SMALL-ANGLE NEUTRON-SCATTERING STUDY OF METALLIC SODIUM ON PHASE-TRANSITION

In metallic sodium, a characteristic waiting time, which is the incuba tion time until phase transition starts, appears above M-s at a fixed temperature. Small-angle neutron scattering from clusters of the low-t emperature phase is observed, which shows good agreement with the aggr egation-of-spheres model, whose radius distribution is a Maxwell distr ibution function. Using the aggregation-of-spheres model, the average radius, r(0), of clusters of the low-temperature phase was found to be 57.2 Angstrom. Moreover, abnormal small-angle neutron scattering from local fluctuations is seen dining the waiting time, where this waitin g time is related to the nucleation process in the martensitic phase t ransition.