The recent finding that “NiSn” is composed of Ni3Sn2 with additions of Ni3Sn4 and a Sn(II) compound, SnO or Sn(OH)2, permits to develop a refined model of its structure and stability. The mean grain diameter was determined by STM (15 nm) with a rather small variance. Electrode potentials could be measured in a fused salt mixture of SnCl2 and KC1 between 240 and 300°C. Their evolution with time was consistently interpreted by assuming a solid state separation of Ni3Sn4 from the Ni‐deficient metastable phase Ni3‐δSn2. This model is in good agreement with earlier results of excess enthalpies and XRD changes measured during the recrystallization process.

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