CONSTRUCTION OF THE ISOTHERMAL CROSS-SECTION OF THE SYSTEM La–Li–Ni–Sn AT 400°C AND THE SOLUBILITY LIMIT OF THE PHASE

Abstract

Abstract

Investigation of multicomponent systems based on rare-earth and transition metals combined with Group IV p-elements is one of the key tasks in modern materials science. Intermetallic compounds forming in such systems possess unique physicochemical characteristics. Notably, doping these phases with Lithium holds significant promise for developing high-performance hydrogen storage materials and innovative anode materials for chemical power sources. As a continuation of the systematic study of multicomponent systems containing Lanthanum, Nickel, Lithium, and Group IVA elements (where the phase states of Silicon- and Germanium-rich regions of the La–Li–Ni–Si and La–Li–Ni–Ge systems were previously established), this work presents a comprehensive experimental investigation of the La–Li–Ni–Sn system. A series of experimental samples were prepared via arc melting of stoichiometric amounts of the starting elements, followed by thermal annealing at 400 °C for 480 hours. Phase qualitative analysis, diffraction pattern indexing, and unit cell crystallographic calculations were performed using LATCON, PowderCell 2.3, and WinCSD software. Full-profile crystal structure refinement via the Rietveld method was executed using the FullProf suite. The experimental monitoring of Lithium content was carried out using flame photometry, and the phase composition of the quaternary alloys was verified via energy-dispersive X-ray microprobe analysis. Two bounded substitutional solid solutions were identified for the first time along the isothermal section between the LaLiSn2 and LaNiSn2 compounds: LaLi1-xNixSn2 (x = 0–0.33; CeNiSi2 structure type, Pearson symbol oS16, space group Cmcm) and LaLixNi1-xSn2 (x = 0–0.20; CaLiSi2 structure type, Pearson symbol oP16, space group Pnma). The solubility limits of the components within these solid solutions were determined based on the unit cell volume behavior as a function of Lithium and Nickel concentration during their mutual substitution. No quaternary compounds of constant composition (stoichiometric phases) were detected within the investigated concentration range.