WO2023038018A1 - ペロブスカイト型複合酸化物粉末並びにそれを用いた固体酸化物型燃料電池用の空気極及び固体酸化物型燃料電池 - Google Patents
ペロブスカイト型複合酸化物粉末並びにそれを用いた固体酸化物型燃料電池用の空気極及び固体酸化物型燃料電池 Download PDFInfo
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- WO2023038018A1 WO2023038018A1 PCT/JP2022/033357 JP2022033357W WO2023038018A1 WO 2023038018 A1 WO2023038018 A1 WO 2023038018A1 JP 2022033357 W JP2022033357 W JP 2022033357W WO 2023038018 A1 WO2023038018 A1 WO 2023038018A1
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- composite oxide
- oxide powder
- perovskite
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- type composite
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- 239000000843 powder Substances 0.000 title claims abstract description 157
- 239000002131 composite material Substances 0.000 title claims abstract description 115
- 239000000446 fuel Substances 0.000 title claims description 33
- 239000007787 solid Substances 0.000 title claims description 26
- 238000010191 image analysis Methods 0.000 claims abstract description 20
- 238000001878 scanning electron micrograph Methods 0.000 claims abstract description 13
- 239000002245 particle Substances 0.000 claims description 120
- 239000000203 mixture Substances 0.000 claims description 20
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 13
- 229910052746 lanthanum Inorganic materials 0.000 claims description 12
- 238000009826 distribution Methods 0.000 claims description 10
- 239000007784 solid electrolyte Substances 0.000 claims description 10
- 229910052712 strontium Inorganic materials 0.000 claims description 10
- 239000011575 calcium Substances 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- 229910052791 calcium Inorganic materials 0.000 claims description 6
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 229910017052 cobalt Inorganic materials 0.000 claims description 4
- 239000010941 cobalt Substances 0.000 claims description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 4
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 2
- 239000007772 electrode material Substances 0.000 abstract description 5
- 239000002994 raw material Substances 0.000 description 52
- 239000002002 slurry Substances 0.000 description 45
- 238000005259 measurement Methods 0.000 description 25
- 238000000034 method Methods 0.000 description 22
- 239000011324 bead Substances 0.000 description 21
- 238000010304 firing Methods 0.000 description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- 239000007789 gas Substances 0.000 description 18
- 239000002270 dispersing agent Substances 0.000 description 14
- 238000001035 drying Methods 0.000 description 14
- 238000010298 pulverizing process Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000004458 analytical method Methods 0.000 description 10
- 239000013078 crystal Substances 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- 238000010248 power generation Methods 0.000 description 9
- 230000000704 physical effect Effects 0.000 description 7
- 239000007921 spray Substances 0.000 description 7
- 238000001694 spray drying Methods 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 6
- 230000001133 acceleration Effects 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 6
- 239000011572 manganese Substances 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 5
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 239000008188 pellet Substances 0.000 description 5
- 229920000058 polyacrylate Polymers 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 239000012528 membrane Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- -1 organic acid salts Chemical class 0.000 description 4
- 238000012856 packing Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 101100513612 Microdochium nivale MnCO gene Proteins 0.000 description 3
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 3
- 235000013339 cereals Nutrition 0.000 description 3
- 238000009694 cold isostatic pressing Methods 0.000 description 3
- 238000001218 confocal laser scanning microscopy Methods 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 230000001186 cumulative effect Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 239000002737 fuel gas Substances 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 150000004679 hydroxides Chemical class 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 150000002823 nitrates Chemical class 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 238000010008 shearing Methods 0.000 description 3
- 206010021143 Hypoxia Diseases 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 235000010216 calcium carbonate Nutrition 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000001804 emulsifying effect Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 239000011361 granulated particle Substances 0.000 description 2
- 238000005469 granulation Methods 0.000 description 2
- 230000003179 granulation Effects 0.000 description 2
- 238000009499 grossing Methods 0.000 description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000012798 spherical particle Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- LEDMRZGFZIAGGB-UHFFFAOYSA-L strontium carbonate Chemical compound [Sr+2].[O-]C([O-])=O LEDMRZGFZIAGGB-UHFFFAOYSA-L 0.000 description 2
- 229910000018 strontium carbonate Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910003024 (La,Sr) (Co,Fe)O3-δ Inorganic materials 0.000 description 1
- 229910003029 (La,Sr)CoO3−δ Inorganic materials 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910002127 La0.6Sr0.4Co0.2Fe0.8O3 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical group [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 102100025490 Slit homolog 1 protein Human genes 0.000 description 1
- 101710123186 Slit homolog 1 protein Proteins 0.000 description 1
- 102100027340 Slit homolog 2 protein Human genes 0.000 description 1
- 101710133576 Slit homolog 2 protein Proteins 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- ZJRWDIJRKKXMNW-UHFFFAOYSA-N carbonic acid;cobalt Chemical compound [Co].OC(O)=O ZJRWDIJRKKXMNW-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 229910000001 cobalt(II) carbonate Inorganic materials 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000002001 electrolyte material Substances 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000005453 pelletization Methods 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 235000011121 sodium hydroxide Nutrition 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000003826 uniaxial pressing Methods 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G45/00—Compounds of manganese
- C01G45/12—Manganates manganites or permanganates
- C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
- C01G45/125—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type[MnO3]n-, e.g. Li2MnO3, Li2[MxMn1-xO3], (La,Sr)MnO3
- C01G45/1264—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type[MnO3]n-, e.g. Li2MnO3, Li2[MxMn1-xO3], (La,Sr)MnO3 containing rare earth, e.g. La1-xCaxMnO3, LaMnO3
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G45/00—Compounds of manganese
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/40—Nickelates
- C01G53/70—Nickelates containing rare earth, e.g. LaNiO3
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M12/00—Hybrid cells; Manufacture thereof
- H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
- H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/8605—Porous electrodes
- H01M4/8621—Porous electrodes containing only metallic or ceramic material, e.g. made by sintering or sputtering
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/88—Processes of manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M2008/1293—Fuel cells with solid oxide electrolytes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a perovskite-type composite oxide powder and the like, and more particularly suitable as a material for air electrodes of solid oxide fuel cells (SOFC: Solid Oxide Fuel Cell, hereinafter sometimes simply referred to as "SOFC”).
- SOFC Solid Oxide Fuel Cell
- the present invention relates to a perovskite-type composite oxide powder (hereinafter sometimes simply referred to as "composite oxide powder") used for
- a fuel cell is an energy converter that can directly obtain electrical energy from chemical energy by reacting fuel such as natural gas or hydrogen with oxygen in the air through a diaphragm that allows ions to pass. Since the fuel cell itself generates only energy and water, attention has been paid to it as a power generation device from a small size to a large size.
- Solid electrolyte type Solid electrolyte type
- molten carbonate type molten carbonate type
- phosphate type solid oxide type
- solid oxide type solid oxide type
- SOFC solid oxide fuel cell
- the solid oxide fuel cell (SOFC) has a high operating temperature of about 700 to 1000°C, but it is characterized by being able to increase the power generation efficiency by combining it with a fuel reformer. and does not require expensive catalytic metals, it is considered to be a particularly promising form.
- the quality of the air electrode has a large impact on the power generation efficiency of the SOFC.
- Characteristics required for the air electrode of SOFC include chemical stability, gas passage efficiency, material conductivity, and the like.
- the air electrode material has a main phase composed of a perovskite-type composite oxide having a specific composition and another composition.
- a cathode material containing a subphase composed of a perovskite-type composite oxide has been proposed.
- Patent Document 2 of the present applicant spherical particles having a high roundness (circularity) are used as a material for the air electrode for the purpose of providing an air electrode for SOFC with high air permeability.
- Oxide powders have been proposed.
- the problem to be solved by the present invention is to improve the conductivity of the air electrode of the SOFC more than before.
- the present inventors investigated the shape factor that affects the conductivity of the SOFC air electrode, and found that the maximum Feret diameter of the composite oxide powder affects the conductivity of the SOFC air electrode. and completed the present invention.
- the geometric standard deviation of the maximum Feret diameter of the perovskite-type composite oxide powder is calculated by image analysis of an SEM image obtained using a scanning electron microscope.
- value is 1.01 or more and less than 1.60
- the area value A calculated from the maximum Feret diameter on the assumption that the perovskite-type composite oxide powder is spherical
- the ratio (B/A) to B is 0.7 or more and less than 1.0.
