Electron diffraction patterns mordenite crystals

A previous examination of a synthetic calcium mordenite 15) revealed an orthorhombic cell. A synthetic strontium mordenite 16) had a C-centered orthorhombic cell although Kerr 12) reported that a few crystals giving electron diffraction patterns corresponding approximately to the body-centered structure Immm) have been synthesized hydro-thermally from aluminosilicate gels containing strontium similar to those gels which yielded a strontium-mordenite. ... 

Many mineral and synthetic samples examined by Bennett and Gard 17,18) gave typical C-centered orthorhombic diffraction patterns and with few exceptions had streaks in the hOl section, indicating an incomplete c-glide plane. A few crystals gave electron diffraction patterns having diffuse maxima in the hOl streaks, which could be interpreted as representing an I-centered mordenite structure. 

This is possible because the projection lens system, which for clarity was not shown in Figure 4.7, is normally included behind the objective lens and below the source image plane. This lens system allows the projection of both the diffraction pattern and the specimen image on the observation screen. In Figure 4.8, [50] the electron diffraction pattern of a Fe thin film is shown. In Figure 4.9, the transmission electron micrograph of the mordenite included in the sample CMT-C (see Table 4.1), where fiber-like crystals of mordenite are seen, is shown [51],... 

Electron diffraction patterns of heavily and weakly faulted mordenite crystals were obtained with a JEOL 100 CX transmission electron microscope fitted with a top entry two-axis tilting stage and a UHR objective pol piece (C = 0.7 mm). In this situation, electron diffraction patterns cansbe obtained from crystals tilted by about 35° from the horizontal. Experimental details have been discussed elsewhere (2). 

Figure 1. Electron diffraction patterns of several mordenite crystals. (A) Natural mordenite from Hicknoi, New Zealand,...

Electron diffraction patterns indicate that heavily and weakly faulted mordenite crystals were obtained weakly faulted mordenites patterns resemble those of commercially-available large port mordenites. The absence of odd order spots or streaks in the hOO rows of the ZSM-11 diffraction pattern has been taken as evidence of the presence of ZSM-11 crystals essentially free from ZSM-5 intergrowths. The (Na,K,T0A)ZSM-5 crystal morphology is different from that of typical (Na,TPA)ZSM-5 the relative lengths of straight and tortuous channels are interchanged (J ). 

Sr mordenite synthesized by Barrer and Marshall (16) gave the Cmcm x-ray pattern and was C-centered orthorhombic by electron diffraction. However, other electron diffraction studies, also by Kerr (12), revealed some synthetic Sr mordenite crystals of the Immm structure prepared at similar synthesis conditions. Future work should examine synthetic Sr and Ca mordenite specimens further for the possible presence of other framework structures, and correlation of structures with Sr2+/Ca2+ ion exchange selectivity. 

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