Enthalpies of formation of selected Co2YZ Heusler compounds

• Published in: Journal of alloys and compounds 2013-11, Vol.577, p.49-56
• Main Authors: Yin, Ming, Chen, Song, Nash, Philip
• Format: Article
• Language: English
• Subjects: Alloys; Aluminum; Atomic properties; Calorimetry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron states; Enthalpy; Enthalpy of formation; Exact sciences and technology; Gallium base alloys; Hafnium; Heusler compound; Methods of electronic structure calculations; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Thermal properties of condensed matter; Thermal properties of crystalline solids; Thermodynamic properties; Titanium
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.04.136

•Enthalpies of formation of selected Co2YZ were measured by drop calorimeters.•Enthalpy decreases as the Z element approaches the top right corner of the periodic table.•For the Y element, enthalpy increases on increasing the number of d electrons.•Result of L21 structured compounds agrees with first principles data.•Lattice parameters and related phase relationships were consistent with literature data. Standard enthalpies of formation at 298K of selected ternary Co2-based Heusler compounds Co2YZ (Y=Fe, Hf, Mn, Ti, V, Zr; Z=Al, Ga, In, Si, Ge, Sn) were measured by high temperature direct synthesis calorimetry. The measured enthalpies of formation (in kJ/mole of atoms) of the L21 compounds are: Co2FeGa (−25.8±2.6); Co2FeSi (−38.4±2.2); Co2FeGe (−11.6±2.1); Co2MnGa (−30.1±2.3); Co2MnSi (−42.4±1.2); Co2MnGe (−31.6±3.0); Co2MnSn (−15.6±2.8); Co2TiAl (−55.0±3.7); Co2TiGa (−54.2±2.6); Co2TiSi (−61.4±1.7); Co2TiGe (−59.3±3.8); Co2TiSn (−38.4±2.0); Co2VGa (−28.4±1.1) and for the B2 compounds: Co2FeAl (−22.5±2.5), Co2MnAl (−27.6±2.7). Values are compared with those from first principles calculation when available and the extended semi-empirical model of Miedema. Trends in enthalpy of formation with element atomic number are discussed. Lattice parameters of the compounds with L21 structure are determined by X-ray diffraction analysis.