JP2006188372A - Manufacturing method of ceramic powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a ceramic powder which has a homogeneous or dispersed particle structure. <P>SOLUTION: The manufacturing method of the ceramic powder for manufacturing the ceramic power containing one or more metal oxides comprises a material liquid-preparing step wherein a material liquid is prepared and a synthesis step wherein the material liquid in a droplet form is heated to synthesize a ceramic. Here, the material liquid contains metal salts, which are salts of metals composing the metal oxides, and a chelating agent containing an electron donor group which is capable of chelating metal cations and a polymerizable functional group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for producing a ceramic powder, and more particularly, to a ceramic powder, a material for an electrode of a solid oxide fuel cell, a solid oxide fuel cell, and a method for producing the same.

  Examples of the ceramic powder used as the fuel electrode material of the solid oxide fuel cell include cermets such as Ni-Sm-added ceria (hereinafter simply referred to as SDC). In a fuel electrode of a solid oxide fuel cell, an electrode reaction occurs at three interfaces (three-phase interface) of an ion conduction path by metal oxide ions, an electron conduction path mainly composed of Ni, and a fuel path. Yes. Therefore, in order to improve the electrode performance, it is required to prevent aggregation of metallic Ni in the fuel electrode and increase the three-phase interface in the fuel electrode.

Under such circumstances, it has been proposed to use, as a fuel electrode material, ceramic powder containing capsule composite particles having NiO as a core and SDC as a shell (Patent Document 1).
JP 9-309768 A

  However, such capsule-type composite particles are effective in preventing aggregation of metallic Ni, but are not necessarily effective in terms of increasing the three-phase interface. Further, in such capsule-type composite particles, when Ni is deposited by reduction from NiO, it is necessary to expose Ni on the surface of the composite particles, but such precipitation control is difficult.

  Furthermore, spray pyrolysis, in which metal salt solution is converted into droplets and pyrolyzed, is effective for synthesizing ceramic powder particles, but the presence of metal oxide phase or particles in the synthetic ceramic particles is highly controlled. It was difficult to do. In particular, the structure control in composite particles containing two or more kinds of metal oxides is not easy, and the particle structure tends to be determined depending on the sinterability of the metal oxides generated by thermal decomposition. It was unexpectedly difficult to obtain dispersed particles having the above metal oxide phase dispersed in the particles.

  Therefore, an object of the present invention is to provide a ceramic powder having a dispersed particle structure and a method for producing the same. Another object of the present invention is to provide a solid oxide fuel cell electrode material having a homogeneous or dispersed particle structure, a solid oxide fuel cell, and a method for producing the same.

  In view of the problems described above, the present inventors have further studied particle structure control in the spray pyrolysis method, and as a result, it is possible to control the particle structure by adding a chelating agent capable of chelating metal cations in the raw material liquid. The inventors have found that the particle morphology can be controlled by adjusting the degree of chelation by the chelating agent or the degree of polymerization of the chelating agent, thereby completing the present invention. That is, according to the present invention, the following means are provided.

  According to the first aspect of the present invention, there is provided a method for producing a ceramic powder containing one or more metal oxides, wherein the metal salt is a metal salt constituting the metal oxide and the metal. A raw material liquid preparation step for preparing a raw material liquid containing a chelating agent having an electron donating group and a polymerizable functional group capable of chelating a cation of the cation, and the ceramic material is synthesized by heating the raw material liquid formed into droplets And a synthesis step.

  In this embodiment, the chelating agent is selected from the group consisting of ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and ethylene glycol oligomers. It can be 1 type or 2 types or more. Of these, the chelating agent is preferably ethylene glycol. Furthermore, in these forms, in the raw material liquid, the chelating agent is preferably contained in a molar ratio with respect to the metal cation of 0.2 or more and 10 or less.

  Further, in this embodiment, a polymerization step of polymerizing at least a part of the chelating agent in the raw material liquid can be provided prior to the synthesis step. This polymerization step may include a step of heating the raw material liquid at a temperature of 70 ° C. or higher and 130 ° C. or lower.

  Furthermore, in this embodiment, the synthesizing step can be a step of synthesizing ceramics by passing the raw material liquid formed into droplets through a heating furnace held at a high temperature from the introduction part to the discharge part. .