- the perovskite-type composite oxide powder according to one aspect of the second invention has the general formula ABO 3- ⁇ (A element is at least one selected from lanthanum, strontium, and calcium, and B element is manganese, cobalt, nickel, and iron. At least one selected, ⁇ indicates the amount of oxygen deficiency).
- the perovskite-type composite oxide powder according to an aspect of the third invention contains lanthanum as an essential component as the A element.
- the circularity of the perovskite-type composite oxide powder calculated by image analysis of an SEM image obtained using a scanning electron microscope is 0.70 or more. less than 1.0.
- the perovskite-type composite oxide powder according to one aspect of the fifth invention has a BET specific surface area of 0.01 m 2 /g or more and 0.5 m 2 /g or less.
- the perovskite-type composite oxide powder according to an aspect of the sixth invention has a volume-based average particle diameter D50 of 10 ⁇ m or more and 50 ⁇ m or less obtained by a laser diffraction particle size distribution analyzer.
- An air electrode for a solid oxide fuel cell according to an aspect of the seventh invention comprises any one of the perovskite-type composite oxide powders described above.
- a solid oxide fuel cell according to an aspect of the eighth invention is a solid oxide fuel cell comprising a fuel electrode, a solid electrolyte, and an air electrode, wherein the air electrode is the air electrode described above. It is characterized by using
- the Feret diameter is the size of a rectangle circumscribing a binary image measurement target (horizontal direction is the length of the side parallel to the X-axis, and vertical direction is the length of the side parallel to the Y-axis. , the maximum Feret diameter is the longer value in the horizontal or vertical direction (see FIG. 1).
- perovskite-type composite oxide powder means an aggregate of particles.
- “-” shown in this specification is used to include the numerical values before and after it as lower and upper limits.
- the SOFC air electrode using the perovskite-type composite oxide powder according to the present invention can ensure better conductivity.
- FIG. 3 is a diagram for explaining the Feret diameter and the like of a perovskite-type composite oxide powder; 1 is a cross-sectional configuration diagram schematically showing an example of an SOFC; FIG.
- One of the major characteristics of the perovskite-type composite oxide powder according to the present invention is that the geometric standard of the maximum Feret diameter of the perovskite-type composite oxide powder calculated by image analysis of the SEM image obtained using a scanning electron microscope is The deviation value is 1.01 or more and less than 1.60.
- the geometric standard deviation is widely used as an indicator of the uniformity of the distribution when the distribution has a tail on the coarse grain side.
- the composite oxide powder has a shape as close to a sphere as possible.
- the geometric standard deviation of the maximum Feret diameter of the composite oxide powder is set to 1.01 or more and less than 1.60.
- a more preferable range of the geometric standard deviation of the maximum Feret diameter is 1.10 or more and less than 1.60, and a further preferable range is 1.20 or more and less than 1.60.
- the geometric standard deviation of the maximum Feret diameter of the composite oxide powder is calculated by converting the measured values into common logarithms and then converting the standard deviations into antilogarithms.
- the measured value of the maximum Feret diameter was calculated using a mechanical method described later.
- Another major feature of the composite oxide powder according to the present invention is the area value A of the particles, which is calculated from the maximum Feret diameter assuming that the composite oxide powder is spherical, and the area value A, which is directly calculated by image analysis.
- the ratio (B/A) to the area value B of the particles is 0.7 or more and less than 1.0.
- the area value A represents the area of the circumscribed circle of the particle, the closer the value of the ratio (B/A) to 1, the smaller the unevenness of the particle and the closer the particle shape is to a sphere.
- the area of the circle indicated by the dashed line is the area value A ((maximum Feret diameter/2) 2 ⁇ ⁇ )
- the area directly calculated by image analysis of the colored particles is the area value B is.
- the Feret diameter the value calculated by the software was used as it was in order to eliminate artificial factors.
- the area value ratio (B/A) is obtained by calculating the area value ratio (B/A) from the measurement data (area value B) and the calculated data (area value A) for each particle, and obtaining at least The average of 50 particles was obtained and used as a ratio of area values.
- the particles of the composite oxide powder constituting the air electrode are spherical, the particles are uniformly present in a form of close packing, and pores are uniformly formed between the particles, and the flow of oxygen is made uniform. A large number of three-layer interfaces where the electrodes, the electrolyte, and the gas phase are in contact with each other are efficiently formed, increasing power generation efficiency.
- the shape of the particles constituting the air electrode is not spherical, for example, a rectangular parallelepiped, depending on how the particles contact each other, there will be a portion with no voids and a portion with excessively large voids. It is formed. As a result, the flow of oxygen becomes non-uniform, and the number of three-phase interfaces decreases, resulting in a decrease in power generation efficiency.
- composition of the perovskite-type composite oxide powder according to the present invention is represented by the general formula ABO 3- ⁇ (A element is at least one selected from lanthanum (La), strontium (Sr), and calcium (Ca), and B element is manganese ( Mn), at least one selected from cobalt (Co), nickel (Ni), and iron (Fe), and ⁇ indicates the amount of oxygen deficiency).
- a composition containing La as the A element is more preferable.
- (La, Sr, Ca) MnO 3- ⁇ -based composite oxide powder containing La, Sr, Ca, Mn (hereinafter sometimes referred to as “LSCM”), La, Sr, (La, Sr) (Co, Fe) O 3- ⁇ -based composite oxide powder containing Co ⁇ Fe (hereinafter sometimes referred to as “LSCF”), containing La ⁇ Sr ⁇ Co (La, Sr) CoO 3- ⁇ -based composite oxide powder (hereinafter sometimes referred to as “LSC”), (La, Sr)MnO 3- ⁇ - based composite oxide powder containing La, Sr, and Mn (hereinafter, “LSM” ), and La(Ni, Co)O 3- ⁇ - based composite oxide powder (hereinafter sometimes referred to as “LNC”).
- LSC La ⁇ Sr ⁇ Co (La, Sr) CoO 3- ⁇ -based composite oxide powder
- LNC La(Ni, Co)O 3- ⁇ - based composite oxide powder
- composite oxide powders have electronic conductivity, for example, adsorbents, catalyst carriers, separation membranes, oxygen electrodes of fuel cells, electrodes of capacitors, functional filter members, gas sensors, lithium It can be used as an electricity storage device, a dye-sensitized solar cell, and the like.
- LSCM is (La 1-x-y Sr x Ca y ) a MnO 3- ⁇ (where 0.1 ⁇ x ⁇ 0.5, 0.1 ⁇ y ⁇ 0.5, 0.9 ⁇ a ⁇ 1.1)
- LSCF is (La 1-x Sr x ) a Co y Fe 1-y O 3- ⁇ (where 0.1 ⁇ x ⁇ 0.5, 0.1 ⁇ y ⁇ 0 .5, 0.9 ⁇ a ⁇ 1.1)
- LCN is La a Co x Ni 1-x O 3- ⁇ (where 0.1 ⁇ x ⁇ 1.0, 0.9 ⁇ a ⁇ 1.0). 1).
- the composition of oxygen is stoichiometrically 3, it may be partially deficient or may be present in excess.
- the composite oxide according to the present invention may have a perovskite structure as a main component in the crystal structure confirmed by X-ray diffraction. It may be present as long as it does not give.
- the composite oxide powder according to the present invention is preferably particles having a circularity calculated from the following formula of less than 1.0, preferably 0.95 or less, and more preferably 0.90 or less.
- the circularity shows a smaller value as the particles are more complicated, and the lower limit is preferably 0.7 or more in order to obtain the effect of the present invention.
- the geometric standard deviation value of the maximum Feret diameter of the composite oxide powder and the circularity are both factors that affect the power generation performance of the SOFC. If the geometric standard deviation of the maximum Feret diameter and the degree of circularity are within specific ranges, it becomes possible to provide a more preferable SOFC. That is, the geometric standard deviation of the maximum Feret diameter is in the range of 1.01 or more and less than 1.60, the circularity is 0.70 or more and 0.95 or less, preferably the geometric standard deviation of the maximum Feret diameter is more than 1.30. If the circularity is 0.75 or more and 0.95 or less in the range of less than 1.60, the packing between the particles becomes dense, and the three-phase interface that affects the power generation performance can also be suitably formed. This is preferable because it improves performance.
