Journal of the Korean Ceramic Society (한국세라믹학회지)

The Korean Ceramic Society (한국세라믹학회)
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Preparation and Characterization of Hydrothermal BaTiO3 Powders and Ceramics

수열합성법에 의한 BaTiO3분말합성 및 소결체의 제조

  • 이병우 (한국해양대학교 기계소재공학부) ;
  • 최경식 (한국해양대학교 기계소재공학부) ;
  • 신동우 (경상대학교 세라믹공학과)
  • Published : 2003.06.01
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Abstract

BaTiO$_3$ fine powders were synthesized by hydrothermal process from peroxo-coprecipitate precursors. The peroxo-coprecipitates were obtained by addition of the BaCl$_2$, TiCl$_4$, and $H_2O$$_2$ aqueous solution to an ammonium solution. Hydrothermal reaction was conducted at various reaction temperatures, times and pH ranges. Unlike the conventional hydrothermal synthesis which needs highly alkaline condition over pH 13 with KOH or NaOH, the present method offered well-developed crystalline (perovskite) BaTiO$_3$ powders synthesized below pH 12 with use of ammonium solution. It was found that the phase-pure fine powders were formed at temperatures as low as 11$0^{\circ}C$ and the properties of the powders synthesized over 13$0^{\circ}C$ were almost same regardless of the reaction time. BET surface area of the prepared powder was as high as 76 $m^2$/g and the calculated particle (particulate) size was below 20 nm. The ultrafine particulates formed weak agglomerates. The microstructure and dielectric properties of BaTiO$_3$ ceramics sintered at the temperature range of 1150~125$0^{\circ}C$ were evaluated.

공침전물을 원료로 사용한 수열합성법을 통해 저온에서 미립의 BaTiO$_3$ 분말을 합성하였다. 출발물질로는 BaCl$_2$와 TiCl$_4$ 의 수용액을 사용하였다 이들의 혼합용액을 제조한 다음 과산화물 형태의 침전을 얻기 위해 과산화수소수($H_2O$$_2$)를 첨가하였으며 이렇게 준비된 용액을 암모니아수에 적하하여 공침전물을 얻었다. 이 과산화공침전물을 수열합성의 원료로 사용하였으며 반응온도와 시간 및 pH를 달리하면서 합성하였다. pH 13 이상이 요구되어 강염기인 KOH나 NaOH를 사용하는 일반적인 수열합성법과 달리 암모나아수로도 얻을 수 있는 pH 12 이하에서 perovskite BaTiO$_3$가 합성되었으며, 11$0^{\circ}C$ 이상에서 균일하고 미세한 BaTiO$_3$ 분말을 합성할 수 있었다. 13$0^{\circ}C$ 이상에서 얻은 분말의 경우 합성시간과 관계없이 일정한 물성을 보여주었다. 이렇게 합성된 분말은 76 $m^2$/g의 높은 비표면적을 보였으며 20 nm 이하의 미세한 일차입자들이 약하게 결합된 응집체를 이루고 있었다. 수열합성분말을 이용하여 l150~120$0^{\circ}C$의 온도범위에서 소결한 시편의 소결특성 및 유전 물성을 평가하였다.

Keywords

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