  In this embodiment, the ceramic powder can contain composite ceramic particles having two or more metal oxide phases dispersed therein. In this aspect, the ceramic powder is a material for an electrode of a solid oxide fuel cell, and two or more kinds of the metal oxide are a metal oxide and a solid oxide that are conductive materials of a solid oxide fuel cell. And a metal oxide which is a material for a support of a fuel cell.

  In addition, according to the 1st form of this invention, the ceramic powder obtained by the manufacturing method of such a ceramic powder is provided.

According to the second aspect of the present invention, there is provided a ceramic powder that is a ceramic powder and contains composite ceramic particles provided with dispersed phases of two or more metal oxides having different sinterability. In this embodiment, the phase of the two or more metal oxides includes a first or second metal oxide selected from the group consisting of NiO, Co ₂ O ₃ and Fe ₂ O ₃ . Phase, M _x Ce _1-x O _{(1-x) / 2} (where M is selected from Gd, Sm and La, and 0.1 ≦ x ≦ 0.8), Y ₂ O ₃ adding _ZrO 2, _Sc 2 _{O 3} additive can be the second phase comprising one or more metal oxides selected from the group consisting of ZrO ₂ and CaO addition ZrO _2. The composite ceramic particle may be a porous spherical body or a flake shape. The average particle system of the composite ceramic particles is preferably 2 μm or less, and the average particle diameter of the first phase and the second phase is preferably 200 nm or less. Such ceramic powder can be used as an electrode material for a solid oxide fuel cell.

  Moreover, according to the 3rd form of this invention, it is a manufacturing method of a solid oxide fuel cell, Comprising: A manufacturing method provided with the process of baking the ceramic powder as described in any one of the above, and forming a fuel electrode. Provided.

  Furthermore, according to the 4th form of this invention, it is a solid oxide fuel cell, Comprising: The solid oxide fuel cell provided with the fuel electrode which uses the ceramic powder in any one of the above as a raw material is provided.

  The method for producing a ceramic powder according to the present invention is a method for producing a ceramic powder containing one or more metal oxides, the metal salt being a metal salt constituting the metal oxide and the metal powder. A raw material liquid preparation step for preparing a raw material liquid containing an electron donating group capable of chelating a cation and a chelating agent having a polymerizable functional group, and a synthesis for synthesizing ceramics by heating the raw material liquid formed into droplets And a process. In addition, the ceramic powder of the present invention is characterized in that it contains composite ceramic particles provided with dispersed phases of two or more metal oxides having different sinterability.

  According to this production method, a raw material liquid containing a chelating agent having a metal salt corresponding to a metal oxide, an electron donating group capable of chelating the metal cation, and a polymerizable functional group in the raw material liquid. When synthesizing ceramics by dropletization and heating, the metal oxide phase in the produced ceramic particles can be uniformly dispersed. Moreover, a fine metal oxide phase can be dispersed. When two or more kinds of metal oxide salts are included, ceramic particles in which two or more metal oxide phases are dispersed almost uniformly and finely can be obtained. Furthermore, by adjusting the degree of chelation by the chelating agent or the degree of polymerization, the resulting ceramic particles can be controlled in the form of particles such as porous spheres, flakes (including shells), and hollow spheres. Further, the particle structure of the ceramic powder of the present invention is provided with dispersed metal oxide phases having different sinterability, and each phase is finely dispersed. A ceramic fired body having a fine structure can be obtained. Hereinafter, various embodiments of the present invention, that is, a method for producing ceramic powder, a ceramic powder, a solid oxide fuel cell electrode material, a method for producing a solid oxide fuel cell (hereinafter simply referred to as SOFC), and SOFC are sequentially described. explain.

(Manufacturing method of ceramic powder)
(Raw material preparation process)
In the method for producing a ceramic powder of the present invention, first, a raw material liquid containing a metal salt which is a metal salt constituting one or more metal oxides to be obtained and a chelating agent is prepared. Although it does not specifically limit as a metal oxide, According to this invention, the particle | grains of a dispersion | distribution form are obtained, and the type | mold composite particle | grain provided by disperse | distributing and providing two or more types of metal oxide phases from two or more types of metal oxides is obtained. Therefore, it is preferable to target two or more metal oxides. In addition, according to the present invention, since the sinterability can be controlled, that is, the dependence of the metal oxide on the sinterability can be suppressed, it is preferable to target metal oxides having different sinterability. . Note that in this specification, metal oxides include composite oxides.

As fuel electrode materials of SOFC, nickel oxide (NiO), solid solution of nickel oxide (NiO) and magnesium oxide (MgO), cobalt oxide (Co ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), A metal oxide such as ruthenium oxide can be used as the conductive material. In addition, examples of metal salts corresponding to these include various salts and hydroxides such as acetates, nitrates, carbonates, and oxalates of these metals. Further, as the support material of the SOFC fuel electrode, stabilized zirconia (FSZ) such as Y ₂ O ₃ added ZrO ₂ , Sc ₂ O ₃ added ZrO ₂ and CaO added ZrO ₂ and partially stabilized zirconia (PSZ), Examples thereof include metal oxides such as cerium oxide doped with a rare earth oxide (M _x Ce _1-x O _{(1-x) / 2} ). Examples of metal salts corresponding to these include acetates, nitrates, carbonates, oxalates, hydroxides, and the like of these metals. These raw material liquids such as metal salts can be prepared by dissolving various metal oxides in a solution containing a counter ion capable of forming a metal salt such as concentrated acid.

Among these, the conductive material for the fuel electrode is preferably selected from NiO, Co ₂ O ₃ and Fe ₂ O ₃ . The support material for the fuel electrode is M _x Ce _1-x O _{(1-x) / 2} (where M is selected from Gd, Sm, and La, and 0.1 ≦ x ≦ 0.8) And Y ₂ O ₃ -added ZrO ₂ , Sc ₂ O ₃ -added ZrO ₂ and CaO-added ZrO ₂ . In Y ₂ O ₃ added ZrO ₂ , Y ₂ O ₃ is preferably 3 mol% or more and 10 mol% or less, and in Sc ₂ O ₃ added ZrO ₂ , Sc ₂ O ₃ is 3 mol% or more and mol% or less. In the case of CaO-added ZrO ₂ , CaO is preferably 5 mol% or more and 20 mol% or less. In addition, the group of NiO, Co ₂ O ₃ and Fe ₂ O ₃ , M _x Ce _1-x O _{(1-x) / 2} , Y ₂ O ₃ added ZrO ₂ , Sc ₂ O ₃ added ZrO ₂ and CaO added The sinterability is different from that of the ZrO ₂ group, and by selecting one or more from each of the two groups, ceramic composite particles having the respective metal phases dispersed therein can be obtained.

Further, as the SOFC air electrode material, (La, Sr) MnO ₃ , (La, Ca) MnO ₃ , (La, Sr) CoO ₃ , (La, Ca) CoO _3, etc. are metal oxides that become conductive materials. It is mentioned as a thing. As metal salts corresponding to these metals, various salts such as acetates, nitrates, carbonates and oxalates of each metal or hydroxides can be used. Further, as the support material for the SOFC air electrode, stabilized zirconia (FSZ) such as Y ₂ O ₃ added ZrO ₂ , Sc ₂ O ₃ added ZrO ₂ and CaO added ZrO ₂ and partially stabilized zirconia (PSZ), Examples thereof include metal oxides such as cerium oxide doped with a rare earth oxide (M _x Ce _1-x O _{(1-x) / 2} ). Examples of metal salts corresponding to these include acetates, nitrates, carbonates, oxalates, and the like of these metals. These raw material liquids such as metal salts can be prepared by dissolving various metal oxides in a solution containing a counter ion capable of forming a metal salt such as concentrated acid.

  Further, when the ceramic powder is used for a catalyst, a metal serving as a catalyst material or a metal oxide and a metal oxide serving as a support material can be used. Examples of the catalyst material include metals such as nickel, cobalt, and iron, and metal oxides such as zinc oxide, tin oxide, copper oxide, lanthanum manganate, and titanium oxide. Examples of the carrier material include aluminum oxide, silicon oxide, magnesium oxide, and titanium oxide. Raw material liquids such as constituent metal salts of these metal oxides can be prepared by dissolving various metal oxides in a solution containing a counter ion capable of forming a metal salt such as concentrated acid.

