DESORPTION CHARACTERISTICS OF RARE-EARTH (R) HYDRIDES (R=Y, CE, PR, ND, SM, GD AND TB) IN RELATION TO THE HDDR BEHAVIOR OF R-FE-BASED-COMPOUNDS

Vacuum desorption characteristics of binary hydrides of rare earth met als (R=Ce, Pr, Nd, Y, Sm, Gd, Tb) were studied. A complete decompositi on of hydrides, confirmed by X-ray diffraction, was achieved at temper atures up to 820 degrees C, When heating the hydrogenated material in vacuum, two distinct hydrogen desorption events were observed for all the hydrides under investigation. The hydrogen desorption behaviour is different for the two groups of metals, namely group I (Ce, Pr and Nd ) and group II (Y, Sm, Gd and Tb). The nation-disproportionation-desor ption-recombination (HDDR) process was shown to take place for the Nd6 Fe13Ge and Nd6Fe12.8Ga1.2 intermetallic compounds, both with the Nd6Fe 13Si-type structure. The hydrogen absorption and desorption properties of these compounds were studied in relation to the desorption charact eristics of neodymium hydride.