- the BET specific surface area of the composite oxide powder according to the present embodiment is a value measured by the BET one-point method by nitrogen adsorption using a BET specific surface area measuring device (Macsorb (registered trademark) HM model-1210 manufactured by Mountec Co., Ltd.). be.
- the BET specific surface area of the composite oxide powder is preferably 0.01 m 2 /g or more and 0.5 m 2 /g or less. It is more preferably 0.3 m 2 /g or less, still more preferably 0.2 m 2 /g or less. If the BET specific surface area becomes too high, it becomes difficult to adjust the viscosity, which is not preferable.
- the average particle size of the composite oxide powder according to the present embodiment is the value of the volume-based cumulative 50% particle size (D 50 ) measured with a wet laser diffraction scattering particle size distribution analyzer.
- the average particle diameter D50 of the composite oxide powder is preferably 10 ⁇ m or more and 50 ⁇ m or less. It is more preferably 15 ⁇ m or more and 45 ⁇ m or less, and still more preferably 20 ⁇ m or more and 40 ⁇ m or less.
- the particle size distribution measurement using the above-described measuring apparatus measures the dispersion of particles that approximate a spherical shape, and it is possible to know the three-dimensional dispersion of the particle size.
- the coefficient of variation of the particle size distribution calculated by the above-described measuring device is 75% or less, preferably 70% or less, and more preferably 60% or less.
- a known classification method such as a sieve can be used to adjust the particle size distribution to a specific range.
- the geometric standard deviation value of the maximum Feret diameter of the composite oxide powder, the area value A, the area value B, and the perimeter of the particle are analyzed and evaluated as follows. Scanning electron microscope (SEM) images taken in advance are analyzed and evaluated using image analysis software (such as Image-Pro Plus manufactured by Media Cybernetics, USA). A commercially available scanning electron microscope (SEM) can be appropriately selected for measurement, and the measurement magnification is not particularly limited as long as the shape of the particles can be confirmed. In this specification, a Schottky field emission scanning electron microscope (JSM-7200F type) manufactured by JEOL Ltd. was used.
- JSM-7200F type Schottky field emission scanning electron microscope
- the acceleration voltage since it is necessary to confirm the surface state, it is preferable that the acceleration voltage is low, and is preferably 10 kV or less.
- the photographing was performed under the conditions of an acceleration voltage of 3.0 kV, an acceleration current of 10 ⁇ A, a WD (Working Distance) of 12 mm, and an SE Detector of Mix. SEM images were displayed with micron bars and the background was set to black and saved. It is preferable to set the resolution of the SEM image to 1280 ⁇ 960 (pixels) or more, because sufficient analysis accuracy can be obtained when image analysis is performed. On the other hand, if the resolution is too high, it will take too much time to analyze the image, so it is preferable to set the value to around 1280 ⁇ 960 (pixels) in terms of image analysis time.
- the particles can be selected arbitrarily, but if the particles are sintered or the like, it is assumed that they will behave as one, so they can be measured as one particle. If a part of the particles is arbitrarily present outside the field of view, it is difficult to confirm the shape of the particles, so it is excluded from the evaluation.
- the number of particles to be measured must be 50 or more independent particles.
- Image analysis is performed using the following method.
- the maximum Feret diameter is calculated for 50 or more particles from image analysis in the field of view.
- the maximum Feret diameter is automatically calculated by image analysis software, because it is possible to avoid human error in measurement.
- Feret diameters in the vertical and parallel directions are calculated. Comparing the parallel direction and the perpendicular direction here, the Feret diameter in the parallel direction is longer, so if the particles have the shape shown here, the maximum Feret diameter is the Feret diameter in the parallel direction.
- Such an operation is performed for each particle, and the maximum Feret diameter of each particle is measured.
- a geometric standard deviation value is calculated from the value of the maximum Feret diameter of the particles thus obtained.
- the numerical conversion of the maximum Feret diameter to the logarithm and the calculation of the geometric standard deviation can be performed using commercially available spreadsheet software.
- the obtained images were analyzed using image analysis software Image Pro Plus Ver. 7.0.1 was used. Specific analysis examples include the following conditions. First, software automatically counts the number of particles in an image that has been taken in advance. At this time, if the particle extraction is not successful due to the contrast or the like, it is preferable to automatically adjust the contrast and analyze it as an appropriate brightness.
- the image acquired from the SEM has depth in the thickness direction, particles that are not suitable for evaluation in the thickness direction and particles that do not enter the acquisition range (particles whose entire image cannot be confirmed) are also observed. be. If it is an image taken by SEM, the image taken is the one in the vertical direction of the particle, so by binarizing the image, it is possible to accurately grasp the outer shape of the particle itself. preferable. In the binarization, the particles to be measured are arbitrarily selected. Particles on the edges of the top, bottom, left, and right windows are automatically excluded from measurement by automatically excluding particles on the edges of the captured image (exclude on the border).
- the photographed particle has a dent, or if the image is three-dimensional and the particles overlap, particles that exist at the bottom in the thickness direction (those that are evaluated as small) will be evaluated.
- the setting to calculate the entire area closed by the particle boundary fill the hole
- the number of points for smoothing was unified to 12, and 4 connections were selected as the condition for recognizing grain boundaries.
- a predetermined area value 50 pixels or less was set to eliminate dust mixed in during photography.
- the option to combine and separate particles is not used because it is an obstacle to grasp the state of particles.
- the composite oxide powder according to the present invention is produced through the following steps. In addition, it is possible to omit the "process of drying and granulating the raw material" of the process (b).
- Predetermined component raw materials are weighed so as to produce a composite oxide powder having a perovskite structure with a desired composition.
- the raw materials for the components those commonly used can be suitably used. Examples thereof include oxides containing La, Sr, Ca, Mn, Co, Ni and Fe, hydroxides, nitrates, carbonates, nitrates and organic acid salts. Of these, carbonates, hydroxides or oxides are particularly preferred for reasons of environmental considerations and availability.
- any two or more kinds of compounds selected from carbonates, oxides, hydroxides, nitrates, etc. can be selected as element sources for each element.
- the component raw material is preferably a water-insoluble salt.
- the impurities in each raw material salt should be 100 ppm or less by weight.
- a raw material slurry is obtained by mixing a predetermined amount of each component raw material with pure water.
- the raw material slurry preferably has a solid content concentration of 25% by mass or more.
- the solid content concentration of the raw material slurry is preferably 40% by mass or more.
- the dispersant ammonium polyacrylate or the like is preferably used.
- a bead mill is preferably used for wet pulverization.
- the material of the grinding media used in the bead mill is not particularly limited as long as it has high mechanical strength. From the viewpoint of obtaining desired grinding efficiency, the diameter of the grinding media (beads) is preferably 2.0 mm or less.
- the raw material slurry is pulverized by a bead mill and then dispersed to obtain a highly uniform slurry.
- a preliminary step it is necessary to separate and collect the beads used in the bead mill from the slurry.
- a method of separating and recovering the beads by passing the slurry through a sieve having a mesh size of 3/4 or less of the bead diameter is preferred.
- the solid content adheres to the mesh of the sieve and clogs the sieve, resulting in poor separation and recovery efficiency, which is not suitable.
- a method for dispersing the raw material slurry a known method can be employed, but a method of dispersing by applying a shearing force is preferable. For example, a method of dispersing using a high-speed shearing type dispersing machine can be mentioned.
- the high-speed shearing disperser for example, a dissolver type, a rotor-stator type, a colloid mill type, or a thin film orbital type is used, and among these, the rotor-stator type disperser is more preferably used.
- the number of revolutions is preferably 10,000 rpm or less, more preferably 8,000 rpm or less, for a small volume scale of about 5 L. When processing with a volume larger than this, the number of revolutions may be appropriately determined in consideration of the scale factor.
- the homogeneity in the raw material slurry is increased, and a more uniform dried product can be obtained during spray drying. As a result, a more homogeneous composite oxide powder can be obtained.
- the raw material slurry after wet pulverization is dried and granulated.
- Spray drying is suitable for drying the raw material slurry and granulating it into spherical granules.
- a spray dryer is preferably used for the spray drying from the viewpoint of obtaining spherical granulated powder.
- Spray dryers include a nozzle type and a disk type, and the disk type is preferable for obtaining spherical particles having a large particle size.
