New insights into the local structure and disorder of W and other cations in tungstates high-entropy oxides

High-entropy oxides (HEOx) is a new class of materials with remarkable properties. The understanding and/or the optimization of their properties requires a good knowledge of the links between the chemical composition and the local structural disorder, which is still missing for most of them. As a pioneer and expert of the study of HEOx, we want to determine the local disorder around the cations (M) in the model MWO4 family (M = stoichiometric mixture of 5 elements) thanks to EXAFS at low-temperature, to relate the magnitude of this disorder to (i) their macroscopic thermal properties and the (ii) phonon behavior. On FAME-UHD, we will concentrate on two transition metals (M=Co, Ni) and the W6+ cation. Recording HERFD-XAS thanks the analyzer-crystals spectrometer of the beamline is mandatory to get (i) very well-resolved W spectra and (ii) an EXAFS signal with a k range long enough to get relevant structural information for Co and Ni.