JPH0421524A - Purification of potassium tantalum fluoride - Google Patents
Purification of potassium tantalum fluorideInfo
- Publication number
- JPH0421524A JPH0421524A JP12302190A JP12302190A JPH0421524A JP H0421524 A JPH0421524 A JP H0421524A JP 12302190 A JP12302190 A JP 12302190A JP 12302190 A JP12302190 A JP 12302190A JP H0421524 A JPH0421524 A JP H0421524A
- Authority
- JP
- Japan
- Prior art keywords
- solution
- tantalum fluoride
- potassium
- tantalum
- potassium tantalum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- APLLYCDGAWQGRK-UHFFFAOYSA-H potassium;hexafluorotantalum(1-) Chemical compound [F-].[F-].[F-].[F-].[F-].[F-].[K+].[Ta+5] APLLYCDGAWQGRK-UHFFFAOYSA-H 0.000 title claims abstract description 30
- 238000000746 purification Methods 0.000 title description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 8
- 239000002253 acid Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 239000000243 solution Substances 0.000 abstract description 13
- 238000002844 melting Methods 0.000 abstract description 9
- 229910052751 metal Inorganic materials 0.000 abstract description 9
- 239000002184 metal Substances 0.000 abstract description 9
- 230000008018 melting Effects 0.000 abstract description 8
- 230000002285 radioactive effect Effects 0.000 abstract description 8
- 239000013078 crystal Substances 0.000 abstract description 3
- 239000012670 alkaline solution Substances 0.000 abstract description 2
- 239000011259 mixed solution Substances 0.000 abstract 1
- 239000010408 film Substances 0.000 description 11
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 9
- 229910052715 tantalum Inorganic materials 0.000 description 8
- WVEIBSXNFJMONP-UHFFFAOYSA-N [Ta].[K] Chemical compound [Ta].[K] WVEIBSXNFJMONP-UHFFFAOYSA-N 0.000 description 6
- 239000012535 impurity Substances 0.000 description 6
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- 239000004065 semiconductor Substances 0.000 description 6
- 229910001936 tantalum oxide Inorganic materials 0.000 description 6
- 150000002739 metals Chemical class 0.000 description 5
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 229910052776 Thorium Inorganic materials 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- VVTSZOCINPYFDP-UHFFFAOYSA-N [O].[Ar] Chemical compound [O].[Ar] VVTSZOCINPYFDP-UHFFFAOYSA-N 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 235000003270 potassium fluoride Nutrition 0.000 description 1
- 239000011698 potassium fluoride Substances 0.000 description 1
- -1 radioactive elements Chemical class 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- YRGLXIVYESZPLQ-UHFFFAOYSA-I tantalum pentafluoride Chemical class F[Ta](F)(F)(F)F YRGLXIVYESZPLQ-UHFFFAOYSA-I 0.000 description 1
- PBCFLUZVCVVTBY-UHFFFAOYSA-N tantalum pentoxide Inorganic materials O=[Ta](=O)O[Ta](=O)=O PBCFLUZVCVVTBY-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Abstract
Description
【発明の詳細な説明】
本発明は、高純度弗化タンタルカリウムの製造方法に関
するものであり、特には半導体デバイス用のタンタル酸
化膜の形成に用いられる高純度タンタルの原料の製造方
法に関する。本発明の弗化タンタルカリウムは半導体デ
バイスに有害な作用を与える不純物が榛微量にまで低減
されており、半導体デバイスにおける絶縁膜として用い
られる高純度タンタル製造のための原料として非常に好
適である。更に本発明の弗化タンタルカリウムはＬＳＩ
電極膜用として用いられる高純度タンタル製造のための
原料としても好適である。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-purity potassium tantalum fluoride, and particularly to a method for producing a raw material for high-purity tantalum used for forming a tantalum oxide film for semiconductor devices. The potassium tantalum fluoride of the present invention has impurities harmful to semiconductor devices reduced to a trace amount, and is very suitable as a raw material for producing high-purity tantalum used as an insulating film in semiconductor devices. Further, the potassium tantalum fluoride of the present invention is LSI
It is also suitable as a raw material for producing high-purity tantalum used for electrode films.
