Understanding of the structural chemistry in the uranium oxo-tellurium system under HT/HP conditions

The study of phase formation in the U-Te-O systems with mono and divalent cations under high-temperature high-pressure (HT/HP) conditions has resulted in four new inorganic compounds: K(2) [(UO(2)) (Te(2)O(7))], Mg [(UO(2)) (TeO(3))(2)], Sr [(UO(2)) (TeO(3))(2)] and Sr [(UO(2)) (TeO(5))]. Tellurium occurs as Te(IV), Te(V), and Te(VI) in these phases which demonstrate the high chemical flexibility of the system. Uranium VI) adopts a variety of coordinations, namely, UO(6) in K(2) [(UO(2)) (Te(2)O(7)), UO(7) in Mg [(UO(2)) (TeO(3))(2)] and Sr [(UO(2)) (TeO(3))(2)], and UO(8) in Sr [(UO(2)) (TeO(5))]. The structure of K(2) [(UO(2)) (Te(2)O(7))] is featured with one dimensional (1D) [Te(2)O(7)](4-) chains along the c-axis. The Te(2)O(7) chains are further linked by UO(6) polyhedra, forming the 3D [(UO(2)) (Te(2)O(7))](2-) anionic frameworks. In Mg [(UO(2)) (TeO(3))(2)], TeO(4) disphenoids share common corners with each other resulting in infinite 1D chains of [(TeO(3))(2)](4-) propagating along the a-axis. These chains link the uranyl bipyramids by edge sharing along two edges of the disphenoids, resulting in the 2D layered structure of [(UO(2)) (Te(2)O(6))](2-). The structure of Sr [(UO(2)) (TeO(3))(2)] is based on 1D chains of [(UO(2)) (TeO(3))(2)](∞) (2−) propagating into the c-axis. These chains are formed by edge-sharing uranyl bipyramids which are additionally fused together by two TeO(4) disphenoids, which also share two edges. The 3D framework structure of Sr [(UO(2)) (TeO(5))] is composed of 1D [TeO(5)](4−) chains sharing edges with UO(7) bipyramids. Three tunnels based on 6-Membered rings (MRs) are propagating along [001] [010] and [100] directions. The HT/HP synthetic conditions for the preparation of single crystalline samples and their structural aspects are discussed in this work.