KR100281829B1 - Preparation of barium titanate fine powder by hydrothermal reaction using titanium 2-alkoxyethoxide precursors - Google Patents
Preparation of barium titanate fine powder by hydrothermal reaction using titanium 2-alkoxyethoxide precursors Download PDFInfo
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- KR100281829B1 KR100281829B1 KR1019990001307A KR19990001307A KR100281829B1 KR 100281829 B1 KR100281829 B1 KR 100281829B1 KR 1019990001307 A KR1019990001307 A KR 1019990001307A KR 19990001307 A KR19990001307 A KR 19990001307A KR 100281829 B1 KR100281829 B1 KR 100281829B1
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- barium
- titanium
- aqueous solution
- barium titanate
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- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 title claims abstract description 48
- 229910002113 barium titanate Inorganic materials 0.000 title claims abstract description 48
- 239000010936 titanium Substances 0.000 title claims abstract description 45
- 239000000843 powder Substances 0.000 title claims abstract description 42
- 229910052719 titanium Inorganic materials 0.000 title claims abstract description 41
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000001027 hydrothermal synthesis Methods 0.000 title claims abstract description 19
- 239000002243 precursor Substances 0.000 title claims abstract description 18
- 238000002360 preparation method Methods 0.000 title 1
- 238000000034 method Methods 0.000 claims abstract description 22
- 239000007864 aqueous solution Substances 0.000 claims abstract description 19
- 159000000009 barium salts Chemical class 0.000 claims abstract description 19
- 239000000243 solution Substances 0.000 claims abstract description 15
- XBYNNYGGLWJASC-UHFFFAOYSA-N barium titanium Chemical compound [Ti].[Ba] XBYNNYGGLWJASC-UHFFFAOYSA-N 0.000 claims abstract description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000003513 alkali Substances 0.000 claims abstract description 10
- 239000002904 solvent Substances 0.000 claims abstract description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 6
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- XNWFRZJHXBZDAG-UHFFFAOYSA-N 2-METHOXYETHANOL Chemical compound COCCO XNWFRZJHXBZDAG-UHFFFAOYSA-N 0.000 claims description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 5
- AYJRCSIUFZENHW-UHFFFAOYSA-L barium carbonate Chemical compound [Ba+2].[O-]C([O-])=O AYJRCSIUFZENHW-UHFFFAOYSA-L 0.000 claims description 5
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 claims description 5
- 229910001863 barium hydroxide Inorganic materials 0.000 claims description 5
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 4
- ITHZDDVSAWDQPZ-UHFFFAOYSA-L barium acetate Chemical compound [Ba+2].CC([O-])=O.CC([O-])=O ITHZDDVSAWDQPZ-UHFFFAOYSA-L 0.000 claims description 4
- 239000012153 distilled water Substances 0.000 claims description 4
- 239000003960 organic solvent Substances 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 3
- SBASXUCJHJRPEV-UHFFFAOYSA-N 2-(2-methoxyethoxy)ethanol Chemical compound COCCOCCO SBASXUCJHJRPEV-UHFFFAOYSA-N 0.000 claims description 2
- ZNQVEEAIQZEUHB-UHFFFAOYSA-N 2-ethoxyethanol Chemical compound CCOCCO ZNQVEEAIQZEUHB-UHFFFAOYSA-N 0.000 claims description 2
- 229940093475 2-ethoxyethanol Drugs 0.000 claims description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- 125000000217 alkyl group Chemical group 0.000 claims description 2
- 125000003118 aryl group Chemical group 0.000 claims description 2
- WDIHJSXYQDMJHN-UHFFFAOYSA-L barium chloride Chemical compound [Cl-].[Cl-].[Ba+2] WDIHJSXYQDMJHN-UHFFFAOYSA-L 0.000 claims description 2
- 229910001626 barium chloride Inorganic materials 0.000 claims description 2
- IWOUKMZUPDVPGQ-UHFFFAOYSA-N barium nitrate Chemical compound [Ba+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O IWOUKMZUPDVPGQ-UHFFFAOYSA-N 0.000 claims description 2
- 125000001797 benzyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])* 0.000 claims description 2
- 125000004848 alkoxyethyl group Chemical group 0.000 claims 1
- 235000011114 ammonium hydroxide Nutrition 0.000 claims 1
- 238000007865 diluting Methods 0.000 claims 1
- 238000000746 purification Methods 0.000 claims 1
- 239000012266 salt solution Substances 0.000 claims 1
- 239000002245 particle Substances 0.000 abstract description 19
- 230000000694 effects Effects 0.000 abstract description 8
- -1 Titanium organometallic compound Chemical class 0.000 abstract description 4
- 238000006703 hydration reaction Methods 0.000 abstract description 4
- 239000003446 ligand Substances 0.000 abstract description 4
- 230000003335 steric effect Effects 0.000 abstract description 4
- 238000006116 polymerization reaction Methods 0.000 abstract description 3
- 239000013522 chelant Substances 0.000 abstract description 2
- 238000006482 condensation reaction Methods 0.000 abstract description 2
