MURATAITE CERAMICS: A COMPLEX MATRIX FOR COMPLEX RADIOACTIVE WASTE

Murataite ceramics are perspective materials for the long-term immobilization of high level radioactive waste. These materials belong to the pyrochlore-murataite polysomatic series. Their crystal structures are of outstanding complexity and contain up to forty symmetrically independent cation sites. The crystal structures are based upon three-dimensional octahedral frameworks that can be described as combinations of murataite and pyrochlore modules immersed into transitional substructures that combine elements of the crystal structures of natural murataite and pyrochlore. The obtained structural models reveal the polysomatic nature of the pyrochlore-murataite series and illuminate the chemical and structural peculiarities of crystallization of the murataite-type titanate ceramic matrices. The high chemical and structural complexity of the members of the pyrochlore-murataite series is unparalleled in the world of crystalline materials proposed for the high-level radioactive waste immobilization, which makes them unique and promising for further technological and scientific exploration.