Semiconductor-metal-semiconductor transitions in the superstoichiometric dihydride YH2.10.

Abstract

A metal-semiconductor transition has been observed in the range 230--260 K for the first time in a slightly superstoichiometric rare-earth dihydride, ${\mathrm{YH}}_{2.10}$ (as compared to the x-rich systems ${\mathrm{CeH}}_{2+\mathit{x}}$ and ${\mathrm{LaH}}_{2+\mathit{x}}$ with 0.7\ensuremath{\lesssim}x\ensuremath{\lesssim}0.9), implying an order-disorder transformation in the octahedral sublattice of the excess hydrogen atoms as the driving mechanism. Furthermore, a resistivity minimum in the range 60--80 K was observed, indicating for the first time in such systems an additional metal-semiconductor transition towards lower temperatures.