- 125000001033 ether group Chemical group 0.000 abstract description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 abstract description 2
- 150000002894 organic compounds Chemical class 0.000 abstract description 2
- 229910052788 barium Inorganic materials 0.000 description 18
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000000725 suspension Substances 0.000 description 6
- 239000002131 composite material Substances 0.000 description 5
- 238000000921 elemental analysis Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000001308 synthesis method Methods 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 238000004566 IR spectroscopy Methods 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000004626 scanning electron microscopy Methods 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical group OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000007385 chemical modification Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- BBJSDUUHGVDNKL-UHFFFAOYSA-J oxalate;titanium(4+) Chemical compound [Ti+4].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O BBJSDUUHGVDNKL-UHFFFAOYSA-J 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 238000010671 solid-state reaction Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 125000001424 substituent group Chemical group 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/003—Titanates
- C01G23/006—Alkaline earth titanates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
Abstract
분자내에 히드록시기와 1 개 이상의 에테르기를 갖는 유기화합물(2-알콕시에탄올)을 리간드로 갖는 티타늄 유기금속화합물 전구체(precursor)는 리간드의 입체 효과와 전자 효과 및 킬레이트 효과에 의해 수화 반응 및 축합 반응에 따른 고분자화 현상을 저지한다. 이러한 티타늄 전구체를 알코올 용매에 희석한 후 바륨염의 수용액과 혼합하여 균일하게 분산된 바륨-티타늄 복합체를 형성하고 알칼리 수용액에서 수열(hydrothermal) 반응 조건을 조절하여 입자가 고르고 구형이며 미세한 결정형의 화학양론적 티탄산바륨(barium titanate) 미세분말을 제조하는 방법을 제공한다.Titanium organometallic compound precursors having an organic compound (2-alkoxyethanol) having a hydroxy group and at least one ether group in a molecule thereof as ligands are characterized by hydration reaction and condensation reaction by the steric effect of the ligand, the electron effect, and the chelate effect. Retards the polymerization phenomenon. The titanium precursor is diluted in an alcohol solvent and then mixed with an aqueous solution of barium salt to form a uniformly dispersed barium-titanium complex, and the hydrothermal reaction conditions are adjusted in an aqueous alkali solution to make particles even, spherical and fine crystalline stoichiometric. Provided is a method for preparing barium titanate fine powder.
Description
본 발명은 입체 효과와 전자 효과 및 킬레이트 효과를 주는 리간드를 가지고 있는 티타늄 유기금속화합물을 바륨염과 함께 수열반응하여 화학양론적 티탄산바륨(BaTiO3) 미세분말을 제조하는 방법에 관한 것이다. 더욱 구체적으로, 본 발명은 분자 내에 히드록시기와 1개 이상의 에테르기를 갖는 유기화합물(알콕시에탄올)을 리간드로 갖는 티타늄 유기금속화합물 전구체를 바륨 염과 혼합하여 균일한 바륨-티타늄 복합체를 형성시키고 알칼리 수용액에서 수열반응 조건을 조절하여, 입자가 고르고 구형이며 미세한 결정형의 화학양론적 티탄산바륨 미세 분말을 제조하는 것으로 이루어진 방법에 관한 것이다.The present invention relates to a method for producing a stoichiometric barium titanate (BaTiO 3 ) micropowder by hydrothermally reacting a titanium organometallic compound having a ligand having a steric effect, an electron effect and a chelating effect with a barium salt. More specifically, the present invention mixes a titanium organometallic compound precursor having an organic compound (alkoxyethanol) having a hydroxy group and at least one ether group as a ligand in a molecule with a barium salt to form a uniform barium-titanium complex and in an aqueous alkali solution. By controlling the hydrothermal reaction conditions, the present invention relates to a process comprising the production of stoichiometric barium titanate powder of uniform, spherical and fine crystal form.
티탄산바륨은 높은 유전상수와 강유전적인 성질 때문에 전자공학산업에서 중요한 물질로 여겨지고 있으며 적층콘덴서(MLCC), 필터, 서미스터(thermistor), 배리스터(varistor), electro-optic device 등의 제품에 주원료로 사용되어 왔다. 특히 바륨과 티타늄의 몰비가 화학양론적이고 입자 크기가 균일한 미세 분말은 유전 손실이 없고 제품의 불량률이 매우 낮으며 성형 온도도 낮아 값비싼 귀금속 전극을 사용하지 않고도 세라믹 적층콘덴서 등을 만들 수 있는 경제적 장점이 있다. 뿐만 아니라 최근 점점 다양화, 고밀도화, 극소형화 추세에 있는 제품의 사양에 대한 요구는 이들 미세 분말의 제조 기술 없이는 불가능하므로 산업적으로도 매우 중요하다.Barium titanate is regarded as an important material in the electronics industry because of its high dielectric constant and ferroelectric properties.It is used as a main raw material in products such as multilayer capacitors (MLCC), filters, thermistors, varistors, and electro-optic devices. come. Particularly, the fine powder with stoichiometric barium and titanium and uniform particle size has no dielectric loss, very low defect rate and low molding temperature, making it an economical way to make ceramic multilayer capacitors without using expensive precious metal electrodes. There is an advantage. In addition, the demand for specifications of products which are becoming more diversified, higher density, and miniaturized in recent years is very important industrially, since it is impossible without the manufacturing technology of these fine powders.
