Low-temperature heat capacity of Sc-Zr and Sc-Mg alloys

Abstract

The low-temperature heat capacity of nineteen Sc-Zr alloys with compositions ranging from pure Sc to 34-at.% Zr in Sc and five Sc-Mg alloys with magnesium concentrations less than 8 at.% were measured from 1 to 20 K. Zirconium additions up to 0.5 at.% raises the electronic specific-heat constant ($\gamma$); then it decreases monotonically with further zirconium additions up to 34-at.% Zr. The effect of magnesium is to decrease the electronic specific-heat constant slowly. The heat-capacity results were used to calculate an experimental density of states (DOS) curve for scandium. The theoretical DOS curves are significantly different from the experimental DOS curve. The various enhancement factors have been calculated using these DOS curves. A change in slope in $\gamma$ at ∼ 2-at.% Mg and the peak in $\gamma$ at 0.5-at.% Zr are probably associated with the second energy band crossing the Fermi energy at the points $H$ and $L$ in the Brillouin zone as the electron concentration is lower or raised, respectively. The effect of dilute amounts of zirconium and magnesium on the Debye temperature (${\Theta }_D$) of scandium is unusual, initially rising for zirconium additions and falling for magnesium additions. At high solute concentrations ${\Theta }_D$ rises and falls more or less in a "saw-tooth"-like fashion. It is suggested that this variation in ${\Theta }_D$ is due to the formation of short-range-order configurations of Sc impurity atoms in the solid solution alloys.