JP4061378B2 - Potassium niobate crystal and method for producing the potassium niobate crystal - Google Patents
Potassium niobate crystal and method for producing the potassium niobate crystal Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims description 69
- UKDIAJWKFXFVFG-UHFFFAOYSA-N potassium;oxido(dioxo)niobium Chemical compound [K+].[O-][Nb](=O)=O UKDIAJWKFXFVFG-UHFFFAOYSA-N 0.000 title claims description 53
- 238000004519 manufacturing process Methods 0.000 title claims description 28
- 238000001816 cooling Methods 0.000 claims description 40
- 239000000843 powder Substances 0.000 claims description 31
- 239000007790 solid phase Substances 0.000 claims description 19
- 230000007704 transition Effects 0.000 claims description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 14
- 239000001301 oxygen Substances 0.000 claims description 14
- 229910052760 oxygen Inorganic materials 0.000 claims description 14
- 239000012298 atmosphere Substances 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 11
- 239000010955 niobium Substances 0.000 claims description 11
- 238000003980 solgel method Methods 0.000 claims description 11
- 229910052758 niobium Inorganic materials 0.000 claims description 10
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 10
- 150000004703 alkoxides Chemical class 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- -1 potassium metal alkoxide Chemical class 0.000 claims description 9
- QOSATHPSBFQAML-UHFFFAOYSA-N hydrogen peroxide;hydrate Chemical compound O.OO QOSATHPSBFQAML-UHFFFAOYSA-N 0.000 claims description 7
- 239000007858 starting material Substances 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 3
- 238000000034 method Methods 0.000 description 12
- 239000012071 phase Substances 0.000 description 10
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 4
- 230000008025 crystallization Effects 0.000 description 4
- 239000011591 potassium Substances 0.000 description 4
- 229910052700 potassium Inorganic materials 0.000 description 4
- 238000000634 powder X-ray diffraction Methods 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical group Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000003618 dip coating Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000004972 metal peroxides Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- ZTILUDNICMILKJ-UHFFFAOYSA-N niobium(v) ethoxide Chemical compound CCO[Nb](OCC)(OCC)(OCC)OCC ZTILUDNICMILKJ-UHFFFAOYSA-N 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- RPDAUEIUDPHABB-UHFFFAOYSA-N potassium ethoxide Chemical compound [K+].CC[O-] RPDAUEIUDPHABB-UHFFFAOYSA-N 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
Description
この出願の発明は、ニオブ酸カリウムとその製造方法に関するものである。さらに詳しくは、この出願の発明は、圧電素子材料として表面弾性フィルターへの応用が期待できる、超微粉体のニオブ酸カリウムとその製造方法に関するものである。 The invention of this application relates to potassium niobate and a method for producing the same. More specifically, the invention of this application relates to an ultrafine powder of potassium niobate that can be expected to be applied to a surface elastic filter as a piezoelectric element material and a method for producing the same.
ニオブ酸カリウム結晶（ＫＮｂＯ3）は、古くから非線形光学用途としての研究が進み
、単結晶育成が試みられてきた。このニオブ酸カリウム結晶は、融点が１１３０℃と高く、固相において相転移が２ヶ所の温度で生じる。このため、たとえば、高温で単結晶を合成した後、室温まで冷却する過程において双晶等の欠陥が導入されやすく、うまく単結晶が育成できても使用できる部分はほとんどなかった。これは、多結晶体でも同様で、固相転移により結晶中にクラックが導入されてしまい、実用に耐える多結晶体を合成することは困難であった。
The potassium niobate crystal (KNbO 3 ) has been studied for nonlinear optical applications for a long time, and single crystal growth has been attempted. This potassium niobate crystal has a high melting point of 1130 ° C., and phase transition occurs at two temperatures in the solid phase. For this reason, for example, defects such as twins are easily introduced in the process of synthesizing a single crystal at a high temperature and then cooling to room temperature, and there are few parts that can be used even if the single crystal can be successfully grown. The same applies to a polycrystal, and cracks are introduced into the crystal due to solid phase transition, and it is difficult to synthesize a polycrystal that can withstand practical use.