전통적으로 티탄산바륨은 탄산바륨(BaCO3)과 이산화티탄(TiO2)간의 고체상태 반응으로 1300 ℃ 정도의 고온에서 제조되어졌으나 보통 입자의 최소 분말 크기가 1 미크론 전후로 상당히 큰 편이며 입자의 크기를 조절하기가 어려울 뿐만 아니라 입자들의 뭉침 현상과 소성시에 발생하는 오염 등이 문제화되어 화학적 용액상의 습식 합성법이 개발되어 함께 사용되고 있다. 현재 사용되고 있으며 생산규모가 점차 확장되어가고 있는 습식 합성법은 옥살레이트(oxalate) 침전법이다. 이 방법은 화학적 합성법 중에서 비교적 간단하고 수율이 높다는 장점을 가지고 있으나, 입자의 크기와 뭉침 현상을 조절하기가 용이하지 않다. 또한 바륨/티타늄 옥살레이트의 안정성이 커서 결정성의 티탄산바륨 분말을 얻기 위해서는 고온에서의 열처리를 필요로 하게 되므로 최종적으로 생산되는 분말의 평균 입경은 0.5 미크론 정도에 불과하다.Traditionally, barium titanate has been produced at a high temperature of about 1300 ℃ by the solid-state reaction between barium carbonate (BaCO 3 ) and titanium dioxide (TiO 2 ), but the minimum particle size of the particles is usually around 1 micron and is very large. Not only is it difficult to control, but also agglomeration of particles and contamination generated during firing are problematic, and a wet synthesis method of chemical solution phase has been developed and used together. The wet synthesis method currently in use and gradually expanding production scale is oxalate precipitation. This method has the advantage of relatively simple and high yield in the chemical synthesis method, but it is not easy to control the size and aggregation of particles. In addition, the stability of the barium / titanium oxalate is so large that the heat treatment at high temperature is required to obtain a crystalline barium titanate powder, so the average particle size of the final powder is only about 0.5 micron.
상용화보다는 아직 연구 단계에 머물러 있으나 개발 가능성이 있는 습식 합성법 중의 하나가 저온수열합성법이다. 저온수열합성법은 반응성이 큰 티타늄 전구체를 사용하여 온화한 반응 조건에서 단시간 내에 티탄산바륨의 미세 분말을 제조하는 것이 장점이다. 그러나 보통 습식 합성에 이용되는 이산화티탄이나 사염화티탄, 또는 단순한 티타늄 알콕사이드 등의 수화 반응 및 중축합 반응에 이어지는 고분자화 반응으로 인해, 합성되는 티탄산바륨 입자가 클 뿐만 아니라 입자 크기가 균일하지 못한 단점이 있다. 이것이 심할 경우에는 이산화티탄 티탄산바륨의 상분리에 이르기도 한다. 또한 수열합성법에 의해 제조된 티탄산바륨의 원소분석 결과는 대부분 바륨이 티타늄에 비해 상당히 부족하여 고도 전자공학산업에서의 요구에 부응하기 어려운 형편이다.Although it is still in the research stage rather than commercialization, one of the wet synthesis methods that can be developed is low temperature hydrothermal synthesis. The low temperature hydrothermal synthesis method has an advantage of producing a fine powder of barium titanate within a short time under mild reaction conditions using a highly reactive titanium precursor. However, due to the hydration reaction and the polycondensation reaction such as titanium dioxide, titanium tetrachloride, or simple titanium alkoxide, which are usually used for wet synthesis, the barium titanate particles synthesized are not only large but also have a disadvantage in that the particle size is not uniform. have. If this is severe, it may even lead to phase separation of barium titanium titanate. In addition, elemental analysis of barium titanate produced by hydrothermal synthesis shows that most of barium is considerably insufficient compared to titanium, making it difficult to meet the demands of the high electronics industry.
따라서, 수화반응 속도를 조절하고 중축합반응에 의한 고분자화 현상을 저지할 수 있도록 입체효과와 전자효과 및 킬레이트 효과를 갖는 유기물질을 티타늄에 결합시킨 유기금속 화합물을 출발물질로 하여, 이들 전구체와 바륨염과의 수용액상 반응에서 고분자화 현상이 저지되므로 분자 수준에서의 화학적 균질성과 입자 크기의 균일성이 좋은 고순도의 초미세 세라믹 분말을 제조하는 데 본 발명의 목적이 있다. 또한, 반응 조건을 조절하여, 통상의 저온 수열 반응에서 흔히 발생하는 바륨과 티타늄 몰비의 화학적 불균형 문제를 해결하여 화학양론적인 결정성 티탄산바륨 미세 분말을 제조하고자 하는 데 본 발명의 또다른 목적이 있다.Therefore, to control the rate of hydration reaction and to prevent polymerization by polycondensation reaction, organic precursors in which organic materials having a steric effect, an electron effect and a chelating effect are bound to titanium are used as starting materials. It is an object of the present invention to prepare a high-purity ultrafine ceramic powder having good chemical homogeneity and uniformity of particle size at the molecular level since the polymerization reaction is prevented in an aqueous phase reaction with a barium salt. In addition, it is another object of the present invention to prepare a stoichiometric crystalline barium titanate fine powder by adjusting the reaction conditions to solve the chemical imbalance problem of barium and titanium molar ratios that are common in the ordinary low-temperature hydrothermal reaction. .
도 1은 본 발명의 실시예 1에 의해 제조된 티탄산바륨 분말의 주사현미경(SEM) 사진을 나타낸 것이다.Figure 1 shows a scanning microscope (SEM) photograph of the barium titanate powder prepared by Example 1 of the present invention.
도 2는 본 발명의 실시예 1에 의해 제조된 티탄산바륨 분말의 X선 회절 스펙트럼을 나타낸 것이다.Figure 2 shows the X-ray diffraction spectrum of the barium titanate powder prepared by Example 1 of the present invention.
도 3은 과량의 바륨염을 사용하여 제조된 티탄산바륨 분말(실시예 2)의 주사현미경 사진을 나타낸 것이다.Figure 3 shows a scanning micrograph of the barium titanate powder (Example 2) prepared using the excess barium salt.
도 4는 가압 조건 하에서 수열반응을 수행하여 제조된 티탄산바륨 분말(실시예 3)의 주사현미경 사진을 나타낸 것이다.Figure 4 shows a scanning micrograph of the barium titanate powder (Example 3) prepared by performing a hydrothermal reaction under pressurized conditions.
본 발명은 티타늄 2-알콕시에톡사이드 전구체를 유기 용매에 희석하고, 바륨염 수용액과 혼합하여 바륨-티타늄 복합체를 형성시키고, 이를 강알칼리 수용액에 첨가한 후에 수열반응을 수행하고, 수세 공정을 통하여 정제하는 것으로 이루어진, 결정성 티탄산바륨 분말의 제조 방법을 제공한다.The present invention dilutes a titanium 2-alkoxy ethoxide precursor with an organic solvent, and mixes with a barium salt aqueous solution to form a barium-titanium complex, which is added to a strong alkali aqueous solution, followed by a hydrothermal reaction, and purified through a washing process. It provides a method for producing a crystalline barium titanate powder consisting of.
본 발명은 수분 및 이산화탄소에 민감한 시약들의 특성을 고려하여 비활성기체 분위기 하에서 수행하며, 반응 전체를 통해 이산화탄소를 제거한 3차 증류수를 사용하는 것이 바람직하다. 또한, 마찬가지 측면에서 강알칼리 수용액도 탄산 이온을 제거하여 사용하는 것이 바람직하다.The present invention is carried out in an inert gas atmosphere in consideration of the properties of the reagents sensitive to moisture and carbon dioxide, it is preferable to use the third distilled water to remove the carbon dioxide throughout the reaction. In addition, it is preferable to use a strong alkali aqueous solution also remove carbonate ion from a similar aspect.
먼저, 본 발명에서의 티타늄 2-알콕시에톡사이드 전구체 화합물은 다음 반응식 1과 같이, 티타늄 이소프로폭사이드를 2-알콕시에탄올과 반응시킴으로써 얻어질 수 있다.First, the titanium 2-alkoxy ethoxide precursor compound in the present invention can be obtained by reacting titanium isopropoxide with 2-alkoxyethanol, as shown in Scheme 1 below.
