A novel high entropy spinel-type aluminate MAl2O4 (M = Zn, Mg, Cu, Co) and its lithiated oxyfluoride and oxychloride derivatives prepared by one-step mechanosynthesis

For the first time, a spinel-type high entropy oxide (Zn0.25Cu0.25Mg0.25Co0.25)Al2O4 as well as its derivative lithiated high entropy oxyfluoride Li0.5(Zn0.25Cu0.25Mg0.25Co0.25)0.5Al2O3.5F0.5 and oxychloride Li0.5(Zn0.25Cu0.25Mg0.25Co0.25)0.5Al2O3.5Cl0.5 are prepared in the nanostructured state via high-energy co-milling of the simple oxide precursors and the halides (LiF or LiCl) as sources of lithium, fluorine and chlorine. Their nanostructure is investigated by XRD, HR-TEM, EDX and XPS spectroscopy. It is revealed that incorporation of lithium into the structure of spinel oxide together with the anionic substitution has significant effect on its short-range order, size and morphology of crystallites as well as on its oxidation/reduction processes. The charge capacity of the as-prepared nanomaterials tested by cyclic voltammetry is found to be rather poor despite lithiation of the samples in comparison to previously reported spinel-type high entropy oxides. Nevertheless, the present work offers the alternative one-step mechanochemical route to novel classes of high entropy oxides as well as to lithiated oxyfluorides and oxychlorides with the possibility to vary their cationic and anionic elemental composition.

Application of Mechanical Activation in Synthesizing Multiferroic Pb(Fe1/2Nb1/2)O3 Powders

Application of Mechanical Activation in Synthesizing Multiferroic Pb(Fe1/2Nb1/2)O3 Powders In the study, the method of high-energy powder milling - mechanical activation (MA) was used for synthesizing Pb(Fe1/2Nb1/2)O3 (PFN) powders. For the purpose of comparing the influence of high-energy milling on PFN synthesis, two groups of powder samples were used. The first mixture consisting of simple oxide powders; the second one consisting of compound oxide powders. The obtained powders were subjected to structural analysis with the use of XRD and Mőssbauer spectroscopy. Tests revealed that during the process of high-energy milling of initial constituents a partial synthesis of PFN material phases occurs. By comparing the two methods of PFN synthesizing it may be stated that mechanical activation in the case of a simple oxide mixture (PFN1) is equally effective as for a compound oxide mixture (PFN2).