Phasenbeziehungen im System Se?Br und die Kristallstrukturen des dimorphen SeBr4

Phase Relations and Crystal Structures in the System Se? Br The system Se? Br contains two intermediate phases with congruent melting behaviour: α-SeBr (+5°C) and α-SeBr₄ (+123°C). β-SeBr and β-SeBr₄ are metastable with respect to the phase diagram and are irreversibly transformed to the α-modifications by annealing. Phase relations in the Se? Br system are discussed in detail. Single crystals of α- and β-SeBr₄ are obtained by vapour phase transport. β-SeBr₄ is monoclinic, space group C2/c, z = 16, a = 17.02, b = 10.39, c = 15.49 Å, β = 117°, and is an isotype of TeCl₄. α-SeBr₄ is trigonal, space group P31c, z = 16, with a = 10.200(7), c = 30.351(18) Å. In both modifications tetrameric cubane-like molecules [SeBr₄]₄ are present, but with different spatial arrangement. The crystal structure of α-SeBr₄ is discussed in terms of packing aspects.     

Definitionen für Fachbegriffe im Bereich der Diffusion im festen Zustand (IUPAC‐Empfehlungen 1999)

Die Übersetzung basiert auf den „Definitions of Terms for Diffusion in the Solid State“ der Commission on High Temperature Materials and Solid State Chemistry der International Union of Pure and Applied Chemistry, veröffentlicht in Pure Appl. Chem. 1999 , 71, 1307–1325. Das Original wurde von M. Kizilyalli (Middle East Technical University, Ankara, Türkei), J. Corish (Trinity College, University of Dublin, Irland) und R. Metselaar (Technische Universiteit Eindhoven, Niederlande) für die Veröffentlichung vorbereitet.     

Synthesis of Strontium Borophosphate,SrBPO5 by Solid State and Hydrothermal Methods and Characterisation

SrBPO₅ was synthesized by a solid‐state reaction reported and by a new solid state reaction using BPO4 as a phosphating agent. It was also obtained by a hydrothermal method. The structure of the compound was solved by Rietveld analysis before. The examination of X‐ray powder diffraction data showed that, SrBPO5 is isostructural with CaBPO₅ and BaBPO₅. It crystallizes in the trigonal system in P3₁21 and the refined unit cell parameters are a = 6.8488(1), c = 6.8159(2) Å, Z=3 and D_m 3.77 g/cm³.