상기 식 중에서, R은 2-알콕시에탄올을 유지할 수 있는 통상의 치환기로서, C1-C6의 저급 알킬기, 아릴기, 벤질 또는 이들의 알콕시에틸기를 들 수 있다. 즉, 본 발명의 2-알콕시에탄올로서는 다음 화학식 1을 갖는 화합물을 사용할 수 있는데:Among the formula, R may be a conventional substituents which can maintain the 2-alkoxy ethanol, a lower alkyl group, an aryl group, a benzyl or a alkoxy group of C 1 -C 6. That is, as the 2-alkoxyethanol of the present invention, a compound having the following Chemical Formula 1 may be used:
식 중에서, R은 상기 반응식 1에서와 같으며, 2-메톡시에탄올, 2-에톡시에탄올 또는 디에틸렌글리콜메틸에테르 등을 예로 들 수 있다. 상기 반응식 1의 반응을 수행하고, 2-프로판올을 증류하여 제거한 후에 감압하에서 생성된 티타늄 2-알콕시에톡사이드 전구체를 증류하여 정제한 후에, 본 발명에 사용할 수 있다.In the formula, R is the same as in Scheme 1, and 2-methoxyethanol, 2-ethoxyethanol or diethylene glycol methyl ether and the like can be given. After the reaction of Scheme 1 above, 2-propanol is distilled off, the titanium 2-alkoxy ethoxide precursor produced under reduced pressure is distilled and purified, and then used in the present invention.
본 발명에서는, 티타늄 2-알콕시에톡사이드 전구체를 희석시키는데, 2∼6 당량의 알코올 용매를 사용하는 것이 바람직하다. 상기 알코올 용매의 예로서는 에탄올, 2-프로판올, 2-메톡시에탄올 등을 들 수 있다.In the present invention, it is preferable to use 2-6 equivalents of alcohol solvent to dilute the titanium 2-alkoxyethoxide precursor. Examples of the alcohol solvent include ethanol, 2-propanol, 2-methoxyethanol and the like.
또한, 이와 같이 희석된 티타늄 2-알콕시에톡사이드 전구체 용액을 바륨염의 수용액과 혼합할 때에도, 상기 티타늄 화합물의 용액을 바륨염 수용액에 천천히 적가하는 것이 바람직하다. 이러한 공정 순서는, 균일한 바륨-티타늄 복합체의 현탁액을 만들어, 우수한 티탄산바륨 분말을 제조하는 데 매우 중요하다.Moreover, when mixing the titanium 2-alkoxy ethoxide precursor solution diluted in this way with the aqueous solution of a barium salt, it is preferable to slowly add the said titanium compound solution to a barium salt aqueous solution slowly. This process sequence is very important for producing a uniform barium-titanium composite suspension and producing good barium titanate powder.
본 발명에서는 바륨염으로서 염화바륨(BaCl2), 아세트산바륨(Ba(OAc)2), 질산바륨(Ba(NO3)2) 또는 수산화바륨(Ba(OH)2) 등을 사용할 수 있으며, 당량 이상의 양으로 사용할 수 있다. 바륨염을 과량 사용하면, 생성된 티탄산바륨내에서의 티타늄과 바륨의 몰비를 1 정도로 얻을 수 있다. 일반적으로, 티탄산바륨내의 티타늄과 바륨의 몰비가 1인 경우에 가장 바람직한 것으로 알려져 있으며, 이와 같은 몰비를 갖는 티탄산바륨을 화학량론적인 티탄산바륨이라고 한다.In the present invention, as the barium salt, barium chloride (BaCl 2 ), barium acetate (Ba (OAc) 2 ), barium nitrate (Ba (NO 3 ) 2 ), or barium hydroxide (Ba (OH) 2 ) may be used. It can be used in the above amount. When the barium salt is used in excess, the molar ratio of titanium and barium in the produced barium titanate can be obtained to about one degree. In general, it is known to be most preferable when the molar ratio of titanium and barium in barium titanate is 1, and barium titanate having such a molar ratio is called stoichiometric barium titanate.
한편, 알칼리에 대한 내식성이 강한 테프론으로 코팅한 스테인레스스틸 오토클레이브(autoclave)에 강알칼리 수용액을 준비한다. 여기에 상기의 현탁액을 첨가하는데, 이 때 반응후의 pH가 13.5 이상이 되도록 하는 것이 바람직하다. 이 수열반응은 온도, 농도, 압력, 시간 등의 여러 공정상의 조건을 조절하여 수행할 수 있는데, 경우에 따라 우수한 화학량론적인 티탄산바륨을 얻을 수 있다. 일반적으로, 본 발명의 수열 반응은 80∼120 ℃에서 티타늄 전구체의 농도는 0.1∼0.2 M로 40 분∼2 시간 동안을 수행할 수 있다.On the other hand, a strong alkaline aqueous solution is prepared in a stainless steel autoclave coated with Teflon strong corrosion resistance to alkali. The above suspension is added thereto, and it is preferable that the pH after the reaction be 13.5 or more. This hydrothermal reaction can be carried out by adjusting various process conditions such as temperature, concentration, pressure, and time, and in some cases, excellent stoichiometric barium titanate can be obtained. In general, the hydrothermal reaction of the present invention can be carried out for 40 minutes to 2 hours at a concentration of 0.1 to 0.2 M titanium precursor at 80 ~ 120 ℃.