  The chelating agent preferably has an electron donating group and a polymerizable functional group that chelate metal cations in the raw material solution. The electron donating group is preferably an ether group or a hydroxyl group. In any of these electron donating groups, it is presumed that the oxygen atom is involved in the chelation of the metal cation. The polymerizable functional group is preferably a double bond polymerizable functional group or a functional group that condenses by dehydration, such as a carboxyl group, an amino group, or a hydroxyl group. Of these, a hydroxyl group is preferred. Accordingly, examples of the chelating agent include oxycarboxylic acids such as citric acid and acrylic acid, polyamines such as ethylenediaminetetraacetic acid, and polyols such as ethylene glycol.

  In the present invention, polyols are preferable. Among them, alkanediols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, ethylene And an oligomer of glycol (with a degree of polymerization of 2 or more and 7 or less). This is because the metal cation can be sufficiently chelated when the degree of polymerization is 7 or less. More preferably, the degree of polymerization is 2 or more and 5 or less. Most preferred as the polyol is ethylene glycol.

  The chelating agent is contained in the raw material liquid to such an extent that the dispersion form can be controlled, but preferably it is contained in a molar ratio of 0.2 to 10 in terms of the molar ratio to all metal cations in the raw material liquid. This is because if the molar ratio is 0.2 or more, the chelate partly proceeds with polymerization, and if it is 10 or less, the chelating agent does not adversely affect the thermal decomposition. More preferably, it is 1 or more and 8 or less. More preferably, it is 1 or more and 5 or less.

  The raw material liquid is prepared so as to contain such metal salts and a chelating agent. Preferably, a chelating agent is added to the metal salt solution and mixed. In the raw material solution, the metal cation is presumed to be chelated by the chelating agent, but in order to promote chelation, it is preferable to polymerize the chelating agent. The initiation of polymerization of the chelating agent varies depending on the type of polymerizable functional group possessed by the chelating agent. In the case of the above polyols, the polymerization is easily promoted by appropriate heating. For example, in the case of ethylene glycol, it is possible to effectively polymerize and promote chelation by heating to 70 ° C. or higher, preferably 80 ° C. or higher. Moreover, it is preferably 130 ° C. or lower, more preferably 120 ° C. or lower, and further preferably 100 ° C. or lower.

  The degree of chelation and polymerization is not particularly limited, but the form of ceramic particles obtained depends on the degree of chelation or polymerization. When the polymerization is not carried out by heating or the like, the ceramic particles are likely to become flaky particles such as hollow spherical particles or skin particles of such hollow particles. On the other hand, when polymerized, porous spherical particles are easily obtained. For example, when ethylene glycol and its oligomer (polymerization degree is 2 or more and 7 or less) are polymerized, a ceramic powder mainly composed of spherical and porous particles can be obtained. As polymerization conditions, ceramic powder mainly composed of spherical and porous particles when polymerized under heating conditions of 70 ° C. to 120 ° C. for 6 hours to 10 hours using ethylene glycol as a chelating agent. Is obtained.

(Synthesis process)
The synthesizing step is a step of synthesizing ceramics by making the raw material liquid into droplets and heating. When the raw material liquid is formed into droplets, it can be diluted with a solvent such as water as necessary. For example, when the viscosity is increased by carrying out the polymerization step, it is preferable to dilute to a viscosity suitable for droplet formation.

  Various liquid atomization methods such as a commonly used spraying method and ultrasonic method can be used for droplet formation without particular limitation. The droplets can be heated using a suitable heating furnace or the like. For example, the droplets may be introduced into the heating furnace using a carrier gas that can transfer the droplets of the raw material liquid. The form of the heating furnace is not particularly limited, but in consideration of the formation of droplets of the raw material liquid, heating / synthesis, and recovery of the synthesized ceramics, a tubular heating furnace capable of passing the liquid droplets of the raw material liquid with a carrier gas is used. It is preferable.

