Mixing enthalpies of liquid Au–Yb alloys

Aurum and europium mixing enthalpies

“…The results of calorimetric measurements of the mixing enthalpy in the Au-Eu system are close to the data obtained for Au-Yb melts (ΔH min ≈ ≈ −51 kJ/mole) [2].…”

“…Comparing the mixing enthalpies in the Cu-REM, Ag-REM, and Au-REM systems shows that exothermicity of ΔH substantially increases in series Cu → Ag → Au. As noted previously [2], large negative values of ΔH in alloy formation in these systems are due to electron transfer from REM to Cu, Ag, Au as a result of the great difference in the electronegativity of components, especially for aurum alloys, which have very high electron affinity (2.8 eV [12]). The exothermal effect in alloy formation in the Au-Eu system seems to completely suppress the size misfit effect, which is opposite in sign and results from the great difference in molar volumes of liquid components ( 0 Au V =10.19 cm 3 /mole and 0 Eu V = = 28.96 cm 3 /mole) [13].…”

“…In this context, the abnormal magnetic properties exhibited by alloys of REMs with variable valency (Ce, Sm, Eu, Yb) with transition metals are usually associated with intermediate valency of REMs (+2 and +3 for Eu and Yb and about +3.4 for Ce) [7,11]. We noted this phenomenon earlier in analyzing the thermodynamic properties of Au-Yb [2] and Co-Ce [14] alloys.…”

“…The initial weight of metal in the crucible was about 3 g. To find the thermal equivalent k of calorimeter, we used pure metal components according to the procedure [2,3] and molybdenum (samples 0.02-0.04 g), which does not practically interact with the melt components between 1300 and 1500 K [2,3].…”

“…The experimental data on the mixing enthalpies ΔH in liquid alloys were obtained using the calorimetric method for only two systems: Au-Gd at 1650 K over a wide range of compositions [1] and Au-Yb at 1463 K at concentrations smaller than 50 at.% Yb [2]. The results demonstrate very large exothermal mixing effect and are substantially higher than the thermodynamic data for Cu-REM [3] and Ag-REM [4] melts examined earlier at the Institute for Problems of Materials Science (National Academy of Science of Ukraine).…”