Abstract
UH3 based hydrides with modified structure and composition can be prepared using high H2 pressures from precursors in the form of rapidly cooled uranium alloys. While the alloys with α-U structure lead to the β-UH3 type of hydrides, γ-U alloys (bcc) lead either to α-UH3 hydride type or nanocrystalline β-UH3.
The nanocrystalline β-UH3 structure, appearing for Mo alloying, can accommodate in addition numerous other d-metal components, as Ti, Zr, Fe, Nb. The pure Mo alloyed hydrides (UH3)1MINUS SIGN xMox exhibit increasing Curie temperature TC with maximum exceeding 200 K for x = 0.12-0.15.
Other components added reduce the TC increment with respect to pure UH3 (170 K). Also alloying by Zr gives a weaker enhancement.
Seen globally, the TC variations are rather modest, which reflects the prominence of interaction of U with H. It is suggested that important ingredient is a charge transfer, depopulating the U-6d and 7s states, while the 5f band stays at the Fermi level.