Enthalpies of formation of selected Pd2YZ Heusler compounds

Standard enthalpies of formation of selected ternary Pd-based Heusler type compositions Pd2YZ (Y = Cu, Hf, Mn, Ti, Zr; Z = Al, Ga, In, Ge, Sn) were measured using high temperature direct synthesis calorimetry. The measured enthalpies of formation (in kJ/mole of atoms) of the Heusler compounds are, Pd2HfAl (−81.6 ± 2.4); Pd2HfGa (−79.9 ± 2.9); Pd2HfIn (−76.4 ± 1.4); Pd2HfSn (−77.6 ± 1.6); Pd2MnSn (−54.6 ± 3.1); Pd2TiGa (−65.6 ± 3.6); Pd2TiIn (−69.9 ± 2.1); Pd2TiSn (−78.6 ± 2.4); Pd2ZrAl (−85.3 ± 3.0); Pd2ZrGa (−76.2 ± 1.9); Pd2ZrIn (−85.1 ± 3.9); Pd2ZrSn (−92.2 ± 3.1); for the B2 compounds, Pd2MnAl (−87.1 ± 3.0); Pd2MnGa (−54.5 ± 1.7); Pd2MnIn (−41.0 ± 2.5); Pd2TiAl (−81.4 ± 1.9); for the tetragonal compound Pd2CuAl (−55.2 ± 3.0) and for the orthorhombic compound Pd2CuSn (−43.1 ± 2.3). Values were compared with those from published first principles calculation and the Open Quantum Materials Database (OQMD). Lattice parameters of these compounds were determined by X-ray diffraction analysis (XRD). Microstructures were identified using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Selected alloys were annealed at various temperatures to investigate phase transformations and phase relationships.