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PTC-BaTiO3 반도체 제조용 고순도 분말의 합성
Synthesis of Fine Powder for PTC-BaTiO3
HWAHAK KONGHAK, February 1999, 37(1), 72-80(9), NONE
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Abstract
KOH용액을 광화제로 첨가하여 80-200℃의 수열반응으로부터 평균입자크기가 0.5μm이하인 입방정의 BaTiO3결정 분말을 제조하였다. 실험결과 0.2 M의 KOH를 첨가하였을 때는 아나타제(TiO2)와 비정질의 혼합상이 생성되었으며 0.8M 이상의 KOH용액을 첨가하였을 때는 안정한 BaTiO3 결정분말이 합성되었다. 광화제 첨가량이 증가함에 따라 Ba(OH)+와 Ti(OH)χ4-χ의 상대과포화도가 증가하여 핵생성속도가 증가하였고, 이로 인해 크기가 작은 결정입자가 순간적으로 많이 생성되어 평균입자크기가 작아지고 입도분포폭이 좁아졌다. 또한, 반응온도가 높을수록 Ba(OH)+와 Ti(OH)χ4-χ의 축합반응이 촉진되어 용액내에 수산화물이 감소하기 때문에 BaTiO3 결정의 응집률이 감소하였으며, 결정성장속도가 증가하여 입자크기가 커졌다.
Crystalline BaTiO3 powder of cubic phase, the mean particle site of which was 0.5 μm, was prepared by hydrothermal synthesis at temperature between 80 and 200 ℃ with KOH as a mineralizer. A mixed phase of anatase and amorphous was formed with 0.2M KOH, but a stable phase of BaTiO3 crystal powder was obtained when the concentration of KOH was 0.8M and above. As the concentration of the mineralizer increased, the relative supersaturations of Ba (OH)+ and Ti(OH)χ4-χ were enhanced. A lot of crystal powder were, therefore, formed instantaneously due to an increase in nucleation rate, and consequently, the mean particle size was reduced and the size distribution became narrower. As the reaction temperature increased, condensation reaction between Ba(OH)+ and Ti(OH)χ4-χ was accelerated, which led to a decrease in hydroxide concentration, so that agglomeration of powder was abated. However, the particle size became larger due to an increase in the crystal growth rate.
Keywords
References
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Herlt W, J. Am. Ceram. Soc., 71(10), 8779 (1988)
Ovramenko NA, Shvets LI, Ovcharenko FD, Kornilovich BY, Izv. Akad. Nauk SSSR Neorg. Mater., 15(11), 1982 (1979)
Munuera G, Eves-Amau V, Saucedo A, J. Chem. Soc.-Faraday Trans., 75, 736 (1979)
Primet M, Pichat P, Mathieu MV, J. Phys. Chem., 75, 1221 (1971)
Titani T, "Inorganic Chemistry,", 2, 427 (1988)
Arima M, J. Am. Ceram. Soc., 79(11), 2847 (1996)
Lee KJ, Chung ST, Suh KW, Korean Assoc. Cryst. Growth, 7(2), 292 (1997)
Jung ST, Seo KW, HWAHAK KONGHAK, 35(4), 520 (1997)
Lee JH, Seong HD, Won CH, Kim JJ, Korean Inst. Met. Mater., 30(7), 768 (1992)
