Order-disorder (OD) structures of Rb₂Zn(TeO₃)(CO₃)·H₂O and Na₂Zn₂Te₄O₁₁

Abstract

Single crystals of the two alkali metal zinc oxidotellurates(IV), Rb2Zn(TeO3)(CO3)·H2O and Na2Zn2Te4O11, were obtained by reactions of mixtures of ZnO, TeO2, Rb2CO3 (molar ratios 2:3:6) and ZnO, TeO2, Na2CO3 (molar ratios 2:3:10), respectively, with small amounts of water as a mineralizer. Both compounds crystallize as order-disorder (OD) structures of layers and feature a high stacking fault probability. The crystal structure of Rb2Zn(TeO3)(CO3)·H2O is composed of layers extending parallel to (100). The structure is composed of two kinds of non-polar OD layers consisting of trigonal-pyramidal [TeO3]2−, tetrahedral [ZnO4]6−, Rb1+, and CO3 2−, H2O, Rb2+, respectively. Different centrings of the layer groups lead to an ambiguity in the stacking arrangement. The crystal structure of Na2Zn2Te4O11 is built from layers extending parallel to (001). Trigonal-pyramidal [TeO3]2− and bisphenoidal [TeO4]4− polyhedra form [Te4O11]6− groups, which are connected by longer Te–O-contacts to form 1 ∞[Te8O22]12− double chains oriented along either [100] or [010]. These chains form non-polar layers, which appear alternatingly in two orientations related by a fourfold rotoinversion. The Zn2+ and Na+ cations are located at the layer interface. The stacking ambiguity is due to different lattices of adjacent layers.

Symmetry Analysis of the Complex Polytypism of Layered Rare-Earth Tellurites and Related Selenites: The Case of Introducing Transition Metals

“…This approach allows to determine the symmetry relations for the whole family of known polytypes and predict the hypothetical ones [27], which is important for the searching of new materials [28][29][30][31][32][33][34]. The OD structures with the different polytypes have been also described for the tellurium compounds, in particular, for the hydrous magnesium orthotellurate (VI) Mg [37].…”