茜ユＬ貧米且困
従来、半導体デバイスにおける電接配線層間の絶縁膜と
してはシリコン酸化膜か用いられてきたが、ＬＳＩの高
集積化に伴う絶縁膜の薄膜化のためにはシリコン酸化膜
では性能不足となり、もっと誘電率の高いタンタル酸化
膜を用いようとする試みが盛んに行なわている。また、
大容量ＭＯ３ＤＲＡＭのキャパシタ用誘電体として高誘
電率のＴａ、０６に現在大きな注目が集められている。Traditionally, silicon oxide films have been used as insulating films between electrical connection wiring layers in semiconductor devices, but silicon oxide films have been used to thin insulating films as LSIs become more highly integrated. However, the performance is insufficient, and many attempts are being made to use tantalum oxide film, which has a higher dielectric constant. Also,
Ta, 06, which has a high dielectric constant, is currently attracting a lot of attention as a dielectric material for capacitors in large-capacity MO3DRAMs.
こうしたＴａ、０６膜は代表的にタンタル製ターゲット
をアルゴン−酸素混合ガス中でスパッタすることにより
形成されるが、スパッタＴａ、Ｏ，薄膜は膜中に多くの
トラップ中心を含むためリーク電流が流れやすい。リー
ク電流の原因としては、残留不純物がその主たるものと
して考えられている。Such Ta, 06 films are typically formed by sputtering a tantalum target in an argon-oxygen mixed gas, but sputtered Ta, 0, thin films contain many trap centers in the film, so leakage current flows. Cheap. Residual impurities are considered to be the main cause of leakage current.
更に、半導体デバイス素子の性能の信頼性を向上するた
めには
１）Ｎａ、に、Ｌｊ等のアルカリ金属
２）Ｕ、Ｔｈ等の放射性元素
３）Ｆｅ、Ｃｒ、Ｎｉ、Ｍｎ等の遷移金属４）Ｎｂ、Ｗ
、Ｍｏ、Ｚ ｒ等の高融点金属のような不純物の低減化
が必要である。上記（１）（３）は後のＴａ処理工程で
除去可能であるため問題はないが、上記（２）、（４）
は除くことができないため、予め除去しておくことが望
ましい。Ｎａ等のアルカリ金属は、ゲート絶縁膜中を容
易に移動し界面特性を劣化させ、またＵ等の放射性元素
は、該元素より放出するα線によって素子の動作信頼性
に致命的影響を与える。Ｆｅ等の遷移金属は、動作の信
頼性を阻害する。Ｗ等の高融点金属は、リーク電流の増
大をもたらす。これらの理由からアルカリ金属及び放射
性元素ならびに遷移金属、高融点金属等の不純物の低減
化がＶＬＳＩ構成材料としての使用における基本である
。Furthermore, in order to improve the reliability of the performance of semiconductor device elements, it is necessary to use 1) alkali metals such as Na, Lj, etc., 2) radioactive elements such as U and Th, 3) transition metals such as Fe, Cr, Ni, Mn, etc. ) Nb, W
It is necessary to reduce impurities such as high melting point metals such as , Mo, and Zr. There is no problem with the above (1) and (3) because they can be removed in the later Ta treatment process, but the above (2) and (4)
cannot be removed, so it is desirable to remove them in advance. Alkali metals such as Na easily move in the gate insulating film and deteriorate interface characteristics, and radioactive elements such as U have a fatal effect on the operational reliability of the device due to alpha rays emitted from the elements. Transition metals such as Fe inhibit operational reliability. High melting point metals such as W cause an increase in leakage current. For these reasons, reduction of impurities such as alkali metals, radioactive elements, transition metals, and high-melting point metals is fundamental for use as VLSI constituent materials.
しかし、このタンタルあるいはタンタル酸化物製造のた
めの原料として用いられる市販の弗化タンタルカリウム
の純度は、Ｎｂ、 Ｍｏ、Ｗ、Ｚｒ等の不純物が数十
ｐｐｍ以上あり、好ましいものではなかった。さらに、
弗化タンタルカリウムの原料として通常用いられるＴａ
、０６の純度に大きく影響されてしまい、最終的なタン
タルあるいはタンタル酸化物の純度の保証及び向上は望
めなかった。However, the purity of commercially available potassium tantalum fluoride used as a raw material for the production of tantalum or tantalum oxide was not preferable, as it contained impurities such as Nb, Mo, W, and Zr in an amount of several tens of ppm or more. moreover,
Ta, commonly used as a raw material for potassium tantalum fluoride
, 06, and it was not possible to guarantee or improve the purity of the final tantalum or tantalum oxide.
このため、純度のよい高純度タンタルあるいはタンタル
酸化物を製造するための原料、特に弗化タンタルカリウ
ムを高純度化する方法が要望されていた。For this reason, there has been a need for a method for highly purifying raw materials for producing high-purity tantalum or tantalum oxide, particularly potassium tantalum fluoride.
そこで、本発明者等が鋭意検討した結果、以下の発明が
なされた。Therefore, as a result of intensive study by the present inventors, the following invention was made.