  An example of such a ceramic synthesizer 2 is shown in FIG. A synthesizer 2 shown in FIG. 1 includes a droplet forming unit 4 including an ultrasonic vibrator, a tubular heating furnace unit 8 communicating with the droplet forming unit 4 via a communication tube 6, and a heating furnace unit 8. The dust collection part 10 installed continuously is provided. The heating furnace unit 8 includes heating furnaces 8a, 8b, 8c, and 8d that are continuously provided along the moving direction of the carrier gas, that is, the moving direction of the liquid droplets of the raw material liquid, and these heating furnaces 8a to 8d. The heating temperature can be set individually, and normally the heating temperature is set to a higher temperature sequentially from the droplet introduction part to the discharge part.

  Although not restricting the present invention, according to such a synthesis step, metal ions are present in a state of being uniformly dispersed by being chelated by a polymerized or non-polymerized chelating agent in droplets of a raw material liquid. Therefore, when ceramics are synthesized, metal ions are not unevenly distributed. Therefore, it is presumed that ceramic particles having a homogeneous and / or fine phase are synthesized.

(Ceramic powder)
The synthesized ceramic powder is collected by the dust collection unit 10 or the like in the synthesis apparatus 2 shown in FIG. The collected ceramic powder is easily crushed into particles. According to the present invention, by containing a chelating agent in the raw material liquid, the ceramic powder of the present invention containing composite ceramic particles that uniformly hold the phase of one or more metal oxides is obtained. be able to. The average particle diameter of the composite ceramic particles is preferably 2 μm or less. Furthermore, the average particle diameter of the individual metal oxide phases (particles) can be nano level, preferably 200 nm or less, more preferably 100 nm or less. In particular, it is possible to obtain a ceramic powder containing dispersed composite particles having two or more kinds of metal oxide phases having different sinterability and dispersed at the nano level. For example, a first phase containing one or more metal oxides selected from the group consisting of NiO, Co ₂ O ₃ and Fe ₂ O ₃ , and M _x Ce _1-x O _{(1-x) / 2} , dispersion having a second phase containing one or more metal oxides selected from the group consisting of Y ₂ O ₃ -added ZrO ₂ , Sc ₂ O ₃ -added ZrO ₂ and CaO-added ZrO ₂ Type composite particles can be obtained. A ceramic powder containing such composite ceramic particles is preferable as a fuel electrode material for SOFC.

  Moreover, as already explained, the ceramic particles in the ceramic powder of the present invention can take various forms corresponding to the degree of polymerization in the raw material liquid. Therefore, porous and spherical particles having two or more metal oxide phases can be obtained. In this case, the individual metal oxide phases can be present as individual primary particles. The average particle diameter of the composite ceramic particles is preferably 2 μm or less. The average particle diameter of the primary particles is at the nano level, preferably 200 nm or less, more preferably 100 nm or less. Moreover, it has a 2 or more types of metal oxide phase, and can also obtain the hollow spherical shape, outer-shell-like, or flake-like particle | grains. Also in such particles such as hollow spheres, the individual metal oxide phases preferably have an average particle diameter of 200 nm or less.

(SOFC and its manufacturing method)
By firing ceramic powder, which is a material for SOFC fuel electrodes, into a film, an SOFC fuel electrode and an SOFC including the fuel electrode can be manufactured. In the fuel electrode after operating the SOFC including the produced fuel electrode, the form of the dispersed composite particles disappears, and instead, a three-dimensional network structure is formed, and a good porous structure is formed. The three phase interface is increased. In addition, in order to form a fuel electrode using ceramic powder, the normal film-forming method performed using ceramic powder can be selected suitably, and can be used. The SOFC can be obtained as a laminate in which an electrolyte layer is sandwiched between such a fuel electrode and an air electrode obtained from a conventionally known air electrode material.

  As described above, according to the present invention, since the raw material liquid contains the chelating agent capable of chelating the metal cation forming the metal oxide, it is homogeneous from the liquid droplets of the raw material liquid by the nano-level metal oxide phase. It is possible to obtain ceramic particles constituted as follows. When the ceramic particles are composed of two or more metal oxide phases, the ceramic particles are dispersed composite particles. Thus, by using as a raw material ceramic powder having individual ceramic particles having a nano-level and / or homogeneous metal oxide phase, it is possible to obtain an unprecedented microstructured ceramic fired body. In addition, by configuring the SOFC fuel electrode, it is possible to obtain a fuel electrode having a fine porous structure that has not been conventionally provided and an increased three-phase interface as compared with the conventional one.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited at all by these Examples, unless the summary is exceeded.

