OBSERVATION OF SPATIALLY CORRELATED INTERGROWTHS OF FAUJASTIC POLYTYPES AND THE PURE END MEMBERS BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

Controlled intergrowths of cubic and hexagonal phases of faujasitic ma terials have been synthesized, using mixtures of crown ethers, and stu died by high-resolution electron microscopy. The results reveal that t he end-member materials are pure phases, nearly free of defects and in tergrowths such as those observed without the use of crown ethers. Mix ed phases form intergrowths, rather than overgrowths, consisting of sh ort blocks of up to 10 unit cells. In intergrowths with greater than 5 0% hexagonal phase there is a spatial correlation between these interg rowing blocks. The growth mechanism for the formation of these crystal s and the role of the crown ethers as structure directing agents is di scussed.