そこで以上の問題点を解決する方法として、たとえばＫ2ＣＯ3とＮｂ2Ｏ5にアルカリ金属酸化物を加えた混合物を加熱溶解し、この高温融液に種結晶を接触させ、融液を冷却しながら結晶を育成するトップシーディング法（特許文献１）や、温度勾配を有する炉内に高温融液を入れた貴金属るつぼを移動させるか炉内を冷却するかの少なくともどちらか一方により、融液を一方向から凝固させる一方向凝固法として、温度勾配とるつぼの移動速度、冷却速度を制御した一方向凝固法（特許文献２）など各種のニオブ酸カリウム結晶の製造方法が提案されている。
しかしながら、これら方法において作製されたニオブ酸カリウム結晶を、焼結法により多結晶体を作製する場合、通常の方法では結晶粒間の結合が弱く、しかも水分を吸収しやすいため、多結晶体を放置しておくと粉末に戻ってしまうという欠点があった。さらに、ニオブ酸カリウムにおける固相転移は容易に生じるため、高温相である立方晶を室温まで冷却することは急冷法によっても困難であった。 However, when a polycrystalline body is produced by sintering the potassium niobate crystals produced by these methods, the bonding between crystal grains is weak in the ordinary method and moisture is easily absorbed. There was a drawback that it would return to powder if left untreated. Furthermore, since the solid phase transition in potassium niobate easily occurs, it is difficult to cool the cubic crystal, which is a high temperature phase, to room temperature even by a rapid cooling method.
以上のような固相転移による結晶のクラック発生の抑制や高温相である立方晶を得ることは、主に固相転移において発生する応力を制御することにより実現することができると考えられ、その制御法の開発が望まれていた。 It is considered that the suppression of crystal cracking due to the solid phase transition as described above and obtaining a cubic crystal which is a high temperature phase can be realized mainly by controlling the stress generated in the solid phase transition. Development of a control method was desired.
そこで、この出願の発明は、以上のとおりの背景から、クラックの導入を抑え、さらには焼結体生成をも可能な立方晶、斜方晶の構造をもつ微細なニオブ酸カリウム結晶（ＫＮｂＯ3）と、簡便に作製できる製造方法を提供することを課題としている。 In view of the above, the invention of this application is based on the fine potassium niobate crystal (KNbO 3 ) having a cubic or orthorhombic structure that suppresses the introduction of cracks and can also generate a sintered body. ) And providing a production method that can be easily produced.
この出願の発明は、上記の課題を解決するものとして、第１には、カリウム金属アルコキシドおよびニオブ金属アルコキシドを出発原料としたゾルゲル法によるニオブ酸カリウム結晶（ＫＮｂＯ 3）の製造方法において、前記原料に過酸化水素水を添加し、生成した粉末をニオブ酸カリウム結晶の固相転移温度以上の５００〜８００℃の温度範囲で５０〜１００ｖｏｌ％酸素雰囲気下で熱処理後、１００〜６００℃／時の範囲の一定の冷却速度で室温まで冷却することを特徴とする立方晶の構造を持つニオブ酸カリウム結晶の製造方法を提供する。
The invention of this application is to solve the above-mentioned problems. First, in the method for producing potassium niobate crystal (KNbO 3 ) by a sol-gel method using potassium metal alkoxide and niobium metal alkoxide as starting materials, Hydrogen peroxide water was added to the powder, and the resulting powder was heat-treated in a temperature range of 500 to 800 ° C. above the solid phase transition temperature of potassium niobate crystals in a 50 to 100 vol% oxygen atmosphere, and then 100 to 600 ° C./hour. A method for producing potassium niobate crystals having a cubic structure characterized by cooling to room temperature at a constant cooling rate in a range.
