Aluminium compounds of the rare earths: Enthalpies of formation of Yb-Al and La-Al alloys

The standard molar enthalpies of formation for the different solid La-Al and Yb-Al alloys have been measured by means of direct calorimetry. The composition and equilibrium state of the Samples were checked by micrographic and X-ray diffraction techniques. The following values have been obtained (kJ (mol atoms)(-1)): LaAl, Delta(form)H degrees = - 46.0+/-2; LaAl, Delta(form)H degrees = - 50.5+/-2; LaAl3 Delta(form)H degrees = - 44.0+/-2; La3Al11 Delta(form)H degrees = - 41.0+/-2; Delta bAl(3) Delta(form)H degrees = - 39.5+/-2; YbAl3 Delta(form)H degrees = - 32.5+/-2. Experimental results are discussed and compared with literature data.