叉ユニ！疾
即ち、本発明は、
１）粗部化タンタルカリウムを弗化水素酸或いは弗化水
素酸を含む混酸に投入し、該溶液を５０〜９５℃に昇温
し、その後２０℃以下に冷却することを特徴とする弗化
タンタルカリウムの精製方法。Uni! That is, the present invention comprises: 1) Putting crude tantalum potassium into hydrofluoric acid or a mixed acid containing hydrofluoric acid, heating the solution to 50 to 95°C, and then cooling it to 20°C or less. A method for purifying potassium tantalum fluoride, characterized by:
２）溶液中の弗化水素酸濃度が５〜３０ｗし％であるこ
とを特徴とする第１項記載の方法。である。2) The method according to item 1, wherein the concentration of hydrofluoric acid in the solution is 5 to 30% by weight. It is.
［（の目 酬−１
本発明の対象となる粗部化タンタルカリウムは、高融点
金属特にＮｂが５〜６０ｐｐｍＷが２〜４０ｐｐｍ、Ｍ
ｏが２〜１０ｐｐｍ、Ｚｒが１〜１０ｐｐｍ、放射性元
素においては、Ｕが１〜２０ｐｐｂ、Ｔｈか１〜１ｏｐ
ｐｂ含有されている。[(Objectives)-1 The roughened tantalum potassium that is the object of the present invention contains a high melting point metal, especially Nb, of 5 to 60 ppm, W of 2 to 40 ppm, M
O is 2 to 10 ppm, Zr is 1 to 10 ppm, and in radioactive elements, U is 1 to 20 ppb, Th is 1 to 1 op.
Contains PB.
これら高融点金属及び放射性金属の除去には、湿式精製
を実施しなければならない。まず、粗部化タンタルカリ
ウムを溶解する手段として、鋭意探索した結果、弗化水
素酸あるいはその混酸が有効であることを見い出した。Wet refining must be performed to remove these high melting point metals and radioactive metals. First, as a means of dissolving crude tantalum potassium, as a result of intensive research, it was discovered that hydrofluoric acid or a mixed acid thereof is effective.
溶液中の弗化水素酸の濃度としては、第１図に示す如く
５〜３０ ｗ ｔ％が好ましい。これは、溶液中の弗化
水素酸の濃度が５％より少い場合は温度を上げても弗化
タンタルカリウムの溶解量が少ないためである。３０ｗ
Ｌ％以上では、温度２０℃での弗化タンタルカリウムの
溶解量がかなりあるため、冷却後の弗化タンタルカリウ
ムの収率が落ちるからである。溶解温度も５０℃〜９５
℃が好ましく、より好ましい温度は７０℃〜９５℃であ
る。溶解温度が」１記の温度より低い場合は、粗部化タ
ンタルカリウムの溶解性が劣り、収率に影響するからで
ある。溶解温度が９５℃より高い場合は、弗化水素酸溶
液の蒸発か激しくなり、最終的には粗部化タンタルカリ
ウムの溶解性が悪くなるからである。次にこの合邦化タ
ンタル溶液を２０℃以下に冷却することにより、弗化タ
ンタルカリウム再結晶か晶出してくる。The concentration of hydrofluoric acid in the solution is preferably 5 to 30 wt% as shown in FIG. This is because when the concentration of hydrofluoric acid in the solution is less than 5%, the amount of potassium tantalum fluoride dissolved is small even if the temperature is raised. 30w
This is because if the temperature exceeds L%, the amount of potassium tantalum fluoride dissolved at a temperature of 20° C. is considerable, and the yield of potassium tantalum fluoride after cooling decreases. The melting temperature is also 50℃~95℃
The temperature is preferably 70°C to 95°C. This is because if the dissolution temperature is lower than the temperature listed in item 1, the solubility of the crude tantalum potassium will be poor, which will affect the yield. This is because if the dissolution temperature is higher than 95° C., the hydrofluoric acid solution will evaporate violently, and the solubility of the crude tantalum potassium will eventually deteriorate. Next, by cooling this tantalum fluoride solution to 20° C. or lower, potassium tantalum fluoride recrystallizes.
弗化タンタルカリウム再結晶をＩ適役、好ましくはアル
カリ性溶液例えばｐＨ９以上である溶液で、ｐＨが５〜
６になるまで充分に洗浄する。これは、乾燥工程で使用
される乾燥機の腐食を防止するためである。次いで１４
０〜３００℃で弗化タンタルカリウム再結晶を乾燥する
。Potassium tantalum fluoride is recrystallized in a suitable solution, preferably in an alkaline solution, such as a solution with a pH of 9 or higher, with a pH of 5 to 5.
