New Fluoridozirconate with the Nonstoichiometric Composition Cs1+x(H2O)1–xMgZr2F11+x·2H2O (x ≈ 0.73): Structure and Thermal Properties

Abstract

New fluoridozirconate with the nonstoichiometric composition Cs_1+x(H₂O)_1–xMgZr₂F_11+x·2H₂O (x ≈ 0.73) (I) is synthesized, its structure is determined, and the thermal behavior is analyzed. In the structure a part of F atoms is split over two positions which results in the formation of two types of coordination polyhedra around the Zr atom: Hoard dodecahedron ZrF₈ and pentagonal bipyramid ZrF₇. There are also two types of combining Zr polyhedra into chains: by sharing edges and by sharing edges and vertices. MgF₄(H₂O)₂ octahedra link infinite zirconium chains into layers. Between the layers cesium cations are located together with H₂O molecules statistically replacing a part of cesium cations. Dehydration of I occurs in the temperature range 140–400 °C and is complicated by the process of its partial pyrohydrolysis.