Three different Ge environments in a new Sr 5 CuGe 9 O 24 phase synthesized at high pressure and high temperature
Résumé
In the framework of expanding the range of copper-based compounds in the pyroxene family we have synthesized at high pressure and high temperature a powder containing a mixture of a new phase with stoichiometry Sr5CuGe9O24 with two identified impurity phases. Electron crystallography showed that the new phase crystallizes with a monoclinic structure with cell parameters a = 11.6 Å, b = 8.1 Å, c = 10.4 Å and β = 101° and space group P2/c. We applied the recently developed low-dose electron diffraction tomography method to solve the structure by direct methods. The obtained structure model contains all 9 independent cation positions and all 13 oxygen positions. A subsequent refinement against X-ray powder diffraction data ascertained the high quality of the structure solution, in particular the unusual structural arrangement that there are three different environments for Ge in this phase. Synopsis The high-pressure high-temperature phase Sr5CuGe9O24 was solved by low-dose electron diffraction tomography and refined against X-ray powder diffraction data. The Ge ions in this compound have three different coordination numbers.
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