Wash thoroughly until it reaches 6. This is to prevent corrosion of the dryer used in the drying process. then 14
Dry the recrystallized potassium tantalum fluoride at 0-300°C.
このようにして、得られた弗化タンタルカリウム再結晶
の収率は９５％以上である。The yield of potassium tantalum fluoride recrystallized thus obtained is 95% or more.
このように、温度による弗化タンタルカリウムの溶解度
差を利用したたけで容易に高純度の弗化タンタルカリウ
ムが得られる。In this way, highly pure potassium tantalum fluoride can be easily obtained by utilizing the difference in solubility of potassium tantalum fluoride depending on temperature.
更に精製が切望される場合は、上記の方法を繰り返す。If further purification is desired, repeat the above method.
［実施例］
市販の粗部化タンタルカリウム２．５に、ｇ（表１に示
す。）を採取し、高純度の５０％弗化水素酸１０ｋｇと
共に、テフロン製反応層内で温度９５℃でｌｈｒ撹拌し
つつ溶解して、含タンタル水溶液を得た。[Example] 2.5 g (shown in Table 1) of commercially available crude tantalum potassium was collected and heated at 95°C in a Teflon reaction bed with 10 kg of high-purity 50% hydrofluoric acid. The mixture was dissolved while stirring for 1 hour to obtain a tantalum-containing aqueous solution.
次に、２０℃以下まで溶液の温度を落として、弗化タン
タルカリウムを再結晶させた。その後、テフロン製炉布
を用い炉別分離し、弗化タンタルカリウム結晶を弗化カ
リウム濃度１００ｇ／Ｑの水溶液で洗浄した。ついで、
弗化タンタルカリウムを１６０℃で乾燥させた。こうし
て得られた高純度弗化タンタルカリウムは２．４ｋｇで
あり、また表１に示すごとく高融点金属含有量がｌｐｐ
ｍ以下、放射性元素含有量が１ ｐｐｂ以下の高品位の
ものである。Next, the temperature of the solution was lowered to 20° C. or lower to recrystallize potassium tantalum fluoride. Thereafter, the mixture was separated into separate furnaces using a Teflon furnace cloth, and the potassium tantalum fluoride crystals were washed with an aqueous solution having a potassium fluoride concentration of 100 g/Q. Then,
Potassium tantalum fluoride was dried at 160°C. The amount of high purity potassium tantalum fluoride thus obtained was 2.4 kg, and as shown in Table 1, the high melting point metal content was 1pp.
It is of high quality with a radioactive element content of 1 ppb or less.
この弗化タンタルカリウムを用いてタンタルあるいは五
酸化タンタルを製造するならば、有害不純物を含まない
ので使用される半導体デバイスの高い性能及び動作信頼
性を保証することかできる。If tantalum or tantalum pentoxide is produced using this potassium tantalum fluoride, high performance and operational reliability of the semiconductor devices used can be guaranteed because it does not contain harmful impurities.
表
（ｐｐｍ）
套訓ＷΣ弧果
高融点金属、放射性元素の少ない高純度の弗化タンタル
カリウムが、高収率でかつ簡単な工程で容易に得られる
。Table (ppm) Instructions WΣArchid Highly pure potassium tantalum fluoride, which is a high melting point metal and contains few radioactive elements, can be easily obtained in high yield and through a simple process.
４、垣画ｍ←（託咀
第１図は本発明における弗化水素酸濃度変化と各温度に
よる弗化タンタルカリウムの溶解量である。4. Frame m ← (Figure 1 shows the change in hydrofluoric acid concentration and the amount of potassium tantalum fluoride dissolved at each temperature in the present invention.
