is partially substituted in the film composition on the surface of the sintered dense film, where A is in group 2 according to the periodic table of elements employed by IUPAC B is selected from D block transition metals, 0 <x <1.0, 0 <y <1.0, and σ is a number that neutralizes the charge of the compound) Method of modifying the surface layer of the oxygen permeation membrane by applying the slurry, printing it to a screen, drying and heating to a temperature of 700 ° C to 1300 ° C to form the modified surface layer of claim 1 on the surface of the sintered body. La _1-x A _x Ga _y Fe _1-y O _3-δ (where A is selected from group 2 according to the periodic table of elements employed by IUPAC, 0 <x <1.0, 0 <y <1.0, and σ is A compacted film prepared by uniaxially or hydrostatically press-molding a powder formed of a powder composed of a single-phase perovskite single phase, a multi-component metal oxide represented by the neutral charge of a compound, is prepared. In the method of modifying the surface layer of the oxygen permeation membrane, A green powder synthesized with a single phase of perovskite, which is a multi-component metal oxide represented by La _1-x A _x Ga _y Fe _1-y O _3-δ , which has a porosity of 35 to 45%. La _1-x A _x B _y B ' _1-y O _3-δ with a partially substituted metal cation in the composition, where A is selected from group 2 according to the periodic table of elements employed by IUPAC, and B is a D block transition metal is selected from, 0, and <x <1.0, 0 <y <1.0, σ is put in the powder of the multicomponent metallic oxide represented the charge of the compound as a number) to create a neutral when a heat treatment at a temperature of 1200 ~ 1600 ℃ The green compact is a sintered compact and forms the modified surface layer of claim 1 on the outer surface of the sintered compact, After sintering the green compact, the sintered compact was subjected to La _1-x A _x B _y B ' _1-y O _3-δ in which the metal cation was partially substituted in the composition of the sintered compact, wherein A is 2 according to the periodic table of elements employed by IUPAC. Selected from the group, B is selected from among the D block transition metals, 0 <x <1.0, 0 <y <1.0, and σ is a number that neutralizes the charge of the compound). Method of modifying the surface layer of the oxygen permeable membrane to form a modified surface layer of claim 1 on the outer surface of the sintered body by heating to 700 ~ 1300 ℃

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