Kinetics of ordering in Ni1.50Sn ('Ni3Sn2') as revealed by the variation of the lattice parameters upon annealing
Résumé
X-ray powder diffraction was employed to reveal the structural changes occurring upon annealing of quenched, hexagonal Ni1.50Sn below its equilibrium ordering temperature, leading finally to long-range ordered, orthorhombic Ni1.50Sn. The changes in the diffraction patterns indicate that the features of the low-temperature phase develop gradually in two main stages. Ex-situ and in-situ time-resolved X-ray powder diffraction analysis of the first stage was employed to monitor at various temperatures in particular the time dependence of the lattice axial ratio c/a associated with the formation of long-range order in small domains. Data evaluation using an 'equivalence-time' method gave a value of 165-170 kJ/mol for the activation energy of the ordering, indicative of lattice-site changes of Ni atoms.
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