Thermodynamics and Physical Properties of selected Heusler Alloys

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TECHNICAL SUMMARY:Heusler compounds of type X2YZ and half-Heusler compounds of type XYZ, where X and Y are transition metals and Z is a group III-V element, can exhibit interesting and useful properties, such as shape memory, thermoelectric, ferromagnetic and spin polarization effects. Unexplored compounds of these types could lead to new mechanical and electronic devices. The thermodynamic properties, crystal structures and phase equilibria of a large number of these compounds will be systematically determined. Drop calorimetry will be used to measure the standard heat of formation and heat capacity as a function of temperature. Phase equilibria and crystal structures will be determined using differential scanning calorimetry, energy dispersive X-ray analysis and X-ray diffraction. The thousands of possible compositions will be rapidly screened using systematic analyses of phase diagrams and first-principles calculations to identify specific systems for study. The thermodynamic data obtained will be incorporated into an on-line database for access by the scientific community. The data will be used to predict phase equilibria and to benchmark first principles calculations for these compounds. Students from high school through graduate school will be trained through these investigations.NON-TECHNICAL SUMMARY:The Heusler family of alloys holds promise for the next generation of sensors and actuators. This experimental study will produce thermodynamic data of fundamental importance to the exploration and future development of these promising materials. Properties to be measured include both thermodynamic and physical properties. Collaborations with scientists around the world will enable computational screening of thousands of potential compositions to determine those most appropriate for experiments and will enable the measurement of potentially useful physical properties. The data produced, which are expected to be critical to the field for future material development and benchmarking/validation of computational predictions, will be made available through a free on-line database. Education and training activities will include graduate students, undergraduate students and high-school students. Outreach will include the construction and dissemination of video tutorials on experimental techniques.