Transmission electron microscopic study of reduced Ca2UO5

Structural changes of Ca₂UO₅ during reduction in hydrogen were studied by transmission electron microscopy. It was shown that monoclinic Ca₂UO₅ changes into triclinic Ca₄U₂O₉. They are related, respectively, to the fluorite and the CM₂O₃structures, so that the product is a superstructure of the latter. Reduction occurs along the (100)_t planes originating from the (006)_m planes of the parent structure by diminishing the coordination number of the Ca cation from 7 to 6.