(Synthesis of ceramic powder)
Cerium nitrate (Ce (NO ₃ ) ₃ ) and samarium oxide (Sm ₂ O ₃ ) are dissolved in concentrated nitric acid, then nickel acetate (Ni (NO ₃ ) ₂ ) is added, and ethylene glycol is added as a chelating agent to all metals. A 5-fold molar amount of the cation amount was added and mixed by stirring to prepare a raw material solution. This raw material liquid was heated at 80 ° C. for 8 hours to polymerize ethylene glycol to promote chelation. A ceramic powder was synthesized by applying 375 ml of water to 125 ml of the raw material liquid after polymerization and applying it to the synthesizer shown in FIG. The heating furnace unit 8 in the synthesizer 2 is an alumina tube having an inner diameter of 20 mm and a length of 1450 mm. The four heating furnaces 8a to 8d arranged in the length direction are 200 ° C., 400 ° C. and 800 ° C., respectively. The inside of the furnace is maintained at ℃ and 1000 ℃. The carrier gas (air) flow rate was 1.0 L / min. The collected powder was calcined in air at 1000 ° C. for 24 hours.

(Ceramic powder morphology and composition analysis)
The obtained synthetic ceramic powder was observed with a scanning electron microscope (SEM), and the ceramic particles were analyzed with a transmission electron microscope (TEM) and the composition thereof with an energy dispersive X-ray spectrometer (EDS). 2 shows SEM observation results, and FIGS. 3 and 4 show TEM observation results and EDS analysis results of ceramic particles and a part thereof, respectively.

  As shown in the SEM observation result of FIG. 2, porous and spherical particles having an average particle diameter of about 1 μm were obtained. Moreover, as shown in the TEM observation results of FIGS. 3 and 4, the ceramic particles are composed of composite particles in which primary particles having an average particle diameter of about 20 nm are aggregated. Further, from the EDS analysis results of FIGS. 3 and 4, it was found that the primary particles in which Ni is present are different from the primary particles in which Ce is present. Furthermore, as shown in FIG. 4, these primary particles were found to be nano-sized and fine and constituted a homogeneous mixed phase.

(Power generation characteristics of solid oxide fuel cells)
Using the obtained ceramic powder as a fuel electrode material of a solid oxide fuel cell, the power generation characteristics were investigated using hydrogen humidified at 3% as a fuel gas. To 1.5 g of powder, 0.8 g of polyethylene glycol as a binder and 1.5 g of ethanol as a dispersing agent are added and mixed in an alumina automatic mortar for about 20 minutes to evaporate ethanol, and then a LSGM plate having a thickness of 100 μm. On top of this, a screen (mesh # 200) was printed and baked at 1250 ° C. for 2 hours. The thickness of the fuel electrode was about 20 μm. Further, (La, Sr) CoO ₃ was used as the air electrode. Add 1.5g of polyethylene glycol as binder to 1.5g of powder and 1.5g of ethanol as dispersant, mix in alumina automatic mortar for about 20 minutes, evaporate ethanol, then backside of LSGM plate with fuel electrode baked A screen (mesh # 200) was printed on this, and baked at 1000 ° C. for 4 hours. The thickness of the air electrode was about 20 μm. 5 and 6 show the evaluation results of the power generation characteristics at 750 ° C. and 600 ° C. for this evaluation battery cell. Moreover, the SEM observation result of the interface of the fuel electrode and electrolyte after evaluation is shown in FIG.

As shown in FIG. 5, a maximum output density of 1.69 Wcm ⁻² was obtained at 750 ° C. This was a power generation characteristic that exceeded the maximum power density (1.11 Wcm ⁻² ) obtained in the conventional capsule composite particles by 50%. Further, as shown in FIG. 6, it was found that even at a low temperature of 600 ° C., 0.24 Wcm ⁻² showed excellent power generation characteristics. It was considered that this was because the produced fuel electrode used the dispersed composite particles as a raw material to obtain an electrode structure with an increased three-phase interface.

  Further, from the SEM observation result of the fuel electrode after the evaluation of the power generation characteristics in FIG. 7, it can be seen that a fine porous structure is formed by configuring the fuel electrode using ceramic powder having dispersed composite particles as a raw material. all right.

