New composite based on Tb<sub>2-x</sub>Y<sub>x</sub>Ni<sub>7-y</sub>Mg<sub>y</sub> and Tb<sub>1-x</sub>Y<sub>x</sub>Ni<sub>5-y</sub>Mg<sub>y</sub> phases with hydrogen sorption properties
Systematic studies of the R2Ni7-xMx solid solutions often showed the presence of two polymorphs in alloys. Both these phases mainly dissolve Mg or some p-elements approximately in equal quantities. The room-temperature modification α-Tb2Ni7 crystallizes in the hexagonal Ce2Ni7-type; the high-temperature phase β-Tb2Ni7 belongs to the rhombohedral Gd2Ni7-type. The hydrogen sorption properties are inherent to these phases.