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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 10, Number 6
BKCSDE 10(6)
June 20, 1989 

 
Title
Two Crystal Structures of Dehydrated Sr2+ and Tl+ Exchanged Zeolite A, SrxTl12-2x-A (x=1.6 and 5.45)
Author
Weon Jeong Yang, Jong Yul Park, Un Sik Kim, Yang Kim*
Keywords
Abstract
Two crystal structures of dehydrated Sr2+ and Tl+ exchanged zeolite A, SrxTl12-2x-A (x = 1.6 and 5.45), have been determined by single-crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at 21(1)℃. Both crystals were ion exchanged in flowing streams of mixed Sr(NO3)2 and TlNO3 aqueous solution, followed by dehydration at 360℃ and 2×10-6 Torr for 2 days. Full-matrix least-squares refinements of the dehydrated Sr1.6Tl8.8-A (a = 12.214(2)Å) and Sr5.45Tl1.1-A (a = 12.291(2)Å) have converged to final error indices, R1 = 0.055 and R2 = 0.061 with 286 reflections, and R1 = 0.072 and R2 = 0.090 with 217 reflections, respectively, for which I > 3σ (I). In both structures, all Sr(Ⅱ) ions are coordinated by three framework oxygens; Sr(Ⅱ) to O(3) distances are 2.21(2)Å for Sr1.6Tl8.8-A and 2.31(1)Å for Sr5.45Tl1.1-A, and Tl(Ⅰ) to O(3) distances are 2.657(6)Å for Sr1.6Tl8.8-A and 2.845(8)Å for Sr5.45Tl1.1-A, respectively. In each structure, the angle subtended at Sr(Ⅱ), O(3)-Sr(Ⅱ)-O(3) is 118.7(4)°for Sr1.6Tl8.8-A and 120.0(4)°for Sr5.45Tl1.1-A. Sr2+ ions prefer to 6-ring sites and Tl+ ions to 8-ring sites when total number of ions per unit cell is more than 8.
Page
582 - 585
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