A new eight-cation inverse high entropy spinel with large configurational entropy in both tetrahedral and octahedral sites: Synthesis and cation distribution by X-ray absorption spectroscopy

In this work we report the synthesis of (Co,Mg,Mn,Ni,Zn)(Al,Co,Cr,Fe,Mn)2O4 in a single-phase spinel structure (space group Fd3¯m). The chemical homogeneity and purity of the sample were checked through X-ray diffraction, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The analysis of the pre-edge peaks of the X-ray absorption spectra for all the transition metals clearly indicated the presence of a partial degree of inversion in the spinel structure. This material is characterized by a particularly large configurational entropy, regarding both the A and the B sites, leading to a total value equal to 3.3 in R unit.