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| Hauptseite > Publikationsdatenbank > High-pressure crystal structures of Wadsley-type vanadium oxides V2O5 and V6O13 |
| Hauptseite > Publikationsdatenbank > High-pressure crystal structures of Wadsley-type vanadium oxides V2O5 and V6O13 |
| Abstract | FZJ-2022-01716 |
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2022
Please use a persistent id in citations: http://hdl.handle.net/2128/30843
Abstract: The so-called Wadsley phases with general formula VnO2n+1 form a homologous series ofcompounds [1,2]. They have arisen much interest due to the observed metal-insulatortransitions and their potential application as battery materials. The crystal structures of theparent compound V2O5 and of V6O13 (n=3) at ambient conditions are closely related, being builtup of edge and corner sharing building units, which can be described as [VO5]-pyramids in V2O5(space group Pmmn) and as [VO6]-octahedra in V6O13 (space group C2/m) [3,4].High pressure Raman and powder diffraction investigations on V2O5 suggest a pressureinducedphase transition between 4 and 7 GPa [5,6]. A recent in-situ high-pressure powderdiffraction study suggests an irreversible phase transition from α-V2O5 to an amorphous statearound 12.6 GPa while according to other investigations V2O5 becomes only fully amorphousunder 20.2 GPa [7]. Under high-temperature high-pressure conditions α-V2O5 converts into β-V2O5 (P21/m) [8]. Ex-situ high-pressure high-temperature synthesis in a multi anvil pressyielded δ-V2O5 (C2/c) which is isostructural to Sb2O59. Despite the high level of interest highpressure investigations using single crystal diffraction have not been performed, nor was theHP-HT phase diagram of V2O5 studied in situ up to know. In addition, despite the fact that the lowtemperature metal-insulator transition in V6O13 has been very well studied [10,11], highpressure investigations have not been performed so far on this compound.We have now studied single crystals of V2O5 and V6O13 as a function of pressure at PetraIII, Desy. The studies on V2O5 show complete irreversible amorphization of the sample above 7.3GPa and, moreover, anomalies are observed between 3 and 4 GPa. To further investigate the HPHTbehaviour of V2O5, we used the large volume press at ID06 at the ESRF and followed theevolution of the sample with in-situ synchrotron radiation. Heating of the amorphous phase leadto the formation of the δ-V2O5 polymorph with Sb2O5 structure, which can be recovered atambient conditions. High pressure single crystal diffraction experiments on V6O13 show ananomalous behaviour between 2 and 3 GPa, yet the ambient pressure polymorph seems to bestable up to the highest pressures reached in the experiment.
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