第２には、カリウム金属アルコキシドおよびニオブ金属アルコキシドを出発原料としたゾルゲル法によるニオブ酸カリウム結晶（ＫＮｂＯ 3）の製造方法において、前記原料に過酸化水素水を添加し、生成した粉末をニオブ酸カリウム結晶の固相転移温度以上の５００〜８００℃の温度範囲で５０〜１００ｖｏｌ％酸素雰囲気下で熱処理後、５〜５０℃／時の範囲の一定の冷却速度で室温まで冷却することを特徴とする斜方晶の構造を持つニオブ酸カリウム結晶の製造方法を提供する。
Second, in a method for producing potassium niobate crystals (KNbO 3 ) by a sol-gel method using potassium metal alkoxide and niobium metal alkoxide as starting materials, hydrogen peroxide water is added to the raw materials, and the resulting powder is converted to niobic acid. It is characterized by cooling to room temperature at a constant cooling rate in the range of 5-50 ° C./hour after heat treatment in a 50-100 vol% oxygen atmosphere at a temperature range of 500-800 ° C. above the solid phase transition temperature of potassium crystals. A method for producing potassium niobate crystals having an orthorhombic structure is provided.
第３には、カリウム金属アルコキシドおよびニオブ金属アルコキシドを出発原料としたゾルゲル法によるニオブ酸カリウム結晶（ＫＮｂＯ 3）の製造方法において、前記原料に過酸化水素水を添加し、生成した粉末をニオブ酸カリウム結晶の固相転移温度以上の５００〜８００℃の温度範囲で５０〜１００ｖｏｌ％酸素雰囲気下で熱処理後、冷却速度１００〜２００℃／時の範囲で５００℃まで冷却し、その後冷却速度５〜５０℃／時の範囲で２５０℃まで冷却、さらに冷却速度１〜５／時の範囲で室温まで冷却することを特徴とする斜方晶の構造を持つニオブ酸カリウム結晶の製造方法を提供する。
Third, in a method for producing potassium niobate crystals (KNbO 3 ) by a sol-gel method using potassium metal alkoxide and niobium metal alkoxide as starting materials, hydrogen peroxide is added to the raw materials, and the resulting powder is converted to niobic acid. After heat treatment in a 50-100 vol% oxygen atmosphere at a temperature range of 500-800 ° C above the solid phase transition temperature of the potassium crystal, it is cooled to 500 ° C at a cooling rate of 100-200 ° C / hour, and then a cooling rate of 5- Provided is a method for producing potassium niobate crystals having an orthorhombic structure characterized by cooling to 250 ° C. at a rate of 50 ° C./hour and further cooling to room temperature at a cooling rate of 1 to 5 / hour.
第４ には、ニオブ酸カリウム結晶の粒径が１０〜１００ｎｍであることを特徴とするニオブ酸カリウム結晶の製造方法を提供する。
Fourth, there is provided a method for producing potassium niobate crystals, wherein the particle diameter of the potassium niobate crystals is 10 to 100 nm.
また、この出願の発明は、第５には、上記第１から第４のいずれかの発明のニオブ酸カリウム結晶の製造方法により得られることを特徴とするニオブ酸カリウム結晶を提供する。 According to a fifth aspect of the present invention, there is provided a potassium niobate crystal obtained by the method for producing a potassium niobate crystal according to any one of the first to fourth inventions.
この出願の第１の発明のニオブ酸カリウム結晶の製造方法によれば、結晶粒の微細化により、結晶粒内に導入されるクラックが少ない立方晶の構造を持つ微細なニオブ酸カリウム結晶を得るための簡便な製造方法が提供される。 According to the method for producing potassium niobate crystals of the first invention of this application, fine potassium niobate crystals having a cubic structure with few cracks introduced into the crystal grains are obtained by refining the crystal grains. A simple manufacturing method is provided.
第２の発明によれば、結晶粒の微細化により、導入されるクラックが少ない斜方晶の構造を持つ微細なニオブ酸カリウム結晶を得るための簡便は製造方法が提供される。 According to the second invention, a simple manufacturing method for obtaining a fine potassium niobate crystal having an orthorhombic structure with few introduced cracks by refining crystal grains is provided.
第３の発明によれば、上記の効果とともにスムーズに固相転移を起こし、効率よく斜方晶の構造を持つニオブ酸カリウム結晶を得るための製造方法が提供される。 According to the third aspect of the present invention, there is provided a production method for obtaining a potassium niobate crystal having a rhombic structure efficiently by causing a solid phase transition smoothly with the above effects.
