Sheding light on the negative thermal expansion behavior in light ions doped Zn2GeO4 nanocrystals: a combined perspective between XAS and XR

This proposal aims to investigate the anomalous behavior of the negative thermal expansion (NTE) in Zn2GeO4 compound and how it can be controlled by appropriated doping with light ions (Li or Mg). Materials which exhibit NTE are of great interest because of the possibility to create compounds with a tunable coefficient of thermal expansion in some specific temperature ranges. However, a full understanding and controlling of NTE mechanisms are still challenging since this behavior can be driven by different mechanisms, such as low-wavenumber phonons, spontaneous polarization, or charge transfer phenomena. Therefore, this study envisages the use of the XAS beamlines BM23/ID24-DCM station to shed light on the NTE at local level of Zn2GeO4 nanocrystals, being complemented by high-resolution X-ray diffraction data from HR-XRD beamline ID22. We expected to better understand the mechanisms of NTE in Zn2GeO4, which may enable a full controll of their intrinsic thermal expansion.