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 varying the crystallization temperature in the procedure used by Jacobs and Martens for the synthesis of zeolite phi. LZ-276 (with SiO₂/Al₂O₃=7.8) is more siliceous than phi. Another silicon-rich zeolite, LZ-277 (SiO₂/Al₂O₃=6.6), was synthesized in a totally inorganic system. The similar chemical and physical properties of LZ-276 and LZ-277 are compared with those of zeolite 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 with a=13.8 and c=15 Å. Twin spots and considerable streaking parallel to {00l} indicate mirror faulting along c. High resolution images on selected crystals of LZ-277 show that the most closely spaced mirror faults occur approximately every 18 Å. The bulk X-ray sample of LZ-276 is less faulted. A close match between the experimental synchrotron X-ray powder diffraction pattern of LZ-276 and one simulated by the DIFFaX program (with faulting probability=10%) indicates that the structures of these materials can be described as a chabazite (CHA) topology with faulting along c, the stacking direction in these ABC double six-ring (D6R) materials. The distribution of interior cages, including new larger cages that result from faulting, is presented.