- the number of revolutions of the atomizer disc depends on the speed at which the raw material slurry is supplied, the air flow rate of the dryer, and the chamber capacity.
- the temperature of the hot air for drying is desirably a temperature at which moisture does not remain in the granulated particles after spray drying. Specifically, it is desirable that the inlet temperature is 150 to 200°C and the outlet temperature is 60°C or higher.
- the feed rate of the raw material slurry is, for example, 5 to 30 kg/h in the case of a device with a drying chamber capacity of about 1 m 3 because the shape of the granulated particles can be maintained and the productivity can be secured. is preferred.
- the solid content concentration in the slurry is preferably in the range of 30-90%, more preferably in the range of 35-85%, and even more preferably in the range of 40-80%.
- the obtained granulated powder is dried using a dryer until the water content in the granulated powder is less than 5.0% by mass.
- the geometric standard deviation value of the maximum Feret diameter can be in the range of 1.01 or more and less than 1.60, and the circularity can be 0.70 or more and 0.95 or less.
- the water content of the granulated powder is preferably 4.5% by mass or less, more preferably 4.0% by mass or less.
- the moisture content of the granulated powder can be measured using an infrared moisture meter. Drying using a dryer is preferably carried out at 90°C to 150°C.
- the dried granulated powder is fired in a firing furnace.
- a conventionally known one such as an electric or gas shuttle kiln, roller hearth kiln, or rotary kiln can be used as a heat source.
- the firing temperature is desirably in the range of 850° C. or higher and 1600° C. or lower from the viewpoint of increasing the filling rate inside the particles constituting the composite oxide powder and increasing the electrical conductivity of the particles.
- the firing temperature is preferably 900° C. or higher from the viewpoint of increasing the electrical conductivity of the composite oxide powder.
- the firing temperature is preferably 1500° C. or less, and a firing temperature of 1400° C. or less is more preferable because the shape of the particles becomes uniform.
- the BET specific surface area can be adjusted to a desired value by adjusting the firing temperature.
- the heating rate in the firing process is preferably 10°C/min or less.
- the firing atmosphere is preferably the air or a gas containing 20% by volume or less of oxygen and the balance of nitrogen. It is preferable that the inside of the firing furnace or the inside of the firing vessel be an open system, and the temperature be raised while removing the gas component generated from the raw material salt of the component raw material.
- the amount of gas generated during the temperature rising stage is greater than in other processes, and by quickly removing the gas generated during the temperature rising stage, the grains grow while the spherical shape is broken or the grain surface is uneven. This is because it is possible to reduce the number of irregularly shaped particles.
- the method of removing the gas component generated from the raw material salt of the component raw material is not limited, but examples include a method of blowing in a gas having the same composition (especially the same oxygen concentration) as the firing atmosphere to quickly replace it. .
- a gas having the same composition especially the same oxygen concentration
- the wind speed of the blown gas is too strong, the granulated powder will collapse or dust will be generated, which is not preferable.
- open system refers to a reaction system in which the inside of the firing furnace or the firing container is not sealed, and gas, which is the firing atmosphere, can flow in and out.
- a step of heat-treating the fired powder in the presence of carbon dioxide can be arbitrarily added, for example, by the method described in Patent Document 3.
- the sintered powder is pulverized to obtain a composite oxide powder.
- a sample mill, a Henschel mixer, a pin mill, or the like can be used for pulverization, and pulverization is performed under conditions that do not impair the spherical shape of the particles.
- the rotation speed is 2500 rpm or less, preferably 2000 rpm. This is because if the number of revolutions is 2500 rpm or less, there is no risk of damaging the spherical shape of the particles.
- the volume is changed, the number of revolutions is appropriately adjusted so as not to impair the spherical shape of the particles.
- the composite oxide powder obtained through the above steps has a volume-based cumulative 50% particle diameter (D 50 ) of 10 ⁇ m to 50 ⁇ m, preferably 10 ⁇ m to 50 ⁇ m, as measured by a wet laser diffraction particle size distribution device (e.g., Microtrac). is preferably in the range 15 ⁇ m to 45 ⁇ m, more preferably 20 ⁇ m to 40 ⁇ m.
- D 50 volume-based cumulative 50% particle diameter
- the composite oxide powder according to the present invention is suitably used as an air electrode for SOFC.
- the SOFC air electrode is produced, for example, by forming the composite oxide powder according to the present invention into a compact and sintering the compact.
- a means for forming a sintered body from the composite oxide powder a means known per se is applied. For example, first, the composite oxide powder is mixed with a binder and filled into a mold having a certain volume. Then, a compact of the composite oxide powder is produced by applying pressure from above. The method of applying pressure is not particularly limited, such as mechanical uniaxial pressing and cold isostatic (CIP) pressing. Next, the produced molded body is heat-treated to obtain a sintered body.
- the heat treatment temperature is preferably in the range of 1000° C. or higher and 1450° C. or lower. When the heat treatment temperature is 1000° C. or higher, the mechanical strength of the molded body is sufficiently maintained, and when the heat treatment temperature is 1450° C.
- the heat treatment time is preferably 2 hours or more and 24 hours or less.
- FIG. 2 is a cross-sectional configuration diagram schematically showing an example of SOFC.
- the SOFC comprises a thin plate-like or sheet-like fuel electrode 1 serving as a support, a solid electrolyte membrane 2 formed on the surface of the fuel electrode 1, and a thin plate-like or sheet-like air layer formed on the surface of the solid electrolyte membrane 2. It has a structure in which the poles 3 are laminated.
- Fuel gas (typically hydrogen (H 2 ), but may be hydrocarbon (methane (CH 4 )) or the like) is supplied to the fuel electrode 1, and the air electrode 3 contains oxygen (O 2 ).
- oxygen oxygen in the air becomes oxide ions at the air electrode 3 .
- Oxide ions are supplied from the air electrode 3 to the fuel electrode 1 via the solid electrolyte 2 .
- water H 2 O is generated by reacting with the fuel gas, electrons are emitted, and power generation is performed.
- the SOFC is prepared, for example, by prefabricating a laminate of a fuel electrode, a solid electrolyte membrane, etc., and including an air electrode material on the laminate by a printing method or the like. By forming layers, the air electrode 3 is formed, and a fuel cell is produced.
- the film thickness of the air electrode 3 may be appropriately determined according to the structure of the cells constituting the SOFC, and is preferably 20 ⁇ m or more and 50 ⁇ m or less, for example.
- the electrolyte material used for the material of the air electrode can be used.
- examples thereof include a rare earth element-doped ceria-based solid oxide electrolyte and a rare earth element-doped zirconia-based solid oxide electrolyte.
- the film thickness of the solid electrolyte layer 2 is made thick enough to maintain the denseness of the solid electrolyte layer, while being thin enough to provide the conductivity of oxygen ions or hydrogen ions, which is preferable for the SOFC. 0.1 ⁇ m or more and 50 ⁇ m or less is preferable, and 1 ⁇ m or more and 20 ⁇ m or less is more preferable.
- the fuel electrode 1 only needs to have a porous structure and be configured so as to be able to come into contact with the supplied fuel gas.
- a material for the fuel electrode 1 a material that has been conventionally used for SOFC can be used.
- the film thickness of the fuel electrode 1 is preferably 20 ⁇ m or more and 1 mm or less, more preferably 20 ⁇ m or more and 250 ⁇ m or less, in terms of durability, coefficient of thermal expansion, and the like.
- the structure of the SOFC can be a conventionally known flat type, polygonal type, cylindrical type, or a flat cylindrical type in which the peripheral side surface of a cylinder is vertically crushed, and the shape and size are not particularly limited.
- planar SOFCs include, for example, an electrolyte-supported type (ESC) with a thick electrolyte and a cathode-supported type (CSC) with a thick air electrode.
- ESC electrolyte-supported type
- CSC cathode-supported type
- MSC metal support cell
- a porous metal sheet is put under the fuel electrode can also be used.
- Example 1 Preparation of Raw Material Slurry ⁇ 1> 3192 g of La2O3 , 1417 g of SrCO3 and CaCO3 were added so as to have a composition of La0.49Sr0.24Ca0.25Mn1.03O3 . Weigh 960 g, 4612 g of MnCO 3 , 4100 g of pure water, and 500 g of ammonium polyacrylate dispersant. ⁇ 2> 3100 g of ZrO 2 beads with a diameter of 1.75 mm are placed in a vessel of a bead mill (capacity: 1.2 liters). ⁇ 3> Pure water and a dispersant are put into a buffer tank and mixed to form an aqueous dispersant solution.
