Chihiro Ohki1 Hirohisa Uchida2 and Ensei Ko3
1Graduate Student, Faculty of Engineering, Tokai University, Kanagawa
The phase equilibria of the PrH2-H and NdH2-H Systems were investigated by measurements of the pressure-concentration-temperature curves using Sieverts' type apparatus made of stainless steel. The measured P-C-T curves of these systems indicated plateaux in the H2 absorption and desorption processes. Large hysteresis phenomena were also observed in the measured curves. The appearance of the plateaux suggested the co-existence of their dihydride and trihydride phases in those regions. The crystal structures of PrH3 and NdH3 were also analyzed for the identification of the formation of trihydride phase for each system by using an X-ray diffraction measurement at room temperature in the air. The trihydride phases for Pr and Nd are having a h.c.p. structure. This result suggests that the present classification of the lanthanoide metal which does not form the LnH3 phase as the lighter and which does form the LnH3 phase as the heavier is having little significance.
lanthanoide, praseodymium, neodymium, trihydride phase, pressure-concentration-temperature measurement, crystal structure
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