(Synthesis of ceramic powder)
Cerium nitrate (Ce (NO ₃ ) ₃ ) and samarium oxide (Sm ₂ O ₃ ) are dissolved in concentrated nitric acid, then nickel acetate (Ni (NO ₃ ) ₂ ) is added, and ethylene glycol is added as a chelating agent to all metals. A 0.25-fold molar amount, a 0.5-fold molar amount and a 1-fold molar amount of the cation amount were added and mixed by stirring to prepare a raw material solution. This raw material liquid was directly applied to the synthesis apparatus shown in FIG. 1 to synthesize ceramic powder. The heating furnace unit 8 in the synthesizer 2 was the same as that in Example 1. Moreover, the four heating furnaces 8a to 8d maintain the inside of the furnace at 200 ° C., 400 ° C., 800 ° C., and 1000 ° C., respectively. The carrier gas (air) flow rate was 1.0 L / min.

(Ceramic powder morphology and composition analysis)
While observing the obtained synthetic ceramic powder with a scanning electron microscope (SEM), the crystal phase was examined by X-ray diffraction for these synthetic ceramic powder and a sample calcined at 1000 ° C. for 24 hours in the air. The SEM observation result is shown in FIG. 8, and the X-ray diffraction spectrum is shown in FIG.

  As shown in the SEM observation results of FIG. 8, flaky particles such as hollow spheres to outer spheres of hollow spheres were obtained at any ethylene glycol addition amount. Moreover, as shown in FIG. 9, there was no change in the crystal phase before and after calcination, and both consisted of NiO and SDC. Therefore, it was found that there is no difference in crystal composition or generation of impurity phases due to differences in the amount of ethylene glycol added.

(Power generation characteristics of solid oxide fuel cells)
Using the obtained ceramic powder as a fuel electrode material of a solid oxide fuel cell, the power generation characteristics were investigated using hydrogen as a fuel gas. To 1.5 g of powder, 0.8 g of polyethylene glycol as a binder and 1.5 g of ethanol as a dispersing agent are added and mixed in an alumina automatic mortar for about 20 minutes to evaporate ethanol, and then a LSGM plate having a thickness of 100 μm. On top of this, a screen (mesh # 200) was printed and baked at 1250 ° C. for 2 hours. The thickness of the fuel electrode was about 20 μm. Further, (La, Sr) CoO ₃ was used as the air electrode. Add 1.5g of polyethylene glycol as binder to 1.5g of powder and 1.5g of ethanol as dispersant, mix in alumina automatic mortar for about 20 minutes, evaporate ethanol, then backside of LSGM plate with fuel electrode baked A screen (mesh # 200) was printed on this, and baked at 1000 ° C. for 4 hours. The thickness of the air electrode was about 20 μm. About this evaluation battery, the evaluation result of the electric power generation characteristic in 700 degreeC is shown to FIGS.

  As shown in FIGS. 10 to 12, by adding ethylene glycol and synthesizing, the polarization value ha of the fuel electrode is reduced, suggesting that the density of the three-phase interface in the fuel electrode is high.

The figure which shows the outline of a ceramics synthesis apparatus. The figure which shows the SEM observation result of the synthetic ceramic particle | grains of Example 1. FIG. The figure which shows the TEM observation result of the synthetic ceramic particle of Example 1, and an EDS analysis result. The figure which shows the TEM observation result of a part of synthetic ceramic particle | grains of Example 1, and an EDS analysis result. The figure (750 degreeC) which shows the electric power generation characteristic of SOFC provided with the fuel electrode which uses the synthetic ceramic powder of Example 1 as a raw material. The figure (600 degreeC) which shows the electric power generation characteristic of SOFC provided with the fuel electrode which uses the synthetic ceramic powder of Example 1 as a raw material. The figure which shows the SEM observation result of the interface of the fuel electrode which uses the synthetic ceramic powder of Example 1 as a raw material, and an electrolyte (after battery operation). The figure which shows the SEM observation result of the synthetic ceramic powder of Example 2 (addition amount of ethylene glycol; (a) 0.25 mol times amount, (b) 0.5 mol times amount, (c) 1.0 mol times amount ). The figure which shows the X-ray-diffraction spectrum before and behind calcination of the synthetic ceramic powder of Example 2 (addition amount of ethylene glycol, (a) 0.5 mol times amount, (b) 1.0 mol times amount). The figure which shows the electric power generation characteristic of OFC provided with the fuel electrode which uses the synthetic ceramic powder (addition amount of ethylene glycol: 0.25 mol times amount) of Example 2 as a raw material. The figure which shows the electric power generation characteristic of SOFC provided with the fuel electrode which uses the synthetic ceramic powder (addition amount of ethylene glycol: 0.5 mol times amount) of Example 2 as a raw material. The figure which shows the electric power generation characteristic of SOFC provided with the fuel electrode which uses the synthetic ceramic powder (addition amount of ethylene glycol: 1.0 mol times amount) of Example 2 as a raw material.

