New maximally disordered – High entropy intermetallic phases (MD-HEIP) of the Gd1-xLaxSn2-ySbyMz (M=Li, Na, Mg): Synthesis, structure and some properties

A new concept to prepare Maximally Disordered – High Entropy Intermetallic Phases (MD-HEIP) with the general formula of Gd1-xLaxSn2-ySbyMz (M = Li, Na, Mg) based on two mechanisms of substitution and insertion is proposed. As a result of the substitution of Gd by La and Sn by Sb in the binary GdSn2 compound, a maximally disordered (MD) phase of Gd1-xLaxSn2-ySby was formed. The formation of Gd1-xLaxSn2-ySbyLiz and Gd1-xLaxSn2-ySbyMgz HD-HEIP phases as the result of additionally inserting Li/Mg into tetragonal antiprismatic voids is observed during the electrochemical lithiation and magnesiation, respectively. The Gd1-xLaxSn2-ySbyNaz phase was formed by partial substitution of Sn atoms by Na atoms. The Gd1-xLaxSn2-ySby and Gd1-xLaxSn2-ySbyMz phases have been studied by XRD, SEM, EPMA, Sn Mössbauer spectroscopy, 7Li NMR, electrochemical techniques, magnetization and heat capacity measurements. The electrochemical studies of cyclic characteristics show that the MD-HEIP electrodes are rapidly activated (5–6 cycles) and continue to work steadily, almost without losing capacity. The MD phases of Gd1-xLaxSn2-ySby and Gd1-xLaxSn2-ySbyNaz show very similar behaviour of physical properties. Both MD phases of Gd1-xLaxSn2-ySby and Gd1-xLaxSn2-ySbyNaz have a comparably strong mean field antiferromagnetic coupling (θ around −41 K) and show typical Currie-Weiss paramagnetic behaviour of localized Gd magnetic moments down to ∼20 K. Both MD – HEIP Gd1-xLaxSn2-ySbyMz (M = Li and Mg) samples show a lowered antiferromagnetic mean field coupling (θ around −13 K) compared to MD phases.