Effect of Phase Stabilizers on the Phase Formation and Sintering Density of $Na^+$-Beta-Alumina Solid Electrolyte

상 안정화제가 $Na^+$-Beta-Alumina 고체 전해질의 상 형성 및 소결밀도에 미치는 영향

  • Lee, Ki-Moon (Department of Materials Chemistry and Engineering, Konkuk University) ;
  • Lee, Sung-Tae (Department of Materials Chemistry and Engineering, Konkuk University) ;
  • Lee, Dae-Han (Department of Materials Chemistry and Engineering, Konkuk University) ;
  • Lee, Sang-Min (Department of Materials Chemistry and Engineering, Konkuk University) ;
  • Lim, Sung-Ki (Department of Materials Chemistry and Engineering, Konkuk University)
  • 이기문 (건국대학교 신소재공학과) ;
  • 이성태 (건국대학교 신소재공학과) ;
  • 이대한 (건국대학교 신소재공학과) ;
  • 이상민 (건국대학교 신소재공학과) ;
  • 임성기 (건국대학교 신소재공학과)
  • Published : 2012.12.10

Abstract

$Na^+$-beta-alumina solid electrolyte was synthesized by solid state reaction using $Li_2O$ and MgO as a phase stabilizer, and the effect of stabilizers on the phase formation and sintering density was investigated. In order to determine the phase fraction according to the synthesizing temperature, the molar ratio of [$Na_2O$] : [$Al_2O_3$] was fixed at 1 : 5, and calcination was conducted at temperatures between $1200{\sim}1500^{\circ}C$ for 2 h. In the $Li_2O$-$Na_2O$-$Al_2O_3$ ternary system, ${\beta}^{{\prime}{\prime}}$-alumina phase fraction considerably increased by the secondary phase transition at $1500^{\circ}C$, whereas it maintained similarly in the MgO-$Na_2O$-$Al_2O_3$ system. Additionally, the disc-type specimens of $Na^+$-beta-alumina were sintered at the temperature between $1550{\sim}1650^{\circ}C$ for 30 min, and relative sintering densities, phase changes, and microstructures were analyzed. In case of $Li_2O$-stabilized $Na^+$-beta-alumina, ${\beta}^{{\prime}{\prime}}$-phase fraction and relative density of specimen sintered at $1600^{\circ}C$ were 94.7% and 98%, respectively. Relative density of MgO-stabilized $Na^+$-beta-alumina increased with a rise in sintering temperature.

$ Na^+$-beta-alumina 고체전해질을 고상반응법을 통해 합성하였으며, 두 종류의 안정화제 $Li_2O$와 MgO가 상 형성 및 소결밀도에 미치는 영향을 비교 분석하였다. 합성온도에 따른 ${\beta}/{\beta}^{{\prime}{\prime}}$-alumina 상 분율 분석을 위해, [$Na_2O$] : [$Al_2O_3$] = 1 : 5의 고정된 몰 비에서 하소온도를 $1200{\sim}1500^{\circ}C$로 변화하여, 각각 2 h동안 하소하였다. $Li_2O$를 안정화제로 사용한 경우에는 $1500^{\circ}C$에서 2차 상 전이가 발생해 ${\beta}^{{\prime}{\prime}}$-alumina 상 분율의 증가가 나타났지만, MgO를 첨가했을 때는 하소온도에 관계없이 상 분율이 유지되었다. 또한 disc 형태의 $Na^+$-beta-alumina 샘플을 $1550{\sim}1650^{\circ}C$의 온도에서 각각 30 min 소결한 후 상대 소결밀도, 상 변화 및 미세구조를 분석하였다. $Li_2O$를 안정화제로 사용하였을 때, 소결온도 $1600^{\circ}C$에서 ${\beta}^{{\prime}{\prime}}$-상 분율과 상대밀도가 각각 94.7%와 98%로 가장 높은 값을 나타냈으며, MgO를 안정화제로 사용하였을 경우, 소결온도의 증가에 따라 상대밀도가 크게 증가하는 결과를 보였다.

Keywords

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