Radiation-enhanced phase separation in amorphous Fe40Ni40P20

Specimens of amorphous Fe₄₀Ni₄₀P₂₀ exposed to neutron-irradiation and subsequently annealed at different temperatures are shown to undergo a similar phase separation into amorphous P-enriched and P-depleted regions as occurs in specimens annealed without prior irradiation. Whilst the radius (∼ 3.2 nm) of the P-rich regions is independent of whether the specimen has been irradiated or not, the onset of phase separation occurs for irradiated samples at lower temperatures; under identical annealing conditions the volume fraction of P-rich clusters is much larger in irradiated FeNiP than in un-irradiated material. The faster phase separation kinetics are a consequence of the irradiation-induced excess volume which allows for an increased mobility of individual atoms.