Thermochemistry of RPdAl (R = rare earth metal) intermetallics

The standard enthalpies of formation at 300 K of the RPdAl phases (R = Nd, Sm, Gd, Tb, Dy, Ho and Er) have been obtained by using a high-temperature direct reaction drop calorimeter. The reliability of the calorimetric results has been determined and supported by using different analytical techniques: light optical microscopy, scanning electron microscopy equipped with electron probe microanalysis (EPMA with EDS detector) and X-ray Powder Diffraction analysis. The high exothermal values observed for the RPdAl phases are discussed and compared with those available for the binary compounds of the R–Pd systems and for the ternary RNiAl phases.

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► A home-made high-temperature calorimeter has been employed.
► The ΔfH° at 300 K for the RPdAl phases have been obtained.
► A high exotermicity in the formation enthalpies of these phases has been found.