Claims (1)
素酸を含む混酸に投入し、該溶液を５０〜９５℃に昇温
し、その後２０℃以下に冷却することを特徴とする弗化
タンタルカリウムの精製方法。 ２）溶液中の弗化水素酸濃度が５〜３０ｗｔ％であるこ
とを特徴とする第１項記載の方法。[Claims] 1) Adding crude potassium tantalum fluoride to hydrofluoric acid or a mixed acid containing hydrofluoric acid, heating the solution to 50 to 95°C, and then cooling it to 20°C or less. A method for purifying potassium tantalum fluoride, characterized by: 2) The method according to item 1, wherein the concentration of hydrofluoric acid in the solution is 5 to 30 wt%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12302190A JPH0421524A (en) | 1990-05-15 | 1990-05-15 | Purification of potassium tantalum fluoride |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12302190A JPH0421524A (en) | 1990-05-15 | 1990-05-15 | Purification of potassium tantalum fluoride |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0421524A true JPH0421524A (en) | 1992-01-24 |
Family
ID=14850264
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12302190A Pending JPH0421524A (en) | 1990-05-15 | 1990-05-15 | Purification of potassium tantalum fluoride |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0421524A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001047813A1 (en) * | 1999-12-28 | 2001-07-05 | Mitsui Mining & Smelting Co., Ltd. | Method for producing fluorinated potassium tantalate crystal and fluorinated potassium tantalate crystal |
| WO2002083568A1 (en) * | 2001-04-06 | 2002-10-24 | Mitsui Mining & Smelting Co.,Ltd. | Method for producing high purity potassium fluorotantalate crystal or high purity potassium fluoroniobate crystal and recrystallization vessel for use in the method for production, and potassium fluorotantalate crystal or high purity potassium fluoroniobate crystal produced by the method for production |
| WO2003072504A1 (en) * | 2002-02-27 | 2003-09-04 | Stella Chemifa Kabushiki Kaisha | Purification method for producing high purity niobium compound and/or tantalum compound |
| WO2003072503A1 (en) * | 2002-02-27 | 2003-09-04 | Stella Chemifa Kabushiki Kaisha | Method of purifying niobium compound and/or tantalum compound |
| KR100425795B1 (en) * | 2001-06-02 | 2004-04-03 | 태원필 | Synthesis of nanosized potassium tantalum oxide(KTaO3) sol-particle |
| US6863750B2 (en) | 2000-05-22 | 2005-03-08 | Cabot Corporation | High purity niobium and products containing the same, and methods of making the same |
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| JPS56125217A (en) * | 1980-02-12 | 1981-10-01 | Starck Hermann C Fa | Manufacture of alkali subearth-acid metallic fluoride complex |
| JPS5734026A (en) * | 1980-08-01 | 1982-02-24 | Showa K B I Kk | Production of high-purity potassium fluorotantalate |
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1990
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|---|---|---|---|---|
| JPS4932897A (en) * | 1972-07-27 | 1974-03-26 | ||
| JPS56125217A (en) * | 1980-02-12 | 1981-10-01 | Starck Hermann C Fa | Manufacture of alkali subearth-acid metallic fluoride complex |
| JPS5734026A (en) * | 1980-08-01 | 1982-02-24 | Showa K B I Kk | Production of high-purity potassium fluorotantalate |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2001047813A1 (en) * | 1999-12-28 | 2001-07-05 | Mitsui Mining & Smelting Co., Ltd. | Method for producing fluorinated potassium tantalate crystal and fluorinated potassium tantalate crystal |
| DE10085177B4 (en) * | 1999-12-28 | 2004-01-08 | Mitsui Mining & Smelting Co., Ltd. | Process for producing potassium tantalate crystals and potassium fluorotantalate crystals produced thereby |
| US6764669B2 (en) | 1999-12-28 | 2004-07-20 | Mitsui Mining & Smelting Co., Ltd. | Method for producing fluorinated potassium tantalate crystal |
| US6863750B2 (en) | 2000-05-22 | 2005-03-08 | Cabot Corporation | High purity niobium and products containing the same, and methods of making the same |
| WO2002083568A1 (en) * | 2001-04-06 | 2002-10-24 | Mitsui Mining & Smelting Co.,Ltd. | Method for producing high purity potassium fluorotantalate crystal or high purity potassium fluoroniobate crystal and recrystallization vessel for use in the method for production, and potassium fluorotantalate crystal or high purity potassium fluoroniobate crystal produced by the method for production |
| US6860941B2 (en) | 2001-04-06 | 2005-03-01 | Mitsui Mining & Smelting Co., Ltd. | Method for manufacturing high-purity potassium fluoroniobate crystal, recrystallization bath used in manufacturing method thereof and high-purity potassium fluorotantalate crystal or high-purity potassium fluoroniobate crystal obtained by manufacturing method thereof |
| KR100425795B1 (en) * | 2001-06-02 | 2004-04-03 | 태원필 | Synthesis of nanosized potassium tantalum oxide(KTaO3) sol-particle |
| WO2003072504A1 (en) * | 2002-02-27 | 2003-09-04 | Stella Chemifa Kabushiki Kaisha | Purification method for producing high purity niobium compound and/or tantalum compound |
| WO2003072503A1 (en) * | 2002-02-27 | 2003-09-04 | Stella Chemifa Kabushiki Kaisha | Method of purifying niobium compound and/or tantalum compound |
| US7214362B2 (en) | 2002-02-27 | 2007-05-08 | Stella Chemifa Kabushiki Kaisha | Purification method for producing high purity niobium compound and/or tantalum compound |
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