Synthesis and characterization of phi-type zeolites LZ-276 and LZ-277: faulted members of the ABC-D6R family of zeolites

A new zeolite, LZ-276, was synthesized in an organic (TEAOH) system by vary ing the crystallization temperature in the procedure used by Jacobs and Mar tens for the synthesis of zeolite phi. LZ-276 (with SiO2/Al2O3 = 7.8) is mo re siliceous than phi. Another silicon-rich zeolite, LZ-277 (SiO2/Al2O3 = 6 .6), was synthesized in a totally inorganic system. The similar chemical an d physical properties of LZ-276 and LZ-277 are compared with those of zeoli te phi described by Grose and Flanigen, and others. TEM [100] selected area diffraction patterns of LZ-277 can be indexed on a hexagonal unit cell wit h a=13.8 and c=15 Angstrom. Twin spots and considerable streaking parallel to {001} indicate mirror faulting along c. High resolution images on select ed crystals of LZ-277 show that the most closely spaced mirror faults occur approximately every 18 Angstrom. The bulk X-ray sample of LZ-276 is less f aulted. A close match between the experimental synchrotron X-ray powder dif fraction pattern of LZ-276 and one simulated by the DIFFaX program (with fa ulting probability = 10%) indicates that the structures of these materials can be described as a chabazite (CHA) topology with faulting along c, the s tacking direction in these ABC double sis-ring (D6R) materials. The distrib ution of interior cages, including new larger cages that result from faulti ng, is presented. (C) 1999 Elsevier Science B.V. All rights reserved.