第４の発明によれば、ニオブ酸カリウム（ＫＮｂＯ3）の分解が抑制される。 According to the fourth invention, the decomposition of potassium niobate (KNbO 3 ) is suppressed.
第５の発明によれば、微細化されたニオブ酸カリウム結晶を得るための製造方法が提供される。 According to 5th invention, the manufacturing method for obtaining the refined | miniaturized potassium niobate crystal | crystallization is provided.
第６の発明によれば、結晶粒の微細化により、導入されるクラックが少なく、表面積が大きく、活性のある、焼結体生成への適用が可能な微細なニオブ酸カリウム結晶を得ることができる。 According to the sixth invention, by refining crystal grains, it is possible to obtain a fine potassium niobate crystal that can be applied to the production of a sintered body with a small number of cracks introduced, a large surface area, and activity. it can.
この出願の発明は上記のとおりの特徴をもつものであるが、以下にその実施の形態について説明する。 The invention of this application has the features as described above, and an embodiment thereof will be described below.
ニオブ酸カリウム結晶は、カリウム金属アルコキシドおよびニオブ金属アルコキシドを出発原料としたゾルゲル法によって生成された粉末を熱処理した後、冷却速度を制御することで、所望のニオブ酸カリウム結晶を得ることができる。ゾルゲル法によるニオブ酸カリウムのアモルファス粉末の生成は、ガス置換した不活性ガス雰囲気下において、カリウム金属アルコキシドおよびニオブ金属アルコキシドを、たとえばエタノール等の溶媒に混合し、過酸化水素水を添加して、１００℃以下の温度で攪拌し、その後、溶媒を蒸発させてアモルファス粉末を得る。不活性ガスは、好適にはアルゴンガスが考慮される。過酸化水素水は、加水分解のために添加され、カリウム金属アルコキシドおよびニオブ金属アルコキシドと過酸化水素水との反応により前駆体中間生成物としてカリウムおよびニオブからなる複合金属過酸化物が生成することになる。この過酸化物は、不安定であるため、水溶液の加熱により容易に微細化された粉体となる。 The potassium niobate crystal can be obtained by heat-treating a powder produced by a sol-gel method using potassium metal alkoxide and niobium metal alkoxide as a starting material, and then controlling the cooling rate to obtain a desired potassium niobate crystal. The production of amorphous powder of potassium niobate by the sol-gel method is carried out by mixing potassium metal alkoxide and niobium metal alkoxide in a solvent such as ethanol in a gas-substituted inert gas atmosphere, adding hydrogen peroxide water, Stir at a temperature of 100 ° C. or lower, and then evaporate the solvent to obtain an amorphous powder. Argon gas is preferably considered as the inert gas. Hydrogen peroxide solution is added for hydrolysis, and the reaction of potassium metal alkoxide and niobium metal alkoxide with hydrogen peroxide solution produces a composite metal peroxide consisting of potassium and niobium as a precursor intermediate product. become. Since this peroxide is unstable, it becomes a powder that is easily refined by heating an aqueous solution.
次いで、この粉体は酸素雰囲気下で熱処理される。酸素雰囲気下にすることで、ニオブ酸カリウム（ＫＮｂＯ3）の分解が抑制される。酸素濃度が低いと、カリウムが蒸発して
しまい別の相（Ｋ4Ｎｂ6Ｏ17）が生成するため、酸素濃度は５０ｖｏｌ％〜１００ｖｏｌ％の範囲にすることが好ましい。熱処理温度は、固相転移温度以下の低温で合成することが望ましいが合成速度が遅くなるため、固相転移温度以上の５００℃〜８００℃が好適な温度範囲として考慮される。熱処理時間は、１〜５時間が好適な範囲として考慮される。
The powder is then heat treated in an oxygen atmosphere. By setting it in an oxygen atmosphere, decomposition of potassium niobate (KNbO 3 ) is suppressed. When the oxygen concentration is low, potassium evaporates and another phase (K 4 Nb 6 O 17 ) is generated. Therefore, the oxygen concentration is preferably in the range of 50 vol% to 100 vol%. As for the heat treatment temperature, it is desirable to synthesize at a low temperature below the solid phase transition temperature, but since the synthesis rate becomes slow, 500 ° C. to 800 ° C. above the solid phase transition temperature is considered as a suitable temperature range. The heat treatment time is considered as a suitable range of 1 to 5 hours.