- the dispersant aqueous solution is circulated through the bead mill using a pump.
- La 2 O 3 , SrCO 3 , CaCO 3 and MnCO 3 weighed as described above are added to the aqueous dispersant solution in the buffer tank while stirring at 400 rpm.
- Homo Mixer Mark II manufactured by Primix Co., Ltd.
- X-ray diffraction measurement X-ray diffraction measurement
- Ultima IV manufactured by Rigaku Corporation.
- the measurement conditions were as follows: Cu tube, tube voltage 40 kV, tube current 40 mA, divergence slit 1/2°, scattering slit 8 mm, light receiving slit open, step width 0.02°, measurement time The setting was 4°/min.
- the analysis software attached to the X-ray diffraction (XRD) device ICDS (Inorganic Crystal Structure Database) for integrated powder X-ray analysis software PDXL2 manufactured by Rigaku Co., Ltd.
- composite oxide Identify the crystal phase of the powder and analyze the composition of the impurity components.
- the crystalline phase it is suitable for the crystalline phase to be a single phase, but if it is small (the intensity ratio of the main peak of the heterophase/perovskite phase is less than 10%), it is acceptable. However, in the case where the conductivity is lowered due to the presence of these different phases, the presence of these different phases should be reduced as much as possible.
- the geometric standard deviation value of the maximum Feret diameter of the composite oxide powder, the area value A, the area value B, the perimeter of the particle, and the circularity were analyzed and evaluated as follows. Scanning electron microscope (SEM) images taken were analyzed and evaluated using image analysis software (such as Image-Pro Plus manufactured by Media Cybernetics, USA). As a scanning electron microscope (SEM), a Schottky field emission scanning electron microscope (JSM-7200F type) manufactured by JEOL Ltd. was used. The image was taken under the conditions of an acceleration voltage of 3.0 kV, an acceleration current of 10 ⁇ A, a WD (working distance) of 12 mm, and an SE detector of Mix. The magnification of the photograph used for calculating the particle size was 1000 times. SEM images were displayed with micron bars and the background was set to black and saved. The SEM image resolution was set to 1280 ⁇ 960 (pixels) or more.
- Image analysis was performed using the image analysis software Image Pro Plus Ver. 7.0.1 was used.
- BET specific surface area The BET specific surface area of the composite oxide powder was measured by the BET one-point method by nitrogen adsorption using a BET specific surface area measuring device (Macsorb (registered trademark) HM model-1210 manufactured by Mountec Co., Ltd.). In addition, in the BET specific surface area measurement, the deaeration conditions before the measurement were 105° C. and 20 minutes.
- the conductivity of the air electrode was measured by pelletizing the air electrode material and using a source meter (Source Meter Model 2400 Series manufactured by Keithley Instruments). Specifically, using a powder molding press, the air electrode material is pressed at a pressure of 2 MPa for 1 minute to form pellets of 5 mm ⁇ 5 mm ⁇ 20 mm. After that, using a CIP molding machine (cold isostatic pressing device), molding is performed for 2 minutes at a pressure of 300 MPa. The temperature of the molded pellet is raised from 25° C. to 1200° C. at a rate of 5° C./min, held at 1200° C. for 2 hours, and then cooled naturally to obtain a pellet for conductivity measurement.
- a source meter Source Meter Model 2400 Series manufactured by Keithley Instruments
- a platinum wire with a diameter of 0.2 mm is wound around the obtained pellet at a total of 4 places with a spacing of 3.5 mm on both ends and inside.
- the sample surface and the platinum wire are bonded using silver paste.
- the pellet is heated from 25°C to 900°C using an electric heater.
- the temperature is maintained at 900° C., and a current value is applied to both terminals by changing the current value from 30 mA to ⁇ 30 mA by 10 mA using the 4-terminal method of a source meter, and the voltage value generated at the inner terminal is measured.
- a resistance value is calculated from the obtained relationship between the voltage and the current at the six points.
- the average particle size of the composite oxide powder according to the present embodiment is the value of the volume-based cumulative 50% particle size (D 50 ) measured with a wet laser diffraction scattering particle size distribution analyzer.
- Example 2 3023 g of La2O3 , 1826 g of SrCO3 , 1976 g of Fe2O3 , CoCO, so that the composition of the powder has the composition of La0.6Sr0.4Co0.2Fe0.8O3 .
- a composite oxide powder according to Example 2 was prepared in the same manner as in Example 1, except that 736 g of 3 ⁇ xH 2 O, 3000 g of pure water, and 400 g of ammonium polyacrylate dispersant were weighed to prepare a raw material slurry. was made. X-ray crystal analysis of the produced composite oxide powder confirmed that it was a perovskite-type composite oxide powder. The physical properties of the produced perovskite-type composite oxide powder were measured in the same manner as in Example 1. Table 2 shows the measurement results.
- Example 3 The temperature was raised at a rate of 1.5°C/min up to 900°C and 1.0°C/min from 900°C to 1400°C, then held at 1400°C for 8 hours, and then increased from 1400°C to 250°C at a rate of 1.0°C/min.
- a composite oxide powder according to Example 3 was produced in the same manner as in Example 1, except that the temperature was lowered at a rate of °C/min and then naturally lowered. X-ray crystal analysis of the produced composite oxide powder confirmed that it was a perovskite-type composite oxide powder.
- the physical properties of the produced perovskite-type composite oxide powder were measured in the same manner as in Example 1. Table 2 shows the measurement results.
- Example 4 Preparation of Raw Material Slurry ⁇ 1> 3400 g of La 2 O 3 and SrCO 3 are added so that the composition of the powder has a composition of La 0.49 Sr 0.24 Ca 0.25 Mn 1.03 O 3 Weigh 1540 g, 1040 g of CaCO3, 4025 g of MnO2 , 4794 g of pure water and 500 g of ammonium polyacrylate dispersant. ⁇ 2> 3100 g of ZrO 2 beads with a diameter of 1.75 mm are placed in a vessel of a bead mill (capacity: 1.2 liters).
- Example 5 (Example 5) 6718 g of La2O3 , 2937 g of NiCO3 , 1962 g of CoCO3 , 4100 g of pure water , a dispersant of ammonium polyacrylate, so that the composition of the powder has the composition of LaNi0.6Co0.4O3
- a composite oxide powder was obtained in the same manner as in Example 1, except that 500 g of was weighed to form a raw material slurry. X-ray crystal analysis of the obtained composite oxide powder confirmed that it was a perovskite-type composite oxide powder.
- the physical properties of the produced perovskite-type composite oxide powder were measured in the same manner as in Example 1. Table 2 shows the measurement results.
- Comparative example 1 A composite oxide according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the cylindrical crucible was covered and fired in a sealed state. X-ray crystal analysis of the obtained composite oxide powder confirmed that it was a perovskite-type composite oxide powder. The physical properties of the produced perovskite-type composite oxide powder were measured in the same manner as in Example 1. Table 2 shows the measurement results.
- Comparative example 2 A composite oxide according to Comparative Example 2 was obtained in the same manner as in Example 1, except that the raw material slurry was spray-dried to obtain granulated powder, and then the powder was not dried in a dryer.
- the water content of the granulated powder obtained by spray-drying the raw material slurry in Comparative Example 2 was 6.0% by mass.
- X-ray crystal analysis of the obtained composite oxide powder confirmed that it was a perovskite-type composite oxide powder.
- the physical properties of the produced perovskite-type composite oxide powder were measured in the same manner as in Example 1. Table 2 shows the measurement results.
- Example 3 Without going through the spray drying process, the raw material slurry is filtered and separated, then dried in the air at 120 ° C. for 24 hours in a box dryer to obtain a precursor (moisture content is less than 5%), followed by a calcination process. Thereafter, sintering was carried out in the same manner as in Example 1 to obtain a composite oxide powder according to Comparative Example 3. X-ray crystal analysis of the obtained composite oxide powder confirmed that it was a perovskite-type composite oxide powder. The physical properties of the produced perovskite-type composite oxide powder were measured in the same manner as in Example 1. Table 2 shows the measurement results.