Explanation of symbols

  2 Ceramic synthesizer 4, droplet forming section, 6 connecting tube, 8 heating furnace unit, 8a, 8b, 8c, 8d heating furnace, 10 dust collecting section.

Claims (18)

A method for producing a ceramic powder containing one or more metal oxides,
A raw material liquid preparation step for preparing a raw material liquid containing a metal salt which is a metal salt constituting the metal oxide and a chelating agent having an electron donating group capable of chelating the metal cation and a polymerizable functional group When,
A synthesis process for synthesizing ceramics by heating the raw material liquid formed into droplets;
A manufacturing method comprising:   The chelating agent is one selected from the group consisting of ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and ethylene glycol oligomers. The manufacturing method of Claim 1 which is 2 or more types.   The manufacturing method according to claim 2, wherein the chelating agent is ethylene glycol.   The said chelating agent is a manufacturing method in any one of Claims 1-3 contained in the said raw material liquid by 0.2-10 in molar ratio with respect to the said metal cation.   The manufacturing method in any one of Claims 1-4 provided with the superposition | polymerization process of superposing | polymerizing at least one part of the said chelating agent in the said raw material liquid prior to the said synthetic | combination process.   The said superposition | polymerization process is a manufacturing method of Claim 5 which is a process of heating the said raw material liquid at the temperature of 70 to 130 degreeC.   The said synthesis | combination process is a process of synthesize | combining ceramics by allowing the said raw material liquid made into the droplet to pass through the heating furnace hold | maintained at high temperature toward the discharge part from the introduction part. The manufacturing method as described.   The said ceramic powder is a manufacturing method in any one of Claims 1-7 containing the composite ceramic particle provided by disperse | distributing the phase of 2 or more types of metal oxides. The ceramic powder is a material for an electrode of a solid oxide fuel cell,
The two or more types of the metal oxides include a metal oxide that is a conductive material of a solid oxide fuel cell and a metal oxide that is a material for a support of a solid oxide fuel cell. Manufacturing method.   A ceramic powder obtained by the production method according to claim 1. Ceramic powder,
A ceramic powder containing composite ceramic particles having dispersed phases of two or more metal oxides having different sinterability. The phase of the two or more metal oxides is
A first phase comprising one or more metal oxides selected from the group consisting of NiO, Co ₂ O ₃ and Fe ₂ O ₃ ;
M _x Ce _1-x O _{(1-x) / 2} (where M is selected from Gd, Sm and La, and 0.1 ≦ x ≦ 0.8), Y ₂ O ₃ added ZrO ₂ a second phase comprising _Sc 2 _{O 3} 1 or additives are selected from the group consisting of ZrO ₂ and CaO added ZrO ₂ or more metal oxides,
Ceramic powder.   The ceramic powder according to claim 11 or 12, wherein the composite particles are porous spherical bodies.   The ceramic powder according to claim 11 or 12, wherein the composite particles are flaky.   The ceramic powder according to claim 11, wherein the composite ceramic particles have an average particle size of 2 μm or less.   The ceramic powder according to any one of claims 11 to 15, which is a material for an electrode of a solid oxide fuel cell. A method for producing a solid oxide fuel cell, comprising:
A manufacturing method provided with the process of forming a fuel electrode using the ceramic powder in any one of Claims 11-15 as a raw material. A solid oxide fuel cell,
A solid oxide fuel cell comprising a fuel electrode made from the ceramic powder according to claim 11.