Thermodynamics of Alloys: Solid Electrolyte Studies and Solution Calorimetry of Nickel-Gallium Alloys.
Final technical rept.,
BIRMINGHAM UNIV (ENGLAND) DEPT OF PHYSICAL METALLURGY AND SCIENCE OF MATERIALS
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Reversible galvanic cells with zirconia-calcia solid electrolytes and either Pt-O air or Ni-O reference electrodes were used to determine thermodynamic properties of solid Ni-Ga alloys at temperatures between 837 and 1100K. Activities, free energies, entropies and heats of formation were obtained for the Ni-rich fcc solid solutions and for the Ni3Ga, Ni2Ga, Ni3Ga2, NiGa and Ni2Ga3 phases. All the above properties are characterised by negative deviations from ideality. The exothermic heats of formation of alloys and their differences from similar Pd-based phases are discussed in relation to their electronic structures. An analysis of the entropies of formation into their probable configurational, electronic, magnetic and vibrational components is suggested. Thermodynamic evidence for substitutional and vacancy defect structures in NiGa was examined. Preliminary results of tin-solution calorimetric measurements of heats of formation of the solid alloys, the above phases and Ni3Ga7 at 300K are presented. Modified author abstract
- Properties of Metals and Alloys