- Comparative Example 1 since sintering was not performed in an open system, the gas components generated from the raw material salts of the elements A and B remained in the crucible without being removed. Further, in Comparative Example 2, since the raw material slurry was spray-dried to obtain the granulated powder, the drying was not performed, so that the gas generated from the granulated powder was not removed in the subsequent sintering, and the crucible was not removed. stayed inside.
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Abstract
Description
第2の発明の一態様に係るペロブスカイト型複合酸化物粉末は、一般式ABO3-δ(A元素はランタン、ストロンチウム、カルシウムから選択される少なくとも一種、B元素はマンガン、コバルト、ニッケル、鉄から選択される少なくとも一種、δは酸素欠損量を示す)で表される組成である。
第3の発明の一態様に係るペロブスカイト型複合酸化物粉末は、前記A元素としてランタンが必須の成分として含まれる。
第4の発明の一態様に係るペロブスカイト型複合酸化物粉末は、走査型電子顕微鏡を用いて取得したSEM画像を画像解析し、算出されるペロブスカイト型複合酸化物粉末の円形度が0.70以上1.0未満である。
第5の発明の一態様に係るペロブスカイト型複合酸化物粉末は、BET比表面積が0.01m2/g以上0.5m2/g以下である。
第6の発明の一態様に係るペロブスカイト型複合酸化物粉末は、レーザー回折型粒度分布解析装置により得られる体積基準の平均粒子径D50が10μm以上50μm以下である。
第7の発明の一態様に係る固体酸化物型燃料電池用の空気極は、前記のいずれかに記載のペロブスカイト型複合酸化物粉末を含むことを特徴とする。
第8の発明の一態様に係る固体酸化物型燃料電池は、燃料極と、固体電解質と、空気極とを備えた固体酸化物型燃料電池であって、前記空気極として前記記載の空気極を用いたことを特徴とする。
円形度=4×π×(面積値B)/(画像解析により算出される粒子の周囲長)2
複合酸化物粉末の平均粒子径D50は10μm以上50μm以下であるのが好ましい。より好ましくは15μm以上45μm以下、一層好ましくは20μm以上40μm以下である。上記測定装置による粒度分布測定は、球形に近似した粒子のばらつきを測定するものであり、立体的な粒度のばらつきを知ることができる。SEM画像の画像解析により得られる好ましい粒子のばらつきと、立体的な粒度のばらつきとを特定の範囲とすれば、より優れた発電性能が得られる。上記測定装置により算出される粒度分布の変動係数は75%以下であればよく、好ましくは70%以下、一層好ましくは60%以下である。粒度分布を特定の範囲にするには、篩など公知の分級方法を用いることができる。
複合酸化物粉末の最大フェレ径の幾何標準偏差値、面積値A,面積値B、粒子の周囲長は、次のようにして解析、評価される。
画像解析ソフト(米国 Media Cybernetics社製 Image-Pro Plus等)を用いて、予め撮影された走査型電子顕微鏡(SEM)画像が解析、評価される。走査型電子顕微鏡(SEM)は市販のものを適宜選択して測定することができ、測定倍率も粒子の形状が確認できるものであれば特に制限はない。本明細書においては、日本電子株式会社製のショットキー電界放出形走査電子顕微鏡(JSM-7200F型)を用いた。加速電圧については、表面状態を確認する必要があることから低速であることが好ましく、10kV以下とすることが好ましい。本明細書では加速電圧は3.0kV、加速電流10μA、WD(Working Distance):12mm、SE Detector:Mixの条件を用いて撮影した。SEM画像にはミクロンバーを表示させ、その背景は黒色に設定し保存した。SEM画像の解像度設定は、1280×960(ピクセル)以上とすれば、画像解析を行う際に十分な分析精度を得られるので好ましい。一方で、解像度が高すぎる場合には、画像の解析に要する時間がかかりすぎるため、画像解析時間の点から、1280×960(ピクセル)近傍の値に設定することが好ましい。
まず、あらかじめ撮影された画像内にある粒子数がソフトウエアにより自動計測される。この際に、コントラスト等で粒子の抽出がうまくいかない場合には、コントラストを自動調整し、適切な輝度として解析することが好ましい。
次に、本発明に係る複合酸化物粉末の製造方法について具体的に説明する。
工程(a):原料を混合し粉砕する工程
工程(b):原料を乾燥・造粒する工程
工程(c):造粒粉を焼成する工程
工程(d):焼成粉を解粒する工程
(秤量)
目的の組成のペロブスカイト型構造を有する複合酸化物粉末が生成されるように所定の各成分原料を秤量する。成分原料は、通常使用されるものを好適に使用することができる。例えば、La、Sr、Ca、Mn、Co、Ni、Feを含む酸化物、水酸化物、硝酸塩、炭酸塩、硝酸塩、有機酸塩などが挙げられる。これらの中でも環境的な側面及び入手し易さの理由から、炭酸塩、水酸化物または酸化物が特に好ましい。また、成分原料は1つの元素につき炭酸塩、酸化物、水酸化物、硝酸塩などから選ばれた任意の2種類以上の化合物を元素源として選択することもできる。尚、後工程において噴霧乾燥により原料の造粒粉を製造するため、成分原料は水に不溶性の塩であるのが好ましい。また、各成分原料塩中の不純物は、重量で各々100ppm以下となるようにすればよい。
所定量を秤量した各成分原料を純水と混合して原料スラリーを得る。良好な特性を有するペロブスカイト型複合酸化物粉末を得る観点から、原料スラリーの固形分濃度は25質量%以上であるのが好ましい。また、乾燥効率の観点からは、原料スラリーの固形分濃度は40質量%以上が望ましい。もっとも、原料スラリーの固形分濃度が50質量%以上になると、スラリーの粘度が高くなすぎて原料の粉砕が困難になる虞がある。そこで、原料スラリーの固形分濃度が50質量%以上の場合は、原料スラリーに分散剤を添加するのが望ましい。分散剤としては、ポリアクリル酸アンモニウム等が好ましく用いられる。
湿式粉砕はビーズミルを用いるのが好ましい。ビーズミルに用いる粉砕メディアの材質は、機械的強度の高いものならば特に限定はない。所望の粉砕効率を得る観点から粉砕メディア(ビーズ)の直径は2.0mm以下であるのが好ましい。
原料スラリーをビーズミルで粉砕した後に、さらに分散させて、均一性の高いスラリーとするのがより好ましい。その前段階として、ビーズミルに使用したビーズをスラリーから分離回収する必要がある。ビーズ径の3/4以下である目開きを有する篩にスラリーを通過させてビーズを分離回収する方法がよい。ただし、あまりにも目開きの細かい篩を使用すると、篩の目に固形分が付着して目詰まりが生じ、分離回収効率が悪くなるので適当でない。また、この際、ビーズに粉砕粉末が付着して粉砕粉末の回収効率が低下しないよう、純水を用いて装置をできるだけ洗浄することが好ましい。ただし、あまりにも純水を加えすぎると、後の段階において固形分濃度を調整しづらくなる場合があるので注意を要する。原料スラリーを分散させる方法としては、公知の方法を採用することが出来るが、剪断力を加えて分散させる方法が好ましい。例えば高速せん断型分散機を使用して分散させる方法が挙げられる。高速せん断分散機としては、例えばディゾルバー型、ロータステーター型、コロイドミル型、薄膜旋回型が用いられ、これらの中でもロータステーター型分散機がより好適に用いられる。ロータステーター型分散機を用いる場合、容量5L程度の少量スケールのものであれば回転数は10000rpm以下が好ましく、より好ましくは8000rpm以下である。これ以上の容量で処理の際には、回転数はスケールファクターを考慮して適宜決定すればよい。
(乾燥・造粒)