熱処理後の冷却は、１００℃〜６００℃／時の範囲の一定の冷却速度で室温まで冷却することで立方晶の構造を持つニオブ酸カリウム結晶を得ることができる。上記のように、粉体が微細であるため、固相転移時の応力発生が低減し、クラックの発生が抑制されるとともに、固相転移が抑制され、高温相のクエンチが容易に実現することができる。 Cooling after the heat treatment can obtain potassium niobate crystals having a cubic structure by cooling to room temperature at a constant cooling rate in the range of 100 ° C. to 600 ° C./hour. As mentioned above, since the powder is fine, stress generation during the solid phase transition is reduced, crack generation is suppressed, solid phase transition is suppressed, and quenching of the high temperature phase is easily realized. Can do.
また、熱処理後の冷却を、５℃〜５０℃／時の範囲の一定の冷却速度で室温まで冷却することで斜方晶の構造を持つニオブ酸カリウム結晶を得ることができる。これは、粉体が微細であるため、固相転移時の応力発生が低減し、クラックの発生が抑制されるとともに、ゆっくりと固相転移を起こしているためである。 Moreover, the potassium niobate crystal | crystallization which has an orthorhombic structure can be obtained by cooling to room temperature with the fixed cooling rate of the range of 5 to 50 degreeC / hour after heat processing. This is because, since the powder is fine, the generation of stress during the solid phase transition is reduced, the generation of cracks is suppressed, and the solid phase transition is caused slowly.
また、熱処理後の冷却を、１００〜２００℃／時の範囲で５００℃まで冷却し、その後冷却速度５〜５０℃／時の範囲で２５０℃まで冷却、さらに冷却速度１〜５℃／時の範囲で室温まで冷却することでも斜方晶の構造を持つニオブ酸カリウム結晶を得ることができる。この方法によって、立方晶から正方晶へ、正方晶から斜方晶への固相転移がスムーズに起こり、効率よく結晶を得ることができる。 Further, the cooling after the heat treatment is cooled to 500 ° C. in the range of 100 to 200 ° C./hour, then cooled to 250 ° C. in the range of the cooling rate of 5 to 50 ° C./hour, and further the cooling rate of 1 to 5 ° C./hour. Cooling to room temperature within the range can also obtain potassium niobate crystals having an orthorhombic structure. By this method, solid phase transition from cubic to tetragonal and from tetragonal to orthorhombic occurs smoothly, and crystals can be obtained efficiently.
以上の方法によって、粒径が１０〜１００ｎｍであるニオブ酸カリウム結晶の超微粉体を得る。この超微粉体は、表面積が大きいため、活性が大きいと考えられ、焼結用の原料として用いることができ、難焼結体として知られるニオブ酸カリウムの焼結体生成への適用のほか、スピンコート法、ディップコート法により容易に薄膜を形成させることも可能となる。 By the above method, an ultrafine powder of potassium niobate crystal having a particle size of 10 to 100 nm is obtained. This ultra fine powder is considered to have high activity due to its large surface area, and can be used as a raw material for sintering. Besides being applied to the production of sintered bodies of potassium niobate, which is known as a hardly sintered body, Further, it is possible to easily form a thin film by a spin coating method or a dip coating method.
以下に実施例を示し、さらに詳しくこの出願の発明について説明する。もちろん、以下の例によって発明が限定されることはない。 Examples will be shown below, and the invention of this application will be described in more detail. Of course, the invention is not limited by the following examples.
