Synthesis and characterization of ZnAPO-34 molecular sieve with CHA structure type

Zinc substituted chabazite-like aluminophosphate ZnAPO-34 was synthesized hydrothermally. Rietveld refinement has been carried out over the X-ray spectrum. Atomic coordinates of the framework were refined assuming the space group <(R)over bar 3m>. Results show that Zn2+, P5+ and Al3+ occupy similar tetrahedral sites in the structure. The cell is rhombohedral; in hexagonal coordinates the lattice parameters are: a=13.827(1) Angstrom and c=15.401(3) Angstrom. Different crystal shapes have been revealed by scanning electron microscopy, and the elemental compositions of these crystals show variations, especially in their Ca and Zn content, but all of them belong to the same solid solution. (C) 1998 Elsevier Science B.V. All rights reserved.