湿式粉砕後の原料スラリーを乾燥して造粒する。原料スラリーを乾燥して球状に造粒するには、噴霧乾燥が適している。噴霧乾燥には、球形の造粒粉を得る観点からスプレードライヤーが好適に用いられる。スプレードライヤーには、ノズル式、ディスク式があるが、粒径の大きい球形の粒子を得るためにはディスク式が好ましい。アトマイザーディスクの回転数は、原料スラリーを供給する速度やドライヤーの送風量、チャンバー容量にもよるが、高回転なほど原料スラリーを剪断し造粒する操作が均一になるため粒子の形状が歪むことなく球状になりやすい。ディスク式スプレードライヤーを用いることによって、最大フェレ径の整った粒子とすることができる。
乾燥用熱風の温度は、噴霧乾燥後、造粒された粒子に水分が残らない温度が望ましい。具体的には、入り口温度で150~200℃、出口温度は60℃以上が望ましい。
原料スラリーの供給速度は、例えば、乾燥室の容量が1m3程度の装置の場合は、造粒される粒子の形状を保つことが出来、生産性も担保出来ることから5~30kg/hとするのが好ましい。また、スラリーにおける固形分濃度が高すぎると、チャンバーへの供給時にスラリーの流動性が低く停滞する場合や、乾燥が十分に行えず生乾きの状態になる場合があるので好ましくない。一方で、スラリーの固形分濃度が低すぎると、回収効率が低くなりすぎるので不適当である。このことから、スラリーの固形分濃度としては30~90%の範囲が好ましく、より好ましくは35~85%の範囲、さらに好ましくは40~80%の範囲である。
乾燥された造粒粉は焼成炉にて焼成される。焼成炉は、熱源として電気式又はガス式のシャトルキルン、ローラハースキルン、ロータリーキルンなど従来公知のものが使用できる。焼成温度は、複合酸化物粉末を構成する粒子の粒子内部の充填率を上げ、粒子の導電率を上げる観点から850℃以上1600℃以下の範囲が望ましい。また、複合酸化物粉末の導電率を上げる観点から焼成温度は900℃以上が好ましい。また、焼成後の焼成粉の解粒を容易とする観点から焼成温度は1500℃以下が好ましく、1400℃以下であると粒子の形状が整うようになるので更に好適である。また、BET比表面積は、焼成温度を調整することで所望の値に調整することが出来る。
焼成粉を解粒して複合酸化物粉末を得る。解粒の際、粒子の球形形状を損なわないように留意する。解粒にはサンプルミル、ヘンシェルミキサー、ピンミル等を用いることができ、粒子の球形形状を損なわない条件で解粒を行う。具体的には、例えば20Lの容量を持つヘンシェルミキサーを用いる場合、回転数は2500rpm以下、好ましくは2000rpmが望ましい。回転数が2500rpm以下であれば、粒子の球形形状を損なうおそれが無いからである。容量を変化させたときには適宜回転数を調整し、粒子の球形形状が損なわれないようにする。
本発明に係る複合酸化物粉末は、SOFCの空気極として好適に使用される。SOFCの空気極は、例えば、本発明に係る複合酸化物粉末を成型体とし焼結することによって作製される。
SOFCについて説明する。図2は、SOFCの一例を模式的に示した断面構成図である。SOFCは、支持体となる薄板状あるいはシート状の燃料極1と、燃料極1の表面に形成された固体電解質膜2と、固体電解質膜2の表面に形成された薄板状あるいはシート状の空気極3とが積層された構造を有する。
(1)原料スラリーの作製
<1>La0.49Sr0.24Ca0.25Mn1.03O3の組成を有するように、La2O3を3192g、SrCO3を1417g、CaCO3を960g、MnCO3を4612g、純水を4100g、ポリアクリル酸アンモニウムの分散剤を500g秤量する。
<2>ビーズミル(容量1.2リットル)のベッセル内に、直径1.75mmのZrO2ビーズを3100g仕込む。
<3>純水と分散剤とをバッファータンクに投入して混合し分散剤水溶液とする。そして、分散剤水溶液を、ポンプを用いてビーズミルに循環させる。
<4>バッファータンク内の分散剤水溶液を400rpmで攪拌しながら、ここへ、上記秤量したLa2O3、SrCO3、CaCO3、MnCO3を投入する。
<5>ビーズミルを1000rpmで回転させ、投入したLa2O3、SrCO3、CaCO3、MnCO3を80分間粉砕する。その後、目開き1mmの篩にスラリーを通過させてビーズを分離回収し、ビーズに付着した原料については200mLの純水を用いて洗浄した。得られたスラリーは、高速乳化・分散機(プライミクス株式会社製ホモミクサーMarkII)を使用して、8000rpmで5分間分散させ、原料スラリーを作製した。
<1>作製した原料スラリーに純水をさらに添加し、原料スラリーの粉末の固形分濃度を63質量%に調整した。
<2>スプレードライヤー(大川原加工機株式会社製スプレードライヤー)のディスク回転数を25000rpm、乾燥用熱風温度を入口温度で150℃、出口温度で75℃とし、原料スラリーの供給速度を9kg/hとして、原料スラリーの噴霧乾燥を行って造粒粉を得た。得られた造粒粉を熱風式乾燥機を用いて100℃で1時間乾燥した。乾燥した造粒粉の水分量は赤外線水分計を用いて測定したところ4.0質量%であった。
円筒型のるつぼ(直径12cm,高さ5cm)に、得られた造粒粉230gを仕込んだ。そして、大気中で25℃から800℃まで昇温速度を7.0℃/min、800℃から1300℃まで3.5℃/minとし、1300℃で4時間保持した後、ヒーターを切り自然降温させて焼成粉を得た。
得られた焼成粉を、後述のX線回折測定で解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認された。
得られた焼成粉2000gをヘンシェルミキサーに装填した。
ヘンシェルミキサーの回転数を1400rpmとし、60秒間焼成粉の粉砕を行って、実施例1に係るペロブスカイト型複合酸化物粉末を得た。
得られたペロブスカイト型複合酸化物粉末の実測面積値(B)、最大フェレ径から算出された面積値(A)、最大フェレ径およびその幾何標準偏差値、円形度、BET法による比表面積値、導電率、平均粒子径D50をそれぞれ下記方法で測定した。測定結果を表2に示す。
複合酸化物粉末のXRD測定を株式会社リガク製のUltimaIVを用いて行う。測定条件としては、管球はCuを用い、管電圧は40kV、管電流は40mA、発散スリット1/2°、散乱スリット8mm、受光スリットは解放設定、ステップ幅は0.02°、計測時間は4°/分の設定とした。得られたX線回折パターンに基づいて、X線回折(XRD)装置に付属の解析ソフトウェア(株式会社リガク製の統合粉末X線解析ソフトウェアPDXL2用ICDS(Inorganic Crystal Structure Database))により、複合酸化物粉末の結晶相の同定、および不純成分の組成の解析を行う。結晶相は単相であることが適切ではあるが、わずか(異相/ペロブスカイト相のメインピークの強度比が10%未満)であれば許容することが出来る。ただし、この異相の存在に起因すると見られる導電率の低下などが生じる場合には可能な限りこれら異相の存在を少なくしなければならない。
複合酸化物粉末の最大フェレ径の幾何標準偏差値、面積値A,面積値B、粒子の周囲長、円形度は、次のようにして解析、評価した。
画像解析ソフト(米国 Media Cybernetics社製 Image-Pro Plus等)を用いて、撮影された走査型電子顕微鏡(SEM)画像を解析、評価した。走査型電子顕微鏡(SEM)は日本電子株式会社製のショットキー電界放出形走査電子顕微鏡(JSM-7200F型)を用いた。加速電圧は3.0kV、加速電流10μA、WD(working Distance):12mm、SE Detector:Mixの条件を用いて撮影した。粒子径を算出するのに使用した写真の倍率は1000倍とした。SEM画像にはミクロンバーを表示させ、その背景は黒色に設定し保存した。SEM画像の解像度設定は、1280×960(ピクセル)以上とした。
複合酸化物粉末のBET比表面積は、BET比表面積測定装置(株式会社マウンテック製のMacsorb(登録商標)HM model―1210)を用いて窒素吸着によるBET1点法で測定した。なお、BET比表面積測定において、測定前の脱気条件は105℃、20分間とした。
空気極の導電率は、空気極材料をペレット化し、ソースメータ(ケースレー・インスツルメンツ社製 Source Meter Model 2400 Series)を用いて測定した。具体的には、粉体成形プレス装置を用いて、空気極材料を2MPaの圧力で1分間加圧して5mm×5mm×20mmのペレットを成形する。その後、CIP成型機(冷間等方圧加圧装置)を用いて、300MPaの圧力で2分間成形する。成形したペレットを、25℃から1200℃まで5℃/minで昇温し、1200℃で2時間保持した後に自然降温させて、導電率測定用ペレットを得る。得られたペレットに直径0.2mmの白金線を両端及び内側において3.5mmの間隔になるよう計4か所に巻き付ける。試料面と白金線を銀ペーストを用いて接合する。このペレットを電気ヒーターを用いて25℃から900℃に変化させる。900℃で保持し、ソースメータの4端子法を用いて両端の端子に30mAから-30mAまで10mAずつ電流値を変化させて電流を印加し、内側の端子に発生する電圧値を測定する。得られた6点の電圧と電流の関係より抵抗値を算出する。そして下記式から導電率σを算出する。
