Multiparametric studies of chalcogenide phase change materials and mixed valent vanadium oxides


We investigate the relationship between crystal structure, electronic configuration and lattice dynamical properties using experimental techniques at synchrotron and neutron sources, as well as laboratory x-ray diffraction at extreme conditions.

Our investigations are focused on phase change materials (e.g. GeTexSe1-x, Sb2Te3-xSex) where we are particularly interested in crystal structures, bonding properties and lattice dynamics as a function of chemical composition and pressure.

The investigations are expanded towards the study of Mott systems (VxOy), which can be considered as a bridge between phase change and valence change materials. Here we aim at the characterizaiton of the pressure temperature phase diagrams, as well as the control of volume expansion through multiparametric studies and at the identification of oxygen diffusion pathways in mixed valence vanadium oxides.

The project is embedded in the SFB 917 (project A5) and realized in close cooperation with the group of Prof. R. Dronskowski at the Institute for Inorganic Chemistry where complementary theoretical calculations are carried out.


Prof. Dr. Karen Friese
Dr. Andrzej Grzechnik


M. G. Herrmann, R. P. Stoffel, I. Sergueev, H.-C. Wille, O. Leupold, M. Ait Haddouch, G. Sala, D. L. Abernathy, J. Voigt, R. P. Hermann, R. Dronskowski, K. Friese (2020). Lattice dynamics of Sb2Se3 from inelastic neutron and X-ray scattering; Physica Status Solidi B: Basic Solid State Physics 2020, 2000063 (7pp).

M. Küpers, R. P. Stoffel, B. Bong, M. G. Herrmann, Z. Li, A. Meledin, J. Mayer, K. Friese, R. Dronskowski (2020). Preferred selenium incorporation and unexpected interlayer bonding in the layered structure of Sb2Te3-xSex . Z. Naturforsch. B 2020, 75, 41-50.

I. Sergueev, K. Glazyrin, M. G. Herrmann, P. Alexeev, H.-C. Wille, O. Leupold, A. May, K. Friese, R. P. Hermann (2019). High pressure nuclear inelastic scattering with backscattering monochromatization. J. Synch. Radiation 26, 1592-1599.

M. G. Herrmann, R. P. Stoffel, M. Küpers, M. Ait Haddouch, A. Eich, K. Glazyrin, A. Grzechnik, R. Dronskowski, K. Friese (2019). New insights on the GeSexTe1-x phase diagram from theory and experiment. Acta Crystallogr. B75, 246-256.

M. G. Herrmann, R. P. Stoffel, R. Dronskowski, K. Friese (2018). The low-temperature heat capacity of the Sb2Te3-xSex solid solution from experiment and theory. J. Phys.: Condens. Matter 30, 405702 (10pp).

A. Grzechnik, Y. Ueda, T. Yamauchi, M. Hanfland, P. Hering, V. Potapkin, K. Friese (2016). Pressure-induced non-superconducting phase of β-Na0.33V2O5 and the mechanism of high-pressure phase transitions in β-Na0.33V2O5 and β-Li0.33V2O5 at room temperature. J. Phys.: Condens. Matter, 28, 035401.

A. Grzechnik, J. Yeon, H.-C. zur Loye, K. Friese (2016). High-pressure behaviour of Cs2V3O8 . J. Solid State Chem. 238, 252-258.

A. Grzechnik, Y. Ueda, T. Yamauchi, M. Hanfland, P. Hering, V. Potapkin, K. Friese (2015). Structural stability of the Wadsley-type bronzes b -Ag0.33V2O5 and b -Li0.33V2O5 on compression: a break-down of the two-leg ladder system in the non-superconducting high-pressure phase of b -Li0.33V2O5 . Phys. Rev. B 91, 174113.


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This project is funded as part of the SFB 917 "Nanoswitches" (project A5) of the Deutsche Forschungsgemeinschaft.

  SFB 917 Copyright: © SFB 917