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KMID : 1059519930370010076
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Journal of the Korean Chemical Society
1993 Volume.37 No. 1 p.76 ~ p.82
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Two Crystal Structures of Dehydrated Ca2+- and Tl+-Exchanged Zeolite A, CaxTl12-2x-A (x = 1.4 and 5.6)
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Kim Duk-Soo
Song Seung-Hwan
Kim Yang
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Abstract
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Two crystal structures of fully dehydrated Ca(Ⅱ) and Tl(Ⅰ) exchanged zeolite A, Ca5.6Tl0.8-A (a = 12.242(2) Å) and Ca1.4Tl9.2-A (a = 12.191(l) Å), have been determined by single-crystal X-ray diffraction methods in the cubic space group Pm3m at 21(1)℃. All crystals were ion exchanged in flowing streams of mixed Ca(NO3)2 and TlNO3 aqueous solution with total concentration of 0.05M. All crystals were dehydrated at 360℃ under 2× 10-6 torr for two days. The structures of the dehydrated Ca5.6Tl0.8-A and Ca1.4Tl9.2-A were refined to the final error indicies, R1 = 0.072 and R2 = 0.076 with 179 reflections for I > 3σ(I), and R1 = 0.048 and R2 = 0.043 with 226 reflections for I > 3σ(I), respectively. In each structure, Ca(Ⅱ) ions are located on threefold axes associated with three 6-ring oxygens. Ca2+ ions prefer to 6-ring sites and Tl+ ions prefer to 8-ring sites when total number of exchanged cations per unit cell is more than 8.
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