특히, 본 발명의 수열반응을 2∼10 기압의 압력 하에서 수행하는 경우에는, 과량의 바륨염을 사용하지 않고도 화학량론적인 티탄산바륨을 얻을 수 있다.In particular, when the hydrothermal reaction of the present invention is carried out under a pressure of 2 to 10 atm, a stoichiometric barium titanate can be obtained without using an excess barium salt.
이상과 같이 생성된, 본 발명의 티탄산바륨 분말은 잔류하는 금속 이온이나 불순물 을 제거할 수 있도록 첨가제 등이 희석된 증류수로 수세 공정을 수행하고 원심분리기 등을 이용하여 분말만을 분리한다. 수세와 분리 과정은 여러 차례 반복하여 티탄산바륨 분말에 잔류하고 있는 여러 금속 이온이나 수용성 불순물을 완전히 제거하는 것이 바람직하다. 수세시 첨가제로는 수산화바륨이나 암모니아수와 같이 용액의 pH를 10∼11로 유지시켜 주며 전체 조성에 영향을 주지 않는 물질을 사용하는 것이 바람직하다.The barium titanate powder of the present invention produced as described above is washed with distilled water in which additives and the like are diluted to remove residual metal ions or impurities, and only the powder is separated using a centrifuge or the like. Washing and separating are preferably repeated several times to completely remove various metal ions and water-soluble impurities remaining in the barium titanate powder. As the additive in washing, it is preferable to use a material such as barium hydroxide or aqueous ammonia that maintains the pH of the solution at 10 to 11 and does not affect the overall composition.
상기한 바와 같은 수세 과정을 거친 후에, 건조하여 잔류 수분을 제거하면 미세하게 결정화된 티탄산바륨 분말을 얻게 된다. 이 때 건조 온도가 너무 낮으면 수분의 제거율이 낮아지고, 너무 높으면 미세 분말 사이에서 소결 현상이 일어날 수 있음이 관찰되었다. 건조과정은 분말을 오븐에 넣고 60∼190 ℃에서 12∼24 시간 동안 실시하는 것이 적당하다. 여기서, 본 발명과 같은 수열 반응의 장점은 기존에 실시하던 소성과정을 거치지 않고 다만 건조를 통하여 정제된 결정성 분말을 얻을 수 있다는 것이다.After washing with water as described above, it is dried to remove residual moisture to obtain finely crystallized barium titanate powder. At this time, it was observed that if the drying temperature is too low, the removal rate of water is low, and if it is too high, sintering may occur between fine powders. The drying process is suitably carried out in the oven for 12 to 24 hours at 60 ~ 190 ℃. Here, the advantage of the hydrothermal reaction as in the present invention is that it is possible to obtain a purified crystalline powder through drying without undergoing a conventional firing process.
상기한 바와 같이 제조된 티탄산바륨은 X선 회절 분석법(x-ray diffraction: XRD)에 의하여 그 결정성이 확인되었고, 주사 전자 현미경(scanning electron microscopy: SEM)을 이용하여 입자 분포가 고르고 구형이며 입자 크기가 나노미터인 것이 확인되었다. 또한 적외선 분광기(IR), BET, 라만(Raman) 분광기, 열 분석기(TGA) 등에 의한 특성 분석 및 ICP에 의한 원소 분석도 실시하였다.The barium titanate prepared as described above was confirmed crystallinity by X-ray diffraction (XRD), and the particle distribution was uniform, spherical and particles using a scanning electron microscopy (SEM). It was confirmed that the size is nanometer. In addition, characterization by infrared spectroscopy (IR), BET, Raman spectroscopy, thermal analyzer (TGA) and the like and elemental analysis by ICP were also performed.
이하, 실시예를 통해 본 발명을 좀더 구체적으로 설명한다. 그러나, 이들 실시예는 단지 본 발명의 범위 중 일부를 예시하는 것으로서, 본 발명이 이에 국한되는 것은 아니다.Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples merely illustrate some of the scope of the present invention, and the present invention is not limited thereto.
실시예 1Example 1
상기 반응식 1에서와 같이 티타늄 이소프로폭사이드와 2-메톡시에탄올을 반응시켜 합성한 티타늄 전구체, Ti(OCH2CH2OCH3)4를 4 당량의 2-프로판올 용매에 희석한 후 상기 티타늄 전구체와 동일한 당량비의 1 M 바륨아세테이트 수용액에 천천히 적가하고 격렬히 교반하면서 1 시간 동안 반응시킨 후에, 티타늄과 바륨이 균일하게 분산된 바륨-티타늄 복합체 현탁액을 제조하였다.The titanium precursor, Ti (OCH 2 CH 2 OCH 3 ) 4 , synthesized by reacting titanium isopropoxide and 2-methoxyethanol as in Scheme 1, was diluted in 4 equivalents of 2-propanol solvent, and then the titanium precursor. After slowly adding dropwise to an aqueous solution of 1 M barium acetate having the same equivalent ratio as that of and reacting vigorously for 1 hour, a barium-titanium composite suspension in which titanium and barium were uniformly dispersed was prepared.