導電率σ=L/(R×b×d)
(式中、L:電圧端子間距離、b×d:断面積、R:抵抗)
本実施形態に係る複合酸化物粉末の平均粒子径は、湿式のレーザー回折散乱粒度分布測定装置により計測した体積基準の累積50%粒子径(D50)の値である。
粉末の組成が、La0.6Sr0.4Co0.2Fe0.8O3の組成を有するように、La2O3を3023g、SrCO3を1826g、Fe2O3を1976g、CoCO3・xH2Oを736g、純水を3000g、ポリアクリル酸アンモニウムの分散剤を400g秤量して原料スラリーを作製した以外は、実施例1と同様にして、実施例2に係る複合酸化物粉末を作製した。作製した複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。
昇温速度を900℃まで1.5℃/min、900℃から1400℃まで1.0℃/minで昇温し、その後1400℃で8時間保持した後、1400℃から250℃まで1.0℃/minで降温し、その後自然降温した以外は、実施例1と同様にして、実施例3に係る複合酸化物粉末を作製した。作製した複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。
(1)原料スラリーの作製
<1>粉末の組成が、La0.49Sr0.24Ca0.25Mn1.03O3の組成を有するように、La2O3を3400g、SrCO3を1540g、CaCO3を1040g、MnO2を4025g、純水を4794g、ポリアクリル酸アンモニウムの分散剤を500g秤量する。
<2>ビーズミル(容量1.2リットル)のベッセル内に、直径1.75mmのZrO2ビーズを3100g仕込む。
<3>純水と分散剤とpH=10程度になるように苛性ソーダをバッファータンクに投入して混合し分散剤水溶液とする。そして、分散剤水溶液を、ポンプを用いてビーズミルに循環させる。
<4>バッファータンク内の分散剤水溶液を400rpmで攪拌しながら、ここへ、上記秤量したLa2O3、SrCO3、CaCO3、MnO2を投入する。
<5>ビーズミルを1000rpmで回転させ、投入したLa2O3、SrCO3、CaCO3、MnO2を80分間粉砕し、その後、目開き1mmの篩にスラリーを通過させてビーズを分離回収し、ビーズに付着した原料については200mLの純水を用いて洗浄した。得られたスラリーは、高速乳化・分散機(プライミクス株式会社製ホモミクサーMarkII)を使用して、8000rpmで5分間乳化分散させ、原料スラリーを作製した。
<1>作製した原料スラリーに純水を添加し、原料スラリーにおける粉末の固形分濃度を63質量%に調整した。
<2>スプレードライヤー(大川原加工機株式会社製スプレードライヤー)のディスク回転数を25000rpm、乾燥用熱風温度を入口温度で150℃、出口温度で75℃とし、原料スラリーの供給速度を9kg/hとして、原料スラリーの噴霧乾燥を行って造粒粉を得た。得られた造粒粉を熱風式乾燥機を用いて150℃で1時間乾燥を行った。乾燥した造粒粉の水分量について赤外線水分計を用いて測定したところ3.8質量%であった。
円筒型のるつぼ(直径12cm,高さ5cm)に、得られた造粒粉230gを仕込んだ。そして、大気中で25℃から900℃まで1.5℃/minで昇温し、さらに900℃から1400℃まで0.89℃/minで昇温し、その後1400℃で8時間保持した後、1400℃から250℃まで1.0℃/minで降温し、その後自然降温させて焼成粉を得た。
得られた焼成粉2000gをヘンシェルミキサーに装填した。
回転数を1400rpmとし、60秒間の粉砕を行って、実施例4に係る複合酸化物を得た。
得られた複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。
粉末の組成がLaNi0.6Co0.4O3の組成を有するように、La2O3を6718g、NiCO3を2937g、CoCO3を1962g、純水を4100g、ポリアクリル酸アンモニウムの分散剤を500g秤量して原料スラリーを形成した以外は実施例1と同様にして、複合酸化物粉が得た。
得られた複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。
円筒型のるつぼに蓋をして密閉状態で焼成を行った以外は、実施例1と同様にして、比較例1に係る複合酸化物が得た。
得られた複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。
原料スラリーの噴霧乾燥を行って造粒粉を得た後の乾燥機での乾燥を行わなかったこと以外は実施例1と同様にして比較例2に係る複合酸化物を得た。なお、比較例2において原料スラリーを噴霧乾燥して得られた造粒粉の水分量は6.0質量%であった。
得られた複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。
噴霧乾燥工程を経ずに、原料スラリーをろ過分離し、その後、箱形乾燥機で120℃24時間大気中で乾燥して前駆体(水分値は5%未満)を得て、その後の焼成工程以降は実施例1と同様にして焼成を行い、比較例3に係る複合酸化物粉末を得た。
得られた複合酸化物粉末をX線による結晶解析したところ、ペロブスカイト型複合酸化物粉末となっていることが確認できた。
作製したペロブスカイト型複合酸化物粉末の物性を実施例1と同様に測定した。測定結果を表2に示す。なお、前駆体を走査型電子顕微鏡により観測したところ、球状を呈しておらず、一次粒子がネットワーク状に連なった形状となっていた。焼成後の粒子は粒子間視野によっては“大きすぎる”一粒子、すなわち粒子焼結が進行してしまったことで、個々の粒子が撮影した視野の中からはみ出してしまうような粒子が多く、それらの粒子を計測しても形態を把握することにならず、本発明に属さないことが明確であったことから、フィレ径の算出を行わなかった。
比較例3の複合酸化物粉末は、SEMで画像解析を行うと貼り付いたような形になっており、解析が困難(粒子間が接続していること、また撮影視野から出てしまっているものが多く、形状把握ができない)であるとともに、一見して平均粒子径(D50)が本文中に望ましい範囲として開示した粒子径よりも大きく、本発明を満足しないことが明らかであったため、粒子径の計測および評価を行わなかった。
Claims (8)
- 走査型電子顕微鏡を用いて取得したSEM画像を画像解析し、算出されるペロブスカイト型複合酸化物粉末の最大フェレ径の幾何標準偏差値が1.01以上1.60未満であり、
前記ペロブスカイト型複合酸化物粉末が球形であると仮定して前記最大フェレ径から算出される面積値Aと、画像解析により直接算出される面積値Bとの比(B/A)が0.7以上1.0未満であるペロブスカイト型複合酸化物粉末。 - 前記ペロブスカイト型複合酸化物粉末が、一般式ABO3-δ(A元素はランタン、ストロンチウム、カルシウムから選択される少なくとも一種、B元素はマンガン、コバルト、ニッケル、鉄から選択される少なくとも一種、δは酸素欠損量を示す)で表される組成ある請求項1に記載のペロブスカイト型複合酸化物粉末。
- 前記A元素としてランタンが必須の成分として含まれる請求項2に記載のペロブスカイト型複合酸化物粉末。
- 走査型電子顕微鏡を用いて取得したSEM画像を画像解析し、算出されるペロブスカイト型複合酸化物粉末の円形度が0.70以上1.0未満である請求項1~3のいずれかに記載のペロブスカイト型複合酸化物粉末。
- BET比表面積が0.01m2/g以上、0.5m2/g以下である請求項1~4のいずれかに記載のペロブスカイト型複合酸化物粉末。
- レーザー回折型粒度分布解析装置により得られる体積基準の平均粒子径D50が10μm以上50μm以下である請求項1~5のいずれかに記載のペロブスカイト型複合酸化物粉末。
- 請求項1~6のいずれかに記載のペロブスカイト型複合酸化物粉末を含む固体酸化物型燃料電池用の空気極。
- 燃料極と、固体電解質と、空気極とを備えた固体酸化物型燃料電池であって、
前記空気極として前記請求項7に記載の空気極を用いた固体酸化物型燃料電池。
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