The Korean Journal of Ceramics

The Korean Ceramic Society (한국세라믹학회)
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A Study on the Ordering of Na Ions in $Na_xWO_3(0.5{\leq}x{\leq}1.0)$

  • Na, Jong-Chul (Department of Materials Science and Engineering, Korea University) ;
  • Sahn Nahm (Department of materials Science and Engineering, Korea University) ;
  • Kim, Myong-Ho (Department of Materials Science and Engineering, Changwon National University) ;
  • Lee, Hyack-Joo (New Materials Evauation Center, Korea Research Institute of Standards and Science) ;
  • Byun, Jae-Dong (Department of Materials Science and Engineering, Korea University)
  • Published : 1996.09.01
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Abstract

Cry structures of $Na_xWO_3$ (0.5$\leq$x$\leq$1.0) were investigated. Transmission electron microscopy (TEM) studies indicate that there is an ordering of sodium ions when x=0.75. The direction of ordering is [110] and the wavelength of ordering is twice of the interplanar distance of (110) plane. It has been confirmed that a superlattice containing eight $Na_{0.75}WO_3$ is the unit cell of ordered structure. In this unit cell, Na sites at (000) and ($\frac{2}{1}\frac{2}{1}\frac{2}{1}$) are vacant. The ordered phase was preserved after the annealing at $600^{\circ}C$ in the air. In reduced $Na_xWO_3$ with x=0.5 and 1.0, extra phases were found with the partially ordered perovskite phase. After annealing at $600^{\circ}C$, theses phases transformed to the phases found in calcined specimens.

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References

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