2, Center for Hierarchical Wasteform Materials, Columbia, South Carolina, United States
A practical working definition of a hierarchical structure is that of a structural motif contained within a larger structure or framework. Salt Inclusion Materials (SIMs) are a subset of a unique family of crystalline hierarchical structure types that are noteworthy because as a “stuffed” porous material, this type of hierarchical material is of fundamental interest in the development of new waste forms. These materials are of the general formula [AmBnX][(UO2)p(MqOr)t] where [(UO2)p(MqOr)t] is the framework consisting of uranyl, UO22+, and MqOr (M = Si, Ge) units, where BnX is the salt-inclusion and A are alkali or alkaline earth cations that are not part of the salt-inclusion. The presentation will focus on the synthesis, crystal growth, structures and potential use of a SIMs, including [Cs3F][(UO2)(Si4O10)], [Cs2Cs5F][(UO2)2(Si6O17)], [Cs9Cs6Cl][(UO2)7(Si6O17)2(Si4O12)], [Cs2Cs5F][(UO2)3(Si2O7)2], and several isostructural germanates, with special emphasis on the overall crystal chemistry of these phases. The synthesis and structural characterization of a series of new phosphates and borates will also be presented.