＜実施例１＞
ガス置換したアルゴン雰囲気中でエタノール３００ｍｌを溶媒とし、カリウムエトキシド（０．０１モル）、ニオブエトキシド（０．０１モル）を混合後、加水分解のための過酸化水素水を添加し、シリコ−ンオイル（信越化学工業製ＫＦ−５４）を用いたオイルバス中で、温度を７８℃に保ち、マグネットスターラーで溶液を撹拌しながらフラスコ中で
反応させる。この時、フラスコ上部には冷却管を配置し、流水で水冷する。また、フラスコ内部と通じる冷却管上部には窒素ガスを流した。
<Example 1>
In a gas-substituted argon atmosphere, 300 ml of ethanol was used as a solvent, potassium ethoxide (0.01 mol) and niobium ethoxide (0.01 mol) were mixed, hydrogen peroxide water for hydrolysis was added, and silico In an oil bath using oil oil (KF-54 manufactured by Shin-Etsu Chemical Co., Ltd.), the temperature is maintained at 78 ° C., and the solution is reacted in a flask while stirring with a magnetic stirrer. At this time, a cooling pipe is disposed at the top of the flask and is cooled with running water. Moreover, nitrogen gas was flowed to the upper part of the cooling pipe connected with the inside of a flask.
合成反応は２４時間で終了する。その後、フラスコから溶液を取り出し、溶媒を蒸発させて粉末を取り出す。粉末Ｘ線回折によると、アモルファス状態であることが確認された。粉末を酸素雰囲気中で６００℃まで加熱し、２時間保持することで熱処理を行った。その後１００℃／時で冷却し、粉末Ｘ線回折を調べると高温相である立方晶のパターンが観察された。 The synthesis reaction is completed in 24 hours. Thereafter, the solution is taken out from the flask, the solvent is evaporated, and the powder is taken out. According to powder X-ray diffraction, it was confirmed to be in an amorphous state. The powder was heated to 600 ° C. in an oxygen atmosphere and heat-treated by holding for 2 hours. Thereafter, the mixture was cooled at 100 ° C./hour and examined by powder X-ray diffraction, and a cubic pattern as a high-temperature phase was observed.
この結果を図１に示す。 The result is shown in FIG.
また、この粉末の結晶粒径は２０〜３０ｎｍと微細であった。
＜実施例２＞
実施例１と同様のゾルゲル法によって、アモルファス粉末を得た。この粉末を酸素雰囲気中で６００℃まで加熱し、２時間保持することで熱処理を行った。その後５℃／時で冷却し、粉末Ｘ線回折を調べると低温相である斜方晶のパターンが観察された。
Moreover, the crystal grain size of this powder was as fine as 20 to 30 nm.
<Example 2>
An amorphous powder was obtained by the same sol-gel method as in Example 1. This powder was heated to 600 ° C. in an oxygen atmosphere and heat-treated by holding for 2 hours. Thereafter, it was cooled at 5 ° C./hour and examined by powder X-ray diffraction, and an orthorhombic pattern as a low temperature phase was observed.
この結果を図２に示す。 The result is shown in FIG.
また、この粉末は結晶粒径は２０〜３０ｎｍと微細であった。
＜実施例３＞
実施例１と同様のゾルゲル法によって、アモルファス粉末を得た。この粉末を酸素雰囲気中で６００℃まで加熱し、２時間保持することで熱処理を行った。その後冷却速度１００〜２００℃／時で５００℃まで、冷却速度５〜５０℃／分で２５０℃まで、さらに冷却速度１〜５℃／時で室温まで冷却するという３種類の冷却速度で冷却した。粉末Ｘ線回折を調べると低温相である斜方晶のパターンが観察された。また、結晶粒径は２０〜３０ｎｍと微細であった。
＜比較例１＞
粉末の加熱処理を酸素雰囲気中から大気中に代えた以外は実施例１と同様の条件で実施した。得られた粉末の結晶粒径は２０〜３０ｎｍと微細であった。この粉末をＸ線回折で調べると立方晶単相は観察されなかった。
＜比較例２＞
ゾルゲル法において、過酸化水素水に代えて蒸留水を用いた以外は、実施例２と同様の条件で実施した。得られた粉末の結晶粒径は２０〜３０ｎｍと微細であった。この粉末をＸ線回折で調べると斜方晶単相は観察されなかった。
The powder had a fine crystal grain size of 20 to 30 nm.