한편, 알칼리에 대한 내식성이 강한 테프론으로 코팅한 스테인레스스틸 오토클레이브에 강알칼리 수용액을 준비하였는데, 강알칼리 수용액은 수산화나트륨 또는 수산화칼륨 수용액에, 불순물로 존재하는 탄산염의 당량비에 해당하는 바륨염을 가하여 이 때 생기는 탄산바륨 침전을 걸러서 탄산 이온을 제거하는 것이다. 이렇게 준비한 pH 14 이상의 강알카리 수용액에 상기의 현탁액을 가하여 최종용액에서 바륨 및 티타늄의 농도가 각각 0.2 M이 되고, 반응후의 pH가 13.5 이상 되도록, 80 ℃에서 1 시간 동안 수열반응을 수행하였다.On the other hand, a strong alkali solution was prepared in a stainless steel autoclave coated with Teflon having high corrosion resistance against alkali. The strong alkali solution was added to a sodium or potassium hydroxide aqueous solution by adding a barium salt corresponding to the equivalent ratio of carbonate present as an impurity. The resulting barium carbonate is filtered to remove carbonate ions. The suspension was added to a strong alkaline aqueous solution having a pH of 14 or more, and the concentration of barium and titanium in the final solution was 0.2 M, respectively, and the hydrothermal reaction was performed at 80 ° C. for 1 hour so that the pH after the reaction was 13.5 or more.
생성된 티탄산바륨 분말을 수산화바륨이 희석된 증류수로 수세하고 원심분리기를 이용하여 10,000 rpm으로 분말만을 분리하였다. 이와 같이 수세와 분리 과정을 거친 분말을 190 ℃의 오븐에서 12 시간 동안 건조시켰다.The produced barium titanate powder was washed with distilled water diluted with barium hydroxide, and only the powder was separated at 10,000 rpm using a centrifuge. Thus washed and separated powder was dried in an oven at 190 ℃ for 12 hours.
상기한 바와 같이 제조한 티탄산바륨 분말의 주사현미경 사진을 도 1에 나타내었으며, 이로부터 본 실시예에 의해 얻어진 티탄산바륨 분말을 입자 크기가 몇십 나노미터 단위로 미세하고 고른 분포를 가지며 입자의 모양도 구형인 것을 알 수 있다. 또한, 본 실시예에 의해 얻어진 티탄산바륨 분말의 X-선 회절 분석한 결과, 순수한 티탄산바륨 결정상으로 존재함을 알 수 있었다(도 2 참조). 생성된 티탄산바륨 분말내의 바륨/티타늄의 몰비는 다음 표 1에 나타내었다.A scanning microscope photograph of the barium titanate powder prepared as described above is shown in FIG. 1. From this, the barium titanate powder obtained by the present example has a fine and even distribution in the order of several tens of nanometers and the shape of the particles. It can be seen that it is spherical. Further, as a result of X-ray diffraction analysis of the barium titanate powder obtained in the present example, it was found that it was present as a pure barium titanate crystal phase (see FIG. 2). The molar ratio of barium / titanium in the resulting barium titanate powder is shown in Table 1 below.
참고적으로, 본 실시예에 의해 얻어진 티탄산바륨 분말은 BET로 측정한 입자 크기가 30 nm였다. 즉, 본 실시예에 의해 제조된 티탄산바륨 분말의 평균 입경이 습식 합성법으로 제조된 상업용 분말의 평균 입경(500 nm)보다 훨씬 작음을 알 수 있다.For reference, the barium titanate powder obtained by this example had a particle size of 30 nm measured by BET. That is, it can be seen that the average particle diameter of the barium titanate powder prepared according to the present example is much smaller than the average particle diameter (500 nm) of the commercial powder prepared by the wet synthesis method.
실시예 2Example 2
상기 실시예 1에서와 같은 티타늄 전구체, Ti(OCH2CH2OCH3)4를 4 당량의 2-프로판올 용매에 희석한 후 티타늄 전구체의 2.2 당량에 해당하는 과량의 1 M 바륨아세테이트 수용액에 천천히 적가하고 격렬히 교반하면서 1 시간 동안 반응시켜 티타늄과 바륨이 균일하게 분산된 바륨-티타늄 복합체 현탁액을 만든 것을 제외하고는 상기 실시예 1에서와 동일한 방법으로 티탄산바륨을 제조하고 수세, 건조하였다.The titanium precursor, Ti (OCH 2 CH 2 OCH 3 ) 4 , as in Example 1 was diluted in 4 equivalents of 2-propanol solvent and slowly added dropwise to an excess of 1 M barium acetate solution corresponding to 2.2 equivalents of the titanium precursor. Barium titanate was prepared in the same manner as in Example 1 except that the mixture was reacted with vigorous stirring for 1 hour to form a barium-titanium composite suspension in which titanium and barium were uniformly dispersed, and washed with water and dried.
