Quenching behaviour of H or D in the solid solutions with erbium, thulium and lutetium at low temperature

Abstract

The solid solutions alpha Er(H,D)_x, alpha Tm(H,D)_x and alpha Lu(H,D)_x exhibit-when quenched across the anomaly region near 200K-a resistivity increase, Delta rho _q, which behaves as a power function of the H concentration: Delta rho _q varies as c_H,D^s, the exponent s increasing from 0.3 to 0.7 when going from ErH_x to LuH_x. An extrapolation towards s=1 leads to a solubility limit in the low-temperature alpha phase of c_alpha ^max approximately 25%. The quenching behaviour in these systems is explained by the availability of tetrahedral sites in the HCP unit cell (one out of eight in the ideal case of maximum solubility) and by the attractive interaction between H atoms in the nearest-neighbour position along the c axis.