<Example 3>
An amorphous powder was obtained by the same sol-gel method as in Example 1. This powder was heated to 600 ° C. in an oxygen atmosphere and heat-treated by holding for 2 hours. Thereafter, cooling was performed at three cooling rates: cooling to 100 ° C./hour to 500 ° C., cooling to 5 ° C./minute to 250 ° C., and further cooling to 1 to 5 ° C./hour to room temperature. . When examining powder X-ray diffraction, an orthorhombic pattern, which is a low-temperature phase, was observed. The crystal grain size was as fine as 20-30 nm.
<Comparative Example 1>
It was carried out under the same conditions as in Example 1 except that the heat treatment of the powder was changed from the oxygen atmosphere to the air. The crystal grain size of the obtained powder was as fine as 20 to 30 nm. When this powder was examined by X-ray diffraction, a cubic single phase was not observed.
<Comparative example 2>
The sol-gel method was carried out under the same conditions as in Example 2 except that distilled water was used instead of the hydrogen peroxide solution. The crystal grain size of the obtained powder was as fine as 20 to 30 nm. When this powder was examined by X-ray diffraction, no orthorhombic single phase was observed.
この出願の発明によって提供されるニオブ酸カリウム結晶は、弾性波フィルター用圧電素子材料、レーザー光線の波長変換用非線形光学材料への利用、中でも圧電素子材料としては、圧電定数の大きな方位が発見され、表面弾性フィルター等への応用が期待でき、産業上においても有効に活用することができる。 Potassium niobate crystals provided by the invention of this application are used for piezoelectric element materials for elastic wave filters and nonlinear optical materials for wavelength conversion of laser beams. It can be expected to be applied to surface elastic filters and can be used effectively in industry.
Claims (5)
によるニオブ酸カリウム結晶（ＫＮｂＯ 3）の製造方法において、前記原料に過酸化水素水を添加し、生成した粉末をニオブ酸カリウム結晶の固相転移温度以上の５００〜８００℃ の温度範囲で５０〜１００ｖｏｌ％酸素雰囲気下で熱処理後、５〜５０℃／時の範囲の一定の冷却速度で室温まで冷却することを特徴とする斜方晶の構造を持つニオブ酸カリウム結晶の製造方法。 In a method for producing potassium niobate crystals (KNbO 3 ) by a sol-gel method using potassium metal alkoxide and niobium metal alkoxide as starting materials, hydrogen peroxide water is added to the raw materials, and the resulting powder is converted into a solid phase of potassium niobate crystals. An orthorhombic crystal characterized by being cooled to room temperature at a constant cooling rate in the range of 5 to 50 ° C./hour after heat treatment in an oxygen atmosphere of 50 to 100 vol% in a temperature range of 500 to 800 ° C. above the transition temperature. A method for producing a potassium niobate crystal having a structure.
によるニオブ酸カリウム結晶（ＫＮｂＯ 3）の製造方法において、前記原料に過酸化水素水を添加し、生成した粉末をニオブ酸カリウム結晶の固相転移温度以上の５００〜８００℃ の温度範囲で５０〜１００ｖｏｌ％酸素雰囲気下で熱処理後、冷却速度１００〜２００℃ ／時の範囲で５００℃まで冷却し、その後冷却速度５〜５０℃／時の範囲で２５０℃まで冷却、さらに冷却速度１〜５℃／時の範囲で室温まで冷却することを特徴とする斜方晶の構造を持つニオブ酸カリウム結晶の製造方法。 In a method for producing potassium niobate crystals (KNbO 3 ) by a sol-gel method using potassium metal alkoxide and niobium metal alkoxide as starting materials, hydrogen peroxide water is added to the raw materials, and the resulting powder is converted into a solid phase of potassium niobate crystals. After heat treatment in an oxygen atmosphere of 50 to 100 vol% in a temperature range of 500 to 800 ° C. above the transition temperature, it is cooled to 500 ° C. at a cooling rate of 100 to 200 ° C./hour, and then a cooling rate of 5 to 50 ° C./hour. A method for producing potassium niobate crystals having an orthorhombic structure characterized by cooling to 250 ° C in the range and further cooling to room temperature at a cooling rate of 1 to 5 ° C / hour.
A potassium niobate crystal obtained by the method for producing a potassium niobate crystal according to any one of claims 1 to 4.
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