본 실시예에 의해 생성된 티탄산바륨내의 원소 분석 결과와 바륨/티타늄의 몰비를 다음 표 1에 나타내었다. 이로부터, 티타늄에 비해 과량의 바륨을 사용하여 티탄산바륨을 제조함으로써, 화학양론적 티탄산바륨에 좀더 근접한 바륨과 티타늄을 함유하는 티탄산바륨 분말을 얻을 수 있음을 알 수 있다.The results of elemental analysis and the molar ratio of barium / titanium in barium titanate produced by this example are shown in Table 1 below. From this, it can be seen that barium titanate powder containing barium and titanium closer to the stoichiometric barium titanate can be obtained by producing barium titanate using excess barium as compared to titanium.
또한, 도 3에서 나타난 바와 같이, 과량의 바륨을 사용하여 티탄산바륨 분말을 제조하면, 분말의 평균 입경을 감소시킬 수 있음을 알 수 있다. 제조된 분말을 X선 회절 분석한 결과, 순수한 티탄산바륨 결정상만을 함유하고 있음을 관찰하였다.In addition, as shown in Figure 3, it can be seen that when the barium titanate powder is prepared using an excess of barium, the average particle diameter of the powder can be reduced. X-ray diffraction analysis of the prepared powder revealed that it contained only a pure barium titanate crystal phase.
실시예 3Example 3
상기 실시예 1에서와 같이 바륨-티타늄 복합체의 현탁액을 강알칼리 수용액에 첨가하여 수열반응을 실시할 때, 7 기압의 압력 하에서 수행한 것을 제외하고는 실시예 1에서와 동일한 방법으로 티탄산바륨을 제조하고 수세, 건조하였다.When performing a hydrothermal reaction by adding a suspension of barium-titanium composite to a strong alkali solution as in Example 1, barium titanate was prepared in the same manner as in Example 1 except that the hydrothermal reaction was carried out under a pressure of 7 atm. Washed with water and dried.
생성된 티탄산바륨내의 바륨/티타늄의 몰비를 측정한 결과, 상기 실시예 2에서와 같이 과량의 바륨을 사용하지 않고도 수열반응시의 압력 조절만으로도, 표 1에 나타낸 바와 같이 화학량론적인 면에서 더욱 우수한 티탄산바륨 분말을 제조할 수 있음을 알 수 있다. 이 때에는, 도 4에서 보는 바와 같이 미세한 평균 입경의 증가를 관찰하였으나 화학양론적인 우수성에 비하면 이 증가는 미미한 것이라 하겠다.As a result of measuring the molar ratio of barium / titanium in the produced barium titanate, as shown in Table 2, even by adjusting the pressure during hydrothermal reaction without using excess barium, it is more excellent in stoichiometry as shown in Table 1 It can be seen that barium titanate powder can be produced. In this case, as shown in FIG. 4, the increase in the fine average particle diameter was observed, but this increase is insignificant compared to the stoichiometric excellence.
이상과 같이, 본 발명에 따르면, 티타늄 2-알콕시에톡사이드 화합물을 사용하여 바륨염을 포함한 수용액과의 반응시, 수화 반응 및 축합 반응이 진행된 후 고분자화된 티타늄 겔 대신, 화학적 변형을 위해 도입된 작용기의 입체 효과와 전자 효과 및 킬레이트 효과에 의하여 균일하게 분산된 용액을 형성하게 되어, 이 바륨-티타늄 복합체로부터 입자 모양이 구형이고 입자 크기가 균일하며 화학양론적으로 결정화된 티탄산바륨 미세 분말을 고온의 전기로를 사용할 필요 없이 비교적 낮은 온도에서 직접 제조할 수 있다. 이러한 미세분말의 제조는 이들 미세 분말을 주원료로 사용하는 고도 전자공학산업 부품의 질을 향상시키는 데 크게 기여할 것이다.As described above, according to the present invention, when reacting with an aqueous solution containing a barium salt using a titanium 2-alkoxy ethoxide compound, instead of polymerized titanium gel after the hydration reaction and condensation reaction, it is introduced for chemical modification. The uniformly dispersed solution is formed by the steric effect, the electron effect, and the chelate effect of the functional group. From this barium-titanium composite, the barium titanate fine powder is spherical in shape, uniform in particle size, and stoichiometrically crystallized. It can be manufactured directly at relatively low temperatures without the need for the use of hot furnaces. The production of such fine powders will greatly contribute to improving the quality of the high electronics industry components using these fine powders as the main raw materials.
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