Experimental investigation and thermodynamic assessment of La–Y–Ni ternary system in Ni‐rich corner
Sheng-Xiang Wu, Li Wang, Huiping Yuan, Qun Luo, Qian Li, Kuo‐Chih Chou
Abstract
Abstract La–Y–Ni alloys exhibit high discharge capacity due to the formation of AB 3‐3.8 ‐type (A = La, Y; B = Ni) intermetallic compounds. However, the stable composition and temperature range for this type of phase are rarely reported, which restrains the development of La–Y–Ni hydrogen storage alloys with stable structure and high capacity. This paper focuses on the phase equilibria of the La–Y–Ni ternary system in Ni‐rich corner. The phase constitution, microstructure, and equilibrated composition were experimentally determined at 1273 and 1148 K using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS). The solubilities of La and Y in the binary compounds were measured. Two ternary compounds, 3R‐LaY 2 Ni 9 with the structure of PuNi 3 type and La 0.5 Y 0.5 Ni 5 with the structure of CaCu 5 type, existed at both temperatures. Based on the experimental data, the thermodynamic description of La–Y–Ni system was assessed by Calculation of Phase Diagram method. The calculated isothermal sections agree with the experimental data. The thermodynamic database is helpful for the design of La–Y–Ni hydrogen storage alloys.