Crystal chemistry of natural and synthetic titanium and molybdenum oxocompounds

Abstract

Crystal chemistry of molybdates and titanates is of special interest due to the appearance of these compounds in the nuclear fuel cycle. In the present study, several synthetic and natural molybdates and titanates were investigated by means of X-ray diff raction singlecrystal structure analysis. Five novel alkali molybdates were synthesized and structurally characterised: β-Cs2Mo4O13, Cs3(Mo2O7)Br, (emim)3K(Mo8O26), (emim)3Rb(Mo8O26) and (emim)2Cs2(Mo8O26) (emim = 1-ethyl-3-methylimidazolium). Th e crystal structures of murataite-3C and -8C, members of the pyrochlore-murataite polysomatic series, have been solved. Th eir investigation provided unambiguous evidence for the modular nature of the series and explained crystallization sequence of murataite matrices from the crystal-chemical point of view. Th e structure of laachite, (Ca,Mn)2(Zr,Mn)2Nb2TiFeO14, a new mineral from the Laach See, Germany, was found to be monoclinic analogue of zirconolite-3O