The crystal structure of a new CdTe₂O₅ polymorph, isotypic with ∊-CaTe₂O₅.

ABSTRACT: Single crystals of cadmium penta-oxidoditellurate(IV), CdTe₂O₅, were obtained as by-products in a hydro-thermal reaction of Cd(NO₃)₂·4H₂O, TeO₂, H₆TeO₆ and NH₃ (molar ratios 2:1:1:6) at 483 K for seven days. The crystals represent a different polymorph (henceforth referred to as the β-form) than the α-CdTe₂O₅ crystals grown from the melt, and are isotypic with hydro-thermally grown ∊-CaTe₂O₅. The asymmetric unit of β-CdTe₂O₅ comprises one Cd, two Te and five O sites, all of which are located in general positions (Wyckoff position 4 e). The cadmium(II) atom is coordinated by seven oxygen atoms, forming ² _∞[CdO_6/2O_1/1] (100) layers. Both tellurium sites are surrounded by four oxygen atoms with one of them being at a significantly longer distance than the other three. The resulting bis-phenoidal [TeO₄] units also form layers propagating parallel to (100) by sharing edges with each other. The stereochemically active 5s ² lone pair of the Te^IV atoms leads to the formation of large channels extending along [011] and smaller ones along [010]. A qu-anti-tative comparison between the crystal structures of β-CdTe₂O₅ and ∊-CaTe₂O₅ is made.

SUBMITTER: Eder F 

PROVIDER: S-EPMC7273983 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature