Microscopic Evidence of a New 9R-AgI Polytype Heterostructure

Abstract

The extraordinary high ionic conductivity and the phase transition with large thermal hysteresis of Agl:Al(2)O(3) nanocomposites can be ascribed to the presence of unusual polytype 7H and 9R modification of Agl as mesoscopic heterostructures. In addition to the 7H Agl phase in the composites previously identified by a Rietveld analysis of X-ray diffraction, a new 9R Agl polytype with a characteristic three-fold contrast was directly evidenced by high resolution transmission electron microscopy. The epitaxial intergrowth of various polytypes was also microscopically evidenced which is in accordance with the Rietveld analysis.